The relationship between the stress and strain
that a particular material displays is known as that particular
material's Stress-Strain curve. It is unique for each material and is
found by recording the amount of deformation (strain) at distinct
intervals of tensile or compressive loading (stress). These curves
reveal many of the properties of a material (including data to establish
the Modules of Elasticity E)
Stress–strain curves of various materials vary widely, and different
tensile tests conducted on the same material yield different results,
depending upon the temperature of the specimen and the speed of the
loading. It is possible, however, to distinguish some common
characteristics among the stress-strain curves of various groups of
materials and, on this basis, to divide materials into two broad
categories; namely, the ductile materials and the brittle materials
stress applied to a material is the force per unit area applied to the
material. The maximum stress a material can stand before it breaks is
called the breaking stress or ultimate tensile stress.
Tensile means the material is under tension. The forces acting on it
are trying to stretch the material. Compression is when the forces
acting on an object are trying to squash it.
The equation below is used to calculate the stress.
stress = stress measured in Nm-2 or pascals (Pa)
F = force in newtons (N)
A = cross-sectional area in m2
The ratio of extension to original length is called strain it has no units as it is a ratio of two lengths measured in metres.
strain = strain it has no units
DL =extension measured in metres
L = original length measured in metres