5: Techniques & Processes Flashcards
Name 3 reasons to use Straight-Beam Testing:
- Measure thickness
- Detect corrosion
- Find disbanding/other discontinuities mostly parallel to surface
Name 2 reasons for Angle-Beam testing:
- Find discontinuities at an angle to front surface
2. Common for weld inspection
What is the reason for using Surface-Wave testing:
Surface breaking discontinuities with restricted access (must be a smooth surface)
What is Plate Wave testing used for?
Very thin sheets.
What is the most commonly used testing technique?
Pulse-Echo
What is the main component of Pulse-Echo testing?
A piezoelectricity charged crystal
What is the difference between Through-Transmission and Pitch & Catch? **
Through-Transmission is 2 transducer used in OPPOSITE sides of each other, but Pitch & Catch transducer can be opposite, adjacent, etc.
Through-Transmission is best for testing what type of material?
Very thick specimens
What are the 6 parts of an immersion tank?
Tank, transducer, manipulator, scan tube, carriage and bridge.
What type of water is used for immersion testing?
Room temperature and de-aerated.
What 3 agents are commonly added to the water?
Wetting agent, anti-bio agent and corrosion inhibitors.
How do you calculate the minimum water distance?
1/4 part thickness plus 6 mm
How do you set the water delay in immersion?
By calculating the minimum correct water distance
DACs don’t generally work on what type of lens’?
Spherically ground lens’
Resonance testing is used for….. (main purpose)
THICKNESS MEASUREMENT
What is resonance testing mainly used on?
Thin material.
When standing waves are formed, the points where the two waves constantly cancel each other out are called what?
Nodes
The points of maximum amplitude between nodes are called what?
Antinodes
The fundamental resonant frequency is what? And what is the formula?
The lowest frequency at which a specimen will resonate.
F = V/2T
The frequencies that are exact multiples of the fundamental frequency are called what?
Harmonics
When using the formula to find the fundamental frequency, as the harmonics increase by 1, what does the formula increase by?
1/2
Ex. FF:
T = 1/2 LAMBDA
2nd Harmonic:
T = 1 LAMBDA
3rd Harmonic:
T = 1 1/2 LAMBDA
The thickness of a material is determined with what formula?
T = V/2f
What are harmonics used for?
Sensitivity
When you use harmonics, you can see a change in what?
Amplitude
Describe B-Scan.
The method of locating probe position from the edge of part required.
What part of the B-Scan is able to locate probe position from edge of part?
An encoder
What is the most common type of B-Scan?
Wheel transducer
Besides A-Scan, what is the other most common type?
C-Scan.
What is a disadvantage about using a C-Scan?
Limited, IF ANY, info about the depth of defects.
Computers can now override this problem by converting to a different scan to determine
Resonance is important for 2 key roles:
- Determines crystal thickness to produce probe of given frequency
- A form of thickness measurement (Resonance Testing)
How are standing waves created?
2 similar plane waves of identical frequency, amplitude and direction of oscillation… BUT DIFFERENT direction of propagation
Resonance causes a drastic increase in what?
Vibration of amplitude
What type of wave does resonance testing use?
Continuous longitudinal wave (not pulsed)
What type of waves have to meet to create standing waves?
Transmitted AND reflected
Resonance does not employ what type of waves?
Lamb waves
Rectification on an A-Scan instrument allows technician to read in…
Radio frequency (RF) or video display
What type of view do you get with a B-Scan instrument?
Cross-Sectional View
What type of view do you get with a C-Scan instrument?
Plan view
Similar to a radiograph display
What are 3 advantages of a Pulse-Echo method?
- Can locate where a defect is in material
- One sided access required
- Can find multiple discontinuities at the same time
What are two disadvantages of the Pulse-Echo method?
- Near field & dead zone effects
2. More attenuation from sound travelling twice through a material
Through-Transmission is advantageous for both thick and thin effects because…
Thin: lack of dead zone effects
Thick: less attenuation (suited for automated tests on large parts)
Two disadvantages of Through-Transmission testing?
- Need access to both sides
2. Needs to be lined up exactly
How is the quality of a material measured with Through-Transmission?
A defective part will result in partial/complete loss of sound transmission.
How is the quality of the material measured with pulse echo?
The pip can be interpreted and evaluated.
What are 4 advantages of immersion testing over contact testing?
- Easier angulation of transducer
- Higher sensitivity possible with higher frequency
- Limited near zone effects
- Better near surface resolution
What are the 3 different immersion testing types?
Bubbler/squirter, conventional and wheel transducer
What are 3 advantages of focused transducer testing over regular immersion testing?
Improves sensitivity & resolution, diminishes effects caused by rough front surface/scattering
What info does a B-Scan give?
Thickness of material, depth of discontinuity from front surface and the size of the discontinuity in one direction.
What info does a C-Scan give?
AREA of discontinuity but not depth/orientation to front surface
When would a C-Scan likely be used?
With an automated system
What are the 3 main areas of resonance testing?
- Thickness measurement (parallel surfaces)
- Bond testing
- Detect large discontinuity oriented parallel to front surface
