Prediction of Fatigue Crack Propagation Path under Combined Torsional and Axial Loading
Keisuke TANAKA,Hiroki TAKAHASHI,Takuya KATO and Yoshiaki AKINIWA
Abstract:A simulation of fatigue crack propagation from a hole or crack under combined axial and torsional loading was conducted on the basis of the maximum tangential stress criterion for determining the crack path. The simulation results of the crack propagation path were compared with the experimental results obtained from fatigue tests by using thin-walled tubular specimens made of a medium-carbon steel. Fatigue cracks are nucleated at the position of the maximum of the amplitude of the tangential stress around the hole, and propagated straight away from the hole. The path of fatigue crack propagation from a hole or a crack followed the direction perpendicular to the maximum of the range of the tangential stress, Ds*q max, near the crack tip calculated from the stress intensity ranges by considering the contact of crack faces near the minimum load. The crack path predicted from the Ds*q max criterion was very close to that calculated from the maximum of the total range of the tangential stress, Dsq max, calculated by neglecting the crack face contact. The superposition of static mode II shear loading changes slightly the propagation path of a crack propagating under uniaxial tension compression. This deviation is caused by the generation of cyclic mode II component due to the zigzag shape of a fatigue crack. Key Words:Fatigue, Crack propagation, Combined stress, Fracture mechanics, Crack propagation path, Crack face contact, Body force method