Safety evaluation of the rocker arm of a diesel engine

In order to evaluate the fatigue endurance for the rocker arm of a diesel engine, stress measurements were performed using strain gages attached near the neck, which is one of the most critical regions in the rocker arm, while varying the engine speed. Fatigue life experiments were carried out on miniature specimens taken from rocker arms. To evaluate the fatigue endurance of the rocker arm, the S–N data were compared with the stress analysis results obtained through a Finite Element Modelling (FEM) analysis of the rocker arm. The von-Mises effective stress of the rocker arm neck region was determined to be 22.4 MPa. The safety factors of this component are 2.6 and 3.8, based on the fatigue endurance limit and the modified fatigue endurance limit, respectively, suggesting that this safety factor is appropriate.