What is high strain rate testing?

High strain rate testing is important for many engineering structural applications and metalworking operations. Kolsky invented the split-Hopkinson pressure bar, which allows the deformation of a sample of a ductile material at a high strain rate, while maintaining a uniform uniaxial state of stress within the sample.

Why do materials generally appear to be stronger when they are tested at higher strain rate?

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 impact testing involve higher strain rates than tensile testing?

We can observe this behavior using a lower strain-rate test such as a tensile test. Tensile tests apply stress over a significantly longer time scale than impact tests. As the strain rate increases we measure a higher yield stress and tensile modulus.

What is strain rate effect?

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.

How do you calculate strain rate?

Strain rate = velocity/length of the specimen, rough approximation,here velocity is velocity of the striker bar. Otherwise use voltage- time data to get microdeformation-time data. This should serve the purpose.

What does an increase in 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 is the strain rate effect?

What is effective strain rate?

The term “effective strain rate” is frequently encountered in literature devoted to the ice-structure interaction problem. As a rule, it is defined as a ratio between indentation velocity and structure width, multiplied by a certain nondimensional factor (αV/d).

How is strain rate calculated?

Why do we need high strain rate testing?

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’s the maximum strain rate for fused silica?

Before this study, published in 2019, the mechanical properties of fused silica had only ever been investigated up to maximum strain rates of < 0.02 s -1 so the potential of the Alemnis system to increase knowledge of materials at high strain rates is undeniable!

How many orders of magnitude is an ultra high strain rate?

The Alemnis Standard Assembly (ASA) achieves ultra high strain rate covering 8 orders of magnitude. The Alemnis Standard Assembly (ASA) can be configured in several ways to achieve ultra high strain rates up to 10’000 s -1, thus covering 8 orders of magnitude!

What should be the strain rate of nanoindentation?

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.