Development of In-plane Biaxial Compression Test Method for Thin Sheet and Investigation of SD Effect under Biaxial Stress Condition

Abstract

The accuracy of the finite element simulation (FE simulation) of press forming has improved as a result of sophisticated material modelling using data of the various experiments such as uniaxial compression, biaxial tension, and in-plane cyclic loading tests. However, the biaxial compression test of sheet material has never been reported lowing to the difficulty in buckling suppression, and differences between material behavior under biaxial tension and that under biaxial compression have not yet been discussed. In this paper, the biaxial compression test of sheet material using special tools to suppress buckling and a specimen shape that leads to uniform deformation in the measurement area is proposed mainly on the basis of FE simulation. The special tool has a urethane plate where the tool come into contact with the measurement area of the specimen to prevent damage of the strain gauges. Absolute values of compressive stresses during plastic work measured by the biaxial compression test were larger than tensile stresses during the same plastic work measured by the biaxial tension test. Similar results observed in uniaxial tension and compression tests are known as the strength differential (SD) effect.