Definitions
Stress = load / area
Strain = deformation / gage length = &Delta L / Lo
Modulus of Elasticity, E = slope of intial linear part of the stress-strain curve
Proportional Limit Stress, &sigmapl = stress value at which the stress-strain curve goes nonlinear
Yield Point Stress, &sigmay = stress value at which the stress-strain curve goes horizontal (for many steels)
0.2%-Offset Yield Stress, &sigma0.2% y = the stress value at which a line drawn with slope E starting at 0.002 strain intersects the stress-strain curve
Ultimate Tensile Stress, &sigmault = largest stress on the stress-strain curve (top of the curve)
Engineering Fracture Stress = fracture load / original area
True Fracture Stress = fracture load / fracture area
Energy at Yield = area under the elastic portion of the load-deformation curve
Energy at Break = area under the entire load-deformation curve
Modulus of Resilience, Ur = area under the elastic portion of the stress-strain curve = &sigmapl2 / 2E = the amount of energy (or work) stored per unit volume at the elastic limit
Modulus of Toughness, Ut = area under the entire stress-strain curve = the amount of energy absorbed per unit volume at fracture -- a measure of the material ductility
Percent Elongation = (Lf - Lo) / Lo x 100%
Percent Elongation of 2" Gage Length = ΔL2 / 2" x 100%
- Percent Elongation of 8" Gage Length = &DeltaL8 / 8" x 100%
Percent Reduction in Area = (Af - Ao) / Ao x 100%