激光辐照移动平板温度场分布的有限元分析

Finite element analyses of temperature fields in moving solids irradiated by a laser source

基于热传导理论,采用有限元方法建立激光辐照无限长移动平板表面激发瞬态温度场的三维模型,用以研究移动平板上下表面瞬态温度场.考虑板材料的热物理参数依赖于温度、板表面的热辐射及对流等因素,计算了上述因素及移动速度对温度场的影响,并进一步讨论了激光半径对温度场的影响.数值结果表明:激光辐照移动平板后,在材料中将产生准稳态温度场;材料热物理参量的温度系数会对激发的温度场分布产生影响;增加对流传热会导致温度峰值和准稳态温度值降低;而表面热辐射的影响可以忽略.此外,增加移动速度会引起温度峰值及准稳态温度值降低,并且到达准稳态所需的时间缩短;温度峰值及准稳态温度值随激光源的半径减小而增加,温度峰值的增幅明显大于准稳态温度值的增幅.

Based on heat conduction theory,a finite element method is introduced to investigate the three-dimensional transient temperature fields in a moving plate irradiated by a laser beam.The laser beam is assumed to be with Gaussian distribution,and the plate is considered as infinite along the motion direction,while the width and the height are finite.Considering the thermal physical parameters depended on temperature,convection and radiation factors of the surfaces,and the motion of the plate,the temperature fields on the upper and bottom surfaces of the plate are obtained.The numerical results show that the quasi-steady state temperature fields are approached.Comparing the temperature fields obtained by before and after considering the factors described above,it shows that the temperature dependences of the thermal properties of the material have distinct influences on the temperature fields.In the conditions that the thermal conductivity and thermal capacity of the material are dependent of temperature,the results are presented for two cases:(1) when neglecting temperature dependence of the thermal capacity,the maximum temperature and the quasi-steady state temperature are both higher than those of considering the temperature dependence;(2) when neglecting temperature dependence of the thermal conductivity,the maximum temperature will decrease while the quasi-steady state temperature will be the same as that of considering the temperature dependence.In addition,with increasing the convective heat transfer coefficient at the upper surface,the maximum temperature and the quasi-steady state temperature will decrease,while the effect of radiative heat losses of the surface can be ignored.Meanwhile,changing the moving velocity not only affects the temperature fields,but also alters the maximum temperature and the time for reaching the quasi-steady state condition.Furthermore,with the radius of the laser source decreasing,the maximum temperature and quasi-steady state temperature will both increase,while the former change is more obvious.