摘要
Ti6Al4V合金在毫秒激光打孔过程中,沿孔壁会形成严重影响成品性能的重铸层。考虑熔体受到的热学和力学等方面的影响,基于修改的流体力学方程和改进的水平集法,建立了激光打孔的固/液/气三相二维数值计算模型,在单脉冲能量为3J的条件下,对不同脉宽参数的激光打孔进行数值研究。运用后处理技术提取了打孔过程中重铸层的温度场、流场和厚度分布情况。结果表明,蒸发和喷溅是熔体排除的主要方式,重铸层是在热-力耦合作用下形成的。重铸层的厚度随激光脉宽的增大而增加,并呈现从孔口到孔底逐渐变薄的特征。
During the process of millisecond laser drilling of Ti6Al4 V alloys,the recast layer forms along hole walls,which is a serious detriment to hole quality.In consideration of the thermal and mechanical parameters influencing melt and based on the modified equations of fluid mechanics and improved Level-Set method,a solid/liquid/gas three-phase two dimensional numerical model is constructed used for laser drilling.The numerical investigation of laser drilling with different pulse widths and with single pulse energy of 3Jis conducted.The temperature field,flow field,and thickness distribution of recast layer during the drilling process are obtained by using the post-processing technology.The results indicate that molten liquid is discharged mainly by means of evaporation and ejection and the recast layer is formed under the coupling effect of heat and force.The recast layer thickness increases with the increment of laser pulse width,which possesses a characteristic of recast layer becoming thin slowly from top hole to bottom hole.
引文
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