Research On Damped System Of Railway Vehicle Hydraulic Damper And Failure Of Its Key Parts

China has made great achievements in railway technology, from speed increasing on April 1st,1997 at first time to on April 18th,2007 at the sixth time. Especially since we started to import advanced railway transportation equipment (such as locomotives and high speed trains, etc.) in 2004, China’s overall railway technology has rapidly come up to the high level in the world, but some technologies of key parts are not grasped yet. The oleo absorbers used in railway construction have almost been foreign products since 1998, because the home-made oleo absorbers go wrong functionally (ineligible damping performance) and with structural failures (bead crack, loose thread connection, loose rubber joint or stripping between rubber and metal), which affects the train safety severely, stability and riding comfort. In recent years, the above failure types also appeared in foreign oleo absorbers which were used in Hexie locomotives and high speed trains in China. Developing the oleo absorbers meeting the need of modern high-end railway transportation equipment as soon as possible will not only stop the relying on importing, shorten the production cycle, lower the cost and improve the competitiveness to make more profit, but also fill in null in independent intelligent property rights of oleo absorbers and leave a profound significance for owning full core technology of major equipment’s key parts.This dissertation, the functional and structural failures of railway oleo absorbers is taken as research objects, based on the tracking of advanced international researches, via a lot of experiments, theoretical research and computer simulation, the mechanism of functional and structural failures in oleo absorbers is investigated, and finally solutions are proposed. It will help the railway oleo absorbers to arrive at the advanced level in the world both in theory and manufacturing, shorten the R&D cycle and strengthen the company’s competitiveness through the research.The main content of the subject is as follows:(1) Based on analysis the geometrical structure of the vertical oleo absorbers of the Hexie locomotives, a lot of experiment data were got, the dynamic mathematical model of the damping regulating system was established, and the opening factors, sequence and criterion of all the damping regulating valves were determined, then the solution of the major parameters comes out finally. Through the simulation with MATLAB/Simulink, the dynamic parameters, indicator diagram and damping performance curve of the absorber were got. Through regulating the major structural parameters of the parts that affect the damping performance, the absorber can better satisfy the need of the damping performance in the product standards.(2) The 3D geometrical model of the railway absorber was built with Solidworks and the dynamic mesh was got with ANSYS ICEM CFD and STAR-CD, then the mesh model was transferred into CFX, boundary conditions were set and the flow field was solved with different moving speed, thus the distribution of the inner flow field of the absorber was achieved. Via varying single parameters, the effect of all the parameters on the structural strength was evaluated. Through the analysis of the inner flow field of the absorber, the mechanism of the functional trouble is concluded as:with the velocity of vibration increasing, the damping force boosts as well. As a result, the growing liquid energy loss in the damper valve leads to the temperature of the oil going up rapidly, the oleo eddy flow swirling, cavitation aggravating caused by the negative pressure of the outlet increasing, etc. A strong eddy flow, providing the screw cap with running torque, results in the looseness of the screw cap and the deficiency or failure of the damper performance. The heated oil, cavitation and eddy flow in the outlet of the damper valve fill the oil storage cylinder with much bubble, which will enter the oil cylinder through the one-way valve in the bottom, the indicator diagram will go wrong and the damper will fail. Through the improvement of the structure, such functional issues as the looseness of the regulating screw cap and the malformed indicator diagram under high speed are solved. With the CFX post-processing, the damper force of the absorber under different conditions was extracted, the indicator diagram was drawn and a new method for the simulation of the absorber damper was provided.(3) The strength of the oil cylinder and the fatigue life index of the regulating spring were checked with classic mechanics; the key parts affecting the structural strength of the absorber was analyzed with finite element method, the mechanism of the structural failure was achieved, and the optimized value of the key structural parameter is determined, then structural failure is removed.(4) The boundary conditions at the product design stage are equivalent to the practical ones, checked with in situ measurement, experimental data were collected for the improvement of the suspension system and the continuing innovation of absorbers (for example, the development of semi-active control oleo absorber); Through the bench test of the absorbers, it is proved that the result of this dissertation has a guiding meaning for the improvement of the practical structural parameters; the applicability and reliability is checked, via the endurance test and the evaluation with vehicle loading.