Monitoring of failure locations in ductile members

The prevention of fracture in a structure is one of the most important problems of mechanical engineering. The fracture of a structure occurs at mechanical failure locations. It would be possible to prevent fracture if it were possible to discern failure locations. One possible method of detection might be to make use of the visible properties of the material. Yield point elongation is accompanied by the formation of visible bands known as Lueders' lines or stretcher strains. These Lueders' lines result not only from monotonic loading, but also from cyclic loading. Utilization of the appearance conditions of Lueders' lines enables the naked eye to detect yielding failure locations of ductile machine members. The appearance of those striped patterns indicates where a fracture is about to occur. It is possible to monitor the position where fracture may occur, over time, if changing striped patterns can be detected by digital signals. It is possible to detect the failure locations of a structure from a remote location. Change of striped patterns indicating maximum stress during cyclic loading is examined. Direct observation was made of change in surface conditions at the vicinity of a hole and round corners where cyclic loading was applied.