Nonlinear photoacoustic response on mechanical stresses in the vicinity of a hole in a D16 aluminum-alloy plate

Characteristics of a photoacoustic signal depending on mechanical stresses in the vicinity of a hole in a D16 aluminum-alloy plate have been analyzed. A new nonlinear photoacoustic effect was found that consists in the occurrence of a nonlinear component in the photoacoustic signal depending on mechanical stresses in the vicinity of a hole. This dependence is detected in the signal on the main modulation frequency of laser radiation. We have proposed a theoretical description of the detected effect of thermoelastic generation of ultrasound in stressed metals based on taking into account the thermal impact of laser radiation on their electron subsystem.