Detection of Crack Initiation by Observations of Free Surface Condition

A simple method to detect crack initiation is presented. By polishing the surface of carbon steel structure properly and using the Luders bands and orange peel as indicators for damage, it is possible to predict crack initiation with the naked eye. The initiation of the Luders bands is the yellow light of the crack initiation, for instance, in the traffic signal, and orange peel is the red light. The relationship between the observed surface condition and the cyclic stress-strain characteristics is discussed.