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Ip THEORY OF FRACTURE MECHANICS FOR FATIGUE LOADING

VIJAY UKADGAONKER (IIT BOMBAY)

Crack initiation and growth: methods, applications, and challenges

Wed 1:30 - 2:50

Barus-Holley 161

In two dimensional stress analyses, for crack initiation, the strain energy consists of dilation and distortion strain energies. Within elastic-plastic boundary the distortion strain energy remains constant. It is the dilatational strain energy that varies over elastic-plastic boundary. Where ever it is maximum, the crack initiates in that direction and the magnitude is directly proportional to Ip witch is the difference of square of first stress invariant and two times second stress invariant. Some two dimensional problems of static fracture mechanics are solved to check this theory, The Ip theory is extended to dynamic fatigue loading on CT specimen, which gives not only magnitude but also direction of the crack growth, unlike the famous Paris law, which gives only magnitude. Ip theory is also extended to fatigue loading at elevated temperatures for maraging steels of various grades.