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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 ...
Vickers hardness test; Brinell scale This page was last edited on 16 November 2024, at 12:16 (UTC). Text is available under the Creative Commons ...
Female alder catkins after shedding their seeds Alnus serrulata male catkins. Alders are trees of the genus Alnus in the birch family Betulaceae.The genus includes about 35 species [2] of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.
The leaves of this tree are sticky and if they are spread on the floor of a room, their adhesive surface is said to trap fleas. [ 32 ] Chemical constituents of Alnus glutinosa include hirsutanonol , oregonin , genkwanin , [ 36 ] rhododendrin {3-(4-hydroxyphenyl)-l-methylpropyl-β-D-glucopyranoside} and ( penta-2,3-dienedioic acid ).
Lignum vitae is hard and durable, and is also the densest wood traded (average dried density: ~79 lb/ft 3 or ~1,260 kg/m 3); [4] it will easily sink in water. On the Janka scale of hardness, which measures hardness of woods, lignum vitae ranks highest of the trade woods, with a Janka hardness of 4,390 lbf (compared with Olneya at 3,260 lbf, [5] African blackwood at 2,940 lbf, hickory at 1,820 ...
[5] [6] [7] Balsa is the softest wood ever measured using the Janka hardness test (22 to 167 lbf). [8] The wood of the living tree has large cells that are filled with water. This gives the wood a spongy texture. It also makes the wood of the living tree not much lighter than water and barely able to float. For commercial production, the wood ...
The midge sometimes creates a separate, tubular gall on the midrib or veins of the undersides of the leaves. [23] The cottony maple leaf scale, Pulvinaria acericola, occurs on the foliage of Acer negundo. [23] A leaf spot fungus, Septoria negundinis creates black-ringed lesions on the leaves. [23]
The hardest hardwoods are much harder than any softwood, [4] but in both groups there is enormous variation with the range of wood hardness of the two groups overlapping. For example, balsa wood, which is a hardwood, is softer than most softwoods, whereas the longleaf pine, Douglas fir, and yew softwoods are much harder than several hardwoods.