Level 2 Flashcards
Mechanical wave motion requires
a) high pressure
b) low pressure
c) particle motion
d) ionic bonding and disbonding
C
In an homogenous and isotropic elastic medium such as low carbon steel, sound velocity a) decreases with distance from source b) varies with direction c) is constant in all directions d) depends on frequency
C
The amount of time between two compressions, or two rarefactions of an elastic wave is called a) wavelength b) period c) frequency d) velocity
B
The velocity of sound is
a) constant for all materials
b) varies with frequency
c) varies inversely with wavelength
d) is characteristic of a material
D
Compared to the atomic or molecular spacing of a material, ultrasonic wavelengths are
a) much greater
b) smaller
c) about the same distance 2
d) are multiples of the atomic spacing
A
The elastic wave that has particle motion parallel to the direction of wave propagation is called
a) longitudinal wave
b) compression wave
c) density wave
d) all of the above
D
In Rayleigh waves, particle motion is
a) parallel to the direction of wave propagation
b) right angles to the direction of wave propagation
c) retrograde
d) in counter clockwise ellipses
D
Rayleigh waves can be used in steel to penetrate up to
a) 10mm
b) 10cm
c) 1m
d) 1 wavelength
D
In bending waves (plate wave mode) particles in the middle zone of the plate vibrate
a) in longitudinal mode
b) in shear mode
c) in Rayeigh mode
d) not at all
B
In the Lamb wave called a dilational wave, particles in the middle zone of the plate vibrate
a) in longitudinal mode
b) in shear mode 3
c) in Rayleigh mode
d) not at all
A
If one sound beam passes through another moving in the opposite direction, the result will be,
a) a change in amplitude
b) a change in direction
c) a change in frequency
d) no change
A
In a standing wave, nodes and antinodes are separated by
a) 1/4 wavelength
b) 1/2 wavelength
c) 1 wavelength
d) 2 wavelengths
A
Standing waves are generated in ultrasonic testing for
a) through testing (pitch-catch)
b) resonance thickness testing
c) flaw detection
d) B-scans
B
Specific acoustic impedance is the product of
a) density and permittivity
b) hardness and velocity
c) velocity and density
d) specific activity and amplitude
C
Poisson’s ratio is expressed in units of
a) m/s
b) Pa
c) N/m24
d) no units, it is dimensionless
D
Frequency can be expressed in terms of
a) 1/s (s=seconds)
b) cps
c) Mhz
d) all of the above
D
The ratio of sound velocity in water to the longitudinal velocity of sound in steel is very nearly
a) 1:1
b) 1:2
c) 1:4
d) 1:5
C
Rayleigh wave velocities for a given material are always
a) greater than longitudinal wave velocities
b) greater than transverse wave velocities
c) less than transverse wave velocities
d) about the same as shear wave velocities
C
The ratio of the incident sound pressure to the reflected sound pressure is called the
a) acoustic impedance
b) acoustic intensity
c) coefficient of reflection
d) coefficient of transmission
C
The ratio of the incident sound pressure to the transmitted sound pressure is called the a) acoustic impedance b) acoustic intensity 5 c) coefficient of reflection d) coefficient of transmission
D
When is the coefficient of transmission a negative value?
a) if Z incident is less than Z transmitted
b) If Z incident is greater than Z transmitted
c) if Z incident equals Z transmitted
d) never
D
Incident sound pressure plus reflected sound pressure equals
a) 0
b) 1
c) transmitted sound pressure
d) none of the above
C
Total incident sound intensity can be calculated from
a) the sum of the reflected and transmitted intensities
b) the difference between reflected and transmitted intensities
c) R plus D (reflection and transmission coefficients)
d) R plus D (reflection and transmission coefficients)
A
(Sin a1) (C2) = (Sin a2) C1) is a form of
a) Krautkramer’s law
b) Snell’s law
c) Boyle’s law
d) Hooke’s law
B
If the Sine of a refracted angle is calculated to be 0.707, the refracted angle will be
a) 36 degrees
b) 45 degrees
c) 60 degrees
d) undetermined from the given information
B
For a shear wave travelling from steel to water incident on the boundary at 10 degrees will give a refracted shear wave in water with an angle of
a) 0 degrees
b) 5 degrees
c) 20 degrees
d) none of the above
D
The critical angle refers to the
a) longitudinal waves’ angle
b) incident angle
c) refracted angle
d) reflected shear wave
B
The critical angle occurs when the sine of the refracted angle equals
a) 0.707
b) 0.846
c) 1.000
d) 1.414
C
At a solid to free boundary, an obliquely incident longitudinal wave from the solid can result in, at most,
a) a reflected longitudinal wave only
b) a reflected longitudinal and reflected shear wave
c) a refracted longitudinal long wave
d) a reflected longitudinal and reflected shear and refracted longitudinal wave
B
At a liquid/solid boundary with an obliquely incident
longitudinal wave from the liquid the result could be at most be 7
a) a reflected longitudinal wave only
b) a refracted longitudinal wave only
c) a reflected longitudinal, and a refracted long wave
d) a reflected long and refracted long and shear wave
D
Given V (water) = 1.5 mm/us and V (steel) longitudinal velocity = 5.0 mm/us and shear velocity mm/us, what is the second critical angle of an incident longitudinal wave from steel.
a) 19 degrees
b) 27 degrees
c) 36 degrees
d) none of the above
D
A shear wave polarized in the plane of incidence impinging on a free boundary at right angles to the boundary will result in
a) a reflected shear wave only
b) a reflected shear wave and reflected longitudinal wave
c) reflected longitudinal wave only
d) a surface wave
A
Maximum surface wave energy is obtained when the angle of incidence is
a) 0 degrees
b) 60 degrees
c) 90 degrees
d) just over the critical angle
D
Geometric-optic treatment of ultrasonic waves fails to account for
a) reflection
b) refraction
c) diffraction
d) normal incidence
C
The relationship for acoustic pressure of spherical waves P=Pe/d, implies
a) an inverse proportionality to distance
b) infinite sound pressure at the source
c) both a and b
d) none of the above
C
Spherical and cylindrical waves reflecting off a plane surface preserve shape but not
a) velocity
b) wavelength
c) frequency
d) acoustic pressure distribution
D
The advantage of inspecting a thick solid cylinder with a waterpath two times the cylinder radius instead of just the cylinder radius is
a) increased sensitivity
b) reduced entry noise
c) smaller near zone
d) more uniform pressure through the cylinder
D
The ratio of the diameter of an oscillator to the wavelength it generates gives the
a) acoustic velocity
b) near zone length
c) acoustic impedance of the oscillator
d) number of interference maxima and minima
D
For practical purposes, the equation for the near zone distance can be approximated by (where l = wavelength and D = probe diameter)
a) D / l
b) D squared / 4 l 9
c) D squared minus l squared/4 l
d) (D-4l)/l squared
B
Given an "X-cut" normal beam contact probe on steel, the probe is 12 mm diameter and has a frequency of 2 MHz. The approximate near zone length is (V steel = 6.0mm/us) a) 4mm b) 12mm c) 24mm d) 48mm
B
A transducer has a near field in water of 35 mm. When used in contact on steel the near zone will be about
a) 47 mm
b) 35 mm
c) 18 mm
d) 9 mm
D
The so called angle of divergence applies to the
a) dead zone
b) near field
c) Fresnel zone
d) far field
D
Sin(gamma) = 1.2 lambda / D (where lambda is wavelength and D is the crystal diameter) is the equation for
a) the first critical angle
b) interference minima in the near zone
c) half angle of divergence in the Fraunhoffer zone
d) optimum energy angle for shear waves
C
The angle of divergence is a function of 10
a) crystal thickness of the probe
b) crystal dimension eg. diameter
c) crystal shape
d) all of the above
D
A rectangular probe, 4mm X 8mm, will have its maximum half angle of divergence
a) in the 4mm direction
b) in the 8mm direction
c) in no particular orientation
d) constant in all directions
A
Given a 10 X 10mm square probe of 5 MHz fundamental frequency, compared to a 10mm diameter 5 Mhz probe, the near zone of the square probe would be a) longer b) shorter c) the same d) independent of wavelength
A
In ultrasonic testing, actual point focusing of sound is not possible due to
a) damping effects
b) divergence in the far zone
c) asymetric vibrations
d) diffraction effects
D
Huygen’s wavelet theory and Fresnel zones can be used to predict
a) focal length
b) maxima and minima points in a sound beam
c) radius of curvature in a focused probe
d) fundamental frequency
B
AVG (or DGS in English) diagrams compare flaw signal amplitudes to
a) side drilled holes
b) flat bottomed holes
c) a theoretical maximum
d) DAC’s
C
Flaws oriented obliquely to the incident sound beam may be better detected using
a) high gain
b) higher frequency
c) focused probes
d) separate transmit and receive probes
D
Echo amplitudes of reference reflectors are dependant on
a) size
b) shape
c) wave mode
d) all of the above
D
A surface can be considered smooth if its irregularities are not more than ________ wavelength.
a) 1
b) 1/3
c) 1/10
d) 1/100
B
The problem of scatter of a rough surface can be reduced by
a) immersion testing
b) a smaller diameter probe
c) a lower frequency probe
d) longer pulse length
C
The effect of oxides or other non metallic inclusions within a defect is to
a) amplify the signal
b) split the signal by mode conversion
c) reduce the signal amplitude
d) none of the above
C
As the pulse length of the excitation voltage is shortened the transmitted pulse
a) frequency spectrum broadens
b) frequency spectrum shortens
c) increases energy output
d) increases penetration ability
A
In general, the frequency content of an ultrasound beam has a larger proportion of high frequencies in its spectrum
a) on axis
b) off axis
c) in the far zone
d) in the free zone
A
The most significant result of scatter and absorption is
a) frequency content changes
b) directivity
c) attenuation
d) beam spreading
C
The effect of attenuation by absorption is most pronounced
a) in steel
b) on the beam axis
c) on higher frequencies
d) on lower frequencies
C
A neper (Np) is a unit of
a) attenuation
b) acoustic impedance
c) pulse rate
d) wavelength
A
If 3 dB gain was removed from a 100% FSH signal the resulting signal would be \_\_\_\_\_\_\_\_\_\_ FSH. a) 97 b) 94 c) 85 d) 71
D
If a signal is dropped from 100% FSH to 32% FSH, the number of dB gain removed from the receiver is
a) 14
b) 10
c) 6
d) 4
B
Attenuation in plastics and rubber is predominantly attributable to
a) absorption
b) scatter
c) beam spread
d) none of the above
A
The attenuation coefficient has the units
a) dB/m
b) Np/cm
c) Np/mm
d) all of the above
D
Non-crystallized materials such as glass are most likely to be
a) isotropic
b) anisotropic
c) piezoelectric
d) not inspectable
A
Attenuation in cast metals is usually reduced by
a) forging
b) rolling
c) extruding
d) all of the above
D
For a given metal of a given grain size, attenuation in the cast form of the metal relative to the worked form is usually
a) greater
b) less
c) identical
d) unpredictable
A
The effect utilized by ultrasonic transducer crystals is the _________ effect.
a) piezoelectric
b) pyroelectric
c) ferroelectric
d) hall
A
Piezoelectric crystals’ structure will always contain
a) face-centered cubic form
b) hexagonal form
c) symmetry about polar axes
d) asymmetry about polar axes
D
An X-cut quartz crystal is primarily used to generate the ________ wave mode.
a) longitudinal
b) transverse
c) Rayleigh
d) Lamb
A
A typical voltage range for driving (exciting) piezoelectric crystals would be
a) 50 to 100 mV
b) 50 to 100 V
c) 50 to 100 kV
d) 500 to 1000 V
D
Y-cut crystals generate shear waves into a solid material by
a) refraction
b) direct coupling
c) reflection
d) no means known
B
The efficiency of the piezoelectric effect is rated by K33 which is the
a) piezoelectric modulus
b) electromechanical coupling factor
c) deformation constant
d) Young’s modulus
B
After a voltage excitation of the piezoelectric crystal, the amplitude of its oscillations decrease by the quantity determined by the
a) Q factor
b) damping coefficient 16
c) characteristic frequency
d) resonance frequency
B
The characteristic or fundamental frequency of a piezoelectric material is not dependant on
a) damping material on either face
b) thickness of crystal
c) velocity of sound in the crystal
d) all of the above
A
To determine the damping coefficient you must know
a) the acoustic impedance of the backing material
b) the acoustic impedance of the loading (front) material
c) both a and b
d) none of the above
C
Harmonic resonances of piezoelectrically excited crystals occur at
a) twice the characteristic frequency
b) all even multiples of the first resonant frequency
c) all odd multiples of the first resonant frequency
d) none of the above
C
Although rarely used in modern day NDT transducers, quartz has the advantage of
a) chemical inertness
b) high coupling coefficient
c) high dielectric constant
d) all of the above
A
For high temperature measurements the preferred piezoelectric material is 17
a) lithium niobate
b) lithium sulphate hydrate
c) quartz
d) PZT
A
Polarization of PZT crystals is accomplished using
a) strong permanent magnets
b) strong alternating voltage
c) strong direct voltage
d) none of the above
C
A significant disadvantage of PZT as a transducer material is its
a) low density
b) high curie point
c) high acoustic impedance preventing good matching
d) exceptionally high electromechanical coupling coefficient
C
Electrodynamic methods of generating and receiving ultrasound rely on
a) magnetrostriction
b) eddy currents
c) laser heating
d) none of the above
B
Magnetostricitive probes consist of
a) copper windings through thin laminated plates
b) copper windings around a ceramic core
c) solid steel wrapped with copper wire
d) none of the above
A
Optical methods used in ultrasonic testing such as Schlieren diffraction and interferometer methods are used in 18
a) transmission techniques only
b) reception techniques only
c) both transmission and reception
d) optical methods are not used in ultrasonics
B
To make useful ultrasonic holograms requires
a) penetrating acoustic waves
b) a source of reference waves
c) conversion means to optical holograms
d) all of the above
D
Pulse-echo ultrasonic testing
a) uses a single probe
b) uses separate transmitter and reciever probes
c) both a and b
d) none of the above
C
Using the pulse echo method with a 0 degree probe having separate transmit and receive crystals, the pattern on a CRT of a flat steel plate would appear as a) evenly spaced multiples b) randomly spaced multiples c) a single spike from the opposite wall d) an uninterrupted base line
A
Phantom echoes of multiples when testing thick specimens are a result of
a) insufficient suppression
b) modulation from the power supply
c) PRF set too high
d) too much gain
C
The main bang signal is formed as a result of the
a) dead zone
b) couplant/specimen interface
c) transmitter pulse
d) all of the above
C
When an ultrasonic machine is equipped with this option, the pulse energy and pulse length can be adjusted
a) receiver fine grain control
b) swept gain
c) time corrected gain
d) damping
D
The voltage of a received ultrasonic signal at the machine’s receiver is typically
a) 1/1000 to 1 volt
b) 10 to 100 volts
c) 100 to 1000 volts
d) not measurable
A
In order to adequately amplify received signals an ultrasonic machine’s receiver amplifier must have a gain of about
a) 6 to 12 dB
b) 20 to 40 dB
c) 80 to 100 dB
d) 100 to 200 dB
C
The main disavantage of a broadband receiver in a ultrasonic machine is
a) non-linear response to amplification
b) amplifier noise limits possible amplification
c) RF display cannot be used
d) rectified display cannot be used
B
The zero time on a contact normal beam probe
a) corresponds to the rising edge of the main bang
b) corresponds to the falling edge of the main bang
c) is determined indirectly by calibration blocks
d) none of the above
C
The acoustic impedance of backing material is often increased by
a) adding a tuning transformer to the probe
b) increasing test pressures
c) adding metal powder to the material
d) increasing suppression
C
A great disadvantage of the old quartz crystal transducers that used the work piece as one of the electrodes was
a) a fluctuating dead zone
b) insufficient damping
c) decreasing sensitivity with use
d) an increase in frequency with use
D
A contact angle beam probe used in fixed housings occasionally requires
a) transformer tuning
b) machining or replacing of the wear face
c) new couplant between crystal and plastic wedge
d) all of the above
B
Wedges used to introduce refracted waves into a test specimen are made of
a) copper
b) brass
c) plastics
d) all of the above can be used
D
In order that one can operate above the critical angle of reflection of longitudinal waves, wedge material for angle beams are
a) grooved on the front face
b) always made of polystyrene
c) chosen with a longitudinal velocity greater than the shear velocity of the test piece
d) chosen with a longitudinal velocity less than the shear velocity of the test piece
D
The layer of highly absorbing material sometimes bonded to the top and front of an angle probe’s wedge is called a (an)
a) cap
b) backing
c) anechoic trap
d) none of the above
C
A calibration for horizontal linearity would check properties of the
a) receiver amplifier
b) image unit (oscilloscope)
c) calibration block
d) probe
B
