Online remaining fatigue life estimation of curved steel connection using nonlinear ultrasonic modulation

Abstract

An online monitoring technique was developed to continuously estimate the remaining fatigue life of a padeye. Piezoceramic ultrasonic transducers were surface-mounted on the padeye for ultrasound generation and sensing. A fatigue index is defined and calculated from the experimentally measured nonlinear ultrasonic modulation components. The fatigue index is also derived as a simple power function of the loading cycles based on the Nazarov-Sutin and Paris-Erdogan theories. Then, the remaining fatigue life is estimated and continuously updated by fitting the power function to the ultrasonic modulation data accumulated up to the present time.