Predicting oak wood properties using X-ray inspection: representation, homogenisation and localisation. Part I: Digital X-ray imaging and representation by finite elements

Abstract

This paper is the first part of a complete modelling where wood is a 2D composite material. It proposes a comprehensive approach to predict the elastic and shrinkage properties of oak wood in the transverse plane from the local properties of the anatomical tissues and the actual morphology of those tissues. Part I is devoted to the methodology of representation. According to oak anatomy, the representative elementary volume used in this work consists of one annual ring limited in the tangential direction by large zones of ray cells. A high-resolution digital X-ray imaging device was built to represent the spatial distribution of tissues directly from cross-sections of wood. A complete image processing, in- cluding image segmentation and partitioned boundaries of tissues (ray cells, big vessels, etc.), was developed; which makes it possible to build a finite element mesh from these images. Thanks to the control of mesh refinement, the number of triangular elements is minimized while a good description of the anatomical structure is obtained. Using these F.E. meshes, Part II will present the homogenization principle and a few exam- ples of calculations of the properties. Macroscopic properties (mechanical and shrinkage) and some localization problems are computed and il- lustrated.