Additive Manufacturing

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	18.4 Days	CHF 2400
Applied Mechanics applmech	-	2.3	2020	23.1 Days	CHF 1200
Processes processes	2.8	5.1	2013	14.9 Days	CHF 2400
Metals metals	2.6	4.9	2011	17.8 Days	CHF 2600
Journal of Manufacturing and Materials Processing jmmp	3.3	5.1	2017	16.5 Days	CHF 1800

14 pages, 710 KiB

Open AccessReview

An Outline of Fused Deposition Modeling: System Models and Control Strategies

by Michele Martini, Massimiliano Scaccia, Gabriele Marchello, Haider Abidi, Mariapaola D’Imperio and Ferdinando Cannella

Appl. Sci. 2022, 12(11), 5400; https://doi.org/10.3390/app12115400 - 26 May 2022

Cited by 8 | Viewed by 3426

Abstract

Fused Deposition Modeling (FDM) is a type of Additive Manufacturing (AM) technology that is becoming increasingly common in numerous applications thanks to its versatility and reduced material waste. However, the complex physical phenomena occurring during extrusion, including the dynamics of non-Newtonian fluids, viscoelastic [...] Read more.

Fused Deposition Modeling (FDM) is a type of Additive Manufacturing (AM) technology that is becoming increasingly common in numerous applications thanks to its versatility and reduced material waste. However, the complex physical phenomena occurring during extrusion, including the dynamics of non-Newtonian fluids, viscoelastic behaviors and rheology, make the use of heuristic observations preferable to that of analytical approaches. Consequently, engineers have focused on optimizing materials and hardware rather than control algorithms. The limited knowledge about extrusion and deposition dynamics usually confines the control action to the motion of the printing head while keeping a constant flow rate. Existing attempts to synchronize motion and extrusion consists of open loop compensations, which, however, require identified transfer functions or need to be tuned manually. This article aims to compactly review FDM technologies from a control perspective by presenting (i) the models of extrusion and deposition and (ii) the control strategies currently adopted in industry. Full article

(This article belongs to the Topic Additive Manufacturing)

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12 pages, 23378 KiB

Open AccessArticle

Bionic Design of the Vertical Bracket of Wide Angle Auroral Imager by Additive Manufacturing

by Hang Li, Ruiyao Liu, Shuai He, Renlong Xin, Haijun Wang, Zhenglei Yu and Zhenbang Xu

Appl. Sci. 2022, 12(10), 5274; https://doi.org/10.3390/app12105274 - 23 May 2022

Cited by 5 | Viewed by 2407

Abstract

In the aerospace field, lightweight design is a never-ending pursuit. By integrating structural bionics and structural optimization, the vertical bracket of a wide angle auroral imager is designed and manufactured by additive manufacturing technology in this work. Initially, the classical topology optimization is [...] Read more.

In the aerospace field, lightweight design is a never-ending pursuit. By integrating structural bionics and structural optimization, the vertical bracket of a wide angle auroral imager is designed and manufactured by additive manufacturing technology in this work. Initially, the classical topology optimization is utilized for the vertical bracket to find the optimal material layout and primary load carrying paths. Drawing on the width-to-diameter ratio and the bone mineral density distribution of human femur, the vertical support is designed as a bionic structure with a solid middle section and thin wall in other parts. Afterwards, size optimization is maintained for the bionic design model to obtain the optimal model. The simulation results show that the three-way eigenfrequencies of bionic optimized structure are 320 Hz, 303 Hz, and 765 Hz, respectively, which are closely approximate to the original structure. However, the mass of bionic optimized structure is reduced by 23%. Benefiting from Selective laser melting, the complex optimized design can be rapidly manufactured. The three-way eigenfrequencies of the optimized structure measured by the 0.2 g sweep tests are 307 Hz, 292 Hz, and 736 Hz, respectively. The vibration test of bionic optimized structure verifies the accuracy of the simulation results. This study indicates that the combination of structural bionics and structural optimization provides a powerful tool kit to the design of similar support structure for space applications. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 2870 KiB

Open AccessArticle

Truncated Newton Kernel Ridge Regression for Prediction of Porosity in Additive Manufactured SS316L

by Hind Abdulla, Maher Maalouf, Imad Barsoum and Heungjo An

Appl. Sci. 2022, 12(9), 4252; https://doi.org/10.3390/app12094252 - 22 Apr 2022

Cited by 13 | Viewed by 2386

Abstract

Despite the many benefits of additive manufacturing, the final quality of the fabricated parts remains a barrier to the wide adoption of this technique in industry. Predicting the quality of parts using advanced machine learning techniques may improve the repeatability of results and [...] Read more.

Despite the many benefits of additive manufacturing, the final quality of the fabricated parts remains a barrier to the wide adoption of this technique in industry. Predicting the quality of parts using advanced machine learning techniques may improve the repeatability of results and make additive manufacturing accessible to different fields. This study aims to integrate data extracted from various sources and use them to obtain accurate predictions of relative density with respect to the governing process parameters. Process parameters such as laser power, scan speed, hatch distance, and layer thickness are used to predict the relative density of 316L stainless steel specimens fabricated by selective laser melting. An extensive dataset is created by systematically combining experimental results from prior studies with the results of the current work. Analysis of the collected dataset shows that the laser power and scan speed significantly impact the relative density. This study compares ridge regression, kernel ridge regression, and support vector regression using the data collected for SS316L. Computational results indicate that kernel ridge regression performs better than both ridge regression and support vector regression based on the coefficient of determination and mean square error. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 6547 KiB

Open AccessFeature PaperArticle

Normalizing Effect of Heat Treatment Processing on 17-4 PH Stainless Steel Manufactured by Powder Bed Fusion

by Si-Mo Yeon, Jongcheon Yoon, Tae Bum Kim, Seung Ho Lee, Tea-Sung Jun, Yong Son and Kyunsuk Choi

Metals 2022, 12(5), 704; https://doi.org/10.3390/met12050704 - 20 Apr 2022

Cited by 22 | Viewed by 5495

Abstract

Laser powder bed fusion (L-PBF)-processed 17-4 PH stainless steel (SS) generally exhibits a non-equilibrium microstructure consisting mostly of columnar δ-ferrite grains and a substantial fraction of retained austenite and martensite, contrary to 17-4 PH SS wrought with a fully martensite structure and coarse [...] Read more.

Laser powder bed fusion (L-PBF)-processed 17-4 PH stainless steel (SS) generally exhibits a non-equilibrium microstructure consisting mostly of columnar δ-ferrite grains and a substantial fraction of retained austenite and martensite, contrary to 17-4 PH SS wrought with a fully martensite structure and coarse grains. Despite the different microstructures of L-PBF and wrought 17-4 PH SS, post-processing is typically performed using the conventional heat treatment method. The insufficient effect of the heat treatment on the L-PBF product produces a δ-ferrite phase in the microstructure. To obtain improved mechanical properties, the addition of a normalizing treatment to the conventional heat treatment after L-PBF in a nitrogen gas environment was investigated. The fully martensitic matrix developed by adding the normalizing treatment contained homogeneous Cu precipitates and exhibited a similar or improved strength and elongation to failure compared to the wrought SS. Full article

(This article belongs to the Topic Additive Manufacturing)

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22 pages, 18295 KiB

Open AccessArticle

Jointing Principles in AMC—Part 1: Design and Preparation of Dry Joints

by Jan-Paul Lanwer, Hendrik Weigel, Abtin Baghdadi, Martin Empelmann and Harald Kloft

Appl. Sci. 2022, 12(9), 4138; https://doi.org/10.3390/app12094138 - 20 Apr 2022

Cited by 4 | Viewed by 2740

Abstract

The study described in this contribution contains a fundamental strategy to select geometries for dry joint profiles in 3D-printed concrete constructions. A database, here called the ‘joint catalogue’, contains a variety of joint types adapted from timber, steel, and bionic connections. Weighting factors [...] Read more.

The study described in this contribution contains a fundamental strategy to select geometries for dry joint profiles in 3D-printed concrete constructions. A database, here called the ‘joint catalogue’, contains a variety of joint types adapted from timber, steel, and bionic connections. Weighting factors and different criteria evaluate and score the various joint profiles (e.g., manufacturability, duration of manufacturing, and mechanical behaviour). Therefore, an algorithm sums up the scores leading to the preselection of better suitable profiles. The preselected joint profiles were afterwards analysed by the finite element method, determining the load capacity of the joint in a unit specimen. According to the joint catalogue, a smooth, triangular, truncated cone and arc joint profile appeared to be the optimal combination for dry joints in additive manufacturing of construction (AMC). Full article

(This article belongs to the Topic Additive Manufacturing)

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22 pages, 169278 KiB

Open AccessArticle

Effect of Vacuum Heat Treatment on the Microstructure of a Laser Powder-Bed Fusion-Fabricated NiTa Alloy

by Cheng-Tse Wu, Markus Bussmann and Kinnor Chattopadhyay

Metals 2022, 12(5), 700; https://doi.org/10.3390/met12050700 - 19 Apr 2022

Viewed by 2284

Abstract

The semiconductor industry uses a physical vapor-deposition process, with a nickel-tantalum (NiTa) alloy-sputtering target, to apply an amorphous NiTa thin film layer between the magnetic soft underlayer and substrate of a heat-assisted magnetic-recording hard disk drive. Currently, the alloy-sputtering target is produced through [...] Read more.

The semiconductor industry uses a physical vapor-deposition process, with a nickel-tantalum (NiTa) alloy-sputtering target, to apply an amorphous NiTa thin film layer between the magnetic soft underlayer and substrate of a heat-assisted magnetic-recording hard disk drive. Currently, the alloy-sputtering target is produced through a hot-pressing (HP) process followed by a hot isostatic pressing (HIP). In this study, we demonstrate a better process for producing the sputtering targets, using laser powder-bed fusion (L-PBF) followed by vacuum heat treatment (VHT), to produce alloy targets with superior microstructural characteristics that will produce better-quality thin films. We compare as-fabricated (just L-PBF) specimens with specimens produced by L-PBF and then annealed at different conditions. Where the as-fabricated specimens are characterized by columnar dendrites, annealing at 1275 °C for 4 h produces a uniform equiaxed grain microstructure and a uniformly dispersed fcc Ta precipitate. In addition, the average microhardness value is reduced from 725 ± 40 to 594 ± 26 HV0.2 and the maximum compressive residual stress is reduced from 180 ± 50 MPa to 20 ± 10 MPa as the result of dislocation elimination during the recovery and recrystallization process. Finally, due to microstructure recrystallization, the VHT-treated L-PBF NiTa specimens exhibit a smaller grain size (2.1 ± 0.2 µm) than the traditional HIP-treated HP specimens (6.0 ± 0.6 µm). Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 1447 KiB

Open AccessArticle

Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals

by Angelina Marko, Stefan Bähring, Julius Raute, Max Biegler and Michael Rethmeier

Appl. Sci. 2022, 12(8), 3955; https://doi.org/10.3390/app12083955 - 14 Apr 2022

Cited by 7 | Viewed by 2709

Abstract

The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality [...] Read more.

The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries. Full article

(This article belongs to the Topic Additive Manufacturing)

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16 pages, 8301 KiB

Open AccessArticle

Laser Powder Bed Fusion of K418 Superalloy: Process, Microstructure, Texture Feature, and Mechanical Property

by Zhen Chen, Pei Wei, Hanfeng Chen, Xinggang Chen, Yi Ruan, Wenzheng Zhou and Sujun Lu

Metals 2022, 12(4), 611; https://doi.org/10.3390/met12040611 - 1 Apr 2022

Cited by 6 | Viewed by 3056

Abstract

Laser Powder Bed Fusion (LPBF) is one of the most promising additive manufacturing (AM) technologies using metal powders. It has been increasingly applied in variety of industrial and engineering fields, including but not limited to aviation, aerospace, nuclear energy, automobiles, medical, molding, shipping, [...] Read more.

Laser Powder Bed Fusion (LPBF) is one of the most promising additive manufacturing (AM) technologies using metal powders. It has been increasingly applied in variety of industrial and engineering fields, including but not limited to aviation, aerospace, nuclear energy, automobiles, medical, molding, shipping, and so on. In this work, the influence of laser process parameters on the microstructure, textural features, and their resulting effect on the macroscopic mechanical properties of LPBF-manufactured K418 samples was investigated experimentally. OM, SEM, and X-ray diffraction were used to characterize the microstructure evolution, and EBSD was used to identify the crystal texture of the as-built K418 samples. The effect relationship between process, microstructure, and properties was investigated using mechanical property testing. Furthermore, the volumetric energy density VED was considered as a comprehensive evaluation index to reflect the effects of the main laser process parameters on the microstructure and mechanical behavior of LPBF-manufactured K418 samples, including scanning speed v, laser power P, layer thickness t, and hatch space H. The results show that as the volumetric energy density VED increases, the microstructure morphology of the LPBF-manufactured K418 sample evolves: clustered columnar grains → coarsened columnar grains → ultrafine columnar grains, and the mechanical properties of the LPBF-manufactured K418 sample improve, owing to the ultrafine elongated columnar grains and a strong {001} <100> cubic texture. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 3182 KiB

Open AccessReview

Photopolymerization of Ceramic Resins by Stereolithography Process: A Review

by Alessandro Bove, Flaviana Calignano, Manuela Galati and Luca Iuliano

Appl. Sci. 2022, 12(7), 3591; https://doi.org/10.3390/app12073591 - 1 Apr 2022

Cited by 59 | Viewed by 7864

Abstract

Stereolithography is known as one of the best Additive Manufacturing technologies in terms of geometrical and dimensional precision for polymeric materials. In recent years, a lot of studies have shown that the creation of ceramic resins, through a particular combination of monomeric components [...] Read more.

Stereolithography is known as one of the best Additive Manufacturing technologies in terms of geometrical and dimensional precision for polymeric materials. In recent years, a lot of studies have shown that the creation of ceramic resins, through a particular combination of monomeric components and ceramic powders, allows to obtain complex shape geometries thanks to the photopolymerization process. This review highlights the characteristics and properties of ceramic resins, peculiarities of the ceramic stereolithography processes, up to the relationship between the composition of the ceramic resin and the complexity of the post-processing phases. The comparison of different studies allows outlining the most common steps for the production of ceramic resins, as well as the physical and chemical compatibility of the different compounds that must be studied for the good feasibility of the process. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 9521 KiB

Open AccessArticle

Mechanical Analysis of Parameter Variations in Large-Scale Extrusion Additive Manufacturing of Thermoplastic Composites

by Nevine Tagscherer, André Marcel Bär, Swen Zaremba and Klaus Drechsler

J. Manuf. Mater. Process. 2022, 6(2), 36; https://doi.org/10.3390/jmmp6020036 - 16 Mar 2022

Cited by 12 | Viewed by 3579

Abstract

Large structural parts manufactured by Extrusion Additive Manufacturing (EAM) are limited by strong anisotropy due to insufficient bond formation and reduced molecular entanglement along the layer interface. To understand the correlation between process and material parameters and to enable digital modeling of EAM, [...] Read more.

Large structural parts manufactured by Extrusion Additive Manufacturing (EAM) are limited by strong anisotropy due to insufficient bond formation and reduced molecular entanglement along the layer interface. To understand the correlation between process and material parameters and to enable digital modeling of EAM, the effect of different substrate temperatures and layer heights on tensile strength was investigated. A simple testing methodology for pelletized carbon fiber-filled polyamide 6 was developed. Tensile tests were performed in a full factorial Design of Experiments (DoE) to determine the tensile properties. For bulk simulation, the nominal strength and modulus were also determined based on contact width obtained by optical microscopy. The results demonstrated high anisotropy, with the maximum transverse tensile strength reaching only 27% of the corresponding longitudinal results and the transverse tensile modulus reaching only 20% of its longitudinal value. The effects of varying layer height were less significant than varying substrate temperature. The results support the hypothesis that sufficient transverse tensile strength is achieved between the extrapolated crystallization onset and melt temperature. The methodology of this study can be used as a benchmark method to qualify new thermoplastic polymers for EAM processes and to determine optimal process parameters for improved fusion bonding. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 25807 KiB

Open AccessArticle

Targeted Temperature Manipulation and Analysis of the Influence on Mechanical Properties in Large-Scale Extrusion Additive Manufacturing

by Nevine Tagscherer, Tim A. Osswald and Klaus Drechsler

Appl. Sci. 2022, 12(6), 2998; https://doi.org/10.3390/app12062998 - 15 Mar 2022

Cited by 3 | Viewed by 2126

Abstract

Layer times in large-scale Extrusion Additive Manufacturing (EAM) of carbon fiber-reinforced thermoplastics are often outside the recommended process window. Brief layer times of tall parts with short path lengths lead to high temperatures and thus to melting of the component. In contrast, the [...] Read more.

Layer times in large-scale Extrusion Additive Manufacturing (EAM) of carbon fiber-reinforced thermoplastics are often outside the recommended process window. Brief layer times of tall parts with short path lengths lead to high temperatures and thus to melting of the component. In contrast, the substrate temperature decreases too far at longer layer times to achieve sufficient fusion bonding through molecular diffusion across the interface. Heating by infrared emitters and cooling by compressed air were experimentally tested and evaluated as methods for temperature control. Assuming that bond formation is mainly temperature-controlled, mechanical properties were expected to be similar to those of non-manipulated samples at the same temperatures. Samples of short carbon fiber-filled polyamide 6 in pellet form were manufactured in three test series. Infrared heating resulted in comparable tensile properties to samples at the target temperature and in a significant increase compared to the base temperature without heating. Cooling proved to be more effective when closer to the deposition nozzle, with tensile results even exceeding the expected values at temperatures below 170 °C. Overall, the results support the potential for targeted temperature control in EAM and the hypothesis that comparable bond strength can be achieved in dependence of the final substrate temperature. Full article

(This article belongs to the Topic Additive Manufacturing)

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16 pages, 15450 KiB

Open AccessArticle

Numerical Studies of the Effects of the Substrate Structure on the Residual Stress in Laser Directed Energy Additive Manufacturing of Thin-Walled Products

by Hang Jing, Peng Ge, Zhao Zhang, Jun-Qi Chen, Zhong-Ming Liu and Wei-Wei Liu

Metals 2022, 12(3), 462; https://doi.org/10.3390/met12030462 - 9 Mar 2022

Cited by 11 | Viewed by 2709

Abstract

A new method of controlling the residual stress in laser directed energy deposition additive manufacturing (DED AM) products proposed based on constraints used in manufacturing and the substrate design. The simulation results of the residual stress, which were validated with the experimental measured [...] Read more.

A new method of controlling the residual stress in laser directed energy deposition additive manufacturing (DED AM) products proposed based on constraints used in manufacturing and the substrate design. The simulation results of the residual stress, which were validated with the experimental measured data, showed that weaker constraints on the substrate could greatly decrease the residual stress in the laser DED AM products. In addition, by designing local reduced thickness regions into the substrate, such as long strip holes or support legs, the residual stress in DED AM products could be further decreased. In this study, when long strip holes were designed in the substrate, the tensile residual stress was decreased by 28%. An even smaller amount of residual stress was achieved when the design structure was changed to support legs. The tensile residual stress decreased by more than 30%. The fewer support legs, the smaller the residual stress. The residual stress in DED AM products could be well-controlled by design, while the stiffness can be weakened with fewer constraints. Full article

(This article belongs to the Topic Additive Manufacturing)

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21 pages, 12669 KiB

Open AccessArticle

Automation of Property Acquisition of Single Track Depositions Manufactured through Direct Energy Deposition

by Jorge Gil, Abílio de Jesus, Maria Beatriz Silva, Maria F. Vaz, Ana Reis and João Manuel R. S. Tavares

Appl. Sci. 2022, 12(5), 2755; https://doi.org/10.3390/app12052755 - 7 Mar 2022

Cited by 2 | Viewed by 2591

Abstract

Metallic additive manufacturing processes have been significantly developed since their inception with modern systems capable of manufacturing components for structural applications. However, successful processing through these methods requires extensive experimentation before optimised parameters can be found. In laser-based processes, such as direct energy [...] Read more.

Metallic additive manufacturing processes have been significantly developed since their inception with modern systems capable of manufacturing components for structural applications. However, successful processing through these methods requires extensive experimentation before optimised parameters can be found. In laser-based processes, such as direct energy deposition, it is common for single track beads to be deposited and subjected to analysis, yielding information on how the input parameters influence characteristics such as the output’s adhesion to the substrate. These characteristics are often determined using specialised software, from images obtained by cross-section cutting the line beads. The proposed approach was based on a Python algorithm, using the scikit-image library and optical microscopy imaging from produced 18Ni300 Maraging steel on H13 tool steel, and it computes the relevant properties of DED-produced line beads, such as the track height, width, penetration, wettability angles, cross-section areas above and below the substrate and dilution proportion. 18Ni300 Maraging steel depositions were optimised with a laser power of 1550

W

, feeding rate of 12

g

\min^{- 1}

, scanning speed of 12

mm s^{- 1}

, shielding gas flow rate of 25

L

\min^{- 1}

and carrier gas flow rate of 4

L

\min^{- 1}

for a laser spot diameter of

2.1 mm

. Out of the cross-sectioned beads, their respective height, width and penetration were calculated with

2.71 %

,

4.01 %

and

9.35 %

errors; the dilution proportion was computed with

14.15 %

error, the area above the substrate with

5.27 %

error and the area below the substrate with

17.93 %

error. The average computational time for the processing of one image was

12.7

s

. The developed approach was purely segmentational and could potentially benefit from machine-learning implementations. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 7032 KiB

Open AccessArticle

Microstructural and Hardness Behavior of H13 Tool Steel Manufactured by Ultrasound-Assisted Laser-Directed Energy Deposition

by Dmitriy Masaylo, Sergei Igoshin, Anatoly Popovich, Alexey Orlov, Artem Kim and Vera Popovich

Metals 2022, 12(3), 450; https://doi.org/10.3390/met12030450 - 5 Mar 2022

Cited by 5 | Viewed by 3696

Abstract

Metal additive manufacturing (AM) by Laser-Directed Energy Deposition (L-DED) usually results in the formation of textured columnar grains along the build direction, leading to anisotropic mechanical properties. This can negatively affect the intended application of the product. Anisotropy can be eliminated by modifying [...] Read more.

Metal additive manufacturing (AM) by Laser-Directed Energy Deposition (L-DED) usually results in the formation of textured columnar grains along the build direction, leading to anisotropic mechanical properties. This can negatively affect the intended application of the product. Anisotropy can be eliminated by modifying the material through an additional exposure to ultrasound (US-assisted) during the L-DED process. In this paper, a multi-track sample was manufactured from AISI H13 (TLS Technik, Bitterfeld-Wolfen, Germany) tool steel by a US-assisted (28 kHz) L-DED process using a specially designed cooling system. The study also included post-process annealing and quenching with the tempering heat treatment of the modified steel, resulting in the retention of the properties, as confirmed by hardness measurements. XRD analysis was used to measure the structural parameters of the unit cell, and the hardness properties were measured in two directions: longitudinally and parallel to the deposition direction. It was found that US-assisted L-DED allows us to obtain a more isotropic structure with an equal size of the coherent scattering region in two printing directions, and to reduce the residual stresses in the material. The anisotropy of the hardness was significantly reduced, with 636 and 640 HV found between the XY and XZ planes. Based on the obtained hardness data, it should be noted that some of the heat treatments studied herein can also result in a decrease in the anisotropy of the properties, similarly to the US-assisted effect. Full article

(This article belongs to the Topic Additive Manufacturing)

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22 pages, 13988 KiB

Open AccessArticle

Improvement of Cooling Effect and Dimensional Accuracy of Wire and Arc Additive Manufactured Magnesium Alloy by Active-Cooling-Based Contacting Copper Blocks

by Hideaki Nagamatsu and Hiroyuki Sasahara

J. Manuf. Mater. Process. 2022, 6(2), 27; https://doi.org/10.3390/jmmp6020027 - 24 Feb 2022

Cited by 11 | Viewed by 4546

Abstract

Wire and arc additive manufacturing (WAAM) employing a magnesium (Mg) alloy is superior in terms of safety, energy efficiency, and deposition rate when compared with a process that utilizes lasers and powder materials. However, problems with WAAM employing an Mg alloy include poor [...] Read more.

Wire and arc additive manufacturing (WAAM) employing a magnesium (Mg) alloy is superior in terms of safety, energy efficiency, and deposition rate when compared with a process that utilizes lasers and powder materials. However, problems with WAAM employing an Mg alloy include poor dimensional accuracy due to low viscosity of the molten Mg alloy. In addition, since Mg alloys cause a combustion reaction with water, an effective cooling method, such as direct water cooling, cannot be applied. In this study, a solid contact-based active cooling method employing copper blocks with high thermal conductivity was proposed to improve the dimensional accuracy and cooling efficiency of fabricated objects using AZ31. Moreover, the proposed method renders it possible to fabricate a wall structure with high flatness as the molten AZ31 solidifies upon direct contact with the flat surface of copper blocks. In addition, the copper blocks harboring an internal water circulation system achieved a higher cooling efficiency and shortened the interval cooling time between the deposition of subsequent layers. Meanwhile, it was discovered that the arc deflected toward the copper blocks, not onto the substrate or the previous layer when the wire tip approached too close to the blocks. Full article

(This article belongs to the Topic Additive Manufacturing)

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26 pages, 12747 KiB

Open AccessArticle

Design of Particle Dampers for Laser Powder Bed Fusion

by Tobias Ehlers and Roland Lachmayer

Appl. Sci. 2022, 12(4), 2237; https://doi.org/10.3390/app12042237 - 21 Feb 2022

Cited by 17 | Viewed by 3595

Abstract

Additively manufactured particle dampers can significantly improve component damping. However, if designed incorrectly, the damping can be worsened. For the design of additively manufactured particle dampers, there are not yet sufficient design rules and models to describe the effect due to numerous design [...] Read more.

Additively manufactured particle dampers can significantly improve component damping. However, if designed incorrectly, the damping can be worsened. For the design of additively manufactured particle dampers, there are not yet sufficient design rules and models to describe the effect due to numerous design parameters. The research question answered in this paper describes how the effect of particle damping can be characterised as a function of excitation force and excitation frequency for different cavity sizes. To characterise the effect of particle damping, a 3³ full factorial test plan is constructed, and the damping is determined experimentally. It is shown that the damping can be reliably evaluated with the circle-fit method. The effect of particle damping is investigated for beams made of AlSi10Mg, 1.2709 and Ti6Al4V. As a result, a positive effect of the particle damping in a frequency range from 500 to 30,000 Hz and partly up to the 9th bending mode can be proven. It is shown that, for the first bending mode, there is an optimum at approx. 2000 Hz. For the optimum, the increase of the damping for the tool steel 1.2709 to 28 and for the aluminium alloy AlSi10Mg to 18 can be proven. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 104669 KiB

Open AccessArticle

Performance-Driven Engineering Design Approaches Based on Generative Design and Topology Optimization Tools: A Comparative Study

by Loris Barbieri and Maurizio Muzzupappa

Appl. Sci. 2022, 12(4), 2106; https://doi.org/10.3390/app12042106 - 17 Feb 2022

Cited by 37 | Viewed by 12456

Abstract

The advent of Additive Manufacturing (AM) is uncovering the limits of the current CAD systems and, at the same time, is highlighting the potentials of the Topology Optimization (TO) and Generative Design (GD) tools that had not been fully exploited until now. Differently [...] Read more.

The advent of Additive Manufacturing (AM) is uncovering the limits of the current CAD systems and, at the same time, is highlighting the potentials of the Topology Optimization (TO) and Generative Design (GD) tools that had not been fully exploited until now. Differently from the traditional design approach in which designers occupy a predominant role in each stage of the design process, the introduction of such tools in the product development process pushes toward simulation-driven design approaches which imply a significant change in the role of the designer. To this end, the paper presents a comparison of two different design methods for Additive Manufacturing based on the adoption of TO and GD tools. The comparison aims to offer a reflection on the evolution of the traditional approach when TO and GD tools are used, and to highlight the potential and limitations of these optimization tools when adopted in an integrated manner with the CAD systems. Furthermore, this comparative study can be a useful and practical source for designers to identify the most appropriate approach to adopt based on their needs and project resources. The comparative study is carried out through the design study of a prototype of a rocker arm and a brake pedal for the Formula Student race car. Their results, compared in terms of mechanical performances, show that both TO and especially GD tools can be efficiently adopted early in a design process oriented to AM to redesign components to make them lighter and stronger. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 6906 KiB

Open AccessArticle

Experimental Investigation on Inner- and Inter-Strip Reinforcements for 3D Printed Concrete via Automatic Staple Inserting Technique

by Xiangpeng Cao, Shiheng Yu and Hongzhi Cui

Appl. Sci. 2022, 12(4), 2099; https://doi.org/10.3390/app12042099 - 17 Feb 2022

Cited by 6 | Viewed by 3340

Abstract

Lack of reinforcements is an existing drawback of 3D printed cementitious components, which is an urgent concern. A staple-inserting apparatus was developed and installed on a 3D printer and automatically fabricated 3D printed and staple-reinforced components with 98% successful insertion to achieve inner- [...] Read more.

Lack of reinforcements is an existing drawback of 3D printed cementitious components, which is an urgent concern. A staple-inserting apparatus was developed and installed on a 3D printer and automatically fabricated 3D printed and staple-reinforced components with 98% successful insertion to achieve inner- and inter-reinforcement of the printed strips. The inserted staples inside the printed strips improved the compressive strength by 25% maximum owing to the inner locking effect by the staple pins, while the flexural strength did not increase because the scattered staples functioned separately. The staples over the strip interfaces remarkably increased the flexural stress by 46–120%. The inserted staples demonstrated a significant strip locking effect, but the unavoidable voids decreased the bonding between staples and the composite. The mechanical analysis concluded that the printing parameters considerably affected the reinforcing rate. The staple inserting technique proved the feasibility of automatic fabrication of fiber-reinforced and printed concrete structures. Full article

(This article belongs to the Topic Additive Manufacturing)

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20 pages, 5130 KiB

Open AccessArticle

Experimental and Numerical Vibration Analysis of Octet-Truss-Lattice-Based Gas Turbine Blades

by Sajjad Hussain, Wan Aizon W. Ghopa, S. S. K. Singh, Abdul Hadi Azman and Shahrum Abdullah

Metals 2022, 12(2), 340; https://doi.org/10.3390/met12020340 - 15 Feb 2022

Cited by 23 | Viewed by 4509

Abstract

This paper aims to investigate the utilization of octet truss lattice structures in gas turbine blades to achieve weight reduction and improvement in vibration characteristics, which are desired for turbine blades to improve the efficiency and load capacity of turbines. A solid blade [...] Read more.

This paper aims to investigate the utilization of octet truss lattice structures in gas turbine blades to achieve weight reduction and improvement in vibration characteristics, which are desired for turbine blades to improve the efficiency and load capacity of turbines. A solid blade model using NACA 23012 airfoil was designed as reference. Three lattice-based blades were designed and manufactured via additive manufacturing by replacing the internal volume of solid blades with octet truss unit cells of variable strut thickness. Experimental and numerical vibration analyses were performed on the blades to establish their suitability for potential use in turbine blades. A maximum weight reduction of 24.91% was achieved. The natural frequencies of lattice blades were higher than those of solid blades. A stress reduction up to 38.6% and deformation reduction of up to 21.5% compared with solid blades were also observed. Both experimental and numerical results showed good agreement with a maximum difference of 3.94% in natural frequencies. Therefore, apart from being lightweight, octet-truss-lattice-based blades have excellent vibration characteristics and low stress levels, thereby making these blades ideal for enhancing the efficiency and durability of gas turbines. Full article

(This article belongs to the Topic Additive Manufacturing)

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18 pages, 43478 KiB

Open AccessArticle

The Study of Biological Glue Droplet Impact Behavior of Bioceramic Powders Applied in 3D Printing of Bone Scaffolds

by Xin-Pei Li, Yan-En Wang, Ammar Ahmed, Qing-Hua Wei, Ying Guo, Kun Zhang and Yi-Kai Shi

Appl. Sci. 2022, 12(4), 1898; https://doi.org/10.3390/app12041898 - 11 Feb 2022

Cited by 6 | Viewed by 1885

Abstract

This paper aims to develop a reliable and effective model to investigate the behavior of micron-sized biological glue droplets impacting micron-sized bioceramic powder beds applied to the 3D printing process. It also endeavours to explore the common rules of droplet impact affected by [...] Read more.

This paper aims to develop a reliable and effective model to investigate the behavior of micron-sized biological glue droplets impacting micron-sized bioceramic powder beds applied to the 3D printing process. It also endeavours to explore the common rules of droplet impact affected by particle size and the wettability of powder, which are supposed to provide process parameters guidance for the application of new materials in 3D printing. Firstly, based on the low impulse impact model, the simplified model was proposed. Then, the observation and simulation experiments of millimeter-scale droplet impacting were carried out under the same conditions to prove the effectiveness of the model. Furthermore, the characterization of a parametric experiment of a 3D printing practice was used to verify the significance and effectiveness of the simulation study method. Lastly, the method was performed to investigate the effect of wettability and particle size of the micron powder on the micron droplet impact. The results showed that the binder powder’s wettability and particle size could directly influence the droplet spreading behavior. The characterization results of samples printed in the simulation-predicted parameter showed that the amount of binder used could be reduced by 38.8~50.1%, while the green strength only lost 17.9~20%. The significance of this simulation method for prediction of 3D printing process parameters was verified. Full article

(This article belongs to the Topic Additive Manufacturing)

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25 pages, 19269 KiB

Open AccessArticle

Investigation of Material Properties of Wall Structures from Stainless Steel 316L Manufactured by Laser Powder Bed Fusion

by Hoang Minh Vu, Steffen Meiniger, Björn Ringel, Holger Claus Hoche, Matthias Oechsner, Matthias Weigold, Matthias Schmitt and Georg Schlick

Metals 2022, 12(2), 285; https://doi.org/10.3390/met12020285 - 5 Feb 2022

Cited by 7 | Viewed by 3037

Abstract

To make powder bed fusion (PBF) via laser beam (-LB) for metals (/M) available for highly regulated components such as pressure equipment according to the Pressure Equipment Directive, system-specific qualification methods need to be established to deal with process- and geometry-dependent inhomogeneous material [...] Read more.

To make powder bed fusion (PBF) via laser beam (-LB) for metals (/M) available for highly regulated components such as pressure equipment according to the Pressure Equipment Directive, system-specific qualification methods need to be established to deal with process- and geometry-dependent inhomogeneous material behavior. Therefore, the material properties of austenitic stainless steel (316L) and their influences on normative acceptable qualification strategies were investigated in this study. Flat tensile test specimens were produced by two manufacturing systems identical in construction and were compared to specimens produced from conventionally rolled sheet material. Specimens were compared in the horizontal and vertical building directions in relation to different slope angles, wall thicknesses and cross-sectional areas. Despite identical process setups, parameters and powder feedstock, differences in mechanical behavior could be seen. Furthermore, the mechanical properties, surface roughness and density showed dependencies on the wall thickness and slope angle. In particular, the influence of wall thickness has not been covered in publications about PBF-LB/M before. These results suggest that geometry- and system-dependent components can be designed based on associated data from qualification processes. Therefore, a new qualification method based on wall structure properties is suggested for standard qualification processes of components with wall structures, such as pressure equipment. Full article

(This article belongs to the Topic Additive Manufacturing)

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27 pages, 12509 KiB

Open AccessReview

Laser Powder Bed Fusion of Unalloyed Tungsten: A Review of Process, Structure, and Properties Relationships

by Mahmoud S. Seyam, Philip Koshy and Mohamed A. Elbestawi

Metals 2022, 12(2), 274; https://doi.org/10.3390/met12020274 - 2 Feb 2022

Cited by 11 | Viewed by 5128

Abstract

Tungsten (W) as a structural component has grown roots in many special applications owing to its radiation-shielding capabilities and its properties at elevated temperatures. The high ductile-brittle transition temperature (DBTT) and the very high melting point of tungsten however have limited its processability [...] Read more.

Tungsten (W) as a structural component has grown roots in many special applications owing to its radiation-shielding capabilities and its properties at elevated temperatures. The high ductile-brittle transition temperature (DBTT) and the very high melting point of tungsten however have limited its processability to certain technologies such as powder metallurgy. Laser powder bed fusion (LPBF) has been introduced in recent years as an alternative for manufacturing tungsten parts to overcome the design limitations posed by powder metallurgy technology. A review of the literature shows significant improvements in the quality of tungsten components produced by LPBF, implying a strong potential for manufacturing tungsten with this technology and a need for further research on this subject. This review paper presents the current state-of-the-art in LPBF of unalloyed tungsten, with a focus on the effect of process parameters on the developed structure/properties and identifies current knowledge gaps. Full article

(This article belongs to the Topic Additive Manufacturing)

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20 pages, 5499 KiB

Open AccessEditor’s ChoiceArticle

Microstructure Evolution in Inconel 718 Produced by Powder Bed Fusion Additive Manufacturing

by Judy Schneider, Laura Farris, Gert Nolze, Stefan Reinsch, Grzegorz Cios, Tomasz Tokarski and Sean Thompson

J. Manuf. Mater. Process. 2022, 6(1), 20; https://doi.org/10.3390/jmmp6010020 - 29 Jan 2022

Cited by 21 | Viewed by 7862

Abstract

Inconel 718 is a precipitation strengthened, nickel-based super alloy of interest for the Additive Manufacturing (AM) of low volume, complex parts to reduce production time and cost compared to conventional subtractive processes. The AM process involves repeated rapid melting, solidification and reheating, which [...] Read more.

Inconel 718 is a precipitation strengthened, nickel-based super alloy of interest for the Additive Manufacturing (AM) of low volume, complex parts to reduce production time and cost compared to conventional subtractive processes. The AM process involves repeated rapid melting, solidification and reheating, which exposes the material to non-equilibrium conditions that affect elemental segregation and the subsequent formation of solidification phases, either beneficial or detrimental. These variations are difficult to characterize due to the small length scale within the micron sized melt pool. To understand how the non-equilibrium conditions affect the initial solidification phases and their critical temperatures, a multi-length scale, multi modal approach has been taken to evaluate various methods for identifying the initial phases formed in the as-built Inconel 718 produced by laser-powder bed fusion (L-PBF) additive manufacturing (AM). Using a range of characterization tools from the bulk differential thermal analysis (DTA) and x-ray diffraction (XRD) to spatially resolved images using a variety of electron microscopy tools, a better understanding is obtained of how these minor phases can be properly identified regarding the amount and size, morphology and distribution. Using the most promising characterization techniques for investigation of the as-built specimens, those techniques were used to evaluate the specimens after various heat treatments. During the sequence of heat treatments, the initial as-built dendritic structures recrystallized into well-defined grains whose size was dependent on the temperature. Although the resulting strength was similar in all heat treated specimens, the elongation increased as the grain size was refined due to differences in the precipitated phase distribution and morphology. Full article

(This article belongs to the Topic Additive Manufacturing)

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12 pages, 5843 KiB

Open AccessArticle

Mechanical Characterization of AISI 316L Samples Printed Using Material Extrusion

by Mattia Carminati, Mariangela Quarto, Gianluca D’Urso, Claudio Giardini and Giancarlo Maccarini

Appl. Sci. 2022, 12(3), 1433; https://doi.org/10.3390/app12031433 - 28 Jan 2022

Cited by 31 | Viewed by 4384

Abstract

The main additive manufacturing (AM) methods to produce metal components are laser powder bed fusion and directed energy deposition, which are energy-intensive, time-consuming, and require high investment costs. An economical alternative is based on a new feedstock comprising a homogenous mixture of sinterable [...] Read more.

The main additive manufacturing (AM) methods to produce metal components are laser powder bed fusion and directed energy deposition, which are energy-intensive, time-consuming, and require high investment costs. An economical alternative is based on a new feedstock comprising a homogenous mixture of sinterable metal powders and a multi-component binder system. This feedstock enables the creation of metal components printed using the material extrusion (ME) technique. In this study, mechanical characterization of AISI 316L samples is conducted to identify the mechanical properties of parts printed using the metal ME process. The test results indicate an average maximum tensile stress of 426.6 ± 23.7 MPa and an elongation at break of 36%. Both the tensile and compressive yield stresses are approximately 150 MPa, demonstrating a symmetric response to the two opposite types of uniaxial loads. Rockwell B and Vickers hardness tests confirm the uniform behavior of the tested material. An X-ray diffraction analysis is conducted to assess the crystallographic structure of the ME 316L samples compared to that of the monolithic material. According to our study results, metal ME seems to be a promising technology to produce non-critical metallic parts that require good mechanical properties, good corrosion resistance, and complex shapes such as chemical tanks, heat exchangers, and medical instruments. Full article

(This article belongs to the Topic Additive Manufacturing)

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23 pages, 10041 KiB

Open AccessArticle

Hot Stamping Parts Shear Mold Manufacturing via Metal Additive Manufacturing

by Myoung-Pyo Hong

Appl. Sci. 2022, 12(3), 1158; https://doi.org/10.3390/app12031158 - 23 Jan 2022

Cited by 3 | Viewed by 3133

Abstract

Hot stamping uses boron (B) steel to simultaneously form parts at high temperatures while cooling the parts in a mold, which is advantageous because of the ability to freeze the forms. However, compared to conventional cold forming, this technique requires additional facilities that [...] Read more.

Hot stamping uses boron (B) steel to simultaneously form parts at high temperatures while cooling the parts in a mold, which is advantageous because of the ability to freeze the forms. However, compared to conventional cold forming, this technique requires additional facilities that include heating devices and additional time for cooling after forming at high temperatures. Additionally, because of the high strengths of hot stamping parts, shear process operations after molding tend to be difficult to perform as a continuous operation via press processing; thus, most operations depend on separate laser processing, which results in lower productivity and increased manufacturing costs. This limitation continues to be the most significant problem with this technology, therefore, restricting its commercialization because of increased mold manufacturing costs and durability problems. This study investigated a low-cost, high-functionality shear mold manufacturing method for 1.5 GPa grade hot-stamped components using heterogeneous metal additive manufacturing. After the concentrated stress in steel during the shearing processes was analyzed using a multi-physical analysis, metal additive manufacturing was used to fabricate the shear mold. Its life was evaluated through trial molding and compared with that for conventional technology. Finally, the commercialization potential of the newly developed method was assessed. Full article

(This article belongs to the Topic Additive Manufacturing)

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20 pages, 95863 KiB

Open AccessArticle

Scanning Strategy Investigation for Direct Powder Bed Selective Laser Processing of Silicon Carbide Ceramic

by Mohamed Abdelmoula, Alejandro Montón Zarazaga, Gökhan Küçüktürk, Francis Maury, David Grossin and Marc Ferrato

Appl. Sci. 2022, 12(2), 788; https://doi.org/10.3390/app12020788 - 13 Jan 2022

Cited by 14 | Viewed by 3352

Abstract

Direct-Powder Bed Selective Laser Processing (D-PBSLP) is considered a promising technique for the Additive Manufacturing (AM) of Silicon Carbide (SiC). For the successful D-PBSLP of SiC, it is necessary to understand the effects of process parameters. The process parameters are the laser power, [...] Read more.

Direct-Powder Bed Selective Laser Processing (D-PBSLP) is considered a promising technique for the Additive Manufacturing (AM) of Silicon Carbide (SiC). For the successful D-PBSLP of SiC, it is necessary to understand the effects of process parameters. The process parameters are the laser power, scanning speed, hatching distance, and scanning strategies. This study investigates the effect of scanning strategies on the D-PBSLP of SiC and ensures that other process parameters are appropriately selected to achieve this. A numerical model was developed to obtain the proper process parameters for the investigation of scanning strategies in this work. Different scanning strategies available in the commercial Phoenix 3D printer manufactured by 3D Systems, such as concentric in–out, linear, inclined zigzag, and hexagonal, have been investigated. It was concluded that the zigzag strategy is the best scanning strategy, as it was seen that SiC samples could be printed at a high relative density of above 80% without a characteristic pattern on the layer’s top surface. SiC samples were successfully printed using different laser powers and scanning speeds obtained from the numerical model and zigzag strategy. Additionally, complex geometry in the form of triple periodic minimum surface (gyroid) was also successfully printed. Full article

(This article belongs to the Topic Additive Manufacturing)

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15 pages, 5684 KiB

Open AccessArticle

Preparation and Characterisation of Cellulose Nanocrystal/Alginate/Polyethylene Glycol Diacrylate (CNC/Alg/PEGDA) Hydrogel Using Double Network Crosslinking Technique for Bioprinting Application

by Anusha Wei Asohan, Rokiah Hashim, Ku Marsilla Ku Ishak, Zuratul Ain Abdul Hamid, Nurshafiqah Jasme and Yazmin Bustami

Appl. Sci. 2022, 12(2), 771; https://doi.org/10.3390/app12020771 - 13 Jan 2022

Cited by 9 | Viewed by 3863

Abstract

In this study, we aimed to prepare and characterise hydrogel formulations using cellulose nanocrystals (CNCs), alginate (Alg), and polyethylene glycol diacrylate (PEGDA). The CNC/Alg/PEGDA formulations were formed using a double network crosslinking approach. Firstly, CNC was extracted from oil palm trunk, and the [...] Read more.

In this study, we aimed to prepare and characterise hydrogel formulations using cellulose nanocrystals (CNCs), alginate (Alg), and polyethylene glycol diacrylate (PEGDA). The CNC/Alg/PEGDA formulations were formed using a double network crosslinking approach. Firstly, CNC was extracted from oil palm trunk, and the size and morphology of the CNCs were characterised using TEM analysis. Secondly, different formulations were prepared using CNCs, Alg, and PEGDA. The mixtures were crosslinked with Ca²⁺ ions and manually extruded using a syringe before being subjected to UV irradiation at 365 nm. The shear-thinning properties of the formulations were tested prior to any crosslinking, while the determination of storage and loss modulus was conducted post extrusion after the Ca²⁺ ion crosslink using a rheometer. For the analysis of swelling behaviour, the constructs treated with UV were immersed in PBS solution (pH 7.4) for 48 h. The morphology of the UV crosslinked construct was analysed using SEM imaging. The extracted CNC exhibited rod-like structures with an average diameter and length of around 7 ± 2.4 and 113 ± 20.7 nm, respectively. Almost all CNC/Alg/PEGDA formulations (pre-gel formulation) displayed shear-thinning behaviour with the power-law index η < 1, and the behaviour was more prominent in the 1% [w/v] Alg formulations. The CNC/Alg/PEGDA with 2.5% and 4% [w/v] Alg displayed a storage modulus dominance over loss modulus (G′ > G″) which suggests good shape fidelity. After the hydrogel constructs were subjected to UV treatment at 365 nm, only the F8 construct [4% CNC: 4% Alg: 40% PEGDA] demonstrated tough and flexible characteristics that possibly mimic the native articular cartilage property due to a similar water content percentage (79.5%). In addition, the small swelling ratio of 4.877 might contribute to a minimal change of the 3D construct’s geometry. The hydrogel revealed a rough and wavy surface, and the pore size ranged from 3 to 20 µm. Overall, the presence of CNCs in the double network hydrogel demonstrated importance and showed positive effects towards the fabrication of a potentially ideal 3D bioprinted scaffold. Full article

(This article belongs to the Topic Additive Manufacturing)

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21 pages, 14854 KiB

Open AccessArticle

Powder Bed Selective Laser Processing of Alumina: Scanning Strategies Investigation

by Mohamed Abdelmoula, Gökhan Küçüktürk, Enrique Juste and Fabrice Petit

Appl. Sci. 2022, 12(2), 764; https://doi.org/10.3390/app12020764 - 12 Jan 2022

Cited by 17 | Viewed by 2997

Abstract

Powder Bed Selective Laser Processing (PBSLP) is a promising technique for the additive manufacturing of alumina. For the method’s success, PBSLP process parameters such as laser power, scanning speed, hatching distance, and scanning strategies need to be investigated. This paper focuses on studying [...] Read more.

Powder Bed Selective Laser Processing (PBSLP) is a promising technique for the additive manufacturing of alumina. For the method’s success, PBSLP process parameters such as laser power, scanning speed, hatching distance, and scanning strategies need to be investigated. This paper focuses on studying the scanning strategies’ effects on the PBSLP of alumina numerically and experimentally. Scanning strategies such as linear with different orientation, concentric, and islands were investigated. A numerical model was developed in which the PBSLP parameters, scanning strategy effects, and interpreting the experimental results could be observed. The numerical model proved its ability to reach the proper process parameters instead of using experimental trails which are time and cost consuming. For relative density, the island strategy succeeded to print alumina samples with a high relative density reaching 87.8%. However, there are round passages formed inside the samples that remain a barrier for the island strategy to be effectively used in PBSLP of alumina. Both linear and concentric strategies achieved a relative density of 75% and 67%, respectively. Considering the top surface roughness, samples printed with linear strategies gave low top surface roughness compared to the island and concentric strategies. Linear-45° is considered the effective strategy among the studied strategies as it achieved good relative density and low roughness at top and side surfaces. For PBSLP of alumina, new scanning strategies should be considered, and this study presents a new scanning strategy that is mainly based on space filling mathematical curves and should be studied in future work. Full article

(This article belongs to the Topic Additive Manufacturing)

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11 pages, 5162 KiB

Open AccessArticle

The Effect of Acceleration on the Separation Force in Constrained-Surface Stereolithography

by Dmitry Gritsenko, Roberto Paoli and Jie Xu

Appl. Sci. 2022, 12(1), 442; https://doi.org/10.3390/app12010442 - 3 Jan 2022

Cited by 6 | Viewed by 2114

Abstract

Constrained-surface-based stereolithography has recently attracted much attention from both academic and industrial communities. Despite numerous experimental, numerical and theoretical efforts, the fundamental need to reduce the separation force between the newly cured part and constrained surface has not yet been completely solved. In [...] Read more.

Constrained-surface-based stereolithography has recently attracted much attention from both academic and industrial communities. Despite numerous experimental, numerical and theoretical efforts, the fundamental need to reduce the separation force between the newly cured part and constrained surface has not yet been completely solved. In this paper, we develop a fluid dynamics approach, proposed in our previous work, to theoretically model the separation force in 3D printing of a cylindrical part for flat and patterned windows. We demonstrate the possibility of separation force reduction with an accelerated movement of the printing platform. In particular, we investigate behaviors of transient parameter, its reduction rate, and separation force reduction with respect to elevation speed and time. The proposed approach involves deceleration and acceleration stages and allows to achieve the force reduction for the entire printing process. Finally, we provide implicit analytical solutions for time moments when switching between the stages can be done without noticeable increase of separation force and explicit expression for separation force in case of patterned window. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 8877 KiB

Open AccessArticle

Development of a Low-Cost Wire Arc Additive Manufacturing System

by Miguel Navarro, Amer Matar, Seyid Fehmi Diltemiz and Mohsen Eshraghi

J. Manuf. Mater. Process. 2022, 6(1), 3; https://doi.org/10.3390/jmmp6010003 - 24 Dec 2021

Cited by 23 | Viewed by 11645

Abstract

Due to their unique advantages over traditional manufacturing processes, metal additive manufacturing (AM) technologies have received a great deal of attention over the last few years. Using current powder-bed fusion AM technologies, metal components are very expensive to manufacture, and machines are complex [...] Read more.

Due to their unique advantages over traditional manufacturing processes, metal additive manufacturing (AM) technologies have received a great deal of attention over the last few years. Using current powder-bed fusion AM technologies, metal components are very expensive to manufacture, and machines are complex to build and maintain. Wire arc additive manufacturing (WAAM) is a new method of producing metallic components with high efficiency at an affordable cost, which combines welding and 3D printing. In this work, gas tungsten arc welding (GTAW) is incorporated into a gantry system to create a new metal additive manufacturing platform. Design and build of a simple, affordable, and effective WAAM system is explained and the most frequently seen problems are discussed with their suggested solutions. Effect of process parameters on the quality of two additively manufactured alloys including plain carbon steel and Inconel 718 were studied. System design and troubleshooting for the wire arc AM system is presented and discussed. Full article

(This article belongs to the Topic Additive Manufacturing)

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41 pages, 21219 KiB

Open AccessArticle

Multi-Scale Modeling of Residual Stresses Evolution in Laser Powder Bed Fusion of Inconel 625

by Mohamed Balbaa and Mohamed Elbestawi

J. Manuf. Mater. Process. 2022, 6(1), 2; https://doi.org/10.3390/jmmp6010002 - 23 Dec 2021

Cited by 13 | Viewed by 4847

Abstract

Laser powder bed fusion exhibits many advantages for manufacturing complex geometries from hard to machine alloys such as IN625. However, a major drawback is the formation of high tensile residual stresses, and the complex relationship between the process parameters and the residual stresses [...] Read more.

Laser powder bed fusion exhibits many advantages for manufacturing complex geometries from hard to machine alloys such as IN625. However, a major drawback is the formation of high tensile residual stresses, and the complex relationship between the process parameters and the residual stresses has not been fully investigated. The current study presents multi-scale models to examine the variation of process parameters on melt pool dimensions, cyclic temperature evolutions, cooling rate, and cyclic stress generation and how they affect the stress end state. In addition, the effect of the same energy density, which is often overlooked, on the generated residual stresses is investigated. Multi-level validation is performed based on melt pool dimensions, temperature measurements with a two-color pyrometer, and finally, in-depth residual stress measurement. The results show that scan speed has the strongest effect on residual stresses, followed by laser power and hatch spacing. The results are explained in light of the non-linear temperature evolution, temperature gradient, and cooling rate during laser exposure, cooling time, and the rate during recoating time. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 3753 KiB

Open AccessArticle

Hybrid Manufacturing of Stiffening Grooves in Additive Deposited Thin Parts

by Valentino A. M. Cristino, João P. M. Pragana, Ivo M. F. Bragança, Carlos M. A. Silva and Paulo A. F. Martins

J. Manuf. Mater. Process. 2021, 5(4), 140; https://doi.org/10.3390/jmmp5040140 - 20 Dec 2021

Cited by 3 | Viewed by 3467

Abstract

This paper is focused on the hybridization of additive manufacturing with single-point incremental forming to produce stiffening grooves in thin metal parts. An analytical model built upon in-plane stretching of a membrane is provided to determine the tool force as a function of [...] Read more.

This paper is focused on the hybridization of additive manufacturing with single-point incremental forming to produce stiffening grooves in thin metal parts. An analytical model built upon in-plane stretching of a membrane is provided to determine the tool force as a function of the required groove depth and to estimate the maximum allowable groove depth that can be formed without tearing. The results for additively deposited stainless-steel sheets show that the proposed analytical model can replicate incremental plastic deformation of the stiffening grooves in good agreement with experimental observations and measurements. Anisotropy and lower formability caused by the dendritic-based microstructure of the additively deposited stainless-steel sheets justifies the reason why the maximum allowable depth of the stiffening grooves is approximately 27% smaller than that obtained for the wrought commercial sheets of the same material that are used for comparison purposes. Full article

(This article belongs to the Topic Additive Manufacturing)

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12 pages, 3973 KiB

Open AccessArticle

Residual Stresses Control in Additive Manufacturing

by Xufei Lu, Miguel Cervera, Michele Chiumenti and Xin Lin

J. Manuf. Mater. Process. 2021, 5(4), 138; https://doi.org/10.3390/jmmp5040138 - 16 Dec 2021

Cited by 40 | Viewed by 6580

Abstract

Residual stresses are one of the primary causes for the failure of parts or systems in metal additive manufacturing (AM), since they easily induce crack propagation and structural distortion. Although the formation of residual stresses has been extensively studied, the core factors steering [...] Read more.

Residual stresses are one of the primary causes for the failure of parts or systems in metal additive manufacturing (AM), since they easily induce crack propagation and structural distortion. Although the formation of residual stresses has been extensively studied, the core factors steering their development in AM have not been completely uncovered. To date, several strategies based on reducing the thermal gradients have been developed to mitigate the manifestation of residual stresses in AM; however, how to choose the optimal processing plan is still unclear for AM designers. In this regard, the concept of the yield temperature, related to the thermal deformation and the mechanical constraint, plays a crucial role for controlling the residual stresses, but it has not been duly investigated, and the corresponding approach to control stresses is also yet lacking. To undertake such study, a three-bar model is firstly used to illustrate the formation mechanism of the residual stress and its key causes. Next, an experimentally calibrated thermomechanical finite element model is used to analyze the sensitivity of the residual stresses to the scan pattern, preheating, energy density, and the part geometry and size, as well as the substrate constraints. Based on the numerical results obtained from this analysis, recommendations on how to minimize the residual stresses during the AM process are provided. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 551 KiB

Open AccessArticle

Prioritization of Challenges for the Effectuation of Sustainable Additive Manufacturing: A Case Study Approach

by Naif Alsaadi

Processes 2021, 9(12), 2250; https://doi.org/10.3390/pr9122250 - 14 Dec 2021

Cited by 8 | Viewed by 2417

Abstract

Additive manufacturing (AM) is gaining significant importance, as demand for customized products is increasing nowadays. AM is one of the disruptive technologies of Industry 4.0, which can reduce waste generation, enabling sustainability. The adoption of sustainable practices in the manufacturing sector is due [...] Read more.

Additive manufacturing (AM) is gaining significant importance, as demand for customized products is increasing nowadays. AM is one of the disruptive technologies of Industry 4.0, which can reduce waste generation, enabling sustainability. The adoption of sustainable practices in the manufacturing sector is due to the need of the current scenario to minimize harmful emissions and for human wellbeing. In this regard, AM technologies are integrated with sustainable manufacturing concepts to contribute toward sustainable AM (SAM), with various benefits from the design, manufacturing, use, and EoL perspectives. Still, many sustainability issues are associated with AM processes, namely limited speed and the uncertain performance of fabricated parts. From this viewpoint, it is essential to analyze the challenges associated with adopting SAM practices. This article presents identification and analysis of the potential challenges associated with adopting SAM practices. Fifteen SAM challenges have been identified from the literature survey and analyzed using the “Gray Technique for Order of Preference by Similarity to Ideal Solution” (G-TOPSIS) approach. The priority order of the challenges has been identified. The study identified that “training towards SAM benefits” and “limited materials recycling potential” were the significant challenges in adopting SAM practices in the manufacturing sector. The present study will help industry practitioners, decision makers, and researchers effectively analyze the challenges associated with SAM for its effective implementation. Researchers can utilize the findings of the study for establishing the guidelines for the adoption of SAM. Full article

(This article belongs to the Topic Additive Manufacturing)

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41 pages, 9367 KiB

Open AccessReview

Applications of Machine Learning in Process Monitoring and Controls of L-PBF Additive Manufacturing: A Review

by Dalia Mahmoud, Marcin Magolon, Jan Boer, M. A. Elbestawi and Mohammad Ghayoomi Mohammadi

Appl. Sci. 2021, 11(24), 11910; https://doi.org/10.3390/app112411910 - 14 Dec 2021

Cited by 57 | Viewed by 8473

Abstract

One of the main issues hindering the adoption of parts produced using laser powder bed fusion (L-PBF) in safety-critical applications is the inconsistencies in quality levels. Furthermore, the complicated nature of the L-PBF process makes optimizing process parameters to reduce these defects experimentally [...] Read more.

One of the main issues hindering the adoption of parts produced using laser powder bed fusion (L-PBF) in safety-critical applications is the inconsistencies in quality levels. Furthermore, the complicated nature of the L-PBF process makes optimizing process parameters to reduce these defects experimentally challenging and computationally expensive. To address this issue, sensor-based monitoring of the L-PBF process has gained increasing attention in recent years. Moreover, integrating machine learning (ML) techniques to analyze the collected sensor data has significantly improved the defect detection process aiming to apply online control. This article provides a comprehensive review of the latest applications of ML for in situ monitoring and control of the L-PBF process. First, the main L-PBF process signatures are described, and the suitable sensor and specifications that can monitor each signature are reviewed. Next, the most common ML learning approaches and algorithms employed in L-PBFs are summarized. Then, an extensive comparison of the different ML algorithms used for defect detection in the L-PBF process is presented. The article then describes the ultimate goal of applying ML algorithms for in situ sensors, which is closing the loop and taking online corrective actions. Finally, some current challenges and ideas for future work are also described to provide a perspective on the future directions for research dealing with using ML applications for defect detection and control for the L-PBF processes. Full article

(This article belongs to the Topic Additive Manufacturing)

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19 pages, 25816 KiB

Open AccessArticle

Influence of LPBF-Surface Characteristics on Fatigue Properties of Scalmalloy^®

by Jens Musekamp, Thorsten Reiber, Holger Claus Hoche, Matthias Oechsner, Matthias Weigold and Eberhard Abele

Metals 2021, 11(12), 1961; https://doi.org/10.3390/met11121961 - 6 Dec 2021

Cited by 24 | Viewed by 4106

Abstract

Laser powder bed fusion (LPBF) has indisputable advantages when designing new components with complex geometries due to toolless manufacturing and the ability to manufacture components with undercuts. However, fatigue properties rely heavily on the surface condition. In this work, in-process surface parameters (three [...] Read more.

Laser powder bed fusion (LPBF) has indisputable advantages when designing new components with complex geometries due to toolless manufacturing and the ability to manufacture components with undercuts. However, fatigue properties rely heavily on the surface condition. In this work, in-process surface parameters (three differing contour parameter sets) and post-process surface treatments, namely turning and shot peening, are varied to investigate the influence of each treatment on the resulting fatigue properties of LPBF-manufactured specimens of the aluminium–magnesium–scandium alloy Scalmalloy^®. Therefore, metallographic analysis and surface roughness measurements, as well as residual stress measurements, computer tomography measurements, SEM-analyses, tensile and fatigue tests, along with fracture surface analysis, were performed. Despite the fact that newly developed in-process contour parameters are able to reduce the surface roughness significantly, only a minor improvement in fatigue properties could be observed: Crack initiation is caused by sharp, microscopic notches at the surface in combination with high tensile residual stresses at the surface, which are present on all in-process contour parameter specimens. Specimens using contour parameters with high line energy show keyhole pores localized in the subsurface area, which have no effect on crack initiation. Contours with low line energy have a slightly positive effect on fatigue strength because less pores can be found at the surface and subsurface area, which even more greatly promotes an early crack initiation. The post-process parameter sets, turning and shot peening, both improve fatigue behaviour significantly: Turned specimens show lowest surface roughness, while, for shot peened specimens, the tensile residual stresses of the surface radially shifted from the surface towards the centre of the specimens, which counteracts the crack initiation at the surface. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 3501 KiB

Open AccessCommunication

Prediction and Compensation of Color Deviation by Response Surface Methodology for PolyJet 3D Printing

by Xingjian Wei, Abhinav Bhardwaj, Li Zeng and Zhijian Pei

J. Manuf. Mater. Process. 2021, 5(4), 131; https://doi.org/10.3390/jmmp5040131 - 4 Dec 2021

Cited by 8 | Viewed by 4049

Abstract

PolyJet 3D printing can produce any color by mixing multiple materials. However, there are often large deviations between the measured color of printed samples and the target color (when the target color is used as the specified color in the printer software). Therefore, [...] Read more.

PolyJet 3D printing can produce any color by mixing multiple materials. However, there are often large deviations between the measured color of printed samples and the target color (when the target color is used as the specified color in the printer software). Therefore, to achieve a target color on a printed sample, the specified color in the printer software should not be the same as the target color. This study applies response surface methodology (RSM) to determine the optimal color specification to compensate for color deviations of the measured color of printed samples from the target color in PolyJet 3D printing. The RSM has three steps. First, a set of experiments are designed for a target color according to central composite design. Second, the experimental data are used to develop a second-order multivariate multiple regression model to predict the deviation between the measured color and the target color. Third, the optimal color specification (often different from the target color) is determined by using the developed predictive model and the desirability function. When the optimal color specification is used as the specified color in the printer software, the deviation between the predicted color of the printed sample and the target color is minimized. The proposed method is applied to four target colors to demonstrate its effectiveness. The results show that the proposed method performs better than the conventional color specification method without compensation in achieving the four target colors by 33% on average. Full article

(This article belongs to the Topic Additive Manufacturing)

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12 pages, 9269 KiB

Open AccessArticle

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

by Maxim Bassis, Abram Kotliar, Rony Koltiar, Tomer Ron, Avi Leon, Amnon Shirizly and Eli Aghion

Metals 2021, 11(12), 1930; https://doi.org/10.3390/met11121930 - 29 Nov 2021

Cited by 8 | Viewed by 2894

Abstract

The wire laser additive manufacturing (WLAM) process is considered a direct-energy deposition method that aims at addressing the need to produce large components having relatively simple geometrics at an affordable cost. This additive manufacturing (AM) process uses wires as raw materials instead of [...] Read more.

The wire laser additive manufacturing (WLAM) process is considered a direct-energy deposition method that aims at addressing the need to produce large components having relatively simple geometrics at an affordable cost. This additive manufacturing (AM) process uses wires as raw materials instead of powders and is capable of reaching a deposition rate of up to 3 kg/h, compared with only 0.1 kg/h with common powder bed fusion (PBF) processes. Despite the attractiveness of the WLAM process, there has been only limited research on this technique. In particular, the stress corrosion properties of components produced by this technology have not been the subject of much study. The current study aims at evaluating the effect of a slow strain rate on the stress corrosion resistance of 316L stainless steel produced by the WLAM process in comparison with its counterpart: AISI 316L alloy. Microstructure examination was carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis, while the mechanical properties were evaluated using tensile strength and hardness measurements. The general corrosion resistance was examined by potentiodynamic polarization and impedance spectroscopy analysis, while the stress corrosion performance was assessed by slow strain rate testing (SSRT) in a 3.5% NaCl solution at ambient temperature. The attained results highlight the inferior mechanical properties, corrosion resistance and stress corrosion performance, especially at a slow strain rate, of the WLAM samples compared with the regular AISI 316L alloy. The differences between the WLAM alloy and AISI 316L alloy were mainly attributed to their dissimilarities in terms of phase compositions, structural morphology and inherent defects. Full article

(This article belongs to the Topic Additive Manufacturing)

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10 pages, 6062 KiB

Open AccessArticle

Preparation of a Nickel Layer with Bell-Mouthed Macropores via the Dual-Template Method

by Ruishan Yang, Weiguo Yao, Guangguang Qian and Yanli Dou

Metals 2021, 11(12), 1894; https://doi.org/10.3390/met11121894 - 25 Nov 2021

Cited by 1 | Viewed by 1945

Abstract

A relatively static and unique bubble template is successfully realized on a microporous substrate by controlling the surface tensions of the electrodeposit solution, and a nickel layer containing macropores is prepared using this bubble template. When the surface tension of the solution is [...] Read more.

A relatively static and unique bubble template is successfully realized on a microporous substrate by controlling the surface tensions of the electrodeposit solution, and a nickel layer containing macropores is prepared using this bubble template. When the surface tension of the solution is 50.2 mN/m, the desired bubble template can be formed, there are fewer bubbles attached to other areas on the substrate, and a good nickel layer is obtained. In the analysis of the macropore formation process, it is found that the size of the bell-mouthed macropores can be tailored by changing the solution stirring speed or the current density to adjust the growth rate of the bubble template. The size change of a macropore is measured by the profile angle of the longitudinal macropore, section. As the solution stirring speed increases from 160 to 480 r/min, the angle range of the bell-mouthed macropores cross-sectional profile is increased from 21.0° to 44.3°. In addition, the angle range of the bell-mouthed macropore cross-sectional profile is increased from 39.3° to 46.3° with the current density increasing from 1 to 2.5 A/dm². Different from the dynamic hydrogen bubble template, the bubble template implemented in this paper stays attached on the deposition and grows slowly, which is novel and interesting, and the nickel layer containing macropores prepared using this bubble template is applied in completely different fields. Full article

(This article belongs to the Topic Additive Manufacturing)

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16 pages, 2859 KiB

Open AccessArticle

Feasibility of Acoustic Print Head Monitoring for Binder Jetting Processes with Artificial Neural Networks

by Philipp Lechner, Philipp Heinle, Christoph Hartmann, Constantin Bauer, Benedikt Kirchebner, Fabian Dobmeier and Wolfram Volk

Appl. Sci. 2021, 11(22), 10672; https://doi.org/10.3390/app112210672 - 12 Nov 2021

Cited by 3 | Viewed by 2355

Abstract

The clogging of piezoelectric nozzles is a typical problem in various additive binder jetting processes, such as the manufacturing of casting molds. This work aims at print head monitoring in these binder jetting processes. The structure-born noise of piezoelectric print modules is analyzed [...] Read more.

The clogging of piezoelectric nozzles is a typical problem in various additive binder jetting processes, such as the manufacturing of casting molds. This work aims at print head monitoring in these binder jetting processes. The structure-born noise of piezoelectric print modules is analyzed with an Artificial Neural Network to classify whether the nozzles are functional or clogged. The acoustic data are studied in the frequency domain and utilized as input for an Artificial Neural Network. We found that it is possible to successfully classify individual nozzles well enough to implement a print head monitoring, which automatically determines whether the print head needs maintenance. Full article

(This article belongs to the Topic Additive Manufacturing)

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15 pages, 7177 KiB

Open AccessArticle

The Effect of Anodization on the Mechanical Properties of AA6061 Produced by Additive Friction Stir-Deposition

by Ning Zhu, Dustin Z. Avery, Ben A. Rutherford, Brandon J. Phillips, Paul G. Allison, J. Brian Jordon and Luke N. Brewer

Metals 2021, 11(11), 1773; https://doi.org/10.3390/met11111773 - 4 Nov 2021

Cited by 25 | Viewed by 3056

Abstract

This paper examines the impact of oxide coatings on the surfaces of feedstock material used for Additive Friction Stir-Deposition (AFS-D). The AFS-D is a solid-state additive manufacturing process that uses severe plastic deformation and frictional heating to build bulk depositions from either metallic [...] Read more.

This paper examines the impact of oxide coatings on the surfaces of feedstock material used for Additive Friction Stir-Deposition (AFS-D). The AFS-D is a solid-state additive manufacturing process that uses severe plastic deformation and frictional heating to build bulk depositions from either metallic rod or powder feedstock. Since aluminum alloys naturally form an oxide layer, it is important to determine the influence of the feedstock surface oxide layer on the resultant as-deposited microstructure and mechanical properties. In this study, three AA6061 square-rod feedstock materials were used, each with a different thickness of aluminum oxide coating: non-anodized, 10-micron thick, and 68-micron thick. Macroscale depositions were produced with these feedstock rods using the AFS-D process. Optical and electron microscopy showed that the two oxide coatings applied through anodization were efficiently dispersed during the AFS-D process, with oxide particles distributed throughout the microstructure. These oxide particles had median sizes of 1.8 and 3 μm², respectively. The yield and tensile strengths of these materials were not measurably impacted by the thickness of the starting oxide coating. While all three feedstock material variations failed by ductile rupture, the elongation-to-failure did decrease from 68% to 55% in the longitudinal direction and from 60% to 43% in the build direction for the thickest initial oxide coating, 68 microns. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 4829 KiB

Open AccessArticle

Plasma Spheroidisation of Irregular Ti6Al4V Powder for Powder Bed Fusion

by Nthateng Nkhasi, Willie du Preez and Hertzog Bissett

Metals 2021, 11(11), 1763; https://doi.org/10.3390/met11111763 - 2 Nov 2021

Cited by 5 | Viewed by 3275

Abstract

Metal powders suitable for use in powder bed additive manufacturing processes should ideally be spherical, dense, chemically pure and of a specified particle size distribution. Ti6Al4V is commonly used in the aerospace, medical and automotive industries due to its high strength-to-weight ratio and [...] Read more.

Metal powders suitable for use in powder bed additive manufacturing processes should ideally be spherical, dense, chemically pure and of a specified particle size distribution. Ti6Al4V is commonly used in the aerospace, medical and automotive industries due to its high strength-to-weight ratio and excellent corrosion resistance properties. Interstitial impurities in titanium alloys have an impact upon mechanical properties, particularly oxygen, nitrogen, hydrogen and carbon. The plasma spheroidisation process can be used to spheroidise metal powder consisting of irregularly shaped particles. In this study, the plasma spheroidisation of metal powder was performed on Ti6Al4V powder consisting of irregularly shaped particles. The properties of the powder relevant for powder bed fusion that were determined included the particle size distribution, morphology, particle porosity and chemical composition. Conclusions were drawn regarding the viability of using this process to produce powder suitable for additive manufacturing. Full article

(This article belongs to the Topic Additive Manufacturing)

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9 pages, 2638 KiB

Open AccessArticle

The Influence of Heat Input on the Surface Quality of Wire and Arc Additive Manufacturing

by Jiayi Zeng, Wenzhong Nie and Xiaoxuan Li

Appl. Sci. 2021, 11(21), 10201; https://doi.org/10.3390/app112110201 - 30 Oct 2021

Cited by 11 | Viewed by 2855

Abstract

Wire and arc additive manufacturing has unique process characteristics, which make it have great potential in many fields, but the large amount of heat input brought by this feature limits its practical application. The influence of heat input on the performance of parts [...] Read more.

Wire and arc additive manufacturing has unique process characteristics, which make it have great potential in many fields, but the large amount of heat input brought by this feature limits its practical application. The influence of heat input on the performance of parts has been extensively studied, but the quantitative description of the influence of heat input on the surface quality of parts by wire and arc additive manufacturing has not received enough attention. According to different heat input, select the appropriate process parameters for wire and arc additive manufacturing, reversely shape the profile model, select the appropriate function model to establish the ideal profile model according to the principle of minimum error, and compare the two models to analyze the effect of heat input on the surface quality of the parts manufactured by wire and arc additive manufacturing. The results show that, when the heat input is high or low, the standard deviation value and the root mean square value reach 1.908 and 1.963, respectively. The actual profile is larger than the ideal profile. When the heat input is moderate, the standard deviation value and the root mean square value are only 1.634 and 1.713, respectively, and the actual contour is in good agreement with the ideal contour. Combined with the analysis of the transverse and longitudinal sections, it is shown that the heat input has a high degree of influence on the surface quality of the specimen manufactured by wire and arc additive manufacturing, and higher or lower heat input is disadvantageous to it. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 5721 KiB

Open AccessArticle

Enabling Multi-Material Structures of Co-Based Superalloy Using Laser Directed Energy Deposition Additive Manufacturing

by Beytullah Aydogan and Himanshu Sahasrabudhe

Metals 2021, 11(11), 1717; https://doi.org/10.3390/met11111717 - 27 Oct 2021

Cited by 8 | Viewed by 3446

Abstract

Cobalt superalloys such as Tribaloys are widely used in environments that involve high temperatures, corrosion, and wear degradation. Additive manufacturing (AM) processes have been investigated for fabricating Co-based alloys due to design flexibility and efficient materials usage. AM processes are suitable for reducing [...] Read more.

Cobalt superalloys such as Tribaloys are widely used in environments that involve high temperatures, corrosion, and wear degradation. Additive manufacturing (AM) processes have been investigated for fabricating Co-based alloys due to design flexibility and efficient materials usage. AM processes are suitable for reducing the manufacturing steps and subsequently reducing manufacturing costs by incorporating multi-materials. Laser directed energy deposition (laser DED) is a suitable AM process for fabricating Co-based alloys. T800 is one of the commercially available Tribaloys that is strengthened through Laves phases and of interest to diverse engineering fields. However, the high content of the Laves phase makes the alloy prone to brittle fracture. In this study, a Ni-20%Cr alloy was used to improve the fabricability of the T800 alloy via laser DED. Different mixture compositions (20%, 30%, 40% NiCr by weight) were investigated. The multi-material T800 + NiCr alloys were heat treated at two different temperatures. These alloy chemistries were characterized for their microstructural, phase, and mechanical properties in the as-fabricated and heat-treated conditions. SEM and XRD characterization indicated the stabilization of ductile phases and homogenization of the Laves phases after laser DED fabrication and heat treatment. In conclusion, the NiCr addition improved the fabricability and structural integrity of the T800 alloy. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 29077 KiB

Open AccessArticle

Coupled Flexural-Electrical Evaluation of Additively Manufactured Multifunctional Composites at Ambient Temperature

by Ritesh Ghimire and Frank Liou

Appl. Sci. 2021, 11(20), 9638; https://doi.org/10.3390/app11209638 - 15 Oct 2021

Cited by 1 | Viewed by 2542

Abstract

Multifunctional composites offer a higher strength to weight ratio, electrical properties, etc., thereby providing possible solutions for replacing the physical electrical wirings in aircraft. The lack of research on the coupled multifunctional characterization of 3D printed composites flexural-electrical properties is the main reason [...] Read more.

Multifunctional composites offer a higher strength to weight ratio, electrical properties, etc., thereby providing possible solutions for replacing the physical electrical wirings in aircraft. The lack of research on the coupled multifunctional characterization of 3D printed composites flexural-electrical properties is the main reason for its unsuitability in aerospace applications. The proposed method evaluates multifunctional flexural-electrical properties of 3D printed multifunctional carbon fiber composites. Traditional methods for conducting structural and electrical analyses for aircraft certification do not accommodate new technologies that are not yet proven. Such technologies are additive manufacturing (AM) techniques, multifunctional composite structures, and the certification requirements for 3D printed multifunctional carbon fiber composites for use in aircraft. In this study, the multifunctional 3D printed specimens were concurrently evaluated for flexural-electrical properties using three-point bending and electrical conductivity tests. The results showed that the multifunctional properties included the maximum flexural strength of 271 MPa and the maximum electrical resistance of 55.1 G Ohms, with the failure modes and mechanisms found to be consistent with the traditional composites. Due to its infancy, the existing AM techniques, and the use of the multifunctional carbon fiber composites manufactured using those AM technologies, are not implemented on a large commercial scale. Full article

(This article belongs to the Topic Additive Manufacturing)

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12 pages, 89001 KiB

Open AccessArticle

Effect of the Melt Pool Boundary Network on the Anisotropic Mechanical Properties of Selective Laser Melted 304L

by Myranda Spratt, Joseph W. Newkirk, Okanmisope Fashanu and K. Chandrashekhara

J. Manuf. Mater. Process. 2021, 5(4), 110; https://doi.org/10.3390/jmmp5040110 - 15 Oct 2021

Viewed by 2755

Abstract

Anisotropic mechanical properties are a well-known issue in selective laser melted parts. The microstructure produced by selective laser melting (SLM) is directional, including the solidified melt pool structures and grains. This work investigates the melt pool boundary’s effects on 304L stainless steel’s compressive [...] Read more.

Anisotropic mechanical properties are a well-known issue in selective laser melted parts. The microstructure produced by selective laser melting (SLM) is directional, including the solidified melt pool structures and grains. This work investigates the melt pool boundary’s effects on 304L stainless steel’s compressive properties. 304L stainless steel solid cylinders were built using a pulse laser SLM machine in four directions using three hatch angle rotations: 0°, 67°, and 105°. The twelve samples were compression tested, and the results were analyzed. Numerical models were also created with the different hatch angles and directions. The melt pool boundary network (MPBN) in each build was tracked using the model across multiple planes. Results showed that both the hatch angle and build orientation influenced the concentration of melt pool boundaries present in the manufactured samples. A weak negative correlation of compressive strength to the melt pool boundaries’ concentration was also observed, indicating that the melt pool boundary concentration negatively affected the material’s strength. Local anisotropic plastic deformation was also observed in some of the compressed samples. In those samples, it was observed that directions that plastically deformed more also contained higher concentration of the melt pool boundaries. Full article

(This article belongs to the Topic Additive Manufacturing)

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15 pages, 8249 KiB

Open AccessArticle

A Voxel-Based Watermarking Scheme for Additive Manufacturing

by Shyh-Kuang Ueng, Ya-Fang Hsieh and Yu-Chia Kao

Appl. Sci. 2021, 11(19), 9177; https://doi.org/10.3390/app11199177 - 2 Oct 2021

Cited by 2 | Viewed by 2224

Abstract

Digital and analog contents, generated in additive manufacturing (AM) processes, may be illegally modified, distributed, and reproduced. In this article, we propose a watermarking scheme to enhance the security of AM. Compared with conventional watermarking methods, our algorithm possesses the following advantages. First, [...] Read more.

Digital and analog contents, generated in additive manufacturing (AM) processes, may be illegally modified, distributed, and reproduced. In this article, we propose a watermarking scheme to enhance the security of AM. Compared with conventional watermarking methods, our algorithm possesses the following advantages. First, it protects geometric models and printed parts as well as G-code programs. Secondly, it embeds watermarks into both polygonal and volumetric models. Thirdly, our method is capable of creating watermarks inside the interiors and on the surfaces of complex models. Fourth, the watermarks may appear in various forms, including character strings, cavities, embossed bumps, and engraved textures. The proposed watermarking method is composed of the following steps. At first, the input geometric model is converted into a distance field. Then, the watermark is inserted into a region of interest by using self-organizing mapping. Finally, the watermarked model is converted into a G-code program by using a specialized slicer. Several robust methods are also developed to authenticate digital models, G-code programs, and physical parts. These methods perform virtual manufacturing, volume rendering, and image processing to extract watermarks from these contents at first. Then, they employ similarity evaluation and visual comparison to verify the extracted signatures. Some experiments had been conducted to validify the proposed watermarking method. The test results, analysis, discussion, and comparisons are also presented in this article. Full article

(This article belongs to the Topic Additive Manufacturing)

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18 pages, 1225 KiB

Open AccessConcept Paper

Additive Manufacturing in the Clothing Industry: Towards Sustainable New Business Models

by Siavash H. Khajavi

Appl. Sci. 2021, 11(19), 8994; https://doi.org/10.3390/app11198994 - 27 Sep 2021

Cited by 18 | Viewed by 10388

Abstract

The clothing industry is among the most polluting and waste-generating industries in the world, and it is responsible for the release of large amounts of greenhouse gases. The industry’s massive size and significant environmental footprint with regard to water and energy consumption and [...] Read more.

The clothing industry is among the most polluting and waste-generating industries in the world, and it is responsible for the release of large amounts of greenhouse gases. The industry’s massive size and significant environmental footprint with regard to water and energy consumption and waste generation make it a valid improvement candidate. While in recent years, global clothing brands and retailers have taken steps to reduce their ecological footprint, there still is a lot of room for improvement. In this research, we view this sustainability issue from a lifecycle perspective and study the new business models (NBMs) that may arise from the utilization of additive manufacturing (AM) technology. AM is emerging as a method of production for final parts. Moreover, as the range of material and available production processes expands, it is increasingly important to study the potential impact of this promising production technology and potential NBMs enabled by it on the clothing industry. Additionally, the obstacles to AM utilization in the clothing industry are explored. We utilize secondary data related to relevant implementation cases to theoretically study the NBMs that AM can enable to improve sustainability. Three NBMs of “clothing as a service”, “collaborative consumption”, and “direct sale/distribution” were envisioned through the study of current AM applications in other industries, as well as current fashion trends. The results of this research have implications for the sustainability of the fashion industry while also providing directions for AM technology development. Full article

(This article belongs to the Topic Additive Manufacturing)

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18 pages, 5354 KiB

Open AccessArticle

Comparison of Properties and Bead Geometry in MIG and CMT Single Layer Samples for WAAM Applications

by Harley Stinson, Richard Ward, Justin Quinn and Cormac McGarrigle

Metals 2021, 11(10), 1530; https://doi.org/10.3390/met11101530 - 26 Sep 2021

Cited by 19 | Viewed by 5123

Abstract

The process of Wire Arc Additive Manufacturing (WAAM) utilizes arc welding technology to fabricate metallic components by depositing material in a selective layered fashion. Several welding processes exist that can achieve this layered deposition strategy. Gas Metal Arc Welding (GMAW) derived processes are [...] Read more.

The process of Wire Arc Additive Manufacturing (WAAM) utilizes arc welding technology to fabricate metallic components by depositing material in a selective layered fashion. Several welding processes exist that can achieve this layered deposition strategy. Gas Metal Arc Welding (GMAW) derived processes are commonly favored for their high deposition rates (1–4 kg/h) and minimal torch reorientation required during deposition. A range of GMAW processes are available; all of which have different material transfer modes and thermal energy input ranges and the resultant metallic structures formed from these processes can vary in their mechanical properties and morphology. This work will investigate single-layer deposition and vary the process parameters and process mode to observe responses in mechanical properties, bead geometry and deposition rate. The process modes selected for this study were GMAW derived process of Metal Inert Gas (MIG) and Cold Metal Transfer (CMT). Characterization of parameter sets revealed relationships between torch travel speeds, wire feed speeds and the specimen properties and proportions. Differences were observed in the cross-sectional bead geometry and deposition rates when comparing MIG and CMT samples though the influence of process mode on mechanical properties was less significant compared to process parameter selection. Full article

(This article belongs to the Topic Additive Manufacturing)

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16 pages, 4125 KiB

Open AccessArticle

High-Speed Cutting of Synthetic Trabecular Bone—A Combined Experimental–Computational Investigation

by Macdarragh O’Neill and Ted J. Vaughan

Appl. Mech. 2021, 2(3), 650-665; https://doi.org/10.3390/applmech2030037 - 20 Sep 2021

Viewed by 2503

Abstract

Orthopaedic surgical cutting instruments are required to generate sufficient forces to penetrate bone tissue while minimising the risk of thermal and mechanical damage to the surrounding environment. This study presents a combined experimental–computational approach to determine relationships between key cutting parameters and overall [...] Read more.

Orthopaedic surgical cutting instruments are required to generate sufficient forces to penetrate bone tissue while minimising the risk of thermal and mechanical damage to the surrounding environment. This study presents a combined experimental–computational approach to determine relationships between key cutting parameters and overall cutting performance of a polyurethane-based synthetic trabecular bone analogue under orthogonal cutting conditions. An experimental model of orthogonal cutting was developed, whereby an adaptable cutting tool fixture driven by a servo-hydraulic uniaxial test machine was used to carry out cutting tests on Sawbone^® trabecular bone analogues. A computational model of the orthogonal cutting process was developed using Abaqus/Explicit, whereby an Isotropic Hardening Crushable Foam elastic-plastic model was used to capture the complex post-yield behaviour of the synthetic trabecular bone. It was found that lower tool rake angles resulted in the formation of larger discontinuous chips and higher cutting forces, while higher rake angles tended to lead to more continuous chip formation and lower cutting forces. The computational modelling framework provided captured features of both chip formation and axial cutting forces over a wide range of cutting parameters when compared with experimental observations. This experimentally based computational modelling framework for orthogonal cutting of trabecular bone analogues has the potential to be applied to more complex three-dimensional cutting processes in the future. Full article

(This article belongs to the Topic Additive Manufacturing)

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23 pages, 6411 KiB

Open AccessReview

Academic Insights and Perspectives in 3D Printing: A Bibliometric Review

by Wenyu Bai, Hui Fang, Yawen Wang, Qiang Zeng, Guangyao Hu, Guanjun Bao and Yuehua Wan

Appl. Sci. 2021, 11(18), 8298; https://doi.org/10.3390/app11188298 - 7 Sep 2021

Cited by 24 | Viewed by 8770

Abstract

Research interest in three-dimensional (3D) printing has been greatly aroused since 1990 due to its outstanding merits, such as freedom of design, mass customization, waste minimization and fast prototyping complex structures. To formally elaborate the research status of the 3D printing field, a [...] Read more.

Research interest in three-dimensional (3D) printing has been greatly aroused since 1990 due to its outstanding merits, such as freedom of design, mass customization, waste minimization and fast prototyping complex structures. To formally elaborate the research status of the 3D printing field, a bibliometric analysis is applied to evaluate the related publications from 1990 to 2020 based on the Science Citation Index Expanded database and Social Science Citation Index database. The overview with detailed discussions is cataloged by keywords, citation, h-index, year, journal, institution, country, author, patent and review. The statistical results show that the United States plays a dominant role in this research field, followed by China and the UK. Singapore is the most productive country with the highest average citations per publication (ACPP), and the second most cooperative country. Among all the institutions, Chinese Academy of Sciences is most productive, and Harvard University has the highest ACPP and h-index. Among all the journals, Materials ranks first in the number of publications in this field. The most attractive research area is “Materials science, Multidisciplinary”, with 4053 publications. Moreover, the major hot topics derived from authors’ keywords are “3D printing”, “additive manufacturing” and “tissue engineering”. Commercial and medical applications appear to be the initial driving force and end goal for the development of the 3D printing technology. Full article

(This article belongs to the Topic Additive Manufacturing)

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23 pages, 8346 KiB

Open AccessArticle

Dense Robust 3D Reconstruction and Measurement for 3D Printing Process Based on Vision

by Ning Lv, Chengyu Wang, Yujing Qiao and Yongde Zhang

Appl. Sci. 2021, 11(17), 7961; https://doi.org/10.3390/app11177961 - 28 Aug 2021

Cited by 5 | Viewed by 2644

Abstract

The 3D printing process lacks real-time inspection, which is still an open-loop manufacturing process, and the molding accuracy is low. Based on the 3D reconstruction theory of machine vision, in order to meet the applicability requirements of 3D printing process detection, a matching [...] Read more.

The 3D printing process lacks real-time inspection, which is still an open-loop manufacturing process, and the molding accuracy is low. Based on the 3D reconstruction theory of machine vision, in order to meet the applicability requirements of 3D printing process detection, a matching fusion method is proposed. The fast nearest neighbor (FNN) method is used to search matching point pairs. The matching point information of FFT-SIFT algorithm based on fast Fourier transform is superimposed with the matching point information of AKAZE algorithm, and then fused to obtain more dense feature point matching information and rich edge feature information. Combining incremental SFM algorithm with global SFM algorithm, an integrated SFM sparse point cloud reconstruction method is developed. The dense point cloud is reconstructed by PMVs algorithm, the point cloud model is meshed by Delaunay triangulation, and then the accurate 3D reconstruction model is obtained by texture mapping. The experimental results show that compared with the classical SIFT algorithm, the speed of feature extraction is increased by 25.0%, the number of feature matching is increased by 72%, and the relative error of 3D reconstruction results is about 0.014%, which is close to the theoretical error. Full article

(This article belongs to the Topic Additive Manufacturing)

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20 pages, 3811 KiB

Open AccessArticle

On the Impact of Additive Manufacturing Processes Complexity on Modelling

by Panagiotis Stavropoulos, Panagis Foteinopoulos and Alexios Papapacharalampopoulos

Appl. Sci. 2021, 11(16), 7743; https://doi.org/10.3390/app11167743 - 23 Aug 2021

Cited by 26 | Viewed by 4179

Abstract

The interest in additive manufacturing (AM) processes is constantly increasing due to the many advantages they offer. To this end, a variety of modelling techniques for the plethora of the AM mechanisms has been proposed. However, the process modelling complexity, a term that [...] Read more.

The interest in additive manufacturing (AM) processes is constantly increasing due to the many advantages they offer. To this end, a variety of modelling techniques for the plethora of the AM mechanisms has been proposed. However, the process modelling complexity, a term that can be used in order to define the level of detail of the simulations, has not been clearly addressed so far. In particular, one important aspect that is common in all the AM processes is the movement of the head, which directly affects part quality and build time. The knowledge of the entire progression of the phenomenon is a key aspect for the optimization of the path as well as the speed evolution in time of the head. In this study, a metamodeling framework for AM is presented, aiming to increase the practicality of simulations that investigate the effect of the movement of the head on part quality. The existing AM process groups have been classified based on three parameters/axes: temperature of the process, complexity, and part size, where the complexity has been modelled using a dedicated heuristic metric, based on entropy. To achieve this, a discretized version of the processes implicated variables has been developed, introducing three types of variable: process parameters, key modeling variables and performance indicators. This can lead to an enhanced roadmap for the significance of the variables and the interpretation and use of the various models. The utilized spectrum of AM processes is discussed with respect to the modelling types, namely theoretical/computational and experimental/empirical. Full article

(This article belongs to the Topic Additive Manufacturing)

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17 pages, 13843 KiB

Open AccessArticle

Research on the Dynamic Compressive Deformation Behavior of 3D-Printed Ti6Al4V

by Bo Pu, Wenbin Li, Qing Zhang, Yu Zheng and Xiaoming Wang

Metals 2021, 11(8), 1327; https://doi.org/10.3390/met11081327 - 23 Aug 2021

Cited by 5 | Viewed by 2743

Abstract

In this paper, the plastic flow and fracture behavior of 3D-printed Ti6Al4V (TC-4) alloy under different temperatures (289–1073 K) and strain rates (0.1–4100 s⁻¹) were studied by using the MTS comprehensive experimental machine (MTS) and split Hopkinson pressure bar (SHPB) equipment. [...] Read more.

In this paper, the plastic flow and fracture behavior of 3D-printed Ti6Al4V (TC-4) alloy under different temperatures (289–1073 K) and strain rates (0.1–4100 s⁻¹) were studied by using the MTS comprehensive experimental machine (MTS) and split Hopkinson pressure bar (SHPB) equipment. The patterns of the influence of temperature and strain rate on the plastic flow behavior of 3D-printed materials in different printing directions were analyzed and compared with those of the traditional TC-4. Based on the experimental data, the modified Johnson–Cook (J-C) constitutive model of 3D-printed TC-4 alloy was established, and the plastic deformation behavior of the material driven by detonation was studied by X-ray photography. The research results showed that under static loading conditions, the strength of the material (AM-P-TC-4) along the printing direction was much higher than the strength of the material perpendicular to the printing direction (AM-T-TC-4). However, there was no difference in material strength for different directions under dynamic loading. Second, under the same deformation conditions, the strength of the 3D-printed TC-4 alloy was considerably higher than that of the traditional TC-4 alloy, but adiabatic shear fracture could be more easily induced under dynamic compressive deformation conditions for the 3D-printed TC-4 alloy, and its fracture strain was substantially less than that of TC-4 alloys. The modified J-C constitutive model established in this paper could better describe the plastic flow behavior of the AM-P-TC-4 alloy under high temperature and high-strain rate deformation conditions. Full article

(This article belongs to the Topic Additive Manufacturing)

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15 pages, 3833 KiB

Open AccessArticle

The Effect of Hot Isostatic Pressing on Surface Integrity, Microstructure and Strength of Hybrid Metal Injection Moulding, and Laser-Based Powder Bed Fusion Stainless-Steel Components

by Aldi Mehmeti, Donal Lynch, Pavel Penchev, Rafael Martinez Ramos, Denis Vincent, Johannes Maurath, David Ian Wimpenny, Khamis Essa and Stefan Dimov

Appl. Sci. 2021, 11(16), 7490; https://doi.org/10.3390/app11167490 - 15 Aug 2021

Cited by 6 | Viewed by 3422

Abstract

Hybrid manufacture of components by combining capabilities of replication and additive manufacturing processes offer a flexible and sustainable route for producing cost-effectively small batches of metal parts. At present, there are open issues related to surface integrity and performance of such parts, especially [...] Read more.

Hybrid manufacture of components by combining capabilities of replication and additive manufacturing processes offer a flexible and sustainable route for producing cost-effectively small batches of metal parts. At present, there are open issues related to surface integrity and performance of such parts, especially when utilising them in safety critical applications. The research presented in this paper investigates the ductility amplification of hybrid components produced using metal injection moulding to preform and then build on them customisable sections by laser-based powder bed fusion. The properties of such hybrid components are studied and optimised through the use of non-conventional post treatment techniques. In particular, hot isostatic pressing (HIP) is employed to improve mechanical strength and to produce hybrid components that have consistent properties across batches and throughout the samples, minimising microstructural heterogeneities between fabrication processes. Thus, the investigated post-processing method can offer an extended service life of hybrid components, especially when operating under severe conditions. The optimised post treatment was found to increase the hybrid components’ strength compared to as-built ones by 68% and ~11% in yield strength (YS) and ultimate tensile strength (UTS), respectively. Subsequently, leading to a great pitting resistance, thus, making HIP samples suitable for corrosive environments. The advantages of the HIP treatments in comparison to the conventional heat treatment of hybrid components are discussed and also some potential application areas are proposed. Full article

(This article belongs to the Topic Additive Manufacturing)

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60 pages, 25236 KiB

Open AccessReview

Additive Manufacturing of Bulk Metallic Glasses—Process, Challenges and Properties: A Review

by Navid Sohrabi, Jamasp Jhabvala and Roland E. Logé

Metals 2021, 11(8), 1279; https://doi.org/10.3390/met11081279 - 12 Aug 2021

Cited by 66 | Viewed by 9554

Abstract

Bulk Metallic Glasses (BMG) are metallic alloys that have the ability to solidify in an amorphous state. BMGs show enhanced properties, for instance, high hardness, strength, and excellent corrosion and wear resistance. BMGs produced by conventional methods are limited in size due to [...] Read more.

Bulk Metallic Glasses (BMG) are metallic alloys that have the ability to solidify in an amorphous state. BMGs show enhanced properties, for instance, high hardness, strength, and excellent corrosion and wear resistance. BMGs produced by conventional methods are limited in size due to the high cooling rates required to avoid crystallization and the associated detrimental mechanical properties. Additive manufacturing (AM) techniques are a potential solution to this problem as the interaction between the heat source, e.g., laser, and the feedstock, e.g., powder, is short and confined to a small volume. However, producing amorphous parts with AM techniques with mechanical properties comparable to as-cast samples remains a challenge for most BMGs, and a complete understanding of the crystallization mechanisms is missing. This review paper tries to cover recent progress in this field and develop a thorough understanding of the correlation between different aspects of the topic. The following subjects are addressed: (i) AM techniques used for the fabrication of BMGs, (ii) particular BMGs used in AM, (iii) specific challenges in AM of BMGs such as the control of defects and crystallization, (iv) process optimization of mechanical properties, and (v) future trends. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 2636 KiB

Open AccessArticle

A Comparative Study of Fatigue Energy Dissipation of Additive Manufactured and Cast AlSi10Mg Alloy

by Chunxia Yang, Ke Zhu, Yayan Liu, Yusheng Cai, Wencheng Liu, Keming Zhang and Jia Huang

Metals 2021, 11(8), 1274; https://doi.org/10.3390/met11081274 - 12 Aug 2021

Cited by 9 | Viewed by 2715

Abstract

In this paper, the fatigue energy dissipation of Gravity Casting (GC) and Laser-based Powder Bed Fusion (LPBF) AlSi10Mg alloys under cyclic loading are investigated. The increase in surface temperature related to the energy dissipation effect is decoupled and used to predict the fatigue [...] Read more.

In this paper, the fatigue energy dissipation of Gravity Casting (GC) and Laser-based Powder Bed Fusion (LPBF) AlSi10Mg alloys under cyclic loading are investigated. The increase in surface temperature related to the energy dissipation effect is decoupled and used to predict the fatigue limits of GC and LPBF AlSi10Mg alloys as being 55.8% UTS and 33.9% UTS, respectively. The energy dissipation rate is obtained by solving the one-dimensional thermal diffusion problem. This energy dissipation is separated into related and unrelated fatigue damage using polynomial function fitting. The energy dissipation related to fatigue damage for LPBF specimens is observed to be higher than that of GC specimens, which indicates worse fatigue performance. The fatigue damage entropy is employed to predict the fatigue life of both GC and LPBF AlSi10Mg alloys, which has a good agreement with the results of a traditional fatigue experiment. Full article

(This article belongs to the Topic Additive Manufacturing)

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24 pages, 9008 KiB

Open AccessArticle

Additive Manufacturing of Bone Scaffolds Using PolyJet and Stereolithography Techniques

by Shummaila Rasheed, Waqas Akbar Lughmani, Muhannad Ahmed Obeidi, Dermot Brabazon and Inam Ul Ahad

Appl. Sci. 2021, 11(16), 7336; https://doi.org/10.3390/app11167336 - 9 Aug 2021

Cited by 18 | Viewed by 4693

Abstract

In this study, the printing capability of two different additive manufacturing (3D printing) techniques, namely PolyJet and micro-stereolithography (µSLA), are investigated regarding the fabrication of bone scaffolds. The 3D-printed scaffold structures are used as supports in replacing and repairing fractured bone tissue. Printed [...] Read more.

In this study, the printing capability of two different additive manufacturing (3D printing) techniques, namely PolyJet and micro-stereolithography (µSLA), are investigated regarding the fabrication of bone scaffolds. The 3D-printed scaffold structures are used as supports in replacing and repairing fractured bone tissue. Printed bone scaffolds with complex structures produced using additive manufacturing technology can mimic the mechanical properties of natural human bone, providing lightweight structures with modifiable porosity levels. In this study, 3D scaffold structures are designed with different combinations of architectural parameters. The dimensional accuracy, permeability, and mechanical properties of complex 3D-printed scaffold structures are analyzed to compare the advantages and drawbacks associated with the two techniques. The fluid flow rates through the 3D-printed scaffold structures are measured and Darcy’s law is applied to calculate the experimentally measured permeability. The Kozeny–Carman equation is applied for theoretical calculation of permeability. Compression tests were performed on the printed samples to observe the effects of the printing techniques on the mechanical properties of the 3D-printed scaffold structures. The effect of the printing direction on the mechanical properties of the 3D-printed scaffold structures is also analyzed. The scaffold structures printed with the µSLA printer demonstrate higher permeability and mechanical properties as compared to those printed using the PolyJet technique. It is demonstrated that both the µSLA and PolyJet printing techniques can be used to print 3D scaffold structures with controlled porosity levels, providing permeability in a similar range to human bone. Full article

(This article belongs to the Topic Additive Manufacturing)

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13 pages, 16138 KiB

Open AccessFeature PaperArticle

Wire Arc Additive Manufacturing with Novel Al-Mg-Si Filler Wire—Assessment of Weld Quality and Mechanical Properties

by René Winterkorn, Andreas Pittner and Michael Rethmeier

Metals 2021, 11(8), 1243; https://doi.org/10.3390/met11081243 - 5 Aug 2021

Cited by 11 | Viewed by 2866

Abstract

Wire arc additive manufacturing enables the production of near-net shape large-volume metallic components leveraging an established industrial base of welding and cladding technology and adapting it for layer-wise material deposition. However, the complex relationship between the process parameters and resulting mechanical properties of [...] Read more.

Wire arc additive manufacturing enables the production of near-net shape large-volume metallic components leveraging an established industrial base of welding and cladding technology and adapting it for layer-wise material deposition. However, the complex relationship between the process parameters and resulting mechanical properties of the components still remains challenging. In case of high-strength Al-Mg-Si aluminum alloys, no commercial filler wires are yet available due the high susceptibility of solidification cracking as well as the necessary efforts to obtain acceptable mechanical properties. To address this need, we evaluated a novel filler wire based on AlMg0.7Si doped with a Ti5B1 master alloy to foster fine equiaxed grains within the deposited metal. The correlation between the process parameters and component quality was examined by analyzing the size and distribution of pores as well as the grain morphology. Furthermore, we evaluated the influence of different post-weld heat treatment strategies to achieve mechanical properties corresponding to the reference wrought material. We demonstrated that fine equiaxed grains in the weld metal reduced the susceptibility of solidification cracking significantly. The novel AlMg0.7Si-TiB (S Al 6063-TiB) filler wire facilitated wire arc additive manufacturing of high-strength aluminum components with mechanical properties that were almost as superior as the corresponding wrought base material. Full article

(This article belongs to the Topic Additive Manufacturing)

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14 pages, 5205 KiB

Open AccessArticle

Effect of Surface Sandblasting and Turning on Compressive Strength of Thin 316L Stainless Steel Shells Produced by Laser Powder Bed Fusion

by Bharat Mehta, Eduard Hryha, Lars Nyborg, Frederic Tholence and Erik Johansson

Metals 2021, 11(7), 1070; https://doi.org/10.3390/met11071070 - 2 Jul 2021

Cited by 8 | Viewed by 3234

Abstract

This study evaluates the effect of post-manufacturing treatment on the compressive performance of additively manufactured components. The components were thin cylindrical shells with an aspect ratio of 25:1 manufactured using laser powder bed fusion and that were then surface treated by means of [...] Read more.

This study evaluates the effect of post-manufacturing treatment on the compressive performance of additively manufactured components. The components were thin cylindrical shells with an aspect ratio of 25:1 manufactured using laser powder bed fusion and that were then surface treated by means of sandblasting or turning. The as-printed and subsequently surface treated samples were uniaxially compressed until failure to depict the effect of the surface condition on the compressive mechanical behavior. The results show that as the surfaces became smoother via sandblasting, the average peak strength for buckling load improves negligibly (0.85%), whereas this effect reaches 6.5% upon surface layer removal via turning. Through microstructural investigation and co-relating this with an understanding of processing conditions existing in manufacturing itself, this effect is seen to be linked to contour scanning causing softening of the surface region in a component. Full article

(This article belongs to the Topic Additive Manufacturing)

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20 pages, 17987 KiB

Open AccessArticle

Infill Design Reinforcement of 3D Printed Parts Using Refinement Technique Adapted to Continuous Extrusion

by Sashi Kiran Madugula, Laurence Giraud-Moreau, Pierre-Antoine Adragna and Laurent Daniel

J. Manuf. Mater. Process. 2021, 5(3), 71; https://doi.org/10.3390/jmmp5030071 - 1 Jul 2021

Cited by 2 | Viewed by 4749

Abstract

In this paper, we introduce an advanced numerical tool aimed to optimise the infill design of 3D printed parts by reducing printing time. In 3D printing, the term infill refers to the internal structure of a part. To create the infill design, slicing [...] Read more.

In this paper, we introduce an advanced numerical tool aimed to optimise the infill design of 3D printed parts by reducing printing time. In 3D printing, the term infill refers to the internal structure of a part. To create the infill design, slicing software is used, which generally creates the infill uniformly throughout the part. When such a part is subjected to external loading, all the infill regions will not experience the same amount of stress. Therefore, using uniform infill throughout the part is not the most optimised solution in terms of material usage. We do propose to evolve the infill design with respect to the mechanical stresses generated by the external loads. To achieve this, an advanced numerical tool has been developed, based on refinement techniques, to control the infill design. This tool is coupled with Finite Element Simulation (FE Simulation) software, which helps to identify the zones where the material is required as an infill to reinforce a part, whereas the refinement technique makes it possible to place the material as an infill in such a way that the airtime during the printing of the part is zero. Zero airtime printing is defined as the ability to deposit each layer of a part, without stopping the material extrusion during the displacement of the nozzle. Therefore, the proposed numerical tool guides us to generate the infill design of a part, in such a way that it will consume zero airtime while manufacturing. Simultaneously, it will increase the stiffness of the part. The proposed approach is here applied to a rectangular structure subjected to four-point bending, made up of PLA material (Poly-Lactic Acid). Full article

(This article belongs to the Topic Additive Manufacturing)

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19 pages, 16143 KiB

Open AccessFeature PaperArticle

Fatigue Performance of an Additively Manufactured Zr-Based Bulk Metallic Glass and the Effect of Post-Processing

by Navid Sohrabi, Milad Hamidi-Nasab, Baptiste Rouxel, Jamasp Jhabvala, Annapaola Parrilli, Maurizio Vedani and Roland E. Logé

Metals 2021, 11(7), 1064; https://doi.org/10.3390/met11071064 - 1 Jul 2021

Cited by 14 | Viewed by 4665

Abstract

Fatigue is the most common cause of failure of mechanical parts in engineering applications. In the current work, we investigate the fatigue life of a bulk metallic (BMG) glass fabricated via additive manufacturing. Specimens fabricated via laser powder-bed fusion (LPBF) are shown to [...] Read more.

Fatigue is the most common cause of failure of mechanical parts in engineering applications. In the current work, we investigate the fatigue life of a bulk metallic (BMG) glass fabricated via additive manufacturing. Specimens fabricated via laser powder-bed fusion (LPBF) are shown to have a fatigue ratio of 0.20 (fatigue limit of 175 MPa) in a three-point bending fatigue test. Three strategies for improving the fatigue behavior were tested, namely (1) relaxation heat treatment, giving a slight fatigue life improvement at high loading conditions (≥250 MPa), (2) laser shock peening, and (3) changing the build orientation, the latter two of which yielded no significant effects. It was found that the presence of lack of fusion (LoF) had the preponderant effect on fatigue resistance of the specimens manufactured. LoF was observed to be a source of stress localization and initiation of cracks. The fatigue life in BMGs fabricated by LPBF is thus primarily influenced by powder quality and process-induced defects, which cannot be removed by the post-treatments carried out in this study. It is believed that a slight increase in laser power, either in the near-surface regions or in the core of the specimens, could improve the fatigue behavior despite the associated (detrimental) increase of crystallized fraction. Full article

(This article belongs to the Topic Additive Manufacturing)

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25 pages, 8309 KiB

Open AccessArticle

Characterization of Geometry and Surface Texture of AlSi10Mg Laser Powder Bed Fusion Channels Using X-ray Computed Tomography

by Christopher G. Klingaa, Filippo Zanini, Sankhya Mohanty, Simone Carmignato and Jesper H. Hattel

Appl. Sci. 2021, 11(9), 4304; https://doi.org/10.3390/app11094304 - 10 May 2021

Cited by 6 | Viewed by 2680

Abstract

Channels manufactured by laser powder bed fusion have an inherent process-induced dross formation and surface texture that require proper characterization for design and process optimization. This work undertakes surface texture characterization of AlSi10Mg channels of nominal diameter sizes ranging from 1 mm to [...] Read more.

Channels manufactured by laser powder bed fusion have an inherent process-induced dross formation and surface texture that require proper characterization for design and process optimization. This work undertakes surface texture characterization of AlSi10Mg channels of nominal diameter sizes ranging from 1 mm to 9 mm using X-ray computed tomography. Profile parameters, including Pa, Pz, and Pq, were found to be interchangeable for qualitative characterization of surface texture variation. Psk, Pvv, and the fractal dimension could identify the presence of extreme dross and sintered particles on the measured profiles. A method for predicting the equivalent diameter of the unobstructed cross-sectional area (D_eq) was presented and its reduction was found to follow a logarithmic trend, as a function of channel length. An empirical model Pa (β, D), as a function of local angular position (β) and channel diameter (D), was demonstrated on a perfect channel geometry, resulting in well-predicted roughness and internal geometry. Full article

(This article belongs to the Topic Additive Manufacturing)

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