Mechanical Properties

Stress, Strain, and Elastic Constants

· The diagram shows the effect of applying a uniaxial tensile (a) or compressive (b) force, F, to a cylindrical sample that stays in the elastic response range.
· Nominal or Engineering Stress and Strain for the samples are defined in terms of a normalization with respect to the initial sample dimensions.
Engineering Stress:
σ_N = (Force/ Initial Area) = (F/A₀)
Engineering Strain:
ε _N = (Change in Length/Initial Length)
= (ΔL/L₀)

From: Callister, "Materials Science and Engineering," Wiley (1994)