Some observations on the nonlinear vibration of thin cylindrical shells

appear to be relatively independent of the nominal radius of the shell. Based on the local curvature of the "flat spot' rather than on the nominal curvature which is commonly used, a new upper bound may be determined for the collapse strength of an initially imperfect spherical shell. This observation is the basis of an analysis developed in Ref. 14 which adequately predicts both the elastic and inelastic strength of 36 machined models with local "flat spots" covering a relatively wide range of 6,