摘要
为了降低激光加工试验成本,建立较为完善的激光加工仿真模型,预测加工材料表面氧化物分布情况,基于计算流体力学方程、流固耦合理论和双温模型,借助OpenFOAM流体仿真平台,通过C++自编程的方式,建立了超快激光烧蚀的三维热化学反应模型。模型考虑了等离子体对入射激光能量的吸收和散焦作用以及温度变化对表面反射率和分层吸收系数的影响,采用Maxwell-Stefan理论模拟了多元组分间的扩散现象,并利用配分函数法拟合了热化学反应速率。采用240 fs脉冲激光进行相同功率、不同脉冲数下的激光打孔试验,验证了仿真模型的有效性。试验结果表明,随着脉冲数的增加,等离子体对激光的屏蔽作用增强,烧蚀后材料表面微孔结构的直径逐渐增大,烧蚀区域的氧化物含量逐渐上升。通过仿真结果与试验结果对比可知,在表面微孔结构的直径方面,两者间的相对误差不超过5%,在表面氧化物含量方面,相对误差控制在12%以内。并且分析出当脉冲数较小时,等离子体作用较弱,热效应在激光能量中所占比例比较大,使得仿真与试验的氧化物占比误差较大。将等离子体与化学反应模块相结合,采用配分函数法求解了热化学反应速率,能够预测材料表面氧化物含量。
In order to reduce the experimental cost of laser processing and establish a relatively perfect laser processing simulation model to predict the ideal oxide distribution on the surface of the material,a three-dimensional thermochemical reaction model based on computational fluid dynamics equation,fluid-structure coupling theory and two-temperature model of ultrafast laser ablation is investigated by means of C++self programming with the help of fluid simulation platform OpenFOAM.In the model,the absorption and defocusing effects of plasma on incident laser energy are considered,and the effects of temperature change on surface reflectivity and layered absorption coefficient are analyzed.The diffusion phenomenon among multicomponent components is simulated by Maxwell Stefan theory,and the thermochemical reaction rate is fitted by partition function method.The experiments of laser drilling with 240 fs pulse laser at the same power and different pulse numbers are carried out to verify the effectiveness of the simulation model.The experimental results show that the diameter of the microporous structure on the surface of the ablated material,the shielding effect of the plasma on the laser and the oxide content in the ablated region gradually rise up with the increase of the number of pulses.By comparing the simulation results with the experimental results,it can be seen that the relative error is less than 5%in simulating the diameter of the surface microporous structure,and within 12%in simulating the surface oxide content.It is analyzed that when the pulse number is smaller,the plasma effect is weaker,and the thermal effect accounts for a larger proportion,which makes the larger error of the oxide proportion between the simulation and the experiment.In this paper,plasma and chemical reaction module are combined to solve the thermochemical reaction rate by partition function method.The content of oxide on the surface of materials can be predicted.
作者
张春波
吴成军
袁浩天
ZHANG Chunbo;WU Chengjun;YUAN Haotian(School of Mechanical Engineering,Xi’an Jiaotong University,Xi’an 710049)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2024年第8期94-106,共13页
Journal of Mechanical Engineering
基金
国家重点研发计划资助项目(2016YFB1102500)。
关键词
超快激光烧蚀
多元组分扩散
热化学反应
等离子体
ultrafast laser ablation
multi-component diffusion
thermo-chemical reaction
plasma
