Collapse Analysis For Shells Of General Shape

F33615-69-C-1523AF-1467AFFDLTR-71-8-Vol-2See also report dated Aug 72, AD-751 702.(*shells(structural forms), failure(mechanics)), (*computer programming, instruction manuals), structural properties, loads(forces), buckling, plastic properties, bodies of revolution, subroutinesnewton-raphson method, collapse, programming manuals, finite difference theory, *stags computer program, structural analysisThe manual presents STAGS, a comprehensive computer code. STAGS is intended for the static analysis of arbitrary shells including the effects of nonlinearities caused by material behavior and finite deformations. Collapse loads based on nonlinear analysis can be computed as well as buckling loads based on classical bifurcation buckling theory with linear prestress. Arbitrary thermal and mechanical loadings can be specified. The manual rpovides instructions for use of the code and presents sample problems and solutions. The program is under development and the version presented here is expected to be updated in 1973. The previous report, Volume 1 (AD-751 702), contains the numerical analysis.

F33615-69-C-1523, AF-1467146703, AFFDLTR-71-8-Vol-1(*shells(structural forms), failure(mechanics)), structural properties, numerical analysis, buckling, plastic properties, tensor analysis, computer programming newton- raphson method, collapse, plates(structural members), finite difference theory, stags computer program, structural analysis. The report presents a theory for nonlinear collapse analysis of shells with general shape. The theory combines energy principals and finite difference methods to obtain a system of nonlinear equations; these are solved by a modified Newton-Raphson technique. For greater economy and flexibility in the analysis a capability is provided for use of variable spacing finite difference grids. Inelastic material behavior, as predicted by the White-Besseling Theory, is incorporated into the analysis. A computer code, STAGS, based on the theory has been written and used to solve a number of sample problems. Results for these problems are presented.

The report contains an assessment of current shell analysis capability. The assessment is based on work conducted at the Lockheed Palo Alto Research Laboratory under contract to the Air Force Flight Dynamics Laboratory. In addition to surveying the open literature, information for the study was gathered during a series of visits made to organizations throughout the United States at which there is an active shell analysis research effort. More than 40 industrial concerns, government agencies and universities have been visited to date. During each visit, technical personnel working in the area of shell analysis were interviewed to determine the scope of their present analysis capability, to learn of current research activities and to discuss computer methods of shell analysis in general. Information so obtained is summarized in a series of briefs which appear in the Appendix of this report.

Thin shells are very popular structures in many different branches of engineering. There are the domes, water and cooling towers, the contain ments in civil engineering, the pressure vessels and pipes in mechanical and nuclear engineering, storage tanks and platform components in marine and offshore engineering, the car bodies in the automobile industry, planes, rockets and space structures in aeronautical engineering, to mention only a few examples of the broad spectrum of application. In addition there is the large applied mechanics group involved in all the computational and experimental work in this area. Thin shells are in a way optimal structures. They play the role of·the "primadonnas" among all kinds of structures. Their performance can be extraordinary, but they can also be very sensitive. The susceptibility to buckling is a typical example. David Bushnell says in his recent review paper entitled "Buckling of Shells - Pitfall for DeSigners": "To the layman buckling is a mysterious, perhaps even awe inspiring phenomenon that transforms objects originally imbued with symmetrical beauty into junk".

This Festschrift marks the retirement of Professor Chris Calladine, FRS after 42 years on the teaching staff of the Department of Engineering, University of Cambridge. It contains a series of papers contributed by his former students, colleagues, and friends. Chris Calladine's research has ranged very widely across the field of struc tural mechanics, with a particular focus on the plastic deformation of solids and structures, and the behaviour of thin-shell structures. His insightful books on Engineering Plasticity and Theory of Shell Structures have been appreciated by many generations of students at Cambridge and elsewhere. His scientific contri bution outside engineering, in molecular structures, is at least as significant, and he is unique among engineers in having co-authored a book on DNA. Also, he has been keenly interested in the research of many students and colleagues, and on many occasions his quick grasp and physical insight have helped a student, and sometimes a colleague, find the nub of the problem without unnecessary effort. Many of the papers contained in this volume gratefully acknowledge this generous contribution. We thank Professor G. M. l. Gladwell for reading through all of the contri butions, Mrs R. Baxter and Mrs o. Constantinides for help in preparing this volume, Godfrey Argent Studio for permission to reproduce Calladine's por trait for the Royal Society, and Dr A. Schouwenburg -from Kluwer- for his assistance. Horace R. Drew Sergio Pellegrino ix CHRIS CALLADINE SOME THOUGHTS ON RESEARCH c. R.