Accurate determination of flow curves using the bulge test with optical measuring systems

Mulder, J.; Vegter, H.; Aretz, Holger; Keller, Stefan; Boogaard, A.H. van den

doi:10.1016/j.jmatprotec.2015.06.034

Cited by 59 publications

(20 citation statements)

References 20 publications

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“…The bulge test is a method that can be used to measure biaxial stress-strain curves [46], parts of yield surfaces [47][48][49][50] and forming limit curves (FLC) [51], or characterize damage mechanisms [52] of sheet metal (as well as the mechanical response of thin films [53,54] or biological tissues [55,56]). Circular dies are typically used to investigate equi-biaxial strain paths, however elliptical dies can be employed to observe proportional strain paths with a strain ratio different from 1 [57][58][59][60][61][62].…”

Section: Methodology Developmentmentioning

confidence: 99%

Tracking Microstructure Evolution in Complex Biaxial Strain Paths: A Bulge Test Methodology for the Scanning Electron Microscope

Plancher

Vonk

et al. 2019

Exp Mech

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In this work, a novel method is presented to track site-specific microstructure evolution in metallic materials deformed biaxially along proportional and complex strain paths. A miniaturized bulge test setup featuring a removable sample holder was designed to enable incremental measurements to be performed in a scanning electron microscope, by probing the same position on the sample at different deformation levels, with electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI) and other imaging modes.Validation experiments were performed at room temperature on samples prepared from commercial sheet metal (dual-phase steel) and foils (stainless steel). Local strain measurements with the digital image correlation technique confirmed that proportional strain paths with a strain ratio up to 5 can be investigated using elliptical dies in the bulge test holder. It is also shown how complex strain paths can be obtained using a combination of overlapping elliptical dies. Incremental EBSD and ECCI were conducted in configurations relevant for the multi-scale investigation of localized plasticity and damage mechanisms in dual-phase steel. Quantitative information regarding microstructure evolution (phase fractions, orientation fields, dislocation structures, etc.) and regarding local strain distributions could be successfully obtained. This type of data sheds light on underlying deformation mechanisms and provides opportunities to calibrate crystal plasticity models.

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Section: Methodology Developmentmentioning

confidence: 99%

Tracking Microstructure Evolution in Complex Biaxial Strain Paths: A Bulge Test Methodology for the Scanning Electron Microscope

Plancher

Vonk

et al. 2019

Exp Mech

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“…The accuracy was improved by incorporating a correction factor related to the dome apex thickness to account for the non-uniformity of the strain distribution on the pole. It was observed that the accuracy of this could be improved further [7]. A systematic study showed that evolution of the sheet thickness is dependent of the anisotropy [21,40].…”

Section: Introductionmentioning

confidence: 99%

“…The uniaxial tensile test is the most commonly used such test. It provides stress-strain data up to the point of diffuse necking at very low levels of plastic strain, when compared with the ones attained in some forming processes [3,7,8]. However, in sheet forming processes, the level of plastic deformation can be higher.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the yield loci of four sheet materials (AA6111-T4, AC600, DX54D+Z, and H220BD+Z) by using uniaxial tensile and hydraulic bulge tests

Alharthi

Hazra

Alghamdi

et al. 2018

Int J Adv Manuf Technol

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“…Other than for sheet metals, pure bending devices have been developed and used for various materials, such as for composite materials by Ben Zineb et al [2], weldments by Bu & Gardner [11], flexible electronics by Hoefnagels et al [12], micro electro-mechanical systems (MEMS) by Elhebeary & Saif [13], micro thin sheet by Stölken & Evans [14] and metal tubes by Guo et al [15]. Alternative testing methods such as shear tests [16][17][18] and bulge tests [19][20][21] can also be used to obtain stress-strain data at high strains. These tests are in general complex in design.…”

Section: Introductionmentioning

confidence: 99%

A New in-Plane Bending Test to Determine Flow Curves for Materials with Low Uniform Elongation

et al. 2020

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Background Flow curves can easily be obtained by uniaxial tensile tests, but strains are then limited by diffuse necking. For many applications, the flow stress must be known above this limit. Objective The main objective of this paper is to obtain flow curves for material with low uniform elongation to relatively high strains compared to a uniaxial tensile test. Method A novel in-plane sheet bending experiment and stress evaluation procedure is presented. The developed bending device can be mounted in a tensile test machine and can produce very high bending curvatures compared to previously proposed pure bending setups. The bending angle and curvature are obtained by image processing and the bending moment is calculated directly from the force measured from the tensile test machine and the bending angle. The moment–curvature relation is used to determine the uniaxial stress–strain relation using an analytical approach, without presuming any hardening model. The bending process and the analytical procedure are validated by a numerical simulation as well as by experiments. Results The numerical validation shows good agreement between the stress–strain curve obtained from the bending process and that of the uniaxial input flow curve up to 12% strain. Experimentally the model is validated by comparing the stress–strain curve obtained from the bending test with the results directly obtained from a tensile test for mild steel. Good agreement is observed up to 12% strain. As an application example, bending tests were performed on a martensitic steel (MS) with low uniform strain (less than 3%). For this material, flow curves could be obtained up to relatively high strains (~12%), compared to a tensile test. Conclusion This bending test setup allows to study materials with low uniform elongation up to significantly higher strains than are readily obtained in a tensile test.

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Accurate determination of flow curves using the bulge test with optical measuring systems

Cited by 59 publications

References 20 publications

Tracking Microstructure Evolution in Complex Biaxial Strain Paths: A Bulge Test Methodology for the Scanning Electron Microscope

Tracking Microstructure Evolution in Complex Biaxial Strain Paths: A Bulge Test Methodology for the Scanning Electron Microscope

Determination of the yield loci of four sheet materials (AA6111-T4, AC600, DX54D+Z, and H220BD+Z) by using uniaxial tensile and hydraulic bulge tests

A New in-Plane Bending Test to Determine Flow Curves for Materials with Low Uniform Elongation

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