Abstract:

Initial defects and working environment will cause different degrees of cracks on the shaft. In order to analyze the effect of cracks on the rotor system, the finite element models of the cracked rotor were established through Jeffcott rotor dynamics model and fracture mechanics theory. The simulation analysis of different crack depths, crack angles and different speeds was carried out, and then a mechanical comprehensive failure table was used to carry out experimental research on part of the cracked rotors. The results show that: the appearance of cracks causes high?order frequency doubling components such as 2X in the vibration response of the system, and the phenomenon of depressions or even ferrules appeared in the axis track, and the vibration amplitude increases accordingly. As the crack deepens, the instability of the system gradually increases. The change of the crack inclination angle also affects the vibration characteristics of the system, and the 45?degree crack has the greatest impact on the system. When the speed starts to increase, the influence of the cracks on the system gradually decreases, the time?domain waveform tends to be stable, and the axis trajectory gradually changes back to an ellipse. Finally, the experimental results were compared with the simulation data to verify the conclusions of simulation and modeling.

Key words: Cracked rotor system, Crack parameters, Rotating speed, High?order doubling components, Vibration amplitude

摘要：

初始缺陷、工作环境会导致转轴出现不同程度的裂纹。为分析裂纹对转子系统的影响，通过Jeffcott转子动力学模型和断裂力学理论建立了裂纹转子系统的有限元模型。对不同裂纹深度、裂纹角度和不同转速进行了仿真分析，并采用机械综合故障台对部分裂纹转子进行了实验研究。结果表明，裂纹的出现使系统振动响应中出现2X等高阶倍频分量，轴心轨迹出现凹陷甚至套圈现象，振动幅值也随之变大；随着裂纹的加深，系统的不稳定性逐渐增强；裂纹倾斜角度的改变也影响系统的振动特性，45°裂纹对系统的影响最大，当转速开始加快时，系统受裂纹的影响慢慢减小，时域波形趋于平稳，轴心轨迹逐渐变回椭圆形。对实验结果与仿真数据进行对比，验证了仿真及建模的结论。

关键词: 裂纹转子系统, 裂纹参数, 转速, 高阶倍频分量, 振动幅值