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MEC302 > Lecture 5-6 > Flashcards

Lecture 5-6 Flashcards

1
Q

Which examination tests are used for surface cracks? (5)

A
  1. Visual and optical
  2. Liquid penetrant
  3. Magnetic particle
  4. Leak
  5. Hydro Proof
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2
Q

Which examination test can be used on subsurface cracks?

A

Electromagnetic

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3
Q

Which examination methods fall under ‘volumetric methods’?

A
  1. Radiography
  2. Ultrasonic testing
  3. Acoustic emission testing
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4
Q

What is the aim of non-destructive examination?

A

To use non-invasive techniques to determine the integrity of materials, components or structures, or to quantitively measure some characteristics of an object

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5
Q

What are the uses of non-destructive examination techniques?

A
  • Flaw detection/evaluation
  • Location determination
  • Leak determination
  • Dimensional measurements
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6
Q

What is the general process of visual/optical testing?

A

Visual examiners follow procedures.

Some procedures compare workmanship samples with production parts.

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7
Q

What are the disadvantages to visual and optical testing?

A
  • Not good for large areas with small cracks/defects

- Can become expensive when using lighting, microscopes, mirrors, boroscopes

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8
Q

How can visual and optical testing be improved?

A
  • Take videos/photos for comparison

- Use image recognition

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9
Q

What is the general process of liquid penetrant testing?

A

Object is coated with dye
Excess dye is removed from the surface
Dry developer is applied, drawing penetrant out of imperfections

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10
Q

Why would visible dyes be used in liquid penetrant testing?

A

The vivid colour contrasts with the developer, so ‘bleedout’ is easy to see

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11
Q

Why would fluorescent dyes be used?

A

Ultraviolet light makes them fluoresce, so imperfections can be seen easily

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12
Q

What is liquid penetrant testing used on?

A

Microscopic cracks - dye gets into cracks by capillary action

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13
Q

What is an extra advantage of liquid penetrant testing?

A

It gives an indication of how deep the crack is - more dye will get into a deeper crack

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14
Q

What is the general process of magnetic particle testing?

A

Magnetic field is induced in a ferromagnetic material
Surface is dusted with iron particles
Surface imperfections distort the field and concentrate iron particles near imperfections

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15
Q

What must be taken into account with the magnetic field in magnetic particle testing?

A

It won’t pick up flaws parallel to the field. Therefore, use fields in at least 2 directions

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16
Q

What detecting methods are used in leak testing?

A
  • Electronic listening devices
  • Pressure gauge measurements
  • Liquid and gas penetrant techniques
  • Soap bubble test
17
Q

What is leak testing in simple terms?

A

Listening or looking for escaping fluid

18
Q

What is the general process of electromagnetic testing?

A

Electrical currents are generated in a conductive material by an induced alternating magnetic field
Eddy currents caused by imperfections/changes in conductive properties will cause changes in induced field

19
Q

Why is electromagnetic testing more versatile than magnetic particle testing?

A

It works with any material that is electrically conductive, not just ferromagnetic

20
Q

What is the general process of radiography?

A

Uses penetrating x-rays or gamma rays, directed through a part onto a film or other media
Imperfections are indicated as density changes in the film

21
Q

What are the disadvantages of radiography?

A
  • Expensive
  • Requires skilled personnel
  • Only sees flaws perpendicular to x-ray
  • Dense targets need higher energy x-rays
22
Q

What is the general process of ultrasonic testing?

A

Uses transmission of high-frequency sound waves to detect imperfections

23
Q

What is the most common form of ultrasonic testing?

A

Pulse echo

24
Q

How does pulse echo work?

A

Sound is introduced into an object and reflections are returned to a receiver from internal imperfections or geometrical surfaces

25
Q

What is the general process of acoustic emission testing?

A

When a solid material is stressed, imperfections emit emissions
They can be detected by special receivers

26
Q

What are emissions?

A

Short bursts of acoustic energy

27
Q

How can emissions be evaluated?

A

Through the study of their

  • Intensity
  • Rate
  • Location
28
Q

What should the primary evaluation method be for any quality control program and why?

A

Visual inspection

It is inexpensive and doesn’t normally require special equipment

29
Q

Why are visual aids and gauges sometimes used in VT?

A

To make discontinuity detection easier and to measure the size of discontinuities

30
Q

What can be used if the area to be inspected is not readily visible?

A
  • Boroscopes
  • Torches
  • Mirrors
31
Q

What qualitative measurements can be made of the weld joint?

A
  • Fit-up
  • Weld size
  • Weld reinforcement height
  • Misalignment
  • Depth of undercut
32
Q

What defects on the base metal prior to welding can cause weld defects? (And can be detected with VT)

A
  • Scabs
  • Scales
  • Seams
33
Q

What should be checked after parts have been assembled for welding?

A
  • Weld joint root opening

- Edge preparation

34
Q

What is the normal sequence for a typical liquid penetrant test?

A
  1. Clean test surface
  2. Apply penetrant
  3. Wait for dwell time
  4. Remove excess
  5. Apply developer
  6. Examine surface
  7. Clean to remove residue
35
Q

What are the essential elements of radiographic testing?

A
  1. Source of penetrating radiation
  2. Record or viewing device
  3. Qualified radiographer
  4. Means to process exposed film or operate other recoding means
  5. A person skilled in interpretation of radiographs
36
Q

What does the measurement system for ultrasonic testing include?

A
  1. Pulser circuit (produces impulses to excite transducer)
  2. Receiver
  3. Gates (monitor size of received signal)
  4. Scanning systems (move transducer over fixed path)
  5. Ultrasonic transducer (produces electrical-mechanical conversion to create wave)

MEC302 (13 decks)

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