Abstract: In order to study the fault features of the inter-shaft bearing， a new type of four degree of freedom dynamic model of inter-shaft bearing with outer race fault is established based on the Hertz nonlinear contact theory， which considers time-varying displacement excitation. A dual-rotor test rig is used to simulate the faults of the bearing outer race， and the experimental results are in good agreement with the numerical simulation results， which verifies the accuracy of the model. The dynamic model is used to analyze the vibration response of the bearing when outer race is faulty. The dependences of the vibration amplitude of the square root， shape factor， impulse factor， peak factor and kurtosis factor on the size of defect and radial load have been studied. The results show that the vibration amplitude of the square root of the inter-shaft bearing increases with the increase of the defect size or radial load. The dimensionless parameters such as impulse factor， peak factor and kurtosis factor increase first and then decrease with increasing defect size. With the increase of radial load， the above three dimensionless parameters show an increasing trend. At the same time， it is proved that the characteristic parameters such as the amplitude of the square root， pulse factor， peak factor and kurtosis factor are sensitive to the outer race fault of inter-shaft bearing.

Key words: Inter-shaft bearing；Time-varying displacement excitation；Outer race fault；Dynamic model；Radial load

摘要： 为了研究航空发动机中介轴承故障特征，基于Hertz非线性接触理论，建立了一种考虑时变位移激励的4自由度中介轴承外圈故障动力学模型。采用双转子试验台对中介轴承外圈故障进行实验模拟，实验结果和动力学模型数值求解结果一致，验证了所建立模型的准确性。采用动力学模型仿真分析了中介轴承外圈存在缺陷情况的振动响应。研究了中介轴承振动方根幅值、波形因子、脉冲因子、峰值因子和峭度因子随缺陷大小、径向载荷的变化规律。结果表明:随着缺陷尺寸或径向载荷增大，中介轴承振动方根幅值呈增大趋势。脉冲因子、峰值因子和峭度因子等无量纲参数随着缺陷尺寸增加，先增大后减小。随着径向载荷增加，以上三个无量纲参数呈增大趋势。同时，证明方根幅值、脉冲因子、峰值因子和峭度因子等特征参数对中介轴承外圈故障敏感。

关键词: 中介轴承；时变位移激励；外圈故障；动力学建模；径向载荷