Effect of a Local Axisymmetric Imperfection on the Buckling Behavior of a Circular Cylindrical Shell under Axial Compression

A combined theoretical and experimental investigation has been carried out on the effects of certain types of local axisymmetric imperfections on the buckling of cylindrical shells un­ der axial compression. Buckling loads have been calculated for a variety of "dimple" imper­ fections. Results have been obtained for constant thickness shells with middle surface variations from the geometry of a perfect cylinder as well as for shells with local axisymmetric thickness variations. Nonlinear prebuckling elrects and edge conditions are taken into ac­ count. In the experimental program a series of seven photoelastic plastic circular cylindrical shells each containing a local axisymmetric dimple centered at mid-length were tested under pure axial compression. All cylinders were constructed by the spin-casting technique and the local imperfection was cut on both the inner aud outer walls using a hydraulic tracer-tool apparatus in conjuuction with a metal template. A broad range of imperfection amplitudes and wavelengths was investigated. The experimental results were in good agreement with the theoretical predictions.