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ASME formula t=PR/(SE-0.6P) - consideration of end load

ASME formula t=PR/(SE-0.6P) - consideration of end load

ASME formula t=PR/(SE-0.6P) - consideration of end load

(OP)
Hi engineers,

A quick one, t=PR/SE-0.6P to calculate thk under internal pressure (circumferential stress).
Why ASME doesn't combine this circumferential stress with the longitudinal stress generated by the end load which is around 1/2 the circumferential stress ?

RE: ASME formula t=PR/(SE-0.6P) - consideration of end load

Primarily because those stresses are in different directions/orientations.

And that formula is based on a failure theory of maximum principal stress. of which the hoop stress is.

Make sense?

RE: ASME formula t=PR/(SE-0.6P) - consideration of end load

(OP)
TGS4 thanks for your reply.

Yes and no, if we consider a small piece of shell the two forces are working in the same plane and should be combined by the square root of the sum of the square for example ?

RE: ASME formula t=PR/(SE-0.6P) - consideration of end load

No. There are multiple theories of failure: maximum principal stress, maximum shear stress (Tresca), maximum distortion energy (von Mises) that are meant to correlate uniaxial stress results to multi-axial stress states.

In VIII-1, the maximum principal stress theory is used. In VIII-2, for pressure only, the same is used, but for combined loadings (or design-by-analysis) the von Mises theory is used. (Old VIII-2 and current Section III used/uses Tresca).

RE: ASME formula t=PR/(SE-0.6P) - consideration of end load

(OP)
Ok TGS4,

It does make sense.

Thanks for your expalantions.

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