Some Calculations to Assess the Effect of the Stress-Strain rate Relationship on Creep in the Neighbourhood of An Opening in a Pressurized thin Spherical Shell

Abstract

Calculations were performed on a pressurized thin spherical shell with a sealed opening for material obeying a simple r-power steady creep law; they were done by an iterative procedure on an IBM 7090 computer. The results, in terms of stress resultant distributions and deformation patterns in the neighbourhood of the opening for different edge load boundary conditions, were examined critically with a view to detecting simple overall patterns of behaviour which are a function of the creep index r. Examination of the results from two different points of view leads to the conclusions that stress concentration factors vary smoothly and almost linearly with 1/ r and that deformation patterns are practically independent of r, for the same edge load boundary conditions. The strain rate concentration factors may be very high. The consequences of these conclusions are examined in the context of the design process.