Teruaki Mikuriya

Effect of Biaxial Stresses on the Threshold of Small Surface Crack Propagation

In order to investigate the effect of biaxial stresses due to the combination of plane bending and cyclic torsion on the threshold of mode I small surface crack propagation, the relationship between the threshold stress and crack length under various biaxial stress ratios C was examined using a circular shaft made of carbon steel. The threshold stress intensity factor is constant above some crack length in each C, but becomes lower with the decrease in C. The length of the slipped regionγp at the crack tip on the threshold of crack propagation is nearly constant regardless of C. Therefore, if the threshold curve of crack propagation in C = 0 is determined experimentally, the threshold curves in other C can be deduced from the relationship betweenγp and C.