Two-dimensional simulation of mechanical stresses during isothermal drying of Eucalyptus nitens wood

Abstract

In this work, a two-dimensional mathematical model of the moisture transport and stress-strain phenomena during the conventional drying process of Eucalyptus nitens wood is presented. The model consists of a system of partial differential nonlinear second-order equations, where the moisture transport phenomenon is modeled on the concept of effective diffusion, and the stresses are modeled on the hypothesis of viscoelastic deformation, which is strongly linked to the strains by free contraction and mechano-sorption. The drying was assumed as an isothermal process and without effects of sustained loads over time (creep). Experimental tests were also carried out under constant psychometric conditions at 30/25 (°C/°C) in order to obtain transient distributions of moisture and stress. From these experimental data, the physical parameters of the proposed mathematical model were obtained by optimization in a context of inverse problem. The numerical solution of the model was obtained through the method of control volumes combined with finite elements. The results of transient distribution of moisture and stress correlate well with the experimental data.

Non-Destructive Assessment of the Dynamic Elasticity Modulus of Eucalyptus nitens Timber Boards

“…Firstly, the recommendation of [ 44 ] was followed to approximate some elastic properties of hardwoods as a proportion of E xdt ( ). Secondly, a constant value of 0.35 was assumed for the three Poisson coefficients, as indicated in other investigations [ 4 , 5 ]. Finally, the local variation of E xdt was implemented by dividing the wood boards into 12 segments each of them with a length of 200 mm.…”

“…Despite the potential of Eucalyptus nitens timber to be used as a structural element, its application in Chile is still incipient. On the one hand, the tensions induced by the tree growth processes and the subsequent drying process of the sawn timber affect the quality of its mechanical properties [ 5 , 6 ]. On the other hand, since Chilean Eucalyptus nitens forests are mainly managed for the pulp and paper industry, tree pruning or thinning processes are not usual, since the aim is to saw the wood in short rotation periods.…”

Drying Stress and Strain of Wood: A Review

“…The mechanical hygroscopic strain and delayed elastic strain were considered in this model [48]. Salinas et al tested and simulated the drying stress of Pinus radiata D. Don, and obtained the solutions by combining the method of volume control and finite element [53,54]. Then, a two-dimensional mathematical model of stress in the conventional drying process of eucalyptus was established based on the assumption of viscoelastic deformation [54].…”