PART I THE MECHANICAL PROPERTIES OF WOOD



INTRODUCTION


The mechanical properties of wood are its fitness and ability to
resist applied or external forces. By external force is meant
any force outside of a given piece of material which tends to
deform it in any manner. It is largely such properties that
determine the use of wood for structural and building purposes
and innumerable other uses of which furniture, vehicles,
implements, and tool handles are a few common examples.

Knowledge of these properties is obtained through
experimentation either in the employment of the wood in practice
or by means of special testing apparatus in the laboratory.
Owing to the wide range of variation in wood it is necessary
that a great number of tests be made and that so far as possible
all disturbing factors be eliminated. For comparison of
different kinds or sizes a standard method of testing is
necessary and the values must be expressed in some defined
units. For these reasons laboratory experiments if properly
conducted have many advantages over any other method.

One object of such investigation is to find unit values for
strength and stiffness, etc. These, because of the complex
structure of wood, cannot have a constant value which will be
exactly repeated in each test, even though no error be made. The