Inverse anamorphosis and multi-map techniques for free topology generation of curved self-stiffened panels using skeleton-based integral soft objects

In the present paper, an improved procedural method for the generation of curved, arbitrarily conformed self-stiffened panels using skeleton-based integral soft objects is presented. The proposed approach extends the application of integral soft objects to curved mesh surfaces by operating an inverse anamorphic mapping of special-purpose displacement fields applied orthogonally to the patched surface representing the curved structural domain. An efficient parallel procedure, able to evaluate the vector field of normals at mesh nodes of the host domain, is preliminary illustrated. Several multi-map techniques are subsequently exploited to generate arbitrary protrusions on different curved mesh surfaces, either open or closed

Multiobjective Particle Swarm Optimization technique as an effective tool for aircraft requirements analysis

In this paper, a multi-objective particle swarm optimization (MOPSO) procedure has been developed and applied in the field of aircraft requirement analysis. In order to identify useful set-up schemes for algorithm control parameters, the optimisation procedure has been preliminarily verified with test-case functions. Moreover, specific tools have been implemented to improve MOPSO effectiveness in finding Pareto front as wide and uniform as possible. The optimization procedure has been subsequently applied to the preliminary definition of a civil transport aircraft configuration. Both maximum takeoff weight and block time have been selected as objective functions to be minimized. At the end of optimization process, useful sensitivity curves, showing cruise speed requirement effects on aircraft main characteristics, have been obtained. Finally, a comparison with a similar task driven by a genetic algorithm has been performed in order to highlight some advantages offered by MOPSO procedure

Optimum topological design of simply supported composite stiffened panels via genetic algorithms

In the present paper the topological optimal design of isotropic/orthotropic thin structures performed via genetic algorithms is shown. Examples involving structural weight minimization under compressive load or buckling load maximization are presented. A modified finite strip method was developed and used to analyze parametric structures arranged in form of plates or stiffened panels with almost arbitrary cross-section shapes. Specific design variables were defined to assure a robust control over geometrical and topological features. In particular, a semi-analytical formulation for the determination of eigenvalues and eigenvectors was adopted in order to reduce computational efforts requested by the optimization task. A mesh-independent solver, involving a reduced number of degrees of freedom, was implemented and interfaced with a genetic optimizer for the purpose. The optimization procedure was based on a specific bit-masking oriented genetic algorithm, able to handle in parallel different genetic operators expressly conceived to process with proper metrics discrete and continuous design variables. As preliminary example, the buckling load maximization of a metallic plate with an arbitrary grid-shaped cross-section is described first. Then a topological optimization concerning the weight minimization of a composite stiffened panel subject to constraint about buckling load is illustrated and discussed in detail about parametric model definition and genetic procedure

Study of the structural behavior of a membrane wing: retrospective analysis of the 1917 biplane Ansaldo SVA5

In the present paper, a numerical investigation and simulation of the cable-membrane wing of the 1917 biplane Ansaldo SVA5 is shown. This activity was mainly sug-gested by a renewed interest about membrane wings, that are currently proposed for specific classes of UAV planes as MAV and HALE aircraft. The study was also performed to evaluate the structural behavior of a such type of wing configuration from an historical point of view. Preliminarily, a procedural FEM model, able to accurately describe wing geometry, topol-ogy and materials, was developed. In order to properly simulate the wing structure subjected to tensile preloads (shrinking dope effects and cable pre-tension), manoeuvre loads and ai-leron deflection, a specific solution procedure, consisting of several non linear analyses, was performed. Some preliminary results, related to fabric skin, wooden parts and steel-wire ca-bles have been finally reported in terms of overall displacements, strain and stress distribution