Ansys interpretation of material properties using mpdata | only one data point | two data points

[shiraz883]

Hi,

I am defining material property (thermal conductivity) for material in Ansys using mptemp and mpdata command. I define the property using two options or rather I have the values sometimes for a particular material at only one temperature and sometimes for some other material it is two data points but the temperature of the component falls outside the range of points defined. How does Ansys interpret and calculates the value at the component temperature?

There are two scenarios possible:

First, only one data point: If I define a material property (let’s say thermal conductivity) for a particular component at a particular temperature (say 1000°C) and if the temperature encountered at that component is 1500°C, what will be the value of thermal conductivity used at 1500°C by Ansys? Will Ansys use the constant value defined at 1000°C ?

Second, two or more data points: If I define the thermal conductivity at 400°C and 500°C but the temperature at that component is 1500°C, what will be the value of thermal conductivity used at that temperature by Ansys? Will Ansys extrapolate and calculate the value at 1500°C?

Thanks
Shiraz

 

[rickfischer51]

No clue what would happen if you use MPTEMP and MPDATA to define a material, and then give it only one data point. Why would you do that? Just use MP. My guess is it will treat it as a material property with no temp dependence. If you specify 2 data points but run the analysis outside that temp range, it takes the specified value closest to the model temp, in you example above, it would take the value at 500C. The software is not going to guess what the material curve looks like from 2 data points. If you want it extrapolated, you pick the method, do the extrapolation, and put in data at a higher temp.

This is the stuff you should be figuring out on your own. Make a simple model, change the temp, and see what happens. This is not hard to do and probably quicker than waiting for an answer. And are more likely to remember it.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[shiraz883]

Thanks Rick.

I think you are right. Will give it a try.

Shiraz
Senior Engineer
Haldor Topsoe