Research

19 pages, 59154 KiB

Open AccessArticle

Investigations on the Mechanical Response of Gradient Lattice Structures Manufactured via SLM

by Judyta Sienkiewicz, Paweł Płatek, Fengchun Jiang, Xiaojing Sun and Alexis Rusinek

Metals 2020, 10(2), 213; https://doi.org/10.3390/met10020213 - 03 Feb 2020

Cited by 46 | Viewed by 7669

The main aim of the paper is to evaluate the mechanical behavior or lattice specimens subjected to quasi-static and dynamic compression tests. Both regular and three different variants of SS 316L lattice structures with gradually changed topologies (discrete, increase and decrease) have been [...] Read more.

The main aim of the paper is to evaluate the mechanical behavior or lattice specimens subjected to quasi-static and dynamic compression tests. Both regular and three different variants of SS 316L lattice structures with gradually changed topologies (discrete, increase and decrease) have been successfully designed and additively manufactured with the use of the selective laser melting technique. The fabricated structures were subjected to geometrical quality control, microstructure analysis, phase characterization and compression tests under quasi-static and dynamic loading conditions. The mismatch between dimensions in the designed and produced lattices was noticed. It generally results from the adopted technique of the manufacturing process. The microstructure and phase composition were in good agreement with typical ones after the additive manufacturing of stainless steel. Moreover, the relationship between the structure relative density and its energy absorption capacity has been defined. The value of the maximum deformation energy depends on the adopted gradient topology and reaches the highest value for a gradually decreased topology, which also indicates the highest relative density. However, the highest rate of densification was observed for a gradually increasing topology. In addition, the results show that the gradient topology of the lattice structure affects the global deformation under the loading. Both, static and dynamic loading resulted in both barrel- and waisted-shaped deformation for lattices with an increasing and a decreasing gradient, respectively. Lattice specimens with a gradually changed topology indicate specific mechanical properties, which make them attractive in terms of energy absorption applications. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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27 pages, 7763 KiB

Open AccessFeature PaperArticle

Optimum Strength Distribution for Structures with Metallic Dampers Subjected to Seismic Loading

by Jesús Donaire-Ávila and Amadeo Benavent-Climent

Metals 2020, 10(1), 127; https://doi.org/10.3390/met10010127 - 15 Jan 2020

Cited by 7 | Viewed by 2546

Abstract

A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly [...] Read more.

A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly normalized by the upward weight of the building and expressed by a shear force coefficient α_i. The cumulative plastic strain energy in a given story i can be normalized by the product of its lateral strength and yield displacement, and expressed by a plastic deformation ratio η_i. The distribution α_i/α₁ that makes η_i equal in all stories is called the optimum yield-shear force distribution. It constitutes a major aim of design; a second aim is to achieve similar ductility demand in all stories. This paper proposes a new approach for deriving the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers. It is shown, both numerically and experimentally, that structures designed with the proposed distribution fulfil the expected response in terms of both damage distribution and inter-story drift demand. Moreover, a comparison with other distributions described in the literature serves to underscore the advantages of the proposed approach. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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24 pages, 60334 KiB

Open AccessArticle

Blast-Induced Compression of a Thin-Walled Aluminum Honeycomb Structure—Experiment and Modeling

by Magda Stanczak, Teresa Fras, Ludovic Blanc, Piotr Pawlowski and Alexis Rusinek

Metals 2019, 9(12), 1350; https://doi.org/10.3390/met9121350 - 15 Dec 2019

Cited by 20 | Viewed by 5049

Abstract

The presented discussion concerns the behavior of a thin-walled hexagonal aluminum honeycomb structure subjected to blast loading. The shock wave affecting the structure is generated by detonation of the C4 charge in an explosive-driven shock tube (EDST). The EDST set-up is an instrumented [...] Read more.

The presented discussion concerns the behavior of a thin-walled hexagonal aluminum honeycomb structure subjected to blast loading. The shock wave affecting the structure is generated by detonation of the C4 charge in an explosive-driven shock tube (EDST). The EDST set-up is an instrumented device that makes it possible to study blast effects in more stable and repeatable conditions than those obtained in a free-air detonation. The formation of folds characteristic of a honeycomb deformation in the axial compression distributes the initial loading over a time period, which is considered as an efficient method of energy dissipation. The test configuration is modeled in the Ls-Dyna explicit code, which enables analysis of the mechanisms of energy absorption that accompanies structural deformation under a blast loading. The conclusions reached in the performed experimental and numerical investigation can be applied to the modeling and optimization of cellular structures used to mitigate blast loadings. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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12 pages, 4814 KiB

Open AccessArticle

Experimental and Numerical Analysis of Conical Projectile Impact on Inconel 718 Plates

by Marcos Rodríguez-Millán, Antonio Díaz-Álvarez, Richard Bernier, María Henar Miguélez and José Antonio Loya

Metals 2019, 9(6), 638; https://doi.org/10.3390/met9060638 - 02 Jun 2019

Cited by 8 | Viewed by 3153

Abstract

This paper analyses the impact behavior of Inconel 718 through experimental and numerical approach. Different conical projectiles were tested in order to obtain the ballistic curves and failure mechanisms. A three-dimensional (3D) numerical model corresponding to the experimental tests was developed using the [...] Read more.

This paper analyses the impact behavior of Inconel 718 through experimental and numerical approach. Different conical projectiles were tested in order to obtain the ballistic curves and failure mechanisms. A three-dimensional (3D) numerical model corresponding to the experimental tests was developed using the Johnson–Cook constitutive model. The experimental data (residual velocities, global, and local perforation mechanisms) were successfully predicted with the numerical simulations. The influence of the projectile’s nose angle was found to be important when designing ballistic protections. The projectile with the narrowest angle, 40°, developed a ballistic limit approximately 10 m/s lower than the projectile with a 72° nose. The use of double-nose projectile for the same nose angle, 72°, led to a ballistic limit 12 m/s lower than that obtained for the single nose. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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19 pages, 15941 KiB

Open AccessArticle

Close Range Explosive Loading on Steel Column in the Framework of Anisotropic Viscoplasticity

by Piotr Witold Sielicki, Wojciech Sumelka and Tomasz Łodygowski

Metals 2019, 9(4), 454; https://doi.org/10.3390/met9040454 - 17 Apr 2019

Cited by 12 | Viewed by 3617

Abstract

The research was based on data obtained from experimental studies and aims in the challenge of mapping these results by a mathematical (phenomenological) model. The field experiments were performed on an H-section steel column supported by a reinforced concrete foundation and subjected to [...] Read more.

The research was based on data obtained from experimental studies and aims in the challenge of mapping these results by a mathematical (phenomenological) model. The field experiments were performed on an H-section steel column supported by a reinforced concrete foundation and subjected to a close-in explosion. Numerical studies were carried out using Abaqus/Explicit code. The user subroutine VUMAT for metallic obstacle was also implemented, together with a coupled Eulerian–Lagrangian approach. The steel column failure recorded during real field tests versus computational results was examined and compared. It was crucial that, from the computational point of view, the obstacle reflected the generalized thermo-elasto-viscoplastic (GTEV) behavior of Perzyna’s type, including an anisotropic measure of damage. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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17 pages, 8688 KiB

Open AccessArticle

The Evaluation of the Fracture Surface in the AW-6060 T6 Aluminium Alloy under a Wide Range of Loads

by Marcin Chybiński, Łukasz Polus, Maria Ratajczak and Piotr W. Sielicki

Metals 2019, 9(3), 324; https://doi.org/10.3390/met9030324 - 13 Mar 2019

Cited by 15 | Viewed by 3561

Abstract

The present study focused on the behaviour of the AW-6060 aluminium alloy in peak temper condition T6 under a wide range of loads: tensile loading, projectile and explosion. The alloy is used as a structural component of civil engineering structures exposed to static [...] Read more.

The present study focused on the behaviour of the AW-6060 aluminium alloy in peak temper condition T6 under a wide range of loads: tensile loading, projectile and explosion. The alloy is used as a structural component of civil engineering structures exposed to static or dynamic loads. Therefore, it was crucial to determine the material’s behaviour at low and intermediate rates of deformation. Despite the fact that the evaluation of the strain rate sensitivity of the AW-6060 aluminium alloy has already been discussed in literature, the authors of this paper wished to further investigate this topic. They conducted tensile tests and confirmed the thesis that the AW-6060 T6 aluminium alloy has low strain rate sensitivity at room temperature. In addition, the fracture surfaces subjected to different loading (tensile loading, projectile and explosion) were investigated and compared using a scanning electron microscope, because the authors of this paper were trying to develop a new methodology for predicting how samples had been loaded before failure occurred based on scanning electron microscopy (SEM) micrographs. Projectile and explosion tests were performed mainly for the SEM observation of the fracture surfaces. These tests were unconventional and they represent the originality of this research. It was found that the type of loading had an impact on the fracture surface. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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22 pages, 14313 KiB

Open AccessArticle

Identification of the Quasi-Static and Dynamic Behaviour of Projectile-Core Steel by Using Shear-Compression Specimens

by Yannick Duplan, Dominique Saletti and Pascal Forquin

Metals 2019, 9(2), 216; https://doi.org/10.3390/met9020216 - 12 Feb 2019

Cited by 3 | Viewed by 3781

Abstract

Armour-Piercing (AP) projectiles constitute a major threat to be considered for the design of bi-layer-armour configurations constructed using a ceramic front plate backed with a composite/metal layer. When they are not made of tungsten-carbide the cores of these projectiles are made of hard [...] Read more.

Armour-Piercing (AP) projectiles constitute a major threat to be considered for the design of bi-layer-armour configurations constructed using a ceramic front plate backed with a composite/metal layer. When they are not made of tungsten-carbide the cores of these projectiles are made of hard steel, and are the main part that defines the penetration performance of the projectile. However, due to specific testing difficulties, the dynamic behaviour of these high-strength steel AP projectiles has not been investigated in sufficient detail. In this study, a detailed experimental investigation of the dynamic behaviour of the steel used for the steel core of 7.62 mm BZ-type AP projectiles was analysed through the use of Shear-Compression Specimens (SCS). In this study, results from both quasi-static and dynamic experiments were examined. The data processing method employed was set and validated based on numerical simulations. Both quasi-static and dynamic SCS experiments were done with the steel tested which clearly indicated the steel cores exhibit a very high elastic limit, little strain-hardening, and very little strain-rate sensitivity despite the wide range of strain-rates considered. This experimental characterisation paves the way to the numerical modelling for the analysis of ballistic impact of 7.62 mm AP projectile against lightweight armour configurations. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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22 pages, 9202 KiB

Open AccessArticle

Material Behavior Description for a Large Range of Strain Rates from Low to High Temperatures: Application to High Strength Steel

by Pierre Simon, Yaël Demarty, Alexis Rusinek and George Z. Voyiadjis

Metals 2018, 8(10), 795; https://doi.org/10.3390/met8100795 - 03 Oct 2018

Cited by 19 | Viewed by 2953

Abstract

Current needs in the design and optimization of complex protective structures lead to the development of more accurate numerical modelling of impact loadings. The aim of developing such a tool is to be able to predict the protection performance of structures using fewer [...] Read more.

Current needs in the design and optimization of complex protective structures lead to the development of more accurate numerical modelling of impact loadings. The aim of developing such a tool is to be able to predict the protection performance of structures using fewer experiments. Considering only the numerical approach, the most important issue to have a reliable simulation is to focus on the material behavior description in terms of constitutive relations and failure model for high strain rates, large field of temperatures and complex stress states. In this context, the present study deals with the dynamic thermo-mechanical behavior of a high strength steel (HSS) close to the Mars^® 190 (Industeel France, Le Creusot, France). For the considered application, the material can undergo both quasi-static and dynamic loadings. Thus, the studied strain rate range is varying from 10⁻³–10⁴ s⁻¹. Due to the fast loading time, the local temperature increase during dynamic loading induces a thermal softening. The temperature sensitivity has been studied up to 473 K under quasi-static and dynamic conditions. Low temperature measurements (lower than the room temperature) are also reported in term of

σ - {ε |}_{\dot{ε}, T}

curves. Experimental results are then used to identify the parameters of several constitutive relations, such as the model developed initially by Johnson and Cook; Voyiadjis and Abed; and Rusinek and Klepaczko respectively termed Johnson–Cook (JC), Voyiadjis–Abed (VA), and Rusinek–Klepaczko (RK). Finally, comparisons between experimental results and model predictions are reported and compared. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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14 pages, 25695 KiB

Open AccessArticle

Monitoring Steel Bolted Joints during a Monotonic Tensile Test Using Linear and Nonlinear Lamb Wave Methods: A Feasibility Study

by Magdalena Rucka

Metals 2018, 8(9), 683; https://doi.org/10.3390/met8090683 - 31 Aug 2018

Cited by 12 | Viewed by 3393

Abstract

The structural integrity of steel bolted joints may be compromised due to excessive loading. Therefore, condition assessment and the detection of potential defects before they cause a failure have become a major issue. The paper is focused on the condition monitoring of a [...] Read more.

The structural integrity of steel bolted joints may be compromised due to excessive loading. Therefore, condition assessment and the detection of potential defects before they cause a failure have become a major issue. The paper is focused on the condition monitoring of a bolted lap joint subjected to progressive degradation in a tensile test. The inspection used Lamb waves propagated through the overlap area. Wave propagation signals were registered automatically by means of piezoelectric transducers. Two damage indices were defined based on linear and nonlinear features of Lamb waves. The use of a network of piezoelectric transducers and the analysis of multiple signals instead of single ones was proved to effectively monitor the state of the bolted joint. The obtained results showed that the method enabled to detect selected stages of the degradation process and to characterize the reduction of the contact area between the plates in the overlap area. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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8 pages, 2663 KiB

Open AccessArticle

Nanoscale Twinned Ti-44Al-4Nb-1.5Mo-0.007Y Alloy Promoted by High Temperature Compression with High Strain Rate

by Wenqi Guo, Haitao Jiang, Shiwei Tian and Guihua Zhang

Metals 2018, 8(8), 619; https://doi.org/10.3390/met8080619 - 07 Aug 2018

Cited by 5 | Viewed by 3194

Abstract

In order to investigate the dynamic mechanical behavior of TiAl alloys and promote their application in the aerospace industry, uniaxial compression of Ti-44Al-4Nb-1.5Mo-0.007Y (at %) alloy was conducted at a temperature range from 25 to 400 °C with a strain rate of 2000 [...] Read more.

In order to investigate the dynamic mechanical behavior of TiAl alloys and promote their application in the aerospace industry, uniaxial compression of Ti-44Al-4Nb-1.5Mo-0.007Y (at %) alloy was conducted at a temperature range from 25 to 400 °C with a strain rate of 2000 s^‒1. Twinning is found to be the dominating deformation mechanism of the γ phase at all temperatures, and the addition of Nb and Mo has a chemical impact on the alloy and reduces the stacking fault energy of the γ phase. The decreased stacking fault energy increases the twinnability; thus, the deformation is dominated by twinning, which increases the dynamic strength of the alloy. With the temperature increasing from 25 to 400 °C, the average spacing of twins in the γ phase increases from 32.4 ± 2.9 to 88.1 ± 9.2 nm. The increased temperature impedes the continuous movement of partial dislocations and finally results in an increased twin spacing in the γ phase. Full article

(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)

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