Repeated Stressing and Crystalline State of Annealed Steel

Abstract

The action of repeated loading, especially of repeated compression for the crystalline state of 0.41% carbon steel was investigated by X-ray. As a result it was established that the crystal fragmentation occurs when the maximum stress exceeds the lower yield point of that material but has no direct relation with fatigue failure. In the case of alternate tension and compression with equal amplitude (mean stress equals zero), the specimens break down far below the yield point, of course, but is not necessarily preceeded by the crystal fragmentation. Then, what is the true nature of fatigue of metals is our problem. According to the authors' view, failure begins when the accumulation of crystal distorsion exceeds a certain limit proper to the individual grain.