CGSB Study Q’s Flashcards
Which of the following materials can be examined by the MPI method?
A) medium alloy steels
B) carbon steels
C) aluminum
D) magnesium
E) brass-copper
F) bronze
G) lead
H) ferro magnetic metals
Medium alloy steels, carbon steels and ferro magnetic metals
Any mass of iron, steel, or material capable of attracting other like masses is known as what?
Magnet
When the flux lines or lines of force traverse the part in a direction essentially parallel to the long axis of the test piece, the lines of force tend to return through the air from one pole to the other forming a closed magnetic field. This is known as what type of magnetism?
A) circular
B) longitudinal
C) transverse
D) continuous
B) longitudinal
In what manner has the part been magnetized when the magnetic flux always has a completely ferromagnetic return?
A) circular
B) longitudinal
C) transverse
D) continuous
A) circular
When longitudinally magnetizing a part in a coil, how is the effective amperage determined?
A) amperage applied multiplied by number of turns in coil
B) number of turns in coil multiplied by width of part
C) amperage indicated by ammeter
D) I = E/R
A) amperage applied multiplied by number of turns in coil
Through what medium are discontinuities demonstrated in magnetic particle inspection?
A) finely divided ferromagnetic particles of high permeability, low coercive force and very high retentivity
B) finely divided ferromagnetic particles of high permeability and low retentivity
C) red oil like substance with good capillary action
D) metal shavings and particles
B) finely divided ferromagnetic particles of high permeability and low retentivity
When the finely divided ferromagnetic particles are in oil suspension, the test method is called;
A) oil and whiting technique
B) oil suspension technique
C) wet method
D) spray or dip method
C) wet method
A sharp variation in the permeability of material being inspected causing a magnetic particle indication is called a:
A) defect
B) discontinuity
C) nonrelevant indication
D) false indication
B) discontinuity
What is the most effective means of magnetization for the detection of extremely deep-lying defects? (2)
A) dry residual method using DC with surge
B) wet continuous method using half wave with rectified current
C) dry continuous method using DC with surge
D) dry continuous method using half wave rectified current with prods
C) dry continuous method using DC with surge AND, D) dry continuous method using half wave rectified current with prods
How are the particles held to the part in false indications?
A) magnetic pole
B) discontinuity
C) gravity or mechanically
D) leakage field
C) gravity or mechanically
Assuming that a part is to be magnetized longitudinally after a circular shot, is it necessary to demagnetized between shots? Why?
No because the second shot will cancel out the previous field
The Tesla is the unit of measurement of the magnetic field strength. What is the term which is used in this regard?
A) current
B) flux density
C) lines of force
D) residual field
B) flux density
What type of current is better for locating subsurface defects?
A) AC
B) DC
B) DC
Define magnetic poles:
The ability of a magnet to attract or repel is not uniform over its surface, but concentrated at local areas called poles.
Each magnetic has at least two opposite poles: one which is attracted to the Earth’s North Pole and called the North Pole of the magnet, while the other is attracted to the Earth’s South Pole which is called the South Pole of the magnet.
Define permanent magnets:
Occur in nature as the mineral “magnetite” or made by artificially magnetizing hardened steels or alloys such as alnico.
They will retain their magnetic field after the magnetizing influence has been removed.
Is the compass test for residual magnetism applicable to parts magnetized circularly?
No
What are three causes of nonrelevant indications?
A) lack of fusion
B) change in section
C) drilled holes near test surface
D) grinding cracks
E) very high amperage
F) blow holes
Change in section, drilled holes near test surface and very high amperage
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 together?
False indications will be formed at localized poles at points of contact
Define remnant magnetism:
The residual magnetism remaining in a magnetic circuit after the magnetizing influence has been removed
Define temporary magnets:
Retain only a very small field after the magnetizing influence has been removed.
The magnetizing field surrounding a bar magnet is most dense:
A) near the middle of the magnet
B) at ends of the magnet
C) 300 mm from the magnet
B) at ends of the magnet
To locate defects, part should be magnetized so that the long axis of possible defects:
A) is at right angle to lines of force
B) is parallel to lines of force
A) is at right angle to lines of force
Residual magnetic particle inspection may be used when: (2)
A) parts are irregular in shape
B) parts are highly retentive
C) parts are highly stressed
D) to help evaluate continuous method indications
B) parts are highly retentive AND D) to help evaluate continuous method indications
When electric current is passed through a coil, the direction of the lines of flux induces in a rod positioned within the coil is:
A) circular
B) unknown
C) longitudinal
D) vector
C) longitudinal
Magnetic particle inspection is not a reliable method of detecting: (2)
A) laps
B) laminations
C) deep seated cavities
D) seams
B) laminations and C) deep seated cavities
Define solenoid:
An electric conductor formed into coils
Name four common ferromagnetic materials which can be inspected by the magnetic particle method.
Iron, nickel, cobalt and some steels
Which two methods which will produce circular magnetism?
A) passing current through the test part
B) placing test part in a solenoid
C) pass current though a central conductor
À) passing current through the test part AND C) pass current through a central conductor
What type of current is usually used with a demagnetizer?
Alternating Current
Is it possible to magnetic with DC?
Yes
Magnetic lines of force are:
A) isolated mono-poles
B) elongated bi-poles
C) manifestations of the “string theory”
D) imaginary concepts for mapping magnetic fields
D) imaginary concepts for mapping magnetic fields
In a ferromagnetic material, a region where all the “atomic moments” are aligned parallel to each other is called a:
A) magnetic zone
B) confederation
C) domain
D) magnetic junta
C) domain
In order to be detectable by magnetic particle testing, a flaw must:
A) be surface breaking
B) be no deeper than 1 mm below the surface
C) produce a leakage field at the test surface
D) all of the above
C) produce a leakage field at the test surface
A good in an otherwise homogenous magnetized material presents itself as a point magnetic dipole. This is the basis for:
A) magnetic particle flaw detection
B) multifrequency eddy current
C) para-magnetism
D) de-magnetization
A) magnetic particle flaw detection
The opposition to the formation of a magnetic flux in a magnetic circuit is referred to as:
A) reactance
B) reluctance
C) resistance
D) antimagnetics
C) resistance
The value of H applied to bring the residual value of B to zero is called:
A) saturation field
B) demagnetization value
C) coercive force
D) phase reversal factor
C) coercive force
A magnetic particle build up from a discontinuity is strongest when the discontinuity is oriented:
A) 180• to the magnetic field
B) 45• to the magnetic field
C) 90• to the magnetic field
D) 90• to the current flow
C) 90• to the magnetic field
Grain boundaries are areas of a metal micro structure:
A) where high melting point constituents are concentrated
B) made up of rows of atoms arrayed in straight lines
C) that are not attacked by etchants and generally stand in relief during metallographic examination
D) where low melting impurities tend to concentrate
D) where low melting impurities tend to concentrate
Steels that contain more than 0.30% carbon, if welded, are prone to which type of discontinuity?
A) HAZ cracking
B) porosity
C) incomplete fusion
D) slag formation
A) HAZ cracking
What are the three main types of corrosion?
A) General corrosion, pitting and intergranular corrosion
B) General corrosion, pitting and transgranular corrosion
C) General corrosion, intergranular corrosion and transgranular corrosion
D) transgranular corrosion, intergranular corrosion and pitting
A) General corrosion, pitting and intergranular corrosion
What is the cause of the cracks in the HAZ?
A) a thermal cycle that increases hardness and reduces brittleness
B) a thermal cycle that reduces hardness and increases brittleness
C) a thermal cycle that reduces hardness and brittleness
D) a thermal cycle that increases hardness and brittleness
D) a thermal cycle that INCREASES hardness AND brittleness
Elongated configurations of foreign substances aligned in the direction of working wrought metals are called:
A) slag
B) inclusions
C) stringers
D) worms
C) stringers
A defect which bears no relation to the direction of metal grains is:
A) intergranular corrosion
B) grinding crack
C) quenching crack
D) lamellar tearing
B) grinding crack
The strength of a circular magnetic field is not affected by the _________ of a part:
A) permeability
B) diameter
C) length
D) any of the above
C) length
Given a steel bar 1 foot long and 3 inches diameter, what current should you use for the coil shot with a 3 turn coil (part placed at bottom of coil)?
A) 100 amps
B) 2000 amps
C) 4000 amps
D) 6000 amps
B) 2000 amps
When welds are required to have only partial penetration use of HWDC yokes often give rise to nonrelevant indications. This problem can be eliminated by:
A) using an AC yoke
B) increasing leg spacing
C) reducing magnetizing current
D) using a pie gauge
A) using an AC yoke
The best way to demagnetize a long tube would be:
A) reversing DC with a central conductor
B) pulsating AC with a central conductor
C) a portable yoke
D) passing the tube through an AC coil
A) reversing DC with a central conductor
Unless subsequently heat treated, all parts must be demagnetized after inspection.
True or False
False
When mixing magnetic particle paste with oil, it is permissible to mix directly in the equipment tank.
True or False
False
Which of the following is most often used for dry magnetic particle inspection?
A) cycle direct current
B) half wave rectified alternating current
C) high voltage, low amperage current
D) direct current from electrolytic cells
B) half wave rectified alternating current
Why should parts be clean prior to inspection? (2)
A) so the operator can stay clean
B) to assure correct indications
C) to keep suspension clean
D) to help make final cleaning easier
B) to assure correct indications AND C) to keep suspension clean
Why are parts demagnetized? (3)
A) so that parts can be handled easier
B) to assure removal of residual magnetism
C) to assist in cleaning of parts
D) if not done, subsequent machining operations may be more difficult to accomplish satisfactory
B) to assure removal of residual magnetism, C) to assist in cleaning of parts and D) if not done, subsequent machining operations may be more difficult to accomplish satisfactory
Why is black light used with fluorescent magnetic particle inspection? (2)
A) to protect the operator’s eyes
B) indications are more easily seen
C) to bring out the dye
D) to bring out the magnetism
B) indications are more easily seen AND C) to bring out the dye
Why should parts be cleaned after demagnetization? (2)
A) to assure that magnetic particles are removed
B) to prevent corrosive action
C) to save the solids of the suspension
D) to prevent cracking during heat treatment
A) to assure that magnetic particles are removed AND B) to prevent corrosive action
If many like parts are coming through inspection and are found rejectable, the thing to do is:
A) tell operator
B) inform supervisor
C) determine cause
D) scrap like parts and save test time
B) inform supervisor
Which of the following apply to magnetizing by use of a central conductor?
A) effective way to develop magnetic field on inside surface
B) enable operator to magnetize several washer shaped parts at same time
C) reduces danger of burning parts due to poor contact
D) can be used for residual and/or continuous method
E) all of the above
E) all of the above
What is the magnetizing force expressed in for circular magnetism?
Amperes
What is the magnetizing force expressed in for longitudinal magnetism?
Ampere turns
When demagnetizing with the prod method the initial magnetizing force used to demagnetize must be:
A) higher than that used to magnetize the part
B) lower than that used to magnetize the part
C) the same as that used to magnetize the part
D) doesn’t matter
A) higher than that used to magnetize the part
If a bar magnet were bent into a circular shape and the ends faced together (without heating), it would:
A) lose its polarity
B) increase its magnetization
C) still have a north and South Pole
D)develop a third pole
C) still have a North and South Pole
A crack in a circular (completely closed) magnet will cause:
A) the magnetic field to die out
B) polarity
C) magnetization
D) a current to flow
B) polarity
If a bar magnet is bent into a circular shape and the ends fused together in a perfect weld, it would:
A) lose its magnetism
B) lose its polarity
C) increase its magnetization
D) increase its polarity
B) lose its polarity
