Research On The Relationship Between The Fatigue Performance Of Steering Knuckle And The Main Parameters Of Damping System

Steering knuckle is one of the important parts of automobile suspension system.It bears the impact of wheel load and road surface,as well as the random load of steering and braking.Once it fails,it will cause the vehicle unable to drive or even lead to major safety accidents,so it has higher requirements for its fatigue durability.The fatigue failure of steering knuckle is mostly caused by long-term random load,while spring and shock absorber play an important role in the suspension system motion and the damping of load amplitude.At present,most of the researches on the fatigue durability of the knuckle are focused on the fatigue life of the knuckle in a certain suspension system,and there is no research on the relationship between the fatigue performance of the knuckle and the main parameters such as damper,spring stiffness,etc.Therefore,this paper takes a compact SUV as the research object,aiming to find out the influence of the main parameters of the damping system on the fatigue performance of the steering knuckle.Firstly,the whole vehicle parameters of the test vehicle are measured,including the coordinates of the hard points,the inertia of the components,the mechanical curve of the elastic elements.The multi-body dynamic model of the whole vehicle is established and verified by K&C;Carry out the strengthening road and test rig of the whole vehicle test field,collect the six component forces of wheel center and the monitoring signals of multiple parts of suspension under different working conditions.such as wheel center acceleration,spring displacement and subframe acceleration,and preprocess the test data.In order to find a suitable load spectrum extraction method for the analysis of the fatigue performance of the knuckle,In the time domain and root mean square values,the simulation and measurement curves of monitoring points of vehicle body and suspension are analyzed.The results show that the constraint loading method is more suitable for high frequency and low amplitude vibration conditions,and the virtual iteration method is more suitable for a wide range and more accurate simulation,but more time-consuming than the constraint loading method.Considering synthetically,the load spectrum extraction methodused in this paper is virtual iteration method.The simulation modal analysis of the steering knuckle is carried out,and the accuracy of the analysis is verified by the test;The process of calculating the fatigue life of the steering knuckle based on the modal stress recovery method is described in detail,and the accuracy of the method is verified by experiments,which verifies the reliability of the modal stress recovery method in calculating the dynamic stress of the steering knuckle under complex load-bearing conditions.Through theoretical model and multi-body simulation,the influence of damper damping and spring stiffness on the boundary load of steering knuckle is discussed.The results show that damper damping has a significant influence on the boundary load of steering knuckle,while spring stiffness has a slight influence.Based on the virtual iteration method and the modal stress recovery method,the fatigue life of the steering knuckle is calculated under different damping coefficient and spring stiffness.Through comparative study,it is found that the damping coefficient has a significant effect on the fatigue performance of the steering knuckle.the fatigue life of the steering knuckle increases first and then decreases with the increase of the damping coefficient of the shock absorber,that is to say,the fatigue life of the steering knuckle is affected The damage area of the main area decreases first and then increases,and the damage area of the secondary area which affects the fatigue life of the steering knuckle always increases with the increase of the damper damping coefficient;The influence of spring stiffness on the fatigue performance of steering knuckle is weak.In the traditional design range of suspension spring stiffness,the fatigue life of steering knuckle tends to decrease with the increase of spring stiffness.The change of damage area in the main area that affects the fatigue life is not obvious,but the damage area in the secondary area that affects the fatigue life of steering knuckle always increases with the increase of spring stiffness.At the end of the paper,genetic algorithm is used to optimize the damping coefficient of the shock absorber.