Thermal Analysis of Laser Drilling Process
In laser drilling process, the material removal involves with evaporation at the surface, liquid ejection, and solid heating. However, liquid ejection vanishes for the lasers with the pulse length within the rage and higher than the nanoseconds. However,
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Thermal Analysis of Laser Drilling Process
In laser drilling process, the material removal involves with evaporation at the surface, liquid ejection, and solid heating. However, liquid ejection vanishes for the lasers with the pulse length within the rage and higher than the nanoseconds. However, in drilling applications mass removal by liquid ejection is desirable because the rate of material removed becomes high. Analytical modeling the laser heating process in relation to drilling is difficult, since process involves with the phase change and fluid flow due to the evaporation at the surface. However, numerical modeling is feasible with some useful assumptions.
2.1 Heating Analysis Laser high intensity beam interaction with the solid surface results in rapid evaporation of the surface. Depending on the power intensity and the duration of the laser pulse, the pressure generated at the laser irradiated surface becomes very high. This situation is especially true for nanosecond laser pulses. Moreover, the prediction of recoil pressure is essential, since the mass removal rate depends on the pressure differential at the cavity surface. Consequently, one of the governing physical parameters involving laser ablation is the pressure generated at the interface of vapor–liquid phases in the cavity. Since the pulse duration is very short and the magnitude of pressure generated in a small area (limited to irradiated spot size) is very high, liquid ejection replaces the vapor jet emanating from the irradiated surface. Since the process is rapid and involves with high temperature phenomenon experimentation into the physical processes becomes difficult and expensive. However, model studies give insight into the physical processes taking place during the ablation process. The analyses related to the model study are presented in line with the previous studies [1–5]. To model the laser evaporative heating situation, energy equation for each phase needs to be solved independently as well as coupled across the interfaces of the two-phases mutually exist (mushy zones). In the initial stage of heating,
B. S. Yilbas, Laser Drilling, SpringerBriefs in Manufacturing and Surface Engineering, DOI: 10.1007/978-3-642-34982-9_2, © The Author(s) 2013
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2 Thermal Analysis of Laser Drilling Process
Fig. 2.1 Schematic of a laser drilling process
Fig. 2.2 Temporal variation of laser pulse intensity, obtained from equation and the measured from the experiment
conduction in solid with convective boundary at the surface should be considered. In actual laser pulse heating, the laser output power intensity distribution at the surface of the workpiece is Gaussian and this should be accommodated in the analysis such that its centre is at the centre of the co-ordinate system Fig. 2.1. The temporal variation of laser power intensity resembling the actual laser pulse
2.1 Heating Analysis
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is shown in Fig. 2.2. This arrangement results in an axisymmetric heating of the substrate material. The diffusion equation for a solid phase heatin
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