A novel ultrasonic non-destructive testing methodology to monitor fatigue crack growth in compact tension specimens

Abstract

Detection and evaluation of fatigue cracks in structural materials are extremely important for life prediction analysis as part of the structural integrity procedure. In this article, we present a novel ultrasonic measurement methodology, based on the diffraction of elastic waves at the crack tips, to monitor the fatigue crack growth near the threshold regime in compact tension specimens at different load ratios. The diffraction phenomenon of ultrasonic waves from the crack tip is demonstrated using a finite element 2D wave propagation simulation. The applicability of this methodology has also been contrasted with that of the conventional direct current potential drop method. In addition, the crack morphology obtained in the ultrasonic c-scan imaging showed a variation in the crack propagation plane as a function of the cyclic loading parameters. The results suggest that this novel methodology is sensitive to fatigue cracks and can form the basis of in situ ultrasonic-based crack measurements in metallic and non-metallic materials.

Fatigue Damage Evaluation of Aviation Aluminum Alloy Based on Strain Monitoring

“…However, there is limited research on the online monitoring of fatigue damage, with most studies being theoretical. In the field of acoustic NDT, Saju T. Abraham [27] monitored fatigue crack extension by diffraction of elastic waves at the crack tip and compared it with the conventional DC potential drop method. T. Vie [28] analyzed the acoustic emission signals during tension and fatigue of 7075-T6 aluminum alloy with various coating combinations to assess the damage and its mechanisms during fatigue testing.…”