Abstract
The dynamic stress-strain curves of annealed aluminum alloy and solder alloy were measured by a more convenient impact test than the Hopkinson bar one. The plastic strain rate was expressed by an exponential function of the overstress, and the constant parameters in the function were estimated from the experimental relation between the overstress and the plastic strain rate.
For the purpose of investigating the strain-rate effect on the flexual stiffness of the rate-sensitive material under a dynamic load, the elasto-viscoplastic behavior of an initially curved bar under longitudinal impact with a rigid hammer was analyzed numerically using the above-mentioned constant parameters. For the reason of difficulty in obtaining a closed form of solution due to geometric and material nonlinearity, the solid bar was replaced by a lumped-parameter model. The strain-rate dependent solution was compared with the strain-rate independent one in order to investigate the strain-rate effects on the residual strain and the residual deformation. As the result of this numerical analysis, it was shown that the impact caused the smaller residual strain (or deformation) in the rate-sensitive materials than in the rate-insensitive ones.
