Pattern Changes of Wood Mechanical Properties in Time Under Reaction Confinement

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Abstract

The main sources of information about the properties of the material are diagrams of a particular type of sample test. However, numerous tensile, compression, bending, and twisting tests as well as other methods of loading could not help determine the mechanisms of the phenomena occurring in the materials at their plastic deformation (creep) and destruction. In scientific literature, there is no theoretical description of the process of deformation and confinement. On the basis of the experimental data, the authors aimed to develop a method describing behaviour of wood deformed at a constant rate to the given reaction value. The reaction is kept constant by additional material deformation up to complete destruction. The task was to derive an equation of material state which would allow us to describe behaviour of the material at any time under various loads and deformations. To analyze deformation diagrams and develop an equation describing the behaviour of the samples, the authors used a universal integrated environment Mathcad 2001 pro allowing one to convert nonlinear diagrams by taking logarithms and by differentiating (more precisely, by finite differences), making them linear and completing the search by statistical processing under the control of the correlation coefficient. These techniques helped determine the structure of creep equation, creep strength, and durability. Creep was accompanied by a decrease in coefficient of elasticity (as the reaction was maintained constant). This behaviour is inconsistent to the view of wood as a continuous medium. The structure of the wood shows up as a multi-dimensional network, nodes of which contain elements with properties of three series-connected circuits: the integrator, the first order relaxation circuit, and the delay component (in terms of the automatic control theory), which make up a structure (atoms, molecules, cells, and other compounds). The equation developed can be applied in the theories of elasticity, plasticity and creep.

Authors

V.F. Dunaev, Candidate of Engineering; V.I. Melekhov, Doctor of Engineering, Professor; M.V. Zakharov, Candidate of Engineering, Associate Professor

Affiliation

Northern (Arctic) Federal University named after M.V. Lomonosov

Keywords

wood, structure of wood, elements of the structure, parts of the elements, deformed wood, chart (experimental curve) deformation, creep, durability, reaction, relaxation limit, creep limit.

References

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