A fractional dual-phase-lag generalized thermoelastic model of ultrashort pulse laser ablation with variable thermal material properties, vaporization and plasma shielding

Abstract

The ultrashort pulse laser is widely used in micro scale non-contact machining of nonmetallic materials because of its high energy density, short pulse duration and small heat affected zone. Ablation is the main material removal mechanism in ultrashort pulse laser processing. This motivates us to establish the fractional dual-phase-lag (FDPL) generalized thermoelastic ablation model and investigate the transient responses of silicon ablated by the picosecond pulse laser. The temperature-dependent material properties, surface recession velocity and plasma shielding effect on the subsequent laser beam have been paid more attention. In calculation, the temperature distributions at the surface melting moment and plasma formation moment are taken as the initial conditions of the next Phases. The coupled governing equations containing fractional order parameter, lag times as well as spatial nonlocal parameter are formulated and solved by Laplace transform together with its numerical inversion. The temperature, displacement and stress with different laser intensity, pulse duration, fractional order parameter, lag time ratio as well as times are obtained and illustrated graphically. The accurate thermoelastic coupling description of silicon processed by the ultrashort pulse laser is obtained, which provides a reliable theoretical guide for high-quality laser processing of nonmetallic materials.