Panel Optimization With Integrated Software Pois

An analysis and an interactive computer program are described through which minimum weight designs of composite, stiffened, cylindrical panels can be obtained subject to general and local buckling constraints and stress and strain constraints. The panels are subjected to arbitrary combinations of in-plane axial, circumferential, and shear resultants. Nonlinear material effects are included if the material is isotropic or has stiffness in only one direction (as does a discrete or a smeared stiffener). Several types of general and local buckling modes are included as constraints in the optimization process, including general instability, panel instability with either stringers or rings smeared out, local skin buckling, local crippling of stiffener segments, and general, panel, and local skin buckling including the effects of stiffener rolling. Certain stiffener rolling modes in which the panel skin does not deform but the cross section of the stiffener does deform are also accounted for. The interactive PANDA system consists of three independently executed modules that share the same data base. In the first module an initial design concept with rough (not necessarily feasible or accurate) dimensions are provided by the user in a conversational mode. In the second module the user decides which of the design parameters of the concept are to be treated by PANDA as decision variables in the optimization phase. In the third module the optimization calculations are carried out. Many examples are provided in which optimum designs obtained by PANDA are compared to those in the literature. (Author).

Optimization of structural panels with respect to bifurcation buckling constraints tends to lead to imperfection sensitive panels. The panels may not represent least weight configurations if the influence of always present geometrical imperfections are taken into account. A software package, POIS (Panel Optimization with Integrated Software) was developed in response to this problem. Here user instructions are presented for Computer Program ECHO and RRSYS which are part of the POIS system. ECHO is a collection of computer programs for least weight design of stiffened structural panels subjected to multiple combinations of inplane loads. ECHO includes program modules for optimization of perfect panels and nonlinear static stress analysis of panels with random imperfections. The optimization problem is carried out as a constrained function minimization problem in which buckling loads, stress, and strain may be constraints. RRSYS is a program system for the nonlinear analysis of elastic structures by means of the Rayleigh-Ritz method. RRSYS is designed to analyze such diverse structural phenomena as collapse, linear and nonlinear bifurcation, vibrations and transient dynamic response. (Author).

An analysis and an interactive computer program are described through which minimum weight designs of composite, stiffened, cylindrical panels can be obtained subject to general and local buckling constraints and stress and strain constraints. The panels are subjected to arbitrary combinations of in-plane axial, circumferential, and shear resultants. Nonlinear material effects are included if the material is isotropic or has stiffness in only one direction (as does a discrete or a smeared stiffener). Several types of general and local buckling modes are included as constraints in the optimization process, including general instability, panel instability with either stringers or rings smeared out, local skin buckling, local crippling of stiffener segments, and general, panel, and local skin buckling including the effects of stiffener rolling. Certain stiffener rolling modes in which the panel skin does not deform but the cross section of the stiffener does deform are also accounted for. The interactive PANDA system consists of three independently executed modules that share the same data base. In the first module an initial design concept with rough (not necessarily feasible or accurate) dimensions are provided by the user in a conversational mode. In the second module the user decides which of the design parameters of the concept are to be treated by PANDA as decision variables in the optimization phase. In the third module the optimization calculations are carried out. Many examples are provided in which optimum designs obtained by PANDA are compared to those in the literature. (Author)

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Structural Analysis Systems: Software—Hardware Capability—Compatibility—Applications, Volume 1 is a practical guidebook on structural analysis systems and their applications. It provides detailed information about a specific software, its postprocessor capabilities and limitations, computer-aided design connection, and compatibility with the most common computers. Several practical examples from industry with computer and user cost are given. This volume consists of 22 chapters and begins with a brief description of the ADINA 84 system and its finite elements, material models, and solution capabilities. The discussion then turns to the analysis interpretive treatise and its database concept; the ANSYS program for engineering analysis; and the structural analysis capabilities of the boundary element analysis system BEASY. The following chapters explore other structural analysis programs such as DEFOR, FLASH, KYOKAI, PAFEC, and PANDA. General purpose finite element and boundary element computer programs for structural and solid mechanics applications are also described. This book will be a valuable resource for practitioners in scientific and industrial disciplines such as mechanical or civil engineering, informatics, applied mathematics, and computer science.

This report describes the work performed by Lockheed Palo Alto Research Labora tory, Palo Alto, California 94304. The work was sponsored by Air Force Office of Scientific Research, Bolling AFB, Washington, D. C. under Grant F49620-77-C-0l22 and by the Flight Dynamics Laboratory, Air Force Wright Aeronautical Laboratories, Wright-Patterson AFB, Ohio under Contract F3361S-76-C-31OS. The work was completed under Task 2307Nl, "Basic Research in Behavior of Metallic and Composite Components of Airframe Structures". The work was admini stered by Lt. Col. J. D. Morgan (AFOSR) and Dr. N. S. Khot (AFWAL/FIBRA). The contract work was performed between October 1977 and December 1980. The technical report was released by the Author in December 1981. Preface Many structures are assembled from parts which are thin. For example, a stiffened plate or cylindrical panel is composed of a sheet the thickness of which is small com pared to its length, breadth, and stiffener- spacing, and stiffeners the thickness of which is small compared to their _ heights and lengths. These assembled structures, loaded in compression, can buckle overall, that is sheet and stiffeners can collapse together in a general instability mode; the sheet can buckle locally between stiffeners; the stiffeners can cripple; and a variety of complex buckling interactions can occur involving local and overall deformations of both sheet and stiffeners. More complex, built-up structures can buckle in more complex and subtle ways.