Visible sensor for yield stress caused by cyclic loading

Yield point is one of the most important mechanical properties of materials, however, there have not been any rules for obtaining the yield point caused by cyclic loading. Also in the case of analyzing the fatigue phenomena, the mechanical properties obtained by tension testing are normally used. It is widely known that when a tensile load is applied to a plane carbon steel specimen, Lueders' lines corresponding to yield stress occur on the surface. We decided to utilize Lueders' lines, in order to obtain the yield point under cyclic loading, therefore we investigated the state of their surface. Then it was clarified that we can utilize Lueders' lines in order to detect the yield point caused by cyclic loading. And that is used to detect the failure place of structural members. This method is very easy, namely only to have a smooth finish at the fixed portion, we can observe an occurrence of the striped pattern by the naked eye.