Toughness, in materials science and metallurgy, is the resistance to fracture of a material when stressed. It is defined as the amount of energy per volume that a material can absorb before rupturing.
Toughness can be found by taking the area (i.e., by taking the integral) underneath the stress-strain curve
. The explicit mathematical description is:
- is strain
- is the strain upon failure
- is stress
Another definition is the ability to absorb mechanical (or kinetic) energy up to failure.
Tests can be done by using a pendulum and some basic physics to measure how much energy it will hold when released from a particular height. By having a sample at the bottom of its swing a measure of toughness can be found, as in the Charpy
and Izod impact tests
Unit of toughness
Toughness is measured in units of joules
per cubic metre
(J/m³) in the SI
system and inch-pound-force
per cubic inch
(in·lbf/in³) in US customary units