Term
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Definition
| at the interface of two media with different velocities: V1 ,V2 |
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Term
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Definition
| Refracted angle determined by it |
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Term
| Mode conversion, occurs when |
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Definition
| a wave encounters an interface between materials of different acoustic impedance and the incident angle is not normal to the interface. |
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Term
| how/ when can one form of wave energy be transformed into an other form? |
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Definition
| When sound travels in a solid material, one form of wave energy can be transformed into another form. For example, when a longitudinal wave hits an interface at an angle, some of the energy can cause particle movement in the transverse direction to start a shear (transverse) wave. |
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Definition
| Refracted L-wave angle is 90 degrees |
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Term
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Definition
| refracted S-wave angle is 90 degrees |
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Term
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Definition
| inhomogeneous compression wave |
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Term
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Definition
| At the critical angle of incidence, much of the acoustic energy is in the form of an inhomogeneous compression wave, which travels along the interface and decays exponentially with depth from the interface. |
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Term
| what creep waves are used for |
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Definition
| Because of the inhomogeneous nature and the fact that they decay rapidly, creep waves are not used as extensively as Rayleigh surface waves in NDT. However, creep waves are sometimes useful because, due to their longer wavelengths, they suffer less from surface irregularities and coarse material microstructure than Rayleigh waves. |
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Term
| The combined effect of scattering and absorption is called |
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Definition
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Term
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Definition
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Term
| two basic causes of sound weakening in natural materials |
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Definition
| scattering and absorption |
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Term
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Definition
| When sound travels through a medium, its intensity diminishes with distance. In idealized materials, sound pressure (signal amplitude) is only reduced by the spreading of the wave. Natural materials, however, all produce an effect which further weakens the sound. This further weakening results from two basic causes, which are scattering and absorption. The combined effect of scattering and absorption is called attenuation |
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Term
| In idealized materials, sound pressure (signal amplitude) is only reduced by |
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Definition
| the spreading of the wave |
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Term
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Definition
Reduction in sound intensity with distance
- OR -
Reduction in signal amplitude with distance
Limits the maximum thickness that
can be inspected. |
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Term
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Definition
Scattering of Sound – Main Reason
Grains
Impurities
Impedance mismatch at grain boundaries
Surface roughness
Absorption of Sound
Direct conversion to heat e.g. plastics |
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Term
| attenuation increases with what? |
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Definition
grain size/ waveleangth
or / aka
d/ (lambda symbol)
and
Increases with frequency. So in order to have more penetration the frequency is decreased thereby decreasing the sensitivity and resolution
and
Cast structures produce strong attenuation |
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Term
relationship between attenuation and frequency
and penetration and sensitivity |
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Definition
attenuation increases with frequency
in order to have more penetration the frequency is decreased
when freqeuency is decreased so is the sensitivity and resolution |
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Term
| Materials with low Attenuation |
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Definition
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Term
| Materials with medium Attenuation |
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Definition
| Cast Al, Steel, Copper, Plastics |
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Term
| Materials with high Attenuation |
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Definition
| Plastics with rubber, cast iron |
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Term
| Attenuation and Frequency |
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Definition
Attenuation can be reduced by using lower frequencies but this will also
Reduce sensitivity for detection of
small flaws, For flaw detection λ/D <10
Reduce resolution by increasing the time
period or pulse width
Attenuation caused by surface roughness
can be reduced by selecting a lower
frequency probe and a viscous couplant |
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Term
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Definition
Defined as the region where
d < λ,
grain size smaller than wavelength
Attenuation α d^3f4
For 5 MHz S waves in steel λ = 0.6 mm |
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Term
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Definition
Caused by preferential grain direction EG. Cast stainless, SS welds, inc 625 welds
Velocity can vary and will depend on the crystal direction/elastic Modulus |
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Term
| Anisotropy And Velocity for L and S waves |
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Definition
L-wave velocity is less affected
S-wave velocity is more affected |
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Term
| Velocity Variations 304 SS Crystal |
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Definition
Extreme shear wave velocities SS crystal:
Vsmax = 4.04 x 106 mm/sec
Vsmin = 2.12 x 106 mm/sec
Longitudinal velocity extremes are
Vℓmax = 6.57 x 106 mm/sec
Vℓmin = 5.23 x 106 mm/sec
The polycrystalline velocities of 304 SS are
Vℓ poly = 5.7 x 106 mm/sec
Vℓ poly = 3.14 x 106 mm/sec |
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Term
| why use shear waves at all |
|
Definition
L-wave output is 40 to 45 % of S-waves
S-waves are always produced with L-waves and this makes it confusing
Note: Wherever possible avoid using refracted L-waves |
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Term
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Definition
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Term
| The relationship between time and frequency in mathematical terms is given by the equation |
|
Definition
f = 1/T
where T is the period of the oscillation and f is the frequency |
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Term
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Definition
| the highest points of the wavelength |
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Term
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Definition
| distance between center of wave and both peaks and troughs |
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Term
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Definition
| the lowest points of the wavelength |
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Term
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Definition
| from the middle of one side of the wave the wave to the middle of the other side containing one peak and one trough |
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Term
| amplitude of the wave is measured from |
|
Definition
| the peak (or trough) to the mid-point |
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Term
| Amplitude can be defined as |
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Definition
| "the maximum displacement from the average position." |
|
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Term
| "the maximum displacement from the average position." |
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Definition
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Term
λ (Greek lambda) is the symbol for
|
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Definition
|
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Term
| Wavelength is given the symbol |
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Definition
|
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Term
|
Definition
| Frequency= Velocity/ wavelength |
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Term
|
Definition
| wavelength = velocity/ Frequency |
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Term
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Definition
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Term
| Ultrasonics is the study of |
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Definition
| very high frequency sound waves which cannot be heard by human ear and have a frequency above 20,000 Hz. |
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Term
| The audible range for human beings is |
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Definition
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Term
| propagation of mechanical vibration through a medium |
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Definition
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Term
| can sound travel through a vacuum |
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Definition
|
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Term
|
Definition
| propagation of mechanical vibration through a medium, it can not travel through a vacuum |
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Term
| several types of sound waves that travel through solids |
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Definition
Longitudinal Waves/Compression Waves
Shear Waves/Transverse Waves
Lamb Waves/Plate Waves
Surface Waves/Rayleigh Waves |
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Term
| how many kinds of waves travel through solids |
|
Definition
|
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Term
| what are the 4 kinds of waves that travel through solids |
|
Definition
Longitudinal Waves/ Compression Waves
Shear Waves/ Transverse Waves
Lamb Waves /Plate Waves
Surface Waves /Rayleigh Waves |
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Term
| Properties of Longitudinal Waves |
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Definition
Travels in all medium
Maximum velocity
Particles vibrate parallel to wave direction
Has maximum penetration power
Least attenuation
Used in immersion testing
Used mainly for straight beam inspection
for detection of lamellar flaws |
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Term
| Properties of Surface Waves |
|
Definition
Particle Vibration: Elliptical Motion
Maximum depth of penetration: 1waveleangth
Cannot negotiate a sharp edge If the surface has substances like grease, oil etc. surface wave gets easily dampened.
Is generated by angulating the incident angle at the second critical angle.
Very sensitive to surface flaws
Velocity of surface wave is approximately 0.9 times of that of shear wave. |
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Term
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Definition
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Term
| Factors Affecting Velocity |
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Definition
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Term
|
Definition
|
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Term
| Acoustic Impedance formula |
|
Definition
The acoustic impedance (Z) of a material is defined as
the product of density (p)
and acoustic velocity (V) of that material
acustic impedance= density X Velocity
Z = ρ x v |
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Term
|
Definition
| The reflected energy is the square of the difference divided by the sum of the acoustic impedances of the two materials. |
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Term
|
Definition
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Term
|
Definition
|
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Term
|
Definition
To Measure thickness, depth, metal path, etc.
Multiple Gates can be used
Gate reference can be initial pulse or Interface echo (IF)
IF gate is used in immersion testing
Alarm gates used in automated testing |
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Term
|
Definition
| Start can be reference to Initial Pulse or Interface echo |
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Term
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Definition
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Term
|
Definition
|
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Term
|
Definition
|
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Term
|
Definition
Used for Corrosion Mapping
Used for Immersion Testing |
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Term
|
Definition
Source of short highenergy bursts of electrical energy
triggerd by timer |
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Term
|
Definition
|
|
Term
| The primary purpose of reference block is |
|
Definition
| to provide a means for adjusting the instrument in order to evaluate discontinuities which could be harmful to the proper function of the work piece |
|
|
Term
| this provides a means for adjusting the instrument in order to evaluate discontinuities which could be harmful to the proper function of the work piece |
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Definition
|
|
Term
| The block is much smaller and lighter than the IIW block but performs many of the same functions. |
|
Definition
| Miniature Angle-Beam or ROMPAS Calibration Block |
|
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Term
|
Definition
| have a constant taper over the desired thickness range. |
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Term
| Step and Tapered Calibration Wedges |
|
Definition
| Step and tapered calibration wedges come in a large variety of sizes and configurations. Step wedges are typically manufactured with four or five steps but custom wedges can be obtained with any number of steps. Tapered wedges have a constant taper over the desired thickness range. |
|
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Term
| how many Distance/area amplitude correction blocks typically in a set |
|
Definition
10
they typically come as a ten-block set |
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Term
| Aluminum sets of Distance/Area-Amplitude Blocks manufactured per the requirements of |
|
Definition
|
|
Term
| steel sets of Distance/Area-Amplitude Blocks manufactured per the requirements of |
|
Definition
|
|
Term
| Distance/Area-Amplitude Blocks come in these materials |
|
Definition
|
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Term
|
Definition
|
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Term
|
Definition
|
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Term
| what view does c-scan have? |
|
Definition
|
|
Term
| What view does B-scan show? |
|
Definition
|
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Term
|
Definition
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Term
| the difrence between sheer and longatudinal waves (pic) |
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Definition
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Term
| what view does A-Scan show |
|
Definition
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Term
| Step and taperd cal wedges |
|
Definition
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Term
| 1st critical angle pic graph |
|
Definition
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Term
| 2nd critical angle pic graph |
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Definition
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Term
|
Definition
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Term
| echo transmittance water steel interface pic |
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Definition
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Term
|
Definition
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Term
|
Definition
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Term
|
Definition
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Term
| echo transmittance water steel interface pic biger |
|
Definition
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