Authors: Slawomir Banaszek
Abstract: The paper presents the course and results of crack propagation simulation research. The object taken into account is a large power turbo-set rotor. The computer code system NLDW is presented. It uses a non-linear model of journal bearings, and well known crack model. Crack depth is marked by a crack coefficient. It is shown the crack generates a coupled forms of lateral, axial and torsional vibrations in multi-support rotor. Their intensity depends on the axial and circumferential crack location on the shaft. The attempt at pointing a proper diagnostic indicator for crack detection in large rotating machine is made according to obtained results.
337
Authors: Zhen Qing Wang, Ji Bin Wang, Wen Yan Liang, Juan Su
Abstract: The viscosity of material is considered at propagating crack-tip. Under the assumption
that the artificial viscosity coefficient is in inverse proportion to the power law of the plastic strain
rate, an elastic-viscoplastic asymptotic analysis is carried out for moving crack-tip fields in
power-hardening materials under plane-strain condition. A continuous solution is obtained
containing no discontinuities. The variations of the numerical solution are discussed for mode I
crack according to each parameter. It is shown that stress and strain both possess exponential
singularity. The elasticity, plasticity and viscosity of material at the crack-tip only can be matched
reasonably under linear-hardening condition. The tip field contains no elastic unloading zone for
mode I crack.
817
Authors: Wei Wei Zhang, Zhi Hua Wang, Hong Wei Ma
Abstract: The objective of this study is to show the potential of the crack detection method based on Wavelet Packet Transform (WPT), which is depending on the response at a single point on a beam subject to moving load. In this paper, an ANSYS model of a cracked beam is established. The moving load is transient analyzed by shifting the point of the concentrated force. The response at mid-span of the beam is calculated and wavelet packet transformed. The crack on the beam can be found by the abnormal signal in WPT branches. The size is also estimated by a defined damage index (Dindex) which relates to the energy of the abnormal signal. Finally, the effects of both crack location and wavelet selection on Dindex are discussed in detail.
285
Authors: Zhi Ping Yin, Jiong Zhang, Jin Guo, Qi Qing Huang
Abstract: The finite element software ANSYS was employed to create a finite element model of the cracked wing beam integrated structure, and the stress field of the crack tip was got by the material nonlinearity (elastic-plastic) analysis method. Based on the maximum tensile stress theory criteria, the crack deflection angle was obtained. The crack deflection angles with different geometry parameters (crack length, wed thickness, the height-thickness ratio of the stringer, cross-sectional area, and the location of the stringer) of the wing beam integrated structure were calculated and compared with each other. So the influences of the geometry parameters of the wing beam integrated structure on the crack deflection were studied. The crack deflection angles obtained in elastic analyzing and elastic-plastic analyzing were compared to investigate the effects of the material property on the crack deflection angle.
101
Authors: Fu Ze Xu, Xue Jun Li, Guang Bin Wang, Da Lian Yang
Abstract: It is common for the imbalance-crack coupling fault in rotating machinery, while the crack information is often overshadowed by unbalanced fault information, which is difficult to extract the crack signal. In order to extract the crack signal of the imbalance-crack coupling fault, and realize the fault diagnosis, the paper mainly analyzes its mechanical properties, and then use wavelet packet to de-nosing, decomposing and reconstructing the acquisition of vibration acceleration signal, and then analyzing the characteristics of frequency domain of the fault signal by using the energy spectrum. So the experiment proved that analyze and dispose the acquisition of the fault signal by using the method of the energy spectrum and the wavelet packet, which can effectively distinguish between the crack signal and unbalanced signals in imbalance-crack coupling faults .It also can provide some reference for the diagnosis and prevention for such fault.
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