Why is Creep Temperature Higher than Melting Point?

In summary: The testing is performed in a furnace at a temperature of 1,100 degrees Celsius. In summary, the standard testing method for creep rupture is performed in a furnace at a temperature of 1,100 degrees Celsius.
  • #1
Ameya Joshi
4
0
Why is the actual value of temperature, at which alloy is at a risk of creep, higher than the expected 0.3 (or 0.4)
of melting point?
 
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  • #2
Creep is the time dependent inelastic deformations of materials that is a function of stress and temperature as well as time. Creep is more significant at temperatures near the melting point, but it can occur at normal ambient air temperatures also. I believe that 30 percent of melting temperature value is established for metals as the point where creep becomes noticeable, but it's greater effect occurs at temperatures higher than that, if that is what you mean. Deformations due to creep are not recoverable. I haven't worked much with creep except for its effects on long cables under high tension, especially aluminum cables.
,and at temperatures below 100 degrees C. After 10 years, Inelastic deformations are sometimes significant.
 
  • #3
Fundamentals of Creep in Metals and Alloys

Creep of an alloy depends on stress, temperature and composition. Larger atoms in a bulk metal will interfere with dislocation glide, so they can improve creep resistance. Some second phase particles and intermetallic compounds can improve creep resistance.

See also - http://ame-www.usc.edu/research/advanced_materials/science.pdf - for example.
 
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  • #4
can anyone of you guys please tell me different ways of preventing or minimizing creep in materials?
 
  • #5
mpotsengshimi03 said:
can anyone of you guys please tell me different ways of preventing or minimizing creep in materials?

Grain boundaries are very weak areas when compared to lattice structure. Thus, they are prone to creep behavior. Therefore less grain boundaries you have, high creep resistance you have. That means, if you can increase your average grain size, you will have higher creep resistance compared to small grain sized material.
 
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  • #6
yirmidokuz said:
Grain boundaries are very weak areas when compared to lattice structure. Thus, they are prone to creep behavior. Therefore less grain boundaries you have, high creep resistance you have. That means, if you can increase your average grain size, you will have higher creep resistance compared to small grain sized material.
thank you so much
 
  • #7
yirmidokuz said:
Grain boundaries are very weak areas when compared to lattice structure. Thus, they are prone to creep behavior. Therefore less grain boundaries you have, high creep resistance you have. That means, if you can increase your average grain size, you will have higher creep resistance compared to small grain sized material.
Which is why turbine blades are preferably single crystal.

http://iweb.tms.org/SUP/selectedreadings/01-1022-205.pdf

I should have added microstructure to the list with stress, temperature and composition.
 
  • #8
I am trying to do a creep rupture test at high temperature to a tube with dia. 5'', thick. 6.5mm. Can anyone help me with the standard specimens diamensions, especially the length of this specimen. Is the whole specimen covered with the furnace ?
thanks for any effort
 
  • #9
Inspector Eng said:
I am trying to do a creep rupture test at high temperature to a tube with dia. 5'', thick. 6.5mm. Can anyone help me with the standard specimens diamensions, especially the length of this specimen. Is the whole specimen covered with the furnace ?
thanks for any effort

This file, astm standard e139, elucidates the standard testing method for determining the creep rupture of a material.
I hope you can find the details you need, in the file.
 

Related to Why is Creep Temperature Higher than Melting Point?

1. Why is creep temperature higher than melting point?

The creep temperature is typically higher than the melting point because creep is a process that occurs at high temperatures and under constant stress, while the melting point is the temperature at which a material transitions from a solid to a liquid state. In other words, the melting point is a characteristic of the material itself, while creep is a phenomenon that is influenced by external factors such as temperature and stress.

2. What is creep and how does it differ from melting?

Creep is the gradual deformation of a material under constant stress at high temperatures. It is a time-dependent process that occurs over an extended period of time. In contrast, melting is the transformation of a solid material into a liquid state when it reaches its melting point. Melting is an instantaneous process, whereas creep is a continuous process.

3. Is there a relationship between creep temperature and melting point?

Yes, there is a relationship between creep temperature and melting point. Generally, materials that have higher melting points also have higher creep temperatures. This is because materials with high melting points are more resistant to deformation and can withstand higher temperatures and stress before undergoing creep.

4. What factors affect the creep temperature of a material?

There are several factors that can affect the creep temperature of a material, including temperature, stress, and time. Higher temperatures and stress levels can accelerate the creep process, while longer periods of time can also contribute to creep deformation. Additionally, the composition and microstructure of the material can also impact its creep behavior.

5. How is creep temperature measured?

Creep temperature can be measured through various techniques such as creep testing or stress relaxation testing. These tests involve applying a constant stress to a material at different temperatures and measuring the resulting deformation over time. The temperature at which the material starts to deform significantly is considered the creep temperature.

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