Research On Fatigue Strength And Strengthening Process Improvement Of A New Engine Crankshaft

With the development of Auto industry,as the core component of automotive,engine has developed rapidly.High efficient,lightweight and high power of the engine has become the goal of the industry.To achieve these goals,technologies such as in-cylinder direct injection,high temperature EGR,turbo,integrated intercooling,high-pressure fuel rails,and stratified combustion are used gradually.Crankshaft as the core moving parts of the engine is subjected to harsh load.For its complex structure,there are many sudden changes in the axial section,which leads to failure when the crankshaft is subjected to alternating torsion,bending and tensile stresses.For the purpose of improving the reliability,guiding the design and improving the manufacturing process of crankshaft,it is proposed to analyze the crankshaft dynamics and fatigue strength of a new model.The dynamic finite element analysis of engine crankshaft under full working condition is carried out by using the data collected by a combustion analyzer on Engine dynamometer bench.With the modle reducing and force analysis,the dynamic model was built in AVL EXCITE PU and the analysis was carried out.The weak position of crankshaft is obtained,which provides a reliable data for the fatigue study.In this paper,the crankshaft dynamic analysis contains transient stress,modal analysis in all directions,displacement of engine flywheel and pulley end with the frequency domain distribution under the full working conditions.By calculating the characteristic value of the model,the natural frequency,vibration mode of the crank connecting rod system and The status of engine crankshaft in actual are obtained,which provides support for engine crankshaft design.The influence of rolling process on crankshaft fatigue strength was studied.The fatigue life of engine crankshaft is analyzed with finite element software with the rolling correction factor,fatigue damage theory and the data obtained in earlier stage.The safety coefficient of engine crankshaft under the full working condition is obtained,which further verifies the reliability of engine crankshaft.Finally,the fatigue test of crankshaft is carried out.The results show that the crankshaft strength meets its requirements.By adjusting the rolling parameters of crankshaft samples and conducting a series of fatigue tests,the optimum parameters are obtained.The test results are consistent with the theoretical analysis.It provides a theoretical basis for crankshaft design and processing technology selection.