Abstract
An ultrafast thermoelasticity based on a hyperbolic two-step heat conduction model with electron-phonon interaction is applied to investigate the thermomechanical response of five immense homogeneous, isotropic gold films (20 nm, 100 nm, 200 nm, 500 nm, and 2 μm) impacted under femtosecond laser pulses by using finite element method (FEM). Finite element governing equations are established and solved in the time domain directly. The results, including electron temperature, lattice temperature, displacements, stresses, and strains, are presented graphically. The effect of thickness of thin films is studied; in addition, characteristics of stress evolution and displacement development in thin films are obtained. Finally, the influence of hot-electron blast force and thermal-mechanical coupling term are studied.
Nomenclature
Ae,Bl | = | constants of electron scattering rate |
Cl | = | lattice specific heat |
Ce | = | electronic specific heat |
G | = | electron phonon coupling constant |
G | = | electron and lattice coupling factor |
Kl | = | lattice thermal conductivity |
Ke | = | electronic thermal conductivity |
qe | = | electronic heat flow vector |
ql | = | lattice heat flow vector |
Te | = | electron absolute temperature |
Tl | = | lattice absolute temperature |
T0 | = | reference temperature |
λ, μ | = | lame coefficients |
Λ | = | electron-phonon coupling factor |
τe | = | electron thermal relaxation time |
τl | = | lattice thermal relaxation time |
Q | = | heat source |
ρ | = | density |
αt | = | linear expansion coefficient |
σij | = | stress tensor |
eij | = | strain tensor |
ui | = | displacement component |
γ | = | (3λ + 2μ)αt |
Subscripts and Superscripts
(1, 2) | = | material layer |
i(j, k) | = | Cartesian coordinates subscript |
0 | = | value at reference temperature T0 |