OBSERVATIONS MADE AT THE ROOT OF A NOTCH IN IRON FATIGUED IN BENDING,

摘要

A piece of Armco iron wire was notched to a depth of .030in.,polished and etched,and then cycled by reversed plane bending. Plastic replicas were made of the notch root after the completion of each tensile stroke. A long trough or crack,about 20microns deep and 20microns wide was observed to develop during 7-1/4cycles. Various effects of cyclic plastic flow were observed in detail at and near the notch root,including the formation of slip bands and subsequent fissuring in the slip bands,and the sinking of surface material to form troughs during cycling. (Author)