A Computationai Constitutive Modei for Giass Subjected to Large Strains, High Strain Rates and High PressuresThis article presents a computational constitutive model for f^la.ss subjected to large strains, high strain rates and high pressures. The model has similarities to a previottsly developed model for brittle materials by Johnson. Holmquist and Beissel (JHB model), hut thete ate significatit differences. This new glass model provides a material sttength that is depetulent on the location and/or condition of the matetial. Ptovisions are made for the .sttength to be depetidetit on whether it is in the intetior, on the sutface (different sutface finishes can be accommodated), adjacent to failed material, or if it is failed. The intact and failed sttengths are also dependetit on the pressure atid the strain täte. Tlietmal softening, damage softening, time-dependent softening, and the effect of the third invariant are also inchided. The shear modttlus can be constant or variable. The pressure-vohtme relationship includes permanent densification and bulking. Damage is accumulated based on plastic strain, ptessure and strain täte. Simple (sitigle-element) e.xamples are presented to illusttate the capabilities of the model. Compttted results for more complex ballistic impact configttrations are also ptesented atid compared to expetitnental data.
This article presents an analysis of the response of boron carbide (B4C) to severe loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine and/or estimate constants for the JH-2 constitutive model for brittle materials. Because B4C is a very strong material, it is not always possible to determine the constants explicitly. Instead they must sometimes be inferred from the limited experimental data that are available. The process of determining constants provides insight into the constitutive behavior for some loading conditions, but it also raises questions regarding the response under other loading conditions. Several Lagrangian finite element and Eulerian finite difference computations are provided to illustrate responses for a variety of impact and penetration problems.
This article presents an analysis of the response of silicon carbide to high velocity impact. This includes a wide range of loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine constants for the Johnson–Holmquist constitutive model for brittle materials (JH-1). It is possible to directly determine the strength and pressure response of the intact material from test data in the literature. After the ceramic has failed, however, there are not adequate experimental data to directly determine the response of the failed material. Instead, the response is inferred from a comparison of computational results to ballistic penetration test results. After the constants have been obtained for the JH-1 model, a wide range of computational results are compared to experimental data in the literature. Generally, the computational results are in good agreement with the experimental results. Included are computational results that model interface defeat, which occurs when a high velocity projectile impacts a ceramic target and then dwells on the surface of the ceramic with no significant penetration.
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