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Creep, Creep resistance processes, How to reduce the creep, It is a…
Creep
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Why is creep important
creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses.
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At low temperatures and low stress, creep is essentially nonexistent and all strain is elastic
At low temperatures and high stress, materials experience plastic deformation rather than creep
example creep of a turbine blade could cause the blade to contact the casing, resulting in the failure of the blade.
Creep is significant when the room temperature is greater than 0.5times the melting point temperature of the material.
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While TUNGSTEN requires a temperature in the thousands of degrees before creep deformation can occur, LEAD may creep at room temperature, ICE will creep at temperatures below 0 °C (32 °F).
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How to reduce the creep
Control of the grain size and structure is also an effective method of reducing creep. Increasing the grain size by thermomechanical processes reduces the creep rate and extends the stress rupture life of metals by lowering the amount of grain boundary sliding
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It is a function of time
Creep is more severe in materials that are subjected to heat for long periods and generally increases as they near their melting point.
Creep deformation generally occurs when a material is stressed at a temperature near its melting point.
Unlike brittle fracture, creep deformation does not occur suddenly upon the application of stress. Instead, strain accumulates as a result of long-term stress. Therefore, creep is a "time-dependent" deformation.
It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material.
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