Fatigue Life Prediction And Improve Of City Bus Body Frame

In the process of driving,the vehicle is affected by the complex conditions such as variable speed,load and road excitation,and suffers the stress cycle caused by dynamic load,which inevitably leads to the fatigue failure of each structural part of the vehicle,among which the body,as an important bearing component of city bus,plays an important role in protecting passengers and drivers.Therefore,it is necessary to analyze the fatigue life of bus body frame.Taking the body frame of a city bus as the research object,the fatigue life is predicted and the fatigue performance is optimized and improved according to the weak points.First,according to the bus design parameters provided by the manufacturer,the three-dimensional model of bus body frame is built in Solid Works software,and the finite element model of frame is built by introducing Hyper Mesh.The dynamic performance of the finite element model is verified by modal analysis theory.The results show that the body frame structure can avoid resonance with internal power source and uneven pavement excitation,and has better dynamic performance.Secondly,according to the manufacturer for the design of the parameters set up in Adams/Car passmenger Car multi-body dynamic model of fully considering pavement lateral excitation and the influence of the fatigue life of all kinds of driving modes of bus frame.With B-level three-dimensional random road as the excitation,a simulation cycle is constructed based on the four-condition cycle of the city bus for virtual simulation,and the load spectrum at the connection between the bus body frame and the suspension is extracted.Then,the method based on inertial release in Hyper Mesh solving unit stress response of the body frame and the suspension joints,in combination with the S-N curve,the connection of the materials of load spectrum and the corresponding stress response in ANSYS n Code Design Life software to life prediction of frame.The results show that the body frame is safe distance is 120800 km,did not meet the requirements of relevant standards,so it is necessary to further optimize skeletal structure.Finally,the thickness of each square tube with a lower fatigue life is selected as the design variable,using the optimal Latin hypercube sampling design,the radial basis neural network is selected to establish an approximate model of the fatigue life and quality of the frame,based on the fatigue life of frame constraints,with the aim to optimize the frame quality,under the premise of guarantee the quality of frame lowest,the frame of car body fatigue life to meet the design requirements.Choose to use the ASA adaptive simulated annealing algorithm to solve the optimal solution in the Isight software,and substitute the rounded optimal solution into the finite element model to solve the problem.The results show that the fatigue life of the framework has been increased from 120,800 kilometers to 440,900 kilometers while the quality changes little,which meets the requirements of relevant standards,and the optimized frame still meet the requirements of dynamic performance,the optimization results provide reference for manufacturers to improve the fatigue life of the frame.