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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.
Diffusional flow can be further broken down into more specific mechanisms: Nabarro–Herring creep, Coble creep, and Harper–Dorn creep. [14] While most materials will exhibit Nabarro-Herring creep and Coble creep, Harper-Dorn creep is quite rare, [20] [21] having only been reported in a select few materials at low stresses including aluminium ...
Source: [6] can be obtained by accelerated creep test in which strain is recirded, interpolating the data (,) (˙) = ˙ + (˙) When adopting the Omega Method for a remaining life assessment, it is sufficient to estimate the creep strain rate at the service stress and temperature by conducting creep tests on the material that has been exposed to service conditions.
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 ...
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.
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 ...
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 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 ]