抄録
The present paper is concerned with a problem of longitudinal plastic waves in a bar subjected to tensile impact. The effect of the variation of impact velocity on the propagation plastic waves and the formation of strain plateau in the strain distribution is discussed experimentally and theoretically. Impact tensile tests of copper specimens were carried out by an impact testing apparatus using a falling weight. The plastic strain distribution of the specimen was measured and the time history of plastic waves at various stations along the specimen was observed, together with the variation of impact velocity during impact. Theoretical calculation was performed by using Malvern's strain-rate dependent theory, taking account of the attenuation of impact velocity.
The results obtained are summarized as follows:
(1) The experimental results showed that the strain distribution along the specimen decreased with the increase of the distance from the impact end and no strain plateau at neighborhood of the impact end appeared.
(2) The theoretical results under the condition of decreasing impact velocity predicted also no strain plateau and almost agreed with the experimental results.
(3) The formation of strain plateau may be limited to the case of a constant impact velocity, though it is related to the strain-rate dependent nature of material, the impact velocity and the duration of impact time.
