Structural Performance Analysis And Optimization Of Three Bridge Rigid Frame Of Mining Dump Truck

The mining dump truck runs in full load or overload state for a long time,with poor conditions and complex road conditions.Therefore,the frame,which plays an important role in connection and load,has complex force and often cracks in use,which leads to the vehicle unable to drive normally or even accidents.In this thesis,the frame of a new mining dump truck is taken as the research object,and problems such as cracking failure and short life are studied.The main research contents include:(1)Failure analysis of weld cracking.The weld cracks and microstructure were analyzed by optical microscopy,OM,EBSD and other macro and micro microstructure characterization methods.Three fracture types and their crack sources(toe cracking,base metal heat-affected zone cracking,weld zone cracking)were determined.No abnormal structures were found in base metal,weld and fusion zone.The results show that the mechanical properties of the frame materials meet the relevant standards.Combined with the structural characteristics,statics and fatigue simulation results,it can be determined that the weld cracking is caused by insufficient design margin of weld strength.(2)Research on the static strength check and evaluation method of the frame.Aiming at the difficulty of strength evaluation caused by stress concentration and stress singularity in the welding zone of the frame,the finite element stress linearization method based on structural stress was introduced,which provided a theoretical basis and method for the strength analysis and design of the frame.Furthermore,the static strength of the frame was checked under six typical working conditions,the stress and deformation characteristics of the frame were obtained,and the weak position of the frame was indicated.(3)Analysis of multi-body dynamics characteristics of the frame.The first twelve order natural frequencies and vibration modes of the frame were obtained by free modal analysis,and the hidden trouble of resonance caused by the engine was eliminated.The virtual prototype of the vehicle dynamics was constructed,the 3D digital pavement model of seven typical working conditions was established,the dynamics simulation of the frame was carried out,and the vibration excitation characteristics of the frame were analyzed.The results showed that the D-level pavement excitation would not cause the resonance problem of the frame.(4)Fatigue life evaluation based on load spectrum.Based on the classical S-N method and Miner’s theory of linear fatigue cumulative damage,the fatigue characteristics of the frame were analyzed and the fatigue life of the frame was evaluated.The sensitive condition affecting the fatigue life was identified as the obstacle crossing condition,indicating that the fatigue life of the frame was loadsensitive.The dangerous position of the frame is predicted to be the weld of the suspension support and the longmen beam base.(5)Optimization design of frame structure.The single factor and multi-objective optimization design of the local structure of the frame and the multi-factor and multiobjective optimization design of the beam were carried out.The sensitive structural parameters affecting the strength of the frame were defined,the stress concentration and stress singularity were alleviated,the static strength of the frame was improved,and the fatigue life was increased.Considering the optimization results and production experience,the design of the new frame is carried out.The static strength and fatigue strength are further improved,and the stress singularity and stress concentration problems are alleviated.(6)Road test and comparative analysis.The road test of the newly designed frame was carried out and compared with the simulation results.The results show that the finite element and dynamic simulation results are consistent with the test results,and the simulation results are verified.This thesis has 96 figures,26 tables,95 references.