Measuring acoustic nonlinearity parameter using collinear wave mixing

This study introduces a new acoustic nonlinearity parameter β T. It is shown that β T is associated with the interaction between a longitudinal wave and a shear wave in isotropic elastic solids with quadratic nonlinearity. Experimental measurements are conducted to demonstrate that the collinear wave mixing technique is capable of measuring β T nondestructively. Further, it is shown that β T is well-correlated with the plastic deformation in Al-6061 alloys. These results indicate that collinear wave mixing is a promising method for nondestructive assessment of plastic deformation, and possibly, fatigue damage in metallic materials.