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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 ...
A two-dimensional flow that, at the highlighted point, has only a strain rate component, with no mean velocity or rotational component. In continuum mechanics, the strain-rate tensor or rate-of-strain tensor is a physical quantity that describes the rate of change of the strain (i.e., the relative deformation) of a material in the neighborhood of a certain point, at a certain moment of time.
A shearing force is applied to the top of the rectangle while the bottom is held in place. The resulting shear stress, τ, deforms the rectangle into a parallelogram. The area involved would be the top of the parallelogram. Shear stress (often denoted by τ, Greek: tau) is the component of stress coplanar with a material cross section.
The shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary (Couette flow), is defined by. where: γ ˙ {\displaystyle {\dot {\gamma }}} is the shear rate, measured in reciprocal seconds; v is the velocity of the moving plate, measured in meters per second; h is the distance ...
The volumetric strain, also called bulk strain, is the relative variation of the volume, as arising from dilation or compression; it is the first strain invariant or trace of the tensor: = = = + + Actually, if we consider a cube with an edge length a, it is a quasi-cube after the deformation (the variations of the angles do not change the ...
For a Newtonian fluid, the stress exerted by the fluid in resistance to the shear is proportional to the strain rate or shear rate. A simple example of a shear flow is Couette flow, in which a fluid is trapped between two large parallel plates, and one plate is moved with some relative velocity to the other. Here, the strain rate is simply the ...
In engineering and materials science, a stress–strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupon and measuring the deformation, from which the stress and strain can be determined (see tensile testing). These curves reveal many of the properties of a ...
The figure also shows the effect of increased strain rate generally increasing the critical resolved shear stress for a constant temperature as this increases the dislocation density in the material. Note that for intermediate temperatures, i.e. region II, there is a region where the strain rate has no effect on the stress.