Papers by Keyword: Damping Ratio

Abstract: Environment pollution and exhaustion of mineral resources aroused strongly research and development of fly ash utilization. As a kind of foundation treatment method, improved by fly ash is more and more used in highway, railway roadbed construction. With the increase of speed of vehicles and vehicle load, the influence of dynamic load on the subgrade has caused people's concern. In this paper, based on fly ash modified loess, dynamic property of modified fly ash loess is discussed through the dynamic triaxial test of the unsaturation disturbed loess. The effect of the dynamic elastic modulus and the damping ratio with different amount of fly ash loess is studied. The results show that the difference of dynamic properties in dynamic load and static load is large. It mainly presents the hysteresis quality and nonlinear relationship between dynamic stress and dynamic strain. And the dynamic elasticity modulus increases with fly ash mixed amount.

Abstract: Increasing consumption of the automobile make vehicle seat comfort characteristic paid more attention to. Damping performance as the third important factors is not allowed to ignore. A three freedom "human - seat" system model has been created for simulation. The result show that as the natural frequency f0 improved, the two resonance peak frequency of the system also improved, the growth of the first order resonance frequency is quite obvious, the second is less growth. And the higher the f0 the less change is. With the improvement of f0, the first order resonance peak to peak value obviously reduced, and the second order resonance peak to peak value increased. So, it is said that the higher the f0 the poor damping effect in high frequency area. The influence of ξ for the damping ratio of work frequency is not big, but the influence for the amplitude value is significant. Increase the natural frequency can make phase angle decreased when resonance, but the change of damping ratio, do not have obviously changes.

Abstract: Dynamic shear modulus ratios and damping ratios of soil are the parameter of indicating dynamic nonlinearity of soil, and the necessary parameter of seismic site analysis. The 372 pairs of soil samples’ dynamic nonlinear parameters, which were tested by dynamic tri-axial tests in about 40 the seismic safety evaluation reports of ocean oil platforms in the Bohai Sea, were collected and corrected. The dynamic shear modulus ratios and the damping ratios of various soil types with different depth in the Bohai seafloor were calculated and their statistical mean values were obtained. The statistical mean values are reasonable and are the important supplements in case that the tested soil samples are not enough in the Bohai Sea sites.

Abstract: An accelerometer is a micro- electromechanical device which can sensitive to acceleration . The sensing mechanism of accelerometer is that when accelerated , the mass moves in Z-axis, and the gap between parallel plates changed with the loads, which causes vary of the capacitance of the estimation. This paper presents a newly devel oped sensor for the conventional capacitive MEMS accelerometer in Z-axis . The principle of capacitive acceleration is based on the detection the change of capacitance which results from acceleration changes. The sensor is used for estimation of the size a nd loads variations for accelerometer. This paper has been focused on the design of the MEMS accelerometer and calculation of the major parameters of the sensor.

Abstract: The main purpose of the numerical simulation that described in this paper is to investigate the damping influence on vortex-induced vibration (VIV) system. By considering different damping ratios, the 1-dof vortex-induced vibration of a rigid cylinder with low mass ratio is investigated numerically by the RANS solver combined with SST turbulence model. Comparing of the simulation results that obtained under low damping ratio by J.S. Wang and experimental results which carried out by Williamson and Govardhan, it indicates that the computing model in this paper is reliable. In addition, by using our model we analyze the vibration under the other two damping ratios, including the corresponding amplitude response and frequency response. We observed significant frequency locking phenomenon under different damping conditions, and locking region decreases with increasing damping.

Abstract: It is necessary to test dynamics parameters of foundations at construction ground of large-size dynamic machine base. This paper elaborate the test technology and data processing methods on the basis of the block forced vibration test with engineering example, and test results are analyzed and discussed.

Abstract: The modal properties of carbon fiber woven fabric (with fiber orientation of 45°/-45°) / epoxy resin composites with different fiber volume fraction were studied by using single input and single output free vibration of cantilever beam hammering modal analysis method. The effect of different fiber volume fraction on the modal parameters of laminated composites was analyzed. The experimental results show that with the fiber volume fraction increasing, the natural frequency of laminated composites becomes larger and damping ratio becomes smaller. The fiber volume fraction smaller, the peak value of natural frequency becomes lower and the attenuating degree of acceleration amplitude becomes faster.

Abstract: A study on dynamic mechanical properties of carbon fiber plain woven fabric (with fiber orientation of 0°/90°) / epoxy resin laminated composites with different fiber volume fraction was carried out. The test method is single input single output free vibration of cantilever beam hammering modal analysis method. The effect of different fiber volume fraction on the modal parameters of laminated composites was analyzed. The experimental results show that with the fiber volume fraction increasing, the natural frequency of laminated composites becomes larger and damping ratio becomes smaller. The fiber volume fraction is greater, the peak value of natural frequency becomes higher and the attenuating degree of acceleration’ amplitude becomes slower.

Abstract: At the beginning,we used the ABAQUS to establish a two-dimensional finite element model of typical asphalt pavement, and analysised the changing axiom of road surface shearing stress under the half sine wave load. Also, we studied on the impact of damping ratio and the driving speed on shearing stress. Finally, by using SPSS13.0 software to compare the impact of speed, the surface layer material damping ratio, lower modulus ratio, the thickness of the surface layer and the thickness of the subbase. The results show that, to reduce the cracking damage caused by oversized shearing stress in asphalt pavement, we should first consider the damping ratio of surface layer material, and the most effective method is to use the road-building material of high damping ratio to prevent cracks, at the same time we should raise the driving speed.

Abstract: In this article, the authors identify the one built in 1998, eight-story structure of steel reinforced concrete body dynamic parameters, and discussed the soil - structure interaction on the identification results.In this study, an 8 degrees of freedom analytical model and the impact analysis model of soil-structure interaction to be established; through the analysis of microseismic observations, using non-parametric (transfer function and Random Decrement method) and parameter techniques (off-line system identification method, ARX :Auto-Regression with eXtra input) to identify the structure of the natural frequency, damping ratio and the story stiffness. Finally, in considering the soil-structure interaction cases, structural parameters were identification and compared the results to confirm the impact of soil-structure interaction.