When an engine connecting rod is designed, it’s important to consider the buckling strength as well as deformation and durability of the rod. The buckling strength of a rod is mainly affected by the shape and area of shank cross-section and boundary conditions of its small and big ends. Buckling analysis by finite element method was carried out to evaluate the elastic buckling strength of a connecting rod that has non-uniform cross section areas. And the Merchant-Rankine formula was applied to predict the inelastic critical buckling load by considering the plastic buckling strength. Finally, the maximum allowable compressive load, which has 56.57kN, was predicted by considering the 1.7 buckling safety factor. It represents an approximately 40% greater than the maximum firing pressure.

The powder forging (PF) process is used to produce fully dense powder metallurgy (PM) parts for high performance automotive applications. PF connecting rods have been widely accepted in the US, Japan, and other countries due to higher performance and lower manufacturing costs when compared to conventionally forged steel connecting rods [1]. In order to meet and exceed requirements for higher fatigue strength and better machinability of PF connecting rods, a newly developed machinability enhancer, named KSX, was introduced [2]. A comparison study between powder forged materials prepared with 0.3% MnS and with 0.1% KSX additions showed excellent properties in the case of the mix with KSX.

Powder forging is a combined technology of powder metallurgy and precision hot forging. Recently, the technology is developing rapidly because of its economic merits, especially in automotive part manufacturing. In the present study, the finite element technique was developed to predict density variation during P/M forging and the technique was applied to analysis of forging of a P/M connecting rod. Although deformation mode of the connecting rod was quite complex, several sections were selected and analyzed under an assumption of asymmetric or plane strain deformation. It was found that some modifications were necessary on the cross section of the beam portion. Therefore, the cross section was modified repeatedly until a satisfactory result of the analysis was obtained. On the other hand, no modifications were necessary in the ring and the pin portions. It is anticipated that the developed technique can be used to optimize preform design and manufacturing processes in P/M forging, which are highly critical to produce successful products in practice.