| The technology of the automobile industry is becoming increasingly mature.In order to adapt to the competition in the present society,it is necessary to improve the overall performance of the automobile,especially in the aspect of the fatigue endurance of the whole vehicle,which is related to the driving safety.Although China's automobile industry continues to develop towards specialization,there is still a lot of room for improvement after a slow start.In order to achieve automotive specialization,efforts should be made to improve the performance of the whole vehicle.This study takes the passenger car provided by an enterprise as the research object to analyze and study the fatigue durability of the car body.By using the inertial release method,the finite element simulation of the body is carried out to obtain the stress field distribution of the body under the action of unit load.Combined with multi-body dynamics,a rigid-flexible coupling vehicle model is established.The load spectrum of the hub of the test vehicle in the actual test field was obtained,and the load spectrum of the connection point between the body and the chassis was extracted by virtual iteration.Combined with the related theory of fatigue analysis,using the theory of local strain in the Ncode method combined with material characteristics,load spectrum,the fatigue life analysis,according to the results of the simulation of the fatigue of targeted puts forward improvement scheme,as the basis of the design of white body,realize the Hypermesh,MSC.Nastran,Adams/car,Femfat,Ncode software,the combination between mainly includes the following contents:1)Building the body model in the 3d software Ug,and use the finite element software Hypermesh to build the body finite element model.The body finite element model is composed of the roof assembly,floor assembly,front firewall assembly and side fence assembly.In the process,according to the practical design of car body choice solder joints and weld position,and the body both inside and outside decorations in the form of concentrated mass rigid unit instead of,in the body and chassis join point load on the X,Y,Z three directions of unit load,through the simulation analysis stress field distribution of the body under the action of a unit load,as one of the essential conditions of automobile body fatigue analysis of the late.2)Corresponding to the model test of a target vehicle road test in Belgium,the sensor measurement system and install the six component between the wheel and rim,the acceleration sensor at round heart,suspension spring point displacement sensor installation,and in the middle of the front and rear stabilizer bar,left,right and swing arm,left and right steering rod displacement sensor installation,won six component and chakras centripetal acceleration,suspension spring displacement,load late for virtual iteration decomposed body and chassis connection point of hard point load.3)According to the body chassis parameters provided by relevant enterprises,in Adams/car,adjust the parameters of each subsystem to make it close to the test vehicle,and assemble each subsystem into a multi-body dynamics model of the whole vehicle.In order to make the simulation results accurate,the body is discretized into a flexible body and a rigid-flexible coupling model is established.On this basis,the vertical displacement of the wheel center is obtained by virtual iteration in Femfat_Lab software using the acceleration signal of the wheel center,and the dynamic load at the connection point of the car body is decomposed as the input load.4)Body fatigue life is directly related to the accuracy of the load spectrum of accuracy,to determine the accuracy of the load spectrum obtained numerical simulation of the experiment,combining with the standard test,extract the front stabilizer bar can be measured through experiment easily measured load and simulation load as compared to determine the accuracy of the load spectrum,the method of sampling to determine body join point load accuracy.5)Combined with body material E-N,body unit load characteristic curve of the static analysis results and chasis join point load spectrum,using the theory of software Ncode combined with local strain(E-N)body,the fatigue life of cloud simulation according to the simulation results,the rear cover parts relatively weak structure optimization to improve,to contrast simulation,body fatigue life of the local minimum value increased from 75000 km to 122000 km,the superiority of the improved scheme is verified.The research method of this paper is combined with road test and simulation technology,which is not only suitable for fatigue analysis of vehicle body,but also for fatigue life analysis of vehicle parts,shortening the cycle of automobile research and development,reducing the number of vehicle test and testing cost,and improving The competitiveness of automobile enterprises has certain engineering guiding significance. |
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