Analysis on technology and defects of fracture splitting of automobile engine connecting rod

Abstract

The principle of connecting rod (con-rod) fracture splitting was analyzed, and the microscopic morphology of fracture surface was observed using scanning electron microscope. Crack initiation and propagation during the fracture splitting of con-rod process was numerically simulated. The effects of the bolt hole on the fracture splitting force and distribution of stress and strain were investigated. Typical location of fracture splitting defects and why they were generated were analyzed, and methods were proposed to avoid them. The results show that the nature of con-rod fracture splitting is a mode I quasi-brittle fracture, and the position of crack initiation can be found during the analysis process. Existence of the bolt hole is helpful to optimize fracture splitting technology and improve product quality, and the optimized range of bolt hole position was achieved based on simulation result. Moreover, defects such as steps, break-outs, usually occur between the bolt hole wall and outer edge of the con-rod big end in that two cracks converged and propagation velocity was slow in this region. The fracture splitting defects can be reduced or avoided when the outer shape of the fracture surface is a circular arc.

Study on Fracture-Split Performance of 36MnVS4 and Analysis of Fracture-Split Easily-Induced Defects

“…The grain fineness number of the C70S6 is lower. The high-hardness lamellar cementite of the C70S6 reduces its machinability [23]. The 36MnVS4 is mainly composed of pearlite and ferrite.…”

New controllable and near net bar fine-cropping system

“…[3][4][5][6][7] Besides, as known, the V-groove can induce the stress concentration effect. [8][9][10][11] The cropping time and the cropping load, which directly affect the efficiency and the energy consumption, can be greatly reduced by the stress concentration effect. Some new different lowstress bar fine-cropping methods have been proposed based on the stress concentration in the last two decades.…”