The main topic of this study is a shape design of a crane-hook. In order to improve its performance and service life, a development of a high quality product has been required. In a practical design scene, elastoplastic deformation analysis is rarely done. Thus, we discuss a crane-hook design based on the elastoplastic deformation analysis. A constitutive equation of our model is constructed by a piecewise linear function. A yield stress and tangent modulus are decided empirically. The displacement between specified points and a structural weight of crane-hook are adopted as the evaluation items to be minimized. The height of each cross-section and the width of each layer in the cross-section are chosen as the design variables in the shape design. For this multi-objective optimization problem with two items, we convert it into the single-objective optimization problem using weighting sum method. By changing the weighting factors, Pareto optima are obtained. As a common feature of shapes on a Pareto line, the obtained designs have tapered shapes similar to those of existing designs.
