Improved 3D displacement measurements method and calibration of a combined fringe projection and 2D-DIC system

Siegmann, Philip; Felipe-Sesé, Luis; Díaz-Garrido, Francisco-Alberto

doi:10.1016/j.optlaseng.2016.08.014

Cited by 13 publications

(6 citation statements)

References 20 publications

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“…For example, for the 1st experiment introduced in this paper, (x 0A , y 0A ) = (468, 132), L = 0.045 mm/pixel and z 0 = 329 mm. Details of calibration process to obtained these parameters are given in [25]. Nevertheless, since the out-of-plane distances (maximum value of 3 mm) are much smaller than z 0 , the second correction is negligible in our experiments and ∆x s ∼ = L • ∆x s,c (the mean of the absolute value of the differences is 6 • 10 −4 mm).…”

Section: In-plane Displacements Measurements and Correctionsmentioning

confidence: 86%

“…In the present work, a self-made full-field technique combining 2D-DIC and fringe projection (FP), (FP + 2D-DIC) is used to obtain the 3D displacement maps of the surface of cylindrical specimens subjected to a tensile test. The 2D-DIC makes possible to measure the in-plane displacements of the surface elements in x-and y -direction and, FP uses an additional fringe projector to measure the out-of-plane (z-displacements) [23][24][25].The obtained axial displacement (AD) profiles and the 3D shape around the necking zone are then used to localize and determine the necking parameters at each load stage in a well-established and reproducible way. This method also allows finding an empirical axial displacement equation, for estimating each surface element of our cylindrical specimens at the necking zone.…”

Section: Measurement Science and Technologymentioning

confidence: 99%

“…The whole 2D-DIC + FP system is mounted on a tripod, which enables the correct configuration and alignment of the set-up. The detailed alignment and calibration procedures have previously been described in [24,25]. Furthermore, the specimen needs to be painted with red speckles on a white background and the fringes must alternate in white and blue.…”

Section: Tensile Testmentioning

confidence: 99%

“…The out-of-plane displacements or z-positions were obtained using the FP technique on the fringe images of the R-channel (I R,s ), where the shifted phase of the projected fringes relative to the straight fringes corresponding to the plane reference surface (I 0 ) was calibrated and related to z-positions (in mm) using a second-order polynomic, the coefficients of which were obtained through a calibration process [25]. At any load stage s, the matrix elements of the z-positions of the pixels z 2,s (i, j) were obtained.…”

Section: Out-of-plane Displacementsmentioning

confidence: 99%

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Experimental approach for the determination of the Bridgman’s necking parameters

Siegmann

Alén-Cordero

Montero

2019

Meas. Sci. Technol.

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Two ways of determining Bridgman’s parameters are presented to estimate the equivalent Bridgman stress–strain (BSS) curve after the onset of necking in cylindrical specimens. The accurate experimental determination of the minimum necking radius, rN, and the radius of curvature of the necking, RN, are considered to be the main problems in applying Bridgman’s model to obtain the equivalent BSS curve and describe the plastic behaviour of materials. Using the combined technique of 2D digital image correlation and fringe projection, the 3D positions and displacements of the surface elements are determined for each load stage of a tensile test on steel, aluminium (Al) and copper (Cu) bars. The axial displacements are well fitted with an empirical function that allows accurate estimation of the beginning of necking and its location on the specimen. From the 3D positions, both Bridgman’s parameters are estimated by adjusting a torus to the necking zone. The 3D measurements around the necking position have to be well defined to obtain the parameters in a feasible way, because the real necking profile does not fit well with the half-circle proposed by Bridgman. Nonetheless, the estimated rN parameters are noisy, affecting the BSS curve. Therefore, an alternative and simpler way for estimating rN and RN is also proposed, only requiring the measurement of total axial displacements along the loading axis of each surface element. In this way, the BSS curve obtained is smooth, although it somewhat underestimates the same curve obtained using experimentally measured 3D data.

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Section: In-plane Displacements Measurements and Correctionsmentioning

confidence: 86%

Section: Measurement Science and Technologymentioning

confidence: 99%

Section: Tensile Testmentioning

confidence: 99%

Section: Out-of-plane Displacementsmentioning

confidence: 99%

See 2 more Smart Citations

Experimental approach for the determination of the Bridgman’s necking parameters

Siegmann

Alén-Cordero

Montero

2019

Meas. Sci. Technol.

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“…In addition, FP requires the fringe constant, K f (mm/radian) and inevitably Δ ϕ , produced by the fringe displacement due to the z -displacement. All these parameters can be obtained following a calibration process [ 40 , 47 ].…”

Section: Fundamentalsmentioning

confidence: 99%

RGB Colour Encoding Improvement for Three-Dimensional Shapes and Displacement Measurement Using the Integration of Fringe Projection and Digital Image Correlation

Felipe-Sesé

Molina-Viedma

López‐Alba

et al. 2018

Sensors

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Three-dimensional digital image correlation (3D-DIC) has become the most popular full-field optical technique for measuring 3D shapes and displacements in experimental mechanics. The integration of fringe projection (FP) and two-dimensional digital image correlation (FP + DIC) has been recently established as an intelligent low-cost alternative to 3D-DIC, overcoming the drawbacks of a stereoscopic system. Its experimentation is based on the colour encoding of the characterized fringe and speckle patterns required for FP and DIC implementation, respectively. In the present work, innovations in experimentation using FP + DIC for more accurate results are presented. Specifically, they are based on the improvement of the colour pattern encoding. To achieve this, in this work, a multisensor camera and/or laser structural illumination were employed. Both alternatives are analysed and evaluated. Results show that improvements both in three-dimensional and in-plane displacement are obtained with the proposed alternatives. Nonetheless, multisensor high-speed cameras are uncommon, and laser structural illumination is established as an important improvement when low uncertainty is required for 2D-displacement measurement. Hence, the uncertainty has been demonstrated to be reduced by up to 50% compared with results obtained in previous experimental approaches of FP + DIC.

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Comparative of conventional and alternative Digital Image Correlation techniques for 3D modal characterisation

et al. 2020

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Improved 3D displacement measurements method and calibration of a combined fringe projection and 2D-DIC system

Cited by 13 publications

References 20 publications

Experimental approach for the determination of the Bridgman’s necking parameters

Experimental approach for the determination of the Bridgman’s necking parameters

RGB Colour Encoding Improvement for Three-Dimensional Shapes and Displacement Measurement Using the Integration of Fringe Projection and Digital Image Correlation

Comparative of conventional and alternative Digital Image Correlation techniques for 3D modal characterisation

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