Heat Accumulation Model And Parameter Optimization Of Femtosecond Laser Machining Process

Femtosecond laser has the advantages of high power,high precision and small heat affected zone.Surface material can be removed directly.Micromachining can be achieved by using femtosecond laser.Femtosecond laser has an irreplaceable advantage in the field of aerospace,semiconductor biological and other material processing.However,heat accumulation and temperature rise may be generated inside the material due to the multi pulse femtosecond laser.That can lead to phase transition,oxidation,or even melting.So how to optimization of femtosecond machining parameters and control the heat accumulation and temperature rise is a problem that need to be settled.This paper discuss the heat accumulation during the laser surface processing.Femtosecond laser surface processing of AZ31 magnesium alloy was simulated by using Matlab.Finite difference method is applied to the model.The effects of different scanning speed,laser repetition rate,laser spot size and laser energy on the thermal accumulation effect during the process was simulated.The laser parameter was optimised.And through the simulation of the process of stainless steel,compared with other models.Thermal conductivity and specific heat was considered.The surface heat accumulation and temperature changes of AZ31 magnesium alloy at the scanning rate of 1 m/s,2 m/s,3 m/s,4 m/s were simulated by using finite difference method.Results showed that the increase of scanning speed can decrease the heat accumulation temperature.When the scanning speed is 1~3 m/s,the heat accumulation temperature of AZ31 magnesium alloy was not stable.When the scanning speed was 4 m/s,the heat accumulation temperature of AZ31 magnesium alloy surface tends to be balanced after 10 pulses.Scanning speed affects the heat accumulation during the process by change the spot overlap.In addition,The surface heat accumulation and temperature changes of AZ31 magnesium alloy at the laser repetition rate of 100 kHz,500 kHz,1 MHz and 2 MHz were simulated.Results showed that the increase of laser repetition rate increases the surface heat accumulation temperature and it has a great influence on the heat accumulation.The laser repetition rate can affect both the overlap rate and the heat transfer time,so the heat accumulation of the process was affected.Two methods to improve the laser fluence were compared with the method of reducing the spot size and improving the laser energy.Results showed that reducing the spot cause lower heat accumulation.Finally,the femtosecond machining process of stainless steel was simulated,and the simulation results were compared with other models,results showed that the model used in this paper can effectively estimate the heat accumulation and temperature during the femtosecond laser processing.