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Data Fitting: Cross-WLF Function

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tirta78

Korea
1 Posts

Posted - 05/11/2014 : 11:29:04 PM

Dear All

I'm trying to fit my equation:
eta=(d1*exp((-a1*(T-d2))/(a2+(T-d2))))/(1+((gama*d1*exp((-a1*(T-d2))/(a2+(T-d2))))/tau)^(1-n))

where:
eta is the Viscosity in Pa s
gamma is the Shear Rate in 1/s
T is the Temperature in K. and its 425K
a1, a2, d1, d2, n, tau are data-fitted coefficients.

As my understanding, since my eta (viscosity) result, I will put it as dependent parameter as y, and gamma as independent parameter as x.

However, I cant get the data fitting works here.

My data is:

Eta Gamma
0.6283 726.6
0.996 709.9
1.578 681.1
2.502 651.6
3.962 607.5
6.283 561.7
9.929 507.2
15.77 453.2
25.03 395.6
39.72 339
62.77 285.4
99.75 235.3
157.9 190
249.9 151.4
389.9 119.8
627.7 90.13

Can anyone give me advice for this?

Thank you

Thank You

JacquelineHe

287 Posts

Posted - 05/12/2014 : 07:03:39 AM

Hi,

If you want to create a user-defined function to fit your data, I suggest you can use the Fitting Function Builder to create your fitting function. Then you the user-defined function to fit your dataset.

Please refer to this help page and the Tutorial for the Fitting Function Builder
http://www.originlab.com/doc/Tutorials/UserDef-FitFunc
http://www.originlab.com/doc/Origin-Help/FitFunc-Builder

Thanks
Jacqueline
OriginLab

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