A new experimental method for measuring life time and crack growth of materials under multi-stage and random loadings

The experimental equipment and method of operation of a special computer-controlled fatigue testing machine is described. This resonance testing machine, operating at ultrasonic frequencies (20 kHz), performs one-step, multistage, and random fatigue tests with the aid of a computerized control system in very short testing times. Differences between this method and testing procedure at conventional frequencies are pointed out. However, it is emphasized that the high frequency tests have practical merit aside from lower energy cost and testing times. Initial results of two-stage fatigue experiments are reported.