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.

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.

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.

Methods of Establishing Forming Limit Diagram of Tube Hydroforming

2012 ◽  
Vol 602-604 ◽  
pp. 1934-1937
Author(s):  
Guo Lin Hu ◽  
Lian Fa Yang ◽  
Jian Wei Liu
Keyword(s):  
Sheet Metal ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
The State ◽  
Forming Limit ◽  
Stress Diagram ◽  
Limit Stress ◽  
Tube Hydro Forming ◽  
Trend Of Development

Forming severity is one of the significant indexes to assess formability of tube hydroforming. The state of strain can be accurately reflected when tube reaches forming limit, mechanical rules during forming processes can be revealed as well by using the forming limit diagram (FLD). By contrast with FLD of sheet metal, the FLD of tube hydroforming is seen as different. In this paper, the importance of FLD of tube hydroforming was discussed briefly; typical methods established to FLD of tube hydroforming were listed and classified; characteristics and insufficiencies of those methods were pointed out; advantages of forming limit stress diagram (FLSD) were introduced simply. Furthermore, the main problem and the trend of development in FLD of tube hydro-forming were summarized.

Optimization of Tube Hydroforming Process Using Probabilistic Constraints on Failure Modes

2011 ◽  
Vol 62 ◽  
pp. 21-35 ◽  
Author(s):  
Anis Ben Abdessalem ◽  
A. El Hami
Keyword(s):  
Failure Modes ◽  
High Reliability ◽  
Thickness Distribution ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Plastic Instability ◽  
Probabilistic Constraints ◽  
Forming Limit ◽  
Reliability Based Design ◽  
Hydroforming Process

In metal forming processes, different parameters (Material constants, geometric dimensions, loads …) exhibits unavoidable scatter that lead the process unreliable and unstable. In this paper, we interest particularly in tube hydroforming process (THP). This process consists to apply an inner pressure combined to an axial displacement to manufacture the part. During the manufacturing phase, inappropriate choice of the loading paths can lead to failure. Deterministic approaches are unable to optimize the process with taking into account to the uncertainty. In this work, we introduce the Reliability-Based Design Optimization (RBDO) to optimize the process under probabilistic considerations to ensure a high reliability level and stability during the manufacturing phase and avoid the occurrence of such plastic instability. Taking account of the uncertainty offer to the process a high stability associated with a low probability of failure. The definition of the objective function and the probabilistic constraints takes advantages from the Forming Limit Diagram (FLD) and the Forming Limit Stress Diagram (FLSD) used as a failure criterion to detect the occurrence of wrinkling, severe thinning, and necking. A THP is then introduced as an example to illustrate the proposed approach. The results show the robustness and efficiency of RBDO to improve thickness distribution and minimize the risk of potential failure modes.

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.

Sign in / Sign up

Export Citation Format

Share Document