Buckling sensitivity of a connecting rod to the shank sectional area reduction

Yield, fatigue and buckling characteristics are often used as evaluation indexes for the performance of engine connecting rods in weight reduction design. There are, however, a limited number of studies on the buckling of connecting rods. Even the widely used field equations for the buckling have limitations in the application since they are derived from ideal support conditions. This study first presents an evaluation procedure for the buckling of a connecting rod via finite element analysis (FEA). The FEA approach allows us to treat the first and second modes of buckling collectively. The buckling stresses from the suggested FEA approach are closer to those measured in rig experiments than those from classical formula are. The stress sensitivities to the area reduction of rod shank are then examined in lights of yield, fatigue and buckling. The stress sensitivity in buckling indicates to be relatively higher than or comparable to those of yield and fatigue. Consequently, when weight reduction of connection rod shank is attempted, buckling should be considered as an essential factor along with the other criteria such as yield and fatigue.