Improving Methods For Vibration And Noise Control Of The Constrained Layer Damping Wheel

The wheel noise is the main source of the railway noise. Therefore, it is particularly important to develop ways for reducing the level of vibration and noise of the wheel. In this dissertation, the method for vibration and noise control of constrained layer damping wheel is investigated and then two effective methods for vibration and noise control are presented:the method of segmenting the constrained layer damping treatments and the method of attaching 'Acoustic black hole'(ABH) treatments. The first method based upon segmenting the constrained layer damping material in special position, which can redistribute the shear deformation of the damping layer. The segmentation can enhance the damping capability and reduce the level of vibration and noise of the wheel. For the second method, the ABH is introduced to absorb the vibrational energy of the basic wheel and dissipate it. Moreover, special cuts are introduced to the ABH aiming at further reducing the vibration of the wheel. The main contents are as follows:(1) The parameter analysis and numerical model of the constrained layer damping wheel. The damping capability of the constrained layer damping treatment is associated with the thicknesses of the damping and constraining layers. Therefore, it is of great importance to analyze the effects of the thicknesses of the damping and constraining layers on reducing the vibration of the wheel. The commercial software ABAQUS is used to construct the finite element model of the wheel. Then the structural loss factor is obtained to estimate the damping capability of the constrained layer damping wheel. The effects of the thicknesses of the damping and constraining layers on the structural loss factor are investigated by the harmonic response analysis. The results show that the structural loss factor improves with the increase of the thickness of the constraining layer in the whole frequency range. With the increase of the thickness of the damping layer, the structural loss factor improves in the high frequency range, while on the contrary the structural loss factor goes down in the low frequency range. The damping capability of the wheel can reach a better level when the thicknesses of the damping and constraining layers are both 2mm after a comprehensive analysis.(2) The improving method of damping capability through segmenting constrained layer damping treatment. The damping capability of the constrained layer damping treatment is based on the shear deformation of the damping layer. Segmenting the constrained layer damping material is an effective method in increasing the shear deformation of the damping layer, which can improve the damping capability of the wheel. The effects of the circular and radial cuts on the damping performance of the wheel are presented. The results show that a reasonable distribution of the cuts can effectively reduce the vibration amplitude value of the wheel. The effect of the circular cut is not that significant in the whole frequency range thought it restrains the vibration in one or two modes. The structural loss factor can be increased by 10%-75% in the high frequency range by the radial cuts. And the vibration reduction of the resonance peaks is about 2-5dB when the frequency is higher than 2000Hz, which is about 37%-68% of the amplitude decreased.(3) The improving method of damping capability based on the ABH. The capability of the ABH in reducing the structural vibration is dependent on the parameters of the ABH. Then it is very important to investigate the effects of the parameters on the vibration reduction. And it is an effective method for introducing the ABH to the standard wheel to restrain the vibration of the wheel. The finite element model of a plate embedded with one acoustic black hole is constructed. The effects of the curvature and size of the ABH and the size of the attached damping layer on the restraint of the vibration are discussed. Then the ABH with constrained layer damping treatment is applied to the wheel and the model is analyzed by the harmonic response analysis. The results show that the wheel with ABH almost has the same effect as the constrained layer damping wheel on reducing the vibration and special cuts on the ABH can further restrain the vibration of the wheel. Comparing to the optimal result of the constrained layer damping wheel with segments, the resonance peaks of the segmented ABH wheel is about l-4dB reduced, which is about 21%-60% of the amplitude decreased.