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*AEROSPACE STRUCTURES*)

The student who successfully completes the course will have the ability to compute the distribution of stress for typical aerospace structures (wing-boxes, fuselages) adopting the elementary theory approach and the forces method; will be able to demonstrate a solid knowledge of the buckling behavior of compressed structures; will be aware of the energetic approaches to the study of structural problems; will be aware of the approach to structural problems based on the use of the finite element method.

The evaluation is based primarily on the verification of the basic knowledge necessary for the study of aerospace structures (equilibrium, shear flow and normal stress computation in thin walled structures). The uncertainty of these skills is not allowed. Also the knowledge of buckling phenomena and the knwoledge of methods for the solution of buckling problems represent an important part of the preparation and evaluation of the student. The uncertainty of these skills is not allowed. The examination is based on the solution of exercises and on a subsequent discussion of the results and, if it is necessary, on the discussion of some theoretical aspects.

Methods:

- Final oral exam.

*Course Contents*

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*( PART I ) - Basic Structural Analysis - Statics (October-December) *

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*Introduction to structural mechanics.*

*Beams in bending, shear and torsion.*

*Principles of aerospace structures construction*

*Bending, shear and torsion of thin-walled tubes*

*Stresses in multi-cell tubes*

*Discrete models of aerospace structures (wing-box, fuselage): elementary theory*

*Correction of the elementary theory results*

*Second order approach: shear diffusion and axial constraint effects in the aerospace structures*

*Matrix method of structural analysis (Force Method and Displacements Method)*

*( PART II ) - Analysis of Aerospace Structures - Statics (February-April)*

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*Introduction to the use of PATRAN-NASTRAN codes (computer lab)*

*Energy methods of structural analysis*

*Theory of thin plates*

*Theory of structural instability (buckling of beams, plates and stiffened panels)*

*Crippling of compressed structures (crippling of beams, plates and stiffened panels)*

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*( PART III ) - Introduction to Structural Dynamics (May) *

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*Introduction to the use of PATRAN-NASTRAN codes (computer lab)*

*Notes and exercises on the single-degree-of-freedom system*

*Analysis of multi-degrees-of-freedom systems*

*Notes to the dynamics of continuous systems (bending and torsional vibrations of beams)*

*Modal analysis of structural systems*

*Notes and exercises on the energy methods for the dynamic analysis of structures*

*Only** Erasmus students can subdived the examination phase into two distict parts. The examination for all the other students consists in a full exam.*

*For Erasmus students:*

*Exams for the PART I (January-February)*

*Exams for the PART II or Full exams (June-July)*

Students should have the ability to use and/or perform the following:

- Vector and tensor notation
- Concepts of stress and strain
- Basics of the elasticity theory
- Isotropic constitutive relations
- Classic Beam Theory

Theoretical lessons and, in the second period, use of personal computer for the preparation of Finite Element models by Nastran-Patran codes.

Delivery: face to face

Attendance: Advised

Learning activities:

- attending lectures
- participation in seminar
- individual study
- Laboratory work

Teaching methods:

- Lectures
- Task-based learning/problem-based learning/inquiry-based learning
- laboratory

The theory of elasticity: two-dimensional problems (stress function method). Elementary theory of thin walled beams (shear, bending and torsion). Study of lumped parameters structures (models of wing-boxes and fuselages). Shear diffusion and warping of thin walled beams. Lumped parameters structures as undetermined systems. Matrix methods: the forces method and the displacement method. Finite Element Analysis. Statics of plates and membranes. Global buckling of compressed beams: bending, torsion, bending and torsion. Buckling of compressed plate. Local buckling of compressed beams. Buckling of compressed stiffened panels. Crippling of both compressed beams and compressed stiffened panels. Dynamic analysis: modal analysis of discrete and continuous systems (cables and beams).

*Spacecraft Structures and Mechanisms** T.P. Sarafin, 1995*

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*Aircraft Structures for Engineering Students** T.H.G. Megson, 1972*

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*Theory and Analysis of Flight Structures** R.M. Rivello, 1969*

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*Theory of Elasticity**S.P. Timoshenko, J.N. Goodier, 1970*

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*Mechanics of Materials** S.P. Timoshenko, J.M. Gere, 1972*

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*Introduction to Structural Dynamics and Aeroelasticity** D.H. Hodges, 2002*

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*Lectures and Exercises of Aerospace Structure L. Boni **( e-learning)*

Recommended reading includes the following works: T.H.G. Megson "Aircraft Structures for Engineering Students" R.M. Rivello "Theory and analysis of flight structures" E. F. Bruhn "Analysis and design of flight vehicle structures" S. P. Timoshenko, J. N. Goodier "Theory of Elasticity" O. A. Bauchau, J. I. Craig "Structural Analysis: with application to aerospace structures"

A good skill in the solution of structural problems, using a critical approach and efficient methods for the discretization of problems, allows the student to approach engineering problems not only in the field of aerospace structures.