scholarly journals Development of Electrohydraulic Forming Process for Aluminum Sheet with Sharp Edge

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ji-Yeon Shim ◽  
Bong-Yong Kang
Keyword(s):  
High Velocity ◽  
Forming Limit Diagram ◽  
Sharp Edge ◽  
Dome Height ◽  
Forming Limit ◽  
Radius Of Curvature ◽  
Forming Process ◽  
Electrohydraulic Forming ◽  
Forming Technology ◽  
Sharp Edges

Electrohydraulic forming (EHF), high-velocity forming technology, can improve the formability of a workpiece. Accordingly, this process can help engineers create products with sharper edges, allowing a product’s radius of curvature to be less than 2 mm radius of curvature. As a forming process with a high-strain rate, the EHF process produces a shockwave and pressure during the discharge of an electrical spark between electrodes, leading to high-velocity impact between the workpiece and die. Therefore, the objective of this research is to develop an EHF process for forming a lightweight materials case with sharp edges. In order to do so, we employed A5052-H32, which has been widely used in the electric appliance industry. After drawing an A5052-H32 Forming Limit Diagram (FLD) via a standard limiting dome height (LDH) test, improvements to the formability via the EHF process were evaluated by comparing the strain between the LDH test and the EHF process. From results of the combined formability, it is confirmed that the formability was improved nearly twofold, and a sharp edge with less than 2 mm radius of curvature was created using the EHF process.

scholarly journals Acquisition and Evaluation of Theoretical Forming Limit Diagram of Al 6061-T6 in Electrohydraulic Forming Process

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 401 ◽  
Author(s):  
Min-A Woo ◽  
Woo-Jin Song ◽  
Beom-Soo Kang ◽  
Jeong Kim
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Forming Process ◽  
Electrohydraulic Forming ◽  
Al 6061 ◽  
Shpb Test ◽  
Strain Rate Hardening ◽  
Free Bulging

The current study examines the forming limit diagram (FLD) of Al 6061-T6 during the electrohydraulic forming process based on the Marciniak–Kuczynski theory (M-K theory). To describe the work-hardening properties of the material, Hollomon’s equation—that includes strain and strain rate hardening parameters—was used. A quasi-static tensile test was performed to obtain the strain-hardening factor and the split-Hopkinson pressure bar (SHPB) test was carried out to acquire the strain rate hardening parameter. To evaluate the reliability of the stress–strain curves obtained from the SHPB test, a numerical model was performed using the LS–DYNA program. Hosford’s yield function was also employed to predict the theoretical FLD. The obtained FLD showed that the material could have improved formability at a high strain rate index condition compared with the quasi-static condition, which means that the high-speed forming process can enhance the formability of sheet metals. Finally, the FLD was compared with the experimental results from electrohydraulic forming (EHF) free-bulging test, which showed that the theoretical FLD was in good agreement with the actual forming limit in the EHF process.

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.

A Study of Improving the Formability of the Commercial Pure Titanium Foils

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Jiaqi Zhu ◽  
Alex Nunnally ◽  
Jenn-Terng Gau ◽  
Siguang Xu
Keyword(s):  
High Velocity ◽  
Pure Titanium ◽  
Tensile Tests ◽  
Dome Height ◽  
Forming Limit ◽  
High Velocity Impact ◽  
Uniform Thickness ◽  
Forming Process ◽  
Velocity Impact ◽  
Commercial Pure Titanium

Abstract In order to obtain the optimum forming process for commercial pure titanium grade 2 foils, a series of tensile tests and micro scale limited dome height (µ-LDH) tests at four temperatures, and meso scale limited dome height tests (meso-LDH) with three punch speeds were conducted on the as-received foils with a thickness of 75 µm. The effects of temperature, geometry, and high-velocity impact were investigated to understand their influences on the formability of the foils. It has been found in the tensile tests that the formability can be improved by elevating temperatures; this has been validated by the µ-LDH tests. Based on forming limit diagrams (FLDs) of the meso-LDH specimens, the high-velocity impact forming process results in not only much better formability but also more uniform thickness distributions than the quasi-static. By analyzing the fractographical scanning electron microscope (SEM) pictures of the meso-LDH specimens, it has been proven that the formability of the foils by using high-velocity impact process is superior to the conventional process. Furthermore, high-velocity impact causes forming limit curve (FLC) to shift in the upper right direction on the right-hand side of FLD. Therefore, it is suggested forming the foils by using high-velocity impact forming process at the elevated temperature for obtaining a better formability and more uniform thickness distribution. It is also recommended to make the radius of the LDH hemisphere punch close to the smallest feature of the designed products for obtaining more accurate FLCs.

Formability Assessment of Prestrained Automotive Grade Steel Sheets Using Stress Based and Polar Effective Plastic Strain-Forming Limit Diagram

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
S. Basak ◽  
S. K. Panda ◽  
Y. N. Zhou
Keyword(s):  
Plastic Strain ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Interstitial Free ◽  
Effective Plastic Strain ◽  
Stretch Forming ◽  
Forming Process ◽  
Two Stage ◽  
Second Stage

Accurate prediction of the formability in multistage forming process is very challenging due to the dynamic shift of limiting strain during the different stages depending on the tooling geometry and selection of the process parameters. Hence, in the present work, a mathematical framework is proposed for the estimation of stress based and polar effective plastic strain-forming limit diagram (σ- and PEPS-FLD) using the Barlat-89 anisotropic plasticity theory in conjunction with three different hardening laws such as Hollomon, Swift, and modified Voce equation. Two-stage stretch forming setup had been designed and fabricated to first prestrain in an in-plane stretch forming setup, and, subsequently, limiting dome height (LDH) testing was carried out on the prestrained blanks in the second stage to evaluate the formability. The finite element (FE) analysis of these two-stage forming process was carried out in ls-dyna for automotive grade dual-phase (DP) and interstitial-free (IF) steels, and the σ-FLD and PEPS-FLD were used as damage model to predict failure. The predicted forming behaviors, such as LDH, thinning development, and the load progression, were validated with the experimental results. It was found that the LDH in the second stage decreased with increase in the prestrain amount, and both the σ-FLD and PEPS-FLD could be able to predict the formability considering the deformation histories in the present multistage forming process with complex strain path.

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.

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.

Comparison of different welding methods on mechanical properties and formability behaviors of tailor welded blanks (TWB) made from AA6061 alloys

2020 ◽  
pp. 095440622095250
Author(s):  
Behrouz Bagheri ◽  
Mahmoud Abbasi ◽  
Reza Hamzeloo
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Co2 Laser ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Welding Parameters ◽  
Friction Stir ◽  
Tailor Welded Blanks ◽  
Different Characteristics

A tailor welded blank (TWB) includes two or more blanks joined together in order to make a single blank. Different welding methods are used to join blanks with different characteristics and form TWBs. In this study, a comparison is made among the effects of three different welding methods namely CO2 laser welding, friction stir welding (FSW), and friction stir vibration welding (FSVW) on mechanical and formability properties of developed TWBs. AA6061 alloy sheets with different thicknesses (1.2 and 0.8 mm) are joined to get TWBs. The forming limit diagram (FLD) and limiting dome height (LDH) are applied to assess the formability. The Taguchi method is applied to find the optimum values of welding parameters. It is concluded that TWBs made by FSVW have higher mechanical properties and formability compared to TWBs made by FSW and CO2 laser welding. The results also indicate that FLD for TWBs made by FSW is higher than FLD for TWBs made by CO2 laser welding and FLD0, for TWBs made by FSVW, increases as vibration frequency increases.

Incremental Sheet Forming with an Industrial Robot – Forming Limits and Their Effect on Component Design

2005 ◽  
Vol 6-8 ◽  
pp. 457-464 ◽  
Author(s):  
L. Lamminen
Keyword(s):  
Sheet Metal ◽  
Industrial Robot ◽  
Forming Limit Diagram ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Point Of View ◽  
Forming Limit ◽  
Forming Process ◽  
3D Cad ◽  
Component Design

Incremental sheet forming (ISF) has been a subject of research for many research groups before. However, all of the published results so far have been related to either commercial ISF machines or ISF forming with NC mills or similar. The research reported in this paper concentrates on incremental sheet forming with an industrial robot. The test equipment is based on a strong arm robot and a moving forming table, where a sheet metal blank is attached. The tool slides on the surface of the sheet and forms it incrementally to the desired shape. The robot is capable of 5-axis forming, which enables forming of inwards curved forms. In this paper the forming limit diagram (FLD) for ISF with the robot is presented and it is compared with conventional forming limit diagrams. It will be shown that the conventional FLD does not apply to incremental forming process. Geometrical accuracy of sample pieces is also studied. Cones of different shapes are formed with the robot equipment and their correspondence with the 3D CAD model is evaluated. The results are compared with other results of accuracy of incremental sheet forming, reported earlier by other researchers. The third issue covered in this article is a product development point of view to incremental sheet forming. In addition to fast prototyping and low volume production of sheet metal parts, ISF brings new possibilities to sheet metal component design and manufacturing. These possibilities can only be exploited if design rules, that will take the possibilities and limitations of the method into account are created for ISF.

Establishment and Application of Forming Limit Diagram of Multi-Gauge Laser Tailor-Welded Blanks

2010 ◽  
Vol 97-101 ◽  
pp. 420-425
Author(s):  
Wei Chen ◽  
S. Cheng ◽  
Y. Ding ◽  
Y.Q. Guo ◽  
L. Xue
Keyword(s):  
High Strength Steel ◽  
Research Method ◽  
Forming Limit Diagram ◽  
High Strength ◽  
Failure Criteria ◽  
Limit Strain ◽  
Measuring System ◽  
Forming Limit ◽  
Forming Process ◽  
Tailor Welded Blanks

The method for establishing the forming limit diagram (FLD) of multi-gauge high strength steel laser tailor-welded blanks (LTWB) is introduced based on analyzing the failure mechanism of multi-gauge LTWB. The Nakazima test is performed to generate the limit strain of multi-gauge high strength steel LTWB. By means of the ARGUS strain measuring system, the limit strain is measured and the FLD of LTWB is plotted subsequently. The FLD established by the Nakazima test is introduced into the FEA forming process as the failure criteria. Compared with the predicted result of the FLD of thinner metal, better correlation between the simulation and experimental results is indicated by adopting the FLD of LTWB as the necking criteria, which also reveals the validity and practicability of the FLD research method for multi-gauge high strength steel LTWB.

Reliability Analysis of the Tube Hydroforming Process Based on Forming Limit Diagram

2005 ◽  
Vol 128 (3) ◽  
pp. 402-407 ◽  
Author(s):  
Bing Li ◽  
Don R. Metzger ◽  
Tim J. Nye
Keyword(s):  
Automotive Industry ◽  
Metal Forming ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Probability Of Failure ◽  
Alternative Methods ◽  
Forming Limit ◽  
Forming Process ◽  
Hydroforming Process ◽  
Free Bulging

Tube hydroforming is an attractive manufacturing process in the automotive industry because it has several advantages over alternative methods. In order to determine the reliability of the process, a new method to assess the probability of failure is proposed in this paper. The method is based on the reliability theory and the forming limit diagram, which has been extensively used in metal forming as the criteria of formability. From the forming limit band in the forming limit diagram, the reliability of the forming process can be evaluated. A tube hydroforming process of free bulging is then introduced as an example to illustrate the approach. The results show this technique to be an innovative approach to avoid failure during tube hydroforming.

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