Faculty of Engineering and Built Environment
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Item Multiobjective optimization of laminated plates for maximum prebuckling, buckling and postbuckling strength using continuous and discrete ply angles(Elsevier., 1996) Adali, Sarp; Walker, Mark; Verijenko, Viktor E.The optimal design of uniaxially loaded laminated plates subject to elastic in-plane restraints along the unloaded edges are given for a maximum combination of prebuckling stiffness, postbuckling stiffness and buckling load. The results are also obtained for biaxially loaded plates without elastic restraints. The method of solution involves defining a design index comprising a weighted average of the objective functions and identifying candidate configurations which have to be optimized and compared to determine the best stacking sequence. This multiobjective approach leads to improved prebuckling, buckling and postbuckling performance. A similar approach is adopted in the case of discrete ply angles with the provision that these angles can only take predefined values. From a manufacturing viewpoint, using only certain fibre orientations such as 0, ± 45 and 90 ° is advantageous and cost-effective. The multiobjective design results are compared to single objective ones, and the effect of various problem parameters on the optimal designs are numerically studied. It is observed that the resulting trade-off among the different objectives are not severe leading to well-balanced laminates with regard to the range of loads they are required to carry. A comparison of continuous and discrete optimization indicates that both designs lead to comparable load carrying capacity, with regard to different objectivesItem Optimization of symmetric laminates for maximum buckling load including the effects of bending-twisting coupling(Elsevier, 1996) Walker, Mark; Adali, Sarp; Verijenko, Viktor E.Finite element solutions are presented for the optimal design of symmetrically laminated rectangular plates subjected to a combination of simply supported, clamped and free boundary conditions. The design objective is the maximization of the biaxial buckling load by determining the fibre orientations optimally, with the effects of bending-twisting coupling taken into account. The finite element method coupled with an optimization routine is employed in analysing and optimizing the laminated plate designs. The effects of boundary conditions, the number of layers and bending-twisting coupling on the optimal ply angles and the buckling load are numerically studied.Item Refined theory of laminated anisotropic shells for the solution of thermal stress problems(Taylor & Francis, 1999) Verijenko, Viktor E.; Tauchert, T. R.; Shaikh, C.; Tabakov, Pavel Y.A new higher order theory of laminated anisotropic shells for the solution of thermal stress problems that takes into account transverse shear stresses is developed.The theory is based on the kinematic hypotheses that were not assumed a priori but derived on the basis of an iterative technique. The hypotheses take into account the influence of the tangential components of the external loads and the temperature on distributions of the transverse shear stresses through the thickness of the shell. Some analytical solutions are obtained on the basis of the theory developed, and the results are compared with those available in the literature. The theory is also implemented on the basis of the finite element method, and a new triangular finite element is formulated. Some numerical results on the basis of this finite element are also presented.Item Optimal design of symmetrically laminated plates for maximum buckling temperature(Taylor & Francis, 1997) Walker, Mark; Reiss, Talmon; Adali, Sarp; Verijenko, Viktor E.The optimal designs of laminated plates subject to nonuniform temperature distributions are givenfor maximum bucklingtemperature. The method ofsolution involves the finite element method based on Mindlin plate theory and numerical optimization: A computational approach is developed that involves successive stages of solution for temperature distribution, buckling temperature, and optimalfiber angle. Three different temperature loadingsare consideredand various combinations of simply supported and clamped boundary conditionsare studied. The effectofplate aspectratioon the optimal fiber angle and the maximum buckling temperature is investigated. The influence of bending-twisting coupling on the optimum design is studied by considering plates with an increasing number of layers.Item Optimal design of symmetric angle-ply laminates subject to nonuniform buckling loads and in-plane restraints(Elsevier, 1996) Walker, Mark; Adali, Sarp; Verijenko, Viktor E.Optimal buckling designs of symmetrically laminated rectangular plates under in-plane uniaxial loads" which have a nonuniform distribution along the edges are presented. In particular, point loads, partial uniJorm loads and nonuniform loads" are considered in addition to uniform O' distributed inplane loads" which provide the benchmark solutions. Poisson's effect is" taken into account when in-plane restraints are present along the unloaded edges. Restraints give rise to in-plane loads" at unloaded edges which lead to biaxial loading, and may cause premature instability. The laminate behaviour with respect to fiber orientation changes significantly in the presence of Poisson's eJfi, ct as compared to that o/'a laminate where this" ~Jfect is neglected. This change in behaviour has significant implications Jor design optimisation as the optimal values of design variables with or without restraints differ substantially. In the present study, the design objective is" the maximisation of the uniaxial buckling load by optimally determining the fiber orientations. The )qnite element method, coupled with an optimisation routine, is employed in analysing and optimising the laminates. Numerical results are given for a number of boundary conditions and fi)r uniJormly and non-uniformly distributed buckling loads.