Optimal Design of Imperfect, Anisotropic, Ring-Stiffened Cylinders Under Combined Loads

Ley, Robert P.; Gürdal, Zafer; Johnson, Eric R.

doi:10.2514/6.1993-1526

Cited by 3 publications

(1 citation statement)

References 3 publications

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“…Other contributions to the field of buckling and postbuckling of panels include works by Weaver and his colleagues [5][6][7], Hilburger, et al [8], Baruch and Singer [9], the creators of the STAGS general purpose program, Almroth, Rankin, Brogan, and Riks [10][11][12], Arbocz and his colleagues [13][14][15], Stein [16], Leissa [17], Arnold and Parekh [18], Starnes, Knight, and Rouse [19], Spier [20,21], Khot and Bauld [22,23], Zhang and Matthews [24], Gurdal and his colleagues [25][26][27][28][29][30], Haftka and his colleagues [30][31][32], Librescu and his colleagues [33][34][35], Sridharan and his colleagues [36,37], Myers and Hyer [38], Nemeth [39], and Noor, Starnes, and Peters [40], to identify but a few in a vast literature.…”

Section: Introductionmentioning

confidence: 99%

Optimum Design of Stiffened Panels With Substiffeners

Bushnell¹,

Rankin²

2005

46th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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The capability of the computer program PANDA2 to generate minimum-weight designs of stiffened panels and cylindrical shells is enhanced to permit the adding of substiffeners with rectangular cross sections between adjacent major stringers and rings. As a result many new buckling margins exist that govern buckling over various domains and subdomains of the doubly stiffened panel or shell. These generally influence the evolution of the design during optimization cycles. The substiffeners may be stringers and/or rings or may form an isogrid pattern. The effects of local, interring , and general buckling modal imperfections can be accounted for during optimization. Perfect and imperfect cylindrical shells with external T-shaped stringers and T-shaped rings and with and without substringers and subrings and under combined axial compression, external pressure, and in-plane shear are optimized by multiple executions of a "global" optimizer called SUPEROPT. It is found that from the point of view of minimum weight there is little advantage of adding substiffeners. However, with substiffeners present the major stringers and rings are spaced farther apart at the optimum design than is so when there are no substiffeners. The weight of a cylindrical shell with substiffeners is much less sensitive to the spacing of the major T-shaped stringers than is the case for a cylindrical shell without substiffeners. The optimum designs obtained by PANDA2 are evaluated by comparisons with buckling loads obtained from a general-purpose finite element program called STAGS. Predictions from STAGS agree well with those from PANDA2.

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Section: Introductionmentioning

confidence: 99%

Optimum Design of Stiffened Panels With Substiffeners

Bushnell¹,

Rankin²

2005

46th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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Approximate method for the optimum design of ring and stringer stiffened cylindrical panels and shells with local, inter-ring, and general buckling modal imperfections

Bushnell¹,

Bushnell²

1996

Computers & Structures

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Difficulties in Optimization of Imperfect Stiffened Cylindrical Shells

Bushnell¹,

Rankin²

2006

47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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The PANDA2 computer program generates minimum-weight designs of ring and stringer stiffened flat or cylindrical composite panels subjected to multiple sets of load combinations. PANDA2 is described with emphasis on the many different stress and buckling constraints that can affect the evolution of a design during optimization cycles, on the way that imperfections are treated, on certain difficulties that imperfections may cause during optimization cycles, and on difficulties encountered during attempts to evaluate optimum designs with the use of the STAGS general purpose finite element program. Details are given on how PANDA2 determines the effect of an initial buckling modal imperfection on the load-bearing capability of a ring and stringer stiffened cylindrical shell. Numerical results pertain to a metallic cylindrical shell with external Tshaped stringers and external T-shaped rings subjected to combined axial compression, external pressure and inplane shear (torque). The maximum allowable stress is set very high so that stress constraints do not affect the evolution of the global optimum design in this example. Minimum-weight designs are determined for this shell with an initial imperfection in the form of the critical general buckling mode. Modifications to PANDA2 are described that overcome some of the difficulties associated with the determination of a global optimum design in the presence of an initial general buckling modal imperfection. Further modifications to PANDA2 are described that lead to less conservative global optimum designs than was previously the case. The optimum designs obtained by PANDA2 are evaluated by comparisons with predictions from STAGS for various finite element models generated automatically with a PANDA2 processor called STAGSUNIT. The agreement between PANDA2 and STAGS predictions for a global optimum design obtained by PANDA2 is good enough to qualify PANDA2 for the optimum design of imperfect stiffened cylindrical panels and shells under combined loads.

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Optimal Design of Imperfect, Anisotropic, Ring-Stiffened Cylinders Under Combined Loads

Cited by 3 publications

References 3 publications

Optimum Design of Stiffened Panels With Substiffeners

Optimum Design of Stiffened Panels With Substiffeners

Approximate method for the optimum design of ring and stringer stiffened cylindrical panels and shells with local, inter-ring, and general buckling modal imperfections

Difficulties in Optimization of Imperfect Stiffened Cylindrical Shells

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