For smaller diameter (say under 3") we take an 18" long piece of tube and put plug in the ends and pull tensile test on it full body or full section.
Now if it is heavy wall (load above our machine) or larger diameter we will cut a longitudinal strip out of the the tube and just flatten the ends for grip, machine a gauge section to precise width, and test that.
The elongation for the strip sample will always be lower, because there is no column collapse contributing to overall elongation.
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P.E. Metallurgy