UG-101, Proof Test per Displacement measurement for SS CF8M

[Swap Material]

Hi Expert,

Need your opinion, whether to proof test CF8M material by Displacement measurement?
I read "materials having a definitely determinable yield point"
By any other means can I do that?

 

[EdStainless]

For what reason? Is there a specification?

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P.E. Metallurgy, consulting work welcomed