Study On The Static Strength,Fatigue Properties And Connection Topology Optimization Of All-aluminum Bus

With the implementation of the green passenger car development strategy,the demand of new materials is increasingly prominent.As a kind of material with low density and excellent strength,aluminum alloy is gradually applied to lightweight passenger car body.Bus as one of the necessary means of transportation,it is essential for passenger car safety and economy to study on its strength and fatigue characteristics,and the research has huge impact on people's life and property security.The main research content is as follows:1.Topology optimization design of connection structure.The static and modal analysis methods are used to analyze the strength,stiffness and low order natural frequencies of the original connection structures under four conditions,and the latter are used as the sub objectives of topology optimization.Determining the shape of the outer contour of the connection structure with topography optimization,establishing a topology optimization model of connections based on SIMP density interpolation method,using the AHP to determine the target weight of sub goals,normalizing sub objectives,using compromise programming method,going on multi-objective topology optimization,and improving the design of the connecting piece according to the optimization results.2.Study on the stress distribution of aluminum alloy body structure.Calculation the bending stiffness and torsional stiffness of aluminum alloy body.The static characteristics of the body is researched under full load bending,left torsion,right torsion,emergency braking,left turn,right turn,left front wheel lifting/dangling 50 mm and right rear wheel lifting/dangling 50 mm eight conditions.3.Static loading test.According to GB/T 6792-2009 2<Bus Skeleton Stress and the Deformation Measurement Method>,measuring the stress values of each measuring point arranged on the car body under different working conditions,and the length variation of the front door,the middle door and the diagonal of the wind window,investigating the rationality of the frame structure design of aluminum alloy bus body,and verifying the correctness of the established finite element model.4.Aluminum alloy body structure fatigue life prediction.The mean modified Wang-Brown criterion is chosen to research fatigue durability of Aluminum alloy body structure.The data,including the results of unit load static analysis,load spectrum and frame material fatigue characteristic,is inputted to Designlife analysis process to calculate the structure fatigue life.Finally,the analysis results of static strength and fatigue characteristics of the body structure are compared.Results show that: The mass of modified connect structure is reduced by 18%.The natural frequencies of the first six orders are improved in different degrees,and the strength and stiffness properties are obviously increased.In the static strength analysis,the maximum stress value of the car body structure under the eight conditions did not exceed the allowable stress of the material,thus meeting the design requirements of the bus strength.By analyzing the static test data,the actual stress distribution and deformation of the car body are obtained,and the correctness of the established finite element model is verified.The fatigue life of the whole structure is predicted to be about 8.07 years,the mileage is 117.6 million kilometers,and the life span can meet the design requirements.