In‐situ surface absorptivity prediction during 1.06 μm wavelength laser low aspect ratio machining of structural ceramics

This study predicts the variation of surface absorptivity with temperature for structural ceramics such as magnesia (MgO), alumina (Al 2 O 3 ), silicon nitride (Si 3 N 4 ), and silicon carbide (SiC). In‐situ temperatures reached during pulsed 1.06 μm Nd:YAG laser low aspect ratio cavity machining of the ceramics under various number of pulses were sensed by a K‐type thermocouple. A thermal model was calibrated by varying the absorptivity to match the computed temperature to that with the measured temperature in the ranges of 860–980 K (MgO), 1020–1120 K (Al 2 O 3 ), 900–1150 K (Si 3 N 4 ), and 700–950 K (SiC) at a given distance from center of the laser beam. Such absorptivity predictions are critical for accurate predictions of suitable machining parameters and in determining actual energy absorbed during low aspect ratio laser machining of structural ceramics. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)