extrapolated CTE?

[subsearobot]

hi,
I am looking for the CTE of SA-508a (stainless steel) at 0deg C. From what I can tell, the ASME BPVC lists the CTE down to 20C. We are not designing to the code, so can not justify the cost of purchasing it; that said, we would like to follow the rules as practical.

Does the ASME code have a policy for extrapolating?

thanks.

 

[metengr]

You mean interpolate, not extrapolate, because ASME does not allow extrapolation of their published data outside of stated service temperature ranges. So, you can only use linear interpolation.

 

[subsearobot]

thanks, metengr

 

[trottiey]

I'm not sure that interpolation of CTE has to be linear. There's an interpretation that says interpolation of stress allowable has to be linear, but nothing I know of on CTE. When using the external pressure tables, the code says "linear interpolation or any other rational interpolation method may be used," so it's not a universal rule.

Stress is a biological mechanism that improves strength at the expense of thought. It is counter-productive to solving technological problems.