engineeringstress

Engineering stress is the stress experienced by a material under uniaxial loading, defined as the applied force divided by the original cross-sectional area: sigma_eng = F / A0. It is a standard parameter in materials testing and engineering design because it provides a simple basis for comparing materials and components using their initial dimensions.

Engineering stress is typically considered alongside engineering strain, defined as the change in length divided by the original length. In the elastic region, the relationship is approximately linear and described by Hooke's law: sigma_eng = E * epsilon_eng, where E is the modulus of elasticity. From the stress–strain curve, engineers identify yield strength, ultimate tensile strength, and the onset of plastic deformation.

Engineering stress assumes a constant cross-section equal to A0, which is valid for small strains. Beyond the yield point in ductile materials, necking causes the actual cross-section to decrease, and engineering stress no longer tracks the true material resistance. True stress, which uses the instantaneous area, provides a more accurate measure in large deformations.

Engineering stress remains widely used in design codes and standard tensile tests due to its simplicity. It is expressed in units of pressure, typically megapascals (MPa) or gigapascals (GPa).