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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]
It is useful in expressing S-N relationships. It is a fundamental principle in materials science that describes the relationship between the stress amplitude experienced by a material and its fatigue life under cyclic loading conditions. The law is named after American scientist O. H. Basquin, who introduced the law in 1910.
Common factors that have been attributed to low-cycle fatigue (LCF) are high stress levels and a low number of cycles to failure. Many studies have been carried out, particularly in the last 50 years on metals and the relationship between temperature, stress, and number of cycles to failure.
Being a power law relationship between the crack growth rate during cyclic loading and the range of the stress intensity factor, the Paris–Erdogan equation can be visualized as a straight line on a log-log plot, where the x-axis is denoted by the range of the stress intensity factor and the y-axis is denoted by the crack growth rate.
The rule, variously called Miner's rule or the Palmgren–Miner linear damage hypothesis, states that where there are k different stress magnitudes in a spectrum, S i (1 ≤ i ≤ k), each contributing n i (S i) cycles, then if N i (S i) is the number of cycles to failure of a constant stress reversal S i (determined by uni-axial fatigue tests ...
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 ...
The flow stress is an important parameter in the fatigue failure of ductile materials. Fatigue failure is caused by crack propagation in materials under a varying load, typically a cyclically varying load. The rate of crack propagation is inversely proportional to the flow stress of the material.