Glossary

Definitions

During the course of this lab, you will be introduced to and use the following terms. You will need to know the meaning of these terms in order to understand the tests. These terms are used by many types of engineers - all the time.

Compression

This, as you would expect, describes a "squeezing" action or force on an object.

Tension

The opposite of compression, or a "stretching" action or force on an object.

Stress

A measure of force per unit of area, i.e. lb./in2 (or psi), kN/m2

Strain

A measure of deformation or elongation of a material, its units are inch per inch; it is the ratio of a change in length to the original length of a specimen.

Strength

The stress value at which a sample of material fails.

Modulus of elasticity

Relates stress to strain and visa versa. It is the ratio of the stress on a sample to the amount of stain that level of stress causes. It is also the slope of the straight line portion of the stress-strain curve for a specific material.

Elastic range

The portion of the stress-strain relationship for a material where if the specimen loaded and then unloaded, it will return to its original undeformed shape. The straight line portion of the stress strain curve.

Neutral axis

A line which runs along the length of a beam where stress and strain are equal to zero.

Moment of inertia

< This is one measure of the stiffness of a beam. It relates cross sectional area and the distance from the neutral axis at which the majority of the area is located to the ease in which the beam is bent. Example: An "I" beam has a greater moment of inertia than a flat plate of the exact same cross sectional area.

Cantilever Beam

A beam (a member whose main action is bending) supported, or fixed, at only one end. i.e. an overhang or a diving board configuration.