Performance Comparison And Notch Parameter Selection On Con-rod Fracture Splitting Machining Of 36MnVS4 And C70S6

Connecting rod splitting technology cannot only significantly reduce the process of connecting rod processing and manufacturing costs,but also improve the manufacturing accuracy and carrying capacity of the connecting rod.Splitting technology requires the connecting rod not only have higher rigidity,strength and fatigue resistance,but also cannot has large plastic deformation in the fracture splitting process.Therefore,the material should also meet the above requirements,and ensure that the body and cap of the con-rod have a better meshing performance.In this paper,the con-rod materials that include high-carbon microalloyed non-quenching-tempering steel C70S6 which is widely used in recent years and medium-carbon microalloyed non-quenching-tempering steel36MnVS4 which is a new material are selected as the research object.On the basis of fracture mechanics and stress concentration theory,the two typical materials are compared to analyze the numerical simulation of the con-rod splitting with the help of large commercial software ANSYS/LS-DYNA.Meanwhile,the fracture properties and defects of 36MnVS4 are investigated.The prefabricated cracking groove is a key process of the con-rod splitting technology.The rational design and the machining quality improvement of prefabricated cracking groove are extremely important to the quality of connecting rod splitting.The influence of groove geometric parameters is analyzed and the optimum parameters are determined in this paper.It provides the basis for application of the con-rod splitting technology and the promotion of new materials.Based on fracture mode and basic theory of fracture mechanics,the causes of crack initiation in cracking groove are analyzed and the analytical expression of the stress and strain near the cracking groove is given.Combined with the micro-structure of connecting rod fracture and the small scale yield line elastic fracture theory,the maximum principal stress criterion is established as a unified criterion for crack initiation and propagation in numerical simulation analysis.Moreover,in order to obtain the stress strain curves and mechanical parameters of the materials,the tensile tests for two kinds of materials are conducted.According to the material composition and micro-structure,the results find out that compared with C70S6,36MnVS4 has higher tensile strength and yield strength,lower carbon content,more ferrite and greater grain size.Which shows that the tear is easier to occur in the cross section of 36MnVS4.The model is established based on joint modeling technique.Meanwhile,the model is meshed,and the boundary condition is processed,and the algorithm and some key techniques are set up.The finite element numerical simulation of two typical connecting rod fracture machining process is carried out,and the distribution of major mechanical fields in the initiation time and the crack propagation is gained.Many key information of two kinds of material connecting rod are compared and analyzed.These information including splitting load,crack initiation and its position and time,the crack propagation speed and stability after crack initiation,the stress release rate and plastic deformation and its value after fracture,and so on.According that,the problems of the new material36MnVS4 that is easy to occur in the splitting process are assessed preliminarily.In view of the importance of the rational design for prefabricated cracking groove,the influence of the groove geometric parameters on the splitting process of two kinds of material con-rod is discussed in this paper.Through the analysis of orthogonal test,the influence of the groove parameters on the splitting load was obtained,and the splitting groove parameters including the curvature radius,the groove depth and the angle.In order to further analyze the influence of the groove parameters on the splitting load,the crack initiation time and the stress concentration degree,the groove parameters are studied deeply.Finally,the optimum groove parameters are determined,and the defects and the precautions of 36MnVS4 are analyzed preliminarily.