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 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.

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

Granular flow of an advanced ceramic under ultra-high strain rates and high pressures

2020 ◽  
Vol 143 ◽  
pp. 104031 ◽  
Author(s):  
Xiangyu Sun ◽  
Ankur Chauhan ◽  
Debjoy D. Mallick ◽  
Andrew L. Tonge ◽  
James W. McCauley ◽  
...  
Keyword(s):  
Granular Flow ◽  
High Pressures ◽  
High Strain ◽  
Strain Rates ◽  
High Strain Rates ◽  
Advanced Ceramic

scholarly journals Use of simulated experiments for material characterization of brittle materials subjected to high strain rate dynamic tension

2017 ◽  
Vol 375 (2085) ◽  
pp. 20160168 ◽  
Author(s):  
Bratislav Lukić ◽  
Dominique Saletti ◽  
Pascal Forquin
Keyword(s):  
High Speed ◽  
Dynamic Range ◽  
High Strain ◽  
Experimental Testing ◽  
Brittle Materials ◽  
Strain Rates ◽  
High Strain Rates ◽  
Extrinsic Factors ◽  
Full Field ◽  
Ultra High Speed

Rapid progress in ultra-high-speed imaging has allowed material properties to be studied at high strain rates by applying full-field measurements and inverse identification methods. Nevertheless, the sensitivity of these techniques still requires a better understanding, since various extrinsic factors present during an actual experiment make it difficult to separate different sources of errors that can significantly affect the quality of the identified results. This study presents a methodology using simulated experiments to investigate the accuracy of the so-called spalling technique (used to study tensile properties of concrete subjected to high strain rates) by numerically simulating the entire identification process. The experimental technique uses the virtual fields method and the grid method. The methodology consists of reproducing the recording process of an ultra-high-speed camera by generating sequences of synthetically deformed images of a sample surface, which are then analysed using the standard tools. The investigation of the uncertainty of the identified parameters, such as Young's modulus along with the stress–strain constitutive response, is addressed by introducing the most significant user-dependent parameters (i.e. acquisition speed, camera dynamic range, grid sampling, blurring), proving that the used technique can be an effective tool for error investigation. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’.

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