Structural Optimization of a Diesel Engine Crankshaft

In the past few years, Finite Element Analysis (FEA) has become an almost essential engineering tool in product development. In addition to that, structural optimization, which is almost as old as the finite element method, is a widely used tool in engineering product design definition. One vastly used method is the shape optimization, which has as an objective the minimization of stress concentration on determined regions. In this work, a 6 cylinder diesel engine crankshaft was analyzed and a structural optimization was performed, more specifically at the web region. The interpretation of the shape optimization results led to a slightly modified geometry of the crankshaft, with the mass of the crankshaft throw only 0.5% higher than the original model. Also, the fatigue safety factor evaluation was performed for both reference and optimized crankshafts as a comparison criterion. The same boundary condition used in the shape optimization was employed for the fatigue factor evaluation. The optimized crankshaft throw showed a 35% increase of the safety factor value for the back region of the web and a 22% increase in the front region of the web. Furthermore, dynamic flexible analysis also showed good results in terms of safety factor increase at this specific region.