Stress-Strain Diagram

Graph of stress as a function of strain. It can be constructed from data obtained in any mechanical test where load is applied to a material, and continuous measurements of stress and strain are made simultaneously. It is constructed for compression, tension and torsion tests.

Stress-Strain curve for a material such as mild steel.

The total area under the curve indicates how tough the material is - how much energy it can absorb while deforming plastically and not breaking.

The stress-strain curve for each material is different and unique. From these curves it is possible to extract a number of the materials properties.

Stress-Strain curves for different materials.

The stress-strain curve for concrete is nearly straight and then stops. This shows a brittle material. Cast iron is also a brittle material. The mild steel curve extends further and the material continues to strain (stretch if under tension) with the stress remaining relatively constant. This shows a high ductility.

See also: Strain, Stress, Stress-Strain Ratio, Tangent Modulus of Elasticity, Young′s Modulus.