System Engineering / Pressure Equipment

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Plastic buckling of thin-walled pipes with D/t > 50 and conclusions for the nuclear design codes (Speech) (24.10.2016)

Speech on the 42nd MPA-Seminar, October 4th and 5th 2016

Ideal elastic-plastic pipes with D/t ≤ 40 fail with a simple kink. Pipes with D/t > 40…70 fail by (plastic) buckling with some wrinkles. The numerical obtained failure shapes are in a good agreement with the experimental shapes. The B2 index significantly depends on the D/t ratio, the elastic modulus and the yield stress. The imperfections have a considerable influence on the B2 index. For ideal elastic-plastic pipes with D/t = 100 and a usual out of roundness of 0.5% typical values for the B2 index are 1.3 for a yield stress of 250 MPa and 1.5 for 500 MPa.

The differences between the B2 indices for ideal and real materials are small and therefore without practical importance. A comparison of the numerical obtained B2 indices with experimental re-sults indicates an out of roundness of 0.5%. Final statements are not possible, because the re-quired information about the experiments is not completely available.

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