Thus, if, for instance, the object illustrated above contains
4 square inches of cross-sectional area, and the total load
it is called upon to endure is 10 tons, the stress would be
expressed as 2 1/2 tons.
STRAIN is the deformation produced by stress.
THE FACTOR OF SAFETY is usually expressed by the result
found by dividing the stress at which it is known the body
will collapse, by the maximum stress it will be called upon to
endure. For instance, if a control wire be called upon to endure
a maximum stress of 2 cwts., and the known stress at which
it will collapse is 10 cwts., the factor of safety is then 5.
[cwts. = centerweights = 100 pound units as in cent & century.
Interestinly enough, this word only exists today in abbreviation
form, probably of centreweights, but the dictionary entries, even
from a hundred years ago do not list this as a word, but do list
c. or C. as the previous popular abbreviation as in Roman Numerals]
The word listed is "hundredweight. Michael S. Hart, 1997]
COMPRESSION.--The simple stress of compression tends
to produce a crushing strain. Example: the interplane and
fuselage struts.
TENSION.--The simple stress of tension tends to produce
the strain of elongation. Example: all the wires.
BENDING.--The compound stress of bending is a combination
of compression and tension.
The above sketch illustrates a straight piece of wood of
which the top, centre, and bottom lines are of equal length.
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