具有内阻的旋转锥形复合材料刀杆铣削过程稳定性的仿真分析

ANALYTICAL INSTABILITY OF MILLING WITH ROTATING TAPERED COMPOSITE TOOL CONSIDERING INTERNAL DAMPING

研究考虑材料内阻的旋转圆锥形复合材料刀杆铣削系统的再生颤振稳定性。基于复合材料粘弹性本构关系、Hamilton原理和Rayleigh梁理论,结合再生时滞铣削力模型,分别导出旋转坐标以及惯性坐标表示的颤振偏微分方程。采用Galerkin法对颤振偏微分方程进行离散化。基于自由振动分析和能量法计算复合材料刀杆的模态损耗因子;基于特征值分析技术计算旋转复合材料刀杆的临界速度和失稳阈。采用时域半离散法和频域零阶近似解法,预测切削系统的稳定性。分析锥度比、长径比、铺层角、铺层方式,以及内、外阻对切削稳定性的影响。计算结果表明,轴对称旋转刀杆铣削过程在两种坐标系下的稳定性预测结果是一致的。研究发现,在高转速下,由于旋转复合材料刀杆内阻的作用,切削系统出现新的不稳定区域。这些新的不稳定区域的起始转速等于旋转复合材料刀杆的失稳阈。

A new regenerative chatter stability prediction model is presented for milling process with internally damped rotating tapered composite cutter bar.Based on the viscoelastic constitutive relation of composite combined with Hamilton principle and Rayleigh beam theory,the chatter governing equations of system are obtained in fixed and rotating coordinate frame,respectively.Modal damping loss factors of composite bar are calculated by free vibration analysis and energy approach.The critical rotating speed and instability threshold are evaluated by solving the characteristic problem of the rotating composite cutter bar.The stability of the system is predicted using both zero order approximation frequency domain method and semi-discrete time domain method.It is shown that both rotating and fixed frame based models give the same results for dynamically symmetric tools.For the milling process with rotating composite cutter bar,it can be found that material internal damping can lead to a new chatter instability zone at high rotational speeds.This new chatter staring point equals to the instability threshold of rotating composite cutter bar.