An Application of Two Step Stress Classification Approach (Primary Structure Method) for Stress Classification at Cylindrical Shell–Nozzle Intersections Subjected to Internal Pressure, Radial Load and In- and Out-of-Plane Bending Moments

Stress classification at shell and nozzle interface had always been an interesting and challenging problem for Engineers. Basic shell theory analyses shell stresses as membrane with local bending stresses developed at locations of discontinuity and load applications. Since in a shell structure, bending stresses develop to mainly maintain compatibility of deformation and membrane stresses to equilibrate the applied load, a simple stress classification will be to categorize the bending stresses as secondary stresses. This is because by definition, secondary stresses develop to maintain compatibility of deformation and primary stresses develop to maintain equilibrium with the applied load. This simplified analysis can result in errors as in real world 100% primary stress as well as 100% secondary stress is rare if not impossible [15], [16]. The widespread use of Finite Element Analysis has made this problem become even more challenging. Several researchers have addressed the problems of stress classification. References [1], [2], [3], [4], [5[, [6], [11], [12] can be consulted for additional details. In this paper the work done by Chen and Li [1], using the two step primary structure method has been used to analyse the problem of stress classification of a shell and nozzle. The spirit of the method has been retained, but several FE models have been made with some deviations from the method in ref.[1], to meaningfully arrive at primary structures.