중 변형률속도 영역에서 차체 강판의 인장/압축 경화 거동에 관한 연구

Abstract

The tension/compression hardening behavior is important in sheet metal forming processes because of complicated loading paths. Experimental methods to measure the tension/ compression behavior have not considered the effect of the strain rate although the strain rate is related to the hardening behavior of sheet metal. The tension/compression tests need to be conducted considering the strain rate to acquire accurate hardening behavior. This paper deals with an experimental technique to measure the tension/compression behavior of sheet metal at strain rates from 0.001 s-1 to 50 s-1 for real sheet metal forming. A new clamping device was developed to prevent a sheet specimen from buckling under compression loading condition. Jig systems to impose pre-strain and reverse loading were also developed for high speed material testing machine. Tension/compression tests have been conducted at various strain rates for SPCC and DP590 with pre-strain of 10%. Hardening behavior under the tension or compression loading condition was compared to each other at severe strain rates.