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Title: Theoretical Prediction of the Forming Limit Band

Abstract

Forming Limit Band (FLB) is a very useful tool to improve the sheet metal forming simulation robustness. Until now, the study of the FLB was only experimental. This paper presents the first attempt to model the FLB. The authors have established an original method for predicting the two margins of the limit band. The method was illustrated on the AA6111-T43 aluminum alloy. A good agreement with the experiments has been obtained.

Authors:
;  [1];  [2];  [3]
  1. Centre of Research for Sheet Metal Forming Technology 'CERTETA', Technical University of Cluj Napoca, 15 C.Daicoviciu, Cluj Napoca (Romania)
  2. ELKEM, Hoffsveien 65 B, Majorstuen, NO-0303 Oslo (Norway)
  3. FORTECH, 6 C. Brancoveanu, 40467 Cluj Napoca (Romania)
Publication Date:
OSTI Identifier:
21057036
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 907; Journal Issue: 1; Conference: 10. ESAFORM conference on material forming, Zaragoza (Spain), 18-20 Apr 2007; Other Information: DOI: 10.1063/1.2729541; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINIUM ALLOYS; COMPUTERIZED SIMULATION; MATERIALS WORKING; METALS; NUMERICAL ANALYSIS; SHEETS

Citation Formats

Banabic, D., Paraianu, L., Vos, M., and Jurco, P.. Theoretical Prediction of the Forming Limit Band. United States: N. p., 2007. Web. doi:10.1063/1.2729541.
Banabic, D., Paraianu, L., Vos, M., & Jurco, P.. Theoretical Prediction of the Forming Limit Band. United States. doi:10.1063/1.2729541.
Banabic, D., Paraianu, L., Vos, M., and Jurco, P.. Sat . "Theoretical Prediction of the Forming Limit Band". United States. doi:10.1063/1.2729541.
@article{osti_21057036,
title = {Theoretical Prediction of the Forming Limit Band},
author = {Banabic, D. and Paraianu, L. and Vos, M. and Jurco, P.},
abstractNote = {Forming Limit Band (FLB) is a very useful tool to improve the sheet metal forming simulation robustness. Until now, the study of the FLB was only experimental. This paper presents the first attempt to model the FLB. The authors have established an original method for predicting the two margins of the limit band. The method was illustrated on the AA6111-T43 aluminum alloy. A good agreement with the experiments has been obtained.},
doi = {10.1063/1.2729541},
journal = {AIP Conference Proceedings},
number = 1,
volume = 907,
place = {United States},
year = {Sat Apr 07 00:00:00 EDT 2007},
month = {Sat Apr 07 00:00:00 EDT 2007}
}
  • The experimental research on the formability of metal sheets has shown that there is a significant dispersion of the limit strains in an area delimited by two curves: a lower curve (LFLC) and an upper one (UFLC). The region between the two curves defines the so-called Forming Limit Band (FLB). So far, this forming band has only been determined experimentally. In this paper the authors suggested a method to predict the Forming Limit Band. The proposed method is illustrated on the AA6111-T43 aluminium alloy.
  • The paper analyzes the dispersion of the mechanical parameters and its influence on the forming limit curves of sheet metals. The tests have been made for the case of the DC01 steel sheets. The dispersion of the mechanical parameters has been observed during the experimental research. On the basis of this dispersion, a forming limit band has been calculated using an alternate formulation of Hora's model (MMFC).
  • Several researchers have proposed analytical methods for predicting the forming limit curve (FLC), which has been successfully used as a diagnostic tool in sheetmetal forming. However, these approaches lack ease of adaptability to various situations and also involve considerable complexity. Sing and Rao proposed a new FLC modeling approach based on limit stress states derived from yield criterion and material properties from a simple tensile test. The first aspect of this study addresses the influence of the shape of the forming limit stress curve (FLSC) upon the FLC. The FLC modeled from a singly linear FLSC exhibits good agreement withmore » the experimental curve, unlike those modeled from an elliptical or a piecewise linear FLSC. It is, thus, established that a linearized limit stress locus describes adequately the actual localized neck condition for the materials chosen in this study. Second, the study focuses on the suitability of the different cases of Hill`s yield criterion for satisfactory prediction of FLCs. The FLCs predicted using different cases of Hill`s criterion are compared with experimental FLCs in the case of steel and copper. Different cases of Hill`s criterion provide a wider choice for FLC modeling for different classes of materials. The sensitivity of Hill`s stress exponent is also thoroughly explored for achieving a close correspondence between the predicted and experimental FLCs.« less
  • Stainless steels as well as TRIP and TWIP steels show a hardening behavior, which can be described only in dependency on the deformation and temperature history during the real forming process. Because the hardening behavior is the determinate factor for the necking phenomenon, the prediction of rupture becomes also deformation path and temperature dependent. As a consequence, the common FLC-method, using a single curve for the prediction of the failure state is not accurate enough. In this paper, a temperature dependent Forming Limit Surface (FLS) is presented.
  • The use of lightweight materials offers substantial strength and weight advantages in car body design. Unfortunately such kinds of sheet material are more susceptible to wrinkling, spring back and fracture during press shop operations. For characterization of capability of sheet material dedicated to deep drawing processes in the automotive industry, mainly Forming Limit Diagrams (FLD) are used. However, new investigations at the Institute for Metal Forming Technology have shown that High Strength Steel Sheet Material and Aluminum Alloys show increased formability in case of bending loads are superposed to stretching loads. Likewise, by superposing shearing on in plane uniaxial ormore » biaxial tension formability changes because of materials crystallographic texture. Such mixed stress and strain conditions including bending and shearing effects can occur in deep-drawing processes of complex car body parts as well as subsequent forming operations like flanging. But changes in formability cannot be described by using the conventional FLC. Hence, for purpose of improvement of failure prediction in numerical simulation codes significant failure criteria for these strain conditions are missing. Considering such aspects in defining suitable failure criteria which is easy to implement into FEA a new semi-empirical model has been developed considering the effect of bending and shearing in sheet metals formability. This failure criterion consists of the combination of the so called cFLC (combined Forming Limit Curve), which considers superposed bending load conditions and the SFLC (Shear Forming Limit Curve), which again includes the effect of shearing on sheet metal's formability.« less