# Strain rate Definition and 16 Threads

Strain rate is the 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). In solids, higher strain rates can often cause normally ductile materials to fail in a brittle manner.

View More On Wikipedia.org
1. ### Micromechanics of High Strain Rate Loaded Composite Media

I would like to know some guidelines regarding this topic. The characteristics of wave propagation depend highly on the orientation of fibre (unidirectional and warp & weft arrangement), fibre volumetric fraction, relative fibre modulli etc. What is the relation of wave propagation and these...
2. ### Streamlines from strain rate tensor

I was reading about strain rate tensors and other kinematic properties of fluids that can be obtained if we know the velocity field V = (u, v, w). It got me wondering if I can sketch streamlines if I have the strain rate tensor with me to start with. Let's say I have the strain rate tensor...
3. ### Does strain rate ever decrease yield stress?

I've been digging through literature the last few days, and I'm starting to wonder if increasing strain rate EVER decreases yield stress? I found anomalies which increase it with increasing temperature. But I cant' find the reverse, so I was wondering if it was possible?
4. ### I What is physicial interpretation of deviatoric strain rate

How these properties are related to velocity fluid. The https://postimg.org/image/674a6sw4t/ https://postimg.org/image/674a6sw4t/ figure shows an area of Earth's mantle where upwelling of hot semi-liquid mantle is occurring in middle and then two downwelling currents on two sides (forming...
5. ### Piezoelectric strain rate and frequency of applied voltage

If one were to apply, for example, 60 Hz AC to a piezoelectric material, would the strain rate be 60 Hz? I am not entirely sure if I am using "strain rate" in its proper sense; I use it merely to describe what I imagine would be the rate at which the material expands and contracts while exposed...
6. ### Difference between Creep and Strain Rate Sensitivity

Hello, recently I became interested in some basics of material science and there was one thing that I did not really understand. What is the difference (or what are things in common) between creep and strain rate sensitivity? I read about it in connection with indentation. - To measure the...
7. ### High strain rate testing using the SHPB -- Help please

I am a part C mechanical engineering student and require some advice for my individual project, which is based on the high strain-rate testing of a particular glass filled composite material using a split-Hopkinson pressure bar (SHPB) experiment. I gathered the results on a SHPB test rig and...
8. ### Can Higher Strain Rates Be Modeled from Existing Stress/Strain Curves?

I want to create stress/strain curves for Higher Strain Rates from an available stress/strain curve? I am interested on the mathematical formulation aspect to generate a Dyna Material card.
9. ### Longitudinal strain rate derivation

Hi, The attachment below is about strain rate in fluids*. It shows how the strain rate d\phi/dt is related to the velocity field derivative du/dx when you stretch the element in x (i.e. longitudinal strain). It has no intermediate steps, and I can't see how the angle has been related to...
10. ### Determine the strain rate for a material fiber

Homework Statement Determine the Strain Rate for a Material Fiber in the direction of the surface normal. The Velocity Field is V=((4y-3x)i+(5x+3y)j) ft/s http://puu.sh/9hQ7Q/2bda80620f.jpg is the picture which describes a steady, planar flow where i and j are unit vectors. Homework...
11. ### Independency of the frame of reference of the strain rate tensor

I've got a problem regarding tensors. Premise: we are considering a fluid particle with a velocity \mathbf{u} and a position vector \mathbf{x}; S_{ij} is the strain rate tensor, defined in this way: \displaystyle{S_{ij}=\frac{1}{2}\left(\frac{\partial u_i}{\partial x_j} +\frac{\partial...
12. ### Axial stress rate vs axial strain rate

Homework Statement I have a Mohr-Coulomb plasticity model with isotropic hardening on the cohesion c(k). The angle of internal friction is constant. k=sqrt((2/3)*(de)'Q*de), where de is the time derivative of the plastic strain. Q is diag[1,1,1,0.5,0.5,0.5]. It is a triaxial test assuming...
13. ### No strain rate dependency- then?

i, I'm attaching a file which have the stress strain curves of same material at quasi static and high strain rates. See materials on page 1 and page 2. Both are same materials. The curve on page 1 is obtained at quasi static strain rate and the curve on page 2 is obtained at high...
14. ### Effect of High Strain Rate on strength of Metal

What is the main reason for changing the strength of metals under very high strain rate? Do all metals show the similar trend in increased strength under high strain rate? What is the effect of crystal structure on this phenomenon?:!)
15. ### What is the difference between strain rate and velocity gradient?

What is the difference between strain rate and velocity gradient of a Newtonian fluid?
16. ### Strain rate effects on steel strength

I was wondering exactly how yield and tensile strength increases with increasing levels of strain rate for a typical steel grade? I understand dislocations are generated during straining (work hardening), but what happens at higher strain rates which increases the strength?