Fatigue Life Prediction And Improve Of Light Truck Cab

In the process of driving,the vehicle bears numerous impacts from the ground.Most of the damage of parts and components is failure in the form of fatigue damage.As an important part of commercial vehicles,the cab ensures the safety of the driver’s life.If fatigue damage occurs,it will endanger life.Therefore,it is very important to analyze the fatigue life of the cab.In this paper,the cab of a light commercial vehicle is selected as the research object,and the virtual reliability test is used to analyze its fatigue life,and the cab design is optimized.First,the finite element model of the light truck cab was established to analyze the dynamic performance of the cab.According to the threedimensional model of the cab provided by the enterprise,establish a finite element model of the body-in-white of the cab in the Hypermesh software;perform a free modal analysis on the cab and analyze its vibration characteristics,whether it resonates with the external excitation,and the occurrence of resonance will cause.Abrupt or sudden increase in stress on the cab structure will greatly reduce the fatigue life of the cab structure.The results show that the vibration characteristics of the cab body-in-white structure meet the design requirements.Secondly,a rigid-flexible coupling model of the vehicle is established,and the vehicle dynamics simulation is performed to predict the fatigue life of the cab structure.Based on the modal neutral file of the cab and the frame generated by Hypermesh,a rigid-flexible coupling model of the entire vehicle is established in Adams/car,and the three-dimensional random road surface is used as an incentive to perform vehicle dynamics simulation to obtain the cab and suspension connection dynamic load data.Finally,the static response of the cab structure was calculated using the static superposition method,and the fatigue life of the cab structure was predicted using the nominal stress method.The results show that the fatigue life of the cab structure is 40,000 km,which does not meet the design requirements of the company’s 156,000 km,so the cab structure needs to be optimized.Finally,in order to improve the fatigue life of the cab,the approximate model theory is used to optimize the structure of the cab to meet the fatigue performance requirements while ensuring the minimum cab quality.An approximate model of the fatigue life,mass of the cab structure and the thickness of the panel structure is established using a radial basis neural network to constrain the fatigue life of the cab,with the cab mass as the goal.By changing the thickness of the panel structure,ASA adaptive simulated annealing is used algorithm,find the optimal solution,bring the optimal solution into the finite element model and compare with before optimization.The results show that: without increasing the quality of the cab,the fatigue life of the cab increased from 40,000 km to 169,000 km without resonance with external excitations.After the optimization,the cab meets the design requirements.The optimization results provide reference for relevant departments of the enterprise.