| The lightweight of automobile has become a trend of car. But as a traffic tool, the safetyand reliability of the car must be ensured. According to the statistics,80%of the mechanicalstructure failure was caused by the fatigue cumulative damage. Traditional car fatiguestrength assessment is conducted through the field test or indoor experiment, but this methedis not only time-consuming but also costing. In recent years, with the improvement of thenumerical calculation method and the simulation tools, virtual simulation analysis of the carfatigue durability has become possible.Welding structure is applied in automotive field extensively, and it is the mainconnection form between the vehicle cab metal sheets. However, due to the weldingcharacteristics, the welding place of the structure is more likely to fatigue failure. Therefore,it is the key to analyze the spotweld fatigue life for the commercial vehicle cab fatigue lifeanalysis.Aiming at the current domestic situation that most fatigue life analysis of commercialvehicle cab is limited to structure analysis, this dissertation calculated the fatigue life of thecommercial vehicle cab structure and apot weld under real vehicle load spectrum through thefinite element method.The fatigue life results were evaluated according to the truck thirtythousand kilometers durability standard.At last, the influence of the sheet material and thespotweld diameter to the vehicle cab fatigue life was analyzed.Firstly, the commercial vehicle cab finite element analysis model was established, andthe spotweld model was the key point. The cab three-dimensioned finite element model andspotweld model were verified through the contrast between the experiment modal analysisresults and the simulation modal analysis results.After that，the general process of the virtual commercial vehicle cab fatigue lifeprediction method based on testing load data was introduced. Input load time process wasacquired through the real truck experiment at China DingYuan Testing Ground, and the correctness of the fatigue life results was further guaranteed by the accuracy of the load data.Because there is vehicle cab rigid body displacement during driving, the unit force stressresponse was calculated by inertia relief method through the MSC.Nastran. The stessresponse, combined with cab input load spectrum, cab structure and spotweld S-N curves,was imported into the MSC.Fatigue. Then, the fatigue damage and life of the vehicle cabstructure and spotweld was obtained. The fatigue life results showed: the fatigue strength ofmost locations of the cab structure and spotwelds was high; local positions such as the cabfront window corners and the cab mounts were a little lower. The life of the commercialvehicle structure are qualified, however, part of the spot welds are failed. The proportion ofthe failed spot welds is1.03%. At last, the influence of the metal material and the spotwelddiameter to the vehicle cab fatigue life was analyzed.Through the virtual simulation method to analyze the fatigue life of car structure, it hasgreat significance and reference value for the early car design and development. It can alsoshorten the development cycle of the products, reduce development costs and improve themarket competitiveness of products. |
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