High‐temperature, pressure‐shear plate impact experiments were conducted to investigate the rate‐controlling mechanisms of the plastic response of high‐purity aluminum at high strain rates (106s−1) and at temperatures approaching melt. Since the melting temperature of aluminum is pressure dependent, and a typical pressure‐shear plate impact experiment subjects the sample to large pressures (2–7 GPa), a pressure‐release type experiment was used to reduce the pressure in order to measure the shearing resistance at temperatures up to 95% of the current melting temperature. The measured shearing resistance was remarkably large (50 MPa at a shear strain of 2.5) for temperatures this near melt. Numerical simulations conducted using a version of the Nemat‐Nasser/Isaacs [1] constitutive equation, modified to model the mechanism of geometric softening, appear to capture adequately the hardening/softening behavior observed experimentally.

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