| Connecting rod is a important part of internal combustion engine. The connecting rod plays a role that translates the linear motion of piston into the rotation motion of crankshaft, and realizes the function of power export. During the working process of engine, motion and stress status is very complex. The big end, the small end and the body of connecting rod have different motion form, and they bear periodically stress like compression, stretching and bending, In addition, with the strengthen of engine performance, and the cylinder pressure of a engine model is closed to 18 MPa. This requires much higher standard for the reliability. If the reliability does not meet the demand, the connecting rod will be damaged irreparably because of fatigue crack. Therefore, analysis of connecting rod has been a very important procedure during engine design.The connecting rod of a turbocharged and inter-cooled four-cylinder diesel engine was studied. The geometric models of connecting rod, piston, and crankshaft were established by Siemens NX8.0 software. After appropriate pretreatment, the simulation of multi-body dynamics for connecting rod was carried out by EXCITE-Power Unit software. The load spectrum that loaded on the small-end and big-end under different speeds were gotten, and the distribution characteristics of transient stress were gotten. Based on the load spectrum, the fatigue life of connecting rod during different speeds and conditions was simulated by FE-SAFE software. The fracture propagation life of connecting rod fatigue was predicted and analyzed by FRANC3D software. At last, the experiment program of fatigue crack testing was designed.The results show that:(1) With the cylinder pressure increase, the big end, the small end and the body transition area of connecting rod have several stress concentrations. The maximum stress is about 600MPa. It is under the allowable stress of material and it meets the design demand.(2) During the normal operation of engine and maximum torque condition, the fatigue life of connecting rod is the lowest. The cycle number of times is 1.86E7. The design demand is 1.00E7, and it meets the design requirement. Therefore, the connecting rod meets the design demand during the maximum torque condition(3) During the combined speed conditions, the cycle number of times is 5.97E7. The design demand is 1.00E7, and it meets the design requirement. So the fatigue strengththe of connecting rod meets the design requirements during all conditions;(4) During the normal operation of connecting rod, it can work for 3.00E5 times from the crack appearing to crack expanding and fracture. The cycle number is relatively short. When connecting rod exceeds its designed working life, it should be inspected regularly. Once the crack of connecting rod is discovered, it is better to replace the part to avoid catastrophic accident.
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