Measuring the damage factor of materials with the thin-walled cylinder torsion test and the low-cycle fatigue test

Abstract

We have derived the expression of the damage factor, D = 1−( G ̃ /G) , by applying Lemaitre's strain equivalent hypothesis to the pure shear case, and used it as the theoretical basis for measuring D with the thin-walled cylinder torsion test. According to the damage strain energy release rate Y and the Mises criterion, we have obtained the relation between D 1 c and D 2 c , 1−D 1c 1−D 2c = √[ 3 2 (1 + v)] Here, we have performed the torsion test on steel No. 35 and steel No. 45, and measured the value of D 2 c ; D 2 c is then converted into D 1 c . We also have measured D c of steel No. 45 in the low-cycle fatigue test with controlled strain amplitude, and compared the test result of steel No. 45.