스패클 패턴을 이용한 변형률속도와 하중방향에 따른 R-값의 측정

Abstract

This paper introduces a method to measure r-value from the speckled pattern with respect to the strain rate and loading direction. The r-values were calculated with high speed camera by analyzing the deformation history during the static and dynamic tensile tests. A digital image processing Matlab code for tracking of selected points was constructed to measure the longitudinal and transversal strain from the speckled pattern, which was made by spraying black paints on the white paint coated tensile specimen. Using suggested method, r-values of 590TRIP 1.2t and 7800P 1.0t were measured with the variation of the strain rate (0.001 /s~ 100 /s) and loading direction (rolling direction, diagonal direction, and transverse direction).