# Difference between Creep and Strain Rate Sensitivity

• phgw
In summary, the conversation discusses the difference between creep and strain rate sensitivity in material science. Creep refers to the constant load applied to a sample and the resulting strain versus time, while strain rate sensitivity looks at how the material's performance changes with different strain rates. These phenomena are different and have different time scales.
phgw
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?

- To measure the creep of a material using nanoindentation, the load is applied to the sample and then held constant for a given time. If the indenter continues to penetrate the sample during this time, creep occurs.
- To measure strain rate sensitivity, the load is applied to the sample within different times. If there's a difference between applying the load slowly or fast, the material shows strain rate sensitive behavior.

For me, these two things seem to be quite similar. Or are these phenomena two totally different things? If not, are there equations that show the similarities?

I am sorry, I know that this is probably really basic stuff, but maybe somebody can explain it to me.

Thanks a lot,

phgw

The time scales for rate sensitivity range from 1/s to 10^8/s (ballistics and blast). The time scales for creep are much slower.

creep is constant load, looking at the strain versus time.
strain rate sensitivity looks at how the performance (typically yield) of a material changes depending on how quickly/slowly you strain the material.

they are very different.

## 1. What is creep?

Creep is the slow, time-dependent deformation of a material under a constant load or stress. It is a gradual process that can occur in both metals and non-metals and is often seen in materials under high temperatures or long-term stress.

## 2. What is strain rate sensitivity?

Strain rate sensitivity is the measure of a material's response to changes in the rate of deformation. It is a property that describes how the material's strength and stiffness change as the strain rate (or speed of deformation) changes.

## 3. What is the difference between creep and strain rate sensitivity?

The main difference between creep and strain rate sensitivity is that creep is a time-dependent phenomenon, while strain rate sensitivity is related to the rate of deformation. Creep is a gradual process that occurs over time under a constant load, while strain rate sensitivity is an immediate response to changes in the rate of deformation.

## 4. How are creep and strain rate sensitivity related?

Creep and strain rate sensitivity are related in that they both involve the deformation of a material, but they are different properties that affect the material in different ways. Creep is a long-term process, while strain rate sensitivity is an immediate response to changes in the rate of deformation.

## 5. Why is understanding the difference between creep and strain rate sensitivity important?

It is important to understand the difference between creep and strain rate sensitivity because they both play a role in the behavior and performance of materials. Creep can lead to structural failure over time, while strain rate sensitivity can affect the material's strength and stiffness, making it important to consider in applications where the material will experience varying rates of deformation.

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