Papers by Author: Wei Dong Cheng

Abstract: Defect diagnosis of rolling element bearings operating under time-varying rotational speeds entails order tracking and analysis techniques that convert a vibration signal from the time domain to the angle domain to eliminate the effect of speed variations. When a signal is resampled at a constant angular increment, the amount of data padded into each data segment will vary, depending on the rate of change in the rotational speeds. This leads to changes in the distance between the adjacent impulse peaks, and consequently, the result of order analysis. This paper presents a quantitative analysis of key factors affecting the accuracy of order analysis on rolling element bearings under variable speeds. An analytical model is established and simulated. The effects of speed variation, instantaneous speed, angular interval between impulses, and the rising time of impulse are specified. It is concluded that the results of order analysis will be smaller as the rotational speed increases, and becomes larger when the speed decreases. Furthermore, the error is larger under low speeds than high speed.

Abstract: Frequency-smear phenomenon caused by fierce rotating speed variation made it difficult to extract the fault features of the rolling bearing. An approach based on time-frequency order tracking and SPWVD was proposed in this paper. The influence of speed variation was reduced by resampling the time-domain non-stationary signal at constant angle increments with order tracking analysis. The precision of instantaneous frequency estimation (IFE) in time-frequency order tracking was improved by the use of Smoothed Pseudo Wigner-Ville Distribution (SPWVD). The simulation signal and experiment on test-rig revealed that the proposed method was more effective than the traditional order tracking in clarifying incipient fault.

Abstract: A velocity blending method is devised for micro-segment line high-speed machining. The model is constructed for blending velocity, and the blending curve equation is established under the constraint of maximized contour error. According to MATLAB simulation, the proposed model and its solving algorithm can achieve the high-speed linking between micro-segment lines, and the efficiency is promoted distinctly.

Abstract: Some of the critical and practical issues regarding the problem of condition monitoring of mobile equipment have been discussed, and an anomaly detection method without priori knowledge has been proposed. The method involves setting amplitude benchmark via spectrum amplitude in normal condition and obtaining the maximum entropy value in abnormal condition. The condition identification is achieved through estimating the amount of anomaly information in spectrum, and a measure of anomaly condition is given by the anomaly degree derived from entropy value dividing the maximum value. The sensitivity, stability and computation load of the method have been also discussed, and the method is validated on an experimental test-bed that the test bearings with different fault diameter support the motor shaft.

Abstract: In order to find the typical acoustic emission (AE) parameters for distinguishing the original specimen without being welded and the specimen with blowhole defect all made of WELDOX960 steel. Three-point bending test on the two specimens were conducted respectively. Firstly, from the procedural map, we deduced that the reason why there was such a sudden energy leap is because of the activities of welding crack, and the multistage energy release also because of the step by step propagation of welding crack in despite of any kind of welding defect. AE parameter distribution map and statistical distribution analysis results also validated the before-mentioned judgment. We found the parameter distribution map of amplitude, count, duration time and centroid frequency of the two specimens were distinctly different, thus those characters can be used as the indicator on its own for distinguishing the two kinds of AE source, i.e., the plastic deformation and the crack generation and propagation