The effect of microstructure and fatigue on the acoustoelastic response of aerospace materials

摘要: This thesis presents work relating to the measurement of nonlinear acoustoelastic response several materials with respect microstructure and fatigue life. The measures coefficient a material. During normal usage components are subject stresses that while not sufficient cause fracture fatigue, gradually weakening component. Linear ultrasonic methods have been shown be poor at detecting fatigue. However, there is evidence accumulation damage gives material elastic can probed by ultrasound. A potential technique monitor produced monitoring changes in techniques. Several nonlinearity using acoustic waves proposed. In this system collinear mixing developed. By measuring velocity change probe wave due induced stress from pump wave, measure obtained. laser ultrasound techniques we gain benefits high spatial temporal resolution. important when investigating as affects material. Single point measurements taken. polycrystalline found vary location. developed variation coefficient. relationship between underlying found. used samples they fatigued. larger proportion (9-30%) than linear (0.5-0.6%). Spatial indicated complex implications further required observed discussed.