RELATIONSHIP BETWEEN WOOD PROPERTIES AND DEFORMATIVITY UNDER DIFFERENT LOADING MODES

Modification of wood by pressing makes it possible to obtain a durable material from low-quality wood species. The relationship between the structure of natural and pressed wood and deformability was investigated in the works of B.I. Ogarkov, P.P. Erinsh, V.A. Shamaev, G.K. Gavrilov. Meanwhile, at present wood is subjected to deformation in a plasticized state, the structure and properties of which are different from the structure of natural wood. In this work, an attempt to establish the relationship between the structure of natural and plasticized wood and its main, deformative indicators (stiffness, modulus of elasticity, Poisson's ratio, etc.) has been made . As a result of the experiments, it was found that (according to the results of processing empirical diagrams "deformation - stress") a three-phase nature of deformation of natural birch wood and plasticized with TCL (thermocatalytic cracking liquid) oil was established with the calculation of stiffness indicators; the dependences of the Punch ratio at variable humidity and temperature during the pressing process for constant and variable loading rates were obtained. Hysteresis in wood under tension and compression for natural and plasticized wood has been studied

CREEP AND REVERSE CREEP OF NATURAL AND PLASTICIZED BIRCH WOOD WHEN PRESSING ACROSS THE FIBERS.

Pressed (modified) wood is a technological process of drying, impregnation and pressing (R 54577-2011 State Standard). The density of pressed wood, depending on the degree of pressing, ranges from 750 to 850 kg/m3. Strength, hardness toughness of this wood is several times greater than of natural wood. Coal oil, TCL (thermocatalytic cracking liquid), shale oil are most often used as wood antiseptics. They are plasticizers and change the nature of deformations during pressing.Experiments with natural and were conducted to obtain comparative data. Pressed wood contained 10% of TCL oily antiseptic by weight of absolute dry wood. Birch wood was used as the starting material. In this case, an antiseptic agent in an amount of 8-10% by weight of dry wood is evenly distributed over the entire cross section of the specimen. Direct and reverse creep was studied to assess time changes in deformation composition of wood, pressed across fibers. Measurements of direct and reverse creep of wood were carried out on a lever installation. The obtained modes can be used to optimize the technology of obtaining plasticized wood, because plasticization of wood with TCL oil reduces toughness 3-5 times (in the first phase of deformation), in the second phase - 1.1-1.5 times, in the third phase - 2.5-3 times. Transverse strain coefficient increases 1.2-1.3 times. Using creep curves of plasticized wood, it was found that oil impregnation gives 4-5 times greater reduction in the proportion of elastic deformations and, accordingly, increases the residual ones.