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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]
A constant fatigue life (CFL) diagram [34] is useful for the study of stress ratio effect. The Goodman line is a method used to estimate the influence of the mean stress on the fatigue strength. A Constant Fatigue Life (CFL) diagram is useful for stress ratio effect on S-N curve. [35]
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 .
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
This simplification allows the number of cycles until failure of a component to be determined for each rainflow cycle using either Miner's rule to calculate the fatigue damage, or in a crack growth equation to calculate the crack increments. [2] Both methods give an estimate of the fatigue life of a component.
Animation showing a series of crack orientations, each of which is evaluated for fatigue life during Critical plane analysis The chief advantage of critical plane analysis over earlier approaches like Sines rule , or like correlation against maximum principal stress or strain energy density , is the ability to account for damage on specific ...
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 ...
Material failure theory is an interdisciplinary field of materials science and solid mechanics which attempts to predict the conditions under which solid materials fail under the action of external loads. The failure of a material is usually classified into brittle failure or ductile failure .