Nominal Strain Definition

Strain is the deformation in a metal when forces are applied.

Nominal strain, also known as engineering strain and Cauchy strain, is the total deformation in a single plane when forces are constantly being applied to the plane within the object being tested for deformation.

Measurement

Nominal strain can be measured by dividing the dead load (force applied to a structure that is present at all times) by "l," which is the length of the plane after pressure is applied minus the original length of the plane. This gives a two-dimensional representation of the problem.

Relationship to True Strain

Engineering strain only measures a small amount of strain and is inaccurate when the deformation is no longer small (usually about 5 percent). In these cases, individuals should attempt to calculate the true strain for a more accurate answer. Equations for true strain can be found in Resources.

Relationship to Stress

Stress is the force applied to an area. Stress interacts with the nominal strain in Hooke's Law, which determines the elasticity of metals by dividing the stress on a plane to its strain under that stress. This elasticity is expressed in pounds per square inch.

References

• Efunda: Strain
• Engineering.com: Stress/Strain Relationship
• The Engineering Toolbox: Stress, Strain, and Young's Modulus
• Key to Metals: Engineering Stress-Strain Curve

Resources

• DRD Technology: Engineering Strain Vs. True Strain