Aerostructure analysis WIKI project
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The document provides information about: 1) The objectives of the aeronautical engineering project, which are to teach students how to analyze load-bearing structures and various analysis methods. 2) The different types of stresses acting on structures like normal stress, shearing stress, and how they relate to forces and deformations. 3) Additional structural analysis concepts covered include truss analysis methods, strains under axial loading, temperature effects, and torsion in circular and thin-walled members.
Aerostructure analysis WIKI project
- 2. Why wiki ? A wiki is a website designed for multiple people to collaborate by adding and editing content. Aerostructure Analysis wiki is an example of a wiki. A wiki farm is a collection of individual wikis, usually hosted by the same website. Browse through a list of wikis by category
- 3. Wiki
- 4. The problems which we faced 1. When we started the project we found that having the material must be with it’s references, but we found that there is a lot of material without a references so couldn’t put it in the wiki. And we solved this problem by adding some videos and presentations instead of this unlicensed data. 2. The tools which wikispaces provide to us are too limited but somehow it was effective. 3. We couldn’t make a better design because of this limited tools and it needs $ to open this tools on wikispaces. 4. Other team members weren’t able to deal with the site and we sloved this problems by a several meetings. 5. Our logo
- 5. 1st problem and how we solved it
- 6. 2nd problem and how we solved it
- 7. 3rd problem and how we solved it
- 8. Objectives The main objective of the project about this course is to provide future aeronautical engineers with the means of analyzing and designing various load bearing structures. This can be done by learning them How to analyze a system of forces and obtain the reactions at the supports of structures and How to analyse the forces in plain trusses. Later, they will study the nature of stress and strain, and the properties of cross sections, finally, they will be introduced to the forces and stresses in members subject to axial, torsion, and bending loading.
- 9. Analysis of Trusses The method of joints: This method uses the free-body-diagram of joints in the structure to determine the forces in each member. The method of sections: This method uses free-body-diagrams of sections of the truss to obtain unknown forces.
- 11. Normal Stress and Shearing Stress Definition : - Stress is a measure of the average force per unit area of a surface within a deformable body on which internal forces act. It is a measure of the intensity of the internal forces acting between particles of a deformable body across imaginary internal surfaces
- 13. Normal Strain Under Axial Loading Normal Strain: It is the deformation in the material due to the effect of normal force on it's cross section area. It Denoted by: ε the deformation / normal length.. = It's unit: it has no unit as it is a ratio between to similar quantities. Axial Loading: It is the normal stress due to the effect of normal force affect on area. It Denoted by: σ = normal force / area It's unit: N/m2
- 15. True Stress and True Strain There are two kinds of stress; Engineering stress and True stress. Engineering stress: it is the force divided by the initial cross section area True stress: it is obtained by dividing the force by the instantaneous cross sectional area. Engineering strain: it can be obtained by the dividing of the total deformation occurred on the specimen by the initial length True strain: it can be obtained by recording the length of the specimen and determine the deformation in each record then divide this deformation on the corresponding length of the specimen and with the summation of all stains in all records (or by integration) we can get the true strain εt = ln(L/L0)
- 17. Deformations of Members under Axial Loading Consider a homogeneous (constant E) rod of length L and of cross section area A subjected to a normal force P to make in it a deformation ∆L and strain ε and stress σ , then from Hook's law σ = Eε , ε = P/AE and since ε = ∆L/L , ∆L = ε L , then ∆L = PL/AE If the rod is consists of more than one martial and of different cross section area then the total deformation on the rod is the summation of the deformation in each portion ∆L = ∑I (Pi . Li / Ai . Ei)
- 19. Statically Indeterminate Problems Statically Indeterminate Problems They are problems in which the internal forces cannot be determined from statics alone. In fact, in most of these problems the reactions themselves-which are external forces-cannot be determined by simply drawing a free-body diagram of the member and writing the corresponding equilibrium equations. The equilibrium equations must be complemented by relations involving deformations obtained by considering the geometry of the problem. Because statics is not sufficient to determine either the reactions or the internal forces, problems of this type are said to be statically indeterminate.
- 21. Problems Involving Temperature Changes Let us first consider a homogeneous rod AB of uniform cross section, which rests freely on a smooth horizontal surface. If the temperature of the rod is raised by ∆T, we observe that the rod elongates by an amount ∆L which is proportional to both the temperature change ∆T and the length L of the rod, then ∆L = α ∆T L (Note if the rod is fixed between two fixed walls then its area will increase and then it's volume also, the stain = 0 but there is stress) Where α is a constant characteristic of the material, called the coefficient of thermal expansion and it has a unit of a quantity per degree C.
- 23. Poisson's Ratio Meaning of Poisson's ratio: Poisson's ratio is the ratio of transverse contraction strain to longitudinal extension strain in the direction of stretching force. Tensile deformation is considered positive and compressive deformation is considered negative. The definition of Poisson's ratio contains a minus sign so that normal materials have a positive ratio. Poisson's ratio, also called Poisson ratio or the Poisson coefficient, is usually represented as a lower case Greek nu, ν . · Poisson ratio = - lateral strain / axial strain .
- 25. Multiaxial Loading; Generalized Hooke’s Law The generalized Hooke's Law can be used to predict the deformations caused in a given material by an arbitrary combination of stresses.
- 27. Torsion Difference between Bars and Shafts: Bars are members that are subjected to an axial loading along it's axis but Shafts are members that are subjected to twist or torque Torsion in circular Shafts Torsion in thin structures Torsion in thin walled members
- 29. Questions
- 30. Thanks for all