Автор: Todor Petkov
- CORRELATION BETWEEN PHYSICAL AND MECHANICAL PROPERTIES OF THE WOOD
The results of testing for the presence of correlation and how strong it is between some physical – mechanical properties - bending strength, modulus of elasticity in bending and density are established. This analysis compared the coefficients of correlation between one or more pairs of variables in order to determine statistical correlations between them. The results reflect the behavior of the test specimens made from the wood of various tree species common in Bulgaria – white pine, spruce, black pine, beech and oak.
Ключови думи: correlation coefficient, physical - mechanical properties of wood
- INFLUENCE OF THE APPLIED PRESSURE ON FINGER JOINED END-TO-END WOOD
In the production of finger-jointed details, it is most important to provide the required applied pressure to achieve the desired adhesion strength of the joint. The results of the study of beech wood elements (Fagus Sylvatica) are presented, with applied different pressure for the face ends of the details (0,4 and 0,7 N/mm2). The following properties have been determined of the tested samples: bending strength, modulus of elasticity and the density of wood. The pneumatic-piston system also provided for securing the bonding pressure in the longitudinal direction of the wood. In the carried – out experiments, it was used a polyvinyl acetate adhesive with a class of water resistance D3. The mechanical properties of the glued elements depend on their structure, the type of adhesive and the type of wood. The paper presents the values of strength and modulus of elasticity in static bending of elements derived from beech wood.
Ключови думи: beech wood, finger-joint, polyvinyl acetate adhesive, pneumatic-piston system
- INFLUENCE OF THE TYPE OF ADHESIVE ON THE PHYSICO-MECHANICAL PROPERTIES OF BEND FURNITURE BOARDS
In the manufacture of furniture structural elements from folded glued thin furniture panels, it is important to determine the parameters affecting the performance of the finished wood composite panels. The purpose of the study was to determine the effect of the type of adhesive used on laminated high-density laminated wood fiber boards (HDF) and poplar plywood. The test specimens are made of five layers of 2.8 mm thick HDF slats and 4 mm thick plywood with 260/100 mm glued plate dimensions. For bonding, three types of adhesives were used - polyvinyl acetate (PVA) dispersion adhesive Jowacoll 103.05, polyurethane (PU) dispersion adhesive - Jovapur 150.50 and polyurethane wood adhesive - SOUDAL 66A. Bending and gluing were performed in a laboratory vacuum press with a rubber membrane and a template with a radius of curvature of 150 mm. The time to achieve minimum technological adhesion strength, vacuum velocity and minimum bending radius are determined. Samples were tested by standard bending with shoulder collection. The results obtained are analyzed and presented graphically.
Ключови думи: glued bent furniture panels, HDF, polyvinyl acetate (PVA) dispersion adhesive, polyurethane (PU) dispersion adhesive, bending strength, vacuum presses