Abstract
The objective of this research is to analyze and evaluate the dynamic flow curve of metals under impact loading at both high strain rate (.epsilon.=1/h dh/dt > 10$\^$3/m/s/m) and large strain (.epsilon.=In h/h$\_$0/ > 1.0). A test method for dynamic compression of metal disc is described. The velocity of the striker face and the force on the anvil are measured during the impact period. From these primitive data the axial stress, strain, and strain rate of the disc are obtained. The Strain rate is determined by the striker velocity divided by the specimen height. This gives a slightly increasing strain rate over most of the deformation period. Strain rates of 100 to 10,000 per second are achieved. Attainable final strains are 150%. A discussion of several problem areas is presented. The friction on the specimen surfaces, the determination of the frictional coefficient, the influence of the specimen geometry (h$\_$0//d$\_$0/ ratio) on the friction effect, the lock-up condition for a given configuration, the friction correction factor, and the evaluation of several lubricants are given. The flow function(stress verus strain) is dependent on the material condition(e.g., prior cold work), specimen geometry, strain rate, and temperature.
본 연구에서는 충격하중하에서 고변형도 .epsilon.=ln(h/h$_{o}$ )＞1.0, 고변형도율 (.epsilon.＞$10^{3}$m/s/m)로 변형하는 재료에 대하여 응력, 변형도, 변형도율사이의 함수관 계를 유도하고, 다음과 같은 현상들을 규명하였다. (1) 고변형도율에서 응력, 변형 도, 변형도율사이의 함수관계식 유도. (2) 압축하중시 시편과 접촉부재사이의 접촉면 에서 발생하는 마찰영향의 조사. (3) 유동응력과 시편의 기하학적 형상사이의 관계식 유도. (4) 압축하중시 재료의 제동현상(lock-up phenomena)의 해석.