Toughness
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In
Toughness and strength
Toughness is related to the area under the stress–strain curve. In order to be tough, a material must be both strong and ductile. 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. To be tough, a material should withstand both high stresses and high strains. Generally speaking, strength indicates how much force the material can support, while toughness indicates how much energy a material can absorb before rupturing.
Mathematical definition
Toughness can be determined by
where
- is strain
- is the strain upon failure
- is stress
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. Mathematically, the modulus of resilience can be expressed by the product of the square of the yield stress divided by two times the Young's modulus of elasticity. That is,
Toughness tests
The toughness of a material can be measured using a small specimen of that material. A typical testing machine uses a pendulum to deform a notched specimen of defined cross-section. The height from which the pendulum fell, minus the height to which it rose after deforming the specimen, multiplied by the weight of the pendulum, is a measure of the energy absorbed by the specimen as it was deformed during the
Unit of toughness
Tensile toughness (or deformation energy, UT) is measured in units of
- 1.00 N·m.m−3 ≃ 0.000145 in·lbf·in−3
- 1.00 in·lbf·in−3 ≃ 6.89 kN·m.m−3.
In the
- UT = Area underneath the stress–strain (σ–ε) curve = σ × ε
- UT [=] F/A × ΔL/L = (N·m−2)·(unitless)
- UT [=] N·m·m−3
- UT [=] J·m−3
Toughest material
An alloy made of almost equal amounts of chromium, cobalt and nickel (CrCoNi) is the toughest material discovered thus far. It resists fracturing even at incredibly cold temperatures close to absolute zero. It is being considered as a material used in building spacecraft.[5]
See also
References
- ^ a b c "Toughness", NDT Education Resource Center, Brian Larson, editor, 2001–2011, The Collaboration for NDT Education, Iowa State University
- )
- OCLC 300921090.
- ISSN 1548-0569.
- ^ Sparkes, Matthew (14 December 2022). "Toughest material ever is an alloy of chromium, cobalt and nickel". New Scientist. Retrieved 18 March 2023.