激光辅助铣削SiCf/SiC复合材料铣削力预测研究

Research on prediction of milling force in laser-assisted milling of SiCf/SiC composites

  • 摘要: SiCf/SiC复合材料铣削过程中铣削力大、质量难以保证,是典型的难加工材料。因此采用多元线性回归法,建立激光辅助整体铣削与分步铣削(过渡层/烧蚀层)的切向力Fx与径向力Fy预测模型,并研究主轴转速、每齿进给量、激光功率对铣削力的影响。试验验证结果表明,各模型平均相对误差低于5%,决定系数R2均大于0.86。结合微观表面形貌分析,基于应变率硬化与材料去除机理,揭示了工艺参数对铣削力的影响机制,结果表明,由于应变率硬化效应,导致Fx随着转速增大而增加;由于烧蚀层的隔热效应和过渡层的相变梯度,导致激光辅助分步铣削过渡层LAAM(S T)中激光功率对Fx呈正相关,而激光辅助整体铣削LAAM(O)和激光辅助分步铣削烧蚀层LAAM(S A)中影响较小;由于切削机制由“压痕断裂”向“剪切滑移”转变,激光辅助整体铣削LAAM (O)烧蚀层中进给量增大会因压痕断裂去除体积提升使铣削力上升;激光辅助分步铣削过渡层LAAM (S T)、激光辅助分步铣削烧蚀层LAAM (S A)的过渡层与疏松粉末层则因剪切滑移效应,铣削力随进给量增大而降低。

     

    Abstract: The milling process of SiCf/SiC composites is characterized by high cutting forces and challenging quality assurance, rendering them a typical difficult-to-machine material. In this study, multiple linear regression is adopted to establish predictive models for tangential force Fx and radial force Fy in both laser-assisted single-step milling and sequential milling (transition layer/ablation layer). The effects of spindle speed, feed per tooth, and laser power on milling forces are systematically investigated. Experimental validation demonstrates that the average relative error of each model remains below 5%, with coefficients of determination (R2) exceeding 0.86. Integrating microscopic surface morphology analysis with strain-rate hardening theory and material removal mechanisms, the influence mechanisms of process parameters on milling forces are elucidated. The results reveal that Fx increases with spindle speed owing to the strain-rate hardening effect; laser power exhibits a positive correlation with Fx in LAAM(S T) due to the thermal insulation effect of the ablation layer and the phase-transformation gradient within the transition layer, whereas its influence is negligible in LAAM(O) and LAAM(S A). Due to the change of cutting mechanism from "indentation fracture" to "shear slip", the increase of feed rate in LAAM (O) ablation layer will increase the milling force due to the increase of removal volume of indentation fracture. The milling force of the transition layer and the loose powder layer of LAAM (S T) and LAAM (S A) decreases with the increase of feed rate due to the shear slip effect.

     

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