Construction Engineering- Characteristics and Application of Wood and Wood Products 1.Wood moisture index The most important moisture content index affecting wood physical and mechanical properties and application is fiber saturation point and equilibrium moisture content. (1) Fiber saturation point is the moisture content of wood when the absorbed water in cell wall is saturated and there is no free water in cell cavity and cell gap.Its value varies with tree species, generally 25%-35%, with an average value of 30%. It is a turning point for wood physical and mechanical properties to change with water content. (2) Equilibrium moisture content refers to the moisture content in wood when it reaches the dynamic equilibrium of absorption and volatilization with moisture in surrounding air.Equilibrium moisture content is a water content index that should be controlled to avoid deformation or cracking when wood and wood products are used. 2.Wood's Wet Expansion, Dry Shrinkage and Deformation (1) Wood deformations, i.e. wet swelling and dry shrinkage, occur only when the content of water adsorbed in the cell wall changes. (2) Wet swelling and shrinkage will affect the use of wood. Dry shrinkage will make wood warp, crack, tenon loosening and loose joints.Wet swelling can cause surface bulging, so wood should be pre-dried before processing or use to make it close to the equilibrium moisture content in accordance with environmental humidity. (3) The deformations of wood are also different in different directions, with the smallest along the grain direction, the larger radial direction and the largest chord direction. 3.Wood Strength Wood can be divided into four kinds of strength according to the stress state: tensile strength, compressive strength, flexural strength and shear strength, while tensile strength, compressive strength and shear strength can be divided into parallel and transverse lines.The direction of action is only parallel to the direction of fibers; the direction of action is perpendicular to the direction of fibers. 4.Solid wood flooring (1) Technical requirements: The technical requirements of solid wood flooring include grading, appearance quality, processing accuracy and physical performance.Among them, the physical and mechanical properties are as follows: water content (7%<water content <the equilibrium water content of wood in all areas of use in China); the difference between the maximum and minimum average water content of the same batch of floor specimens shall not exceed 4.0%, and the difference between the maximum and minimum water content of the same board shall not exceed 4.0%, the wear resistance of the surface of the paint board, the adhesion of the paint film and the hardness of the paint film.The appearance of solid wood flooring, such as Easter, Dead Joint, Corrosion and Processing Corrugation, should meet the corresponding quality requirements, but the antique flooring does not require this.According to the appearance quality and physical properties of the products, solid wood flooring can be divided into high-quality products, first-class products and qualified products. (2) Application: Solid wood floor is suitable for floor decoration of gymnasium, training room, stage and residence.
Construction Engineering-Characteristics and Application of Wood and Wood Products
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Uploaded by admin on 2019-10-15 13:46:55