Abstract
This paper deals with the fatigue life prediction of a manual transmission housing considering the effect of the stress gradient at the fatigue critical location. It was proposed that the critical distance is not just a material property and it is also a function of the notch geometry. This method was named as a “Variable critical distance” method and it offers to consider the effect of geometry on the critical distance. Laboratory tests were conducted to obtain several fatigue fracture locations using customized loads & high cycle fatigue lives for different load cases were reported. Finite element simulation model was used to determine the stress gradients at various fatigue fracture locations and were represented by their respective “Stress Gradient Factors (SGF)” for each of these locations. Different critical distances were derived using SGF in the proposed method. Out of the different available schemes, critical distance point scheme was implemented to determine the fatigue life under the different loading conditions. While conventional surface stress based fatigue life prediction method showed a large underestimation of fatigue life compared to lab test results and the constant critical distance method also resulted in the comparable difference between the simulation and test results, the variable critical distance method showed a good correlation of the fatigue life.