| The crankshaft is a very important part of the engine,and is subjected to extremely highly mechanical loads during engine operation.In the actual work process,the crankshaft to withstand the cyclical changes in the gas pressure,inertia force of components with high quantity and corresponding torque,which easily leads to a rapid changes in the inner crankshaft including in the pull,pressure,bending,twisting stress.In order to complete the demanding design,crankshaft often is devised as complicated shape,whether in crank pin or in crank arm,and thus stress concentration is widely phenomena in the crankshaft design process.This problem existed in design not only gives arise to formation of fatigue crack,but also may lead to crankshaft breakdown and so make potential threats for the engine working.Especially,turbo supercharged engines will endure the more the above consequence than common ones due to their own explosive force.Therefore,it is more important to explore the strength and fatigue endurance of the crankshaft of turbo supercharged engines.In this research,we took a inline four-cylinder 1.5-T gasoline engine crankshaft system as the object of analysis,comprehensively analyzed the the dynamic stress of the crankshaft by theoretical analysis,computer simulation and experimental research methods,using the current advanced analytical techniques and tools,to predict the fatigue invalidation.It is designed to provide reference for the design and development of engine crankshaft.Firstly,we analyzed the operation state and force of crankshaft and its affiliated parts.In terms of multi-body system as crankshaft system,multibody dynamics theory and structural analysis theory were referenced to establish the multi-body dynamics equation;in term of fatigue invalidation,we detected the fatigue classification and factors influencing fatigue to identify which fatigue is involved,which theory is suitable to predict the fatigue and which method is used.Next,the CATIA software is used to model the crankshaft,body and other related parts.The indispensable body and the related components were meshed and established the finite element model using Hyper Mesh finite element preprocessing software.The model was established by ABAQUS software,which was prepared for the establishment of multi-body dynamics analysis.The crankshaft model was established by applying the multi-body dynamics software AVL-EXCITE POWER UNIT which automatically divided andreduced the crankshaft.After the completion of the above preparation,based on the dynamic software EXCITE POWER UNIT,a 15-T inline four-cylinder engine crankshaft multi-body dynamics analysis model was built.Based on the kinetic analysis,the dynamic load spectrum of the crankshaft in the working cycle of the engine was calculated.In view of the weakness of the crankshaft on the crankshaft of the engine,the crank angle fatigue strength analysis was carried out on the basis of the analysis of the crank strength:system calculation,analysis of force field data,the S-N curve of the material and the dynamic load spectrum of the crankshaft fillet.The fatigue life of the crankshaft was predicted by FEMFAT fatigue analysis software,and the safety factor at each fillet of the turbocharger crankshaft was analyzed.Finally,we calculated the crankshaft in the normal operation of the torque under different conditions,selected the maximum torque under different conditions for analysis and got the torque.And then we integrated currently domestic and interna tional experimental methods,specifically selected crankshaft bending fatigue test method,and did bending fatigue test to verify the accuracy of computer simulation and the rationality of prediction by the existing crankshaft fatigue bending test machine. |
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