MT LEV-III 59 Cards Harold Bennett 2025 Flashcards
MT LEV-III
For which of the following would the wet fluorescent technique be preferred over the dry technique?
When increased speed and sensitivity are desired.
The magnetic domains in a permanent magnet are aligned in:
Fixed positions, predominantly in one direction.
Gas, hot tears, cold shuts, shrinkage cracks and sand inclusions are examples of defects resulting from which of the following processes?
Casting.
Which of the following statements is a valid reason for demagnetizing a part after completing a magnetic particle test?
If the part is to be radiographed after magnetic particle inspection, residual magnetism may interfere with the electromagnetic radiation spectrum.
Subjecting a part to a magnetic field that is constantly reversing in polarity and gradually diminishing in strength accomplishes which of the following?
Demagnetizes the part.
The concentration of the solid content of a suspension of magnetic particles is measured by:
Permitting the solids to settle out of suspension.
An important factor that must be considered when selecting a method of magnetization is the:
Alloy, shape, and condition of the part.
When a magnetic material reaches its Curie temperature, the material becomes:
Paramagnetic.
Magnetic particle inspection methods on ferromagnetic materials are recognized as superior to liquid penetrant techniques when:
The parts are painted.
A paramagnetic material:
Is slightly magnetic.
Which of the following will reduce a magnetic field?
Move the alternating current coil further away from the part.
When an external magnetizing force is removed, some of the magnetic domains remain preferentially oriented. The additional force required to return them to their original random orientation is commonly referred to as:
Coercive force.
When a cylinder is magnetized by a central conductor, the field is most intense:
At the inside surface of the cylinder.
When is the magnetic field strongest in an object being inspected by the magnetic particle method?
While the magnetizing current is applied.
Which of the demagnetization methods listed below is most effective?
Direct current with reversing and step-down control.
When using the longitudinal magnetization method to inspect a bar 152 mm (6 in.) long and 51 mm (2 in.) in diameter with a 5-turn coil, which of the following amperage values should be used?
3000A.
To examine a part 127 mm (5 in.) long and 51 mm (2 in.) in diameter using a 5-turn coil and head stock magnetic particle machine, what amperage should be used for longitudinal magnetization?
3600A.
To examine a bar 381 mm (15 in.) long and 51 mm (2 in.) in diameter using a 7-turn coil and head-stock magnetic particle machine, what amperage should be used for circular magnetization?
1800A.
If the same amperage is passed through a 25 mm and 51 mm (1 in. and a 2 in.) diameter bar of the same length and material, the strength of the magnetic field at the surface:
Of the 25 mm (1 in.) bar will be approximately twice that of the 51 mm (2 in.) bar.
If the same amperage is passed through a 25 mm (1 in.) diameter bar and a 51 mm (2 in.) diameter bar of the same length and material, the strength of the magnetic field at the center of:
Both bars will be 0.
When a magnetic field is induced in a part with prods spaced 152 mm (6 in.) apart, the field is a:
Circular field.
When circular magnetization is used to detect subsurface discontinuities, direct current is used instead of alternating current because:
The skin effect of alternating current reduces the maximum depth at which discontinuities can be found.
An inspection method in which an initial magnetizing force is applied to a part and then reduced to a lower continuous value is called:
The surge method.
When deciding to inspect a part by the residual method of applying the particles, what factor affects the residual magnetic field strength of the part?
The retentivity of the part.
Factors that must be considered when interpreting an indication are:
The orientation and shape of the indication and the direction of the magnetic field.
A 7-turn coil at 1000 A is used to inspect a round solid part 381 mm (15 in.) long and 64 mm (2.5 in.) in diameter. The length-to-diameter ratio is:
6.0.
Which of the following, when used as the last magnetizing method, will best render a part suitable for relatively easy measurement of the external magnetic field using a field indicator?
Longitudinal magnetization.
When using direct current an indication is detected. What is the next logical step to determine if the indication results from a surface or subsurface condition?
Reinspect using alternating current.
Which of the statements below is most appropriate concerning materials I and II represented by the hysteresis curves shown in Figure 1?
Material II could be used for dry powder magnetic particles.
Considering the curves shown in Figure 1, material II in comparison to material I indicates that the material:
Has a high permeability.
Point B on the hysteresis curve for material I shown in Figure 1:
Is the material’s magnetic saturation point.
Which point on the hysteresis curve shown in Figure 1 represents the residual field value?
C.
When withdrawing a part from the field around a coil and without changing the direction of current, which of the following has the least effect on demagnetizing the part?
Direct current.
The least important factor below that should not be considered when selecting a method of magnetization to detect subsurface discontinuities is:
Cost of the equipment.
Which of the following discontinuities occur as a result of the rolling process?
Laminations.
Which of the following discontinuities occur as a result of the forging process?
Laps.
If an indication is formed when using the residual method as well as the continuous method, it is most likely:
A relevant indication.
Plated parts can be reliably tested for fine surface cracks using the magnetic particle method if the plating is less than:
0.127 mm (0.005 in.) thick.
The magnetic lines of flux in a permanent magnet:
Enter the south pole and leave through the north pole.
Which of the following magnetization techniques is not recommended for magnetic particle testing?
Parallel magnetization.
When attempting to demagnetize a part containing a circular residual field:
Establish a longitudinal field and then proceed with demagnetization.
Small parts requiring demagnetization should be:
Processed through a demagnetization cycle one at a time.
The best shape for magnetic particles used in the dry powder method is:
A mixture of elongated and globular.
The best method for testing ball bearings is:
Induced current shots along X, Y, and Z axis, rotating 360 degrees during each shot.
When a magnetized ferromagnetic object is exposed to a subsequent heating operation above the Curie point:
The magnetic domains become random.
A discontinuity caused by a welding operation is:
Lamellar tearing.
The most effective current to be used with dry magnetic particle is:
Half-wave rectified alternating current.
The following properties should be considered in choosing a vehicle for the wet method, except:
Capillarity.
The amount of light reflected by one surface compared to that reflected by another adjacent surface is:
Brightness contrast.
Given a certain continuous magnetization current in a material, which type of current would give the deepest penetration?
Half-wave direct current.
Given a certain continuous magnetization current in a material, which type of current would give the shallowest penetration?
Alternating current.
Which type of radiation can most damage human tissue?
UV-B.
Compared with magnetic particle testing, liquid penetrant testing is not reliable after paint removal from weld because:
Partial smearing of weld surface metal across the discontinuity opening can occur.
Prod spacing less than 76.2 mm (3 in.) is usually not practical because:
Particles tend to bend around the prod making interpretation difficult.
One of the most important facts that must be remembered while establishing magnetic particle procedure:
In most cases the continuous method is more sensitive than is the residual method.
Which one of the following magnetic particle testing techniques is logically acceptable for testing a large flat area?
Prod.
Permeability of a material can be numerically written as:
BM.
One disadvantage for using undyed wet magnetic particles is:
The lack of contrasting color makes them difficult to see.
One of the most desirable characteristics of the media for magnetic particle testing is:
The highest possible permeability and lowest retentivity.
