Material microstructure effects on ultrasonic waves under simple shear and pure shear

In this paper, the longitudinal and transverse wave velocities propagating into aluminum alloy A6061 under simple shear and pure shear were studied experimentally. Compared with the same velocity change tendencies of transverse wave under simple shear and pure shear, longitudinal wave velocity showed different change tendencies under both shear states, regardless of the same shear strain states in two cases. Furthermore, the measured longitudinal wave velocity changes under pure shear state were apparently categorized into two types according to different material surface states, i.e., simply decreasing change tendency at polished surface state, and chaotic change tendencies at unpolished material surface state. Consequently, the finite element analysis was carried out to investigate the deformation-induced microstructure effects on ultrasonic waves under plastic deformation. The analyzed results indicate that the transverse wave velocity changes depend on textures mainly, whereas the longitudinal wave velocity shows a sensitive response to the point defects.