Establishment of Dynamic Model of axle Box Bearing of high-speed Train under Variable Speed Conditions

This paper establishes a dynamic model of the bearing rotor system of a high-speed train under variable speed conditions. Different from previous works, the proposed model simplifies the contact stress and considers the compensation balance excitation caused by the rotor mass eccentricity. The angle iteration method is used to solve the challenging problem that the roller space position cannot be determined in bearing rotation. The simulation results show that the model accurately describes the dynamics of bearing under varying speed profiles that contain acceleration, deceleration and speed oscillation stages. The order ratio spectrum of the bearing vibration signal indicates that both single frequency and multiple frequency in simulation results are consistent with that in theoretical results. Experiments of bearing with outer ring fault and inner ring fault under various operating conditions are presented to verify the developed model.

A model-based local fault size measurement method of rolling bearing considering load influence

Rolling bearing local fault vibration mechanism research is the theoretical basis of advanced bearing fault diagnosis and size measurement technology. In this paper, the additional displacement and impact force excitation of inner and outer ring local faults under low speed and heavy load condition are analysed, and rolling bearing local fault vibration model is established. The simulated dual impulse characteristics have higher accuracy under low speed and heavy load condition compared with other traditional local fault models. The outer and inner ring fault simulated dual impulse interval errors are 6.7% and 1.1%, respectively. Then the local fault vibration mechanism is analysed, and the influence of heavy load condition on dual impulse characteristic is not negligible. Finally, a size measurement method of bearing local fault based on vibration model is proposed. Two sizes of outer ring fault bearing are tested in four different working conditions, and the average measurement error is 3.78%. The results show that the proposed method can overcome the influence of different working conditions and accurately measure different local fault sizes.

Fault Diagnosis of Intershaft Bearing Using Variational Mode Decomposition with TAGA Optimization

To efficiently extract the features of aeroengine intershaft bearing faults with weak signal, the variational mode decomposition (VMD) method based on the tolerant adaptive genetic algorithm (TAGA) (TAGA-VMD) is proposed by introducing the idea of tolerance into the traditional adaptive genetic algorithm in this paper. In this method, the tolerant genetic algorithm was adopted to find the optimum empirical parameters K and α of VMD. A fault simulation experiment system of intershaft bearings was built for the inner ring fault and outer ring fault of bearings to verify the proposed TAGA-VMD method. The results show that the proposed method can effectively extract the fault feature frequency of intershaft bearings, and the error between the extracted fault feature frequency and the theoretical value of fault frequency is less than 0.1%. The efforts of this study provide one promising fault feature extraction approach for aeroengine intershaft bearing fault diagnosis with weak signal.

Research on early weak structural damage detection of aeroengine intershaft bearing based on acoustic emission technology

Until now, there is no effective method to detect the early weak structural damage of the aero engine intershaft bearing. In this article, an online method based on acoustic emission technology is used to detect the early weak structural damage of aeroengine intershaft bearing. The combination of maximum correlated kurtosis deconvolution and bandpass filter is proposed to enhance and denoise fault characteristic signals of the aero engine intershaft bearing. The Hilbert envelope demodulation is used to extracting the bear fault characteristic frequency. Under aeroengine working conditions, the experiment of an intershaft bearing with outer ring fault is carried out. The result shows that bearing outer ring fault characteristic frequency and bearing vibration frequencies clearly appear in the envelope spectrum of the acoustic emission signal. Therefore, online detection of early weak structure damage of aeroengine intershaft bearing is realized by acoustic emission technology under the background of strong noise.