Theories And Simulations On The Vibration Absorbing Systems Of Vehicles

Vehicle comfort and collision safety performance is closely related with the shock absorber. At present, the development and the design of shock absorber stay in imitation of design, experience design and experimental correction. The lack of advanced design theory of shock absorber leads to problems of failure, high cost and long development cycle. In hence, study on the working principles, failure mechanism theories, perfect design concepts, optimizations of damper structure by experiment and simulation have important theoretical significance and engineering value.Based on the theoretic research, this paper established the conversion formula of damping force and oil hydraulic pressure, throttling formulas, valve deformation formulas under three different equilibrium models of forces. Further, through the Java iterative calculation, we obtained the change history of valve radial line when the separation point between valve disc and spring basement was out of the ring groove(d≤a). We found that it was a parallel flow during the period the valve wasn’t open and it was a radial flow between two parallel flat planes during the period the valve was open. In the analysis of the two throtting calculation, the local head loss and the frictional head loss were considered. The rod padding effect to the inner radius and the throttle orifice flow effect to the throtting thickness were considered in the second throttling calculation. Oil pressure obtained by the throttle formula and obtained by the conversion formula had a good consistency. The contact types between valve disc and spring seat were circumference line contact, circumference surface contact (the untouched section is entirely subjected to the hydraulic pressure) and circumference surface contact (the untouched section is partially subjected to the hydraulic pressure). Under the assumed distribution load, valve disc deformation calculation based on the theory of shells and the finite element showed a good agreement.Based on the theoretic research, we pointed out the causation of the indicator diagram (F-S diagram) deviation, the causation of the curve penetrating, the factors which influenced the indicator diagram plumpness. The valve system sensitivity deficiency would lead to the variation of damping force behinds the piston speed change, and to form a "residual force"(the incentive speed was zero but damping force wasn’t zero), and the indicator diagram deviation. On the damping force vs. velocity diagram (F-V diagram), the first half of the recovery curve or the compression curve would separate from the second half. When the separation of a high speed curve was too large, this curve would pass through a low speed curve on the indictor diagram. Effects of the velocity point (Vmax) and the open gate velocity to the indicator diagram plumpness were neglectable; when the open gate damping force and the slope of the second segment of the F-Vmax curve (k2) were determined, the indicator diagram plumpness was certain; when Fo was certain and k2reduced, work would decline; the damping force hysteresis would induce serious un-plumpness of the indicator diagram.Through tests and anatomizations, we pointed out that abnormal fluctuations of damping force were corresponding to the processing quality and the design analysis, there was a correspondence between the abnormal noise and valve opening state (Fo/Vo)-The main quality problems were the oil leak, the gas pressure resistance loss, the aberrancy of damping force and the pine twisting moment loss. Friction direction swerve, lack of valve sensitivity, loss of pine twisting moment, irrational design and valve disc wrap had different features in the anatomization results and the F-S curves and the F-V curves. The acceleration time characteristics and the acceleration frequency characteristics of withdraws with noisy problem were generally bigger than the normal ones’, so were the damping force time characteristics and the damping force frequency characteristics of withdraws with noisy problem; those abnormities were caused by opening the valve, and their open status were generally bigger than the normal ones.Two simulation methods for forecasting the damping force characteristics, a dynamic fluid-structure interaction (FSI) finite element system and a dynamic fluid-structure interaction finite element impact system were promoted. The predicting methods of F-Vmax curve were:①aining the damping force at each velocity point by using quasi-statics method;②Gaining the F-V curve of Vmax=1500mm/s. Through a series of simulations, we gained the damping force vs. velocity characteristics, the distribution and the history of the valve disc stress and the fluid field. Meanwhile, simulation results had verified the rationality of the theoretic method. Also, we probed into ways, such as sub cycling, to promote the computation speed and the computation precision.Also, this paper had accomplished an airdrop landing simulation of a vehicle for special services. We pointed out that the axle was the weakest part; the contact time and the ground stiffness were closely related. When the ground was a concrete material, the contact time was the shortest, vehicle dynamic stress and its fluctuation was the biggest. For further understanding the effects of the shock absorber to the vehicle safety and its damage, this part has a good help.