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Nowadays, the mechanical design of automotive connecting rods is essentially guided by analytic calculations followed by numeric methods to assess the stresses, displacements, contact pressures, fatigue and buckling. The present work, applies an alternative methodology based on the method of topology optimization to design the connecting rod aiming mass reduction. Two connecting rods designs were developed using two different methodologies, which the methodology considering the topology optimization generated a 3% lighter connecting rod and with improved lubrication performance when compared with the conventional design obtained from the current design methodology.

Automotive internal combustion engines use connecting rods to compose its mechanical set-up based on a piston-rod-crank mechanism. Typically, a connecting rod has an i-shaped beam along its length in order to have better moment of inertia distribution on two axes, one aligned to the engine rotating axis and other, orthogonal to the same. An alternative design was developed by the use of an oval shaped beam in order concentrate the moment of inertia just along the engine rotating axis. The structural simulations based on Finite Element Analysis showed that the fatigue and buckling strength were maintained and finally, experimental fatigue testing had proven that oval beam design kept the fatigue and also buckling strength

Connecting rods of internal combustion engines usually apply a bolted joint solution at the big end for the assembly with the crankshaft, and in addition, to simplify disassembling. Consequently, a typical engine connecting rod is formed by a stem and a cap that are joined by bolts. However, the engine dynamic loads can be enough to overload the joint causing the cap detachment of the stem. Therefore, the main goal of this paper is to evaluate if the engine dynamic loads are sufficient to cause the unilateral opening of the joint surface that can lead to a catastrophic failure of the engine. The calculation is done by analytical approach and also, by finite element model. The analytical formulation achieved critical results based on conservative hypotheses, while the numerical results indicated a certain security regarding the unilateral opening of the joint surface, pointing to the direction of bolted joints development based on finite element models.