Flow Laws
Each plastic deformation of a material can be described by a formula in which the strain rate depends on the differential stress (σ or σD), the grain size (d) and an activation value in the form of an Arrhenius equation:
In which A is the constant of diffusion, Q the activation energy of the mechanism, R the gas constant and T the absolute temperature (in kelvins). The exponents n and m are values for the sensitivity of the flow to stress and grain size respectively. The values of A, Q, n and m are different for each deformation mechanism. For diffusion creep, the value of n is usually around 1. The value for m can vary between 2 (Nabarro-Herring creep) and 3 (Coble creep). That means Coble creep is more sensitive to grain size of a material: materials with larger grains can deform less easily by Coble creep than materials with small grains.
Read more about this topic: Diffusion Creep
Famous quotes containing the words flow and/or laws:
“Flow, flow the waves hated,
Accursed, adored,
The waves of mutation:
No anchorage is.”
—Ralph Waldo Emerson (1803–1882)
“Nearest to all things is that power which fashions their being. Next to us the grandest laws are constantly being executed. Next to us is not the workman whom we have hired, with whom we love so well to talk, but the workman whose work we are.”
—Henry David Thoreau (1817–1862)