Knockdown factors for buckling of cylindrical and spherical shells subject to reduced biaxial membrane stress

• Published in: International journal of solids and structures Vol. 47; no. 10; pp. 1443 - 1448
• Main Author: Hutchinson, John W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.05.2010
• Subjects: Buckling; Compressing; Cylindrical shells; Defects; Imperfection-sensitivity; Knockdown factors; Membranes; Reduction; Spherical shells; Stresses; Cylindrical shells; Spherical shells; Imperfection-sensitivity; Buckling; Knockdown factors
• ISSN: 0020-7683; 1879-2146
• DOI: 10.1016/j.ijsolstr.2010.02.009

Cylindrical shells under uniaxial compression and spherical shells under equi-biaxial compression display the most extreme buckling sensitivity to imperfections. In engineering practice, the reduction of load carrying capacity due to imperfections is usually addressed by use of a knockdown factor to lower the critical buckling stress estimated or computed without accounting for imperfections. For thin elastic cylindrical shells under uniaxial compression and spherical shells under equi-biaxial compression, the knockdown factor is typically as small as 0.2. This paper explores the alleviation of imperfection-sensitivity for loadings with a reduced circumferential (transverse) membrane stress component. The analysis of Koiter (1963) on the effect of an axisymmetric imperfection on the elastic buckling of a cylindrical shell under uniaxial compression is extended to both cylinders and spheres for loadings that produce general combinations of biaxial membrane stresses. Increases in the knockdown factor due to a reduction of the transverse membrane component are remarkably similar for cylindrical and spherical shells.