Applied Mechanics and Materials Vols. 105-107

Abstract: The tread wear would change the wheel/rail relation and seriously affect the railway vehicle dynamic behaviors. After testing the several EMUs under running ,this paper not only analyses the discipline of tread wear, but also computers the influence on wheel/rail contact geometry by a program devopled in Matlab/GUI. A MBS model of trailer of EMUs is constructed, including the model of passagers. The dynamic performance of EMUs and riding comfort are compared among the standard, worn and turned tread profile. We draw the following conclusions：Tread profile after running for a long time without turning would emerge harmful concave worn；The unsymmetrical wheel/rail contact would increame the risk of derailment and debase passengers comfort of EMUs；After turning , the dynamic performance of EMUs can be improved.

Abstract: The dynamics characteristic of aerial towed cable has been investigated with many models. Because of the coupling between the components of the towed cable system, the dynamics of the towed cable is complex and nonlinear. Though the aerodynamic performances of cable is studied for a long time, the results are quiet different with researchers. The ideal method to obtain the aerodynamic forces is to simulate the flow structure around the towed cable.The purposes of this paper are to simulate the flow field of the towed cable with the different inclined angles by using Large Eddy Simulation (LES) with sub-grid scale model of Smagorinsky-Lily and to study the variation of the aerodynamic forces and its influences on flow structure. The results show that the LES can predict the flow structure of the cable reasonably.

Abstract: The exact bending solutions of moderately thick rectangular plates with two opposite sides simply supported are derived based on the symplectic geometry method. The basic equations for the plates are transferred into Hamilton canonical equations. Then the whole state variables are separated. According to the method of eigenfunction expansion in the symplectic geometry, the exact bending solutions of the plates are obtained. Since only the basic elasticity equations of the plates are used and there is no need to select the deformation functions arbitrarily, the approach utilized is completely reasonable.

Abstract: Gantry bucket wheel stacker-reclaimer belongs to large complex steel structure. Once it is instability at the working time that will make a large accident. So we have to calculate its strength and stiffness. But its connection and the working condition are very complex. And the size of the model is so large which leads to debase the calculation efficiency. This paper use Pro/E software to create the model. And use Pro/Mechanical to make a finite element analysis. Through the properly simplified the model, we can increase the calculation efficiency. During the calculation result we find that the Pulley yoke, Rigid leg and Flexible leg appear big stress areas. We will give an optimization design for the irrational place and high stress areas. So that to improve the Gantry bucket wheel stacker-reclaimer on-site safety. And provide a certain reference for the subsequent design and improvement.

Abstract: Among structural health monitoring (SHM) techniques, Lamb waves is frequently used as diagnostic tools to detect damage in plate-like structures. Temperature variation can cause significant changes in guided-wave propagation and transduction for SHM. In this paper, controlled experiments examine changes in Lamb wave propagation and transduction using PZT-5A piezoelectric wafers under quasi-statically varying temperature (from 5°C to 60°C). The baseline selection method and baseline signal stretch method are used to compensate the temperature influence on Lamb wave propagation. The results of the experiments demonstrate the effectiveness of the temperature compensation approach and the simulated damage on the plate can be detected effectively under elevated temperatures environment.

Abstract: 7 geotechnical centrifuge model tests for buried explosion in dry sand were investigated by using 450 g-t geotechnical centrifuge apparatus. Blast wave effect on apparatus and propagation laws in dry sand were studied under the conditions of different explosive charges and different centrifuge acceleration levels. 11 accelerometers were buried around the explosives for recording the acceleration response in sand. Other 1 accelerometer was installed on the centrifuge arm to monitor blast wave effect on centrifuge apparatus. The results demonstrate that: The effect of blast wave on centrifuge apparatus can be ignored. The peak acceleration is a power increasing function of the acceleration level. An empirical relation of exponent can be found between the proportional peak acceleration and the proportional distance.

Abstract: On the basis of systematic study on the existing measurement methods of multi-degrees-of-freedom, A real-time monitoring method for five-degrees-of-freedom of the extruder’s moving parts was proposed based on laser beam measurement reference and machine vision. Simultaneously measuring multi-degrees-of-freedom is implemented by two-collimated laser beam and three-point measurement in this method, laser dispersion technology is used for several measuring points using the same basis simultaneously, the baseline errors are initial adjusted and real-time monitored, the method of machine vision is used for precise extraction of the position signals. Position signals are collected and selected by a Charge Coupled Device (CCD) sensor and a high speed Digital Signal Processor (DSP), long-distance propagation and reconciliation of multi-channel data is implemented by an industrial Ethernet. Experiments indicated the method is effective and steady.

Abstract: A method for analyzing wind-induced vibration and its control of transmission tower-line system in mountainous area is described. The method is applied to a real transmission line containing two self-supporting steel angle towers, 3 spans of conductors and ground lines together with insulators. Analyses are conducted for the out-of-plane wind direction, and the fluctuating wind load on tower-line system is simulated by harmony superposition method and davenport spectrum. The numerical results indicate that the wind-induced response and its control effect are mainly related to the stiffness of the towers, rather than the mounting height or the spans of the power lines. At the same time, viscoelastic dampers fixed on the main members can suppress the wind-induced displacement of the towers effectively.

Abstract: The vibration system of a geophysical prospecting car has three main features: the starting frequency is low (from 1Hz); the load is large (a single spring bears more than 3667Kg of load); the vibration signal is mixed with stochastic components. In this paper, models of an improved passive vibration isolation system and a semi-active fuzzy vibration control system of a geophysical prospecting car frame are established and simulated respectively. In the semi-active fuzzy control system the stiffness of an air spring is adjusted, and at the same time the impact by damping changes on the system performance is also taken into account. In order to evaluate the effects, the displacement and acceleration of car frame and the dynamic load of air spring are taken to comparative analysis. The results indicate that the proposed semi-active scheme can effectively lower the damage from vibroseis to the body of the car.

Abstract: In this paper through to analyse the sensitivity of several modal parameters about the elastic modulus damage such as characteristic frequency, modal displacement, flexibility matrix and modal curvature , Combined with Fisher information matrix , got the sensitivity of modal parameters on different damage positions of bridge. Computational simulation of Jian Tiao bridge is implemented with this method to find Optimum sensor placement schemes of different parameters. And through the result of numerical analysis we know, flexibility matrix is the most sensitive parameter about damage of elastic modulus, modal sensitivity less than flexibility matrix, the third is frequency. Sensitivity of modal curvature is the dullest, its sensitivity only 1/300 than flexibility matrix. It have different sensor arrange schemes when use four different modal parameters, among them the sensitivity of flexibility matrix is highest.