Download or read book Optimal Design of Geodesically Stiffened Composite Cylindrical Shells microform written by Guy Gendron and published by Ann Arbor, Mich. : University Microfilms International. This book was released on 1991 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimal Design of Geodesically Stiffened Composite Cylindrical Shells written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-27 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: An optimization system based on the finite element code Computations Structural Mechanics (CSM) Testbed and the optimization program, Automated Design Synthesis (ADS), is described. The optimization system can be used to obtain minimum-weight designs of composite stiffened structures. Ply thickness, ply orientations, and stiffener heights can be used as design variables. Buckling, displacement, and material failure constraints can be imposed on the design. The system is used to conduct a design study of geodesically stiffened shells. For comparison purposes, optimal designs of unstiffened shells and shells stiffened by rings and stingers are also obtained. Trends in the design of geodesically stiffened shells are identified. An approach to include local stress concentrations during the design optimization process is then presented. The method is based on a global/local analysis technique. It employs spline interpolation functions to determine displacements and rotations from a global model which are used as 'boundary conditions' for the local model. The organization of the strategy in the context of an optimization process is described. The method is validated with an example. Gendron, G. and Guerdal, Z. Unspecified Center NASA-CR-190706, NAS 1.26:190706, CCMS-92-23, VPI-E-92-20 NAG1-643...

Download or read book Optimal Design of Geodisically Stiffened Composite Cylindrical Shells written by G. Gendron and published by . This book was released on 1992 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Monthly Catalog of United States Government Publications written by United States. Superintendent of Documents and published by . This book was released on 1993 with total page 1072 pages. Available in PDF, EPUB and Kindle. Book excerpt: February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index

Download or read book Monthly Catalogue United States Public Documents written by and published by . This book was released on 1993 with total page 1786 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design Aids for Stiffened Composite Shells with Cutouts written by Sarmila Sahoo and published by Springer. This book was released on 2016-09-16 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the free vibrations of graphite-epoxy laminated composite stiffened shells with cutout both in terms of the natural frequencies and mode shapes. The dynamic analysis of shell structures, which may have complex geometry and arbitrary loading and boundary conditions, is solved efficiently by the finite element method, even including cutouts in shells. The results may be readily used by practicing engineers dealing with stiffened composite shells with cutouts. Several shell forms viz. cylindrical shell, hypar shell, conoidal shell, spherical shell, saddle shell, hyperbolic paraboloidal shell and elliptic paraboloidal shell are considered in the book. The dynamic characteristics of stiffened composite shells with cutout are described in terms of the natural frequency and mode shapes. The size of the cutouts and their positions with respect to the shell centre are varied for different edge constraints of cross-ply and angle-ply laminated composite shells. The effects of these parametric variations on the fundamental frequencies and mode shapes are considered in detail. The information regarding the behavior of stiffened shells with cutouts for a wide spectrum of eccentricity and boundary conditions for cross ply and angle ply shells may be used as design aids for structural engineers. The book is a significant contribution to the existing literature from the point of view of both industrial importance and academic interest.

Download or read book Optimal Design of Ring Stiffened Cylindrical Shells Using Multiple Frame Sizes written by Michael Pappas and published by . This book was released on 1978 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the solution to the singly reinforced discrete stiffener problem by direct use of an optimization scheme employing mathematical programming. The optimization formulation and procedure used here admit a large number of simultaneous buckling modes thus allowing optimization under conditions of mode coalescence, which are usual in this type of problem. This is a preliminary study, the purposes of which are; to develop and evaluate methodology for the treatment of this problem, to develop preliminary insights into how multiple frame sizes may efficiently be employed in submersible structures, to examine the nature of design improvement resulting from use of multiple size frames, and to investigate the nature of such optimal designs. (Author).

Download or read book Optimal Design of Cylindrical Shells written by Peter Nestler and published by . This book was released on 2009 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimal Design of Laminated composite Circular cylindrical Shells Subjected to Combined Loads written by Guojun Sun and published by . This book was released on 1988 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimal Design of Cylindrical Shells written by Percy Po Hei Yuen and published by . This book was released on 2002 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Finite Element Analysis of Geodesically Stiffened Cylindrical Composite Shells Using a Layerwise Theory written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-24 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Layerwise finite element analyses of geodesically stiffened cylindrical shells are presented. The layerwise laminate theory of Reddy (LWTR) is developed and adapted to circular cylindrical shells. The Ritz variational method is used to develop an analytical approach for studying the buckling of simply supported geodesically stiffened shells with discrete stiffeners. This method utilizes a Lagrange multiplier technique to attach the stiffeners to the shell. The development of the layerwise shells couples a one-dimensional finite element through the thickness with a Navier solution that satisfies the boundary conditions. The buckling results from the Ritz discrete analytical method are compared with smeared buckling results and with NASA Testbed finite element results. The development of layerwise shell and beam finite elements is presented and these elements are used to perform the displacement field, stress, and first-ply failure analyses. The layerwise shell elements are used to model the shell skin and the layerwise beam elements are used to model the stiffeners. This arrangement allows the beam stiffeners to be assembled directly into the global stiffness matrix. A series of analytical studies are made to compare the response of geodesically stiffened shells as a function of loading, shell geometry, shell radii, shell laminate thickness, stiffener height, and geometric nonlinearity. Comparisons of the structural response of geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells are provided. In addition, interlaminar stress results near the stiffener intersection are presented. First-ply failure analyses for geodesically stiffened shells utilizing the Tsai-Wu failure criterion are presented for a few selected cases. Gerhard, Craig Steven and Gurdal, Zafer and Kapania, Rakesh K. Langley Research Center NASA-CR-200288, NAS 1.26:200288 NAG1-1085...

Download or read book Optimization of Thin wall Cylindrical Shells with Compliant Cellular solid Cores written by Matthew Aaron Dawson and published by . This book was released on 2005 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) The weight optimization of the structure identifies the optimum ratio of the core modulus to the shell modulus and is supported by a Lagrangian optimization technique. The design of natural, thin-wall structures with cellular cores is compared to the analytical optimal, and the deviation about the theoretical optimum is explored. The analysis also discusses the selection of materials in the design of the cylinders with compliant cores, identifying the most suitable material combinations. The performance of a cylinder with a compliant core is compared with competing designs (optimized hat-stiffened shell and optimized sandwich-wall shell). Furthermore, experiments comparing the performance of a cylindrical shell with a compliant core to that of an equivalent hollow shell are performed in uniaxial compression; the experimental results supporting the analysis are presented, demonstrating significant improvement over the equivalent hollow shells. Finally, the challenges associated with achieving the optimal design in practice are discussed, and the potential for practical implementation is explored.

Download or read book Structural Optimization and Design Senstitivity of Composite Cylindrical Shells for Buckling and Postbuckling written by Jay Michael Ferreira and published by . This book was released on 1992 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Imperfection Insensitive Thin Shells written by Xin Ning and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The buckling of axially compressed cylindrical shells and externally pressurized spherical shells is extremely sensitive to even very small geometric imperfections. In practice this issue is addressed by either using overly conservative knockdown factors, while keeping perfect axial or spherical symmetry, or adding closely and equally spaced stiffeners on shell surface. The influence of imperfection-sensitivity is mitigated, but the shells designed from these approaches are either too heavy or very expensive and are still sensitive to imperfections. Despite their drawbacks, these approaches have been used for more than half a century. This thesis proposes a novel method to design imperfection-insensitive cylindrical shells subject to axial compression. Instead of following the classical paths, focused on axially symmetric or high-order rotationally symmetric cross-sections, the method in this thesis adopts optimal symmetry-breaking wavy cross-sections (wavy shells). The avoidance of imperfection sensitivity is achieved by searching with an evolutionary algorithm for smooth cross-sectional shapes that maximize the minimum among the buckling loads of geometrically perfect and imperfect wavy shells. It is found that the shells designed through this approach can achieve higher critical stresses and knockdown factors than any previously known monocoque cylindrical shells. It is also found that these shells have superior mass efficiency to almost all previously reported stiffened shells. Experimental studies on a design of composite wavy shell obtained through the proposed method are presented in this thesis. A method of making composite wavy shells and a photogrametry technique of measuring full-field geometric imperfections have been developed. Numerical predictions based on the measured geometric imperfections match remarkably well with the experiments. Experimental results confirm that the wavy shells are not sensitive to imperfections and can carry axial compression with superior mass efficiency. An efficient computational method for the buckling analysis of corrugated and stiffened cylindrical shells subject to axial compression has been developed in this thesis. This method modifies the traditional Bloch wave method based on the stiffness matrix method of rotationally periodic structures. A highly efficient algorithm has been developed to implement the modified Bloch wave method. This method is applied in buckling analyses of a series of corrugated composite cylindrical shells and a large-scale orthogonally stiffened aluminum cylindrical shell. Numerical examples show that the modified Bloch wave method can achieve very high accuracy and require much less computational time than linear and nonlinear analyses of detailed full finite element models. This thesis presents parametric studies on a series of externally pressurized pseudo-spherical shells, i.e., polyhedral shells, including icosahedron, geodesic shells, and triambic icosahedra. Several optimization methods have been developed to further improve the performance of pseudo-spherical shells under external pressure. It has been shown that the buckling pressures of the shell designs obtained from the optimizations are much higher than the spherical shells and not sensitive to imperfections.

Download or read book Optimal Design of Cylindrical Shells Under Strength Constraints written by Babur Yakar and published by . This book was released on 1992 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Data Collection on Geometry and Design Loads for Stiffened Cylindrical Shells in Marine Structures written by S. Valsg°ard and published by . This book was released on 1980 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Legal Aspects of Space Commercialization written by Kunihiko Tatsuzawa and published by . This book was released on 1992 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: