scholarly journals Effect of Cell Wall Ductility and Toughness on Compressive Response and Strain Rate Sensitivity of Aluminium Foam

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Alexandra Byakova ◽  
Svyatoslav Gnyloskurenko ◽  
Andrey Vlasov ◽  
Nikolay Semenov ◽  
Yan Yevych ◽  
...  
Keyword(s):  
Cell Wall ◽  
Strain Rate ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Melt Processing ◽  
Wall Material ◽  
Static Compression ◽  
Quasi Static Compression ◽  
Al Foams

The study presents the effect of cell wall ductility and toughness on the compressive behaviour of closed-cell Al foams under static and dynamic loading and localised deformation by indentation. Two kinds of Al alloys including relatively ductile AlSiMg alloy and high-strength AlZnMg alloy, which comprises a great amount of brittle eutectic domains, were used as matrix materials. Both kinds of Al foams were fabricated via newly developed melt processing using the CaCO3-foaming agent without Ca additive. Mechanical behaviour of Al foams under quasi-static compression and indentation was examined and compared with that performed under dynamic loading using direct impact tests. Characteristic events revealed in deformation patterns of Al foams at quasi-static compression were also monitored with the CCD camera. Significant differences in stress-strain response and strain rate sensitivity of Al foams arose from the difference in the microstructure, and hence, ductility and toughness of the cell wall material were investigated and discussed.

Optimization of constitutive model parameters for simulation of polystyrene concrete subjected to impact

2017 ◽  
Vol 9 (2) ◽  
pp. 121-140 ◽  
Author(s):  
Tae Kwang Yoo ◽  
Tong Qiu
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Material Model ◽  
Drop Impact ◽  
Model Parameters ◽  
Compression Tests ◽  
Static Compression ◽  
Impact Tests ◽  
Quasi Static Compression

This article presents the results of a series of experimental testing and numerical modeling studies to optimize the parameters of a constitutive material model to accurately simulate the behavior of polystyrene crushable concrete during impact loading using LS-DYNA. Quasi-static compression tests and confined drop impact tests were conducted. To model the quasi-static compression tests, the response surface methodology was used to optimize Poisson’s ratio and friction angle in the pseudo-tensor model in LS-DYNA. Using the optimized model parameters, the simulated compression stress versus strain relationship showed an excellent agreement with those from the compression tests. To model the confined drop impact tests, the strain rate sensitivity parameter in LS-DYNA was optimized by comparing the drop impact simulations at different strain rate sensitivity values with the drop impact tests. This study suggests that the pseudo-tensor material model is potentially suitable for modeling crushable concrete. Although the optimized constitutive model parameters are specific for the polystyrene concrete mix used in this study, similar approach can be used to optimize model parameters for other polystyrene concrete mixes.

scholarly journals The strain-rate sensitivity of irreversible deformation of the metallic multilayer composite GLARE

2019 ◽  
Vol 487 (5) ◽  
pp. 507-510
Author(s):  
N. S. Selyutina ◽  
Yu. V. Petrov ◽  
V. Parameswaran ◽  
A. P. Sharma
Keyword(s):  
Strain Rate ◽  
Sheet Metal ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Irreversible Deformation ◽  
Multilayer Composite ◽  
Relaxation Model ◽  
Al 2024

Responses of the aluminum multilayer composite to dynamic loading are described by the relaxation model of plasticity. Relations between the rate sensitivity of the multilayer composite, parameters of the dynamic loading and the strain rate sensitivity of its components are established. It is shown that estimates of the rate sensitivity turned out to be higher for GLARE composite in comparison to the rate sensitivity estimates for its component of Al 2024-T3 sheet metal.

scholarly journals Influence on strain-rate history effects on the development of necking instabilities under dynamic loading conditions

2021 ◽  
Author(s):  
Nicolas Jacques ◽  
Jose Rodriguez-Martinez
Keyword(s):  
Strain Rate ◽  
Dynamic Loading ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
Neck Formation ◽  
History Effects ◽  
Instantaneous Strain ◽  
Instantaneous Strain Rate Sensitivity ◽  
Dynamic Loading Conditions

The present paper is devoted to the analysis of strain-rate history effects on neck formation under dynamic loading. For materials presenting strain-rate history effects, two different strain-rate sensitivities should be distinguished: the instantaneous strain-rate sensitivity and the work-hardening strain-rate sensitivity. We have analysed the relative contributions of these two kinds of strain-rate sensitivities to neck retardation for two different configurations: a bar under impact tension and a dynamically expanding ring. For this purpose, we have developed finite element models and, for the second configuration, an analytical model based on the linear stability analysis. The obtained results show that strain-rate history effects have a significant influence on the onset and development of necking. The reason of thisphenomenon is that, contrary to the instantaneous strain-rate sensitivity, the work-hardening strain-rate sensitivity does not contribute to delay the neck formation.

scholarly journals Effect of the Strain Rate and Fiber Direction on the Dynamic Mechanical Properties of Beech Wood

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 881 ◽  
Author(s):  
Shumeng Pang ◽  
Yingjing Liang ◽  
Weijun Tao ◽  
Yijie Liu ◽  
Shi Huan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Beech Wood ◽  
Rate Sensitivity ◽  
Dynamic Mechanical Properties ◽  
Fiber Direction ◽  
Compression Tests ◽  
Static Compression ◽  
Dynamic Mechanical

As a macroscopically orthotropic material, beech wood has different mechanical properties along the fiber direction and the direction perpendicular to the fiber direction, presenting a complicated strain rate sensitivity under impact or blast loadings. To understand the effect of the strain rate on the mechanical properties of beech wood, dynamic compression tests were conducted for the strain rate range of 800 s−1–2000 s−1, and quasi-static compression tests for obtaining the static mechanical properties of beech wood were also performed for comparison. The fiber direction effect on the mechanical properties was also analyzed, considering two loading directions: one perpendicular to the beech fiber direction and the other parallel to the beech fiber direction. The results show that beech wood for both loading directions has a significant strain rate sensitivity, and the mechanical properties of beech wood along the fiber direction are superior to those along the direction perpendicular to the fiber direction. An analysis of the macrostructures and microstructures of beech specimens is also presented to illustrate the failure mechanisms. The beech wood, as a natural protective material, has special dynamic mechanical properties in the aspect of transverse isotropy. This research provides a theoretical basis for application in protective structures.

scholarly journals Compressive Behaviour of Additively Manufactured Periodical Re-Entrant Tetrakaidecahedral Lattices at Low and High Strain-Rates

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1196
Author(s):  
Michaela Neuhäuserová ◽  
Tomáš Fíla ◽  
Petr Koudelka ◽  
Jan Falta ◽  
Václav Rada ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Speed ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Deformation Behaviour ◽  
Rate Sensitivity ◽  
Image Correlation ◽  
Strain Rates ◽  
Static Compression

Compressive deformation behaviour of additively manufactured lattice structures based on re-entrant tetrakaidecahedral unit-cell geometry were experimentally investigated under quasi-static and dynamic loading conditions. Specimens of four different structures formed by three-dimensional periodical assembly of selected unit-cells were produced by a laser powder bed fusion technique from a powdered austenitic stainless steel SS316L. Quasi-static compression as well as dynamic tests using split Hopkinson pressure bar (SHPB) apparatus at two strain-rates were conducted to evaluate the expected strain-rate sensitivity of the fundamental mechanical response of the structures. To evaluate the experiments, particularly the displacement fields of the deforming lattices, optical observation of the specimens using a high-resolution camera (quasi-static loading) and two synchronised high-speed cameras (SHPB experiments) was employed. An in-house digital image correlation algorithm was used in order to evaluate the anticipated auxetic nature of the investigated lattices. It was found that neither of the investigated structures exhibited auxetic behaviour although strain-rate sensitivity of the stress–strain characteristics was clearly identified for the majority of structures.

scholarly journals Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 339
Author(s):  
Xiang Wang ◽  
Zhi Qiang Ren ◽  
Wei Xiong ◽  
Si Nan Liu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Strain Rate Sensitivity ◽  
Critical Role ◽  
Rate Sensitivity ◽  
Confined Compression ◽  
Negative Strain Rate Sensitivity ◽  
Cast Specimen ◽  
Structure Heterogeneity

The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.

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