Irreproducibility of acoustic emission under cyclic irradiation of solids by an infrared laser pulse

Acoustic emission (AE) caused by a stress wave in solid material samples with various thermophysical properties, i.e., copper, aluminum, and glass upon exposure to СO₂ laser pulses is studied. It is found that the general AE picture (the AE signal arrival time, its amplitude, and others) is not reproduced during repeated experiments following one after another, which indicates irreversible local changes occurred in the material structure. The effect of the critical material energy density on the AE pattern during the laser exposure is demonstrated.