Advanced Materials Research Vols. 199-200

Abstract: A new method of vibration suppression, interior inlay viscous fluid unit (IVFU), has been proposed and investigated in this paper. Experimental results show the inherent characteristics of interior inlaid fluid subsystem in suppressing the plate vibration. A numerical simulation is carried out using software FLUENT. The original liquid-solid coupling model is rationally simplified to an approximate hydrokinetic model by constructing the fluid dynamic boundary conditions. A criterion of energy dissipation is proposed. Simulation results show that under the first principal vibration, the damping effect of 1/2 volume water is better than that of 2/3 volume, and under the second principal vibration, the latter behaves a self-adaptive characteristic more than the former. Simulation results clearly illustrate the inherent mechanism of suppressing vibration and the characteristic of fluid movement in closed cavity on different situations.

Abstract: In the paper the free vibration system of bridge section model is designed in order to measure the wind-induced effects on the bridge section model in the wind tunnel. In the system the suspension device is constituted with decoupling sliding components and simple spring suspension. Meanwhile, a set of data measurement and acquisition device based on the Labview is provided in the system. The measurement on the wind-induced static force, flutter and vortex-induced vibration of the bridge section model can be conducted at single degree of freedom or multiple degrees of freedom.

Abstract: Because AE (Acoustic Emission) signals in bearing fault monitoring unavoidably mixed various noise which lead to wide band characteristics, in this paper, the collected AE signals are pre-processed by EMD (Empirical Mode Decomposition) algorithm to extract useful information in the concerned frequency range, after that, power spectrum is used to locating analysis and pattern recognition. Experiment show that this method could improve the detection accuracy in rolling element bearing fault diagnosis.

Abstract: A new method for gear local fault diagnosis based on vibration signal analysis is presented in this paper by using the concept of instantaneous frequency. The data from the physical simulation are used to detect the change in the instantaneous frequency and meshing vibration energy of the gear tooth fault by Empirical Mode Decomposition and Hilbert Huang Transformation (EMD-HHT). It is verified that method is effective by rig testing of geared system.

Abstract: Based on the study and analysis that Lyapunov exponent can be used to characterize the motion state of system, in connection with the nonlinear dynamic characteristics shown from the performance of fault rotating mechanical system, the authors proposed the analysis method of Lyapunov dimension on the signal feature of mechanical fault. Using theory of phase space reconstruction, simulating fault signal of rotating machine was reconstructed. In order to let the phase space reconstruction adequately reflect the movement characteristics of the system, the time delay and embedding dimension are discussed emphatically. Based on what mentioned above, the authors calculated the Lyapunov exponent and the Lyapunov dimension. From the analysis and calculation on simulation of different fault signals, it showed that under different rotating machinery fault conditions, its Lyapunov dimension were significantly different, which verified that this nonlinear feature quantities were effective parameters for fault information and they were excellent parameters in terms of extraction and recognition of fault features.

Abstract: Measured vibration response signals are inevitably contaminated with noise originating from test environment as well as electronic devices. This situation often leads to serious difficulties in many applications as they require high-quality measured data. This paper presents a signal-noise separation method for measured impulsive response functions (IRFs) based on structured low rank approximation (SLRA). The proposed method was tested with a steel cantilever beam, which was subjected to impulsive excitation. Gabor transform was also employed to process measured signals. The results show that this method can give a reliable separation of signal and noise, which will enhance the accuracy of various applications that rely on measured signals.

Abstract: As to the random sonic fatigue problem of thin walled structure of aerospace flight vehicle, estimation method for fatigue life based on Von Mises stress peak probability density is investigated. Assuming that Von Mises stress process satisfies three-parameter Weibull distribution, the peak probability density function of Von Mises stress is derived through the threshold crossing analysis and the peak distribution analysis of stationary random process. According to the Miner linear cumulative damage theory, the method for estimating the fatigue life in the frequency domain is established with the Von Mises stress peak probability density function applied. As an example, an aero-engine Combustor liner is considered, using coupled Finite Element Method (FEM) and Boundary Element Method (BEM) method, the structure vibration response to limited bandwidth Gaussian white noise is calculated. Based on the results, fatigue life of the structure is estimated by using the proposed method. Further more, the influences of the probability density function which is characterized by three-parameter Weibull distribution and two-parameter Weibull distribution respectivily for Von Mises stress response of the Combustor liner structure subjected to random accoustic loadings are discussed.

Abstract: All actual vibration systems are nonlinear in character. For nonlinear vibration problems, IHB method is an effective definite quantitative method. The theoretical foundation of IHB method is amplitude incremental variational principle. In this paper, amplitude incremental complementary energy principle for nonlinear vibration is established.

Abstract: A new method had been proposed in this paper of fault diagnosis for rolling bearings based on multichannel vibration signals and QPCA-SVM-based method. The vibration signals were obtained by some multi-sensors with three channels X, Y, Z, that were orthogonal axes. The three orthogonal axes signals were constructed a pure quaternion sequences as samples for processing. The pure quaternion sequences data set was processed by quaternion principle components analysis (QPCA) for feature extraction, and then combined with pattern recognition tools support vector machine (SVM) for classifying some faults patterns. The experimental results indicated its efficiency, and it provided a method for fault diagnosis on multichannel vibration signals.

Abstract: Wavelet transform has been widely used for the vibration signal based rolling element bearing fault detection. However, the problem of aliasing inhering in discrete wavelet transform restricts its further application in this field. To overcome this deficiency, a novel fault detection method for roll element bearing using redundant second generation wavelet packet transform (RSGWPT) is proposed. Because of the absence of the downsampling and upsampling operations in the redundant wavelet transform, the aliasing in each subband signal is alleviated. Consequently, the signal in each subband can be characterized by the extracted features more effectively. The proposed method is applied to analyze the vibration signal measured from a faulty bearing. Testing results confirm that the proposed method is effective in extracting weak fault feature from a complex background.