Stress–strain curve

A stress-strain curve is a graph that is used to describe the relationship between stress and strain of a specific material. Stress is captured on the y-axis while strain is on the x-axis. Stress is the amount of force needed to change the material's shape: in this case, to make it longer. Strain is a measurement of how much the shape changes.

This graph is usually made by testing a material with a tensile test. A force, of varying amounts, is used to pull the sample apart at a constant rate until it breaks. This graph is used to show important characteristics of a material such as the yield strength, ultimate strength, fracture point, strain hardening, necking, and Young's modulus.

 Yield strength - point after which permanent, un-fixable damage occurs (think of overstretching a rubber band and now it's larger than it was originally)
 Ultimate strength - strongest recorded measurement of the material, also known as maximum stress
 Fracture point - point at which the material breaks
 Strain hardening - area where the material becomes stronger but is undergoing permanent, un-fixable damage
 Necking - region on graph where the material is past its ultimate strength and where the material is becoming smaller in area at the location where it breaks
 Young's modulus - the slope of the stress-strain curve before the yield strength point, used to describe "plastic" deformation. That is damage to the material that can be completely reversed (think of stretching a rubber band and returning it back to place and it's back to its original size)

Related pages
 Strength of materials

Tension (mechanics)
 Elastomers
 Plane strain compression test
 Stress–strain index
 Tensometer
 Universal testing machine

Category:Elasticity (physics)