Short-Time Thermal Effects on Thermomechanical Response Caused By Pulsed Lasers

摘要

An ultrafast thermoelasticity model is proposed to analyze the heat transport and thermomechanical phenomena in metal films heated by femtosecond laser pulses. It covers 1) the dual-hyperbolic two-step heating process in thermal transport, 2) the hot-electron blast effect in momentum transfer, 3) the coupling effect between lattice temperature and strain rate, 4) the thermal stress relaxation effect, and 5) the volumetric absorption of laser beam energy. The coupled transient thermoelasticity equations are solved with a nonconventional finite difference scheme. Numerical analysis is performed for gold films under the conditions of uniaxial strain and uniaxial stress, respectively. The effects of the heat-flux relaxations in electrons and the lattice, thermal stress relaxation, hot-electron blast force, and thermal-mechanical coupling are investigated.