An ultrasonic method for dynamic monitoring of fatigue crack initiation and growth.

摘要: Attached ultrasonic sensors can detect changes caused by crack initiation and growth if the wave path is directed through area of critical formation. Dynamics cracks opening closing under load cause nonlinear modulation received signals, enabling small to be detected stationary sensors. A methodology presented based upon behavior signals versus applied monitor formation originating from fastener holes. Shear angle beam transducers operating in transmission mode are mounted on either side hole such that transmitted travels expected cracking. Time shift linear with respect load, well explained due strain combined speed acoustoelasticity. During subsequent situ monitoring unknown loads, measured time flight used estimate energy as a function basis for detection. Results low cycle fatigue tests several aluminum specimens illustrate efficacy method both determining growth.