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  Volume 6, Number 1, January 2021 , pages 15-30

An optimization framework for curvilinearly stiffened composite pressure vessels and pipes
Karanpreet Singh, Wei Zhao and Rakesh K. Kapania

    With improvement in innovative manufacturing technologies, it became possible to fabricate any complex shaped structural design for practical applications. This allows for the fabrication of curvilinearly stiffened pressure vessels and pipes. Compared to straight stiffeners, curvilinear stiffeners have shown to have better structural performance and weight savings under certain loading conditions. In this paper, an optimization framework for designing curvilinearly stiffened composite pressure vessels and pipes is presented. NURBS are utilized to define curvilinear stiffeners over the surface of the pipe. An integrated tool using Python, Rhinoceros 3D, MSC.PATRAN and MSC.NASTRAN is implemented for performing the optimization. Rhinoceros 3D is used for creating the geometry, which later is exported to MSC.PATRAN for finite element model generation. Finally, MSC.NASTRAN is used for structural analysis. A Bi-Level Programming (BLP) optimization technique, consisting of Particle Swarm Optimization (PSO) and Gradient-Based Optimization (GBO), is used to find optimal locations of stiffeners, geometric dimensions for stiffener cross-sections and layer thickness for the composite skin. A cylindrical pipe stiffened by orthogonal and curvilinear stiffeners under torsional and bending load cases is studied. It is seen that curvilinear stiffeners can lead to a potential 10.8% weight saving in the structure as compared to the case of using straight stiffeners.
Key Words
    pressure vessels; curvilinear stiffeners; optimization framework; finite element analysis
Karanpreet Singh, Wei Zhao and Rakesh K. Kapania:Kevin T. Crofton Department of Aerospace and Ocean Engineering,
Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, U.S.A.

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