From Tennyson, et al.
The ratio of the axial wavelength of the manufactured axisymmetric imperfection to the axial wavelength of the critical axisymmetric buckling mode of the perfect shell is about 0.594.
The test results fall somewhat below the theoretical results probably because there are other types of imperfections besides the intentionally manufactured axisymmetric sinusoidally varying shape of the generator, such as unavoidable slightly circumferentially varying nonuniform axial loading, very small variations in shell wall thickness and/or elastic properties, because the manufactured imperfection is not exactly axisymmetric, and/or the boundary conditions are slightly different from those postulated in the theory.
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