Viability of Determining residual stress with ASTM E837 using Rosette Strain Gauges

[bradsr0138]

Can someone explain to me how effective the procedure outlined in ASTM E837 is at determining residual stress in a heavy wall pressure vessel?

The situation I have is that a fabricator is proposing to do this test on a recently in-service vessel to determine if pre-heat is necessary prior to making modifications to a vessel. Is this procedure good at determining stress throughout the thickness of the wall or just the surface stress?

 

[EdStainless]

How will they then get stress relief for the measurement?
When we do this on tubes we then drill a flat bottom hole through the center of the SG in various depth steps.
This gives us an idea of the residual stress (after a bunch of modeling).
But we are only dealing with something 0.100" thick.

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P.E. Metallurgy, consulting work welcomed

 

[bradsr0138]

EdStainless, I don't think I understand your question... The stress relief for measurement is measured using the rosette gauge. I am just wondering if total residual stress measured/calculated is representative of the entire wall thickness of the shell, or just the surface to the depth of the flat bottom drilled hole.

 

[EdStainless]

You need to look at the modeling that they use for actually calculating the stresses.
As I recall the stress field slightly below the bottom of the hole has some effect, but not very far.
Also ask about the uncertainties in this process, they are huge.
We were trying to measure values <10ksi and often saw uncertainties of +/-6ksi.
And we could drill in steps all of the way through.


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P.E. Metallurgy, consulting work welcomed

 

The situation I have is that a fabricator is proposing to do this test on a recently in-service vessel to determine if pre-heat is necessary prior to making modifications to a vessel.

I'm not sure this correctly expresses the fabricator's question. Are they referring to something different than preheat for welding?

Preheat is determined by Code, technical specification and engineering judgment (always). And preheat in the usual range doesn't do that much to lower peak residual stresses from welding. If the PV is heavy walled, is PWHT not involved?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."