Laser power dependence of mechanoluminescence in metals

Mechanoluminescence (ML) glow is produced on the back side when the front of a metal sample is irradiated with infrared Nd:YAG laser pulses. An incident laser beam with a power density below the plasma-flare onset threshold causes a rise in temperature in the studied metal. As the incident laser power density increases, the intensity of the ML glow signal also increases. On the basis of the laser power density-induced temperature, an expression is derived for the temperature-induced thermal stress. An expression is derived for the correlation between thermal stress and laser power density, which indicates that the temperature-induced thermal stress is directly related to the incident laser power density. In the region of plastic deformation, temperature-induced thermal stress is related to the strain and, consequently, to the emitted ML intensity. Finally, an expression is derived for the laser power dependence of the ML intensity, and good agreement is found between the theoretical and experimental results. Copyright © 2016 John Wiley & Sons, Ltd.