Follow-up of a panel restoration procedure through image correlation and finite element modeling

Abstract

International audienceResidual stress estimation is an important question for structural integrity. Since residual stresses are self-balanced stress fields, a classical way to obtain information on them is to remove a part of the structure, and observe the structure displacement field arising from the stress redistribution. The hole- drilling method is such an approach. In some cases, as for the present one concerning a painted panel of cultural heritage, the hole-drilling method is not suited (a structure with a complex geometry, few tests allowed) but one can take advantage of structural modifications if they are monitored (here, a restoration act). We therefore describe in this article a model updating approach, focusing on the residual stress estimation and not on the material parameter identification. This study couples an optical non-invasive shape measurement (digital image correlation, using a projected speckle pattern on the painted panel, with luminance compensation) and a numerical approach (3D finite elements) for the model updating. The 3D stereo-correlation is used to measure a partial displacement field between three different states of the structure (at three different times of the restoration act). The numerical part concerns stress evaluation, once the model and the experiments are compared using a geometric mapping and a spatial projection of discrete fields. Using modeling and identification, the simulation is used to obtain the residual stresses in the panel, before and after the restoration

Evaluating the use of digital image correlation for strain measurement in historic tapestries using representative deformation fields

“…), though clearly this is not an option when analysing valuable historic tapestries. Consequently, previous attempts to use DIC with tapestries (and also oil paintings) have used the inherent image and texture of the artwork itself to track displacements. Nevertheless, while promising, such an approach can lead to significant hidden errors in the DIC measurements, potentially large enough to throw doubt on interpretations of the results.…”

On the analysis of canvas wrinkling via isogeometric stereocorrelation

“…One critical issue associated with stereocorrelation is to have sucient image 15 contrast to enable the registration to succeed (Khennouf et al, 2010;Dureisseix et al, 2011). If natural contrast is not sucient, ad hoc procedures may be considered, for instance, by projecting a random pattern in addition to the negative image of the original surface (Dureisseix et al, 2011).…”

“…If natural contrast is not sucient, ad hoc procedures may be considered, for instance, by projecting a random pattern in addition to the negative image of the original surface (Dureisseix et al, 2011). This method allows 3D shapes to be measured.…”

“…The aim of the present work is to use global approaches to stereocorrelation Dufour et al, 2015a;Dubreuil et al, 2016), which consist of measuring 3D shapes and surface displacements when registrations are performed over the whole surface of interest and not locally as in the afore-30 mentioned approaches (Khennouf et al, 2010;Dureisseix et al, 2011;Malowany et al, 2014). Consequently, if some contrasted zones exist, the shape and displacement interpolations will allow the sought information to be assessed everywhere.…”

Automatic Frames Extraction and Visualization From Noisy Fringe Sequences for Data Recovering in a Portable Digital Speckle Pattern Interferometer for NDI

“…Well-known methods for measuring global deformations of wooden boards employ displacement transducers [28], fiber Bragg gratings glued to different critical points [29], or digital image correlation technique and finite element modeling [30]. As an alternative DSPI can be employed, allowing for full-field measurements of out-of-plane displacements, without utilizing the complex set-up required by the methods mentioned above.…”