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In materials science, creep (sometimes called cold flow) is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses.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.
F.R. Larson and J. Miller proposed that creep rate could adequately be described by the Arrhenius type equation: = / Where r is the creep process rate, A is a constant, R is the universal gas constant, T is the absolute temperature, and is the activation energy for the creep process.
In continuum mechanics, ratcheting, or ratchetting, also known as cyclic creep, is a behavior in which plastic deformation accumulates due to cyclic mechanical or thermal stress. [ 1 ] [ 2 ]
A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations.
In materials science, Coble creep, a form of diffusion creep, is a mechanism for deformation of crystalline solids. Contrasted with other diffusional creep mechanisms, Coble creep is similar to Nabarro–Herring creep in that it is dominant at lower stress levels and higher temperatures than creep mechanisms utilizing dislocation glide. [ 1 ]
In materials science, Nabarro–Herring creep (NH creep) is a mechanism of deformation of crystalline materials (and amorphous materials [1]) that occurs at low stresses and held at elevated temperatures in fine-grained materials. In Nabarro–Herring creep, atoms diffuse through the crystals, and the rate of creep varies inversely with the ...
In materials that were deformed under very high temperatures, lobate grain boundaries may be taken as evidence for diffusion creep. [7] Diffusion creep is a mechanism by which the volume of the crystals can increase. Larger grain sizes can be a sign that diffusion creep was more effective in a crystalline material.
Creep increases with temperature and it is more common when a material is exposed to high temperatures for a long time or at the melting point of the material. Creep machines are used to understand the creep of materials and determine which type can do the job better, which is important when making and designing materials for everyday uses.