Download AE416 Test 2 Questions With Correct Answers. and more Exams Aerospace Engineering in PDF only on Docsity!
AE416 Test 2 Questions With
Correct Answers
Assume that: 1) All materials possess ____________ 2) _______ in objects do not necessarily render it unfit for use 3) The ability to detect ________ increases with ________ size - ANSWER Flaw(s) Non Destructive Techniques: ___________________ or _____________________ - ANSWER Active or Passive Active NDT: - ANSWER Introduce energy and observe how it changes in the presence of flaws Examples of Active NDT: ______________, ______________, ______________, and ______________ - ANSWER Radiography, Ultrasonics, Magnetics, and Eddy Curent Passive NDT: - ANSWER Monitor or Observe the object of interest in "as is" state or with visually enhancing surface fluids Examples of Passive NDT: ______________, ______________, ______________, ______________, and ______________ - ANSWER Visual Examination/Inspection, Penetrant (surface), Acoustic Emission, Noise Analysis, and Leak Testing Words Nondestructive Testing (NDT), Nondestructive ______________ (NDI), and Nondestructive ______________ (NDE) - ANSWER Nondestructive Inspection and Non Destructive Evaluation What is the first step in NDE? - ANSWER Visual Inspection: Examine for defects (cracks, corrosion, dents, etc.) Damage often escapes normal vision so ______________, ______________, ______________, ______________ , and ______________ are used - ANSWER borescopes, endoscopes, microscope, binoculars, and telescopes A ______________ has an objective lens or video camera on one end, an eyepiece or videodisplay on the other, connected by a rigid or flexible tube - ANSWER borescope
______________: A type of imaging where cameras are used to detect and measureinfrared radiation that cannot be seen with the naked - ANSWER Thermography ______________: When highly accelerated electrons strike a suitable target, x- rays are produced - ANSWER Radiography Liquid Penetrant Inspection: Penetrant inspections rely upon ______________ forces and the natural accumulation of fluids around ______________ such as cracks - ANSWER capillary; discontinuities Piezoelectricity: - ANSWER Electricity or electric polarity due to pressure especially in acrystalline substance (as quartz) Pulse-Echo Inspection: - ANSWER When an ultrasonic packet of energy (e.g., pulse) strikes a surface or anomaly suchas a crack, it will be reflected much like radar, sonar, or visible light Consider a body having an equilibrium position that when displaced, experiences arestoring force causing back-and-forth motion about its equilibrium position - ANSWER oscillatory or periodic Vibration: - ANSWER A periodic motion of the particles of an elastic body or medium in alternatelyopposite directions from the position of equilibrium when that equilibrium has beendisturbed (as when a stretched cord produces musical tones or molecules in the airtransmit sounds to the ear) During damped vibration testing... - ANSWER Virtually all objects will resonate if disturbed in the right way. Very large amplitude displacements (and catastrophe) are possible Strobe Light: - ANSWER A strobe light or stroboscopic lamp is a device used to produce regular flashes of brilliant light How was the strobe light invented? - ANSWER In the late 1920's as a graduate student at the Massachusetts Institute of Technology(MIT), Harold Eugene Edgerton began investigating stroboscopy. Heat transfer (or heat) is energy in transit due to a ______________ ______________. - ANSWER temperature difference Conduction: - ANSWER The transfer of heat through matter by communication of kinetic energy from particle to particle with no net displacement of the particles
An ______________ ______________ ______________ is an electrical device that converts analog transducer output voltage to adigital number (ready for computer storage) - ANSWER Analog to Digital Converter A binary digit or "bit" can take on values of _ or _, true or false, on or off, etc.
- ANSWER 0 or 1 For a signal of bandwidth fc (highest frequency), sampling must occur at ______________ this rate or greater to capture all information contained within a signal (Nyquist, 1928) - ANSWER twice Aliasing: - ANSWER Failure to sample at a rate higher than the Nyquist rate leads to false, low frequency signals In mathematics, the ______________ series is a type of ______________ analysis, which is used on functions that might otherwise be difficult or impossible to analyze. The series decomposes a periodic function into a sum of simple functions, which may be sines and cosines or may be complex exponentials - ANSWER Fourier; Fourier In mathematics, the continuous Fourier ______________ is one of the specific forms of Fourier analysis. As such, it ______________ one function into another, which is called the frequency domain representation of the original function - ANSWER transforms; transforms What do you use for Noisy Signals? - ANSWER A Fourier transform can sometimes reveal the noisy frequencycomponents. Then low-pass, high-pass, or band-pass filters (analog or digital) can beused filter them. Intuition and common sense help too. What experiment does numerous chance observations (e.g., coin tosses, rain or shine, etc.) are made and data is collected. - ANSWER Probabilistic Experiment What is a Set of possible outcomes (N )? - ANSWER Sample Space What is Relative frequency or likelihood for a given outcome (p )? - ANSWER Probability What describes all possible outcomes and their probabilities? - ANSWER Probability Distribution Normal (Gaussian) Distribution has what type of curve? - ANSWER One of most important continuous probability distributions; the "bell-shaped curve" describes numerous observations in industry, research, and every day life
mu: mean sigma; standard deviation x: variable or outcome With the standard normal distribution, a _ value represents the number of standard deviations above or below the mean corresponding to the x it was computed from - ANSWER z No matter how carefully measurements (e.g., mass, velocity, temperature, etc.) aremade, there is always some degree of ______________ regarding their accuracy - ANSWER uncertainty What is Freedom from mistake or error; conformity to truth or to a standard or model; degree of conformity of a measure to a standard or a true value? - ANSWER Accuracy ______________: The ______________ of an instrument indicates its ability to reproduce a certain reading with a given accuracy - ANSWER Precision 2005 Chalk's Airline Miami Seaplane Crashed why? - ANSWER Wing broke off from fuselage Why did the Tacoma Narrows Bridge collapse? and when did it happen? - ANSWER Resonance vibration (oscillating in natural mode of vibration) Nov 7, 1940 What is shown in Flutter at a Glance? - ANSWER Objects breaking apart due to flutter When was the strobe light invented? - ANSWER 1931 X-Rays are what type of energy? - ANSWER electromagnetic When x-rays pass through an object, they ______________ in energy. Lead absorbs ______________ of the energy while wood absorbs ______________. This contrast is what radiograph photos are made. - ANSWER reduces; much; little What type of waves are introduced into the object for Ultrasonic testing? - ANSWER Elastic Waves What tool is often used for Ultrasonic testing? These are used to beam and capture the wave energy. - ANSWER Piezoelectric transducers Does Ultrasonics work with both solids and liquids? - ANSWER Yes
A ______________ is a temperature-sensing element made from sintered semiconductor material. It exhibits a large change in resistance proportional to a small change in temperature. ______________ usually have negative temperature coefficients which means resistance decreases as temperature increases. Highly nonlinear. - ANSWER thermistor; Thermistors Thermistors are difficult to design circuits with due to their data being nonlinear. How do you overcome this? - ANSWER The difficulty can be eased by using matched pairs of thermistors, in such a way that the nonlinearities tend to offset one another What is kinematic viscosity? - ANSWER Fluids resistance to flow under gravity ζ > 1 - ANSWER Overdamped (displaces, then moves toward equilibrium) ζ = 1 - ANSWER Critically Damped (displaces the most, but moves toward equilibrium the quickest) ζ < 1 - ANSWER Underdamped (vibrates as it moves toward equilibrium) Structural Damping - ANSWER Structure dissipates energy as it vibrates. Moving connections,fasteners, joints, etc. Standard normal distribution has a mean of _ and standard deviation of _. - ANSWER 0; 1 What equation has significant importance in the study of periodic motion and vibrations? - ANSWER a second-order, nonhomogeneous, linear differential eq with parameters m, c, and k What are the units of omega_n, the natural frequency of vibration for an undamped system? - ANSWER rad/s What is amplitude and its units? - ANSWER Distance from equilibrium in meters What happens in an overdamped system? - ANSWER over damped displaces, then moves towards equilibrium What happens in a critically damped system? - ANSWER Critically damped displaces the most, but moves toward equilibrium the quickest What happens in an underdamped system? - ANSWER Underdamped vibrates as it moves towards equilibrium
Where are resonance frequencies? - ANSWER Close to the free or damped natural frequencies Do light/stiff or heavy/compliant structures tend to resonate at higher frequencies? - ANSWER Light/stiff What fraction of exposure time allowed many photographs in the MIT lab to freeze a split second motion dead in its tracks? - ANSWER 1/10,000 sec Heat always flows from Hot to Cold - ANSWER True Law used in Conduction? - ANSWER Fourier's Law Law used in Convections? - ANSWER Newton's law of cooling Law used in Radiation? - ANSWER Stefan-Boltzmann law What is emissivity? - ANSWER Describes how efficiently a surface emits as compared to a "block body (e=1, dark/rough object)" What is a thermocouple often shielded in? - ANSWER Inside a metal or ceramic shield that protects it from a variety of environments What is an emf adjustment referred to as? - ANSWER The cold-junction (CJ) correction Hysteresis/Viscoelastic Materials - ANSWER Loaded solids absorb energy through internal friction.Rubber bands, seat cushion foams, etc. What effects do temperature changes in the wiring between the input and output ends have on voltage? - ANSWER Do not affect the output voltage, provided that the wiring is of thermocouple alloy or a thermoelectric equivalent When does the composition of the junction itself not affect the thermocouple action in any way? - ANSWER As long as the temperature, T1, is kept constant throughout the junction and the junction material is electrically conductive Law of Successive Thermocouples - ANSWER a thermocouple designated for one open-end reference temperature can be used with a different open-end temperature. Electromagnetic energy radiates from - ANSWER all matter regardless of its temperature.
