Mathematical Modelling and Computational Simulation of the Hydraulic Damper during the Orifice-Working Stage for Railway Vehicles

Abstract

e objective of this paper is to establish an accurate nonlinear mathematical model of the hydraulic damper during the orificeworking stage. A new mathematical model including the submodels of the orifices, hydraulic fluids, pressure chambers, and reservoir chambers is established based on theories of the fluid mechanics, hydropneumatics, and mechanics. Subsequently, a force element based on the established model of the hydraulic damper which contains 56 inputs, 6 force states, and 47 outputs is developed with the FORTRAN language in the secondary development environment of the multibody dynamics software SIMPACK. Using the force element, the damping characteristics of the modified yaw damper with different diameters of the base orifice are calculated under different amplitudes and frequencies of the sine excitation, and then the simulation results are compared with the experimental results which are obtained under the same conditions. Results show that during the orificeworking stage, the new established mathematical model can accurately reproduce the nonlinear static and dynamic characteristics of hydraulic dampers such as the force-displacement characteristic, force-velocity characteristic, fluid shortage, hysteresis effect, and pressure limited effect. Furthermore, it also shows that the nonlinear characteristics of the orifice, air release, cavitation, leakage for high frequencies, and dynamic characteristics of fluid (i.e., the density, bulk modulus, and air/gas content) should be taken seriously during the modelling of the hydraulic damper at the orifice-working stage. e mathematical model proposed in this paper is more applicable to the railway vehicle system dynamics and individual system description of the hydraulic damper.

Development of an Impact Energy Absorption Structure by an Arc Shape Stroke Origami Type Hydraulic Damper

“…Terefore, the type of hydraulic oil had a relatively small efect on the impact damping performance of the origami hydraulic damper. (6) In the research for this paper, we researched a basic performance of the origami damper, mainly considering the above main efects, and we can ignore other infuencing factors due to their smaller impact such as the material of the origami structure, the temperature of the oil, etc. Due to its shape, can adapt to the multidirectional loads, the advantage about the origami damper is that it can be used without any universal joints or other related mechanical structures or in a compact space.…”

“…Cylinder-type hydraulic dampers are widely used as energyabsorbing parts for impact-and vibration-damping devices, and several research results on their damping performance against impact vibrations and the development of applied technology have been published [1][2][3][4][5][6].…”

Modeling Dynamic Pressure Loss by Absorption in Oleo-Pneumatic Shock Absorbers without Separator

“…Moreover, the equilibrium states of the oil-gas system before and after touchdown adhere to experimental gas solubility data. The present modeling approach assumes that the oil is incompressible, which is approximately the case for pressures up to 100 bar [22], while in drop test experiments, a maximum pressure of 45 bar was reached. Measurements of the pressure in the lower chamber by Willich et al [12] show an almost steplike force-pressure transmission during the landing impact, which indicates an almost incompressible oil.…”