成長ひずみ法によるコンロッドの形状最適化の解析

概要

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Because of space restrictions and the necessity of minimum mass, the connecting rod is one of the more heavily stressed parts of the car engine. The heaviest load occurs by gas pressure during firing at the top dead center position of the piston. The second is tensile load which occurs by the inertia force of the piston assembly mass and around the small end of the connecting rod mass. The third stress due to a lateral inertia, or “whip” of the connecting rod is usually negligibly small. In this paper we investigated the optimization of the shape of the normal connecting rod for the car engine, applying the growth-strain method. The analyses were done in case of compressive and tensile loads separately. The growth criterion parameters of the principal stress on the connecting rod were determined from the fatigue strength of the original design data and the actual safety factor. We thought that it is most compatible to use the fatigue strength which is the safety side, smallest value of the material constants, because the connecting rod receives the reciprocating compressive and tensile hard loads. After analysis, the optimized configurations of the connecting rod were compared with that of the original one. Then the reduction rate of the volume of the optimized connecting rod was approximately 22.8%.