On measuring the dynamic elastic modulus for metallic materials using stress wave loading techniques

摘要

Metallic materials are mostly rate dependent in mechanical behavior, but their elastic modulus under high strain rate is hard to measure accurately. In this paper, two methodologies are proposed based on stress wave theory in hope of accurate measurement for metallic materials, for example Ti6Al4V alloy. One is based on the one-dimension stress wave propagation in a long Ti6Al4V bar, and the elastic modulus under a high strain rate is obtained from the calculated stress wave speed. The other technique is to utilize the integrated Hopkinson pressure bar made of Ti6Al4V material. The obtained elastic moduli from these methods are compared and analyzed, and the results are consistent with each other. The numerical simulations with cylindrical and dogbone-shaped specimens are conducted to show the influence of bar indentation on measurement accuracy. An alternative method is introduced based on the vertical split Hopkinson pressure bar, which can extend the integrated Hopkinson pressure bar method for most metallic materials with small bulk. The verification experiments are also conducted. Finally, the limiting strain rate is estimated for potential measurement problems.