III. Translate the following sentences into Ukrainian.

1. Fungi need food, air, suitable temperature, and suitable moisture content.

2. Cross grain is the deviation of wood fibres from a direction parallel to

the longitudinal axis of a piece of wood.

3. Rotten knots are softer than the surrounding wood.

4. Pitch pocket is a well-defined opening between the growth rings.

5. Generally compression wood has high longitudinal shrinkage and low

stiffness.

6. Shakes encourage horizontal shear failures and seriously affect strength.

7. Discoloured streaks have little effect on the strength of the wood.

IV. Read and translate the text. Defects in Wood

Every tree is a prey to defects from the moment it emerges as a seedling to the last stages of seasoning . Wood defects are classified as natural and artificial.

Natural defects of wood are decay, cross grain, knots, compression wood, insect holes, pitch pockets, shake and mineral streaks.

Decay. Decay is caused by organisms known as fungi. Fungi need food, air, suitable temperature, and suitable moisture content. Wood with moisture content less than about 20 per cent will not decay owing to the lack of sufficient moisture for fungi development. Wood under water will not decay because the air supply of fungi is lacking. Decay affects shock resistance.

Cross Grain. This term denotes the deviation of wood fibres from a direction parallel to the longitudinal axis of a piece of wood. Subtypes include diagonal, spiral, and irregular grain.

Knots. A knot is that part of a branch included in the bole of a tree. Knots are classed according to size, shape, and quality. Pin knots are less than 12 mm in diameter. Standard knots are from 12 mm to 36 mm in diameter. Large knots are more than 36 mm in diameter. Sound knots are as hard as the surrounding wood and their fibers are intergrown with it. Rotten knots are softer than the surrounding wood.

Checks are cracks or splits which run across the rings and usually appear at the

ends of a board. Splits are cracks which tend to run along the length of the board.

Stain is a discolouration of the wood. Blue stain is common in white pine.

Compression Wood. This is abnormal growth which occurs on the under side of leaning trees and limbs of softwoods. It is denser and harder than other wood. Compression wood is characterized by wide, eccentric annual rings, little contrast between spring and summerwood, and is more or less dark-reddish to brown in colour. Generally compression wood has high longitudinal shrinkage compared with normal wood. It also has low stiffness.

Insect Holes. Occasional wormholes don’t seriously weaken wood. Numerous holes have a somewhat similar effect as knots, except that grain distortion is not involved. Such holes are classified as pin holes, grub holes, etc.

Pitch Pocket. This is a well-defined opening between the growth rings. It contains

resin and is characteristic of the wood of certain conifers such as pines, spruces, etc. A large number of pitch pockets may affect strength and can indicate shake in the wood.

Shake. This is separation of wood along the grain, primarily between or within annual rings. In beams, shakes encourage horizontal shear failures and seriously affect strength.

Mineral Streaks. They look like bird pecks or holes. Discoloured streaks are caused by oxidation or other chemical changes in the wood; they may damage its appearance, but they have little effect on the strength of the wood.

The artificial wood defects are crooks, bows, cups, twists, warps, etc.

Crook is a longitudinal curvature of the edge. Bow is a longitudinal curvature of the face. Cup is a curvature across the grain. Twist is a winding or turning of the edges of a board.