The Evolution of Damage in Prenotched Steel Specimens Deformed at High Strain Rates
We study dynamic thermomechanical deformations of a prenotched steel specimen deformed in plane strain tension at nominal strain-rates of 1000/s, 5000/s and 20000/s. The thermomechanical response of the porous material is modeled by the modified Gurson’s flow potential; the modification being due to Tvergaard and Needleman. The effective stress is assumed to depend upon the plastic strain, plastic strain-rate and temperature through the Johnson-Cook relation. Voids are presumed to grow due to plastic dilation and nucleate when the plastic strain reaches a critical value. The dependence of Young’s modulus, bulk modulus and thermal conductivity on porosity is accounted for. It is found that both the initial porosity and the nominal strain-rate influence noticeably when and from where the damage, defined as the porosity attaining a critical value, begins to evolve.
KeywordsShear Band Dead Zone Initial Porosity Adiabatic Shear Band Viscoplastic Material
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