07 Sept 17 - Structures 3

07 Sept 17 - Structures 3 - AOE 2104-Aerospace and Ocean...

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AOE 2104--Aerospace and Ocean Engineering Fall 2009 Virginia Tech September 17 2009 Aircraft Structures 3 Click to edit Master subtitle style AOE 2104 Introduction to Aerospace Engineering Aircraft Structures 3
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AOE 2104--Aerospace and Ocean Engineering Fall 2009 Virginia Tech September 17 2009 Aircraft Structures 3 Talked about the concept of stress and strain Looked at different stress types Saw how stress and strain are related Introduced the concept of elasticity and plasticity Any questions? Last time…
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AOE 2104--Aerospace and Ocean Engineering Fall 2009 Virginia Tech September 17 2009 Aircraft Structures 3 What is a factor of safety? To what degree does the structure exceed maximum expected load Known as a “multiplier” Why do we need one? We have normal operations effects but also: Material property degradation due to environmental effects Isolated effects such as hard landing, extreme turbulence Uncertainty in modeling Creates a structure which is very unlikely to fail under expected conditions How is it defined? A design parameter picked to relate design limit load to design ultimate load Must be > 1 for a viable structure! First, look at factor of safety . . S F x load limit Design load ultimate Design =
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AOE 2104--Aerospace and Ocean Engineering Fall 2009 Virginia Tech September 17 2009 Aircraft Structures 3 Ultimate load Maximum load where the structure does not fail Structure generally never sees this load in it’s lifetime Limit load Maximum load where structure shows no permanent deformation One which should occur only once or few times during a component’s lifetime These are connected through the Factor of Safety For commercial aircraft F.S. is usually around 1.5 This is a design value These rules are mandated by the FAA Aircraft go through extensive testing procedures to become “certified” but of course this does not just include structures What are ultimate load and maximum limit load?
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This note was uploaded on 04/04/2010 for the course ESM 2214 taught by Professor Lesko during the Spring '10 term at Virginia Tech.

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07 Sept 17 - Structures 3 - AOE 2104-Aerospace and Ocean...

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