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Additive Manufacturing Technologies and Its Applications Using Advanced Materials
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Additive Manufacturing Technologies and Its Applications Using Advanced Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (15 April 2022) | Viewed by 55041

Special Issue Editor

Prof. Dong-Gyu Ahn

E-Mail Website
Guest Editor
Chosun University, Gwangju, South Korea
Interests: development of additive manufacturing (AM) process; applications of AM; design for AM; numerical simulation of metal AM processes

Special Issue Information

Dear Colleagues,

One of the major issues of additive manufacturing (AM) today is the development of novel AM technologies using advanced materials to expand scientific and industrial applications. The part quality, which depends on AM technologies, is greatly influenced by applied AM processes, deposition methodologies, and post-processing techologies. Numerical analyses, including heat transfer and residual stress analyses, are needed to create desired parts without defects using the AM process. The application of the AM process using advanced materials can improve functionality and desired characteristics of the product.

Therefore, this Special Issue shall focus on recent works related to additive manufacturing technologies and their applications using advanced materials. Topics can include but are not limited to:

  1. Additive manufacturing process using advanced materials;
  2. Post-processing technology of AM parts (including heat treatment and microstructure modification, etc.);
  3. Application of AM technology to improve functionality of parts;
  4. Application of AM technology using advanced materials;
  5. Numerical analysis of additive manufacturing process for metallic and non-metallic materials;
  6. Review of AM technologies and their applications using advanced materials.

Prof. Dong-Gyu Ahn
Guest Editor

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Keywords

  • additive manufacturing (AM) process
  • applications of AM
  • advanced materials
  • post-processing of AM parts
  • numerical analysis of AM processes

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Published Papers (18 papers)

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Research

13 pages, 5895 KiB  
Article
Fabrication of Thermochromic Membrane and Its Characteristics for Fever Detection
by Hyeon Seop Jeon, Jeong Hwa Kim, Martin B. G. Jun and Young Hun Jeong
Materials 2021, 14(13), 3460; https://doi.org/10.3390/ma14133460 - 22 Jun 2021
Cited by 7 | Viewed by 2453
Abstract
Body temperature is an important indicator of the health status of the human body. Thus, numerous studies have been conducted in various fields to measure body temperature. In this study, a biocompatible thermochromic membrane that changes its color when the temperature becomes higher [...] Read more.
Body temperature is an important indicator of the health status of the human body. Thus, numerous studies have been conducted in various fields to measure body temperature. In this study, a biocompatible thermochromic membrane that changes its color when the temperature becomes higher than the transition temperature for thermochromism was fabricated using an extrusion-based three-dimensional printing process. The printing material was prepared by mixing a thermochromic pigment and a thermoplastic polymer in various ratios. The effects of mixing ratio on the various properties of the fabricated membranes were experimentally investigated. It is presented that the fabricated lattice membrane had excellent thermochromic reaction, which was experimentally evaluated using a measurement of color brightness. The pigment content affected the diameter and surface morphology of the printed filament. The elastic modulus decreased, and thermochromic response became faster as the pigment concentration increased. Subsequently, a patch for fever detection was developed and then attached to the skin to demonstrate its color change according to body temperature. Results show that the fabricated thermochromic patch could be successfully applied to fever detection. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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17 pages, 8599 KiB  
Article
Numerical Investigation of Deposition Characteristics of PLA on an ABS Plate Using a Material Extrusion Process
by Bih-Lii Chua, Sun-Ho Baek, Keun Park and Dong-Gyu Ahn
Materials 2021, 14(12), 3404; https://doi.org/10.3390/ma14123404 - 19 Jun 2021
Cited by 4 | Viewed by 2422
Abstract
Three-dimensional prototypes and final products are commonly fabricated using the material extrusion (ME) process in additive manufacturing applications. However, these prototypes and products are limited to a single material using the ME process due to technical challenges. Deposition of plastic on another dissimilar [...] Read more.
Three-dimensional prototypes and final products are commonly fabricated using the material extrusion (ME) process in additive manufacturing applications. However, these prototypes and products are limited to a single material using the ME process due to technical challenges. Deposition of plastic on another dissimilar plastic substrate requires proper control of printing temperature during an ME process due to differences in melting temperatures of dissimilar plastics. In this paper, deposition of PLA filament on an ABS substrate during an ME process is investigated using finite element analysis. A heat transfer finite element (FE) model for the extrusion process is proposed to estimate the parameters of the ME machine for the formulation of a heat flux model. The effects of printing temperature and the stand-off distance on temperature distributions are investigated using the proposed FE model for the extrusion process. The heat flux model is implemented in a proposed heat transfer FE model of single bead deposition of PLA on an ABS plate. From this FE model of deposition, temperature histories during the ME deposition process are estimated. The results of temperature histories are compared with experiments. Using the calibrated FE model, a proper heating temperature of ABS for deposition of PLA is evaluated. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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18 pages, 15196 KiB  
Article
The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties
by Yongjie Zhang and Seung Ki Moon
Materials 2021, 14(11), 2907; https://doi.org/10.3390/ma14112907 - 28 May 2021
Cited by 18 | Viewed by 3473
Abstract
Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical [...] Read more.
Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical performance issue, thermal annealing process is frequently utilized. However, problems such as distortion issues and the need for jigs and fixtures limit the effectiveness of the thermal annealing process, especially for low volume complex FFF parts. In this research, a novel low temperature thermal annealing is proposed to address the limitations in conventional annealing. A modified orthogonal array design is applied to investigate the performance of ULTEM™ 9085 FFF coupons. Further, the coupons are annealed with specialized support structures, which are co-printed with the coupons during the manufacturing process. Once the annealing process is completed, multiscale characterizations are performed to identify the mechanical properties of the specimens. Geometrical measurement of post annealed specimens indicates an expansion in the layering direction, which indicates relief of thermal stresses. Moreover, annealed coupons show an improvement in tensile strength and reduction in strain concentration. Mesostructure and fracture surface analysis indicate an increase in ductility and enhanced coalescence. This research shows that the proposed annealing methodology can be applied to enhance the mechanical performance of FFF parts without significant distortion. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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27 pages, 12188 KiB  
Article
Effects of Deposition Strategy and Preheating Temperature on Thermo-Mechanical Characteristics of Inconel 718 Super-Alloy Deposited on AISI 1045 Substrate Using a DED Process
by Ho Kim, Kwang-Kyu Lee, Dong-Gyu Ahn and Hyub Lee
Materials 2021, 14(7), 1794; https://doi.org/10.3390/ma14071794 - 5 Apr 2021
Cited by 11 | Viewed by 3331
Abstract
Thermomechanical characteristics are highly dependent on the deposition strategy of the directed energy deposition (DED) process, including the deposition path, the interpass time, the deposition volume, etc., as well as the preheating condition of the substrate. This paper aims to investigate the effects [...] Read more.
Thermomechanical characteristics are highly dependent on the deposition strategy of the directed energy deposition (DED) process, including the deposition path, the interpass time, the deposition volume, etc., as well as the preheating condition of the substrate. This paper aims to investigate the effects of the deposition strategy and the preheating temperature on thermomechanical characteristics of Inconel 718 super-alloy deposited on an AISI 1045 substrate using a DED process via finite element analyses (FEAs). FE models for different deposition strategies and preheating temperatures are created to examine the thermomechanical behavior. Sixteen deposition strategies are adopted to perform FEAs. The heat sink coefficient is estimated from a comparison of temperature histories of experiments and those of FEAs to obtain appropriate FE models. The influence of deposition strategies on residual stress distributions in the designed model for a small volume deposition is examined to determine feasible deposition strategies. In addition, the effects of the deposition strategy and the preheating temperature on residual stress distributions of the designed part for large volume deposition are investigated to predict a suitable deposition strategy of the DED head and appropriate preheating temperature of the substrate. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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18 pages, 6979 KiB  
Article
Irreversible and Repeatable Shape Transformation of Additively Manufactured Annular Composite Structures
by Bona Goo, Jong-Bong Kim, Dong-Gyu Ahn and Keun Park
Materials 2021, 14(6), 1383; https://doi.org/10.3390/ma14061383 - 12 Mar 2021
Cited by 10 | Viewed by 2013
Abstract
Four-dimensional (4D) printing is a unique application of additive manufacturing (AM) which enables additional shape transformations over time. Although 4D printing is an interesting and attractive phenomenon, it still faces several challenges before it can be used for practical applications: (i) the manufacturing [...] Read more.
Four-dimensional (4D) printing is a unique application of additive manufacturing (AM) which enables additional shape transformations over time. Although 4D printing is an interesting and attractive phenomenon, it still faces several challenges before it can be used for practical applications: (i) the manufacturing cost should be competitive, and (ii) the shape transformations must have high dimensional accuracy and repeatability. In this study, an irreversible and repeatable thermoresponsive shape transformation method was developed using a material extrusion type AM process and a plain thermoplastic polymer (ABS) without a shape-memory function. Various types of annular discs were additively manufactured using printing paths programmed along a circular direction, and additional heat treatment was conducted as a thermal stimulus. The programmed circumferential anisotropy led to a unique 2D-to-3D shape transformation in response to the thermal stimulus. To obtain more predictable and repeatable shape transformation, the thermal stimulus was applied while using a geometric constraint. The relevant dimensional accuracy and repeatability of the constrained and unconstrained thermal deformations were compared. The proposed shape transformation method was further applied to AM and to the in situ assembly of a composite frame–membrane structure, where a functional membrane was integrated into a curved 3D frame without any additional assembly procedure. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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21 pages, 12111 KiB  
Article
Surface Modification Using Assisting Electrodes in Wire Electrical Discharge Machining for Silicon Wafer Preparation
by Chunliang Kuo, Yupang Nien, Anchun Chiang and Atsushi Hirata
Materials 2021, 14(6), 1355; https://doi.org/10.3390/ma14061355 - 11 Mar 2021
Cited by 6 | Viewed by 2411
Abstract
This paper outlines notable advances in the wire electrical discharge machining of polycrystalline silicon workpieces for wafer preparation. Our use of assisting electrodes permits the transfer of aluminum particles to the machined surface of the polycrystalline silicon workpieces, to enhance conductivity and alter [...] Read more.
This paper outlines notable advances in the wire electrical discharge machining of polycrystalline silicon workpieces for wafer preparation. Our use of assisting electrodes permits the transfer of aluminum particles to the machined surface of the polycrystalline silicon workpieces, to enhance conductivity and alter surface topography regardless of the silicon’s crystallographic structure and diamond-type lattice. This in-process surface modification technique was shown to promote material removal and simultaneously preserve the integrity of the machined surfaces with preferable surface textures. In the validation experiment, the 25 mm-thick assisting electrodes deposited a notable concentration of aluminium on the machined surface (~3.87 wt %), which greatly accelerated the rate of material removal (~9.42 mg/s) with minimal surface roughness (Sa ~5.49 μm) and moderate skewness (−0.23). The parameter combination used to obtain the optimal surface roughness (Sa 2.54 μm) was as follows: open voltage (80 V), electrical resistance (1.7 Ω), pulse-on time (30 μs), and electrode thickness (15 mm). In multiple objective optimization, the preferred parameter combination (open voltage = 80 V, resistance = 1.4 Ω, pulse-on time = 60 μs, and assisting electrode thickness = 25 mm) achieved the following appreciable results: surface modification of 3.26 ± 0.61 wt %, material removal rate of 7.08 ± 2.2 mg/min, and surface roughness of Sa = 4.3 ± 1.67 μm. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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11 pages, 5772 KiB  
Article
Evaluation of 3D Templated Synthetic Vascular Graft Compared with Standard Graft in a Rat Model: Potential Use as an Artificial Vascular Graft in Cardiovascular Disease
by Sung-Hwa Sohn, Tae-Hee Kim, Tae-Sik Kim, Too-Jae Min, Ju-Han Lee, Sung-Mook Yoo, Ji-Won Kim, Ji-Eun Lee, Chae-Hwa Kim, Suk-Hee Park and Won-Min Jo
Materials 2021, 14(5), 1239; https://doi.org/10.3390/ma14051239 - 5 Mar 2021
Cited by 17 | Viewed by 3470
Abstract
Although the number of vascular surgeries using vascular grafts is increasing, they are limited by vascular graft-related complications and size discrepancy. Current efforts to develop the ideal synthetic vascular graft for clinical application using tissue engineering or 3D printing are far from satisfactory. [...] Read more.
Although the number of vascular surgeries using vascular grafts is increasing, they are limited by vascular graft-related complications and size discrepancy. Current efforts to develop the ideal synthetic vascular graft for clinical application using tissue engineering or 3D printing are far from satisfactory. Therefore, we aimed to re-design the vascular graft with modified materials and 3D printing techniques and also demonstrated the improved applications of our new vascular graft clinically. We designed the 3D printed polyvinyl alcohol (PVA) templates according to the vessel size and shape, and these were dip-coated with salt-suspended thermoplastic polyurethane (TPU). Next, the core template was removed to obtain a customized porous TPU graft. The mechanical testing and cytotoxicity studies of the new synthetic 3D templated vascular grafts (3DT) were more appropriate compared with commercially available polytetrafluoroethylene (PTFE) grafts (ePTFE; standard graft, SG) for clinical use. Finally, we performed implantation of the 3DTs and SGs into the rat abdominal aorta as a patch technique. Four groups of the animal model (SG_7 days, SG_30 days, 3DT_7 days, and 3DT_30 days) were enrolled in this study. The abdominal aorta was surgically opened and sutured with SG or 3DT with 8/0 Prolene. The degree of endothelial cell activation, neovascularization, thrombus formation, calcification, inflammatory infiltrates, and fibrosis were analyzed histopathologically. There was significantly decreased thrombogenesis in the group treated with the 3DT for 30 days compared with the group treated with the SG for 7 and 30 days, and the 3DT for 7 days. In addition, the group treated with the 3DT for 30 days may also have shown increased postoperative endothelialization in the early stages. In conclusion, this study suggests the possibility of using the 3DT as an SG substitute in vascular surgery. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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24 pages, 14517 KiB  
Article
Microstructures and Mechanical Properties of Deposited Fe-8Cr-3V-2Mo-2W on SCM420 Substrate Using Directed Energy Deposition and Effect of Post-Heat Treatment
by Ye Eun Jeong, Jun Yeop Lee, Eun Kyung Lee and Do Sik Shim
Materials 2021, 14(5), 1231; https://doi.org/10.3390/ma14051231 - 5 Mar 2021
Cited by 7 | Viewed by 2848
Abstract
In this study, the Fe-8Cr-3V-2Mo-2W tool steel powder was deposited on the SCM420 substrate through the directed energy deposition (DED) process. This study focuses on the mechanical properties of the deposited Fe-8Cr-3V-2Mo-2W and the effect of heat treatment on it. The changes in [...] Read more.
In this study, the Fe-8Cr-3V-2Mo-2W tool steel powder was deposited on the SCM420 substrate through the directed energy deposition (DED) process. This study focuses on the mechanical properties of the deposited Fe-8Cr-3V-2Mo-2W and the effect of heat treatment on it. The changes in the microstructural characteristics of the deposited region due to heat treatment after deposition were observed. The influence of heat treatment on the mechanical properties was then analyzed accordingly and hence, the hardness, wear, impact and tensile tests were conducted on the deposited material. These properties were compared with those of the commercial tool steel powder M2-deposited material and the carburized specimen. In the deposited Fe-8Cr-3V-2Mo-2W layer, an increased martensite phase fraction was obtained through post-heat treatment and the amount of precipitated carbides was also increased. This increased the hardness from 48 to 62 HRc after heat treatment and the wear resistance was significantly improved as well. The amount of impact energy absorbed decreased from 11 J before heat treatment to 6 J after heat treatment, but the tensile strength significantly increased from 607 to 922 MPa. When compared with the M2-deposited surface, the Fe-8Cr-3V-2Mo-2W deposits had 3% lower surface hardness and 76% lower fracture toughness but exhibited 56% higher tensile strength. When compared with the carburized SCM420, the Fe-8Cr-3V-2Mo-2W deposits exhibited 3% higher surface hardness and wear resistance, 90% lower fracture toughness and 5% higher tensile strength. This study shows that surface hardening through DED can exhibit similar or superior mechanical properties when compared to carburizing. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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17 pages, 7826 KiB  
Article
A Study on Using the Additive Manufacturing Process for the Development of a Closed Pump Impeller for Mechanically Pumped Fluid Loop Systems
by Alexandra Adiaconitei, Ionut Sebastian Vintila, Radu Mihalache, Alexandru Paraschiv, Tiberius Frigioescu, Mihai Vladut and Laurent Pambaguian
Materials 2021, 14(4), 967; https://doi.org/10.3390/ma14040967 - 18 Feb 2021
Cited by 15 | Viewed by 5096
Abstract
The efficiency of a centrifugal pump for mechanical pump fluid loops, apart from the design, relies on the performance of the closed impeller which is linked to the manufacturing process in terms of dimensional accuracy and the surface quality. Therefore, the activities of [...] Read more.
The efficiency of a centrifugal pump for mechanical pump fluid loops, apart from the design, relies on the performance of the closed impeller which is linked to the manufacturing process in terms of dimensional accuracy and the surface quality. Therefore, the activities of this paper were focused on defining the manufacturing process of a closed impeller using the additive manufacturing technology for mechanically pumped fluid loop (MPFL) systems in space applications. Different building orientations were studied to fabricate three closed impellers using selective laser melting technology and were subjected to dimensional accuracy and surface quality evaluations in order to identify the optimal building orientation. The material used for the closed impeller is Inconel 625. The results showed that both geometrical stability and roughness were improved as the building orientation increased, however, the blade thickness presented small deviations, close to imposed values. Finishing processes for inaccessible areas presented significant results in terms of roughness, nevertheless, the process can be further improved. Abrasive flow machining (AFM) post-processing operations have been considered and the results show major improvements in surface quality. Thus, important steps were made towards the development of complex structural components, consequently increasing the technological readiness level of the additive manufacturing process for space applications. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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17 pages, 5022 KiB  
Article
Effects of Energy Parameters on Dimensional Accuracy When Joining Stainless-Steel Powders with Heterogeneous Metal Substrates
by Chunliang Kuo, Yuren Chen and Yupang Nien
Materials 2021, 14(2), 320; https://doi.org/10.3390/ma14020320 - 9 Jan 2021
Cited by 6 | Viewed by 1897
Abstract
This work presents some breakthroughs for obtaining high dimensional accuracy and reliable geometrical tolerance in the joining of stainless-steel powders with heterogeneous substrates. In the laser melting process, the interfacial energy fractions and forces acting at the solid–liquid surface of the melting powders [...] Read more.
This work presents some breakthroughs for obtaining high dimensional accuracy and reliable geometrical tolerance in the joining of stainless-steel powders with heterogeneous substrates. In the laser melting process, the interfacial energy fractions and forces acting at the solid–liquid surface of the melting powders can effectively vary their geometrical shapes and positions before they turn into the liquid phase. When the interfacial free energy is low, the melting powders are near molten, thus the successive volumetric changes can alter the layered geometry and positions. This assumption was validated by a powder-bedding additive manufacturing process to consolidate stainless-steel 316L powders (SLM 316L) on a thin heterogeneous stainless-steel substrate. Experiments were carried out to reveal the effects of the process parameters, such as laser power (100–200 W), exposure duration (50–100 µs) and point distance (35–70 µm) on the resulting material density and porosity and the corresponding dimensional variations. A fractional factorial design of experiment was proposed and the results of which were analyzed statistically using analysis of variances (ANOVA) to identify the influence of each operating factor. High energy densities are required to achieve materials of high density (7.71 g/cm3) or low porosity (3.15%), whereas low energy densities are preferable when the objective is dimensional accuracy (0.016 mm). Thermally induced deflections (~0.108 mm) in the heterogeneous metal substrate were analyzed using curvature plots. Thermally induced deformations can be attributed to volumetric energy density, scanning strategy, and the lay-up orientation. The parametric optimizations for increasing in dimensional accuracy (Z1: ~0.105 mm), or in material density (~7.71 g/cm3) were proven with high conversion rates of 88.2% and 96.4%, respectively, in validation runs. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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9 pages, 2810 KiB  
Article
Fabrication of SiC Sealing Cavity Structure for All-SiC Piezoresistive Pressure Sensor Applications
by Lihuan Zhao, Haiping Shang, Dahai Wang, Yang Liu, Baohua Tian and Weibing Wang
Materials 2021, 14(1), 128; https://doi.org/10.3390/ma14010128 - 30 Dec 2020
Cited by 3 | Viewed by 2141
Abstract
High hardness and corrosion resistance of SiC (silicon carbide) bulk materials have always been a difficult problem in the processing of an all-SiC piezoresistive pressure sensor. In this work, we demonstrated a SiC sealing cavity structure utilizing SiC shallow plasma-etched process (≤20 μm) [...] Read more.
High hardness and corrosion resistance of SiC (silicon carbide) bulk materials have always been a difficult problem in the processing of an all-SiC piezoresistive pressure sensor. In this work, we demonstrated a SiC sealing cavity structure utilizing SiC shallow plasma-etched process (≤20 μm) and SiC–SiC room temperature bonding technology. The SiC bonding interface was closely connected, and its average tensile strength could reach 6.71 MPa. In addition, through a rapid thermal annealing (RTA) experiment of 1 min and 10 mins in N2 atmosphere of 1000 °C, it was found that Si, C and O elements at the bonding interface were diffused, while the width of the intermediate interface layer was narrowed, and the tensile strength could remain stable. This SiC sealing cavity structure has important application value in the realization of an all-SiC piezoresistive pressure sensor. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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12 pages, 2594 KiB  
Article
A Post-Treatment Method to Enhance the Property of Aerosol Jet Printed Electric Circuit on 3D Printed Substrate
by Bing Wang, Haining Zhang, Joon Phil Choi, Seung Ki Moon, Byunghoon Lee and Jamyeong Koo
Materials 2020, 13(24), 5602; https://doi.org/10.3390/ma13245602 - 8 Dec 2020
Cited by 5 | Viewed by 2662
Abstract
Aerosol jet printing of electronic devices is increasingly attracting interest in recent years. However, low capability and high resistance are still limitations of the printed electronic devices. In this paper, we introduce a novel post-treatment method to achieve a high-performance electric circuit. The [...] Read more.
Aerosol jet printing of electronic devices is increasingly attracting interest in recent years. However, low capability and high resistance are still limitations of the printed electronic devices. In this paper, we introduce a novel post-treatment method to achieve a high-performance electric circuit. The electric circuit was printed with aerosol jet printing method on an ULTEM substrate. The ULTEM substrate was fabricated by the Fused Deposition Modelling method. After post-treatment, the electrical resistance of the printed electric circuit was changed from 236 mΩ to 47 mΩ and the electric property was enhanced. It was found that the reduction of electric resistance was caused by surface property changes. Different surface analysis methods including scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) were used to understand the effectiveness of the proposed method. The results showed that the microsurface structure remained the same original structure before and after treatment. It was found that the surface carbon concentration was significantly increased after treatment. Detailed analysis showed that the C-C bond increased obviously after treatment. The change of electrical resistance was found to be limited to the material’s surface. After polishing, the circuit resistance was changed back to its original value. As the electric circuit is the basic element of electric devices, the proposed method enables the fabrication of high performance devices such as capacitors, strain gauge, and other sensors, which has potential applications in many areas such as industrial, aerospace, and military usage. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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12 pages, 3286 KiB  
Article
3D-Printable Carbon Nanotubes-Based Composite for Flexible Piezoresistive Sensors
by Chaima Fekiri, Ho Chan Kim and In Hwan Lee
Materials 2020, 13(23), 5482; https://doi.org/10.3390/ma13235482 - 1 Dec 2020
Cited by 31 | Viewed by 4039
Abstract
The intersection between nanoscience and additive manufacturing technology has resulted in a new field of printable and flexible electronics. This interesting area of research tackles the challenges in the development of novel materials and fabrication techniques towards a wider range and improved design [...] Read more.
The intersection between nanoscience and additive manufacturing technology has resulted in a new field of printable and flexible electronics. This interesting area of research tackles the challenges in the development of novel materials and fabrication techniques towards a wider range and improved design of flexible electronic devices. This work presents the fabrication of a cost-effective and facile flexible piezoresistive pressure sensor using a 3D-printable carbon nanotube-based nanocomposite. The carbon nanotubes used for the development of the material are multi-walled carbon nanotubes (MWCNT) dispersed in polydimethylsiloxane (PDMS) prepolymer. The sensor was fabricated using the direct ink writing (DIW) technique (also referred to as robocasting). The MWCNT-PDMS composite was directly printed onto the polydimethylsiloxane substrate. The sensor response was then examined based on the resistance change to the applied load. The sensor exhibited high sensitivity (6.3 Ω/kPa) over a wide range of applied pressure (up to 1132 kPa); the highest observed measurement range for MWCNT-PDMS composite in previous work was 40 kPa. The formulated MWCNT-PDMS composite was also printed into high-resolution 3-dimensional shapes which maintained their form even after heat treatment process. The possibility to use 3D printing in the fabrication of flexible sensors allows design freedom and flexibility, and structural complexity with wide applications in wearable or implantable electronics for sport, automotive and biomedical fields. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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22 pages, 7063 KiB  
Article
Properties of Tool Steels Printed by Directed Energy Deposition Process on S45C Base Metal
by Sungjong Choi, Hochan Kim, Jihyun Sung, Dongmok Lee and Jongdock Seo
Materials 2020, 13(22), 5068; https://doi.org/10.3390/ma13225068 - 10 Nov 2020
Cited by 4 | Viewed by 2311
Abstract
We present a fundamental study on the development of trimming dies at room temperature for the hot-stamping process using directed energy deposition. Specimens of G and F materials were fabricated by machining 3D-printed blocks. The hardness of G-layered specimens was slightly higher than [...] Read more.
We present a fundamental study on the development of trimming dies at room temperature for the hot-stamping process using directed energy deposition. Specimens of G and F materials were fabricated by machining 3D-printed blocks. The hardness of G-layered specimens was slightly higher than that of F-layered specimens, reaching approximately 700 HV at the surface. The G-layered specimens consisted of columnar and equiaxed dendrites, whereas the F-layered specimens mainly consisted of equiaxed dendrites. Spherical pores were observed inside the layered cross section, whereas relatively large irregular-shaped cavities were observed in layered boundaries. The tensile strengths of the G-layered and F-layered specimens were approximately 1800 and 1650 MPa, respectively. During bonding strength tests on an area bonded with S45C base metal, a fracture occurred in one case because of the lack of fusion at the boundary, and the F-layered specimens showed a lower strength than the G-layered ones. During wear tests on a quenched 1.5 GPa-grade aluminized steel plate, the F-layered specimens showed lower wear loss. However, the G-layered specimens showed better wear resistance during wear tests on a 1.5 GPa-grade electrogalvanized steel plate. These findings serve as fundamental data for additive manufacturing processes using tool steels of high-strength materials with high melting points. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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19 pages, 7599 KiB  
Article
Estimation Method of Interpass Time for the Control of Temperature during a Directed Energy Deposition Process of a Ti–6Al–4V Planar Layer
by Bih-Lii Chua and Dong-Gyu Ahn
Materials 2020, 13(21), 4935; https://doi.org/10.3390/ma13214935 - 3 Nov 2020
Cited by 18 | Viewed by 2822
Abstract
Directed energy deposition (DED) provides a promising additive manufacturing method to fabricate and repair large metallic parts. However, it may suffer from excessive heat accumulation due to a high build rate, particularly during a wire feeding-type DED process. The implementation of interpass time [...] Read more.
Directed energy deposition (DED) provides a promising additive manufacturing method to fabricate and repair large metallic parts. However, it may suffer from excessive heat accumulation due to a high build rate, particularly during a wire feeding-type DED process. The implementation of interpass time in between two depositions of beads plays an important process role to passively control the interpass temperature. In this study, a method to estimate the proper interpass time using regression analysis from heat transfer finite element analysis is proposed for maintaining the interpass temperature during a wire feeding-type DED deposition of a planar layer. The overlapping beads of a planar layer are estimated using a polygonal-shaped bead profile in the finite element model. From the estimated proper interpass time, a selected proper interpass time scheme (PITS) is suggested for practical implementation. The selected PITS is applied in a thermo-mechanical finite element model to evaluate the temperature distribution and its effects on the depth of the melt pool, the depth of the heat-affected zone (HAZ), displacement, and residual stresses. By comparing the predicted results with those using a constant interpass time scheme (CITS), the selected PITS shows better control in reducing the depths of the melt pool and HAZ without severely inducing large displacement and residual stresses. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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15 pages, 5538 KiB  
Article
Ultrasonic Cavitation Erosion Behavior of AlCoCrxCuFe High Entropy Alloy Coatings Synthesized by Laser Cladding
by Danqing Yin, Guangbing Liang, Shuai Fan and Shanxin Li
Materials 2020, 13(18), 4067; https://doi.org/10.3390/ma13184067 - 13 Sep 2020
Cited by 11 | Viewed by 2743
Abstract
Cavitation corrosion resistant coatings are an excellent solution to the cavitation corrosion problem. High entropy alloys provide a new possibility for cavitation resistant coatings due to their excellent comprehensive performance. Laser cladding was employed to synthesize AlCoCrxCuFe (x represents the [...] Read more.
Cavitation corrosion resistant coatings are an excellent solution to the cavitation corrosion problem. High entropy alloys provide a new possibility for cavitation resistant coatings due to their excellent comprehensive performance. Laser cladding was employed to synthesize AlCoCrxCuFe (x represents the Cr concentration, x = 0.5, 1.0, 1.5, 2.0) high entropy alloy coatings (HECs) on AISI 304 steel. The phase transformation, microstructure, micro-mechanical properties, and cavitation erosion performance of HECs were studied. Results showed that AlCoCrxCuFe HECs were composed of BCC and FCC duplex phase. The microstructure of HECs showed a typical dendritic structure. The composition segregation of interdendrite structures was observed. Cavitation erosion resistance represented by 20 h volume loss was decreased with the increase in Cr content. AlCoCrxCuFe HECs with the lowest chromium content (AlCoCr0.5CuFe) showed the best cavitation erosion resistance among all samples. The cavitation resistance of AlCoCrxCuFe HECs has good correlation with the mechanical parameter Hn3/Er2 (Hn is nanohardness, Er is elastic modulus) and phase formation parameter δ (δ is atomic radius difference). The surface after 20 h of cavitation erosion testing exposed the dendritic structure of BCC phase, which was caused by the destruction of the interdendrite structure by cavitation impact. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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13 pages, 4365 KiB  
Article
Deposition of Durable Micro Copper Patterns into Glass by Combining Laser-Induced Backside Wet Etching and Laser-Induced Chemical Liquid Phase Deposition Methods
by Jae Min Seo, Kui-Kam Kwon, Ki Young Song, Chong Nam Chu and Sung-Hoon Ahn
Materials 2020, 13(13), 2977; https://doi.org/10.3390/ma13132977 - 3 Jul 2020
Cited by 19 | Viewed by 4799
Abstract
Glass is a well-known non-conductive material that has many useful properties, and considerable research has been conducted into making circuits on glass. Many deposition techniques have been studied, and laser-induced chemical liquid phase deposition (LCLD) is a well-known and cost-effective method for rapid [...] Read more.
Glass is a well-known non-conductive material that has many useful properties, and considerable research has been conducted into making circuits on glass. Many deposition techniques have been studied, and laser-induced chemical liquid phase deposition (LCLD) is a well-known and cost-effective method for rapid prototyping of copper deposition on glass. However, the deposition results from the LCLD method on the surface of glass, which shows an issue in its detachment from the substrates because of the relatively low adhesion between deposited copper and the nontreated glass surface. This problem undermines the usability of deposited glass in industrial applications. In this study, the laser-induced backside wet etching (LIBWE) method was performed as a preceding process to fabricate microchannels, which were filled with copper by LCLD. Additional durable copper wire was produced as a result of the enhanced adhesion between the glass and the deposited copper. The adhesion was enhanced by a rough surface and metal layer, which are characteristics of LIBWE machining. Furthermore, the proposed method is expected to broaden the use of deposited glass in industrial applications, such as in stacked or covered multilayer structures with built-in copper wires, because the inserted copper can be physically protected by the microstructures. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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12 pages, 6056 KiB  
Article
Directly Printed Low-Cost Nanoparticle Sensor for Vibration Measurement during Milling Process
by Soo-Hong Min, Tae Hun Lee, Gil-Yong Lee, Daniel Zontar, Christian Brecher and Sung-Hoon Ahn
Materials 2020, 13(13), 2920; https://doi.org/10.3390/ma13132920 - 29 Jun 2020
Cited by 6 | Viewed by 2681
Abstract
A real-time, accurate, and reliable process monitoring is a basic and crucial enabler of intelligent manufacturing operation and digital twin applications. In this study, we represent a novel vibration measurement method for workpiece during the milling process using a low-cost nanoparticle vibration sensor. [...] Read more.
A real-time, accurate, and reliable process monitoring is a basic and crucial enabler of intelligent manufacturing operation and digital twin applications. In this study, we represent a novel vibration measurement method for workpiece during the milling process using a low-cost nanoparticle vibration sensor. We directly printed the vibration sensor based on silver nanoparticles positioned onto a polyimide substrate using an aerodynamically-focused nanomaterials printing system, which is a direct printing technique for inorganic nanomaterials positioned onto a flexible substrate. Since it does not require any post-process such as chemical etching and heat treatment, a highly sensitive vibration sensor composed of a microscale porous structure was fabricated at a cost of several cents each. Furthermore, accurate and reliable vibration data was obtained by simple and direct attachment to a workpiece. In this study, we discussed the performance of vibration measurement of a fabricated sensor in comparison to a commercial vibration sensor. Using frequency and power spectrum analysis of obtained data, we directly measured the vibration of workpiece during the milling process, according to a process parameter. Lastly, we applied a fabricated sensor for the digital twins of turbine blade manufacturing in which vibration greatly affects the quality of the product to predict the process defects in real-time. Full article
(This article belongs to the Special Issue Additive Manufacturing Technologies and Its Applications Using Advanced Materials)
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