Ultrasonic basics Flashcards
What is the definition of ultrasonic testing
The study and application of sound waves having frequencies higher than the human ear.
At what frequency does ultrasonics technically begin?
20khz
What is the typical ultrasound testing range?
50khz to 25 mhz.
Ultrasonic testings two primary applicatio s are?
Thickness measurement
& flaw detection.
Ultrasonic test are performed in a frequency range od A. 50khz to 25mhz B. 50khz to 5 Mhz C.5khz to 25khz. D. 25Mhz to 50Mhz.
A. 50khz to 25Mhz.
What is Dead Zone?
Discontinuities just beneath the surface may not be detectable.
True or false. Objects with unfavorable geometry or interior structure may be unsuitable for testing.
True.
Can sound propogate through solids liquids and gases
Yes.
What two properties does a medium require to vibrate.
Mass & elasticity.
What is propogating?
Ability for sound wave to travel through the material.
What does propogating through a material depend on
The nature and wavelength.
The process of sound propagation by the to and fro movenment. Of particles within a medium is called. A. Frequency B. Wavelength C. Cycle D. Vibration.
D. Vibration
Longintudinal waves require:
Elasticity.
Transverse, surface, and plate waves require?
Elasticity and rigidity.
Wave modes are defined by?
Particle motion relative to direction of sound wave energy travel.
The ability of a material to support a wave mode depends on.
Elasticity, rigidity, and vibrations.
The best phrase used to describe different ways sound waves travel is. A. Modes of difference. B. Modes of transmission C. Examples of propogation. D modes of propogation.
D. Modes of propogation.
Which type of sound wave modes will propogate through liquid? A. Longitudinal B. Transverse C. Surface D. All the above.
A. Longitudinal.
An ultrasonic wave in which particle displacement is perpindicular to direction of wave propogation is? A. Longitudinal B. Compressional C. Plane D. Transverse
D. Transverse
Sound waves that travel on the surface of a solid in a manner similar to waves on a water surface are called? A. Compressional waves B. Primary waves C transverse waves D rayleigh waves
D. Rayleigh waves.
An ultrasonic wave in which particle displacement is the same direction as wave propogation is? A. Transverse waves B. Longitudinal waves C. Surface waves. D. Plate wave
B. Longitudinal.
The three most common modes of sound vibration are?
A. Logintudinal, compressional, and transverse
B. Transverse, logintudinal, and shear.
C. Longintudinal, transverse, and rayleigh
D. Transverse, shear, and rayleigh
C. Longitudinal, transverse and rayleigh.
What sound wave modes propogate through liquid. A. Longitudinal B. Transverse C. Surface. D. All the above
D. All the above.
The only modes of vibration that can exist in liquid are? B. Shear C. Surface A. Longitudinal D. Both A and B
A. Longitudinal
What is shear wave particle movement direction?
It is at right angles or perpindicular. To the direction of propogation.
True or false. Shear waves travel only in solids?
True
The velocity of shear waves is approximately____of the velocity of logintudinal waves
1/2.
True or false angle beam transducers must be used with material they were made for.
True.
The wave amplitude at a depth of one wavelength is approximately ______ of wave amplitude on the material surface?
4%
Surface waves penetrate approximately ______ wavelength below the surface.
One
Surface waves travel in steel at approximately _______ of the velocity of shear waves or about ______ slower than shear waves.
91%, 10%
Surface waves:
A. Can exist in solids liquids and gases
B. Travel over the surface of solids exclusively
C. Travel at the same speed of longitudinal waves.
D. Travel 10 yeards before being completly attenuated.
B. Travel over the surface of solids exclusively.
Surface waves travel at a speed of around 10% less than. A. Shear waves B. Compression waves. C. Longitudinal waves. D. Plate waves
A. Shear waves
Lamb wave velocity is dependent on?
Frequency, angle, and the type of material.
The two basic mode types of lamb waves are
Symmetrical and assymetrical.
Plate waves only ocxur in thin materials _____wavelengths thick or less
3
Lamb or plate waves have two basic types. A. Symmetrical and asymmetrical B. Eliptical and plate. C. Mode 1 and mode 2 D. None of the above.
A symmetrical and asymmetrical
The wave moves in a cycle and the cycle concept can be illustrated as a?
Sine curve or sine wave.
Frequency is defined as?
The rate of vibration or number of complete waves that pass a given point in one second.
The unit of frequency is called?
Hertz
Hertz(Hz): cycles per second
Kiloherts(khz) thousands of cycles per second
Megahertz (mhz) millions of cycles per second.
What is the audible range?
The range of frequencies hear by the human ear.
The number of complete waves which pass a given point in a given period of time (usually one second) is referred to as? A. Pulse length B. Velocity. C. Wavelength D. Frequency
D. Frequency
Which of the following frequencies would provide best resolution? A. 5 mhz B.2.25 mhz C. 1mhz D. 10mhz
D. 10 mhz
A technician might use a lower\_\_\_\_\_\_\_\_ to overcome the difficulty of getting sound through the coarse grain structure of a thick casting? A. Gain setting B. Repetition rate C. Frequency D. Probe diameter
C. Frequency
Define velocity?
The speed of sound.
Expressed as distance traveled per unit of time. Like inches per microsecond
Common units of time in ultrasonics are?
Second, microsecond, and nanosecond
Calculations involving velocity can be simplified by using ________ or __________ as units
Kilometers/second or centimeter/ usec as units.
Velocity is______ in a homogeneous material.
Constant
Velocity varies from the velocity of
Refrence standard
If your refrence standard is of a different material than the test material
The measurments will be innacurate.
Velocity depends upon
Mode & material velocity & enviromental factors.
Material velocity is defined as.
Material properties of density and elasticity
Mode velocity is defined as
The wave mode such as longitudinal or shear waves
Enviromental factors are?
The temperature and sometimes air pressure and humidity of material.
A term used in ultrasonics to express the rate at which sound waves pass through a material is? A. Frequency B. Wavelength C. Velocity D. Pulse length
C. Velocity
The factors that have the greatest effect on ultrasonic velocity are?
A. The dead zone and wavelength
B. Material density, elasticity, temperature, and mode of wave.
C. The material thickness
D. The far field and wavelength
B. Material density, elasticity, temperature, and mode of wave.
All other factors being equal, which of the following modes of vibration has the greatest velocity. A. Transverse waves B. Longitudinal waves C. Shear waves D. Surface waves
B. Longitudinal waves
The velocity of a compression wave as compared to a transverse wave is approximately\_\_\_\_\_\_\_ as fast A. Four times B. Twice C. Three times D. None of the above
B. Twice
Define displacement
Otherwise known as particle displacement or displacement amplitude. ( is a measure of the distance of the movement of the particle from its equilibrum position in a medium as it transmits a sound wave.
Define crest
Part of wave with maximum value or upward displacement
Define trough
Opposite of crest so minimum or lowest point in cycle
Define amplitude
The distance from a center line or still position, to the top of crest or bottom of trough.
Wavelength is equal to?
Velocity/frequency V/F
To convert wavelength eqaution v/f you times it by?
1000
A pulse or wave train is?
A series of sound waves.
Wavelength is related to?
Frequency and sensitivity.
The shorter the wavelength the higher the_______, and the greater the_________
Frequency, sensitivity
Amplitude losses are caused by
Structure of test material
Scattering is defined as
reflection of sound by a course grain structure, impurities or fine porosity
Absorption is defined as
Conversion of sound into heat by friction among vibrating particles.
Total distance losses are a combination of
Both beam spread and sound losses from attenuation
As grain structure increases in material, its principal effect will be on? A. The velocity of sound B. The angle of refraction C. Attenuation D. The acoustic impendance
C. Attenuation
The gradual loss of acoustical energy as sound travels through the test material. Caused by factors such as grain size, fine porosity etc is called A. Penetration B. Rarefaction C. Attenuation D. Mode conversion
C. Attenuation
When wave energy is lost through absorption and the scattering of the beam within the material it is understood what is occuring. A. Attenuation B. High density obstruction C. High frequency subversion D. Molecular interferance
A. Attenuation.
Attenuation of sound in solid material is in large part due to
Grain structure and grain size of the material in question
Scattering losses are greatest where
Wavelength is less than one third of grain size.
When sound hits a acouatic interface it will either do one of two things
Transmit, reflect
An echo is a _________ from and acoustic interface
Reflection
Define acoustic interface
The boundary between two materials with two different acoustic impendances
The boundary between two materials with different acoustic properties is called? A. An acoustic dampening B. An acoustic impendance C. Rarefaction D. Acoustic interface
D. Acoustic interface.
What are symbols for this equation.
Impendance = density x velocity
Z = PxV
Acoustic impendance is determined by the:
A. Ratio of velocity to sound density
B. Product of the materials density as well as the wave velocity
C. Product of wave velocity and frequency
D. Ratio of material density to wave velocity.
B product of the materials density as well as the wave velocity
Accoustic impendance is the opposition of a material to the passage of a sound wave: True or False.
True
The higher the ratio of acoustic impendance, the greater the reflectivity of an interface between two different materials: True or False
True
Define search unit tube
Tube or mounting arm that positions transducer underwater
Define Immersion transducer
Transducer designed for use underwater
Accoustic impendance is?
The opposition that individual material particles offer to being disloged by sound
What is formula for reflected energy?
RE (z2-z1/z2+z1)^2
Due to law of conservation of energy: transmitted energy =
100% - reflected energy
Transmitted energy + reflected energy equals
Total energy
Example: if reflected energy is 88% then transmitted would be 12
Echo performance is affected by reflector
Size Shape Orientation Texture Thickness
A low impendence ratio is often called a impendance mismatch true or false
False a high impendence ratio is called such
True or false the angle of reflection is always equal to the angle of incidence
True
The process which a sound beam changes angular direction after passing through and interface between materials with different accoustic velocities is called? A. Rarefraction B. Attenuation C. Mode conversion D. Refraction
D. Refraction
The angle of reflection is equal to? A. Equal to the angle of refraction B. Dependent on the frequency used C. Dependent on the couplant used. D. Equal to the angle of incidence
D. Eqaul to the angle of incidence.
In ultrasound the term refraction refers to\_\_\_\_\_\_\_ of the sound beam as it passes from one medium to another? A. Slowing B. Acceleration C. Depletion D. Bending
D. bending
Snells law formula is?
Sin a / sin b =v1/v2
The first critical angle is?
The incident angle that causes the refracted longitudinal beam to be refracted at 90 degrees.
When the incident angle is between normal incidence and the first critical angle what will exist in test piece
Both transverse and longitudinal waves.
At the first critical angle the longitudinal or l wave is refracted at?
90 degrees
The second critical angle is?
The incident angle that causes the refracted transverse beam to be refracted at 90 degrees
The region between normal incidence and the first critical angle is not very useful for ultrasonic testing purposes. Why not?
A. The presence of two beams results in confusing reflections
B. The shear wave has not obtained peak energy at this point
C. None of the above
D. It is better to have three beams than two
A. The presence of two beams results in confusing reflections.
Refraction and mode conversion occur because the _________ of the longitudinal wave changes as the beam enters the second medium.
A. Speed.
B. Oscillation
D. Vibration
A. Speed
Which of the following may occur when and ultrasonic wave strikes and interface?
A. Reflection
B. Refraction
C. Mode conversion
D. All the above may occur depending upon the incident angle and material velocities
D. All the above
When a longitudinal wave is refracted at ninety degrees, the angle of incident longitudinal wave is called A. The mode conversion constant B. The snell angle C. The first critical angle D. The snell constant
C the first critical angle
H
C the first critical angle
When the incident angle is between 1 degree and the first critical angle
A. Only longitudinal waves are produced in the second material
B. The sound beam is tottaly reflected
C. Transverse waves and longitudinal waves are produced in the second material
D. Only transverse waves are produced in the second material
C transverse waves and longitudinal waves are produced in second material
At longitudinal wave incident angles between the first and second critical angles.
A. Only transverse waves are produced in the second material
B. Only longitudinal waves are produced in second material
C. Transverse waves and longitudinal waves are produced in second material
D. The sound beam is tottaly reflected
A. Only transverse waves are produced in the second material
As a sound wave passes at an angle through an acoustic interface, the angle of any refracted transverse wave generated is dependent upon?
A. The frequency of the incident sound wave
B. The accoustic impendances of the materials on each side of the interface
C. The velocities of the materials on each side of the interface
D. The wavelengths of the incident sound wave
C. The velocities of the materials on each side of the interface
The most useful range of incident longitudinal wave angles for angle beam ultrasonic testing is between the?
A. Normal angle of incidence and the first critical angle
B. First critical angle and the second critical angle
C. Second critical angle and the third critical angle
D. Above the third critical angle
B. First critical angle and the second critical angle.
The second critical angle is defined as the longitudinal wave incident angle which results in:
A. A refracted longitudinal wave of 90 degrees relative to the normal line
B. A refracted transverse wave of 90 degrees relative to the normal line
C. Complete reflection of the sound beam with no surface wave
D none of the above
B. A refracted transverse wave of 90 degrees relative to the normal line
The longitudinal wave incident angle which results in the formation of a surface wave is
A. Normal incidence
B. Any angle above the first critical angle
C. The second critical angle
D. The first critical angle
C. The second critical angle.
As the frequency of the ultrasonic beam increases, what happens to fresnel or near zone
Increases
Sound pressure is the greatest at the beginning of
The far field
Beam spread begins in
Far field
The end of the near field and beginning of far field is called
Yo point
As the frequency increases in ultrasonic testing the length of the fresnel zone near field? A. Remains the same B. Increases C. Decreases D. Varies uniformly
B. Increases
