Abstract
A replica method is commonly used to detect a crack initiation and propagation for rotating bending fatigue cracks. But in this method, a length of crack on the surface can be detected at only the certain cycles, and can't detect the crack initiation accurately or observe the change of fatigue crack length continuously. In this report, small fatigue cracks are detected by measuring the displacement at a notch root of specimens during fatigue test with a laser displacement meter. As a result, we can observe the propagation of fatigue cracks by measuring the amount of displacement change in real time.
