Analysis of modal and uniaxial fatigue performance of the upper swing arm of a double wishbone suspension based on virtual road excitation
Double wishbone suspension,one of the important structural types in automotive chassis suspension systems and accurately positioned through multiple parameters,has higher stiffness and torsional strength.Due to its unequal length fork arms,it absorbs the lateral force brought by the tire,achieves good lateral support,and improves turning performances.When the wheels move up and down simultaneously,they can automatically change the camber angle,thereby reducing tire wear,better adapting to the road surface,achieving larger tire contact area and better adhesion.While excellent handling experience is guaranteed,comfort should also be thoroughly considered.Research on fatigue durability suggests that attempts to scan the road surface point cloud CRG model of the test field were made in the early years.Excitation signals for road condition simulation are generated and loaded into the finite element system for analysis.Thus,the corresponding component strength and fatigue design load are obtained.Currently,the research is focused on strength verification and durability analysis of the lower support arm in extreme working conditions such as emergency braking and actual load spectra to verify the accuracy of the results through simulation and dynamic stress testing.Virtual load and real load fatigue tests are conducted to optimize the design of stress concentration areas.A modal analysis reveals the double wishbone structure exhibits resonance at the excitation frequency.Therefore,finite element pre-analysis is employed to preliminarily determine the modal frequency range and vibration mode,and hammer impact modal tests are conducted to compare and confirm the accuracy of the finite element model,providing reference for further vibration reduction structure design and dynamic response solving.This paper mainly explores the fatigue performance of the upper support arm of a double wishbone suspension,and builds a finite element model of the upper support arm through mesh partitioning.Durable road conditions are simulated and enhanced,equivalent virtual roads are built,and load timing excitation signals are generated.A multi-body dynamics rigid flexible coupling system model is built and multi-body dynamics simulation analysis is conducted.Through a finite element analysis on the upper support arm,the 7-12 natural frequencies and vibration mode positions of the upper support arm are obtained.The modal frequency is markedly higher than the idle vibration frequency of the engine,helping avoid resonance.Meanwhile,the stress distribution on the upper support arm is relatively uniform,and the maximum stress area is at the ball joint where the upper support arm is connected to the steering joint.The fatigue durability characteristics of the upper support arm are obtained through the Miner fatigue damage accumulation rule.The maximum damage location is found in the area connected to the steering joint and the minimum cyclic fatigue cycle meets the actual engineering requirements.
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