高速主轴系统热特性分析与实验

Thermal characteristics analysis and experimental study on high-speed spindle system

为了在设计阶段避免高速主轴在实际加工中由于温升过高可能会引起加工精度降低的问题,构建高速主轴的三维有限元模型(FEA)进行瞬态热-结构耦合分析.但传统热特性分析模型中,没有考虑结合面间接触热导致仿真精度较低,该有限元模型考虑接触热导对仿真结果的影响.利用Weierstrass-Mandelbrot函数表征轴承表面的粗糙形貌,利用功率谱法与粗糙表面形貌数据对分形参数进行辨识,并提出接触力学模型以计算用于接触热导建模的接触参数.最终,提出几何-力学-热综合预测模型计算结合面间的接触热导,有效避免统计学方法的不准确性与实验测量法通用性不强的缺陷.利用电机效率分析与轴承拟静力学分析法,分别求解电机与轴承热功率.由雷诺数判定流体的流动状态,并依据努塞尔数计算主轴部件的对流换热系数.将上述边界条件施加到该有限元模型对温度场与热变形进行仿真,并进行热特性实验验证该有限元模型的有效性.结果表明,该有限元模型的仿真精度明显优于不考虑接触热导的热特性分析模型.

A three-dimensional finite element analysis （FEA） model was proposed to conduct transient thermal-structure interactive analysis of high-speed spindle systems in order to avoid the degeneration of high speed spindle＇s machining accuracy in actual machining caused by an excessive temperature rise at the design stage. However, thermal contact conductance （TCC） was often ignored in traditional thermal mod- els of high-speed spindles. Which caused inaccuracies in traditional thermal models. The FEA model con- sidered TCC to improve the accuracy of traditional thermal models. The Weierstrass-Mandelbrot function was used to characterize the rough surface morphology of bearing rings. The fractal parameters were iden- tified by combing the power spectrum method with the measurement data of bearing ring＇s surface mor- phology. And a contact mechanics model was proposed to calculate the contact parameters used in the modeling of TCC. Then, an integrated geometry-mechanical-thermal model for TCC was proposed, which effectively avoided the inaccuracies of statistical methods and the poor generality of experimental measure ments. The heat generation of the built-in motor and rolling bearing was calculated based on the efficiency analysis method and quasi-static mechanics analysis, respectively. According to the Reynolds number, the flow status of the fluid was determined, and the convective heat transfer coefficients of spindle components were calculated based on the Nusselt number. The above boundary conditions were applied to the FEA model, and thermal characteristics experiments were conducted to demonstrate the validity of the FEA model. The results show that the simulation precision of the FEA model is superior to that of the tradi- tional thermal properly analysis models which ignor TCC.