Design, Analysis and Application of a Novel Test for Sheet Metal Forming Limits under Non-Planar Stress States

2011 ◽  
Author(s):  
Julian M. Allwood ◽  
Daniel R. Shouler
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Design Analysis ◽  
Forming Limits ◽  
Stress States

Sheet metal forming limits as classification problem

2017 ◽  
Author(s):  
Christian Jaremenko ◽  
Xiaolin Huang ◽  
Emanuela Affronti ◽  
Marion Merklein ◽  
Andreas Maier
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Classification Problem ◽  
Forming Limits

scholarly journals Recent Approaches for the Determination of Forming Limits by Necking and Fracture in Sheet Metal Forming

2015 ◽  
Vol 132 ◽  
pp. 342-349 ◽  
Author(s):  
M.B. Silva ◽  
A.J. Martínez-Donaire ◽  
G. Centeno ◽  
D. Morales-Palma ◽  
C. Vallellano ◽  
...  
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limits

Prediction and analysis of ductile fracture in sheet metal forming—Part I: A modified Ayada criterion

2014 ◽  
Vol 23 (8) ◽  
pp. 1189-1210 ◽  
Author(s):  
HS Liu ◽  
MW Fu
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Ductile Fracture ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Fracture Criterion ◽  
Ductile Fracture Criterion ◽  
Wide Range ◽  
Stress States

A modified ductile fracture criterion is proposed based on the traditional Ayada criterion and coded into the finite element simulation platform of VUMAT/ABAQUS for prediction and analysis of ductile fracture in metal plastic strain processes. In this modified ductile fracture criterion, stress triaxiality is taken into account, and more importantly, the exponential effect of the equivalent plastic strain on the damage behavior, which is generally ignored in other ductile fracture criteria, is also considered. The material related constants in the modified ductile fracture criterion are determined by tensile tests together with finite element simulations. The applicability and reliability of the ductile fracture criterion in ductile fracture prediction in two types of classic stress states, viz. shear stress, tensile stress in sheet metal forming, are investigated based on the deformation behavior and fracture occurrence in two case studies with two typical types of materials, i.e. Al 6061 and T10A. The materials have a wide range of plasticity. The simulation and experimental results verify the applicability and reliability of the developed ductile fracture criterion in prediction of the ductile fracture with and without necking in different stress states of plastic strain.

Forming Limits of a Sheet Metal After Continuous-Bending-Under-Tension Loading

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Ji He ◽  
Z. Cedric Xia ◽  
Danielle Zeng ◽  
Shuhui Li
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Loading Condition ◽  
Hybrid Approach ◽  
Forming Limit ◽  
Forming Limits ◽  
Continuous Bending ◽  
Bending Under Tension

Forming limit diagrams (FLD) have been widely used as a powerful tool for predicting sheet metal forming failure in the industry. The common assumption for forming limits is that the deformation is limited to in-plane loading and through-thickness bending effects are negligible. In practical sheet metal applications, however, a sheet metal blank normally undergoes a combination of stretching, bending, and unbending, so the deformation is invariably three-dimensional. To understand the localized necking phenomenon under this condition, a new extended Marciniak–Kuczynski (M–K) model is proposed in this paper, which combines the FLD theoretical model with finite element analysis to predict the forming limits after a sheet metal undergoes under continuous-bending-under-tension (CBT) loading. In this hybrid approach, a finite element model is constructed to simulate the CBT process. The deformation variables after the sheet metal reaches steady state are then extracted from the simulation. They are carried over as the initial condition of the extended M–K analysis for forming limit predictions. The obtained results from proposed model are compared with experimental data from Yoshida et al. (2005, “Fracture Limits of Sheet Metals Under Stretch Bending,” Int. J. Mech. Sci., 47(12), pp. 1885–1986) under plane strain deformation mode and the Hutchinson and Neale's (1978(a), “Sheet Necking—II: Time-Independent Behavior,” Mech. Sheet Metal Forming, pp. 127–150) M–K model under in-plane deformation assumption. Several cases are studied, and the results under the CBT loading condition show that the forming limits of post-die-entry material largely depends on the strain, stress, and hardening distributions through the thickness direction. Reduced forming limits are observed for small die radius case. Furthermore, the proposed M–K analysis provides a new understanding of the FLD after this complex bending-unbending-stretching loading condition, which also can be used to evaluate the real process design of sheet metal stamping, especially when the ratio of die entry radii to the metal thickness becomes small.

A New Approach to the Evaluation of Forming Limits in Sheet Metal Forming

2015 ◽  
Vol 639 ◽  
pp. 333-338 ◽  
Author(s):  
Marion Merklein ◽  
Andreas Maier ◽  
Daniel Kinnstätter ◽  
Christian Jaremenko ◽  
Emanuela Affronti
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Strain History ◽  
Failure Behavior ◽  
Forming Limits ◽  
Optical Strain Measurement ◽  
Optical Strain

The forming limit diagram (FLD) is at the moment the most important method for the prediction of failure within sheet metal forming operations. Key idea is the detection of the onset of necking in dependency of different sample geometry. Whereas the standardized evaluation methods provides very robust and reliable results for conventional materials like deep drawing steels, the determined forming limits for modern light materials are often too conservative due to the different failure behavior. Therefore, within this contribution a new and innovative approach for the identification of the onset of necking will be presented. By using a pattern recognition-based approach in combination with an optical strain measurement system the complete strain history during the test can be evaluated. The principal procedure as well as the first promising results are presented and discussed.

Sheet Metal Forming Limits Under Complex Strain Paths Using Void Growth and Coalescence Model

1986 ◽  
Vol 108 (3) ◽  
pp. 240-244 ◽  
Author(s):  
U. S. Rao ◽  
R. C. Chaturvedi
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Void Growth ◽  
Metal Forming ◽  
Strain Ratio ◽  
Forming Limits ◽  
Coalescence Model ◽  
Strain Paths ◽  
Complex Strain ◽  
Void Growth And Coalescence

It is well established that ductile fracture occurs by nucleation, growth and coalescence of voids. Several models have been developed to predict limits under constant strain ratio paths considering void inhomogeneity and void growth. In this paper the void growth and coalescence model developed by Rao and Chaturvedi for predicting forming limits under constant strain ratio paths, has been extended for predicting forming limits under two stage strain paths. The predicted results have been compared with experimental results of Ishigaki and analyzed.

scholarly journals Advances in characterization of sheet metal forming limits

2016 ◽  
Vol 734 ◽  
pp. 032073 ◽  
Author(s):  
Thomas B. Stoughton ◽  
John E. Carsley ◽  
Junying Min ◽  
Jianping Lin
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limits
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