Toughness

For example, brittle materials (like ceramics) that are strong but with limited ductility are not tough; conversely, very ductile materials with low strengths are also not tough.

[1] It is the energy of mechanical deformation per unit volume prior to fracture.

where If the upper limit of integration up to the yield point is restricted, the energy absorbed per unit volume is known as the modulus of resilience.

A typical testing machine uses a pendulum to deform a notched specimen of defined cross-section.

Tensile toughness (or deformation energy, UT) is measured in units of joule per cubic metre (J·m−3), or equivalently newton-metre per cubic metre (N·m·m−3), in the SI system and inch-pound-force per cubic inch (in·lbf·in−3) in US customary units: In the SI system, the unit of tensile toughness can be easily calculated by using area underneath the stress–strain (σ–ε) curve, which gives tensile toughness value, as given below:[4] An alloy made of almost equal amounts of chromium, cobalt and nickel (CrCoNi) is the toughest material discovered thus far.

[5] It resists fracturing even at incredibly cold temperatures close to absolute zero.