Multiaxial Fatigue Analysis Of Hub Assembly For Heavy Commercial Vehicles

Wheel is an important part of a ground vehicle,any dynamic behavior of the vehicle is finally realized by the friction between the wheels and the ground,and hub is the basis of wheel.As the only part connect the vehicle and the road,hub is subjected to extremely complex loads at work and is often under multiaxial stress state,so its reliability is very important to the safety of the vehicle and it is very meaningful to study hub's fatigue life by multiaxial fatigue theory.This paper takes the wheel hub of a commercial vehicle as the research object,and its damage characteristics and life prediction method under multiaxial load is studied.The paper's main contents include the following aspects:Simulation of thin wall cylinder specimen and wheel hub is conducted to study the stress distribution characteristics and influence factors of the structure under multi-parameter load.Results show that the structure's stress distribution would change when the load changes,the load's amplitude ratio and phase difference affect the stress distribution,and the structure is under multi-point damage state.Multiaxial fatigue theory is applied to the structure's fatigue life prediction under this condition.Based on the theory of critical plane method,the finite element simulation on thin wall cylinder specimen is conducted.And the prediction ability of several common multiaxial fatigue life models is evaluated by comparing the test results with simulation results.Results show that the position of the critical plane and the damage parameter are related to the equivalent stress amplitude and the load phase angle;the KBM model defined the plane with maximum shear strain amplitude as the critical plane,and takes the normal strain on the plane into consideration,its life prediction effect is better when the structure is under multiaxial stress state.The finite element model of hub assembly is established,the boundary conditions of the model are defined,model's grid size and the selection method of discrete load step is discussed,a multiaxial stress state estimation method is proposed to judge the stress state of the key parts of hub.Finally,the critical plane's position and the prediction life of hub are obtained.Results show that it is necessary to fully consider stress' peak value on key parts of the structure when selecting discrete load step;proposed multiaxial stress state estimation method can distinguish the uniaxial stress state,proportional and nonproportional multiaxial stress state;area near the hub bolt hole and the vent hole are two key parts and both are under nonproportional multiaxial stress state,area near bolt hole is more likely to occur fatigue failure.A life prediction method of the structure under multiaxial random load is defined,simulation is carried out to simulate the experimental process and two results are compared to verify the effectiveness of this method.Based on this method,the fatigue life of key parts of hub under random load is predicted.Results show that this multiaxial random fatigue life prediction method and multiaxial fatigue model is good at predicting the high cycle life and is suitable for hub's fatigue reliability analysis.