Materials optimization of a connecting rod using FGM

Abstract

A connecting rod should be designed with high reliability, being sufficiently strong to remain rigid under mechanical loads, yet lightweight enough to reduce the inertia forces, which are produced when the rod and piston stop, reverse directions, and accelerate again at the end of each stroke. In this study, a traditionally designed steel-forged connecting rod is used as a baseline. The concept of Function Graded Materials (FGM) is introduced as an alternative to conventional steel. A three-dimensional model of the connecting rod is constructed and analyzed by finite element method (FEM) with the ANSYS software package to evaluate the stresses distribution over the entire rod. In addition, transient and force analyses are performed, and the results are validated through computer simulations. It is well established that improvements in connecting rod design directly enhance engine performance by increasing reliability, service life, efficiency, fuel economy, and reducing noise, size, weight, and vibration. This study investigates the impact of functionally graded materials on connecting rod performance and aims to optimize the design to reduce maximum von Mises stress in critical regions. The analysis is conducted using FEA software, with comprehensive modeling and simulation results presented in detail. To achieve optimization, three material compositions (aluminum–steel, aluminum–titanium, and titanium–steel) are evaluated. The most effective composition is identified based on performance. Theoretical analysis suggests that manufacturing an FGM-based connecting rod using a bulk layering process is feasible. From a stress standpoint, the aluminum–titanium composite provides the best performance, showing a 49.4 % stress reduction compared to the steel connecting rod. However, due to its higher cost, the aluminum–steel composite offers a more balanced solution, achieving a 44 % stress reduction while being more cost-effective.