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When testing wood in lumber form, the Janka test is always carried out on wood from the tree trunk (known as the heartwood), and the standard sample (according to ASTM D143) is at 12% moisture content and clear of knots. [3] The hardness of wood varies with the direction of the wood grain. Testing on the surface of a plank, perpendicular to the ...
Wood grain is the longitudinal arrangement of wood fibers [1] or the pattern resulting from such an arrangement. [2] R. Bruce Hoadley wrote that grain is a "confusingly versatile term" with numerous different uses, including the direction of the wood cells (e.g., straight grain, spiral grain), surface appearance or figure, growth-ring placement (e.g., vertical grain), plane of the cut (e.g ...
It specifically refers to the longitudinal alignment of cells, or the direction in which the fibers are going. [4] The six types of grain are: straight, irregular, diagonal, spiral, interlocked, and wavy. The directional of the grain directly corresponds with the strength of the wood. [5]
A familiar example of an orthotropic material is wood. In wood, one can define three mutually perpendicular directions at each point in which the properties are different. It is most stiff (and strong) along the grain (axial direction), because most cellulose fibrils are aligned that way.
Knots affect the technical properties of the wood, usually reducing tension strength, [10] but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the ...
Wood physics, which constitutes an essential component of the field of wood science, building upon discoveries in wood chemistry, wood anatomy (xylem), and biology, as well as principles from classical physics, mechanics, and materials strength. [14] Wood physics encompasses critical research areas including: a) examining wood behaviour in ...
While OSB does not have a continuous grain like a natural wood, it does have greater strength on its long axis because more of the component grains are oriented in this direction. This can be seen by observing the alignment of the surface wood chips.
Grain size: increasing grain size decreases the amount of grain boundaries, which results in slower creep due to the high diffusion rate along grain boundaries. This is opposite low-temperature applications, where increasing grain size decreases strength by blocking dislocation motion.