| As an important component of internal combustion engine, crank connecting rod system is working under ignition impact force for transforming the piston translational motion to the crankshaft rotation and transforming the combustion of internal conversion to kinetic energy. Subjected to periodic outbreaks of thrust and components of resistance moment alternating load, connecting rod system is vulnerable to the most common mode of failure and that is fatigue damage, so the fatigue damage analysis and simulation is of great significance to design optimization.The working principle and transmission mode of crank-connecting rod are introduced in this paper, simplified static analysis of boundary conditions is proposed according to the kinematics equations and dynamics equations, and according to the simplified boundary conditions this paper carried on finite element static simulation analysis so as to realize the strength calculation of the connecting rod and the results are compared with the traditional calculation method. The comparison of two finite element simulation methods of bolt pre tightening force of temperature method and pre tightening unit method is simulated by means of computer simulation so as to obtain the analysis of the similarities and differences between the two methods. In addition, this paper also introduces the theory of dynamics of multi rigid body and rigid flexible coupling and multiaxial fatigue theory.With the method of computer aided function and virtual prototype test, this paper finished with finite element theory of crank of a new L4 engine based on fatigue analysis.3D model and assembly model of crank-connecting rod was founded by Pro/E. What is more, dynamic virtual prototype test of pure rigid body and rigid flexible coupling in ADAMS with the application of data interface is performed in this paper to obtain the kinematics characteristic curve and theoretical feature function and compared to verify the rationality afterwards. In addition, this paper also gets the stress of connecting rod under the rated conditions, curve deformation, extraction value, deformation value of stress at specific time, and the link flexible features. At the same time, static analysis and dynamic analysis results are compared and verified the limitations of some approximate research methods.The stress and deformation time history data is loaded into FE-SAFE software and obtain the fatigue life analysis based on the multiaxial fatigue theory and mean stress correction algorithm, and the load coefficient of connecting rod fatigue life and the connecting rod design life coefficient images is also realized in this paper. The FOS values that can be taken as the target of optimization design value design life rate are extracted, and the impact of surface machining processes on the fatigue life of connecting rod is explored.Through calculation analysis results, it is shown that the motion law of crank connecting rod fits well with theory analysis, the strength of connecting rod and stiffness can satisfy the requirements, and the fatigue life of the connecting rod under the rated condition meets the design requirements. Surface processing has obvious effect on fatigue life which will provides advice for the optimize design of connecting rod. Life design implementation rate of FOS value and its variance can be target values of connecting rod optimization algorithm. |
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