1 / 14

2145-392 Aerospace Engineering Laboratory II Vibration of Beam

2145-392 Aerospace Engineering Laboratory II Vibration of Beam. by NAV. Vibration of Beam. 1. Motivation 2. Introduction/Theory 3. Objectives 4. Apparatus. 1. Motivation Aircraft Vibration. Engine Pump Landing gear extension and retraction Extension of speed brakes Wing.

edric
Download Presentation

2145-392 Aerospace Engineering Laboratory II Vibration of Beam

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2145-392 Aerospace Engineering Laboratory IIVibration of Beam by NAV 2145-392 NAV 2013

  2. Vibration of Beam • 1. Motivation • 2. Introduction/Theory • 3. Objectives • 4. Apparatus 2145-392 NAV 2012

  3. 1. MotivationAircraft Vibration • Engine • Pump • Landing gear extension and retraction • Extension of speed brakes • Wing • Normal? Low Vibration, background noise, turbulence • Abnormal? Engine rotor imbalance, malfunction of mechanical equipment, and airflow disturbances acting over doors 2145-392 NAV 2012

  4. Aircraft Wing Vibration • Flutter is an unstable condition in which unsteady aerodynamics excite near or at the natural frequencies of the structure over which the air flows. • The resulting vibrations can grow to a magnitude that causes the structure to fail. • Wing Fluttering 2145-392 NAV 2012

  5. Aircraft Wing Vibration • If the aircraft’s structure is low damped, it means that the various natural frequencies of different parts of the aircraft’s structure do not dampen out and thus can ‘flutter’. • In worst case scenarios flutter is a potentially dangerous condition in which the vibrations of various parts of the structure become divergent – leading to structural failure • Flutter testing is important as it evaluates the aircraft’s stability and dampening modes at limit speeds and high altitude 2145-392 NAV 2012

  6. 2. Introduction/Theory Vibration is the branch of engineering that deals with repetitive motion of mechanical systems. Examples: • engineering structure to earthquakes 2145-392 NAV 2012

  7. 2. Introduction Vibration Related Examples: • unbalanced rotating machine -> shut-down, failure • plucked string of a musical instrument -> sound • ride quality of an automobile or motorcycle -> stiff, smooth 2145-392 NAV 2012

  8. 2. Theory Only the most important features are considered in the analysis to predict the behavior of the system under specified input conditions. The analysis of a vibrating system usually involves • Step 1: Physical modeling • Step 2: Mathematical modeling = derivation of the governing equations • Step 3: Solving the equations • Step 4: Interpreting of the results (numerical, graphical, etc). • Can we go backwards? Graphical results  equation? 2145-392 NAV 2012

  9. 2. Theory Three basic elements in a simplified vibrating system • the element restoring or releasing KE • mass or a mass moment of inertia • the element restoring or releasing PE • an elastic component or a spring • the element dissipating energy • Damper 2145-392 NAV 2012

  10. 2. Theory  • These elements are related to the behaviors of the system subjected to various kinds of excitation • To analyze the vibration problem, the quantities of these elements must be determined via some measurements. • The natural/resonance frequencies are then calculated. 2145-392 NAV 2012

  11. 2. Introduction How important are these quantities? When the excitation frequency meets the resonance frequency / when the excitation is large • BIG vibration • Structural Failure See movies • The Chinook resonances • The MD-80 landing 2145-392 NAV 2012

  12. 3. Objectives • To determine values of the basic quantities of a simplified beam system i.e. the stiffness of the spring and the damping coefficient of a damper through experiments by observing the time response [displacement vs time graphs]. • To study the vibration behavior of the system when the conditions/parameters vary. • Ultimate goal: To understand the vibration characteristics of a simplified aircraft wing and apply the understanding to (partially) design of wing structure 2145-392 NAV 2012

  13. Modeling Wing flutters due to excitation e.g. from wind Simplify the model of the wing as a beam Continuous system with structural stiffness and damping Physical model turns into a math model with a governing partial differential equation Simplify more and make the mass “lumped” together Simplify even more to get one rigid beam pivoted at the end with a spring and a damper 2145-392 NAV 2012

  14. 4. Apparatus The vibration testing apparatus “Universal Vibration” It represents physical plants including rigid and flexible beams subjected to an unbalance force available free and damped vibration. 2145-392 NAV 2012

More Related