Study On Thermal Field Distribution In Solid Materials In Simulations On Picosecond Laser Cutting And Marking

In order to shorten product development cycle and save costs, numerical simulationmethods are often used in scientific and technical studies. At present, the industrialization of ourpicoseconds laser is still in a startup state. Some key technical indicators can get from simulationof laser processing. Compared with actual processing effects, we can optimize the parametersand lay the foundation for domestic picoseconds laser in actual applications.Our work is a sub-project of “Simulation study on picoseconds lase”, supported by theNational High Technology Research and Development Program of China (“863” program)(Grant number:2011AA030205).In the process of laser cutting and marking, one of the key characteristic properties is thevariation of the temperature field. The physical properties and state (such as thermal diffusionthermal expansion as well as thermal stress) of the processing materials will change under heateffect when cut by pulsed laser. When laser energy accumulated strong enough, part of thematerial will vaporize or melt. Using this effect, we can accomplish laser processing as cutting,piercing, marking, etc. Therefore, one of the key studies of cutting and marking is the simulationof thermal field in processing materials. The current dissertation is focused on the followingaspects:1. Based on Gaussian beam distribution, we set up a simulation model on the intensitydistribution of picoseconds laser in vacuum. Results show that, picoseconds laser is of highintensity and low divergence. These features are favorable for laser machining.2. Take quartz and ceramics for example; on the basis of analytical solution of onedimensional Fourier thermal conductivity equation, we got thermal distribution of space and time for the materials. Our results show that, the temperature will be raised to1289.6oC when quartzmeets the first pulse of the picoseconds laser. In the case of ceramics, similarly, the temperaturewill up to1843.7oC when first pulses passed. And the temperature will exceed the melting pointof both two after the second pulse. By using assistant gas, people can achieve machining of thematerials.3. Without considering propagation velocity of heat wave, the classical Fourier equationwas not perfect. We modified the classical Fourier thermal conductivity equation by introducingvelocity item. Through the qualitative analysis, we found that, the variation of temperature fieldslows down by considering the speed. But the influence is limited.