Acoustoelastic Lamb wave analysis in thin plates

Fabrication processes, such as, shot peening, bending, and rolling can induce residual stresses in metals that will impact product performance and cause phenomena such as cracking and corrosion. To better manage residual stress tools are needed to map their distribution. Ultrasonic methods can be used as a good tool for residual stress detection, and this approach is non-destructive and costs are modest. Methods which utilize longitudinal critically refracted (LCR) waves are receiving increased attention and it can be used on thick material. However, there have only been a limited number of studies which consider the acoustoelastic effect for thin plate materials which generate Lamb waves. This paper reports a study in which a numerical model is used to investigate the Lamb wave dispersion curves under loading that induce stresses. The effects of stress on various Lamb modes are discussed and those which appear to be most sensitive are identified. It is found that when the stress´s direction is normal to the direction of wave propagation in a 1 mm thick aluminum plate the A0 mode is the most sensitive to the applied stress.