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.

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.

Prediction of T-Shaped Tube Hydroforming Stress Limit

2011 ◽  
Vol 480-481 ◽  
pp. 1140-1143
Author(s):  
Lin Zhou ◽  
Xiao Min Cheng
Keyword(s):  
Numerical Simulation ◽  
Tube Hydroforming ◽  
Simulation Method ◽  
Forming Limit ◽  
Stress Limit ◽  
Shaped Tube ◽  
Strain Limit ◽  
Stress Diagram ◽  
Strain Paths ◽  
Limit Stress

Tube hydroforming has been widely used in auto industry due to its remarkable advantages compared with conventional manufacturing via stamping and welding. The forming limit stress diagram (FLSD) which is independent of strain paths is of great significance to tube hydroforming. The FLSD of 2008T4 tube blank was established to predict fracture defect in T-shaped tube hydroforming simulation. By numerical simulation method, the stress limit and strain limit were analyzed and fracture defects were predicted. Two prediction results of the fracture defects location were the same yet the limit pressure values corresponding to fracture were different. The FLSD prediction result was close to the experiment result, so the accuracy of FLSD as tube hydroforming limit criterion was proved.

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.

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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