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Research Papers

A Comparison Between the Accuracy of Two-Dimensional and Three-Dimensional Strain Measurements

[+] Author and Article Information
Niranjan Desai

Department of Mechanical and Civil Engineering,
Purdue University Northwest,
1401 US-421,
Westville, IN 46391

Joel Poling

Department of Mechanical and Civil Engineering,
Purdue University Northwest,
1401 US-421,
Westville, IN 46391

Gregor Fischer

Department of Civil Engineering,
Technical University of Denmark,
Brovej 118,
Kgs. Lyngby 2800, Denmark

Christos Georgakis

Department of Engineering—Structural
Monitoring and Dynamics,
Aarhus University,
Inge Lehmanns Gade 10,
Aarhus C,
Aarhus 8000, Denmark

Manuscript received July 15, 2017; final manuscript received December 8, 2017; published online January 16, 2018. Assoc. Editor: Shiv Joshi.

ASME J Nondestructive Evaluation 1(2), 021005 (Jan 16, 2018) (14 pages) Paper No: NDE-17-1069; doi: 10.1115/1.4038731 History: Received July 15, 2017; Revised December 08, 2017

This investigation determined the effect of specimen out-of-plane movement on the accuracy of strain measurement made applying two-dimensional (2D) and three-dimensional (3D) measurement approaches using the representative, state-of-the-art digital image correlation (DIC)-based tool ARAMIS. DIC techniques can be used in structural health monitoring (SHM) by measuring structural strains and correlating them to structural damage. This study was motivated by initially undetected damage at low strains in connections of a real-world bridge, whose detection would have prevented its propagation, resulting in lower repair costs. This study builds upon an initial investigation that concluded that out-of-plane specimen movement results in noise in DIC-based strain measurements. The effect of specimen out-of-plane displacement on the accuracy of strain measurements using the 2D and 3D measurement techniques was determined over a range of strain values and specimen out-of-plane displacements. Based upon the results of this study, the 2D system could measure strains as camera focus was being lost, and the effect of the loss of focus became apparent at 1.0 mm beam out-of-plane displacement while measuring strain of the order of magnitude of approximately 0.12%. The corresponding results for the 3D system demonstrate that the beam out-of-plane displacement begins to affect the accuracy of the strain measurements at approximately 0.025% strain for all magnitudes of out-of-plane displacement, and the 3D ARAMIS system can make accurate strain measurements at up to 2.5 mm amplitude at this strain. Finally, based upon the magnitudes of strain and out-of-plane displacement amplitudes that typically occur in real steel bridges, it is advisable to use the 3D system for SHM of stiff structures instead of the 2D system.

Copyright © 2018 by ASME
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References

Desai, N. , 2016, “ Small-Strain Measurement in Bridges Using the Digital Image Correlation (DIC) Technique,” Proc. SPIE, 9805, p. 980530.
Desai, N. , Georgakis, C. , and Fischer, G. , 2016, “ A Comparison Between the Minimum Resolutions of Two Digital Image Correlation-Based Tools in Making Strain Measurements,” Fifth IAJC-ISAM International Conference, Orlando, FL, Nov. 6–8, Paper No. 093. http://cd16.iajc.org/wp-content/uploads/Camera-ready-papers/093-x-16___A%20Comparison%20Between%20the%20Minimum%20Resolutions%20of%20Two%20Digital%20Image%20_REVISED--Desai%2C%20Georgakis%2C%20Fischer_.pdf
Desai, N. , Georgakis, C. , and Fischer, G. , 2016, “ A Comparison Between the Minimum Resolutions of Two Digital Image Correlation-Based Tools in Making Strain Measurements,” Int. J. Eng. Res. Innovation, 8(2), pp. 113–126.
Jiang, R. , Jauregui, D. V. , and White, K. R. , 2008, “ Close-Range Photogrammetry Applications in Bridge Measurement: Literature Review,” Meas.: J. Int. Meas. Confed., 41(8), pp. 823–834. [CrossRef]
Poling, J. , and Desai, N. , 2017, “Effect of Out-of-Plane Specimen Movement on the Accuracy of the Smallest Specimen Strain Measurable Using the Digital Image Correlation Technique,” Proc. SPIE, 10170, p. 101702L. [CrossRef]
Desai, N. , Poling, J. , Fischer, G. , and Georgakis, C. , 2017, “ Small Strain Measurement Using Digital Image Correlation-Based iMETRUM in a Specimen Subjected to Out-of-Plane Movement,” Fifth Annual International Conference on Architecture and Civil Engineering (ACE), Singapore, May 8–9, pp. 164–183.
GOM, 2017, “ARAMIS,” GOM GmbH, Braunschweig, Germany, accessed Dec. 19, 2017, http://www.gom.com/metrology-systems/aramis.html
Matsumoto, T. , and Motomura, S. , 1984, “Test of Welding Technique for Repair of Steel Highway Bridges,” Transportation Research Board, National Research Council, Washington, DC, Transportation Research Record No. 950, pp. 157–163.
U. S. Department of Transportation, 2012, “Steel Bridge Design Handbook: Bridge Steels and Their Mechanical Properties,” Vol. 1, U. S. Department of Transportation, Federal Highway Administration, Washington, DC, Publication No. FHWA-IF-12-052. https://www.fhwa.dot.gov/bridge/steel/pubs/if12052/volume01.pdf

Figures

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Fig. 5

The loading apparatus. From top down: specimen, linkage, 100 kN load cell, clevis, platform.

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Fig. 4

The threaded rod that applied the displacements by turning clockwise

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Fig. 3

The caliper to measure the displacements

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Fig. 2

The specimen with the support to prevent buckling (above), with the apparatus to apply the displacement

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Fig. 1

Specimen schematic (specimen face as seen by sensor)

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Fig. 12

The 14 kg test: load versus strain of 3D ARAMIS

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Fig. 13

The 25 kg test: load versus strain of 2D ARAMIS

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Fig. 14

The 25 kg test: load versus strain of 3D ARAMIS

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Fig. 15

The 35 kg test: load versus strain of 2D ARAMIS

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Fig. 16

The 35 kg test: load versus strain of 3D ARAMIS

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Fig. 17

The 45 kg test: load versus strain of 2D ARAMIS

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Fig. 18

The 45 kg test: load versus strain of 3D ARAMIS

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Fig. 19

The 55 kg test: load versus strain of 2D ARAMIS

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Fig. 20

The 55 kg test: load versus strain of 3D ARAMIS

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Fig. 9

The 10 kg test: load versus strain of 2D ARAMIS

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Fig. 10

The 10 kg test: load versus strain of 3D ARAMIS

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Fig. 11

The 14 kg test: load versus strain of 2D ARAMIS

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Fig. 6

Final speckled spray pattern that was used for all tests

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Fig. 7

The Nikon D800 camera is placed 100 mm from the specimen with a 60 mm lens. The light is also shown illuminating the specimen.

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Fig. 21

The 95 kg test: load versus strain of 2D ARAMIS

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Fig. 22

The 95 kg test: load versus strain of 3D ARAMIS

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Fig. 23

R-squared values in percent versus strain values in percent for 2D ARAMIS

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Fig. 24

R-squared values in percent versus strain values in percent for 3D ARAMIS

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