Schematic of the joint in the payload shroud that buckled during a test

Local buckling failure is caused by an axisymmetric inward excursion of the load path of the axial compression seen by the payload shroud at Station 468. This is a known “imperfection” that can be included in the computerized model.

This known “imperfection” is the most serious imperfection in the entire fabricated shell because during a test the payload shroud failed because of it and not because of some unknown and unknowable random imperfection.

Therefore, one might say that the payload shroud as fabricated is not imperfection sensitive in the “classical” sense of that term.

If the payload shroud had been designed taking account of the load path eccentricity at Station 468 (by the use of a thicker doubler, for example) then the stiffened cylindrical shell would be classed as “moderately imperfection sensitive” (See Part 2 above).

Page 27 / 28