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Research on active control strategy of vibration in complex environment
Get PDFFxLMS algorithm has been widely used in active vibration control field theoretically. This paper is aimed at the complex situations in actual environment including interference and occasional divergence due to algorithm. Firstly the effects to control process and result caused by those situations are analyzed, then select different means based on different characteristics of the effects to deal with them, and integrate all those means to derive a new optimal control strategy which is suitable to actual applications. The experiment shows that the improved control strategy can response effectively different occasional situations without any weakness of normal control, and it can promote the practical application ability of the algorithm and is able to adapt to complex environments in active vibration control
Damage identification using singular value feature of continuous wavelet coefficients
Get PDFA hybrid soft computing approach is developed with the aim of identifying multiple damage in beam-type structures. This approach is formulated based on integration of two renowned soft computing methods: a wavelet transform and a singular value decomposition. The integration features the creation of a sophisticated damage indicator: mode shape’ continuous wavelet transform-singular value decomposition component (MWSC).The MWSC has inherent capabilities of immunity to noise and sensitivity to multiple damage of beam-like structures. The effectiveness of the MWSC is numerically verified by identifying multiple cracks in cantilever beams, with particular emphasis on its ability of locating multiple damages in noisy environments
Topology optimization for minimizing frequency response of constrained layer damping plates
Get PDFThis paper presents a topology optimization method to design the optimal layout of Constrained Layer Damping (CLD) material in structures subjected to harmonic excitations or stationary random excitations. A finite element model is used to describe the dynamic performances of the CLD structure. Since energy dissipation arises only from the viscoelastic (VEM) layer, the modulus of elasticity of the VEM layer is complex. The complex mode superposition method is employed to calculate the steady-state response of the CLD structure under harmonic excitations. According to Pseudo-Excitation Method (PEM), the vibration analysis of stationary stochastic excitations can be transformed to the analysis of harmonic excitations. The minimization of frequency response at specified one point or several points in structures are selected as optimization objective. The Solid Isotropic Material with Penalization (SIMP) method is adopted to interpolate the CLD material. The sensitivity is derived by means of the adjoint variable method which is more efficient than the direct variable method. The Method of Moving Asymptote (MMA) is used to search the optimal layout of CLD material on structures. Numerical examples are given to illustrate the efficiency and verification of the proposed approach
Optimum design of a partially-treated MR-fluid sandwich plate
Get PDFThe present study concerns with dynamic characterization and optimal design of a partially treated magneto-rheological (MR) sandwich plate. An aluminum sandwich plate, partially treated with MR fluid (MRF 132DG) was fabricated for dynamic characterization in the laboratory. The MR-filled cavity in the plate was subjected to a uniform magnetic flux using two permanent magnets located at top and bottom of the structure. The dynamic response characteristics of the sandwich plate were experimentally obtained under harmonic force excitations. A finite element model of the partially-treated MR sandwich plate was developed using classical plate theory considering the effect of slippage between the top and bottom layers. The validity of the finite element model was demonstrated by comparing the theoretical results with those of the experiment. An optimization problem was subsequently formulated and solved using genetic algorithm (GA) to identify optimal locations for the MR fluid treatments for realizing maximum variations in stiffness and damping properties of the structure corresponding to the lower three modes of flexural vibration, individually and simultaneously, in response to the applied magnetic field. The effect of shear deformation on the vibration properties of the partially treated sandwich plate was particularly highlighted. The results suggest that the MR fluid treatments can significantly alter the stiffness and damping properties of the sandwich structure under noticeable shear strain, while a partial treatment could yield the changes in stiffness and damping comparable to those of a fully-treated plate
Development of spherical ultrasonic motor for space. Evaluations of durability under high temperature environment
Get PDFThe purpose of this research is to develop the spherical ultrasonic motor (SUSM) for space. The SUSM is a small multi-DOF motor. The various performances are requested of the motor for space. The experiments under the high temperature environment were carried out to check the durability to the radiant heat from the sun this time. Our experimental results showed that SUSM for space also maintains the drive performance under the high temperature environment. The material of piezoelectric elements and adhesives which influence the performances of SUSM for space will be reported in detail
An experiment to assess vibration reduction ability of the rubber floating-slab tracks with different supporting forms
Get PDFThe rubber floating-slab track is one of the best methods to isolate vibration induced by the interaction of the train and the rails. In order to improve its vibration reduction ability, three kinds of supporting forms, i.e. full-surface supporting, linear supporting and point-like supporting, were discussed by laboratory tests. Through time history analysis and frequency spectrum analysis, we found that the linear supporting form and the point-like supporting form have the smaller first resonant frequency than the full-surface supporting form, which is induced by the weakened supporting stiffness. Because of this reason, the maximum values of vibration acceleration of the floating slab for the linear supporting form and the point-like supporting form increase in the time domain and the frequency domain. However, the point-like supporting form has the smallest transfer ratio of vibration acceleration from the floating slab to the tunnel wall compared with the linear supporting form and the full-surface supporting form
Dynamics of the formation of thin LaNbO4 films using magnetron sputtering
Get PDFDoped lanthanum niobate thin films were deposited using magnetron sputtering technique. W and Mg cathodes were used for doping LaNbO4 thin films. Thin films were deposited on two types of substrates: amorphous optical quartz (SiO2) and polycrystalline Alloy 600 (Ni-Cr-Fe). The structural and morphological analysis was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), atomic force microscope (AFM). The nonequilibrum growth of the thin films and the nonlinear dynamics of the sputtered atoms and their oxides is observed. XRD analysis revealed that Mg promotes crystallite formation in La1-xMgxNbO4 thin films and W inhibits crystallite formation in LaNb1-xWxO4 thin films. EDS analysis showed that La1-xMgxNbO4 and LaNb1-xWxO4 thin films are nonstoichiometric. They have deficit or excess oxygen and Nb (compared to lanthanum). It was noticed that the nonstoichiometry has influence on the morphology of thin films. The cross section of formed thin films analysis showed that grains or fibers are not visible in the thin films with excess oxygen concentration and thin films with deficit of oxygen has fiber type structure. Oxygen concentration also influences the surface morphology. The roughness of the surface increases (0.2 nm ÷ 0.3 nm for La1-xMgxNbO4 and 0.2nm ÷ 0.8 nm for LaNb1-xWxO4) with decreasing oxygen concentration
Analysis on fatigue life of a certain gear transmission system
Get PDFAs the certain gear transmission system becomes more complex and precise, the flexibility of shaft will influence the dynamic response of system. Build the rigid model of gear system and the finite element model of the gear shaft. Establish the rigid-flex coupling model with the virtual prototype technology, simulation and make a contrast between rigid model and rigid-flex model. Find the influence of shaft flexibility on the dynamic response of gear system, which can enhance the accuracy rating of the model. With the increase of the bearing interval, the impact of coupling will become severely. Furthermore, we analysis the influencing factor of the fatigue life of the shaft. Analysis the law of the fatigue life in the different d/D, the result can provide a reference for the optimum structural design of the gear transmission system
Bearing fault diagnosis based on active learning and random forest
Get PDFBearing plays an important role in rotating machineries and has received increasing attention in diagnosis of its faults accurately. This paper proposes a fault diagnosis approach exploiting active learning (AL) based on random forest (RF), which can perform accurate bearing fault diagnosis with most valuable samples. First, feature vectors are obtained by empirical mode decomposition (EMD) process for original vibration signals and selected as input of the system. Second, samples with highest uncertainty are selected through AL and added to the training set to train RF classifier. Finally, trained RF is employed to perform classification for bearing faults with testing set. Experimental results demonstrate that the proposed approach can effectively and accurately identify typical bearing faults
The untrenched pipe’s stability analysis on the seabed under wave loadings using dynamic method
Get PDFThe on-bottom stability of submarine pipeline is a key problem of submarine pipeline design. The key issue is to simulate the interaction among wave, pipe and soil. The factors such as contact effect, frictional coefficient between pipe and soil, pipe’s penetration, the impact of yield stress are considered. Also, the results show that the computation of the pipe/soil interaction may provide a helpful tool for the engineering practice of pipeline on-bottom stability design