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Investigation of the grid method for accurate in-plane strain measurement

Abstract : This paper deals with the accurate measurement of the in-plane strain components on a deformed specimen using the grid method. A crossed grid transferred on the specimen surface is used for this purpose. Images of this grid are captured with a CCD camera before and after deformation. The complete strain state is deduced by processing these images with a suitable procedure described in the paper. The originality of this procedure is twofold. The first one is to determine the phase derivatives directly from the images. The second one is to compensate local variations of the grid pitch as well as local rotations of the grid, because these two phenomena may corrupt the final strain maps if they are not taken into account. The metrological performance of this procedure is assessed and discussed in terms of accuracy, measurement noise and spatial resolution. Two types of tests are used for this purpose: a translation and a rotation. These tests simulate the effect of rigid-body motion in a strain field that is rigorously equal to zero. One example finally illustrates the procedure: a tensile test performed on an open-hole specimen.
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Contributor : Migration Irstea Publications <>
Submitted on : Friday, May 15, 2020 - 4:26:18 PM
Last modification on : Monday, February 22, 2021 - 9:14:10 AM

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C. Badulescu, M. Grédiac, Jean-Denis Mathias. Investigation of the grid method for accurate in-plane strain measurement. Measurement Science and Technology, IOP Publishing, 2009, 20 (9), pp.17. ⟨10.1088/0957-0233/20/9/095102⟩. ⟨hal-02592632⟩



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