GROWTH OF SHEAR LIPS IN SURFACE CRACKED SHAFTS SUBJECTED TO FATIGUE LOADING

Shear lip growth was monitored on the fracture surfaces of notched and plain surface cracked shafts subjected to constant amplitude axial fatigue loads. Results showed that shear lip growth in the plain specimens was slightly slower than predictions based on equations derived from through cracked plate data. This is in contrast to shear lip growth in the notched shafts, which was much slower than predicted. The reduced rate of shear lip growth in the shaft geometries is attributed to the decreasing stress intensity factor along the surface crack front and the tensile circumferential stress in the notch shafts. It was also seen that the formation of shear lips had a significant effect on the shape of the crack front. Overall specimen fatigue life, however, was relatively unaffected by shear lip growth.