Search results
Results from the WOW.Com Content Network
Fatigue has traditionally been associated with the failure of metal components which led to the term metal fatigue. In the nineteenth century, the sudden failing of metal railway axles was thought to be caused by the metal crystallising because of the brittle appearance of the fracture surface, but this has since been disproved. [ 1 ]
Tear bands are approximately parallel to the direction of crack growth and produce what is known as a river pattern, so called, because it looks like the diverging pattern seen with river flows. The source of the river pattern converges to a single point that is typically the origin of the fatigue failure.
PSB structure (adopted from [7]). Persistent slip-bands (PSBs) are associated with strain localisation due to fatigue in metals and cracking on the same plane. Transmission electron microscopy (TEM) and three-dimensional discrete dislocation dynamics (DDD [8]) simulation were used to reveal and understand dislocations type and arrangement/patterns to relate it to the sub-surface structure.
A Griffith crack (flaw) of length is in the middle [3] [4] an infinity large material. Fracture mechanics was developed during World War I by English aeronautical engineer A. A. Griffith – thus the term Griffith crack – to explain the failure of brittle materials. [5] Griffith's work was motivated by two contradictory facts:
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.
Fretting decreases fatigue strength of materials operating under cycling stress. This can result in fretting fatigue, whereby fatigue cracks can initiate in the fretting zone. Afterwards, the crack propagates into the material. Lap joints, common on airframe surfaces, are a prime location for fretting corrosion.
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 ...
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 .