Learning Forum

[jonsys]

I do a curve fit for visco-elastic material using the Shear Data (Shear Modulus-Time) for 3 different temperatures [Fig 1].
After I 'Solve Curve Fit', I get the Prony Shear data (Relative Moduli and Relaxation Time) so I 'Copy Calculated Values To The Property'. The graph in the curve fit seems to match the points. 
But these Prony Shear Data generated by the curve fit seems kind of strange [Fig 2] (strange because Prony shear parameters usually follow a trend (as far as I know), for example, time is decreasing).

Moreover, for this case, I have additionally the Prony Series, but the values seem to be very different [Fig 3].

Any suggestions? 
How much should I trust ANSYS curve fit?

[John Doyle]

Try to curve fit relaxation for just one temperature.

[jonsys]

I tried for one temperature and:

• When I click at curve fitting [Fig 1], the curve fits the points satisfactory.


• After I copy the calculated values to the property [Fig 2], and click on Prony Shear Relaxation [Fig 3], the curve dos not fit anymore the points (it's just flat instead). - Version 17.1


• So I tried curve fit with 19.1 Student version and the Chart problem mentioned at point 2 is solved. However, I get the same values of Relative Moduli and Relaxation Time, which still do not follow any trend (increasing the number of parameters won't help).

Regards,