Experimental and Visco-Plastic Self-Consistent evaluation of forming limit diagrams for anisotropic sheet metals: An efficient and robust implementation of the M-K model

2015 ◽  
Vol 73 ◽  
pp. 62-99 ◽  
Author(s):  
C. Schwindt ◽  
F. Schlosser ◽  
M.A. Bertinetti ◽  
M. Stout ◽  
J.W. Signorelli
Keyword(s):  
Forming Limit ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Robust Implementation ◽  
Self Consistent

Formability of High Strength Sheet Metals with Special Regard to the Effect of the Influential Factors on the Forming Limit Diagrams

2015 ◽  
Vol 812 ◽  
pp. 271-275 ◽  
Author(s):  
Miklós Tisza ◽  
Péter Zoltán Kovács ◽  
Zsolt Lukács ◽  
Antal Kiss ◽  
Gaszton Gál
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Experimental Investigations ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Research Activities

Car manufacturing is one of the main target fields of sheet metal forming: thus sheet metal forming is exposed to the same challenges as the automotive industry. The continuously increasing demand on lower consumption and lower CO2 emission means the highest challenges on materials developments besides design and construction. As a general requirement, the weight reduction and light weight construction principles should be mentioned together with the increased safety prescriptions which require the application of high strength steels. However, the application of high strength steels often leads to formability problems. Forming Limit Diagrams (FLD) are the most appropriate tools to characterize the formability of sheet metals. Theoretical and experimental investigations of forming limit diagrams are in the forefront of todays’ research activities.

Effect of Plastic Anisotropy on Forming Limit Prediction

2005 ◽  
Vol 495-497 ◽  
pp. 1573-1578 ◽  
Author(s):  
S. He ◽  
Albert Van Bael ◽  
Paul van Houtte
Keyword(s):  
Strain Path ◽  
Plastic Anisotropy ◽  
Yield Locus ◽  
Material Behavior ◽  
Forming Limit ◽  
Sheet Metals ◽  
Forming Process ◽  
Forming Limit Diagrams ◽  
Strain Path Changes ◽  
Complex Strain

A model based on Marciniak-Kuczynski (M-K) theory [1] for the prediction of forming limit diagrams (FLDs) for anisotropic sheet metals is presented. The plastic anisotropy is taken into account by the shape of the yield locus generated on the basis of measured crystallographic texture. As a result, not only the material behavior during the monotonic loading can be well described and predicted, but also the complex strain-path changes during the forming process can be taken into account. Examples of predicted FLDs for two aluminum alloys are given. Comparisons with experimental results are presented.

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 The secondary forming limit diagrams of sheet metals.

1985 ◽  
Vol 51 (469) ◽  
pp. 2224-2230 ◽  
Author(s):  
Manabu GOTOH ◽  
Takeshi SATOH ◽  
Kozo TANAKA
Keyword(s):  
Forming Limit ◽  
Sheet Metals ◽  
Forming Limit Diagrams

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.

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