Abstract: The conventional modal methods become inefficient when expanded to the high frequency region. This leads to a large number of degrees of freedom (DOF) even for one-dimension structures. Meanwhile, a short computational time is also the requirement of on-line structural health monitoring. This paper presented an application of B-spline wavelet on interval (BSWI) finite element for one-dimension elastic wave propagation problems. By using central difference method in time domain, numerical results involving wave propagations in crack free rod and beam were obtained and compared with results calculated by classical finite element method. Numerical examples validated the good performance of BSWI. BSWI could provide a accurate and efficient solution for wave propagation problems. The proposed method provides a good reference for structural health monitoring.
Abstract: In this paper, the influence of turbulence integral scale to buffeting responses of long-span bridge is analyzed by adopting 2-D buffeting theory. One cable-stayed bridge and one suspension bridge are selected as analysis object. Buffeting responses are calculated under two different wind speeds and different size of turbulence integral scales, which range from 10m to 80m in this paper. The numerical results show that buffeting responses do not change with turbulence integral scale linearly and when turbulence integral scale increases to one value, buffeting responses reach a peak. In addition, turbulence integral scale corresponding to peak value of buffeting responses rise with growth of wind speed.
Abstract: In order to study the dynamic response of the asphalt pavement under vehicle random stimulation, the random vibration model of vehicles and the mathematic model of pavement dynamic response in which the base and surface are all viscoelasticity are established respectively. The analytical solution of the stochastic response for the pavement is deduced. The stochastic load acted on the pavement can be gotten by the mathematic model of the vehicle vibration. The numeral feature functions of the random response, such as even function, time-space correlation function, time correlation function and mean square function, are obtained by the analytical solution. The paper provides a theory method for studying the random response of the asphalt pavement.
Abstract: The hysteresis dynamic behavior of metal rubber mathematically modeled with a practical method is studied, and the method of parameter separated identification is presented with details. Parameters of the model are identified with the test data of metal rubber, from which the theoretical loops are reconstructed, and the mechanism of the nonlinear damping behavior of the metal rubber is investigated. The theoretical loops and the experimental one are close to each other with satisfactory accuracy. The result shows that with the simple mathematical form and the satisfactory precision, the mixed damping model can be used effectively in practical engineering. This study provides a practical and effective method in modeling and the parameter identification of the metal rubber isolator.
Abstract: The vibration control effect due to blocking mass on vibration transmission of single force excited structure is analyzed by adopting mechanical impedance method. Take the ring ribs cylindrical shell as research object, and simplify it as a mass-spring-damping system. The mechanical impedance of the whole structure is calculated by general commercial software MSC/NASTRAN, and then the vibration control effective and ineffective frequency band of any given mass was discussed. By comparing the vibration control effect calculated by general commercial software (finite element method) and mechanical impedance method, it is proved that mechanical impedance method is effective in analyzing the vibration control effect due to blocking mass.
Abstract: The electron beam stability is one of the most important requirements for the Shanghai Synchrotron Radiation Facility (SSRF), whose ground vibration is much larger than other light source for softer soil and deeper rock. This paper concentrates on the attenuation of the ground vibration, especially induced by the nearby vehicles. The result indicates that the variation of the ground-vibration amplitude is in a good accordance with the vehicle-number distribution, and the SSRF foundation achieves an obvious attenuation effect since it can attenuating more than 80% vibration induced by the vehicles nearby, which is mainly due to the slab and piles of the foundation. In order to achieve the design criterion, the vehicles with weights equal to or heavier than 10 ton should be prohibited to pass through the nearby roads.
Abstract: The results of an experimental investigations on the natural characteristics of tuned bladed disk and forced dynamic responses of mistuned bladed disks are reported. Three experimental bladed disks are discussed: a tuned specimen of periodic symmetry with 12-blades which are nominally identical, and two mistuned specimens, which feature small blade-to-blade variations by adding slight blocks to blade tips. All the specimens are subject to travelling wave excitation produced by piezo-electric actuators sticking on the root of blades. The primary objective of this experiment is to observe the natural characteristics of tuned bladed disk, and to research the impact of mistuning on the forced response blade amplitude magnification. Analytical predictions about the blade amplitude magnification factor are verified by the experimental results.
Abstract: Finite element model of the elbow interiorly impacted by flat-nosed missile was established using ANSYS/LS-DYNA. The Cowper-Symonds model was adopted. The rupture strain failure criterion was used to define the failure process. Numerical values were compared with experimental values obtained from the literature and the reliability of model was validated. The penetration failure mode of the elbow was analyzed. Factors of the critical rupture kinetic energy Er were acquired. It can be seen that the penetration failure mode is plugging induced by the extrusion and scraping dominated of axis stress. The effect of Do on Er can be neglected. Er increases with the increase of t/Do, Dm/t and R/Do when the missile mass m is invariable. The effect of m on Er should consider the factors of m and critical rupture velocity Vr.
Abstract: When boundary element (BE) was coarse, the general Gauss quadrature of Helmholtz integral equation (HIE) on it was not accurate. A mesh-less refined integral algorithm (RIA) of BEM was used to overcome this problem. Then RIA coupled with FEM/CFD was applied to predict submarine propeller excited hull underwater noise. The thrust and torque excitations of propeller simulated via CFD were loaded on to submarine respectively to calculate the acoustic response, and the sound power and main peak frequencies were obtained. Results show that, thrust mainly excites submarine axial mode and high sound area appears at the two conical-type ends, and torque mainly excites circumferential mode and high sound area appears at the broadside of cylindrical section, but with rather smaller sound power and radiation efficiency than the former. So, main attention should be focused on thrust excitation when perform the sound radiation reduction of submarine that propeller excited.
Keywords: Submarine, Propeller excitation, Refined integral algorithm, Vibro-acoustic, CFD/FEM.