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# finding the larsson miller curve based on raw data

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## finding the larsson miller curve based on raw data

(OP)
Hi all,
How do i determine a larson-miller regression line based on raw creep data (time, temp, stress)? The material doesnt exist in the standards.
I assume i could do a spline based of the data?

I guess what i am looking for is a larson-miller parameter calculator, but i am certain i am oversimplifying this immensely :)

Appreciate any form of guidance.

### RE: finding the larsson miller curve based on raw data

you could use C=20 to simplify P = f(σ) = T (log t + C. if not use P = f(σ) = T (log t + C(σ))·10^−3 to get C. then run stress σ vs parameter C, C(σ) = -A σ + B regression with at least 3 stress data points.

### RE: finding the larsson miller curve based on raw data

And then continue the process and fill in with a lot more data points.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

### RE: finding the larsson miller curve based on raw data

(OP)
Thank you for the response,

I have the data set in the link below. What is the correct way to determine a lower scatter band representing a 95% confidence level?
Is there a certain method that is used to determine creep values, or is it sufficient to do a spline and then determine a standard deviation? I am not sure how to achieve this, though.

Is this possible to achieve in Excel with no addons?
I also have access to Mathcad.

My goal is to determine an allowable stress for an ASME pressure vessel.

https://homepages.abdn.ac.uk/h.tan/pages/teaching/...

edit: corrected the link

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