Stresses in a Lumber Pile in the Process of Drying in a Convective Drier
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 4, July, 2020
STRESSES IN A LUMBER PILE IN THE PROCESS OF DRYING IN A CONVECTIVE DRIER V. A. Sychevskii
UDC519.6:539.536
Numerical calculation of the three-dimensional stress–strain state of a lumber pile in the process of drying in a convective drier is presented. The solution is obtained with the aid of the program complex ANSYS allowing one to develop and visualize three-dimensional geometric constructions. The results of the work can be used for carrying out computational experiments on drying materials in chambers and in developing the regimes of drying lumber piles by analyzing their stress–strain state and for designing drying facilities. Keywords: convective drier, lumber pile, numerical calculation, computational experiment. Introduction. Stresses and strains arising in lumber in the process of convective drying can cause their deformation, cracking, and even destruction. To prevent the appearance of the indicated defects in the lumber, it is necessary to know the conditions under which they appear. The stress–strain state of the lumber in the process of drying in a convective drier is affected by the drying regime (temperature, moisture content), initial heating of materials, their laying, aerodynamics of the heat carrier, construction of the drier, and the location of screens in the latter. Because of the difficulty of determining the stress–strain state of the lumber materials in the process of convective drying, the technological regimes of drying are determined with account for the moisture content of materials, i.e., indirectly, that is, approximately. With the development of computational technique, it has become possible to solve three-dimensional problems of the stress–strain state of lumber piles in convection-type driers. The significance of such a calculation is due to the absence of reliable experimental methods of determining the stress–strain state of lumber and timber piles. Calculations of stresses and strains in single lumber pieces were carried out by many authors. In works [1, 2], stresses in the lumber were determined by representing a board as a system of a large number of rigidly connected rods whose lengths are oriented across the board fibers. A serious shortcoming of such a method is that the stress in the board is considered to be a scalar quantity. In [3, 4], analytical solutions were obtained for the linearized problem of the elasticity of a wooden disk. It has been established that the basic factor that determines the mechanical behavior of such a disk in the process of its drying is the difference of the moisture contents in the heart-wood of the disk and of its sap-wood. However, the field of moisture content in the disk material was not determined, whereas the difference in the moisture contents needed for analytical calculations was assigned arbitrarily. In [5], a more complex problem of nonisothermal transfer of moisture and stresses in drying a single board was considered, for the solution of which semi-an
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