Finite Element Calculation, Vibration And Fatigue Analysis Of7140-type Bus Frame

The frame is the foundation of the whole bus.It is the key base part of busassembly. The frame withstands the various loads from both inside and outside of thebus.The author studied the7140-type bus frame. Four working conditions were formedby simplified and abstraction method according the state of the stationary and movingconditions of bus. Analyzed and calculated the strength, stiffness, and the road randomvibration response and the random fatigue of the frame in various conditions. Provideda theoretical basis for the rationality of the frame structure, to reduce the structuralquality and cause of failure and reduce manufacturing costs, and improve thereliability of the frame.This thesis is based on finite element theory. The finite element model of the bus framewere established by using the finite element software ANSYS12.0. Established thefoundation for the frame follow-up analysis. Analyzed the force characteristics of thebus frame in four conditions, including the bus frame bending conditions,full loadbending twist conditions, emergency braking and emergency braking. Obtainedstress and displacement distribution data of the frame in various conditions used thestatistics of the result data,obtained the proportion distribution of stress range of theframe. Verified the static strength of the frame and the material utilization of theframe structure. carried out modal analysis of the frame, Came to the top twentyorders of vibration of vibration natural frequency and mode shapes.provided the basic data for avoiding resonance and the subsequent dynamic analysis.Used Modal superposition method to calculate the random vibration of the frameunder the road random excitation. Obtained the stress distribution and displacementamplitude of the random vibration of the bus frame. Got displacement, velocity,acceleration response curve at the maximum amplitude of the frame. Analyzeddynamic characteristics of the frame. By Using of random vibration calculation data,based on Three interval method of Gaussian and law of Miner, Carried out Randomfatigue strength calculation of the frame. Verified the fatigue strength of the frameUnder the action of the road random excitation.By analyzing calculation results, it showed that: strength and rigidity of the framein all operating conditions are excessive, and Material utilization efficiency is low.Be seen in the mode vibration shape diagram, The amplitude of the frame is mainly concentrated in the frame front and the end.As the requirements for arranging othercompatible components, Needed to consider ways to improve the frame structure, Tomake the frame displacement distribution reasonable under the dynamic vibrationconditions. under the action of road random vibration, The amplitude of the frame isalso mainly concentrated in the frame front and the end. Occurred resonantcoupling when Road vibration frequency meeting the second-order naturalfrequency,needed to change the structure parameters of the frame to avoid thiscondition. Through the random fatigue analysis, fond that fatigue strength of theframe structure is too excessive, The frame could be further optimized.By analyzing, this paper provides a theoretical basis for both further optimize ofthe fame and improving the design for the fame., and also provides analytical methodsfor the design and development of similar products.