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Ma X.B.,Beihang University | Ma X.B.,Science and Technology Laboratory on Reliability and Environmental Engineering | Cheng B.,Beihang University
Advanced Materials Research | Year: 2014

The accelerated wear test of metal materials is researched, and the boundary conditions which required by failure mechanism consistency receive a meaningful exploration. This work presents a physical model about the boundary of accelerated stress to support accelerated test design. According to the material properties, the accelerated stress is restricted by three boundaries which are the boundary of the normal load, the boundary of relative speed and the boundary of their product. This research shows that failure mechanism consistency in accelerated wear test manifests as consistency of parameters in statistics, yet in physics, it depends on the three boundaries. © (2014) Trans Tech Publications, Switzerland.

Liu H.,Beihang University | Wang J.,Beihang University | Lu C.,Beihang University | Lu C.,Science and Technology Laboratory on Reliability and Environmental Engineering
Mathematical Problems in Engineering | Year: 2013

This paper presents an approach to bearing fault diagnosis based on the Teager energy operator (TEO) and Elman neural network. The TEO can estimate the total mechanical energy required to generate signals, thereby resulting in good time resolution and self-adaptability to transient signals. These attributes reflect the advantage of detecting signal impact characteristics. To detect the impact characteristics of the vibration signals of bearing faults, we used the TEO to extract the cyclical impact caused by bearing failure and applied the wavelet packet to reduce the noise of the Teager energy signal. This approach also enabled the extraction of bearing fault feature frequencies, which were identified using the fast Fourier transform of Teager energy. The feature frequencies of the inner and outer faults, as well as the ratio of resonance frequency band energy to total energy in the Teager spectrum, were extracted as feature vectors. In order to avoid a frequency leak error, the weighted Teager spectrum around the fault frequency was extracted as feature vector. These vectors were then used to train the Elman neural network and improve the robustness of the diagnostic algorithm. Experimental results indicate that the proposed approach effectively detects bearing faults under variable conditions. © 2013 Hongmei Liu et al.

Zhao G.,Science and Technology Laboratory on Reliability and Environmental Engineering | Zhao G.,Beihang University | Sun Y.,Science and Technology Laboratory on Reliability and Environmental Engineering | Sun Y.,Beihang University | Hu W.,Beihang University
Applied Mathematics and Information Sciences | Year: 2013

The system fault behavior model was investigated by the author first. System fault behavior model describes the occurrence and development process of malfunction in product, and analyzes the transmission process of unit malfunction in system and effects of various factors on system. In order to realize simulation of system fault behavior, it is necessary to perform formalized process of system fault behavior model, so as to acquire the mathematic description required by computer simulation. So the formalized description of fault behavior model (FBM) based on polychromatic sets theory was introduced. With consideration of the characteristics of model hierarchy and information variety of current fault behavior model, the method of polychromatic sets and polychromatic graph was adopted to describe the information such as objects, behaviors, restriction and relevant correlation in model. Formalized description of fault behavior model and convenient model for computer expression and operation were realized, which laid down a further solid foundation for simulation of system fault behavior. © 2013 NSP Natural Sciences Publishing Cor.

Hong S.,Science and Technology Laboratory on Reliability and Environmental Engineering | Zhang B.,Beihang University | Yang H.,Science and Technology Laboratory on Reliability and Environmental Engineering
Advances in Intelligent Systems and Computing | Year: 2014

This paper introduces a reconfigurable array synthesis method using the correlation weightings of Smooth Local Trigonometric Base (SLTB) for line antenna array and investigates its beam pattern characteristics. The beam pattern can be reconfigured by adjusting the overlapping coefficiency r of the bell-shaped function, the number K and the frequency spacing Δf of the SLTB. A fast and convenient reconfigurable array synthesis algorithm is proposed according to the evolvement rule of the beam pattern. The proposed method provides a nearly optimum first sidelobe level and gradually decaying sidelobes compared with Chebyshev weighting. Moreover, its computational complexity is O(N•K2) while the one of Chebyshev is O(N3). © Springer-Verlag Berlin Heidelberg 2014.

Wang Z.,Science and Technology Laboratory on Reliability and Environmental Engineering | Lu C.,Beihang University | Ma J.,Science and Technology Laboratory on Reliability and Environmental Engineering
Vibroengineering Procedia | Year: 2013

Bearings, as important components, are widely used in almost all forms of rotary machines. Bearing failure is one of the foremost causes of breakdown in rotating machinery. Such failure can be catastrophic and often results in lengthy industrial downtime that has economic consequence. In order to prevent unexpected bearing failure, this paper presents a health assessment method using Gaussian mixture model (GMM) based on a hybrid feature extraction method. This hybrid feature extraction method combines Empirical Mode Decomposition (EMD) and Singular Value Decomposition (SVD) to process the nonlinear and non-stationary vibration signal of bearing. Then, the health condition of bearing can be assessed and tracked in terms of confidence values (CVs) obtained by GMM. This method can be employed only using normal condition datasets without the need of failure data, which is a notable indicator for bearing health tracking and defect detection at the incipient stage. Its performance and effectiveness has also been validated via a bearing test-bed. © 2013 VIBROENGINEERING.

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