Investigation into the cause of failure of pinion shaft-a case study

Investigation into the cause of failure of a pinion shaft of a grinding unit, which failed after only one day's service, was carried out. Little evidence of usual progressive failure was observed from the fracture surface. Ingot defects like unwelded pipe and blow holes were observed at the failed portion and the most probable cause of failure was analysed to be due to these pre-existing defects in the material. (Mr. B.N. Das, Scientist and Mr. B.N. Ghose, Junior Scientific Assistant, National Metallurgical Laboratory, Jamshedpur)