Effect of Yield Criterion on Numerical Simulation Results Using a Stress-Based Failure Criterion

2006 ◽  
Vol 128 (3) ◽  
pp. 436-444 ◽  
Author(s):  
Aaron Sakash ◽  
Sumit Moondra ◽  
Brad L. Kinsey
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Sheet Metal ◽  
Failure Criterion ◽  
Path Dependence ◽  
Yield Criterion ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Simulation Results

Determining tearing concerns in numerical simulations of sheet metal components is difficult since the traditional failure criterion, which is strain-based, exhibits a strain path dependence. A stress-based, as opposed to a strain-based, failure criterion has been proposed and demonstrated analytically, experimentally in tube forming, and through numerical simulations. The next step in this progression to the acceptance of a stress-based forming limit diagram is to demonstrate how this failure criterion can be used to predict failure of sheet metal parts in numerical simulations. In this paper, numerical simulation results for dome height specimens are presented and compared to experimental data. This procedure was repeated for various yield criteria to examine the effect of this parameter on the ability to predict failure in the numerical simulations. Reasonable agreement was obtained comparing the failure predicted from numerical simulations and those found experimentally, in particular for the yield criterion which has been shown to best characterize the material used in this study.

Numerical Simulation Support for a Stress-Based Failure Criterion

2005 ◽  
Author(s):  
Sumit Moondra ◽  
Aaron Sakash ◽  
Brad Kinsey
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Sheet Metal ◽  
Failure Criterion ◽  
Path Dependence ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Sheet Metal Parts

Determining tearing concerns in numerical simulations of sheet metal components is difficult since the traditional failure criterion is strain-based and exhibits strain path dependence. Recently, a stress-based, as opposed to a strain-based, failure criterion has been proposed and demonstrated both analytically for sheet materials (Arrieux, 1987 and Stoughton, 2001) and experimentally for tube hydroforming (Kuwabara et al., 2003). The next steps in this progression to acceptance of a stress-based forming limit diagram is to demonstrate how this failure criterion can be used to predict failure of sheet metal parts in numerical simulations. In this paper, numerical simulation results for dome height testing specimens are presented and compared to experimental data from Graf and Hosford (1993). Reasonable agreement was obtained comparing the failure predicted from numerical simulations and those found experimentally.

Study on the Forming Process of the Crossmember in Car Intermediate Floor

2013 ◽  
Vol 442 ◽  
pp. 593-598
Author(s):  
Xue Xia Wang ◽  
Peng Chong Guan ◽  
Hai Peng Li ◽  
Li Hui Wang ◽  
Na Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Process Parameters ◽  
Thickness Distribution ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Simulation Technology ◽  
Forming Process ◽  
Distribution Diagram ◽  
Simulation Results

Flanging and bending forming processes of the crossmember in car intermediate floor are investigated respectively by using numerical simulation technology. The numerical model of the crossmember was established and its press forming effect was simulated to determine the feasible process parameters affecting its manufacturability. Forming limit diagram and thickness distribution diagram are used to evaluate simulation results of different process schemes. And then optimum values of process parameters for flanging and bending are found, which can reduce the tendencies of wrinkling, springback and crackling during the stamping of the product.

Bifurcation Analysis of Forming Limits for an Orthotropic Sheet Metal

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Shuhui Li ◽  
Ji He ◽  
Z. Cedric Xia ◽  
Danielle Zeng ◽  
Bo Hou
Keyword(s):  
Sheet Metal ◽  
Bifurcation Analysis ◽  
Yield Criterion ◽  
Forming Limit Diagram ◽  
Experimental Result ◽  
Forming Limit ◽  
Forming Limits ◽  
R Value ◽  
Value Effect ◽  
The Hill

A bifurcation analysis of forming limits for an orthotropic sheet metal is presented in this paper. The approach extends Stören and Rice's (S–R) bifurcation analysis for isotropic materials, with materials following a vertex theory of plasticity at the onset of localized necking. The sheet orthotropy is represented by the Hill’48 yield criterion with three r-values in the rolling (r0), the transverse (r90) and the diagonal direction (r45). The emphasis of the study is on the examination of r-value effect on the sheet metal forming limit, expressed as a combination of the average r-value raverage and the planar anisotropy (Δr). Forming limits under both zero extension assumption and minimum extension assumption as well as necking band orientation evolution are investigated in detail. The comparison between the experimental result and predicted forming limit diagram (FLD) is presented to validate the extended bifurcation analysis. The r-value effect is observed under uniaxial and equal-biaxial loadings. However, no difference is found under plane strain condition in strain-based FLD which is consistent with Hill's theory. The force maximum criterion is also used to analyze FLD for verification.

Numerical Simulation of Punching Bonding Based on AutoForm

2011 ◽  
Vol 189-193 ◽  
pp. 3423-3426
Author(s):  
Jiang Tao Wang ◽  
Ming Qian Shen ◽  
Tao Xue ◽  
Guo Hong Dai
Keyword(s):  
Numerical Simulation ◽  
Sheet Metal ◽  
Process Parameters ◽  
Limit Analysis ◽  
Die Design ◽  
Forming Limit ◽  
Stamping Die ◽  
Different Shapes ◽  
Simulation Results ◽  
Study Context

Punching bonding made for study context and Autoform selected for platform, numerical simulation of stamping was carried under different shapes, different materials, different parameters, and the different simulation results was gained . And deformation, the thickness of the forming limit analysis of simulation results, etc., and thus such important parameters as the thickness of sheet metal, punch diameter, the speed and the size of power punching and etc.,was modified and debuged, the combination of optimized process parameters of sheet metal was achieved in the final. Therefore, AutoForm not only can be used to overcome the difficulties,which there is no standard available, relying on repeated experiments to determine the parameters of the connected so as to achieve green design stamping; but also be made for stamping die design and production of connections to increase the efficiency and the expansion of the stamping connections the scope of the application.

Comparison of Experimental and Numerical Failure Criterion for Formability Prediction of Automotive Part

2013 ◽  
Vol 658 ◽  
pp. 354-360 ◽  
Author(s):  
Jun Seok Yoon ◽  
Hak Gon Noh ◽  
Woo Jin Song ◽  
Beom Soo Kang ◽  
Jeong Kim
Keyword(s):  
Sheet Metal ◽  
Failure Criterion ◽  
Fe Simulation ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Forming Process ◽  
Gtn Model ◽  
Numerical Result ◽  
Automotive Part ◽  
Nakajima Test

The ability to predict the forming severity with respect to crack and failure is essential to analysis of sheet metal forming process. The forming limit diagram (FLD) is commonly used to gauge the formability of sheet metal. In this article, forming limit diagrams of cold rolled carbon steel (JIS-SPCC), which widely used to produce the parts of automobile, are obtained by performing experiment and FE simulation with the Nakajima-test. By using the GTN (Gurson-Tvergaard -Needleman) damage mechanical model, a failure criterion based on void evolution was examined in this FE simulation. The parameters of GTN model are determined through comparison of experimental and numerical result with Nakajima-test. These parameters acceptably can be used in GTN model using given material. In application case, the reliability of the GTN model for failure criterion in simulation with automotive part was confirmed.

Determination of FLD for Ti-6Al-4V Titanium Alloy Sheet

2016 ◽  
Vol 687 ◽  
pp. 171-178
Author(s):  
Piotr Lacki
Keyword(s):  
Titanium Alloy ◽  
Numerical Simulations ◽  
Real Time ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Alloy Sheet ◽  
Forming Limit

Ti-6Al-4V is the most widely applied titanium alloy in technology and medicine due its good mechanical properties combined with low density and good corrosion resistance. However, poor technological and tribological properties make it very difficult to process, including the problems with sheet-metal forming. The best way to evaluate sheet drawability is to use Forming Limit Diagram (FLD), which represents a line at which failure occurs. FLD allows for determination of critical forming areas.The FLDs can be determined both theoretically and experimentally. Recently, special optical strain measurement systems have been used to determine FLDs.In this study, material deformation was measured with the Aramis system that allows for real-time observation of displacements of the stochastic points applied to the surface using a colour spray. The FLD was determined for Ti-6Al-4V titanium alloy sheet with thickness of 0.8 mm. In order to obtain a complete FLD, a set of 6 samples with different geometries underwent plastic deformation in stretch forming i.e. in the Erichsen cupping test until the appearance of fracture.The real-time results obtained from the ARAMIS software for multiple measurement positions from the test specimen surface were compared with numerical simulations of the cupping tests. The numerical simulations were performed using the PamStamp 2G v2012 software dedicated for analysis of sheet-metal forming processes. PamStamp 2G is based on the Finite Element method (FEM). The major and minor strains were analysed. The effect of friction conditions on strain distribution was also taken into consideration

Effect of Bending Strain in Forming Limit Strain and Stress of IN-718 Sheet Metal

2015 ◽  
Vol 830-831 ◽  
pp. 238-241 ◽  
Author(s):  
K.Sajun Prasad ◽  
Sushanta Kumar Panda ◽  
Sujoy Kumar Kar ◽  
S.V.S. Narayana Murty ◽  
S.C. Sharma
Keyword(s):  
Sheet Metal ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Forming Process ◽  
Hardening Law ◽  
Bending Strain ◽  
Multi Stage ◽  
Strain Paths ◽  
Von Mises

The forming limit diagram (ε-FLD) was estimated by deforming IN-718 sheet metal in different strain paths using a sub-size limiting dome height test set-up. The bending strains induced due to the use of smaller punch were estimated in all the strain paths, and the corrected ε-FLD was evaluated. The mathematical models such as Hill localized necking, Swift diffuse necking and Storen-Rice bifurcation theories were implemented to predict the limiting strains. In-order to avoid the path dependency of the ε-FLD during multi-stage forming process, stress based forming limit diagram (σ-FLD) was estimated using von-Mises and Hill-48 anisotropy plasticity theory with incorporation of Hollomon power hardening law. It was found that the bending strain influenced the limiting strains and stresses in the forming limit diagram. However, IN-718 material has encouraging formability in stretch forming process. The plot of the equivalent strains versus triaxiality indicated increasing limiting strain of the material in tension-tension mode.

The Effect of Model Parameters on Predicted Stress Based Failure Criterion for Sheet Metal

2008 ◽  
Author(s):  
Matthew J. Derov ◽  
Brad L. Kinsey ◽  
Igor Tsukrov
Keyword(s):  
Sheet Metal ◽  
Failure Criterion ◽  
Strain Path ◽  
Path Dependence ◽  
Prediction Method ◽  
Forming Limit ◽  
Model Parameters ◽  
Analytical Prediction ◽  
Limit Curve ◽  
Forming Limit Curve

Tearing failure in sheet metal forming has traditionally been predicted based on the strain state of the material. However, a concern with this failure prediction method is that the strain based forming limit curve exhibits significant strain path dependence. A stress based failure criterion has been proposed and shown to be less sensitive to the strain path through numerical simulations and by analytically converting strain based data to stress space. However, a means to predict this stress based failure criterion without prior knowledge of the strain based forming limit curve for sheet metal is required. In this paper, an analytical prediction of the stress based forming limit curve is derived and compared to experimental and numerical results. The effects of model parameters are also investigated.

Optimization of Sheet Metal Process Parameters of a Shield Case Piece Using Computer Simulation

2006 ◽  
Vol 510-511 ◽  
pp. 330-333
Author(s):  
M.C. Curiel ◽  
Ho Sung Aum ◽  
Joaquín Lira-Olivares
Keyword(s):  
Sheet Metal ◽  
Thickness Distribution ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Physical Processes ◽  
Forming Process ◽  
Element Analysis ◽  
One Step ◽  
Range Of Values ◽  
Principal Strains

Numerical simulations based on Finite Element Analysis (FEA) are widely used to predict and evaluate the forming parameters before performing the physical processes. In the sheet metal industry, there are basically two types of FE programs: the inverse (one-step) programs and the incremental programs. In the present paper, the forming process of the shield case piece (LTA260W1-L05) was optimized by performing simulations with both types of software. The main analyzed parameter was the blankholding force while the rest of the parameters were kept constant. The criteria used to determine the optimum value was based on the Forming Limit Diagram (FLD), fracture and wrinkling of the material, thickness distribution, and the principal strains obtained. It was found that the holding force during the forming process deeply affects the results, and a range of values was established in which the process is assumed to give a good quality piece.

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