# Dictionary Definition

toughness

### Noun

1 enduring strength and energy [syn: stamina, staying power]
2 the property of being big and strong [syn: huskiness, ruggedness]
3 the elasticity and hardness of a metal object; its ability to absorb considerable energy before cracking [syn: temper]
4 impressive difficulty [syn: formidability]

# User Contributed Dictionary

## English

### Noun

1. the state of being tough and strong (withstanding force)
2. In the context of "of a metal": the resistance to fracture when stressed
3. formidable difficulty

# Extensive Definition

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.

## Mathematical definition

Toughness can be found by taking the area (i.e., by taking the integral) underneath the stress-strain curve. The explicit mathematical description is:
\frac \mbox \mbox = \int_^ \sigma\, d\epsilon
Where
• \epsilon is strain
• \epsilon_f is the strain upon failure
• \sigma is stress
Another definition is the ability to absorb mechanical (or kinetic) energy up to failure.

## Toughness tests

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.

toughness in German: Zähigkeit