טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBen-Yosef Yiska
SubjectImperfection Sensitivity of Conical Shells
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Emeritus Izhak Sheinman
Professor Emeritus Menahem Baruch (Deceased)


Abstract

    The thesis is devoted to the comprehensive study of the stability and imperfection sensitivity of shells according to Koiter’s theory. Conical shell was chosen as a representative shell structure that exhibited of the entire range of sensitivity imperfection: it varies from the very sensitive to imperfection- cylindrical shell to the completely non-sensitive- annular plate. By changing the cone semi vertex angle one can learn about the characteristic behavior of shell structure, and to understand the mechanism its behavior. The main goal of this research is to determine the parameters that affect the buckling load and the imperfection sensitivity, by. The imperfection sensitivity of conical shells is considered - via the initial post buckling analysis - on the basis of three different shell theories: Donnell’s Sanders’ and Timoshenko’s. The procedure involves nonlinear partial differential equations, which are converted into a sequence of three linear sets. The equations are solved with the variables expanded in Fourier series in the circumferential direction and finite differences in the axial directions. A general code is developed and used in studying the effect of higher exactness of the shell theory on the sensitivity behavior of: isotropic, stiffened and anisotropic angle-ply cylindrical shells, isotopic and stiffened conical shells. A main conclusion drawn from this work reveals that the sensitivity to imperfection is affected by the accuracy of the theory used in the analysis. In other words- the more accurate the shell theory is, the less sensitive to imperfection. The least accurate shell theory may indicate certain sensitivity and the most exact, none at all.