Reliability Analysis And Test Of Double-tube Hydraulic Damper

The hydraulic damper is a necessary part in the vehicle. It can improve the comfort of thevehicle by absorbing vibration from the pavement. It can also avoid the serious roll and pitch,therefore improve both the ride and handling performance of the vehicle. The failure of thehydraulic damper will make the vehicle shake, the wheel sideslip and cause a longer brakingdistance, thus it can directly influence the safety of the passengers. In addition, the hydraulicdamper always works in an adverse working condition, how to improve the reliability of thedamper has become an urgent research topic. Therefore, this paper will base on the double-tubehydraulic damper, try to study on the reliability assessment, research the forming principle to thehydraulic damping, and build a model to describe the degradation characteristics of the damper.Then, obtain reliability and lifetime of this double-tube hydraulic damper by analyzing thedegradation data, which provide identifiable ground for improving the reliability of the hydraulicdamper. During the whole work, the main research includes:Firstly, stated the background and significance of the study; gave an overview of thedevelopment history and research status of reliability engineering; Summarized the problem ofreliability analysis and test method; introduced the development of the reliability analysis aboutthe damper at home and abroad and pointed out the deficiency; On this basis, proposed thecontent and ideas of this study.Secondly, the constitution, working principle and working requirements of the hydraulicdamper was researched. The definition of the failure mode by collecting the failure field data wasintroduced. Through fault tree analysis (FTA) and failure mode, effects and criticality analysis(FMECA), made sure the influence of every failure mode. Finally it can get the parameter whichcan represent the failure of the damper, and made a further analysis of the key component in thedamper.Thirdly, on the base of the working principle of the damping force, build the rebound(compressive) force model in the rebound (compression) stroke when the rebound (compress)valve was open or close. Simulated the hydraulic damper’s damping characteristic by usingMATLAB: get the charts of the piston displacement VS damping force (indicator diagram) andthe piston velocity VS damping force (Velocity characteristics). A physical prototype test wascreated, which showed the accuracy and efficiency of the theoretical model.Fourthly, the relationship between the damping force and different failure mode was anayzed.The sensitivity analysis of the different parameters was done and the prior distribution of the damping force according to the structure sizes and the distribution of varied parameters wascalculated by using Monte Carlo Method. Researched on the degradation mechanism of thedamping force and a degradation model for the damper were derived by considering thedegradation of the oil viscosity.Fifthly, established a degradation test plan based on the equipment of test-bed and gotdegradation path based on the degradation data of the rebound (compressive) force by using theLeast Square Method. Further studied the distribution of false lifetime, and by introducing thetheory of virtually expanded sample estimation method, Bootstrap method, also use the priorinformation, estimated the extremely small scale sample test data. The test data is processed bythe method of graphical estimation, and finally worked out the parameters of the reliabilitystatistical model. The reliability of the damper under certain conditions was achieved.Finally, a conclusion was made and the future research about the reliability of double-tubehydraulic damper was briefly presented.