Numerical Study of the Critical Impact Velocity in Shear. Appendix Number 1.
Final technical rept. for period ending 1996,
METZ UNIV (FRANCE) LAB OF PHYSICS AND MECHANICS OF MATERIALS
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Localization of plastic deformation in the form of shear bands is a very common failure mode in many materials. At high strain rates plastic deformation becomes nearly adiabatic which leads to the local heating of a material and as a consequence to the softening and formation of the adiabatic shear bands. At impact velocities of the order of 100 ms the Critical Impact Velocity CIV in shear occurs. The superposition of adiabatic shear banding and adiabatic plastic waves in shear is the main interest in this report. A numerical study of impact shearing of a layer has been performed by the FE code ABAQUS. It was intended to verify available experimental results for VAR 4340 steel 52 HRC, obtained by direct impact on the Modified Double Shear specimen, 1. In particular, the numerical study has been focussed on the effect of the impact velocity including the phenomenon of the Critical Impact Velocity in shear. An infinite thin layer fixed at one end and with a small geometrical imperfection in the middle of its height was considered. The layer was submitted in the other end to different shear velocities, from quasi-static to impact, up to 180 ms. Two modes of shear deformation of the layer have been found in the first mode all deformation concentrates in the middle of the layer, and in the second near the surface where the shear velocity is imposed. The CIV could be defined as a transition between those two modes. It has been shown that impact velocities higher than the CIV leads to a substantial reduction of the localization energy. All FE calculations have been performed with constitutive relations specially developed to reflect behavior of VAR 4340 steel. Thermal coupling, strain hardening and rate sensitivity are accounted for.
- Properties of Metals and Alloys
- Numerical Mathematics