Anisotropic Theory of Growth Stresses in Trees

Growth stresses are a consequence of the growth process in trees; they arise from stresses which develop in each new peripheral sheath of wood cells. This situation is analysed using a linearly-elastic, three-dimensional orthotropic model for wood. Expressions for the stress and strain distributions in a tree are derived. Some previous experimental work is reinterpreted by analysing the stress and strain redistributions that occur during various cutting processes. It is shown that the discrepancy in the qualitative behaviour of the radial strain between previous theories and experimental measurements may be accounted for by the redistribution of stresses that occurs during the preparation of a cross-cut disc in the experiments.