Thermoelastic Wave Induced by Pulsed Laser Heating

Abstract

In this work, a generalized solution for the thermoelastic plane wave in a semi-infinite solid induced by pulsed laser heating is formulated in the form of Fourier series. The solution takes into account the non-Fourier effect in heat conduction and the coupling effect between temperature and strain rate, which play significant roles in ultra-short pulsed laser heating. Based on this solution, calculations are conducted to study stress waves induced by different laser parameters. It is found that with the same maximum surface temperature increase, a shorter pulsed laser induces a much stronger stress wave in a solid. The non-Fourier effect causes a higher surface temperature increase, but a weaker stress wave. The surface displacement accompanying thermal expansion shows a time delay to the laser pulse in femtosecond laser heating. On the contrary, surface displacement and heating occur simultaneously in nano- and picosecond laser heating. In femtosecond laser heating, results show that the coupling effect attenuates the stress wave and extends the duration of the stress wave. This may explain the minimal damage in ultra-short laser materials processing.