Buckling experiments on damaged cylindrical shells

It is well known that the buckling load of a thin cylindrical shell under axial compression depends significantly on the initial imperfection of the specimen. In this paper we focus attention on the effect of imperfections in the form of a particular kind of damage on the load-carrying capacity of a thin cylindrical shell. The study is an experimental one. The specimens used were steel drinks cans having a radius/thickness ratio of about 350. The damage was introduced by pressing in an indentation by hand and then pushing it out again:this left two locally damaged regions in the shell; and the level of damage could be characterised by the width of the initial indentation. The specimens were tested under eccentric axial compression. Careful visual observations were made of the behaviour of the shells in the damaged regions. In general, as the load increased a small dimple near the damaged zone grew in size; and turned gradually into a diamond shape. When the width of such a dent reached 25 mm, the can collapsed catastrophically. The nominal stress level in the region of the dent at buckling was around 0.24 of the classical buckling stress, whereas the buckling stress level for undamaged cans was 0.5+/-0.1 of the classical value. Copyright (C) 1996 Elsevier Science Ltd.