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Material Models for Accurate Simulation of Sheet Metal Forming and Springback
Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6
For anisotropic sheet metals, modeling of anisotropy and the Bauschinger effect is discussed in the framework of Yoshida-Uemori kinematic hardening model incorporating with anisotropic yield functions. The performances of the models in predicting yield loci, cyclic stress-strain responses on several types of steel and aluminum sheets are demonstrated by comparing the numerical simulation results with the corresponding experimental observations. From some examples of FE simulation of sheet metal forming and springback, it is concluded that modeling of both the anisotropy and the Bauschinger effect is essential for the accurate numerical simulation.
Reduction of Springback of Sheet Metals by Bottoming
Takayuki Ogawa,Atsushi Hirahara,Fusahito Yoshida 한국소성가공학회 2010 기타자료 Vol.2010 No.6
The effect of bottoming on the reduction of springback is investigated by performing V-air-bending experiment on a high strength steel sheet of TS590MPa and the corresponding FE simulation. From the experiment, it was found that the springback is drastically decreased with increasing bottoming force. This is mainly due to the reduction of bending moment by compressive load acting normally to the sheet. At an early stage of bottoming, springback is also influenced by the change of geometrical rigidity of the bent sheet due to the straightening of ridge line warp. Since bottoming is a process of reverse deformation of tension-compression, the Bauschinger effect of materials should be taken into account for its accurate numerical simulation. 3D FE simulation using Yoshida-Uemori kinematic hardening model predicts well the bottoming effect.
Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling
Shohei TAMURA,Satoshi SUMIKAWA,Hiroshi HAMASAKI,Takeshi UEMORI,Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6
To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r?, r45 and r90), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh’s biquadratic yield function and Barlat’s Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model)
Bendability of Aluminium- and Steel-Clad Chromium Plates
Okada, Tatsuo,Yoshida, Fusahito,Itoh, Misao,Harada, Yasunori,Ohmori, Masanobu 대한금속재료학회(대한금속학회) 1998 METALS AND MATERIALS International Vol.4 No.3
The present paper describes how the cladding of chromium plate with dissimilar metals improves the plastic bendability of the chromium. Three-point bending tests at various temperatures were performed for three types of chromium specimens: a monolithic chromium plate, aluminium- and steel-clad chromium plate. The aluminium-clad chromium plate was bent at 343 K up to a bent angle of 90 degrees without failure, even when the chromium layer was located outside of the plate (tension side), while the monolithic chromium plate could be bent exclusively at temperatures above 403 K. When the chromium layer was located inside of the steel-clad chromium plate (compression side), the plate was successfully bent at 307 K. The FE stress analysis of bending proved that the cladding of chromium plates with proper metals of different kinds is effective to reduce the tensile stress in chromium induced during bending and also the residual stress existing after bending operation.
Uemori, Takeshi,Okada, Tatsuo,Yoshida, Fusahito 대한금속재료학회(대한금속학회) 1998 METALS AND MATERIALS International Vol.4 No.3
This paper presents the prediction of springback in sheet metal forming in terms of the description of the Bauschinger effect. It addresses three different types of constitutive models: an iso-tropic hardening model (IH model), a linearly kinematic hardening model (LK model), and a model of combined linearly-nonlinearly kinematic and isotropic hardening (L-NK+IH model). The springback predicted by the L-NK+IH model is found to be more pronounced than that by the IH and the LK model. It is caused by the stress-strain response characterized by the gradual transition from fully elastic to plastic behavior during stress-reversal, which is essential to the L-NK+IH model.