Processing of Timber Flashcards Preview

Technology 3 - Building Science and Structures > Processing of Timber > Flashcards

Flashcards in Processing of Timber Deck (30):
1

What are the two processes of processing timber

- cutting into visible sizes
- maximise yeild

2

what is the definition of conversion

cutting of freshly felled timber into usable sizes

3

cutting of freshly felled timber into usable sizes refers to

Conversion

4

what will determine the orientation and distribution of cells in sawn timber

cutting process

5

plain sawing produces a high

yield... but it's properties differ from those of it's neighbours

6

True radial sawing produces planks with...

identical properties.... but involves a high waste rate

7

what are the two types of growth defect

shakes and knots

8

shakes and knots are types of

growth defect

9

shakes are...

splits in the timber

10

knots are formed when...

branches grew out of the trunk

11

wane is a defect from the ..... process

conversion

12

wane is....

the presence of bark on the outer edge of the plank and has aggressive grain slope.

13

what is seasoning

this is the controlled reduction in moisture content

14

the controlled reduction in moisture content is also known as

seasoning

15

what is the equation for moisture content in timber

wet - dry / dry x 100

16

freshly felled or green timber can have a moisture content of

150%

17

timber must be dried to have a moisture content below 20% to eliminate

fungal attack

18

timber that is stacked in open sided sheds and allowed to dry naturally is know as

air seasoning

19

timber that is heated to expel moisture is known as

kiln seasoning

20

what is the fibre saturation point

this is when water is removed from the cell cavities, and the only remaining water is that contained within the cell walls.

21

drying beyond the fibre saturation point will result in

shrinkage and changes in mechanical properties

22

too rapid drying of the surface layers can lead to the surface experiencing tensile forces which will result in

splits and checks

23

timber is a .... material

anisotropic

24

how does shrinkage occur in timber

tangential - radial - longitudinal

25

timber below the fibre saturation point is a ..... material

hygroscopic

26

a hygroscopic material can

absorb water from moist air and lose moisture to dry air

27

timber is not truly elastic in its response to stress, it is...

viscoelastic

28

what is viscoelastic

it simultaneously manifests the properties of an elastic solid and a viscous liquid.

29

viscoelasticity is property associated with creep, under static loading timber undergoes...

instantaneous elastic strain followed by time dependent strain.

30

what are the major limitations to timber

variability in properties
anistropy
limited size availability at reasonable cost