Papers by Keyword: Damping

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Authors: Adrian Ioan Niculescu
Abstract: The paper presents a complex quarter car model obtained with ADAMS software, View module, useful in the first stage of suspension dimensioning and optimization.The model is equipped with compression and rebound stopper buffer and suspension trim corrector.The proposed quarter car model with two degrees of freedom (wheel and body) performs all these goals allowing changing:Geometrical elementsPosition of equilibrium, depending on vehicle load;Trim correction;Elastic and dissipative characteristics of the suspension and tire;Suspension stroke;Road profile, assessed either by simple or summation of harmonic functions or reproducing real roadsBuffers (for stroke limitation) position and characteristics;The models developed provide information on:Vertical stability assessed by vertical movements of the body and the longitudinal and transversal stability evaluated based on adherence characterized by wheel ground contact force and frequency of soil detachment wheel.Comfort assessed on the basis of body vertical acceleration and collision forces to the stroke ends.The body-road clearanceThe trim corrector efficiencyAll above performances evaluated function the road unevenness, acceleration, deceleration, turning regime.The damping characteristic is defined by damping forces at different speed for each strokes respectively one for rebound and other for compression.The contact force road-wheel is defined based tire rigidity law.The stopper buffer forces on rebound and compression are defined based each specific rigidity characteristics.The road excitation is realized with a function generator.The software allow the model evolution visualisation in real time, also generating the diagrams of displacements, forces, accelerations, speeds, for each elements or for relative evolution between diverse elements.The simulation was realized for unloaded and fully loaded car using a road generated by a sum of harmonic functions presented in equation (8).The excitation covers the specific frequencies area, being under the body frequencies up to the wheel proper frequencies.The realized ¼ car model, have reached the goal to evaluate the suspension trim correction advantages.The simulations confirm the trim corrector increases the suspension performances, thus for the analyzed case the trim corrector increase simultaneous:Body-ground clearance (evaluated by body higher increasing) between 18.5÷55.1 %Body stability (evaluated by maximal body displacement) between 9.8÷11.4 %Body comfort (evaluated by maximal body acceleration) between 3.4÷35.5 %Adherence (evaluated by maximal and RMS wheel-groundcontact force variation) between 7.0÷12.1 %Body and axles protection (evaluated by buffer strike force) between 10.8÷38.2 %
205
Authors: Bin Yang, A Lei Du
Abstract: A simplified mathematic model of hydro-pneumatic suspension was set up and the damping characteristic curve of hydro-pneumatic suspension was obtained accordingly. A analysis of the effect of diameter of hydraulic jar, velocity of piston, diameter of damping hole and check valve diameter on damping characteristic of hydro-pneumatic suspension was made. It showed that the major influence factors includes moving speed of piston, diameter of hydraulic jar and diameter of damping hole.
1129
Authors: Sumedh Mannar, Amarjot Singh, M.Sai Shankar
Abstract: The increasing requirement for harnessing nuclear power demands the development of innovative precautionary techniques for protection from radiation. The high energies of the particles emitted have to be moderated before they render damage to any material subjected to them. Besides using simple shielding material, electrostatic shielding by setting up opposing electric fields has been implemented towards charged radiation damping to date. This paper aims at presenting and analyzing a material-efficient protection technique against ionizing radiation by introducing a number of parallel capacitive metal foils in between layers of dielectric shielding material. This is the first paper to present a technique by making use of charged capacitive elements to set neutralization centers for incoming charged radiation in order to minimize the thickness of material used for equivalent radiation shielding. The increase in efficiency of the shielding unit in reducing the net energy of radiation by the introduction of charged capacitive foils is experimentally observed.
3834
Authors: Xue Ren Wang, Xu Hong Miao, Xin Liu, Di Jia, De Jin Qian
Abstract: It is much valuable to find a method for predicting the middle and high acoustic characteristics of big and complex structures such as ships and airplanes. Impact of the ring frequency and the damping on the vibration transmission is discussed firstly. Then the feasibility of the model simplification method for big and complex structures whose acoustic characteristics will be predicted is analyzed. At last, the simplification method was applied to predict the middle and high frequency sound radiation of the double complex cylindrical structures. Numerical results showed that the proposed method has the same accuracy as the conventional finite element method and boundary element method, and can be applied to deal with engineering problems.
326
Authors: Djamel Bensahal, Mohamed Nadir Amrane, Mounir Kharoubi
Abstract: The paper presents an analysis of the damping of laminated beams with four different stacking sequences. The experimental investigation was conducted using tensile cyclic tests for different laminates studied. The impulse technique was chosen to perform modal analysis of the ease of implementation and quickness of the test. The numerical analysis is performed by the finite element method using beam element. The difference between strain energies for both cases damaged and undamaged are calculated by the finite element method. The structural damping of the different beams is evaluated from these energies. The decrease in frequency for different rates of loading shows the loss of stiffness for all materials studied.
33
Authors: Fang Jia, Fan Cheng Zhang
Abstract: In present study, the mechanical properties of disc-spring vibration isolator with viscous dampers is investigated by finite element analysis (FEA) and experiments. The result of FEA and static test reveals that frictional damping has significant effect on the static stiffness of combination vibration isolator, the ability to strengthen loading stiffness and lower unloading stiffness. However viscous damper has no effect on the static mechanical properties. The dynamic experiment shows that the dynamic performance of combination vibration isolator can be greatly improved with viscous dampers. Viscous dampers have little effect on dynamic stiffness of vibration isolator, but significant effect on damping characteristics. These conclusions are of significant importance in the analysis and design of combination disc-spring vibration isolators.
454
Authors: She Miao Qi, Y.S. Ho, Hai Peng Geng, Lie Yu
Abstract: A general method is developed to deal with the compressibility of air film and to predict the linear dynamic stiffness and damping coefficients of air-lubricated bearings over the whole range of frequency. Numerical results reveal that both stiffness and damping coefficients are functions of not only the static parameters such as eccentricity and attitude angle, but also the frequency of disturbance. The coefficients are continuous and tend to certain values even when the frequency approaches zero or positive infinity. In general, the direct terms of the dynamic stiffness increase with the increase of the frequency, while the cross-coupling terms tend to an equal value when the frequency becomes infinite, and all the damping coefficients decrease in the higher frequency region and vanish when the frequency approaches positive infinity.
817
Authors: She Miao Qi, Y.S. Ho, Hai Peng Geng, Lie Yu
Abstract: A general method is developed to deal with the compressibility of air film and to predict the linear dynamic stiffness and damping coefficients of air-lubricated bearings over the whole range of frequency. Numerical results reveal that both stiffness and damping coefficients are functions of not only the static parameters such as eccentricity and attitude angle, but also the frequency of disturbance. The coefficients are continuous and tend to certain values even when the frequency approaches zero or positive infinity. In general, the direct terms of the dynamic stiffness increase with the increase of the frequency, while the cross-coupling terms tend to an equal value when the frequency becomes infinite, and all the damping coefficients decrease in the higher frequency region and vanish when the frequency approaches positive infinity.
1230
Authors: Jae Min Kim, Jong Jae Lee, Sang Sup Ahn, Jun Seong Choi
Abstract: It is necessary to accurately estimate the dynamic characteristics of stay cables, especially damping ratios, to design cable damper for appropriate vibration mitigation of a cable-stayed bridge in service. In this study, a vibration exciter has been developed to evaluate the cable damping of a cable-stayed bridge. The feasibility of the developed system was verified through field tests on a 100m long stay cable. The damping ratios of the stay cable were estimated based on acceleration data as well as displacement data measured by digital image processing technique. The performance of the passively operated MR dampers with the different voltage inputs were investigated by comparing the estimated damping ratios.
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