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.

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.

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.

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.

Finite-Element Modeling of Thermal Forming of Ti-TWBs with Experimental Verification

2014 ◽  
Vol 626 ◽  
pp. 518-523
Author(s):  
C.P. Lai ◽  
Luen Chow Chan
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
Experimental Verification ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Production Test ◽  
Forming Process ◽  
Tailor Welded Blanks ◽  
Multi Stage ◽  
Strain Paths

The titanium tailor-welded blanks (Ti-TWBs) are being developed in different industries such as automobile and aerospace, combining the advantages of both tailor-welded blanks technology and titanium alloys. In recent decades, computer simulation of sheet metal forming processes has been employed increasingly over conventional production test and adjustment methodology to achieve the optimum and cost-effective operation procedures. Recently, certain amounts of theoretical analysis for the sheet metal forming process have been developed. However, these analyses could not be applied directly to the material under multi-stage forming process. Thus, some researchers have developed a damage-based model to predict the instability and failure of sheet metals, particularly for the above Ti-TWBs, with consideration of material damage under discontinuous or proportional loading strain paths. So far this model has been used and proved to be successful to predict formability of selected sheets of steel and aluminium alloy. However, the application of the damage-coupled model has yet to be extended to the Ti-TWBs under thermal multi-stage forming operation.The main objective of this paper is to investigate numerically the formability of Ti-TWBs under multi-stage forming process with experimental verification. Titanium alloy sheets (Ti-6Al-4V) in thickness of 0.7mm and 1.0mm were selected and laser-welded the specimen of Ti-TWBs. The model based on the damage mechanics is introduced to predict the thermal formability of Ti-TWBs with change of strain paths. In this study, the anisotropic damage model incorporate with the finite element codes and user-define material subroutine were developed to predict the formability of Ti-TWBs with change of strain paths. The mechanical properties and damage parameters of Ti-TWBs for the simulation were measured experimentally. The simulation of Ti-TWB under multi-stage forming process were then conducted and validated experimentally at similar forming conditions. The predicted results have been found to agree well with those obtained from the experiments. This analysis can be applied readily to design and manufacture TWB components or structures so as to satisfy the need of such market demands.

Forming Limit Prediction of BCC Materials under Non-Proportional Strain-Path by Using Crystal Plasticity

2012 ◽  
Vol 201-202 ◽  
pp. 1110-1116
Author(s):  
Mei Yang ◽  
Xiao Yan Zhang ◽  
Hao Wang
Keyword(s):  
Sheet Metal ◽  
Crystal Plasticity ◽  
Strain Path ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Slip Systems ◽  
Plasticity Model ◽  
Forming Process ◽  
Crystal Plasticity Model ◽  
Microstructure Effect

In this paper, the forming limit of a body-centered cubic (BCC) sheet metal under non-proportional strain-path is investigated by using the Marciniak and Kuczynski approach integrated with a rate-dependent crystal plasticity model. The prediction model has been proved to be effective in predicting Forming Limit Diagram (FLD) of anisotropic sheet metal with FCC type of slip systems[1]. The same model has been used to study the FLD under non-proportional strain-path of BCC slip systems numerically and experimentally. The agreement between the experiments and simulations is good. With crystal plasticity model well describing the crystal microstructure effect, our model can be used to predict the FLD of BCC sheet metal under complicated strain path in plastic forming process with good accuracy.

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.

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.

Research on the Forming Limit Diagram Based on Laser Shock Forming

2010 ◽  
Vol 44-47 ◽  
pp. 148-152
Author(s):  
Yin Fang Jiang ◽  
Zhen Zhou Tang ◽  
Zhi Fei Li ◽  
Lei Fang
Keyword(s):  
Sheet Metal ◽  
Strain Path ◽  
Reduction Rate ◽  
Forming Limit Diagram ◽  
Thickness Reduction ◽  
Forming Limit ◽  
Laser Shock ◽  
Maximum Thickness ◽  
Laser Shock Forming ◽  
Strain Paths

Laser shock forming (LSF) of sheet metal is a novel technology in plastic deformation. It is necessary to correctly predict the Forming Limit Diagram (FLD) based on LSF. New failure maximum thickness reduction rate criterion is used to determine the forming limit based on the numerical system during LSF. The relationship model between maximum thickness reduction rate and the strain path is built. In addition, the effects of strain path and strain-hardening exponent on forming limit are considered. The maximum thickness reduction rate under equi-biaxial tensile strain path can be determined easily during LSF and the expression of the criterion is determined finally. Then the limit strains under other strain paths between uniaxial tension to equi-biaxial tension can be determined by the criterion combined with numerical simulation of forming process. The criterion can predict forming limits for sheet metal exactly and makes it possible to determine forming limit strains under different strain paths only through equi-biaxial tensile test during LSF.

scholarly journals Effect of crystallographic texture on the forming limit in microforming of brass

2019 ◽  
Vol 6 ◽  
pp. 27
Author(s):  
Anil Mashalkar ◽  
Vilas Nandedkar
Keyword(s):  
Crystal Orientation ◽  
Plastic Anisotropy ◽  
Experimental Tests ◽  
Plane Stress State ◽  
Internal Variable ◽  
Yield Function ◽  
Dome Height ◽  
Forming Limit ◽  
Forming Process ◽  
Strain Paths

Microforming is an emerging technology to manufacture products in the light of miniaturization in several domains of industry. Plastic anisotropy is one of the material characteristics significantly affecting the micro forming process. The crystal orientation influences tensile strength, yield strength and ductility, depending on different grain sizes and principle sliding planes. The present work elaborates on the influence of the plastic anisotropic in microforming for a plane stress state condition. Yield function and constitutive equations for the anisotropic material with consideration of the crystal lattice constants and parameters of crystallography texture are proposed. The crystal orientation is considered in a subroutine VUMAT algorithm, as an internal variable based on the developed mathematical model which is implemented in Abaqus as an user material subroutine. Micro limiting dome height experimental tests for different strain paths are conducted with brass foils. The results are compared with that predicted with numerical analysis, considering critical damage and element deletions. The numerical and experimental results show a good agreement for the Alpha brass ultra-thin foils, using a set of failure criterion.

Computer-assisted engineering determination of the formability limit for thin sheet metals by a modified Marciniak method

2009 ◽  
Vol 44 (6) ◽  
pp. 459-472 ◽  
Author(s):  
T Pepelnjak ◽  
B Barisic
Keyword(s):  
Shape Change ◽  
Thin Sheet ◽  
Central Area ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Computer Assisted ◽  
Stress Concentrations ◽  
Forming Process ◽  
Forming Limits ◽  
Strain Paths

Development of a new sheet-metal-forming technology in a digital environment demands accurate and reliable mechanical properties and forming limits of the selected material. It is essential to determine the forming limits for thin sheets and foils. Implementation of the Marciniak procedure with strip-shaped specimens defining the left-hand side of the forming limit diagram (FLD) results in tearing outside the observed area of the specimen. Therefore, new shapes of test pieces were designed with a strip-shaped central area and enlarged outer areas, which were in contact with the die during the forming process. The radius of the specimen enlargement enabled a co-axial contact of its edge and direction of the material flow over the die radius during the forming process. The shape of the redesigned geometry of the specimen was analysed using the finite element (FE) program ABAQUS to minimize undesired stress concentrations at the die radius. Finally, strain paths variations due to shape change were analysed. The new specimen concept was verified on TS-275 tinplate steel with a thickness of 0.24 mm. By implementing the necessary redesigned specimen shapes and by analysis of the tearing limit of the TS-275 material, the forming limit curve for the tinplate material under investigation was constructed.

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