@article{11403919672e48e487ce804b8d353cb6,
title = "Vermiculate artefacts in image analysis of granular materials",
abstract = "Some reported analyses of images of deforming granular materials have generated surprising vermiculate strain features which are difficult to reconcile with the mechanics of deformation of granular matter. Detailed investigation using synthetic images and improved processing of images of laboratory experiments indicates that such features can emerge as a consequence of the image acquisition (sensor, contrast, resolution), the subsequent image correlation implementation, and the user's choice of processing parameters. The two principal factors are: (i) the texture and resolution of the images and (ii) the algorithm used to achieve sub-pixel displacement resolution. Analysis of the images using a sub-pixel interpolation algorithm that is more robust than that used originally eliminates the vermiculate features for images with moderate resolution and texture. However, erroneous features persist in images with low resolution and poor texture. Guidance is provided on ways in which such artefacts can be avoided through improved experimental and image analysis techniques.",
keywords = "Digital image correlation, Granular materials, Sub-pixel interpolation, Vermiculation",
author = "Sam Stanier and Jelke Dijkstra and Danuta Le{\'s}niewska and James Hambleton and David White and {Muir Wood}, David",
note = "Funding Information: The work forms part of the activities of the Centre for Offshore Foundation Systems (COFS) at the University of Western Australia, which is supported by the Lloyd{\textquoteright}s Register Foundation as a Centre of Excellence and is a node of the Australian Research Council (ARC) Centre of Excellence in Geotechnical Science and Engineering . Jim Hambleton was seconded to University of Western Australia under the aegis of the ARC Centre of Excellence in Geotechnical Science and Engineering. Jelke Dijkstra is supported by an Intra-European Fellowship EC/FP7-MC-IEF 623613 EMPIRC . Danuta Le{\'s}niewska was supported by NCN Grant No. 2011/03/B/ST8/05865 . David White holds the Shell Energy and Minerals Institute (EMI) Chair in Offshore Engineering. David Muir Wood is particularly grateful for the support of the Centre for Offshore Foundation Systems, University of Western Australia through the award of the Martin Fahey Visiting Fellowship during 2013. He also acknowledges the support of the Northern Research Partnership of Scottish universities at Dundee University and the invaluable support of the British Council in making initial experimental contacts for photoelastic and image analysis of granular materials. Publisher Copyright: {\textcopyright} 2015 Elsevier Ltd.",
year = "2016",
month = feb,
day = "1",
doi = "10.1016/j.compgeo.2015.11.013",
language = "English (US)",
volume = "72",
pages = "100--113",
journal = "Computers and Geotechnics",
issn = "0266-352X",
publisher = "Elsevier BV",
}