Strain rate is the rate of change in strain (deformation) of a material with respect to time.
The strain rate at some point within the material measures the rate at which the distances of adjacent parcels of the material change with time in the neighborhood of that point. It comprises both the rate at which the material is expanding or shrinking (expansion rate), and also the rate at which it is being deformed by progressive shearing without changing its volume (shear rate). It is zero if these distances do not change, as happens when all particles in some region are moving with the same velocity (same speed and direction) and/or rotating with the same angular velocity, as if that part of the medium were a rigid body.
The strain rate is a concept of materials science and continuum mechanics, that plays an essential role in the physics of fluids and deformable solids. In an isotropic Newtonian fluid, in particular, the viscous stress is a linear function of the rate of strain, defined by two coefficients, one relating to the expansion rate (the bulk viscosity coefficient) and one relating to the shear rate (the "ordinary" viscosity coefficient).
Read more about Strain Rate: Definition, See Also
Famous quotes containing the words strain and/or rate:
“O Master, let me walk with Thee
In lowly paths of service free;
Tell me Thy secret, help me bear
The strain of toil, the fret of care.”
—Washington Gladden (1836–1918)
“As a novelist, I cannot occupy myself with “characters,” or at any rate central ones, who lack panache, in one or another sense, who would be incapable of a major action or a major passion, or who have not a touch of the ambiguity, the ultimate unaccountability, the enlarging mistiness of persons “in history.” History, as more austerely I now know it, is not romantic. But I am.”
—Elizabeth Bowen (1899–1973)