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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.
Primary Creep: the initial creep stage where the slope is rising rapidly at first in a short amount of time. After a certain amount of time has elapsed, the slope will begin to slowly decrease from its initial rise. Steady State Creep: the creep rate is constant so the line on the curve shows a straight line that is a steady rate.
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.
L. M. Kachanov [5] and Y. N. Rabotnov [6] suggested the following evolution equations for the creep strain ε and a lumped damage state variable ω: ˙ = ˙ ˙ = ˙ where ˙ is the creep strain rate, ˙ is the creep-rate multiplier, is the applied stress, is the creep stress exponent of the material of interest, ˙ is the rate of damage accumulation, ˙ is the damage-rate multiplier, and is ...
Alternative material models have been proposed to simulate ratcheting, such as Chaboche, Ohno-Wang, Armstrong–Frederick, etc. [6] Ratcheting is a significant effect to be considered to check permanent deformation in systems which undergoes a cyclic loading.
Grain boundary sliding (GBS) is a material deformation mechanism where grains slide against each other. This occurs in polycrystalline material under external stress at high homologous temperature (above ~0.4 [1]) and low strain rate and is intertwined with creep. Homologous temperature describes the operating temperature relative to the ...
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 ...
For some materials, e.g. elastomers and polymers, subjected to large deformations, the engineering definition of strain is not applicable, e.g. typical engineering strains greater than 1%, [1] thus other more complex definitions of strain are required, such as stretch, logarithmic strain, Green strain, and Almansi strain.