Analysis of an unusual crankshaft failure

A crankshaft cracked in a strange manner when test running was performed for only 20 min. Four cracks were found on the edge of the oil hole. Using mechanical analysis, microstructure and metallurgy the reason of this event has been revealed. Force of friction caused by improper crankshaft repair and assembling is main factor of the failure. Why friction occurs, how the crack initiates and expands and what the process of failure is were studied.