A Computational Constitutive Model for Glass Subjected to Large Strains, High Strain Rates and High Pressures

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Timothy J. Holmquist ◽  
Gordon R. Johnson
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
High Pressures ◽  
High Strain ◽  
Material Strength ◽  
Large Strains ◽  
Single Element ◽  
Strain Rates ◽  
High Strain Rates ◽  
Third Invariant

This article presents a computational constitutive model for glass subjected to large strains, high strain rates and high pressures. The model has similarities to a previously developed model for brittle materials by Johnson, Holmquist and Beissel (JHB model), but there are significant differences. This new glass model provides a material strength that is dependent on the location and/or condition of the material. Provisions are made for the strength to be dependent on whether it is in the interior, on the surface (different surface finishes can be accommodated), adjacent to failed material, or if it is failed. The intact and failed strengths are also dependent on the pressure and the strain rate. Thermal softening, damage softening, time-dependent softening, and the effect of the third invariant are also included. The shear modulus can be constant or variable. The pressure-volume relationship includes permanent densification and bulking. Damage is accumulated based on plastic strain, pressure and strain rate. Simple (single-element) examples are presented to illustrate the capabilities of the model. Computed results for more complex ballistic impact configurations are also presented and compared to experimental data.

scholarly journals The Freely Expanding Ring Test—A Test to Determine Material Strength at High Strain Rates

1986 ◽  
Vol 108 (4) ◽  
pp. 335-339 ◽  
Author(s):  
R. H. Warnes ◽  
R. R. Karpp ◽  
P. S. Follansbee
Keyword(s):  
High Strain ◽  
Time History ◽  
Ring Test ◽  
Test Material ◽  
Material Strength ◽  
Large Strains ◽  
Strain Rates ◽  
High Strain Rates ◽  
Strain Behavior ◽  
Thin Ring

The freely expanding ring test (ERT) is a conceptually simple test for determining the stress-strain behavior of materials at large strains and at high strain rates. This test is conducted by placing a thin ring of test material in a state of uniform radial expansion and then measuring its subsequent velocity-time history. The ring is usually propelled by a high explosive driving system. The test has not become popular in the materials property community, however, because there has been some concern about how the launching of the ring sample with an explosively generated shock wave might affect the properties to be measured. To determine the suitability of the ERT for these fundamental investigations, a series of experiments was performed on a carefully controlled material—oxygen-free electronic fully annealed copper. Recovered ring samples were analyzed and the change in hardness determined. Comparisons of the ERT data with that from Hopkinson bar tests at strain rates of about 5 × 103 s−1 indicate that the shock-induced hardness is approximately equivalent to a strain hardening of 5 percent. ERT data on this material at strain rates up to 2.3 × 104 s−1 are presented.

Response of aluminum nitride (including a phase change) to large strains, high strain rates, and high pressures

2003 ◽  
Vol 94 (3) ◽  
pp. 1639-1646 ◽  
Author(s):  
Gordon R. Johnson ◽  
Timothy J. Holmquist ◽  
Stephen R. Beissel
Keyword(s):  
Aluminum Nitride ◽  
Phase Change ◽  
High Pressures ◽  
High Strain ◽  
Large Strains ◽  
Strain Rates ◽  
High Strain Rates

scholarly journals An improved computational constitutive model for glass

2017 ◽  
Vol 375 (2085) ◽  
pp. 20160182 ◽  
Author(s):  
Timothy J. Holmquist ◽  
Gordon R. Johnson ◽  
Charles A. Gerlach
Keyword(s):  
High Pressures ◽  
High Strain ◽  
Experimental Testing ◽  
Laboratory Data ◽  
Experimental Results ◽  
Large Strains ◽  
Strain Rates ◽  
High Strain Rates ◽  
Surface Strength ◽  
Improved Model

In 2011, Holmquist and Johnson presented a model for glass subjected to large strains, high strain rates and high pressures. It was later shown that this model produced solutions that were severely mesh dependent, converging to a solution that was much too strong. This article presents an improved model for glass that uses a new approach to represent the interior and surface strength that is significantly less mesh dependent. This new formulation allows for the laboratory data to be accurately represented (including the high tensile strength observed in plate-impact spall experiments) and produces converged solutions that are in good agreement with ballistic data. The model also includes two new features: one that decouples the damage model from the strength model, providing more flexibility in defining the onset of permanent deformation; the other provides for a variable shear modulus that is dependent on the pressure. This article presents a review of the original model, a description of the improved model and a comparison of computed and experimental results for several sets of ballistic data. Of special interest are computed and experimental results for two impacts onto a single target, and the ability to compute the damage velocity in agreement with experiment data. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’.

A Dynamic Mechanical Analysis of T2 Copper at High Strain Rates

2019 ◽  
Vol 812 ◽  
pp. 38-44
Author(s):  
Shuai Chen ◽  
Wen Bin Li ◽  
Xiao Ming Wang ◽  
Wen Jin Yao
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Pure Copper ◽  
Dislocation Slip ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Shpb Test

This work compares the pure copper (T2 copper)’s stress-strain relationship at different strain rates in the uni-axial tension test and Split Hopkinson Pressure Bar (SHPB) test. Small samples were utilized in the high strain rate SHPB test in which the accuracy was modified by numerical simulation. The experimental results showed that the T2 copper’s yield strength at high strain rates largely outweighed the quasi static yield strength. The flow stress in the stress-strain curves at different strain rates appeared to be divergent and increased with the increase in strain rates, showing great strain strengthening and strain rate hardening effects. Metallographic observation showed that the microstructure of T2 copper changed from equiaxed grains to twins and the interaction between the dislocation slip zone grain boundary and twins promoted the super plasticity distortion in T2 copper.

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