scholarly journals Two-scale approach to dynamic localization failure of AISI 316H stainless steel sheets

2008 ◽  
Vol 35 (1-3) ◽  
pp. 93-103
Author(s):  
W. Gambin ◽  
K. Kowalczyk-Gajewska ◽  
L.T. Kudrjavceva ◽  
M.V. Micunovic
Keyword(s):  
Thin Sheet ◽  
Forming Limit ◽  
Dynamic Localization ◽  
Forming Limit Diagrams ◽  
Steel Sheets ◽  
Plastic Dissipation ◽  
Mesoscopic Level ◽  
Independent Variable ◽  
Single Grain ◽  
Equivalent Yield

Dynamic localization failure of a thin sheet made of AISI 316H steel is considered on the macroscopic and mesoscopic level for proportional and nonproportional stress paths. On the macroscopic level, we propose: (1) the replacement of time as independent variable by a function of plastic dissipation and (2) dependence of the initial equivalent yield stress on stress rate. On the mesoscopic level - the regularized Schmid model for description of the single grain behavior is used and the polycrystalline yield surface generated by the texture development enables to improve the Forming Limit Diagrams for the sheet element.

Influence of Pre-Forming on the Forming Limit Diagram of Aluminum and Steel Sheets

2007 ◽  
Vol 344 ◽  
pp. 113-118 ◽  
Author(s):  
Massimo Tolazzi ◽  
Marion Merklein
Keyword(s):  
Dual Phase Steel ◽  
Process Analysis ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Linear Strain ◽  
Forming Limit Diagrams ◽  
Steel Sheets ◽  
Biaxial Stretching ◽  
Strain Paths

This paper presents a method for the experimental determination of forming limit diagrams under non linear strain paths. The method consists in pre-forming the sheets under two different strain conditions: uniaxial and biaxial, and then stretching the samples, cut out of the preformed sheets, using a Nakajima testing setup. The optical deformation measurement system used for the process analysis (ARAMIS, Company GOM) allows to record and to analyze the strain distribution very precisely with respect to both time and space. As a reference also the FLDs of the investigated grades (the deep drawing steel DC04, the dual phase steel DP450 and the aluminum alloy AA5754) in as-received conditions were determined. The results show as expected an influence of the pre-forming conditions on the forming limit of the materials, with an increased formability in the case of biaxial stretching after uniaxial pre-forming and a reduced formability for uniaxial load after biaxial stretching if compared to the case of linear strain paths. These effects can be observed for all the investigated materials and can be also described in terms of a shifting of the FLD, which is related to the art and magnitude of the pre-deformation.

scholarly journals Forming Limit Diagrams of Ground St14 Steel Sheets with Different Thicknesses

2012 ◽  
Vol 5 (1) ◽  
pp. 60-64 ◽  
Author(s):  
Ramin Hashemi ◽  
Amir Ghazanfari ◽  
Karen Abrinia ◽  
Ahmad Assempour
Keyword(s):  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Steel Sheets ◽  
St14 Steel

scholarly journals Forming Limit Diagrams of Perforated St12 Steel Sheets

2021 ◽  
Author(s):  
M. Hossein Sehhat ◽  
Ali Mahdianikhotbesara ◽  
Mohammadjafar Hadad
Keyword(s):  
Forming Limit ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Maximum Deformation ◽  
Steel Sheets ◽  
Deformation Limit ◽  
Metal Sheets ◽  
Perforated Sheets ◽  
Nakajima Test ◽  
Hemispherical Punch

Abstract One of the unique characteristics of sheet metals is their formability, which is determined by the forming limit diagrams. These diagrams specify the maximum deformation limit before part’s failure. For several applications of metal sheets, they have to be in the perforated format. Existence of holes in the perforated sheets may adversely deteriorate the forming limit of metal sheets. In this study, the effect of perforated sheets’ hole size and hole layout on their formability are investigated. Several specimens of St12 steel with 0.6 mm thickness, different widths, two various hole sizes of 2 and 4 mm, and two layouts of triangular and square were prepared. The specimens were tested using Nakajima test (stretch with a hemispherical punch) to generate the forming limit diagrams. It was observed that both the diameter and layout of the punched holes have a significant effect on the formability of the perforated sheets. The perforated sheets with triangular hole layout showed higher forming limits due to their larger ligament ratios.

scholarly journals Prediction of necking in thin sheet metals using an elastic–plastic model coupled with ductile damage and bifurcation criteria

2017 ◽  
Vol 27 (6) ◽  
pp. 801-839 ◽  
Author(s):  
Yasser Bouktir ◽  
Hocine Chalal ◽  
Farid Abed-Meraim
Keyword(s):  
Plane Stress ◽  
Thin Sheet ◽  
Three Dimensional ◽  
Ductile Damage ◽  
Forming Limit ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Plastic Model ◽  
Elastic Plastic ◽  
Localized Necking

In this paper, the conditions for the occurrence of diffuse and localized necking in thin sheet metals are investigated. The prediction of these necking phenomena is undertaken using an elastic–plastic model coupled with ductile damage, which is then combined with various plastic instability criteria based on bifurcation theory. The bifurcation criteria are first formulated within a general three-dimensional modeling framework, and then specialized to the particular case of plane-stress conditions. Some theoretical relationships or links between the different investigated bifurcation criteria are established, which allows a hierarchical classification in terms of their conservative character in predicting critical necking strains. The resulting numerical tool is implemented into the finite element code ABAQUS/Standard to predict forming limit diagrams, in both situations of a fully three-dimensional formulation and a plane-stress framework. The proposed approach is then applied to the prediction of diffuse and localized necking for a DC06 mild steel material. The predicted forming limit diagrams confirm the above-established theoretical classification, revealing that the general bifurcation criterion provides a lower bound for diffuse necking prediction, while the loss of ellipticity criterion represents an upper bound for localized necking prediction. Some numerical aspects related to the prestrain effect on the development of necking are also investigated, which demonstrates the capability of the present approach in capturing the strain-path changes commonly encountered in complex sheet metal forming operations.

scholarly journals Numerical Prediction of the Forming Limit Diagrams of Thin Sheet Metal using SPIF Tests

2017 ◽  
Vol 183 ◽  
pp. 113-118 ◽  
Author(s):  
Ben Hmida Ramzi ◽  
Thibaud Sebastien ◽  
Richard Fabrice ◽  
Hapsari Gemala ◽  
Malécot Pierrick
Keyword(s):  
Sheet Metal ◽  
Thin Sheet ◽  
Numerical Prediction ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Thin Sheet Metal

Forming limit diagrams of zinc and zinc alloy coated steel sheets

1994 ◽  
Vol 31 (5) ◽  
pp. 613-618 ◽  
Author(s):  
Jae Wook Kwon ◽  
Dong Nyung Lee ◽  
Insoo Kim
Keyword(s):  
Forming Limit ◽  
Zinc Alloy ◽  
Coated Steel ◽  
Forming Limit Diagrams ◽  
Steel Sheets

scholarly journals Forming Limit Diagrams of Perforated St12 Steel Sheets

2021 ◽  
Author(s):  
M. Hossein Sehhat ◽  
Ali Mahdianikhotbesara ◽  
Mohammadjafar Hadad
Keyword(s):  
Forming Limit ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Maximum Deformation ◽  
Steel Sheets ◽  
Deformation Limit ◽  
Metal Sheets ◽  
Perforated Sheets ◽  
Nakajima Test ◽  
Hemispherical Punch

Abstract One of the unique characteristics of sheet metals is their formability, which is determined by the forming limit diagrams. These diagrams specify the maximum deformation limit before part’s failure. For several applications of metal sheets, they have to be in the perforated format. Existence of holes in the perforated sheets may adversely deteriorate the forming limit of metal sheets. In this study, the effect of perforated sheets’ hole size and hole layout on their formability are investigated. Several specimens of St12 steel with 0.6 mm thickness, different widths, two various hole sizes of 2 and 4 mm, and two layouts of triangular and square were prepared. The specimens were tested using Nakajima test (stretch with a hemispherical punch) to generate the forming limit diagrams. It was observed that both the diameter and layout of the punched holes have a significant effect on the formability of the perforated sheets. The perforated sheets with triangular hole layout showed higher forming limits due to their larger ligament ratios.

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