Aserrado 2001. A simulation software inter-relating growth stresses distribution inside standing trees, sawing patterns, variations of wood mechanical characteristics, and distortions of boards

Aserrado 2001 is a simulation software designed in the framework of the project "Sawmilling systems suitable for European Eucalyptus globulus affected by growing stresses" (coordinator CIS Madera, Galicia, Spain). This software is based on mechanical modelling linking models of distribution of growth stresses, mechanical behaviour of wood inside tree, geometrical characteristics of the logs, end splitting distribution models, and sawing distortions. It aimed at supplying practical information about growth stresses releasing effect and further outcomes on processing, in particular: level of boards distortions, primary / secondary sawing yields, distribution of sawn products for each orientation (quarter sawn, intermediate, flat sawn). Its design is based on the utilization of simple and realistic inputs at the level of the sawmill. The objective is to provide sawyers with computer-aided tools to support their choices based on objective criteria. The approach is essentially mono dimensional, using simple principles of Strength of Material theory complemented with simplifying assumption regarding the initial distribution of growth stresses in a log and the constitutive equation of the material. The log is divided along its length into several portions, to allow conicity and diameter variations. Each board is analyzed as a beam that bends due to the gradient of released growth stress along its cross-section. Experimental validation has been performed according to two kinds of sawing patterns. Initial growth strains were measured on the standing tree and on the log before sawing, using the single-hole method. Comparison with measured deflections and strains gave satisfactory results. In addition to deflections resulting from the growth stress release, the software takes into account the existence of a knotty core and a sapwood region to be optionally eliminated, as well as the losses expected from the crack propagation. (Texte intégral