The effect of connecting rod temperature on its high-cycle fatigue life

The complex loading that the connecting rod tolerates mandates an adequate solidity to withstand the applied forces. Therefore, it is necessary to precisely evaluate the stresses applied to the connecting rod and predict its fatigue life in the engine's actual operational conditions.The present study aimed to evaluate the impact of the connecting rod's temperaure on its high-cycle fatigue (HCF) life using the dynamic analysis of the connecting rod. The present study used the finite element method to analyze the HCF life. The ANSYS software was also used to predict the temperature, stresses, and HCF life through Goodman theory and nCode Design Life software.

The thermo-mechanical analysis results showed that neglecting connecting rod's temperaure results in an overestimation of the stress applied on the connecting rod by approximately 9.2 MPa (or 4.8%) than the actual limit, highlighting the critical impact of the thermal stress on the mechanical analysis and then fatigue life estimation of the connecting rod. The fatigue life analysis revealed that the minimum fatigue life of the connecting rod, considering and not considering thermal stress, was 2.904*109 and 2.634*109 cycles, respectively, observable in the area between the shank and small end of the connecting rod. Such findings indicated that disregarding temperature leads to an estimation of the HCF life of the connecting rod by approximately 0.27*109 cycles (10.3%) more than the actual limit.