Fatigue Life Analysis And Active Control Of Key Parts Of Automotive Suspension

The automobile suspension system is an important part to ensure the smoothness and handling stability of the entire vehicle.It also has a crucial impact on driving safety.The fatigue life of its key components has always been the primary concern in structural design.The accelerating trend and demanding requirements presented by the weight reduction of the entire vehicle have made the contradiction between the fatigue life and weight reduction of the key component structure of the vehicle increasingly prominent.In view of the limitations and passiveness of traditional fatigue life control methods,the paper is proposed the active control method of introducing piezoelectric materials to improve the fatigue life of the key components of the suspension,which significantly improves the fatigue life of the controlled components,and at the same time the lightweight effect is significantly improved.In this paper,based on the actual distributed drive vehicle suspension system development project,the lower cross arm of the suspension is selected as the key component to complete the strength analysis and lightweight design,establish the rigidflexible coupling multi-body dynamic model of the suspension system and complete the fatigue life analysis.Then,the fatigue life influencing factors and sensitivity analysis of the component structure were carried out,the piezoelectric ceramic lower cross arm coupling model was established and the piezoelectric characteristics simulation and comparison were completed.The specific research contents are as follows:(1)This article first briefly introduces the structure of the double wishbone torsion bar spring independent suspension,establishes the finite element model of the lower crossarm of the suspension,analyzes the loading conditions of the bus and uses the vehicle dynamics model to extract the limit conditions The static load data of the lower suspension cross arm,complete the boundary conditions of strength evaluation and optimization design,and carry out the strength evaluation of the lower cross arm.The results show that the lower cross arm needs the structural optimization design.Meet the strength design requirements.(2)The basic theory of topology optimization and the variable density method are summarized for the purpose of lightweighting the lower cross arm of the suspension,and the element density of the finite element model of the lower cross arm of the suspension is used as the design variable for topology optimization,and the maximum stress cannot exceed 850MPa as a constraint Under the condition,the volume fraction of the lower cross arm structure is used as the objective function to perform the topology optimization design of the lower cross arm and complete the geometric reconstruction.Under the conservative optimization design scheme,the lower cross arm of the suspension finally achieves 13.1%light weight and meets its strength design requirements,reaching the light weight goal.(3)The rigid-flexible coupling model of the suspension system is established and the B-level pavement and C-level pavement are simulated separately to obtain the dynamic load spectrum of the lower cross arm under simulated working conditions.Based on the nominal stress method,combined with the stress and strain results under unit load,the dynamic load spectrum and the SN curve of the material,using the Miner cumulative damage law with the support of Ncode software to complete the suspension of the lower cross arm under the B-level road and C-level road Fatigue life prediction.Under class B pavement conditions,the minimum number of fatigue life cycles of the lower cross arm of the suspension is 8.353×1010 times,which is regarded as infinite life.Under severe road C level pavement conditions,the minimum number of cycles of the lower cross arm suspension is 5.293×106 times,equivalent to mileage of 1.058×105kilometers.(4)In this chapter,the influence factors of fatigue life of the lower cross arm of the double wishbone torsion bar spring suspension are sorted out and summarized,and four representative influence parameters are selected from them for single factor influence rule analysis.At the same time,orthogonal experiment design is carried out on the above four influencing parameters and sensitivity ranking is performed by analysis of variance,and finally the degree of sensitivity to the number of fatigue life cycles is obtained,which is the main influence factor of the lower cross arm of the suspension during the fatigue life design stage.The secondary evaluation provides practical application reference.(5)Based on the influencing factors of the fatigue life of the lower cross arm and limited by the passiveness of the traditional fatigue life control method,in this paper,the piezoelectric control of the fatigue life of the cross arm is used as a starting point to establish a piezoelectric ceramic lower cross arm coupling model,including piezoelectric Ceramic patch layout,selection of piezoelectric materials,research on piezoelectric characteristics,and finally complete the simulation of piezoelectric characteristics and comparative analysis,to provide direction and reference for the research and practical application of piezoelectric control of fatigue life.