Self-calibration for lab-<i>μ</i>CT using space-time regularized projection-based DVC and model reduction

Jailin, Clément; Buljac, Ante; Bouterf, Amine; Poncelet, Martin; Hild, François; Roux, Stéphane

doi:10.1088/1361-6501/aa9818

Cited by 15 publications

(19 citation statements)

References 47 publications

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“…The so-called DIC-PGD framework has been developed to directly extract the dominant displacement modes (using space [175,80] or space-time [111] separation) and provides big savings. However, for the sake of simplicity, this option is not followed herein.…”

Section: Space-time Regularizationmentioning

confidence: 99%

Digital Volume Correlation: Review of Progress and Challenges

et al. 2018

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3D imaging has become popular for analyzing material microstructures. When time lapse series of 3D pictures are acquired during a single experiment, it is possible to measure displacement fields via digital volume correlation (DVC), thereby leading to 4D results. Such ForewordThe present paper aims at reviewing the major developments in Digital Volume Correlation (DVC) over the past ten years. It follows the first review on DVC that was published in 2008 by its pioneer [11]. In the latter, the interested reader will find all the general principles associated with what is now called local DVC. They will not be recalled hereafter. In such approaches the region of interest is subdivided into small subvolumes that are independently registered. In addition to its wider use with local approaches, DVC has been extended to global approaches in which the displacement field is defined in a dense way over the region of interest. Kinematic bases using finite element discretizations have been selected. To further add mechanical content, elastic regularization has been introduced. Last, integrated approaches use kinematic fields that are constructed from finite element simulations with chosen constitutive equations. The material parameters (and/or boundary conditions) then become the quantities of interest.These various implementations assume different degrees of integration of mechanical knowledge about the analyzed experiment. First and foremost, DVC can be considered as a stand-alone technique, which has seen its field of applications grow over the last ten years. In this case the measured displacement fields and post-processed strain fields are reported. With the introduction of finite element based DVC, the measured displacement field is continuous. It is also a standalone technique. However, given the fact that it shares common kinematic bases with numerical simulations, it can be easily combined with the latter. One route is to require local satisfaction of equilibrium via mechanical regularization. Another route is to fully merge DVC analyses and numerical simulations via integrated approaches. Different examples will illustrate how these various integration steps can be tailored and what are the current challenges associated with various approaches.

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Section: Space-time Regularizationmentioning

confidence: 99%

Digital Volume Correlation: Review of Progress and Challenges

et al. 2018

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“…It is also worth emphasizing that the same spirit has also been used very recently in 4D-DVC (i.e., dealing with 3D space and 1D time displacement fields), also separating time from space [48]. Here again, this PGD approach revealed extremely rewarding.…”

Section: Introductionmentioning

confidence: 91%

Mode-enhanced space-time DIC: applications to ultra-high-speed imaging

Berny

Jailin²,

Bouterf³

et al. 2018

Meas. Sci. Technol.

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Digital Image Correlation (DIC), which consists in registering image pairs to measure displacement fields, can be tailored to analyze image sequences from videos taking advantage of a common reference image. In the present study it is no longer the first image of the sequence but rather a computed image from the entire video. The sought kinematics, which is separated in space and time, offers the opportunity to extract "modes," each of which is a spatial displacement field multiplied by a scalar function of time only. These modes are not chosen a priori but rather computed from a specific formulation of DIC so that they capture the displacements at best. The exploited mathematical technique to achieve this modal representation is a form of Proper Generalized Decomposition (PGD) that makes use of the DIC variational formulation, where both spatial and temporal regularizations can be included. Two image videos acquired with an ultra-high speed camera at 5 and 10 million frames per second are analyzed to illustrate the proposed technique. Very large computation time gains are obtained with no noticeable differences in the kinematic measurements. Moreover, it is shown that motions have a lower complexity, i.e., require less modes, than the direct Proper Orthogonal Decomposition (or Principal Component Analysis) Mode-enhanced space-time DIC: Applications to ultra high-speed imaging 2 performed on the entire video.

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“…An extension of this method has been applied to an online calibration ( i.e., calibrated from the sample motion during the scanning process) of the tomograph [23]. An initial (blurry) reconstruction was performed from a set of initial parameters.…”

Section: Data Driven Reconstruction Of Non-rigid Samplesmentioning

confidence: 99%

Dynamic Tomographic Reconstruction of Deforming Volumes

Jailin

Roux

2018

Materials

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The motion of a sample while being scanned in a tomograph prevents its proper volume reconstruction. In the present study, a procedure is proposed that aims at estimating both the kinematics of the sample and its standard 3D imaging from a standard acquisition protocol (no more projection than for a rigid specimen). The proposed procedure is a staggered two-step algorithm where the volume is first reconstructed using a “Dynamic Reconstruction” technique, a variant of Algebraic Reconstruction Technique (ART) compensating for a “frozen” determination of the motion, followed by a Projection-based Digital Volume Correlation (P-DVC) algorithm that estimates the space/time displacement field, with a “frozen” microstructure and shape of the sample. Additionally, this procedure is combined with a multi-scale approach that is essential for a proper separation between motion and microstructure. A proof-of-concept of the validity and performance of this approach is proposed based on two virtual examples. The studied cases involve a small number of projections, large strains, up to 25%, and noise.

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Self-calibration for lab-μCT using space-time regularized projection-based DVC and model reduction

Cited by 15 publications

References 47 publications

Digital Volume Correlation: Review of Progress and Challenges

Digital Volume Correlation: Review of Progress and Challenges

Mode-enhanced space-time DIC: applications to ultra-high-speed imaging

Dynamic Tomographic Reconstruction of Deforming Volumes

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