Wood (English name: Solid Wood) is an indispensable material in human life. It has the advantages of light weight, high strength and easy processing. Some trees have beautiful textures, but they are also easily deformed, perishable and flammable. The texture is uneven, the strength is inconsistent in all directions, and there are often natural defects. Therefore, in order to understand the importance of wood, wood can be used correctly.
Wood strength
Uneven texture, inconsistent strength in all aspects is an important feature of wood, but also its shortcomings. The strength of the wood along the trunk (commonly known as the grain) is much greater than the transverse (horizontal) of the vertical trunk. The picture shows the compressive strength of the three directions of pine and miscellaneous wood. The strength of each aspect can be found from the structure and arrangement of tubular cells. Wood fiber has the strongest longitudinal connection, so the tensile strength of the grain is the highest. The wood is pressed against the grain, and each cell looks like a column. The pressure is so large that the cell wall warps inward and then breaks. Therefore, the compressive strength of the grain is smaller than the tensile strength of the grain. When the horizontal stripes are pressed, the tubular cells are easily crushed, so the strength is only about 1/8 of the compressive strength of the grain, and the bending strength is between the tensile and compressive strengths.
The highest tensile strength of wood is the tensile strength of the standard test piece. In fact, wood often has knots such as knots, twill, cracks, etc., so the tensile strength will be much lower, and the strength value will not be Stable, generally wood is used as a pressing member such as column, pile, diagonal bracing, truss on the roof truss, etc. The impact of rickets on the compressive strength of the grain is not great, and the strength value is also relatively stable. The woodworker often said that "the top of the tree is a thousand pounds", which is a good expression of the strong resistance of the wood. Wood is also used as a bent member such as beams and plates. The wood of the bent members must be carefully selected to avoid the impact of rickets.
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