JVE International
Not a member yet
1200 research outputs found
Sort by
Numerical simulation of fluctuation pressure with liquid-filled pipes based on large eddy simulation method
Get PDFPipeline is an important part of mechanical system on ship. Fluctuation pressure produced on the pipe wall is a significant source of noise, and more and more scholars pay attention to it. In this paper, by using large eddy simulation and subgrid turbulence theory, pipeline fluctuation pressure simulation model is established, and influence of flow velocity, wall roughness and step offset of pipeline connection on pipe fluctuation pressure are studied. This provides theoretical guidance for low-noise installation and maintenance of ship piping system
Automated wavelet-based damage identification in sandwich structures using modal curvatures
Get PDFRecently, damage assessment of composite structures being in operation has been one of crucial problems in industries such as aircraft, aerospace, automotive, etc. Following this, rapid development of non-destructive testing methods has been observed over the last decades. One of the promising approaches is vibration-based one, which in general is based on identification of a damage using singularities in modal shapes of vibration. The identification procedure requires application of advanced signal processing techniques, where the wavelet transform is used the most commonly. Due to the high sensitivity of wavelet-based approach to changes of parameters of an analysis, e.g. a type of applied wavelet and its order, it was decided to develop an algorithm, which allows automating this process by using multi-objective meta-optimization of the mentioned parameters. The presented approach allows selecting optimal parameters for wavelet-based damage identification procedure without neither a priori knowledge on values of wavelet parameters, nor the parameters of an optimization algorithm. The proposed approach was tested on composite sandwich structures with damaged core as well as damaged face sheets. Obtained results confirm the effectiveness of automated damage identification mainly in the context of the high convergence to the optimal solution
Optimization of passive constrained layer damping (PCLD) treatments for vibration reduction
Get PDFAn efficient method to reduce the frequency averaged transverse vibration level of a plate by optimizing the position of attached passive constrained layer damping PCLD is presented. This method uses a multilayer anisotropic plate model which is an equivalent single layer plate model (ESL) where transverse shear stresses and displacements are continuous at each layer’s interfaces. Hence, for a laminate composed of an arbitrary number of layers, all the quantities are related to those of the first layer. The optimization process is based on the use of the ESL plate model combined with the genetic algorithm (GA) and Latin Hypercube Sampling (LHS) algorithm implemented in a Rayleigh-Ritz resolution program. The convergence acceleration of the method is achieved thanks to the combination of genetic algorithm and the use of the ESL plate model instead of a three-dimensional mesh that requires more computing resource
Adaptive vibration control of a nonlinear quarter car model with an electromagnetic active suspension
Get PDFThe main goal of the active suspension system used in a vehicle is reducing the vehicle vibration. In this study, an adaptive control approach is applied to a nonlinear quarter car model with an active suspension system. An electromagnetic actuator is used in the active suspension system. The attractive aspect of the applied control method is not required to both vehicle parameters and actuator parameters. Using Lyapunov based stability analysis; it is shown that all the signals in the closed loop system are bounded. Hence, the applied controller ensures the vibration reduction of the nonlinear quarter car model. The simulation results show that the applied adaptive controller provide a good ride comfort despite the parametric uncertainties while keeping suspension travel and tire deflection in acceptable limits
A new machinery diagnosis method based on complex bilateral spectrum
Get PDFIn view of the turbo molecular pump high-speed rotating parts, this paper presents a new machinery diagnosis method based on complex bilateral spectrum. At first, the vertical and horizontal vibration signals are directly combined into complex signals in time-domain; and then the complex bilateral spectrum is obtained by fast Fourier transform (FFT). Furthermore, the holospectrum, which can fast find machinery faults, can be obtained using the amplitude and phase at some special frequencies. At the same time, the equivalence of holospectrum technique and the proposed method is verified. Finally, a case study shows the effectiveness of the proposed method
Axial vibration analysis of cracked nanorods with arbitrary boundary conditions
Get PDFThe axial vibration of cracked nanorods (carbon nanotubes) with arbitrary boundary conditions is studied. The nonlocal elasticity theory is used, and the crack severity is modeled by an axial spring representing the discontinuity in the axial displacement. The present model is set up by dividing the nanorod into two segments connected by an axial spring located at the cracked section. The axial displacement functions are sought as the combination of two Fourier sine series and Stokes’ transformation. Vibration frequencies of a nanorod for variant crack positions under different boundary conditions are calculated by means of the proposed method. The purpose of this study is mainly to present a general analytical method for the dynamical analysis of cracked nanorods with arbitrary boundary conditions (rigid or restrained) rather than to investigate a specific problem
A combined method of thermal and vibratory stress relief
Get PDFA combined method of thermal and vibratory stress relief (TVSR) to extend effects of vibratory stress relief (VSR) is presented. TVSR was implemented by imposing vibratory load on a workpiece at an assisted temperature. Residual stresses before and after treatment were measured using the modified layer removal method (MLRM) to evaluate the stress variations. A finite element (FE) model was developed to investigate and compare TVSR and VSR treatment on workpieces cut from a 7075 aluminum alloy plate. Thermal influence on TVSR equipment and vibratory treatment of the workpiece was analyzed using this model. Experiments were conducted to validate simulation results. Significant residual stress relief was observed in TVSR, however, effects of VSR were limited
The stability of the tethered trailer and its control
Get PDFTethered trailer vehicle is a nonprofessional tractor that drags an unpowered vehicle with rope. In this paper, a nonlinear dynamic model of the tractor is developed. With the Dugoff’s tire model. A new nonlinear tethered tractor-trailer model is created to simulate critical parameters. A trailer front-wheel steering feedback control strategy is derived in order to improve stability and trajectory tracking feature the comparison of the simulation results for tension of the traction rope, the trajectory following resistance, and the handling stability clearly demonstrates the efficacy of the proposed control strategy
Adaptive algorithm with variable step size for numerical analysis on nonlinear fatigue damage accumulation of steel bridge
Get PDFAn adaptive algorithm with variable step size was firstly established in the paper in order to predict fatigue life of steel bridge welded components accurately and efficiently. The coupled damage constitutive model is developed within ABAQUS through user defined material subroutines to introduce damage revolving formulation into the fatigue damage analysis and the fatigue damage evolution process of the steel bridge components was finally studied. It is demonstrated that the adaptive variable step size algorithm for predicting fatigue life of steel bridge components is scientific and effective. Secondary development based on commercial software is more convenient and suitable to explore the mechanism of local damage accumulation process of various structures. The efficiency of the adaptive algorithm is not so high when the material damage is described by the linear Miller criterion, while it can effectively improve the calculation speed when the nonlinear Lemaitre damage evolution criterion is applied
Vibration signal simulation of planetary gearbox based on motion process modeling
Get PDFIn planetary gearbox, multiple gear pair meshing with each other and the vibration transmission paths from gear meshing points to the fixed sensors are time-varying. Therefore, fault diagnosis of the planetary gearbox is more difficult compared to that of fixed-axis gearbox, in which the vibration signal simulation models are very important. This paper constructs vibration signal models based on motion process modeling. This kind of modeling method is easier to understand compare with other methods which mainly based on the theory or physical laws behind the phenomena. The modeling process was presented in a step-by-step procedure according to the motion process of planetary gearbox. Frequency analysis was also implemented and comprehensive diagram was shown to help understand the result