Toughness

Toughness or tenacity describes the resistance of a material to fracture or crack propagation.

Toughness is the energy consumption in connection with plastic deformation, which can be made visible by means of the load-displacement diagram. However, this is not directly from a definition of the concept of toughness can be derived, since in addition to quantify the fraction nominal voltage, the characteristics fracture deformation, fracture energy absorption and crack arrest assets are used to evaluate the toughness. This can lead to the rise in toughness in addition to improved fracture properties alternatively crack deflection or crack branching.

Typical examples of viscous materials are most metals. The opposite of the toughness is the brittleness. Examples of brittle materials are glass, ceramics, some plastics and hardened steel. These materials are very limited in their ability to deform plastically and thus can carry much less energy than tough materials before they break.

Temperature dependence

Some materials ( especially plastics and steel and all other body-centered cubic materials) show a pronounced temperature dependence of their toughness. The transition between tough " high altitude " and dryness " down position " is described by the transition temperature. The application temperature should always be above. Before this effect was known ships ( Liberty freighter during the Second World War, for example ) in a calm sea, but low temperatures are always brittle broken apart for no apparent reason.

Measurement methods

The parameters of toughness can be determined using different test procedures or methods of fracture mechanics. Thus, the fraction rated voltage and the fracture energy absorption by the Charpy impact test, Kerbzugversuch, penetration test or tensile test, the fracture deformation can be determined with the bending or folding test and the impact test. The crack arrest capacity is determined by the Charpy impact test or drop weight test.

Toughness classes

Tenacity of minerals

In mineralogy, the tenacity (toughness ) is a mineral surface with a steel needle certified Hardness:

• In brittle ( fragile ) Mineral dust from the surface of the Ritz jumps off. Most of the minerals belong to this category.
• During mild ( tendilem ) mineral powder does not jump off the Ritz, but remains lie at the edge of the scratch. Example: galena, stibnite
• In cuttable ( sektilem ) Mineral penetrating the needle creates a scratch track, but not the Ritz powder. Example: Talk, solid bismuth

The tenacity of the entire mineral is tested by bending:

• Brittle fracture minerals.
• Supple ( ductile / malle abel ) Minerals permanently change their shape. The shape change is plastically, that is, without breaking; e.g. can be hammered into a mineral flakes or drawn into a wire. Example: many metals ( silver, gold, copper, etc. ), argentite.
• Inelastic - flexible (flexible) minerals differ from the ductile minerals by the fact that the crystal can only be bent. Hammering or pulling would cause them to break. They remain after bending also in the new form. Example: plaster.
• The other hand, elastic- flexible ( elastic ) Minerals return after bending back their original shape. Example: biotite, muscovite, biotite mica

Strength of carbon fibers

Carbon fibers are classified according to seven degrees of their tensile strength: