Using optical full-field measurement based on digital image correlation to measure strain on a tree subjected to mechanical load

0428997 - ÚTAM 2015 RIV US eng J - Journal Article
Sebera, V. - Praus, L. - Tippner, J. - Kunecký, Jiří - Čepela, J. - Wimmer, R.
Using optical full-field measurement based on digital image correlation to measure strain on a tree subjected to mechanical load.
Trees: structure and function. Roč. 28, č. 4 (2014), s. 1173-1184. ISSN 0931-1890. E-ISSN 1432-2285
Institutional support: RVO:68378297
Keywords : digital image correlation * tree biomechanics * strain * pulling test * arboriculture * nondestructive
Subject RIV: JJ - Other Materials
Impact factor: 1.651, year: 2014

The goal of this study was to analyze and measure the displacement and strain response behavior of the tree (Juglans regia L.) subjected to a mechanical load. The analysis addresses issues of tree biomechanics that call for a high-quality deformation data measured on trees’ surfaces in a noninvasive way. For these purposes, the 3D digital image correlation (3D-DIC) was proposed and tested against standard extensometers. The measured tree was subjected to a bending by a pulling test to induce strain on the tree stem. The DIC technique successfully provided strain field on a tree bark despite its highly complicated geometry. Vertical averaging of the strain field obtained by the DIC revealed that a tree stem behaves according to beam theory exhibiting compression and tension parts. The absolute values of strain measured by both techniques agree with each other in order of magnitude, DIC returning lower values (approximately 21.1 and 40.8 % for compression and tension part, respectively). The results reveal necessity for future study of stress/strain transfer from xylem to bark. The sensitivity analysis shows that the computed strain highly depends on subset size used in the DIC computation. Based on the projection error and strain, the optimal subset size was found out to be between 21 and 31 pixels. The measurement proved that the DIC method can be successfully used in tree biomechanics. In general, our results and the character of DIC technique that allows testing at different scales depending on imaging methods indicate its big potential in plant biomechanics.
Permanent Link: http://hdl.handle.net/11104/0238994