UT1 Flash Cards
Waves used in ultrasonic testing of materials are __ in nature.
Mechanical
In a longitudinal wave, zones of compression alternate with __ zones?.
Rarified
Elastic waves can be transmitted in?
a) air
b) water
c) solids
d) all of the above
The smallest distance between two points on an elastic wave where
the particles are in the same state of motion is the
Wavelength
The maximum displacement of a particle from its point of rest in
a sound wave is its
Amplitude of movement
Particle motion in a longitudinal wave is
parallel to the direction of wave propagation
In transverse waves, particle motion is
right angles to the direction of wave propagation
Rayleigh waves are a phenomenon associated with
a) solid to liquid boundaries
b) solid to air boundaries
c) solid to solid boundaries
d) all of the above
Surface waves limited on two surfaces are also called
lamb waves
Rayleigh, shear and longitudinal describe
wave modes
In general, the result of two waves interacting on each other can
be found by
vector addition
The point where no particle displacement occurs on a standing
wave is called
a node
The point where maximum particle displacement occurs on a
standing wave is called
an antinode
Wavelength of sound is determined by
(velocity) / (frequency)
Compared to water, the acoustic impedance of steel is
higher
2,500,000 cycles per second (cps) is also expressed as
2.5 MHz
The product of acoustic velocity times the density of a material
gives
acoustic impedance
In steel, shear wave velocity as compared to longitudinal wave
velocity is about
one half as fast
The usual form of denoting acoustic impedance is
Z
If a material borders on empty space the interface is called
a free boundary
In determining the coefficient of reflection, a negative value
indicates
phase reversal relative to the incident wave
Phase reversal of an ultrasound wave upon reflection from a
sonically softer material is indicated by
a negative R value
Incidence of a sound wave from a solid to a gas is considered a
free boundary condition because
the acoustic impedance of a gas is essentially zero
Bending of a sound wave upon entering a new medium is explained
by
Snells’s law
If a sound beam is incident on steel from water at 20 degrees,
the refracted transverse wave will have an angle
greater than 20 degrees
The change from longitudinal to transverse waves (and visa versa)
at a boundary is called
mode conversion
The incident angle at which the transmitted longitudinal wave
first ceases to exist in the defracting medium is called the
first critical angle
The incident angle at which the transmitted transverse wave first
ceases to exist in the refracting medium is called the
second critical angle
The critical angle for the longitudinal wave is also called the
first critical angle
The critical angle for the transverse wave is also called the
second critical angle
Mode conversion in ultrasonics occurs at
all boundaries
For a longitudinal wave entering a medium of lower acoustic
velocity, the refracted longitudinal wave angle in the new
material will be
less than incidence angle
The law of reflection requires that
The angle of reflection equals the angle of incidence
The normal to the reflecting surface, the reflected ray and incident ray lie in the same plane
The “bending” of sound waves at gaps and openings is accounted
for by
diffraction
According to geometric-optic treatment of sound, acoustic
pressure
decreases with distance from source
Reflection and refraction phenomenon are illustrated in
geometric-optic treatment of ultrasound by means of
rays and straight lines
In practical ultrasonic testing, mirror surfaces can be used with
sound beams to
reach points of difficult access
The interference pattern produced in front of a transducer face
is a result of
diffraction
The distance from the probe face to the last main maximum on the
beam axis is called the
near field
Acoustic pressure fluctuates in the near zone due to
diffraction interference
A longitudinal wave generating transducer will have a given near
field in steel. If in water the near field for this probe will
be
about 4 times as long
Acoustic pressure along the beam axis moving away from the probe
has various maxma and minima due to interference. At the end of
the near field pressure is
a maximum
Beyond the near zone of an ultrasound beam from a probe is the
far field
Variations in acoustic pressure at right angles to the probes’
sound beam in the near zone are a result of
side lobes
The angle of divergence is
applicable to the far zone only
The “main lobe” of a rectangular probe is
broader in the small probe dimension
Focusing of ultrasound is accomplished by
curved piezoelectric crystals &
lenses
Difficulties determining exact lateral location and relative size
of a flat reflector in the near zone result from
multiple maxima and minima
AVG (or DGS in English) diagrams are used for
estimating flaw size
Flaw detection using the through transmission method can give
accurate information about
a) flaw depth
b) flaw type
c) flaw orientation
d) none of the above
In ultrasonic testing, a wave pulse contains
a range of frequencies
The main contribution to loss of sound pressure of a beam
incident on a rough surface is provided by
scatter
More scatter of a sound beam is had when using
higher frequency probes
For best results detecting a defect that may be irregularly
shaped and slightly off perpendicular to the beam, the wavelength
used should be
as large as possible to locate the defect
In ultrasonic testing by pulse-echo method, the sound waves off
the probe are
a range of frequencies
Higher frequency probes are not preferred for inspection of
castings due to
scatter
Sound reduction over a distance can be accounted for by
a) absorption
b) scatter
c) beam spreading
d) all of the above
Attenuation of ultrasound by absorption is a result of
heating
For a plane wave, sound pressure is reduced by attenuation in a
_______ fashion.
exponential
If a signal on your CRT is 28% FSH and 6 dB gain is added to the
receiver amplifier the signal will be _______ FSH.
a) 34%
b) 42%
c) 56%
d) 70%
If a signal is reduced from 84% to 42% FSH, the number of dB
gain removed from the receiver is
a) 2
b) 6
c) 12
d) 42
typical maximum thickness range for inspecting forged steel by
ultrasonics is
1 to 10 m
As temperature of a solid increases the attenuation of sound in
that object tend to
increase
Scatter is more likely to be a problem if
grain size is large
Scatter of ultrasound at grain boundaries is a result of
differences in elastic properties
Scatter generally increases with
a) increasing grain size
b) decreasing wavelength
c) increasing frequency
d) all of the above
In ultrasonic testing a piezoelectric material is used to
convert mechanical energy to electrical energy
The piezoelectric material first used for ultrasonic transducers
is
Na Cl
X-cut quartz crystal transducers are cut with active element face
at right angles to the
X-axis
Shifts of the positive charge on the silicon and negative charge
on the oxygen in a quartz crystals account for
the piezoelectric effect
In order to generate mechanical displacements (ultrasound waves)
in a X-cut piezoelectric crystal we must
apply an alternating voltage
Applied voltage on a piezoelectric crystal used in a transducer
requires ________ to cause mechanical displacement
electrodes
The fundamental frequency of a piezoelectric crystal used in
ultrasonics is a function of
its thickness
&
the velocity of sound in the crystal material
The ratio of vibration amplitude at resonance frequency to the
amplitude of static thickness change is called
Q factor
large Q factor indicates
narrow bandwidth
Resonance peaks at frequencies of odd numbered multiples of the
resonance frequency are called
harmonics
In pulse-echo testing there is an advantage to using short pulses
to excite the transducer because
the dead zone is decreased
&
the frequency spectrum is broadened
Of the various materials used for transducer crystals, lithium
sulphate hydrate is the most critical because it
looses its water of crystallization above 130 degrees C
A PZT transucer will loose its piezoelectric property if
heated above its curie point
In addition to a low critical temperature, lithium sulphate
hydrate
is soluble in water so must be water proofed
Methods of generating and receiving ultrasound by deformation of
ferromagnetic materials in a magnetic field utilize the
phenomenon called
magnetostriction
Magnetostrictive principles can be used
for transmitting ultrasound
&
for receiving ultrasound
Mechanical methods of ultrasound generation
a) utilize electro-mechanical hammers
b) utiltize rotating wire brushes
c) require no coupling liquids
d) all of the above
The method whereby sound is transmitted through a plate from a
transmitter on one side to a receiver on the other
is called an intensity method
Pulse-echo ultrasonic testing is used for
a) thickness testing
b) flaw detection
c) acoustic velocity determinations
d) all of the above
Using the pulse echo method with a 0 degrees probe (single
crystal) on a flat steel plate 50mm thick, the pattern on the CRT
would appear as
evenly spaced multiples
When testing thick specimens, it may be advisable to
decrease the pulse repetition frequency
In immersion testing you would normally position the
entrance echo on the left of the CRT
Transmitter voltage pulse is triggered by the
control pulse of the sweep generator
For flaws immediately below the surface the best option is
TR or twin crystal probes
The normal presentation of ultrasonic signals on an ultrasonic
machine used in NDT is
rectified form
If not equipped with a frequency selecter for the reciever
amplifier an ultrasonic machine would probably use a (an)
broadband receiver
Threshold adjustment is applied to
“clean up” the noise on the baseline
Electrode material on the piezoelectric crystal faces, typically
evaporated to about 1000 angstroms thick, is made of
a) gold
b) silver
c) chrome/gold
d) all of the above can be used
Boron, aluminum oxide and sapphire are often used in transducers
as
wear faces
In contact testing using angle beam probes with removable wedges,
the purpose of groves in the front of the wedge is
absorb internally reflected sound
The most commonly used wave mode for angle beam testing is
transverse
Unless otherwise noted, the refracted beam angle on a perspex
wedge is the refracted angle in
steel
Angle beam wedges can be used to generate surface waves only if
the refracted shear wave is 90ø
A property of the receiver amplifier that is periodically
verified is
vertical linearity
The purpose of the IIW block is to determine
Information obtained about the exit point and refracted angle of an angle beam probe
must be check periodically since the probe is subject to wear
The IIW block is used primarily
for contact probes
A system that electronically monitors an echo signal in a gate such that an alarm is triggered if the signal exceeds a predetermined amplitude is called a/an
go / no-go system
The preferred presentation method for determining the amplitude of a echo signal is the
A-scan
Resonance testing methods are used for
thickness testing
Thickness readings from ultrasonic testing can be indicated by
For immersion testing, surface scale and rust can be removed by
In contact testing best probe contact is made on __ surfaces.
Flat
Uniformity of coupling is verified by the operator monitoring
For normal ultrasonic contact testing of forged carbon steel and aluminum the optimum frequency range of transducers is
2 to 5 MHz
High frequency transducers, over 10 MHz, have
When a longitudinal wave is directed along the length of a large solid shaft from an end of the shaft, sensitivity to defects fluctuates as the probe is moved from the centre to the outside
edge of the shaft. This is accounted for by
interfering edge effects
When performing contact angle beam testing interferring surface waves can be distinguished from flaws by
touching the work surface with an oily finger
When inspecting a thin flat plate with a 60ø shear wave probe it
is possible to see both top and bottom corners of the plate when
the beam is aimed at the plate edge. This is due to
beam spread
When scanning a test plate with angle beam probes, the operator can often determine the front and backwall position on the screen from
“grass mounds”
In plate testing with angle beams, the full skip distance refers to
twice the sound path to the opposite wall thickness
For an ultrasound beam to skip in the circumferential direction of a tubular product
The delta technique uses
A transmitting probe and receiving probe on the same side of the test piece
Surface wave ultrasonic testing is superior to penetrant testing because it
can find sub-surface defects
Flaw size is often determined by
If the sound beam strikes a flaw at right angles and the flaw has a greater area than the beam it will
at like a backwall
Although ingots of metal are often difficult to test by ultrasonics due to large dimensions and scatter due to grain size, it is useful to locate
gross piping
Which of the following plate defects would not be a result of in-service use?
laminations
Production line testing of high pressure ribbed tubing would use
which ultrasonic technique?
immersion testing from the inside diameter
The common metric term Hertz (abb.Hz) is used to indicate
cycles per second
With a sound velocity of 1.5mm/æs in water, the wavelength of the ultrasonic disturbance in water provided by an ultrasonic cleaning machines’ 40 kHz transducer is
37mm
The 3 essential elements common to all systems that use ultrasonic devices are
power source, transducer, convertor
The incident angle at which the longitudinal mode is refracted at
90ø is
the first critical angle
The number of nanoseconds in 2 milliseconds is
2 X 10^6
When a piezoelectric material has a voltage applied to it
mechnanical deformation occurs
To a degree, the mechanical deformation of a piezoelectric material is directly proportional to the
applied voltage
So as to be utilized as ultrasonic transducers, ferroelectric ceramics must
Most piezoelectric ceramics (ferroelectrics) are
polycrystalline
When ferro electric ceramics such as PZT are heated to above their curie point and held under a bias voltage while cooling to 80øC they are considered
poled or polarized
When using quartz as a piezoelectric transducer, longitudinal waves are generated from the
X - cut
The advantage of quartz crystals over ceramic materials for ultrasonic transducers is
Although quartz has about twice the receiving sensitivity of PZT, PZT used for pulse-echo testing in NDT results in higher amplitude signals for the same conditions because
transmission constant is higher
Lithium sulphate as a transducer material is most notable for its
high solubility in water
A positive valve of a reflection coefficient indicates
no phase change has occurred
A negative value of a reflection coefficient indicates
180ø phase change
The purpose of highly absorptive backing material in transducers
used for testing is to
eliminate sound re-entering the crystal
Short highly damped pulses of ultrasound have their advantage in NDT in that
time measurement accuracy is improved
A material that exhibits dimensional changes in a magnetic field is said to be
magnetostrictive
Which of the following is not a magnetostrictive material
PZT
The advantage of magnetrostrictive transducers is
Standing waves in any medium are result of
interference from reflections
An acoustic lens for focusing ultrasound at a specific point in front of the transducer is made as thin as possible so as to
minimize absorption
Focusing of ultrasound energy is accomplished by
The purpose applying ultrasound to a weld puddle during electric arc welding is to
create a finer grain structure and increase tensile strength
Ultrasonics used for drilling or machining has the advantage that
complex shapes can be cut out in a single pass
If a 1 MHz quartz crystal (cut for half-wave resonance) is 0.29 cm thick, how thick would it have to be if the half-wave resonance frequency was to be 10 MHz?
0.29 mm
Using the through transmission method of ultrasonic testing
no flaw echo is seen
The advantage of a longer path length in the standard perspex wedge of a common contact-angle beam transducer is
improved near surface resolution
Increased damping on a piezoelectric element results in
You are given a cube of material 20mm thick. By pulse-echo immersion testing you determine the multiples of this material to be separated by 6.9 microseconds, the longitudinal velocity of sound in the material is
5800 m/s
Given a cube of iron (long. velocity = 5800 m/s), pulse-echo multiples are seen every 100 microseconds. What is the thickness of the iron?
29 cm
The difference between a thickness gauge and a distance gauge is
the range that is measured
The incremental fine gain control of the ultrasonic instrument is
calibrated in
1 or 2 dB increments
Delay” on the ultrasonic machine is used to
correct for proper zero point
Most codes would recommend the actual beam angle of an angle beam
probe not deviate from the indicated angle by more than
two degrees
When performing contact weld inspection the purpose of doing a
normal beam inspection of the parent metal adjacent to the weld is
The best way to determine the required sensitivity for ultrasonic
testing is
use reference welds with real defects of the minimum acceptable size
Which of the following is not a consideration when choosing a
couplant for ultrasonic testing
nominal test frequency
In weld inspection, the longitudinal wave inspection of the plate adjacent to the weld is usually done using a frequency in the range of
2-6 MHz
The size and shape of ultrasonic probes used are determined
primarily by
the specific application
Attenuation is not a result of
beam geometry
Probe index, refracted angle, timebase and sensitivity are
usually calibrated using
calibration and or reference blocks
When using angle beams (transverse waves) for ultrasonic testing, the position of a flaw signal on the timebase can be calibrated
for
Which is not a commonly used target when establishing sensitivity for ultrasonic testing?
a tungsten ball
The gain required to compensate for differences in coupling efficiency between a reference or calibration block and the work piece is called
transfer correction or transfer value
The purpose of moving a contact angle beam probe back and forth
perpendicular to the axis of the weld inspected is to
ensure full volumetric inspection of weld and heat affected zone
In weld inspection, transverse cracks are best located by
scanning parallel to the weld axis
The recommended refracted angle for contact shear wave inspection of plate less than 10mm thick is
70ø
The position of a defect found by an angle beam inspection
requires that you know
The length of a defect is calculated from
lateral probe movement
Manual probe movement in contact scanning to evaluate a defect for type is
always a combination of all of the above
To improve the accuracy of defect location and evaluation you should
use a probe of higher frequency
Amplitude response of a defect is not influenced by
Maximum amplitude response of a planar defect will usually be had
when
its main surface is perpendicular to the sound beam
Reference reflectors in calibration blocks are normally cylindrical holes because
they are not as directionally dependant
When drawing a distance/amplitude curve (DAC) you set the signal from the reference hole which gives the maximum amplitude to
80% - 90% FSH
When contact testing is performed, a transfer value is
if the beam from an unfocused probe strikes a convex steel surface from water with normal incidence it will
increase beam spread
If the beam from an unfocused probe strikes a concave steel surface with normal incidence from water it will
decrease beam width
Severity of a defect is determined by
The result of a rough test surface in ultrasonic testing is
The effect of increasing the temperature of a test piece to 30
degrees C. is to
decrease acoustic velocity
The ability to separate individual defects lying closely together is called
resolution
A calibration block can be used to
When establishing the relative sensitivity of higher power longitudinal wave probes on the methyl polymethacrylate insert of
the IIW block
When using the IIW Block #1, the probe exit point is established using the
100mm radius
When calibrating for an inspection range of 0 to 100mm with an angle beam probe, delay on the instrument must be
adjusted to correct for the time delay in the perspex wedge
The main advantage of the Rompas or DIN block (IIW block 2) is
portability
When using the large IIW Block #1, what are the fewest number of reflections you would need to use to calibrate a longitudinal probe for 100mm range?
2
When using the large IIW Block #1, what are the fewest number of reflections from the 100mm radius in order to calibrate a 70 degree shear wave probe for a 100mm range?
2
The use of flat bottom holes for a reference standard when testing forgings is a reasonable method of flaw assessment because
they are a good representation of the flat defects found in forgings
Flat bottom hole test blocks are made
Maximum sensitivity of a transducer is found at the
end of the near zone
A flat normal beam probe has a near zone of 25mm in water. If used in direct contact on steel the near zone would be
6mm
Attenuation of ultrasonic energy is an inherent property of all materials and is
variable with alloy and test frequency
A focused probe is positioned in water 5 cm over a plate 10cm thick. The probe having a focal length of 6 cm will focus
0.25 cm from the entry surface of the plate
In ultrasonic testing the term sensitivity usually refers to the
test system’s ability to discern
the smallest size defect
When performing a pulse-echo test, if you scanned over a large defect with the same acoustic impedance as the material you were testing
it would not be detected
Modern ultrasonics uses signal processing methods like signal
averaging, spectral analysis, deconvolution auto-correlation and
filtering to
both locate and characterize flaws
In ultrasonic spectrum analysis, the effect of increasing metal grain size on the spectra would be
reduction in higher frequencies
When trying to obtain a “noise free” signal a filter is sometimes used. If this filter limits signals to just a narrow range of frequencies it is called a __ filter.
band-pass
In ultrasonic testing, one of the best means of conveying a large quantity of information about a test piece is by
ultrasonic imaging
Acoustic imaging techniques permit the visualization of objects because
acoustic waves obey the same equations as optical waves
Ultrasonic waves with frequencies of 400MHz to 2GHz would be used
in
acoustical microscopy
If the “focal spot” size of the beam from a focused transducer was increased by increasing the focal length
resolution would decrease
In nondestructive testing the acronym EMAT stands for
electromagnetic acoustic transducer
When performing contact ultrasonic testing, significant amplitude variations from the same indication can result from
The advantage of a short duration excitation pulse applied to a
normal transducer is
Generally, longitudinal waves propagate__.
faster than shear waves
For a single crystal piezoelectric material used in an ultrasonic
transducer the angle to the crystal axis that it is cut determines
direction of deformation
Alignment of the small domains in polycrystalline ferro-electric materials, such as PZT, is called
In a ferroelectric ceramic such as PZT, the curie temperature is the temperature above which
the piezoelectric domain structure is lost
In some ultrasonic probe arrangements, one variety of piezo
material is used for the transmitter and another for the receiver. The purpose of two different materials is
to optimize relative efficiencies of transmitter and receiver elements
The parallel of mechanical resonance frequency of a piezoelectric
element occurs when the element thickness is
one half wavelength
Backing materials used in ultrasonic transducers are used for
changing frequency bandwidths
The purpose of putting one or more matching layers between the front face of a probe and the coupling medium is
to improve coupling
The result of spherical or “cup shaped” lens on the front of an
ultrasonic probe is a(n)
point focused beam
Variations in a probes’ actual frequency and its nominal frequency by as much as 5%
are acceptable in NDT
Electromagnetic acoustic transducers (EMATs) are made from
coils of wire
Mechanical deformation of a material placed in a magnetic field is called
magnetostriction
The most common single measurement made on ultrasonic transducers is determination of
nature of sound field
Velocity of ultrasonic waves in steel at 10øC. as compared to 40øC. are
faster
Using an unrectified A-scan presentation the dominant frequency can be determined provided you know the
time interval on the baseline
Pulse length determines a probes’
depth resolution
The purpose of determining signal-to-noise ratio is
necessary to ensure small flaws do not go undetected
Another term for the suppression control on an ultrasonic machine is
reject
Probes used in ultrasonic contact testing are checked
periodically for performance when in regular use. Which characteristic would not be checked daily?
beam profile
A deviation in actual refracted angle of + or - 2 degrees will result in
When using perspex wedges for contact testing, if the actual refracted angle varies by more than + or - 2 degrees the wedge should be
The method of non-destructive testing which uses acoustic energy usually in the 1MHz to 5 MHz range is
ultrasonic testing
The testing of materials to detect internal, surface and
concealed defects or discontinuities by methods which do not damage or destroy the material under test is called
non-destructive testing
In ultrasonic testing, the display in which pulse amplitude is represented as a displacement along one axis and time as a displacement along the other axis is called a(n)
A-scan
The product of density an acoustic velocity is
acoustic impedance
The number of oscillations per second experienced by a particle as an acoustic wave passes through it is called the
acoustic frequency
The angle at which an ultrasonic beam spreads in the far zone is called the
angle of divergence
A contact probe which introduces an ultrasonic wave into a test piece so that the beam angle in the test piece is a some angle other than 0 or 90 degrees to the normal is called a(n)
angle probe or angle beam probe
The control on an ultrasonic machine which enables electrical signals to be decreased by known values, usually dB, is called a(n)
attenuator
The line of maximum sound intensity in the far zone of an ultrasonic beam, and its projection back to the near zone is called the
beam axis
In ultrasonic testing, the distance travelled along the beam axis is called
beam path length
A compression wave probe is used to generate and/or receive
longitudinal waves
Material attached to the rear of an ultrasonic crystal to
increase damping is called
crystal backing
A presentation where-by the relative amplitude of ideal reflectors of different sizes are plotted against different distances is called
The dominant frequency of an ultrasonic flaw detection system depends on the
A probe constructed such that the ultrasonic waves converge at a point or line is a(n)
focused probe
The amount by which the electrical signal from the ultrasonic transducer is amplified is
the gain
Gain and attenuator controls on an ultrasonic machine are usually calibrated in
decibels
A probe specially designed to be used totally under water is called a(n) __ probe.
immersion
Background indications seen on an A-scan, arising from material characteristics and/or electrical noise is termed
grass
The method whereby the test piece is either wholly or partially under water or other such coupling fluid is called
immersion testing
In an A-scan presentation, the indication of the instant at which the pulse is applied to the transmitting crystal is the __ indication.
initial pulse
The phenomenon whereby a longitudinal wave generates waves of other modes upon reflection or refraction is
mode conversion
Acoustic or electrical interference in ultrasonic testing is often called
noise
The short wave-train produced on each excitation of an ultrasonic transducer is a(n)
pulse
An echo received from a reflector of known size and
characteristics could be termed a
reference echo
Spreading the timebase interval to enable signals from a selected range to be displayed is called
scale expansion
The distance between successive points of impingement of the beam axis on the entry surface after reflecting from the opposite side
is called
skip distance
The display generated so that distance along a horizontal axis is proportional to time is a(n)
time base
The imaginary line that connects all the points of the same phase in a wave propagating in a medium is referred to as the
wave front
The plastic prism coupled between and ultrasonic transducer and a test piece which causes the ultrasonic waves to propagate at a known angle within the test piece is called a
wedge
Which of the following methods would not use pulsed ultrasound?
When using the “pitch-catch” method of ultrasonic testing, which is not true?
all the piezoelements are mounted in one housing
Sizing of defects located in the near zone is difficult because of
A rough surface may affect resolution and sensitivity by
Maximum acoustic energy is coupled from one medium to another when the acoustic impedance of the first medium is __ the second.
the same as
Which of the following terms is not used to describe methods of coupling ultrasonic energy into a test specimen?
non-invasive
In immersion testing, the hindrance of multiple interface signals that results from the pulse bouncing between the test piece and probe on normal incidence is avoided by
increasing the distance between probe and work surface
Which mode of wave used in nondestructive testing is not initially produced by mode conversion?
longitudinal
Resonance methods of thickness testing are no longer commonly used. This technique utilized
continuous wave oscillators
To avoid distortion of received ultrasonic signals the receiver amplifier should have similar bandwidth characteristics as the
receiving transducer
Transducers with high-Q factor have
poor resolution compared to low-Q factor
In hardcopy presentations of C-scans, the item recorded is
If you wanted to determine the depth a large surface breaking crack extending into a plate you were inspecting using an angle beam, you would need to know
Significant advantage of ultrasonics over radiography is
it is safe
Which is not a characteristic of ultrasound used to evaluate materials
density
In ultrasonic testing, attenuation studies are
used to study some properties of materials
Surface wave testing would be used to detect
fatigue cracks in helicopter blades
Which is not a welding defect term
lamination
The most common method of ultrasonic testing of welds is
angle beam
The orientation of the defect with respect to the direction of the ultrasonic beam determines
whether the reflected pulse returns to the receiver
To inspect tubular products using the ultrasonic method,
all wave modes can be used
Production line ultrasonic inspection of tubular test pieces is done by
any of the above can be used depending on the specifics of the application
Tubing ie. tubular products, is best inspected by ultrasonics using the __ method.
pulse-echo
Thickness measurements of plates are made using __ waves.
compressional
The purpose of water jets in ultrasonic inspection of hot plate (100øC.) is
The principles involved in testing non-metals by ultrasonics as compared to metals are
essentially the same
Ultrasonic testing of concrete would be carried out using frequencies in the range of
25 to 100 kHz
Rubber tires can be inspected by ultrasonic means but it requires lower frequencies in the range of 50 kHz because
of attenuation from scatter off the fibres
Ultrasonic pulse-echo techniques are used on livestock to
establish fat profiles
Ultrasonics has been applied in
Given a 10 MHz probe vibrating into water, with a velocity of 1.5 mm/æs, what is the wavelength of the longitudinal wave
0.15 mm
Given a 2.5 MHz transducer radiating ultrasound into glycerin, what is the wavelength of the shearwave in the glycerin?
Given a 2 MHz PZT crystal coupled to steel at an angle of incidence of 3ø, what is the wavelength of the shearwave in steel if V long is 5.9mm/æs and V shear is 3.2mm/æs?
1.6 mm
Given a 4 MHz probe radiating normally into copper, V long = 4.7 km/s V shear = 2.3km/s, the wavelength of the longitudinal wave is
1.18 mm
A plane longitudinal wave strikes a water-steel interface from water ( V long water=1.5Km/s V long steel= 5.9km/s V shear steel=3.2km/s ) at normal incidence. Having had a 2mm wavelength in water it will result in the shear wave wavelength being
none of the above, a shear wave does not occur
The probe movement that maintains a constant distance from an
indication while varying the direction of the beam is called
orbiting
The divergence of an ultrasonic beam is dependent on:
Transducer wavelength and diameter
When a longitudinal wave is incident upon an inclined interface between zero degrees
and the first critical angle
Shear waves and longitudinal waves are produced in the second material
The piezoelectric material in a search unit which vibrates to produce ultrasonic waves
is called
A transducer element or crystal
When a longitudinal wave is incident upon an inclined interface and is refracted at
ninety degrees, the angle of the incident longitudinal wave is called
The mode conversion constant
When a longitudinal wave sound beam passes through an acoustic interface at some
angle other than zero degrees:
Reflection, refraction and mode conversion will occur
Which of the following can be a source of spurious ultrasonic signals?
(a) Surface roughness of the test piece
(b) Mode conversion within the test piece
(c) Shape or contour of the test piece
(d) All of the above
A noisy base line, or hash may result in:
Large grain size
Sound waves which travel on the surface of a solid in a manner similar to waves on a
water surface are called:
Rayleigh waves
Lamb waves are formed in a part which has
A thickness approximately equal to the wavelength
Which type(s) of sound wave modes will propagate through liquids?
Longitudinal
When the motion of the particles of a medium is transverse to the direction of
propagation, the wave being transmitted is called a
Shear wave
Which of the following test frequencies would generally provide the best penetration
in a 12 inch thick specimen of coarse-grained steel?
1.0 MHz
An oscilloscope display in which the screen base line is adjusted to represent the one
way distance in a test piece is called a
B scan display
A common use of ultrasonic testing is
Detecting of sub-surface indications
Sound waves of a frequency beyond the hearing range of the human ear are referred
to as ultrasonic waves or vibrations, and the term embraces all vibrational waves of
frequency greater than approximately
20 kHz
Y cut crystals produce
Shear waves
The cable that connects the ultrasonic instrument to the search unit is specially
designed so that one conductor is centred inside another. The technical name for such a cable is:
Coaxial cable
As ultrasonic frequency increases
Wavelength decreases
In an A scan presentation, the amplitude of vertical indications on the screen
represents the
Amount of ultrasonic sound energy returning to the search unit
Loss of the test piece back wall echo during scanning may be caused by
A discontinuity which is not parallel to the entry surface
When a sound beam is reflected
The angle of reflection equals the angle of incidence
Which of the following circuits converts electrical energy to ultrasonic energy?
The transducer
An instrument display in which the horizontal base line represents elapsed time and
the vertical deflection represents signal amplitudes is called
A scan
Which of the following circuits provides short duration, high energy pulses which are
used to excite the transducer?
The pulse generator
A cross section view of a test piece is produced by which of the following?
B scan
Echo amplitude losses may be caused by
(a) Entry surface roughness
(b) Coarse grain size
(c) Discontinuity orientation
(d) All of the above
Which of the following is an advantage of using a focused transducer?
Greater sensitivity is achieved in the transducer’s useable range
Which of the following circuits provide current to operate the ultrasonic instrument?
The power supply
Which of the following is a true statement?
Thicker crystals produce lower frequency transducers
Which type(s) of sound wave modes will propagate through solids?
(a) Longitudinal
(b) Shear
(c) Surface
(d) All of the above
The longitudinal wave incident angle at which the refracted shear wave angle equals
ninety degrees is called?
The second critical angle
The amount of beam divergence from a crystal is primarily dependent on
the:
Frequency and crystal size
In ultrasonic testing, a liquid coupling medium between the crystal surface and the part surface is necessary because :
An air interface between the crystal surface and the part surface would almost
completely reflect the ultrasonic vibrations
X cut crystals produce:
Longitudinal waves
Lower frequency transducers are normally used:
Where deeper penetration is required
All other factors being equal, which of the following modes of vibration has the
greatest velocity?
Longitudinal wave
In immersion testing, the position of the search unit is often varied to transmit sound into the test part at various angles to the front surface. Such a procedure is referred to as:
Angulation
The angle of a refracted shear wave generated as a sound wave passes at an angle through an acoustic interface is dependant on:
The acoustic impedances of the materials of each side of the interface
Which of the following is a likely effect of a rough test piece surface?
Loss of discontinuity signal amplitude
Wavelength is:
The distance from trough to trough or from peak to peak of a sound wave
The velocity of surface waves is approximately _______________ the velocity of shear waves in the same material.
Nine-tenths
An ultrasonic instrument control which allows moving an A scan display to the left or right without changing the distance between any echoes displayed is called:
The sweep delay
A disadvantage of using natural quartz crystals in a search unit is that:
It is the least effective generator of ultrasonic energy of all commonly used
materials
The formula Sin A/Sin B = VA/VB is known as:
Snell’s law
A 25 MHz search unit would most likely be used during:
Immersion testing
A technique in which two transducers are used, one on each side of the test piece, is
called:
Through transmission testing
Sound beam intensity is irregular in the area called:
The near field
A more highly damped transducer crystal results in:
Better resolution
The process of comparing an instrument or device with a standard is called:
Calibration
Scattering of an ultrasonic beam is most pronounced when:
Material grain size and wavelength are comparable
Ultrasonic testing is:
Sound which has a frequency or pitch above the range of the human ear
Which technique would most likely be used to examine a weld, with the weld cap still in place?
Angle beam testing
The maximum frequency usually used for contact testing is:
5 MHz
Higher frequency transducers are normally used:
In immersion testing applications
Typical ultrasonic testing frequencies are:
1 MHz to 5 MHz
‘25 million cycles per second’ can also be stated as:
25 MHz
A disadvantage of using a high frequency ultrasonic transducer is:
It is scattered more by coarse grained material
Which of the following circuits provides timing signals to the pulser?
The clock
Which of the following search units would contain the thinnest quartz crystal?
A 25 MHz search unit
With longitudinal wave incident at angles between the first and second critical angles:
Only shear waves are produced in the second material
Sound velocity is described by which of the following relationships?
Wavelength times frequency
The relationship between the longitudinal wave incident angle and the refracted shear wave angle is defined by:
Snell’s law
Acoustic impedance is defined by which of the following relations?
Material density × velocity
The upper limit of human hearing is normally considered to be about:
20 kHz
Reference standards containing a series of flat bottom holes of the same diameter at
different depths in each block are called?
Distance-amplitude blocks
During ultrasonic testing by the immersion method, it is frequently necessary to
angulate the search unit when a discontinuity is located at an angle in order to:
Obtain a maximum response if the discontinuity is not originally oriented
perpendicular to the ultrasonic beam
Which of the following transducer materials is the most efficient receiver of
ultrasonic energy?
Lithium sulphate
An ultrasonic wave in which particle displacement is 90 degrees to the direction of wave propagation is called a:
Shear wave
An advantage of using lithium sulphate in search units it that:
It is one of the most efficient receivers of ultrasonic energy
Moving a search unit over a test surface either manually or automatically is referred to as:
Scanning
Which of the following materials of the same alloy is most likely to produce the
greatest amount of sound attenuation over a given distance?
A coarse grained casting
The ability to separate echos from reflectors close together in depth is called:
Resolution
Greater depth of penetration in coarse grained material may be achieved using:
Lower frequencies
Lower frequency transducers produce:
Deeper penetration, less attentuation and greater beam spread
Spurious indications might be caused by which of the following?
Mode conversion from beam spread in a long specimen
The portion of a test piece which is represented by the CRT screen area from zero to the rightmost edge of the initial pulse is called:
The near field
The depth of penetration of surface waves is approximately:
One wavelength
An ultrasonic test using a straight beam contact search unit is being conducted
through the thickness of a flat part such as a plate. This test should detect:
Laminar-type flaws with major dimensions parallel to the rolled surface
The first critical angle is defined as the longitudinal wave incident angle which results
in:
A refracted longitudinal wave of ninety degrees
The number of complete waves which pass a given point in a given period of time
(usually one second) is referred to as the:
Frequency of a wave motion
The speed of sound in a given material depends on:
The density and elasticity of the material
A screen pattern containing a large number of low-level indications (often reffered to as ‘hash’) could be caused by:
Coarse grained material
In an A scan presentation, the horizontal base line represents the:
Elapsed time or distance
In a basic ultrasonic test pattern (A scan) for contact testing, the initial pulse (assume no sweep delay is used):
Is the high indication on the extreme left side of the screen that represents the
entry surface of the inspected part
An ultrasonic instrument control which is used to expand or contract the horizontal
base line of an A scan display is called:
The sweep length or range control
A term used in ultrasonics to express the rate at which sound waves pass through
various substances is:
Velocity
Transducer focal lengths are normally specified as:
Distance in steel
The second critical angle is defined as the longitudinal wave incident angle which
results in:
A refracted shear wave of ninety degrees
Spurious or nonrelevant indications might be suspected if:
Indications are unusually consistent in amplitude and appearance
A disadvantage of lithium sulfate as a transducer material is that:
It is soluble in water
An advantage of using a ceramic transducer in search units is that:
It is one of the most efficient generators of ultrasonic energy
The three most common modes of sound vibration are:
Longitudinal, transverse and rayleigh waves
A larger diameter crystal results in:
Less beam spread
Entry surface resolution is a characteristic of an ultrasonic testing system which
defines its ability to:
Detect discontinuities located just beneath the entry surface in the part being
tested
Higher frequency transducers produce which of the following?
Greater sensitivity, resolution and attenuation
In immersion testing, verification that the search unit is normal to a flat entry surface
is indicated by:
Maximum reflection from the entry surface
Which of the following is true?
Wavelength=velocity/frequency
Most commercial ultrasonic testing is accomplished using frequencies between:
15 and 100 MHz
The longitudinal wave incident angle which results in formation of a rayleigh wave is
called:
The second critical angle
An ultrasonic testing technique in which the transducer element is not parallel to the test surface is called
Angle beam testing
In the same material, shear wave velocity is:
Approximately 1/2 longitudinal wave velocity
Another name for a compression wave is a:
Longitudinal wave
Under most circumstances, which of the following frequencies would result in the
best resolving power?
25 MHz
The most useful range of incident longitudinal wave angles for ultrasonic testing is:
Normal incidence to the first critical angle
Ultrasonic testing of material where the search unit is in direct contact with the
material being tested may be:
(a) Straight beam testing
(b) Surface wave testing
(c) Angle beam testing
(d) All of the above
The echo on the cathode ray tube (CRT) which represents the far boundary of the
material being tested is called:
The back wall echo
A standard block which can be used to calibrate an instrument for an angle beam
range calibration is:
V1/A2 block
The ability to detect echos from small reflectors is called:
Sensitivity
When the motion of the particles of a medium is parallel to the direction of
propagation, the wave being transmitted is called a:
Longitudinal wave
In contact testing, the entry surface indication is sometimes referred to as:
The initial pulse &
The ‘main bang’ or transmitter pulse
A second name for Rayleigh waves is:
Surface waves
Sound beam intensity decreases expontentially with distance in the area called:
The far field
A test method employing two seperate search units on opposite surfaces of the
material being tested is called:
Through-transmission testing
Which of the following is not (!) a requirement of a couplant?
Highly penetrating
A plan view representation of a test piece is produced by which of the following?
C scan
A widening of the front surface indication, when testing a rough surface, is caused by:
A partial reflection of ultrasonic beam side lobe energy
When a vertical indication has reached the maximum signal height which can be
displayed or viewed on the CRT of an ultrasonic instrument, the indication is said to have reached its:
Vertical level
A material used between the face of a search unit and the test surface to permit or improve the transmission of ultrasonic vibrations from the search unit to the material being tested is called:
A couplant
When an ultrasonic beam passes through the interface between two dissimilar
materials at an angle, a new angle of sound travel is formed in the second material due to:
Refraction
The velocity of sound waves is primarily dependent on:
The material in which the sound is being transmitted and the mode of vibration
Piezoelectric ability is the property of a material to:
Produce an electric current when deformed and vice versa
The boundary between two different materials which are in contact with each other is called:
An interface
An ultrasonic insrument control which is used to adjust the sharpness of the CRT
screen display is called:
Astigmatism or focus
A disadvantage of using a low frequency ultrasonic transducer is:
It provides a larger beam angle and poorer resolving power
As transducer crystal thickness decreases:
Frequency increases
On the area-amplitude ultrasonic standard test blocks, the flat-bottomed holes in the
blocks are:
Different in diameter, increasing by 1/64 inch increments from the No. 1 block
to the No. 8 block
An ultrasonic instrument control which is used to expand or contract the horizontal
base line of an A scan display is called:
The sweep length or range control
Greater depth of penetration in coarse grained material may be achieved using:
Lower frequencies
A disadvantage of using a low frequency ultrasonic transducer is:
It provides a smaller beam angle and poorer resolving power
A disadvantage of using a high frequency ultrasonic transducer is:
It is scattered more by coarse grained material
When a longitudinal wave sound beam passes through an acoustic interface at some
angle other than zero degrees:
Reflection, refraction and mode conversion occur
The angle of a refracted shear wave generated as a sound wave passes at an angle through an acoustic interface is depentant on
The acoustic impedances of the materials on each side of the interface
The purpose of the couplant is to:
Match impedances between the transducer and test piece
Which of the following can be a source of spurious ultrasonic signals?
(a) Surface roughness of the test piece
(b) Mode conversion within the test piece
(c) Shape or contour of the test piece
(d) All of the above
When a sound beam is reflected:
The angle of reflection equals the angle of incidence
Sound beam intensity decreases expontentially with distance in the area called:
The far field
The ability to detect echoes from small reflectors is called:
Sensitivity
The ability to separate echoes from reflectors close together in depth is called:
Resolution
Which of the following transducer materials is the most efficient receiver of
ultrasonic energy?
Lithium sulfate
A display which shows the initial pulse and the front surface echo superimposed
would be considered:
An A scan
A display which shows the initial pulse and the front surface echo with a fairly wide
space between the two would be considered:
An immersion test
When conducting an immersion test, the water path distance must be controlled so
that:
The test piece discontinuity indications appear between the first front and first
back surface echos
