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Fatigue (material) Fracture surface of an aluminium crank arm from a bicycle. The dark area (due to oil, dirt and fretting) is a slow growth fatigue crack and may contain striations. The bright area is caused by sudden fracture. Mechanical failure modes. Buckling.
Thermo-mechanical fatigue (short TMF) is the overlay of a cyclical mechanical loading, that leads to fatigue of a material, with a cyclical thermal loading. Thermo-mechanical fatigue is an important point that needs to be considered, when constructing turbine engines or gas turbines.
The tensile strength can be quoted as either true stress or engineering stress, but engineering stress is the most commonly used. Fatigue strength is a more complex measure of the strength of a material that considers several loading episodes in the service period of an object, [ 6 ] and is usually more difficult to assess than the static ...
For example; "fatigue or corrosion of a structural beam" or "fretting corrosion in an electrical contact" is a failure mechanism and in itself (likely) not a failure mode. The related failure mode (end state) is a "full fracture of structural beam" or "an open electrical contact".
Fatigue testing is a specialised form of mechanical testing that is performed by applying cyclic loading to a coupon or structure. These tests are used either to generate fatigue life and crack growth data, identify critical locations or demonstrate the safety of a structure that may be susceptible to fatigue.
Static fatigue. Static fatigue describes how prolonged and constant cyclic stress weakens a material until it breaks apart, which is called failure. [ 1] Static fatigue is sometimes called "delayed fracture". [ 2] The damage occurs at a lower stress level than the stress level needed to create a normal tensile fracture. [ 2]
Corrosion fatigue is fatigue in a corrosive environment. It is the mechanical degradation of a material under the joint action of corrosion and cyclic loading. Nearly all engineering structures experience some form of alternating stress, and are exposed to harmful environments during their service life. The environment plays a significant role ...
Low cycle fatigue (LCF) has two fundamental characteristics: plastic deformation in each cycle; and low cycle phenomenon, in which the materials have finite endurance for this type of load. The term cycle refers to repeated applications of stress that lead to eventual fatigue and failure; low-cycle pertains to a long period between applications.