What is considered a high strain rate?
The velocity of waves and the size of the test piece determine the upper limit of strain rate for accurate measurement of stress–strain curves. At very high strain rate (beginning at about 104 or 105 s−1), shock wave propagation becomes critical.
What is high strain rate deformation?
Deformation at higher rates (a) produces more uniform dislocation distributions for the same amount of strain, (b) hinders the formation of discrete dislocation cells, (c) decreases cell size, and (d) increases misorientation, with more dislocations trapped within cell interiors.
What does a higher strain mean?
A simplified explanation is that when a material is loaded at very high strain rates, the stress/strain travels faster than the cracks in the material and they encounter solid, un-cracked material which displays higher resistance to the stresses and hence higher strength.
What are strain rate effects?
Strain rate effect is the basic property of solid materials while strain rate effect of nonuniform materials is more obvious than that of uniform materials. Concrete strength is highly sensitive to the process of loading.
How do you increase strain rate?
Shear strain rate is dependent on shear stress. When temperature increases from T1 to T2, shear strain rate increases for a given shear stress. Similarly, the application of a higher shear stress will increase the shear strain rate.
How does strain rate affect a material?
As the speed increases, the yield strength and modulus also increase. The material appears to be stronger and stiffer simply due to the increase in strain rate, an effect that can also be achieved by keeping the strain rate constant and incrementally reducing the test temperature.
Does increasing strain rate increase ductility?
The conventional (quenched and tempered) reference material does not show similar behavior. Interestingly, the Q&P treated material’s ductility is considerably reduced at increasing strain rates while strength remains almost constant.
What happens when strain rate increases?
Increasing strain rate has the effect of increasing both the modulus and the yield stress and flow stress of a polymer.
How does strain rate affect mechanical properties?
From the results of this study, it is concluded that the increased strain rates increase the mechanical properties of material. The highest mechanical properties at the strain rate of 20 mm/min with a yield stress value is 563.78 MPa, and the maximum tensile strength is 590.17 MPa.
What is the importance of high strain rate testing for materials?
From a scientific viewpoint, being able to test materials over a wide range of strain rate including high strain rate testing allows the deformation mechanisms to be probed and understood, particularly with regard to determination of activation volumes.
What is the best method for ultra-high strain rate testing?
At the macroscale, there are numerous proven methodologies for ultra-high strain rate testing (impact experiments, Kolsky pressure bar, etc.). However, the micro- and nanoscales remain comparatively unexplored due to the inherent limitations of the established testing methods.
What is the strain rate of the nanoindentation test?
Although the nanoindentation technique has evolved in recent years, most tests are still typically performed in the quasi-static regime, meaning at strain rates in the range of 10 -5 to 10 -2 s -1.
What happens when the strain rate of a material increases?
As the strain rate increases even further, uniform deformation within the specimen becomes more critical. Inertia initially opposes uniform deformation, and a stress wave is transmitted and reflected within the test piece.