Modeling of dynamic process in the laser-off period during laser drilling

Fig. 3. Image sequences of the keyhole fabricated by a single laser pulse with a laser energy of 4.86 J in both the laser-on and -off periods. The white bar represents 1 mm.

Download full size

View in Article

Fig. 4. Temperature distributions of the keyhole fabricated by a single laser pulse with a laser energy of 4.86 J in both the laser-on and -off periods. The white bar represents 1 mm.

Download full size

View in Article

Fig. 5. Velocity distributions of the keyhole fabricated by a single laser pulse with a laser energy of 4.86 J in both the laser-on and -off periods. The white bar represents 1 mm.

Download full size

View in Article

Table 1. Properties of Aluminum and Constants in Simulation.[22,23]

View table

View in Article

Table 1. Properties of Aluminum and Constants in Simulation.[22,23]

Nomenclature (unit)	Symbol	Value
Melting/evaporation temperature (K)	$T_{m} / T_{v}$	933/793
Solid/liquid density ( $kg / m^{3}$ )	$ρ_{s} / ρ_{l}$	2702/2385
Solid/liquid specific heat (J/m/K)	$c_{s} / c_{l}$	917/1080
Solid/liquid conductivity (W/m/K)	$k_{s} / k_{l}$	237/100
Latent heat of fusion/evaporation (J/kg)	$L_{m} / L_{v}$	$3.6 \times 10^{5} / 1.09 \times 10^{7}$
Temperature coefficient of surface tension (N/m/K)	$\frac{\partial σ}{\partial T}$	$- 0.3 \times 10^{- 3}$
Dynamic viscosity (Pa s)	$μ$	$1.6 \times 10^{- 3}$
Convective heat transfer coefficient ( $W / m^{2} / K$ )	$h_{c}$	20
Radiation emissivity ( $W / m^{2} / K^{4}$ )	$ε$	0.2
Absorption coefficient	$η$	0.26
Stefan–Boltzmann constant ( $W / m^{2} / K^{4}$ )	$σ_{s}$	$5.67 \times 10^{8}$
Focal radius (μm)/Pulse width (μs)	$r_{0} / τ$	300/1000

Table 2. Numerical and Experimental Data for Both Keyhole Depth and Width.

View table

View in Article

Table 2. Numerical and Experimental Data for Both Keyhole Depth and Width.

Energy (J)	Depth^a (mm)	Depth^b (mm)	Diameter^a (mm)	Diameter^b (mm)
1.22	0.894	0.902	0.518	0.523
2.07	1.322	1.313	0.752	0.741
3.13	1.448	1.420	0.824	0.817
4.86	1.523	1.510	0.872	0.870
6.31	2.070	2.109	0.863	0.875
8.01	2.745	2.693	0.901	0.920
10.20	3.120	3.131	0.943	0.958
13.27	3.439	3.357	1.052	1.046