Papers by Author: Ryutaro Hino

Abstract: In this study, a new simulation-based design technique for multi-stage metal forming process is developed with special emphasis on reduction of stages in the process. The developed design technique is an iterative design optimization, which is based on response-surface-based numerical optimization and finite element analysis of the process. The design procedure starts with the initial rough process design. To eliminate one stage in the multi-stage process, the new optimum process design is determined based on the former process design by using numerical optimization in conjunction with FE simulation. This design optimization step is repeated, reducing the stages one by one, until the possible minimum number of stages is reached. The developed design technique is applied to stage reduction of a 3-stage axisymmetric forging process of aluminum billet. We can confirm that a new 2-stage process design is determined successfully and the developed design optimization technique is effective to reduce stages in multi-stage forming process.

Abstract: This paper deals with experimental observations and modeling of plastic deformations of a high strength steel sheet (HSS sheet) under biaxial stress conditions. Using a cruciform specimen of a HSS sheet of 980MPa-TS, experiments of proportional and non-proportional loadings were performed. Numerical simulations for the biaxial stress-strain responses were conducted using a constitutive model of large-strain cyclic plasticity (Yoshida-Uemori model), and the results were compared to the experimental data. The results of numerical simulation show a good agreement with the experimental results, which is attributed to accurate modeling of the backstress evolution of the anisotropic yield surface.