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# Poisson's ratio at elevated temperatures

## Poisson's ratio at elevated temperatures

(OP)
In metals, E and Fy decrease as temperature increases.  Is Poisson's ratio affected by elevated temperatures (100 deg F to 1000 deg F)?

### RE: Poisson's ratio at elevated temperatures

I know for sure that Poisson's is temperature-dependent in many metals.

My recollection is that the general trend is a lowering of Poisson's as temperature increases (but not with 100% certainty).

I think I may have a reference about more specifics. I'll try to dig it out.

### RE: Poisson's ratio at elevated temperatures

All good reference books quote Poissons Ratio for different materials at room temperature.  For this reason I believe it to be temperature dependent.

### RE: Poisson's ratio at elevated temperatures

If you consider what Poissons ratio is determined by, then would the thermal expansion constant not be the same for the material in both directions?, If so, this would suggest that poissons ratio wouldn't change.

### RE: Poisson's ratio at elevated temperatures

PR vs T for some typical metals:
INCO 718:  0.294 @ 70F; 0.306 @ 1400F
INCO 625:  0.308 @ 70F; 0.329 @ 1400F
A286:      0.280 @ -320F; 0.300 @ 70F; 0.360 @ 1600F

Does anyone have any data for Aluminum and Al-Li alloys?

### RE: Poisson's ratio at elevated temperatures

Using the following data (taken from Kaye and Laby) it is possible to calculate the tempco for different materials.  Aluminium is chosen here as an example:

At 20 deg C,

E=70.3*10^9  (Pa)
G=26.1*10^9  (Pa)
Tempco for E is -480 ppm/degC
Tempco for G is -520 ppm/degC

For a homogeneous isotropic solid,
Poissons Ratio =(E/2G)-1

By plotting Poisson's Ratio against temperature the tempco for Poisson's Ratio for Aluminium at 20C turns out to be +55.6 ppm/degC

### RE: Poisson's ratio at elevated temperatures

I know that for Inconel 600, E as well as G decreases with increasing temperature, approximately parabolically.. Depending on these relations, Poisson's ratio changes with temperature accordingly..
For Inconel 600, Poisson's ratio first drops, and later rises again with temperature..

I took my data from the publications at www.specialmetals.com

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