Research On The Fatigue Reliability Of Key Components Of Hydro-pneumatic Spring Damper For A Special Vehicle

Hydro-pneumatic spring is widely used in special vehicles because of its increasing nonlinear characteristics.However,the high-frequency impact load of the road makes the key components of its damping valve have all kinds of failures,leading to the failure of parts.Therefore,the research on the reliability of its damping structure is particularly important.This paper analyzed and discussed the characteristics of the hydro-pneumatic spring damper for the new generation of special vehicles.Based on this,the structural strength and fatigue life of the damper were evaluated,and the improvement scheme was proposed,which provided strong support for the improvement of the reliability of the new generation of special vehicles.Taking the damping valve of hydro-pneumatic spring of a special vehicle as the research object,the mathematical model and finite element model were established according to its specific structure and working principle The simulation of oil impact under different inlet flow rates was completed on workbench platform,and the pressure difference data on both sides was obtained.The simulation results were compared with the experimental results of the real vehicle sample under the same working conditions,and the accuracy of the simulation model was verified by the theoretical calculation results.Through the simulation results under the whole working conditions,the opening pressure difference of the damping valve was about 53.8MPa,and the corresponding piston movement speed was obtained 1.62m/s.Based on the fluid structure coupling simulation technology,6 kinds of simple harmonic vibration loading conditions were selected to analyze the flow field of the damping valve-oil model.The distribution of oil flow velocity and pressure under different working conditions were obtained,and the pressure field of the fluid structure coupling surface was analyzed,which provided data support for the stress and fatigue analysis of the key components of the damping valve.Modal analysis module was used to carry out modal analysis and extraction of the first fifteen modes of vibration of the damping valve,which eliminated the possibility of resonance under working conditions.Taking the valve core and valve seat as the research object,based on the results of fluid structure coupling simulation,the stress analysis and static strength check under normal and high-speed conditions were carried out,and the distribution of vulnerable areas was obtained.Based on the results of stress analysis,the fatigue analysis of the valve seat and the valve core under typical working conditions was carried out by using the stress life method,and compared with the failure photos of the structural parts of the real vehicle,it was found that the joint of the valve seat neck and the valve core rod were the fatigue failure positions.The influence of design parameters and operating parameters on the fatigue life of key components of the vibration damping valve was discussed by changing the aperture of the normal through hole,the stiffness of the back pressure spring,the piston loading speed and the oil viscosity.The orthogonal test design method was used to sensitively each factor.Based on the research results,the improvement suggestions were put forward.The specific plan was to adjust the stiffness of the back pressure spring to10 k N/m,increase the diameter of the normal through hole to 5mm,select the HM46 hydraulic oil,and increase the working cylinder diameter to 90 mm appropriately.The maximum stress of the vulnerable area of the rear valve core and valve seat was reduced by 51.8%,and the fatigue life was increased by 112.5%,which effectively improved the fatigue reliability of the damping valve.