Modulus of Elasticity - Also known as Young's modulus; calculated by finding the slope of the stress-strain curve for a given material within the range of its linear proportionality between stress and strain.
Proportional Limit - The greatest stress a material can develop without deviating from linearity between stress and strain. Otherwise stated, the greatest stress developed in a material within its elastic range.
Percent Reduction in Area - The difference between the original and final cross-sectional areas of a test piece, expressed as a percentage.
Yield Point - Two critical points within the yield range for ductile materials are the upper yield point (UYP) and the lower yield point (LYP), which are used to characterise the plastic range of a material.
Yield Strength - The stress at which a material exhibits a specified limiting permanent set.