Strength analysis of joints in shells and bottoms with connecting pipes run through a flange

Abstract

with the complexity of the geometry of the coupling zone between the shell or bottom and a connecting pipe through a flange, and with the sharp change in curvature of the surface of the composite shell structure. Familiar analytical methods [2] are highly approximate and are based on a number of assumptions that markedly limit the range of application of the computational formulas used to estimate maximum stresses. The difficulties of experimental investigation, for example, when a strain-measurement method is used, are governed by the fact that the flange possesses a short length and large (absolute) curvature in the meridional direction. This complicates direct strain measurement (especially meridional strains). In our study, we investigate the most general approach to computational analysis of structural joints in intersecting-typ e shells on the basis of the finite-element method (FEM) An applied computational procedure, which is the evolution of a computational procedure for flange-free joints, is developed [3]. The body of computations is based on use of the moment theory of shells. Structurally, a flanged joint is a composite shell structure in which the flange is represented as the part of a toroidal shell that ensures smooth coupling between the basic shell (shell or bottom) and connecting pipe. In performing the calculation by the FEM, the joint under consideration is replaced by a finite-element model using tetragonal elements of an arbitrary shell of revolution. The elements are defined in a curvilinear coordinate system on the median surface shell; geometric relationships defining a mutually unique relationship between the curvilinear coordinates of the shell and matrix transformations of the coordinate system, are therefore established for the shell's lines of intersection. Skopinskii and Kazachkin [4] discuss the computational procedure in greater detail. The applied procedure has been implemented on a computer in the form of the SAIS (Stress Analysis in Intersecting Shells) software package for computational analysis of the stress state of standard joints in intersecting shells. The SAIS is a problem-oriented computer program and ensures simplicity of initial-data presentation, automated generation of a computed model of the joint, small computer outlays, and sufficiently accurate and complete analysis of the stress state of the jointed shell. The software package has been run on both the ES computer and IBM PC/AT-type personal computer. In the version for the personal computer, there is an interactive graphics postprocessor, which provides a convenient graphic form of representation for the computed results. The software has been widely verified. Due to a lack of detailed results of investigations for joints with a flange, we planned and performed special experimental studies of models of a cylindrical shell with a radial connecting pipe using the method of photoelasticity with "freezing" of deformations. Careful planning of the experiment made it possible