MT LEV-II 149 Cards Harold Bennett 2025 Flashcards
Magnetic Particle Testing (MT)
A gear with case-hardened ground teeth and hub ends is MT tested Individual indications are detected on five teeth and one end surface of the hub The indications do not break over the part edges. What is the probable identity of the indication?
Grinding cracks
A prime consideration when selecting a powder to be used as a magnetic particle medium is to select a powder that:
PROVIDES A HIGH CONTRAST TO THE SURFACE BEING TESTED
A rough forging discontinuity has the following characteristics:
1. Can occur on the surface or internally.
2. Is associated with low temperature processing.
3. Is often caused by excessive working.
4. Creates cavities varying in size.
How would it be identified
Burst
Cold working indications will not reappear if the part is:
retested after stress relieving.
External poles which are too strong to permit good inspection of a part are more likely to result when using:
Longitudinal Magnetization.
Half wave rectified AC (HWDC) is used for detection of:
Surface and Subsurface Defects.
If a copper conductor is placed through a ferrous cylinder and a current is passed through the conductor, then the magnetic field (flux density) in the cylinder will be:
greater than in the conductor.
If one-inch and two-inch diameter bars were magnetized by passing the same current through them, the magnetic fields would be:
STRONGER IN THE ONE-INCH DIAMETER BAR.
Of the following discontinuity categories, which one is considered most detrimental to the service life of an item?
Cracks open to the surface
Since the magnetic lines of force within a bar magnet run the length of the bar, it is said to be:
Longitudinally Magnetized
The length of a part being magnetized by passing an electric current from one end to the other:
does not affect the strength of the magnetic field
The most common failure mechanism associated with sharp fillets, notches, undercuts, and seams is:
Fatigue Cracking.
When it is believed that a defect has been removed by chipping, grinding, or flame cutting, the next operation is to
RE-EXAMINE THE AREA BY MAGNETIC PARTICLE TESTING
Which of the following can cause non- relevant magnetic particle indications?
1. JOINTS BETWEEN DISSIMILAR METALS
2. BRAZED JOINTS
3. ROUGHING TOOL CUTS ON SURFACE
Which one of the following is not a discontinuity common to rolled products?
COLD SHUTS
A break in the magnetic uniformity of a part that is called a magnetic discontinuity is related to a sudden change in:
Permeability
A coil around the part produces:
a Longitudinal Field
A coil shot is required to be performed after a head shot using the wet continuous method In order to properly conduct the coil shot it is necessary to:
1. Place the part in the coil and continue the inspection
2. After Evaluating the Head Shot Indications
A curve is sometimes drawn to show graphically the relation of the magnetizing force to the strength of the magnetic field produced in a certain material. This curve is known as the:
HYSTERESIS CURVE
a defect commonly associated with the welding process is
Lack of penetration
A defect open to the surface produces
an indication which is:
SHARP AND DISTINCT
A desirable property of magnetic particles used for the inspection medium for either the dry or wet method is that they:
1. BE NON-TOXIC
2. POSSESS HIGH PERMEABILITY
3. POSSESS LOW RETENTIVITY
A gear with case-hardened ground teeth and hub ends is MT tested Individual indications are detected on five teeth and one end surface of the hub The indications do not break over the part edges. What is the probable identity of the indication?
Grinding cracks
A general rule to use for determining the detectability of surface discontinuities by magnetic particle inspection is that:
THE DEPTH SHOULD BE AT LEAST FIVE TIMES THE WIDTH OF THE OPENING OF THE DEFECT AT THE SURFACE.
A large forging is repaired by welding. Magnetic particle inspection of the repair weld reveals an irregular indication running parallel with the weld passes. It is located near the center of the bead and starts and ends by turning off slightly from the axial direction. This indication is indicative of:
WELD SHRINKAGE CRACKS
A longitudinal surface crack in a circularly magnetized part will cause:
A MAGNETIC LEAKAGE FIELD
A magnetic particle build-up from a discontinuity is strongest when the discontinuity is oriented:
90 degrees to the magnetic field
A metal that is difficult to magnetize is said to have:
low permeability.
A part is adaptable to magnetic particle inspection if:
the material is ferromagnetic
A prime consideration when selecting a powder to be used as a magnetic particle medium is to select a powder that:
provides a HIGH CONTRAST to the surface being tested
A rough forging that has received no further processing is magnetic particle teste An indication is observed to run in every direction. It appears to extend deeply into the part and perpendicular to the surface. It is very sharp. What is the probable identity of the indication?
Forging burst
A specimen may be demagnetized by which of the following methods?
1. Heat Treatment above curie temperature
2. AC coil
3. Reversing DC fields
Alternating current (AC) can be used to demagnetize a magnet and involves passing through AC through a coil placed near the magnet.
The AC current generates a magnetic field that cancels out the magnetic field of the magnet, which demagnetizes it.
An electric current through a copper wire:
Creates a Magnetic Field around the wire.
An electrical yoke produces:
a LONGITUDINAL field
An example of a irrelevant indication that would be classed as a magnetic irregularity rather than an actual discontinuity could be caused by:
AN ABRUPT CHANGE IN THE HARDNESS OF PART.
An interruption in the normal physical structure or configuration of a part which produces an MT indication is called:
a DISCONTINUITY
Applying the theory of the “Right Hand Rule,” a longitudinal surface defect in a round bar is detected by “current passing in a direction parallel to the direction of expected defects” because:
the magnetic field is at
(RIGHT ANGLES) to the defect.
What TERM is used to describe the reverse magnetizing force necessary to remove the residual magnetism in a material?
COERCIVE FORCE
Comparing parts that have been circularly magnetized and those which have been longitudinally magnetized, which retains the most objectionable residual field if not demagnetized?
LONGITUDINAL
Most of the time its going to be (Longitudinal)
Comparing parts that have been circularly magnetized and those which have been longitudinally magnetized, which retains the most objectionable residual field if not demagnetized?
Longitudinal
Demagnetization may be accomplished by ?
By HEATING a material above its Curie Point
(HEAT TREATING WORKS!)
it will kill my rare earth magnets if I leave it on a VERY-HOT pipe too long
Demagnetization:
may be easy or difficult depending on the type of material.
THE TERM used to describe materials that have a weak, negative susceptibility to magnetic fields is ?
DIAMAGNETIC
I remember that by thinking (DIE)-Magnetic or dead Most elements in the periodic table, including copper, silver, and gold, are diamagnetic.
Discontinuities in PLATE, SHEET, OR STRIP caused by pipe, inclusions, or blowholes in the original ingot which after rolling are usually flat and parallel to the outside surface are called:
LAMINATIONS.
External poles which are too strong to permit good inspection of a part are more likely to result when using:
LONGITUDINAL magnetization.
THE TERM used to describe a material that is strongly attracted to a magnet, and which can be made into a magnet
FERROMAGNETIC
I remember Ferromagnetic by thinking Furiously strong
Fluorescent magnetic particle indications should be inspected under:
BLACK LIGHT
Forging laps occur in what relation to the axial direction of a part?
MAY OCCUR ANYWHERE ON SURFACE AND MAY BEAR NO RELATION TO AXIAL DIRECTION OF THE PART
If a crack exists in a circular magnet, the attraction of magnetic particles to the crack is caused by:
a leakage field
If a current is passed through an
electrical conductor, what will surround the conductor?
a Magnetic Field
If a current of the same amperage is passed through two conductors of the same dimensions, one of which is magnetic and one of which is nonmagnetic, the magnetic field surrounding the conductors will:
be the same for both conductors.
If an overall pattern (sometimes circular lines) appears on the test surfaces, how should the inspector reprocess the test piece?
RETEST AT LOWER AMPERAGE
If wet magnetic particle suspension is not uniform, then:
1. the strength of an indication may vary
2. the interpretation of the indication may be erroneous.
In a magnetic particle test, assuming that all of the following are in the same relative position in a small part, which would be the hardest to detect?
A scratch
In longitudinal magnetization the proper TERM for calculating magnetizing force is:
AMPERE-TURNS
In magnetic particle inspection, it is best to:
make sure that parts meet specified acceptance criteria
In order to detect defects in different directions in a material by magnetic particle inspection, it is best to use:
two or more fields in different directions.
Inspecting a part by magnetizing, removing the current flow, then applying the medium is called the:
RESIDUAL METHOD
Internal splines and holes drilled parallel to or near test surfaces will cause:
Broad, and Fuzzy indications Directly aligned with the part’s internal contours.
Lines of flux are thought to leave a magnet at:
THE NORTH POLE.
Remember Santa LEAVES the NORTH POLE to come to your house
Magnetic flux lines which are parallel to a discontinuity produce:
no indications.
Magnetic lines of force:
Form a CLOSED LOOP.
Magnetic Field Lines
1. can NEVER CROSS
2. are CONTINUOUS
3. FORM CLOSED LOOPS without beginning or end.
4. They go From the NORTH POLE to the SOUTH POLE.*
Magnetic particle inspection is not a reliable method of detecting:
DEEP SEATED CAVITIES.
Mag Particle can ONLY detect discontinuities about a Quarter Inch (¼”) deep, it is for surface and near-surface flaws in ferromagnetic materials. for deeper discontinuities (RT) or (UT) would be needed
One advantage of using fluorescent particles is:
the high speed of inspection.
(no waiting on PT to dwell)
Paramagnetic materials are
Materials that are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed
(Partially) (PARA)-Magnetic
Residual magnetic particle inspection may be used when:
PARTS ARE HIGHLY RETENTIVE
Retentive means having the ability to retain
Residual magnetism may be beneficial as an aid:
in interpretation and evaluation of indications.
Resistance to demagnetization:
is greater in HARD materials than soft materials.
Since the magnetic lines of force within a bar magnet run the length of the bar, it is said to be:
LONGITUDINALLY MAGNETIZED
Remember longitudinal (most of the time its going to be that answer on the test)
Some limitations of coil magnetization techniques are that:
the coil must be of minimum diameter in relation to part.
The part has to be able to fit in the coil
Some limitations of coil magnetization techniques are that:
1. The coil must be of minimum diameter in relation to part.
2. The effective field is generally limited on either side of the coil.
3. Small diameter parts should be placed close to the coil.
4. Remember its all of the above.
Sub-surface discontinuity indications
usually appear
wide and fuzzy.
1. Because they are deeper
2. Remember Cracks open to the surface are sharp and distinct
The ability of matter to attract other matter to itself is a phenomenon associated with:
Magnetism
The accumulation of particles at a site on the part surface, collected at and held to the site by the magnetic leakage field, is called:
an indication.
The amount of amperage used for magnetic particle inspection using the prod method is determined from the:
DISTANCE BETWEEN THE PRODS
The area of maximum induced field strength using a yoke is:
the area directly between the poles.
The areas on a magnetized part from which the magnetic field is leaving or returning into the part are called:
MAGNETIC POLES
The best type of magnetic field to use to inspect a TUBULAR product for surface defects along its length is a:
Circular Field
(Tubular Dude Tubular)
The detection of deep-lying defects in
heavy weldments (1/4 inch) to 2 inches below surface) is:
Very Improbable.
The maximum depth that magnetic particles can detect a discontinuity is
1/4 inch, however 0.050 to 0.100 inch is a more realistic depth.
The end of a magnet at which the lines of flux are thought of as entering the bar is:
The South Pole.
The flux within and surrounding a magnetized part or around a conductor carrying a current is known as:
MAGNETIC FIELD
The general term used to refer to a break in the metallic continuity of the part being tested is:
Discontinuity
The lines of force that form a path around a crack in a ring magnet are called:
Leakage Flux.
The magnetic field is strongest when:
the magnetizing current is flowing.
The magnetism which remains in a piece of magnetizable material after the magnetizing force has been removed is called the:
Residual Field
The magnitude of the residual magnetic field in a specimen is dependent on:
the Strength of the Applied Magnetizing Force.
The magnitude of the residual magnetic field in a specimen is dependent on:
the Strength of the Applied Magnetizing Force.
The major factor that determines the success of magnetic particle inspection is the:
field strength.
The most effective MT method for inspection of a large casting is using:
multidirectional magnetization.
The parts are blanks cut from rolled iron bar stock and have been rough machine Inspection by continuous method reveals distinct but broken lines parallel (1/4” to 1”) with the axis on some of the pieces. These indications are indicative of:
nonmetallic inclusions.
The pattern of iron powder sprinkled on a paper placed over a bar magnet is called a:
MAGNETOGRAPH
The permeability of a material describes:
the ease with which it can be magnetized
The point at which the magnetism in a material cannot be increased even though the magnetizing force continues to increase is known as the:
SATURATION POINT
The retentivity of a material describes:
the ability to retain the magnetic field
The strength of the magnetic field induced in a part is often referred to as:
FLUX DENSITY
The strength of the wet suspension should be maintained at a given level because:
1. a low level might give weak indication.
2. a high level may give heavy background
The strongest magnetic field in a coil is at the:
INSIDE EDGE
The term used to refer to the total opposition to flow of current represented by the combined effect of resistance,inductance, and capacitance of a circuit is:
IMPEDANCE
The type of current that is best suited to detect surface discontinuities is:
A/C
The unit of measure of one line of flux per square centimeter of area is one:
GAUSS
The unit usually used to denote flux density is the:
GAUSS
The wet fluorescent magnetic particle inspection method is the same as the standard wet magnetic particle method except for requirements for:
BLACK LIGHT
To detect lengthwise defects on the inside diameter of hollow parts, you should:
pass current through a central conductor.
Using the residual test method, a number of parts are magnetized and laid on a rack prior to application of magnetic particles. Why is it important that they do not rub or touch each other?
IT MAY CAUSE MAGNETIC WRITING.
What are the three causes of irrelevant indications?
1. CHANGE OF SECTION THICKNESS
2. VERY HIGH AMPERAGE
3. DRILLED HOLE NEAR SURFACE
What equipment is used to determine if a part has been demagnetized?
A field meter
What is not a discontinuity common to forged products
Shrinkage
What method provides greater sensitivity, particularly in locating sub-surface discontinuities?
Continuous
What rule describes the direction of current flow (+ to -) when lines of magnetic force surround a conductor?
Right hand rule
What type of magnetization uses the formula: Ampere-turns = 45,000/(L/D)?
Longitudinal
What wattage is most commonly used for mercury vapor bulbs for portable fluorescent magnetic particle inspection?
100 watts
When a magnetic field is induced in a part with prods spaced six inches apart, the field is:
Circular.
When adding concentrate to any wet magnetic particle suspension liquid it is common practice:
1. to add powder directly to the suspension liquid
2. and to make a small, slurry-like test mixture of powder
When magnetic material is placed into a coil, the magnetic lines of flux concentrate themselves in the material and:
create a longitudinal magnetic field
When magnetizing a weld in two directions, and if the current used in the first direction is 750 amps and the current in the second direction is 400 amps, which of the following is true?
The part should be checked to see if demagnetization between operations is necessary.
When preparing a bath it is important to have the bath strength at a proper level, as too many particles can result in:
masking the indications.
When preparing an inspection bath, the amount of magnetic particles per gallon of fluid is called its:
strength or concentration.
Its like a drink how (Strong) you want that drink?
When testing a bar with an L/D ratio of four in a ten-turn coil, the required current would be:
1125 amperes.
When testing for fine shallow surface cracks, the preferred MT method should be:
WET A/C
When the most complete demagnetization available is desired and demagnetization is to be accomplished by placing the part in a coil energized with AC of progressively decreasing amperage, the following orientation of the long axis of the part is most desirable:
East-West
When there is absolutely no pattern or distribution of magnetic particles, the possible cause is that:
1. The material is Nonmagnetic
2. The amperage setting is too low
3. No current is being applied
When using a dry magnetic particle powder, the proper way to apply it to the part is to:
FLOAT THE PARTICLES TO INSPECTION SURFACE AS GENTLY AS POSSIBLE.
When using the wet continuous method, the flow of suspension from the hose should be shut off:
while the current is flowing.
When using the wet method, why should a high velocity flow of wet method bath over surfaces following removal of the magnetizing current not be used?
It may wash away a fine or weakly held indication.
When using the wet particles in water suspension, wetting agents are added to:
INSURE THE PROPER WETTING OF PART
Where particles are attracted to a site on the surface of a part by a magnetic leakage field which is due to a condition such as a crack, lap, or other condition not acceptable to the applicable standards for the part, then we have:
A DEFECT
Which brings out surface indications most clearly?
AC
Which form of magnetization is easiest to control in most parts?
CIRCULAR MAGNETIZATION
Which of the following can be magnetized?
1.IRON
2.NICKEL
3.COBALT
Which of the following can cause non-relevant magnetic particle indications?
1. Joints between dissimilar metals
2. Brazed joints
3. Roughing tool cuts on surface
Which of the following casting defects is caused by non-uniform cooling resulting in stresses which rupture the surface of the metal?
HOT TEARS
Which of the following is a commonly used technique for preserving MT powder patterns?
1.Clear Lacquer
2.Transparent Tape
3.Photography
Which of the following is an advantage of magnetic particle testing over penetrant testing?
1. It can detect surface discontinuities with foreign material imbedded in them.
2. It is faster on individual parts.
3. It can detect near-surface discontinuities.
4. All of the above
Which of the following is an advantage of the dry method over the wet method?
It is easier to use for field inspection with portable equipment.
Which of the following is an advantage of the dry method over the wet method?
It is easier to use for field inspection with portable equipment.
Which of the following is most often used for dry magnetic particle inspection?
Half Wave Rectified Alternating Current (HWAC)
Half Wave Rectified Alternating Current (HWAC) When single phase alternating current is passed through a rectifier, current is allowed to flow in only one direction. The reverse half of each cycle is blocked out so that a one directional, pulsating current is produced. The current rises from zero to a maximum and then returns to zero.
Which of the following is not an acceptable technique for removing a thin film of oil or grease prior to magnetic particle testing?
Brush the surface with power wire brush.
Which of the following is the most effective method for the detection of extremely deep-lying defects?
Dry continuous method using half wave rectified current with prods
Which of the following will best define surface cracks?
AC
Which of the following will produce circular magnetism?
Passing current through prods
Which of these cracks may appear as an irregular, checked, or scattered pattern of fine lines usually caused by local overheating?
GRINDING CRACKS
Which residual field is most difficult to demagnetize?
CIRCULAR
Which statement is true when related to magnetic lines of force?
1. They never cross
2. They are most dense at the poles of a magnet
3. They seek the path of least resistance
Which technique is the most sensitive?
Continuous
Which type of current has a “skin effect”?
AC
Why are large soft contact areas such as lead or copper braid used for surfaces or headstocks?
1. TO INCREASE THE CONTACT AREA
2. REDUCE THE POSSIBILITY OF BURNING THE PART
Why are magnetic particles available in different colors?
1. For color contrast with the part surface
2. To Enhance the detection of indications
Why is it preferable to disassemble parts before magnetic particle inspection?
1. Disassembly makes all surface areas visible.
2. Interfaces will create leakage fields which may confuse the inspection.
3. It is usually easier to handle the disassembled parts.
4. All of the above.
Why should parts be cleaned after demagnetization?
To assure that the magnetic particles are removed
