Дослідження січних модулів листяних та хвойних порід деревини з різним показником вологості

Abstract

Most wood-based materials, elements, products and structures work in both non-aggressive and aggressive environments. Aggressive also include environments with high humidity. Humidity of wood in such conditions is higher than standard (in an unprotected condition), that is more than 12 %. The humidity content of wood directly affects its physical and mechanical properties, in particular the initial modulus of elasticity and the modulus of deformation. The method of experimental researches of wooden prisms in the size of 30´30´120 mm on compression along fibers at a rigid mode of loadings (on increase of movements of a press of the testing machine) is in detail given. The following species of wood were tested: coniferous species — larch, pine, spruce; deciduous — birch, alder, ash. The trees from which the samples were made were grown, in particular, pine, spruce — in the forests of Rivne region; birch, alder, ash — in the forests of Volyn region; larch — in the forests of Ivano-Frankivsk region. The tested wood had a humidity content of 30 %, 21 %, 12 % at the age of 60 years and grade without defects and damage. Wood blanks were pre-dried in the laboratory to an average humidity of 30 % and in special drying chambers to a humidity of 21 % and 12 %. The humidity of the wood was controlled using a humidity meter MD-814. Experimental studies were performed on a servo-hydraulic testing machine STM-100 with an automated control and data recording system. On the basis of experimental researches diagrams (secant modulus—stress level) of continuous deciduous (birch, alder, ash-tree) and coniferous (larch, pine, spruce) breeds of wood were constructed. The initial modulus of elasticity and modulus of deformation of different types of wood in the range from 30 % to 12 % of humidity were obtained experimentally and theoretically. It is established that with a decrease in humidity from 30 % to 12 %, the strength of wood of all species increases the initial modulus of elasticity and the modulus of deformation increases significantly