Fatigue Life Prediction Method Reseach For Camshaft Based On Load Spectrum Of Full Conditions

Camshaft is one of the key components of the diesel engine. During the operation of thediesel engine， Considering the high periodicity of the contact stress and the fast relativesliding velocity between the cam surface and the tappet， the cam shaft withstand largerbending and torsional loads.the shaft neck of camshaft very prone to stress concentration，when it bearing excessive force turn up the fatigue damage phenomenon.This paper takes acamshaft as the research object， based on the principle of multi-quality dynamics， usedvalve-train AVL software to established one-dimensional simulation analysis model. And byOne-dimensional simulation of valve train dynamics analysis obtained the camshaft sufferedload in the assessment conditions. Establishing three-dimensional solid model of thecamshaft，and using the transient dynamics simulation analysis to obtain the distribution ofvarious conditions stress of the camshaft. Compared various load spectrum method to find thesuitable load spectrum method for the camshaft，and establish stress distribution loadspectrum during four working conditions about camshaft. According to the Load distributionand load history of camshaft， select the appropriate method of fatigue analysis to calculatethe fatigue life， and analysis the methods to improve the fatigue life.Apply the AVL TYCON software to establish the Department of intake valve， exhaustvalve system，valve train components，bearings,drive mechanism and using these departmentto establish one-dimensional simulation model of Valve Train. By the four Valve assessmentconditions: the rated speed condition，90%of the rated speed conditions，80%of the ratedoperating conditions， maximum torque conditions received suffered load at the point ofcontact of the cam and follower， and the torque of whole cam shaft in the work process.Simulation results show that the buffer segment will appears larger distribution in the workprocess of the camshaft.Using Pro/E software to establish the three-dimensional solid model of camshaft and camshaft bearings simplify bearing，and import the three-dimensional solid model into thespecialized processing software ANSA. Minimize transient finite element analysis，a largeamount of the guarantee accuracy premise model solving scale only in the structure weakjournal excessive fillet using a fine grid. Using finite element analysis software ANSYSanalysis the camshaft in the four conditions，The finite element analysis results show that thecamshaft stress concentration areas are mainly located in the cam shaft neck and the transitionof rounded corners. The distribution of stress provide the signal data for the preparation of theload spectrum.On the basis of existing fatigue analysis methods，taking into account the camshaft stresslevel conditions in the elastic range for all the working conditions，select the nominal stressmethod (S-N curve Act) as a camshaft fatigue life prediction method；Comparesingle-parameter to two-parameter cycle counting method，taking into account thetwo-parameter cycle counting method can be more true representation of variableamplitude loading process，the preparation of the four points of the two-parametercycle counting method rain flow counting method camshaft load spectrum；Load finiteelement transient the results of the analysis into the fatigue analysis software NCode DesignLife. Established S-N curve and analysis model of fatigue analysis model according to theempirical formula and material fatigue properties.By the Miner linear cumulative law analysisvarious operating conditions fatigue life of the camshaft stress concentration，the combinationof conditions the camshaft overall fatigue life，provide theoretical support for camshaft fatigueanalysis...