Imperfections and buckling in cylindrical shells with consistent residual stresses

Metal silo walls are often constructed from isotropic plates, and the contr olling design condition is buckling under axial compression. It has long be en recognised that this buckling strength is highly sensitive to imperfecti ons in the cylindrical shell, but most attention has been paid to geometric imperfections and imperfect boundary conditions. Imperfections in the form of residual stresses have only rarely been investigated, and the challenge s facing a rigorous treatment of them have often not been faced. This paper adopts a rigorous treatment technique to investigate residual stresses and their effect on the axial compression buckling strength under elastic cond itions. It achieves this by considering consistent stress and displacement fields arising from local geometrical incompatibilities, and adopting their consequent geometric imperfections. The calculations of the strength of im perfect shells with residual stresses are compared with corresponding calcu lations for the same imperfections but with the residual stresses 'annealed ' out of the analysis. The results show that consistent residual stresses g enerally appear to strengthen a thin shell relative to the corresponding st rength with only geometric imperfections present. (C) 2000 Elsevier Science Ltd. All rights reserved.