Shape Optimization of a Single Cylinder Engine Crankshaft

Due to increasing demand for environment friendly vehicles with better fuel economy and strict legislations on greenhouse gas emissions, lightweight design has become one of the most important issues concerning the automobile industry. Within the scope of this work lightweight design potentials that a conventional single cylinder engine crankshaft offers are researched through utilization of structural optimization techniques. The objective of the study is to reduce mass and moment of inertia of the crankshaft with the least possible effect on the stiffness and strength. For precise definition of boundary conditions and loading scenarios multi body simulations are integrated into the optimization process. The loading conditions are updated at the beginning of each optimization loop, in which a multi body simulation of the output structure from the previous optimization loop is carried out. Equivalent static loads method, which is an embedded feature in OptiStruct, is applied to obtain the loading scenarios for the most critical time steps of the corresponding dynamic simulation. A number of variants of the problem are investigated according to assessment and optimization criteria and the promising results are introduced. The results show that more than 15% mass and mass inertia reduction is possible without any increase in stress values with ESLM based optimization approaches.