Abstract
Resonance frequency is an important parameter in the ultrasonic fatigue testing. This study investigated the effects of the resonance frequency by measuring stress amplitude and edge displacement under various resonance frequency conditions. The resonance frequency of the specimens varies according to the specimen length. When the resonance frequencies are equal between the specimen and the testing machine, errors of stress amplitude are negligible. However, if there are differences, the errors are increased. In these cases, the errors of edge displacement are increased as well. The errors of stress amplitude are therefore reduced by re-calculating the stress amplitude based on the measured edge displacement. This re-calculation is very close to feedback control of the edge displacement. A way to minimize the errors is however to match the resonance frequencies between the specimen and the testing machine. In this case, the feedback control is not always necessary.
