Laser-pulse-induced temperature, thermal stress, and crater morphology effect during multipulse nanosecond laser manufacturing.

We construct a numerical model for multipulse laser drilling. It is found that the previous laser-pulse-induced temperature accumulation, thermal stress occurrence, and crater morphology change promote subsequent pulse laser drilling. Among them, previous laser-pulse-induced temperature accumulation contributes significantly to the drilled crater depth when the workpiece temperature is higher than its melting point just before the subsequent laser pulse irradiation, especially in a short pulse interval condition. The crater morphology change becomes the main contributor when the workpiece temperature decreases below the melting point, often in a long pulse interval condition. Besides, the previous occurrence of laser-pulse-induced thermal stress always has had little influence on the drilled crater. This work can be a theoretical reference, especially for multipulse laser manufacturing.