The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform
Chunxiao Zhou - One of the best experts on this subject based on the ideXlab platform.
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fast procedure for non uniform optimum design of stiffened shells under Buckling Constraint
Structural and Multidisciplinary Optimization, 2017Co-Authors: Bo Wang, Kuo Tian, Gang Li, Chunxiao ZhouAbstract:For tailoring the non-uniform axial compression, each sub-panel of stiffened shells should be designed separately to achieve a high load-carrying efficiency. Motivated by the challenge caused by numerous variables and high computational cost, a fast procedure for the minimum weight design of non-uniform stiffened shells under Buckling Constraint is proposed, which decomposes a hyper multi-dimensional problem into a hierarchical optimization with two levels. To facilitate the post-Buckling optimization, an efficient equivalent analysis model of stiffened shells is developed based on the Numerical Implementation of Asymptotic Homogenization Method. In particular, the effects of non-uniform load, internal pressure and geometric imperfections are taken into account during the optimization. Finally, a typical fuel tank of launch vehicle is utilized to demonstrate the effectiveness of the proposed procedure, and detailed comparison with other optimization methodologies is made.
Bo Wang - One of the best experts on this subject based on the ideXlab platform.
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fast procedure for non uniform optimum design of stiffened shells under Buckling Constraint
Structural and Multidisciplinary Optimization, 2017Co-Authors: Bo Wang, Kuo Tian, Gang Li, Chunxiao ZhouAbstract:For tailoring the non-uniform axial compression, each sub-panel of stiffened shells should be designed separately to achieve a high load-carrying efficiency. Motivated by the challenge caused by numerous variables and high computational cost, a fast procedure for the minimum weight design of non-uniform stiffened shells under Buckling Constraint is proposed, which decomposes a hyper multi-dimensional problem into a hierarchical optimization with two levels. To facilitate the post-Buckling optimization, an efficient equivalent analysis model of stiffened shells is developed based on the Numerical Implementation of Asymptotic Homogenization Method. In particular, the effects of non-uniform load, internal pressure and geometric imperfections are taken into account during the optimization. Finally, a typical fuel tank of launch vehicle is utilized to demonstrate the effectiveness of the proposed procedure, and detailed comparison with other optimization methodologies is made.
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non probabilistic reliability based design optimization of stiffened shells under Buckling Constraint
Thin-walled Structures, 2015Co-Authors: Zeng Meng, Bo Wang, Gang Li, Kai ZhangAbstract:Stiffened shells are affected by numerous uncertainty factors, such as the variations of manufacturing tolerance, material properties and environment aspects, etc. Due to the expensive experimental cost of stiffened shell, only a limited quantity of statistics about its uncertainty factors are available. In this case, an unjustified assumption of probabilistic model may result in misleading outcomes of reliability-based design optimization (RBDO), and the non-probabilistic convex method is a promising alternative. In this study, a hybrid non-probabilistic convex method based on single-ellipsoid convex model is proposed to minimize the weight of stiffened shells with uncertain-but-bounded variations, where the adaptive chaos control (ACC) method is applied to ensure the robustness of search process of single-ellipsoid convex model, and the particle swarm optimization (PSO) algorithm together with smeared stiffener model are utilized to guarantee the global optimum design. A 3 m-diameter benchmark example illustrates the advantage of the proposed method over RBDO and deterministic optimum methods for stiffened shell with uncertain-but-bounded variations.
József Farkas - One of the best experts on this subject based on the ideXlab platform.
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8 – Welded Stiffened Cylindrical and Conical Shells
Design and Optimization of Metal Structures, 2020Co-Authors: József Farkas, Karoly JarmaiAbstract:This chapter discusses welded stiffened cylindrical and conical shells. The economy of some structural types is demonstrated by the comparison of minimum costs of different structural versions. Such a comparison has been performed for various kinds of stiffened cylindrical shells, such as ring stiffeners, external pressure, ring stiffeners, bending, stringer stiffeners, axial compression and bending, stringer stiffeners, bending, ring and stringer stiffeners, axial compression, and external pressure. The optimum design problem is solved for a slightly conical shell loaded in external pressure with equidistant ring-stiffeners of a welded square box section. The optimum number of shell segments is found, which minimizes the cost function and fulfils the design Constraints. The thickness of each shell segment is calculated from the shell Buckling Constraint. This Constraint is similar to that for circular cylindrical shells, but an equivalent thickness and segment length is used according to the DNV design rules. The dimensions of ring-stiffeners for each shell segment are determined on the basis of the ring Buckling Constraint. This Constraint is expressed by the required moment of inertia of the ring-stiffener cross-section. The cost function includes the cost of material, forming of plate elements into shell shape, assembly, welding, and painting. The fabrication cost function is formulated according to the fabrication sequence. The forming, welding, and painting costs play an important role in the total cost.
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Minimum cost design of a cellular plate loaded by uniaxial compression
Structural and Multidisciplinary Optimization, 2012Co-Authors: Karoly Jarmai, József FarkasAbstract:Cellular plates are constructed from two base plates and an orthogonal grid of stiffeners welded between them. Halved rolled I-section stiffeners are used for fabrication aspects. The torsional stiffness of cells makes the plate very stiff. In the case of uniaxial compression the Buckling Constraint is formulated on the basis of the classic critical stress derived from the Huber’s equation for orthotropic plates. The cost function contains the cost of material, assembly and welding and is formulated according to the fabrication sequence. The unknown variables are the base plate thicknesses, height of stiffeners and numbers of stiffeners in both directions. The cellular plate is lighter and cheaper than the plate stiffened on one side. The Particle Swarm Optimization and the IOSO techniques are used to find the optimum. PSO contains crazy bird and dynamic inertia reduction criteria, IOSO is based on a response surface technology.
Ilan M. Kroo - One of the best experts on this subject based on the ideXlab platform.
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Optimization of joined-wing aircraft
Journal of Aircraft, 1993Co-Authors: John W. Gallman, Stephen C. Smith, Ilan M. KrooAbstract:The joined wing is an innovative aircraft configuration with a rear wing that has its root attached near the top of the vertical tail and a tip that sweeps forward to join the trailing edge of the main wing. This study demonstrates the application of numerical optimization to aircraft design and presents a quantitative comparison of joined-wing and conventional aircraft designed for the same medium-range transport mission. The computer program developed for this study used a vortex-lattice model of the complete aircraft to estimate aerodynamic performance, and a beam model of the lifting-surface structure to calculate wing and tail weight. Weight estimation depended on a fully stressed design algorithm that included a Constraint on Buckling and a correlation with a statistically based method for total lifting-surface weight. A variety of 'optimum' joined-wing and conventional aircraft designs are compared on the basis of direct operating cost, gross weight, and cruise drag. Maximum lift and horizontal tail Buckling were identified as critical joined-wing design issues. The addition of a Buckling Constraint is shown to decrease the optimum joined-wing span and increase direct operating cost by about 4%. The most promising joined-wing designs were found to have a joint location at about 70% of the wing semispan, a fuel tank in the tail to trim, and a flap spanning 70% of the wing. These designs are shown to cost 3% more to operate than a conventional configuration designed for the same medium-range mission.
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Structural Optimization for Joined-Wing Synthesis
Journal of Aircraft, 1992Co-Authors: John W. Gallman, Ilan M. KrooAbstract:The joined wing is an innovative aircraft configuration with a rear wing, or horizontal tail, that is attached near the top of the vertical tail and sweeps forward to join the trailing edge of the main wing. This study evaluates two structural design methods for application in an aircraft synthesis code and quantifies the differences between these methods for joined wings in terms of weight, stress, direct operating cost, and computational time. A minimum weight optimization method and a fully stressed design method are used to design joined-wing structures. Both methods determine the sizes of 204 structural members, satisfying 1020 stress Constraints and five Buckling Constraints. Monotonic splines are shown to be a very effective way of linking spanwise distributions of material to a few design variables. Five beam Buckling Constraints for the horizontal tail are included in both design methods. Without this Constraint on Buckling, the fully stressed design is shown to be very similar to the minimum weight structure. Adding a beam Buckling Constraint for the horizontal tail increased the structural weight by 13% and produced a fully stressed design that is 0.9% heavier than the minimum weight structure. Using the minimum weight optimization method to design the structure and to save 0.9% in weight required 20 times the computational time. Furthermore, the minimum weight structure produced only a 0.02% savings in direct operating cost. This study suggests that a fully stressed design method based on nonlinear analysis is adequate for a joined-wing synthesis study. The same joined wing considered in this study was shown, in an earlier study, to be slightly more expensive to operate than a conventional configuration designed for the same medium range transport mission. Since the same fully stressed design method was used in this earlier study, this work supports the comparisons of joined-wing and conventional aircraft performance presented in the earlier study. Of course, a different set of mission specifications and design assumptions may produce joined wings that perform significantly better.
Joowon Kang - One of the best experts on this subject based on the ideXlab platform.
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Design of Buckling constrained multiphase material structures using continuum topology optimization
Meccanica, 2019Co-Authors: Quoc Hoan Doan, Dongkyu Lee, Jaehong Lee, Joowon KangAbstract:This study contributes to a possibility of evaluating composite structures configuration such as steel and concrete using Buckling and volume Constraints based on multi-material topology optimization. A Jacobi active-phase algorithm is used to generate multiphase topology optimization. It provides a rational solution appropriated to the topology optimizer, Method of Moving Asymptotes due to the conflict in updating the design variables. A modified material interpolation scheme solving spurious Buckling modes problem which occurs in the multi-material topology optimization process is given and discussed. An investigation of Buckling Constraint parameter is described. It allows a single-objective minimum compliance topology optimization to obtain two objectives of maximizing both structure stiffness and first Buckling load factor. The optimal changing topologies of single material structure and multi-material structure corresponding to different Buckling Constraints are presented. Numerical examples of compression-only structures and compression-tension structures considering structural instability are performed using both single material and multiple materials to verify the efficiency and superiority of the present method.