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With body-centered cubic materials (bcc), the Wöhler curve often becomes a horizontal line with decreasing stress amplitude, i.e. there is a fatigue strength that can be assigned to these materials. With face-centered cubic metals (fcc), the Wöhler curve generally drops continuously, so that only a fatigue limit can be assigned to these ...
Vibration fatigue is a mechanical engineering term describing material fatigue, caused by forced vibration of random nature. An excited structure responds according to its natural-dynamics modes, which results in a dynamic stress load in the material points. [ 1 ]
Metallurgical failure analysis is the process to determine the mechanism that has caused a metal component to fail.It can identify the cause of failure, providing insight into the root cause and potential solutions to prevent similar failures in the future, as well as culpability, which is important in legal cases. [1]
An impact load is one whose time of application on a material is less than one-third of the natural period of vibration of that material. Cyclic loads on a structure can lead to fatigue damage, cumulative damage, or failure. These loads can be repeated loadings on a structure or can be due to vibration.
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.
There are three mechanisms acting in thermo-mechanical fatigue Creep is the flow of material at high temperatures; Fatigue is crack growth and propagation due to repeated loading; Oxidation is a change in the chemical composition of the material due to environmental factors. The oxidized material is more brittle and prone to crack creation.
Variable amplitude loads produce striations of different widths and the study of these striation patterns has been used to understand fatigue. [ 6 ] [ 7 ] Although various cycle counting methods can be used to extract the equivalent constant amplitude cycles from a variable amplitude sequence, the striation pattern differs from the cycles ...
Curve A shows the fatigue behavior of a material tested in air. A fatigue threshold (or limit) is seen in curve A, corresponding to the horizontal part of the curve. Curves B and C represent the fatigue behavior of the same material in two corrosive environments. In curve B, the fatigue failure at high stress levels is retarded, and the fatigue ...