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Quench cracking, or crack growth following a quenching process, is another example of intergranular fracture and almost always occurs by intergranular processes. [6] This process of quench cracking is promoted by weakened grain boundaries and large grain sizes and additionally influenced by the temperature gradient at which quenching occurs and ...
Historically, fatigue has been separated into regions of high cycle fatigue that require more than 10 4 cycles to failure where stress is low and primarily elastic and low cycle fatigue where there is significant plasticity. Experiments have shown that low cycle fatigue is also crack growth. [4]
Crack closure is a phenomenon in fatigue loading, where the opposing faces of a crack remain in contact even with an external load acting on the material. As the load is increased, a critical value will be reached at which time the crack becomes open .
Schematic of typical fatigue-crack-growth behavior. In normal fatigue-testing of smooth specimens, about 90 percent is spent in crack nucleation and only the remaining 10 percent in crack propagation. However, in corrosion fatigue crack nucleation is facilitated by corrosion; typically, about 10 percent of life is sufficient for this stage.
It is the result of the process of fatigue due to rolling/sliding contact. [2] [3] The RCF process begins with cyclic loading of the material, which results in fatigue damage that can be observed in crack-like flaws, like white etching cracks. [2] These flaws can grow into larger cracks under further loading, potentially leading to fractures ...
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.
A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads. The growth of a fatigue crack can result in catastrophic failure, particularly in the case of aircraft. When many growing fatigue cracks interact with one another it is known as widespread fatigue damage. A crack growth equation can be used to ...
Another way of measuring crack growth is to mark the specimen with heat tinting or fatigue cracking. The specimen is eventually broken apart and the crack extension is measured with the help of the marks. The test thus performed yields several load vs crack mouth opening displacement (CMOD) curves, which are used to calculate J as following:-