Temperature field-based equivalent heat source study for short arc discharge machining of C/SiC composites
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摘要: 针对C/SiC复合材料放电加工仿真普遍采用高斯热源,忽略间隙弧柱热效应的问题,文章以放电过程的热效应进行两部分等效。采用椭球体热源等效电弧弧柱,高斯面热源等效工件表面热效应,从平行和垂直于碳纤维两个方向进行温度场仿真,对比传统高斯热源与等效热源,并通过实验进行验证。结果表明:运用新型等效热源仿真,得到的凹坑尺寸比传统高斯热源更加接近实验加工的尺寸,预测精确度提高20%。Abstract: In response to the problem that C/SiC composite electrical discharge machining simulations commonly use a Gaussian heat source and ignore the thermal effect of the interstitial arc column, this paper performs a two-part equivalence with the thermal effect of the discharge process. Using an ellipsoidal heat source equivalent to an arc-arc column and a Gaussian surface heat source equivalent to the surface thermal effect of the workpiece, temperature field simulations are carried out in two directions, parallel and perpendicular to the carbon fibre, comparing a conventional Gaussian heat source with an equivalent heat source, and verified by experiment. The results show that: using the new equivalent heat source simulation, the size of the crater obtained is closer to the experimentally machined size than the conventional Gaussian heat source, with a 20% improvement in prediction accuracy.
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Key words:
- SEAM /
- equivalent heat source /
- C/SiC composites /
- Gaussian heat source
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参数 碳纤维 SiC 密度/(kg/m3) 1 850 3 200 比热容/(J/kg·K) 710 656 导热系数/(W/(m·K)) 50(轴向)5(径向) 185 升华温度/K 3 823 2 973 表 2 仿真条件
名称 数值或条件 放电电压/V 30 放电电流/A 40 放电频率/Hz 600 占空比/(%) 90 工件 C/SiC 半径R/mm 0.57 a=b/mm 1.373 5 c/mm 0.58 v/(mm/ms) 0.386 6 表 3 实验条件
名称 数值或条件 放电电压/V 30 放电频率/Hz 600 占空比/(%) 90 工件 C/SiC 电极 Cu 极性 正极性加工(工件+,电极−) 介质 空气 表 4 垂直于碳纤维仿真参数与实验参数
垂直于碳纤维 高斯热源模拟仿真 等效热源模拟仿真 实验 误差 数值 差值 数值 差值 传统高斯热源 等效热源 X1/mm 3.781 6 0.437 6 3.718 1 0.564 3 0.69 0.365 8 0.182 2 X2/mm 4.219 2 4.282 4 Y1/mm 2.781 9 0.438 6 2.714 2 0.574 1 0.69 0.364 3 0.168 0 Y2/mm 3.220 5 3.288 3 Z1/mm 2.090 8 0.069 2 2.057 0 0.103 0 0.18 0.615 6 0.427 8 Z2/mm 2.160 0 2.160 0 表 5 平行于碳纤维仿真参数与实验参数
平行于碳纤维 高斯热源模拟仿真 等效热源模拟仿真 实验 误差 数值 差值 数值 差值 传统高斯热源 等效热源 X1/mm 3.752 0 0.485 7 3.689 5 0.617 9 0.88 0.448 1 0.297 8 X2/mm 4.237 7 4.307 4 Y1/mm 3.391 3 0.214 1 3.382 3 0.235 0 0.88 0.756 7 0.733 0 Y2/mm 3.605 4 3.617 3 Z1/mm 6.881 6 0.118 4 6.778 8 0.221 2 0.38 0.688 4 0.417 9 Z2/mm 7.000 0 7.000 0 -
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