Papers by Keyword: Vertical Vibration

Abstract: Ride comfort is a reference point in evaluating the dynamic performance in railway vehicles. There are more methods to assess the ride comfort, depending on the traffic details and the specific needs of a railway administration. This paper focuses on the comfort index methods, in accordance with UIC Leaflet 513 R and the standard of railway applications ENV 12299, and the ride Sperling’s method, formulated by Sperling. A correlation is drawn between the comfort indices corresponding to the two methods, based on the link between the comfort and the values of these indices. The comfort indices derived from the two methods by numerical simulations help with validating the fact that, in general, the velocity influences the vertical ride comfort, and, in particular, the position of the carbody critical points, from the perspective of the ride comfort.

Abstract: Tribological behaviour of polymer and hard coating films is complicated with bio-lubricant. Contacting and kinematic conditions of a knee joint when a person in running was simulated in the study. Substrates of specimens are Ti₆Al₄V and 316LVM stainless steel. Two kinds of polymer films, PCL-PEG-PCL and mPEG-PCL-mPEG, were used to simulate the tissue of cartilage. The silicon nitride film, SiN_xH_y prepared by PECVD, was used as a protecting film, and it’s thickness about 1000 nm under the polymer film. The testing device was developed, upper specimen is rotated reversely and the lower one is moved linearly forward and backward for 6 mm. A frequency vibration is applied under the lower specimen to simulate the vibration caused from walking, which is sated 2 Hz. Two torque meters are used for friction measurement in rotational and sliding directions. Experiments simulated vertical vibration, rotary and reciprocating motion. Comparing friction coefficient with different substrates with SiN_xH_y film, mixture of PCL-PEG-PCL and bovine serum can effectively decrease friction but useless for mPEG-PCL-mPEG. If adhesion of PCL-PEG-PCL polymer can be improved, it has potential in the application of artificial joint.

Abstract: The motion equation of the grinding cylinder is deduced, which is based on the dynamic analysis of the grinding cylinder of the ball mill coupled with vertical vibration. Numerical model of vertical vibration ball mill is built and used to study the motion of grinding cavity media and grinding efficiency. The simulation results show that the distribution status of the grinding media in each region is changed, the grinding fragmentation of the grinding media to the material is enhanced, and the efficiency of fine grinding is improved with the coupled vertical vibration in a ball mill.

Abstract: In this study, effects of vertical vibration have been explored by means of comparative trial . Twenty two college male students participated in this trial, they were randomly divided into control group and vibration group. The experiment lasted 9 weeks, 3 sessions each week.Test has been performed after and before trial. After analyzing the test outcome,the finding showed that Vibration and convention exercise both can significantly increase the absolute peak torque (extensors:t=-3.919,p=0.02<0.05,flexor:t=-4.839, p=0.001<0.05) and relative peak torque (extensors: t=-2.379,p=.020; flexor : t=-5.285,p=0.000) of knee joint. The vibration exercise is better than the convention exercise.

Abstract: In this paper, the vertical vibration influence on the surface velocity of a 5cSt silicone oil liquid bridge has been investigated numerically. The Navier-Stokes equations coupled with the energy conservation equation are solved on a staggered grid, and the two-phase surface is captured by using the mass conserving level set method. The present results indicate that the axial and radial surface velocities of the liquid bridge are suppressed by the external vertical vibration.

Abstract: Based on the Biots dynamic consolidation equation, the individual contributions of these two compression waves in vertical vibration of water-saturated soils are analyzed. The equation belong to displacements of solid skeleton is established by using the decoupling of dynamic equation which is combined with boundary conditions to derive an analytic solution about displacements of solid skeleton under the excitation of the individual contributions of these two waves. And then, displacements of pore fluid and pressure of pore water under the excitation of the individual contributions of these two waves are obtained on the basis of that analytic solution. The attenuation of these two types of compression waves influenced by pore permeability is examined and it should be mentioned that, the contribution of the second compression wave is the main consideration when permeability coefficient is large, on the contrary, the contribution of different compression wave should be considered on the different soil column height when permeability coefficient is small.

Abstract: A dynamic model of seven degree of freedom for the vertical vibration of stand rolls system in a cold tandem mill is developed by Kinematics Theory. According to the actual parameters of a factory six-roll cold rolling mill, the influence of natural frequency and modes for rolling process is analyzed. It finds that the third-order and the six-order natural frequency play a role key in vertical vibration system. Combined with energy distribution of each part and flexibility of the modes analysis for vertical vibration system, it can avoid resonance of rolling process and optimize the parameters of stand rolls system by adjusting structural size appropriately. The above mentioned results have provided a reference for further research on Kinematics and structural optimization of six-roll cold tandem mill.

Abstract: According to the chatter phenomenon of 3^rd stand of a steelworks six-roller tandem cold mill (TCM), vertical vibration of tandem cold mill was simplified to eight degrees of asymmetric freedom mass-spring system. Virtual prototype model on vertical vibration of tandem cold mill was established and natural frequencies and main vibration mode of mill were solved by using automatic dynamic analysis of mechanical systems in software ADAMS. The modal coordinates of main vibration mode of the mill were referred firstly and obtained; the maximal mode of vibration system was found and finally discovered the fifth-octave-mode chatter was the probable vibration of the mill.

Abstract: The vibration influence on the quality of strip for 2180mm six-high cold tandem rolling mill is discussed. The abnormal frequency of mill is analysis by spot examination. The methods of numerical computation and finite element method simulation by the ANSYS are adopted to set up dynamic model of six-high mill. At the same time, the natural frequency of mill and the response to mill at different excitation is calculated. Comparing the analysis results with the data from the experiment, the finite element models presented in the thesis were proved to be an efficient and valid way to simulate actual working conditions.

Abstract: Rolling process is a typical and complex nonlinear dynamic one which determined by the couple-interaction of different physical attribute movements. Different forms of dynamic response will be reacted by the external excitation on mill system, such as the fluctuation of the rolling force. The vertical vibration and the roller axial flexural deformation, among these dynamic responses, are the main factors which would affect the strip after rolling quality. In order to exactly describe the roll systems vertical vibration and the roller axial dynamic property, this article is focused on the mathematical modeling of the roll systems vertical vibration and the lateral flexural vibration. Take the situation, the roll systems vertical vibration and the lateral flexural vibration occur simultaneously, into account, the authors build the lateral coupling-dynamic model of the roll system. Using numerical simulation method, the authors analyze the interaction between the roll systems vertical vibration and lateral flexural vibration.