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Research Papers

Forming Limit Differences in Hemispherical Dome and Biaxial Test During Equibiaxial Tension on Cruciform

[+] Author and Article Information
Chetan P. Nikhare

Department of Mechanical Engineering,
The Pennsylvania State University Erie,
Erie, PA 16563
e-mail: cpn10@psu.edu

Emmett Vorisek

Department of Mechanical Engineering,
The Pennsylvania State University Erie,
Erie, PA 16563
e-mail: ejv5072@psu.edu

John R. Nolan

Department of Mechanical Engineering,
The Pennsylvania State University Erie,
Erie, PA 16563
e-mail: jrn5231@psu.edu

John T. Roth

Department of Mechanical Engineering,
The Pennsylvania State University Erie,
Erie, PA 16563
e-mail: jtr11@psu.edu

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received December 11, 2016; final manuscript received May 7, 2017; published online July 6, 2017. Assoc. Editor: Ashraf Bastawros.

J. Eng. Mater. Technol 139(4), 041011 (Jul 06, 2017) (9 pages) Paper No: MATS-16-1365; doi: 10.1115/1.4037020 History: Received December 11, 2016; Revised May 07, 2017

Traditionally, the mechanical properties of materials have been characterized using the uniaxial tension test. This test is considered adequate for simple forming operations where single axis loading is dominant. Previous studies, however, have noted that the data acquired from this type of testing are not enough and additional details in other axes under simultaneous deformation conditions are important. To analyze the biaxial strain, some studies have suggested using the limiting dome height test and bulge test. However, these tests limit the extent of using multi-axial loading and the resulting stress pattern due to contact surfaces. Therefore, researchers devised the biaxial machine which is designed specifically to provide biaxial stress components using multiple and varying loading conditions. The idea of this work is to evaluate the relationship between the dome test data and the biaxial test data. For this comparison, cruciform specimens with a diamond shaped thinner gage in the center were deformed with biaxial stretching on the biaxial testing machine. In addition, the cruciform specimens were biaxially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a three-dimensional (3D) model generated on abaqus. These models were then compared with the experimental results. The forces on each arm, strain path, forming, and formability were analyzed. The differences between the processes were detailed. It was found that biaxial tests eliminated the pressurization effect which could be found in hemispherical dome tests.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Tensile sample dimension and MTS tensile test machine [29]

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Fig. 2

Cruciform specimen with diamond center

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Fig. 3

Biaxial experiment setup with DIC

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Fig. 4

Nakajima hemispherical dome test setup

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Fig. 5

Biaxial model: (a) 3D model and (b) meshed samples

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Fig. 6

Hemispherical dome test model

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Fig. 7

Engineering stress–strain curve for three samples in rolling direction

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Fig. 8

True stress–strain curve along with fitted power law

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Fig. 9

Strain pattern through DIC on deformed biaxial specimen: (a) intermediate strain pattern representation with picked elements for analysis, (b) specimen at the start of deformation, and (c) specimen near to failure

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Fig. 10

Equivalent plastic strain pattern on simulated biaxial specimen: (a) near to failure and (b) separation

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Fig. 11

Engineering stress–strain curve for selected arm regions of cruciform

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Fig. 12

Arm stress–strain curve in biaxial experiment and simulation

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Fig. 13

Deformed specimen during hemispherical dome tests: (a) experiment, (b) simulated equivalent plastic strain patter near to failure, and (c) simulated separation

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Fig. 14

Punch force–displacement comparison during experiment and simulation of hemispherical dome test

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Fig. 15

Engineering stress–strain curve for arm location during biaxial and hemispherical dome simulation

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Fig. 16

Engineering stress–strain curve for center location during biaxial and hemispherical dome simulation

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Fig. 17

Biaxial strain path during biaxial and hemispherical dome simulation along with as received material forming limit diagram

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Fig. 18

Stress–strain response under hydrostatic pressure (Reprinted with permission from Wu et al. [12]. Copyright 2009 by Elsevier.)

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Fig. 19

Effective stress–strain response under hydrostatic pressure (Reprinted with permission from Wu et al. [12]. Copyright 2009 by Elsevier.)

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Fig. 20

Forming limit diagram under hydrostatic pressure (Reprinted with permission from Wu et al. [12]. Copyright 2009 by Elsevier.)

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Fig. 21

Biaxial strain path during biaxial and hemispherical dome simulation along with hypothetic annealed FLC and pressurized FLC

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