INVESTIGATION OF FORMING LIMIT STRESS DIAGRAMS OF SHEET METALS

2005 ◽  
Vol 41 (07) ◽  
pp. 45 ◽  
Author(s):  
Ying Xie
Keyword(s):  
Forming Limit ◽  
Sheet Metals ◽  
Limit Stress

Fracture Prediction for Sheet Metals Subjected to Draw-Bending Using Forming Limit Stress Criterion

2013 ◽  
Author(s):  
Masazumi Saito ◽  
Toshihiko Kuwabara
Keyword(s):  
Sheet Metal ◽  
Steel Sheet ◽  
Fracture Criterion ◽  
Test Material ◽  
Forming Limit ◽  
Sheet Metals ◽  
Cross Sectional ◽  
Stress Criterion ◽  
Limit Stress ◽  
Draw Bending

Draw-bending is one of the typical deformation modes in sheet metal forming. It causes serious thickness reduction to sheet metals and very often leads to fracture. Therefore, it is crucial to establish a fracture criterion for sheet metals subjected to draw-bending. In this study, a fracture criterion for sheet metals subjected to draw-bending is investigated using the concept of the forming limit stress criterion. The test material used is a dual phase steel sheet (DP590Y) with a thickness of 1.2 mm and a tensile strength of 590 MPa. Draw-bending experiments of a wide specimen are performed using three different die profile radii: 4, 6 and 10 mm. The forming limit stress of the test material under draw-bending, σDB, is precisely determined from the experimentally measured drawing force and the cross sectional area of the specimen, determined from the strain distribution in the vicinity of fracture using a 2 mm square grid. In addition, multiaxial tube expansion tests are performed to measure the forming limit stress under plane strain tension, σPT. It is found that σDB almost coincides with σPT. Thus, it is concluded that σPT can be a fracture criterion for a sheet metal under draw-bending, at least for the high strength steel sheet used in this study.

Forming Limit Prediction of Sheet Metals Subjected to Combined Loading Using Forming Limit Stress Curve

2011 ◽  
Author(s):  
Fuminori Sugawara ◽  
Kengo Yoshida ◽  
Toshihiko Kuwabara ◽  
Naoki Taomoto ◽  
Naoki Yanagi ◽  
...  
Keyword(s):  
Combined Loading ◽  
Forming Limit ◽  
Sheet Metals ◽  
Stress Curve ◽  
Limit Stress

scholarly journals Forming Limit Stress Diagram Prediction of Pure Titanium Sheet Based on GTN Model

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1783 ◽  
Author(s):  
Tao Huang ◽  
Mei Zhan ◽  
Kun Wang ◽  
Fuxiao Chen ◽  
Junqing Guo ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Pure Titanium ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Forming Limit ◽  
Stress And Strain ◽  
Gtn Model ◽  
Stress Diagram ◽  
Limit Stress ◽  
Hemispherical Punch

In this paper, the initial values of damage parameters in the Gurson–Tvergaard–Needleman (GTN) model are determined by a microscopic test combined with empirical formulas, and the final accurate values are determined by finite element reverse calibration. The original void volume fraction (f0), the volume fraction of potential nucleated voids (fN), the critical void volume fraction (fc), the void volume fraction at the final failure (fF) of material are assigned as 0.006, 0.001, 0.03, 0.06 according to the simulation results, respectively. The hemispherical punch stretching test of commercially pure titanium (TA1) sheet is simulated by a plastic constitutive formula derived from the GTN model. The stress and strain are obtained at the last loading step before crack. The forming limit diagram (FLD) and the forming limit stress diagram (FLSD) of the TA1 sheet under plastic forming conditions are plotted, which are in good agreement with the FLD obtained by the hemispherical punch stretching test and the FLSD obtained by the conversion between stress and strain during the sheet forming process. The results show that the GTN model determined by the finite element reverse calibration method can be used to predict the forming limit of the TA1 sheet metal.

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