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Macroscopic and microscopic discontinuities (at the crystalline grain scale) as well as component design features which cause stress concentrations (holes, keyways, sharp changes of load direction etc.) are common locations at which the fatigue process begins. Fatigue is a process that has a degree of randomness , often showing considerable ...
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 ]
In mechanical design, most failures are due to time-varying, or dynamic, loads that are applied to a system. This phenomenon is known as fatigue failure. Fatigue is known as the weakness in a material due to variations of stress that are repeatedly applied to said material. [8]
Basquin's law of fatigue states that the lifetime of the system has a power-law dependence on the external load amplitude, , where the exponent has a strong material dependence. [1] It is useful in expressing S-N relationships .
Within the branch of materials science known as material failure theory, the Goodman relation (also called a Goodman diagram, a Goodman-Haigh diagram, a Haigh diagram or a Haigh-Soderberg diagram) is an equation used to quantify the interaction of mean and alternating stresses on the fatigue life of a material. [1]
ε f ' is an empirical constant known as the fatigue ductility coefficient defined by the strain intercept at 2N =1; c is an empirical constant known as the fatigue ductility exponent, commonly ranging from -0.5 to -0.7. Small c results in long fatigue life. ς f ' is a constant known as the fatigue strength coefficient
In true corrosion fatigue, the fatigue-crack-growth rate is enhanced by corrosion; this effect is seen in all three regions of the fatigue-crack growth-rate diagram. The diagram on the left is a schematic of crack-growth rate under true corrosion fatigue; the curve shifts to a lower stress-intensity-factor range in the corrosive environment.
The fatigue limit or endurance limit is the stress level below which an infinite number of loading cycles can be applied to a material without causing fatigue failure. [1] Some metals such as ferrous alloys and titanium alloys have a distinct limit, [ 2 ] whereas others such as aluminium and copper do not and will eventually fail even from ...