Linear window correlation: new image processing based approach to strain distribution analysis of wood

An in-depth understanding of the response of wood under compression/densification calls for characterization of strain distribution over the wood. Recently, an image processing technique has been used for strain evaluation on wood, as the traditional devices are not able to measure irregularly distributed strain field. Unfortunately, the classic image correlation algorithm is rather time consuming and could take up to days to compute the final result. In this paper, an improved image correlation algorithm with linearly changed searching region during the correlation seeking is presented. The processing speed is increased by over 1800 times while keeping the high accuracy of the displacement measurement. In addition, full feasibility tests were conducted on balsam fir (Abies balsamea (L.) Mill.) and eastern white pine (Pinus strobus L.) samples.The results demonstrate the high robustness, efficiency, and accuracy of the proposed method. Une connaissance approfondie de la reaction du bois soumis a la compression ou a la densification exige la carac-terisation de la distribution des tensions dans le bois. La technique de traitement des images a recemment ete utilisee pour evaluer les tensions dans le bois etant donne que les appareils traditionnels ne sont pas capables de mesurer un champ de tension distribue de facon irreguliere. Malheureusement, l'algorithme classique de correlation des images demande passable-ment de temps et pourrait prendre plusieurs jours pour calculer le resultat final. Dans cet article, nous presentons un algo-rithme de correlation d'images ameliore avec une zone de recherche lineairement modifiee pendant la recherche de correlations. La vitesse de traitement est 1 800 fois plus rapide tout en conservant la precision elevee de la mesure des de-placements. De plus, des tests complets de faisabilite ont ete realises sur des echantillons de sapin baumier (Abies balsamea (L.) Mill.) et de pin blanc (Pinus strobus L.). Les resultats demontrent que la methode proposee est tres robuste, efficace et precise. [Traduit par la Redaction]
Introduction Recently, wood densification has attracted the attention of researchers (Wang and Cooper 2005; Gong et al. 2006). This technology allows utilization in new applications of wood from some fast-growing [...]