Fracture of acrankshaft on a 150-ton press after operating 35 years

摘要

The fracture of the 6-inch diameter crankshaft of a 150-ton mechanical press, which was being used to form automotive wheel components from 1/4-inch thick steel stock, caused the main gear, weighing about 1,700 lbs., to fall into the manufacturing area severely injuring one of the machine operators. By comparing the ailure load calculated from the fracture toughness of the shaft material to the loads allowable in an infinite life design of a component such as the crankshaft, it was concluded that the fatigue crack growth and final failure occurred under the normally expected cyclic loads. The shaft failed as the result of fatigue crack growth which originated at intergranular crakcs that developed in an area that had been inadvertently subjected to local intense heating and quenching.