MT lv.1 Flashcards
Prior to the use of magnetic particles to detect flaws by magnetic methods, flaws could be located in iron pieces using
a) Hall detectors
b) ordinary magnetic compasses
c) electro scopes
d) electromagnetic resonance
b) ordinary magnetic compasses
The ampere is a unit of
a) electric current
b) electromotive force
c) electromagnetic force
d) magnetic intensity
a) electric current
Total current in two parallel conductors can be determined by knowing the distance between the conductors and the
a) dielectric constant of air
b) resistivity of the conductors
c) right hand rule
d) magnetic force exerted per unit length of wire
d) magnetic force exerted per unit length of wire
The units Webers per square metre (Wb/m^2) are used to quantify a:
a) magnetic induction field
b) magnetic dipole
c) magnetic monopole
d) magnetic force
a) magnetic induction field
Magnetic field lines are
a) always concentric rings
b) symbolic only, and used to indicate spatial direction of the field
c) a result of the van Allan belts
d) of uniform density
b) symbolic only, and used to indicate spatial direction of the field
A void in an otherwise homogenous magnetized material presents itself as a point magnetic dipole. This is the basis for
a) magnetic particle flaw detection
b) multi frequency eddy current
c) para-magnetism
d) de-magnetisation
a) magnetic particle flaw detection
Magnetic properties of materials are a result of
a) electric currents on the atomic and sub-atomic scale
b) the strong nuclear force
c) the ratio of protons to neutrons in the material
d) the weak nuclear force
a) electric currents on the atomic and sub-atomic scale
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
When discussing magnetization and its effects the magnetic induction field is usually represented by the letter
a) B
b) H
c) M
d) Z
a) B
When discussing magnetization and its effects the magnetic field intensity, or as its also called, the magnetic field is represented by the letter
a) B
b) H
c) M
d) Z
b) H
The phenomenon whereby the magnetization of a ferromagnetic sample lags the applied cyclic magnetic field is referred to as
a) phase lag
b) Doppler effect
c) hysteresis
d) demagnetization
c) hysteresis
When a hysteresis curve is generated for a ferromagnetic material, a magnetic field remains in the material when the applied field is returned to zero. This field is called the
a) coercive force
b) induction field
c) residual induction
d) resultant vector
c) residual induction
The value of H applied to bring the residual value of B to zero is called
a) saturation field
b) demagnetization value
c) induction coercive force
d) phase reversal factor
c) induction coercive force
In order to be detectable by magnetic particle testing, a flaw must
a) be surface breaking
b) be no deeper than 1mm below the surface
c) produce a perturbation of the induction field at the test surface
d) all of the above
c) produce a perturbation of the induction field at the test surface
To detect a flaw by magnetic particle methods, techniques are developed to
a) maximize field perturbations in the region of a flaw
b) optimize retentivity of the material
c) propagate the flaw by Barkhausen jumps
d) all of the above
a) maximize field perturbations in the region of a flaw
Sensitivity of the magnetic particle method depends on the
a) absolute magnitude of the induced field perturbation
b) spatial gradient of the induced field perturbation
c) magnitude of the applied field
d) surface flux density of the test piece
b) spatial gradient of the induced field perturbation
Magnetic particle testing has an advantage over liquid penetrant testing because it can
a) be used on ferromagnetic materials
b) locate surface defects
c) locate subsurface defects
d) be cheaper to use
c) locate subsurface defects
Magnetic particle testing is a practical test method to inspect.
a) glass
b) ceramics
c) aluminum castings
d) none of the above
d) none of the above
Which is not an essential step in magnetic particle testing?
a) establish a suitable magnetic flux in the test piece
b) application of magnetic particles
c) examination of test piece
d) post cleaning of test piece to remove magnetic particles
d) post cleaning of test piece to remove magnetic particles
Inherent discontinuities are formed during
a) initial melting and refining of the metal
b) primary processing
c) secondary processing and manufacturing
d) in-service use
a) initial melting and refining of the metal
When a discontinuity causes the magnetic field lines to be forced out of the specimen into the air, the field in the air is called a
a) force field
b) leakage field
c) flux field
d) flaw field
b) leakage field
Magnetic particles are available in many colours to
a) indicate degree of permeability
b) optimize visibility
c) indicate degree of rententivity
d) permit the inspector to choose a colour that will not clash with his/her clothing
b) optimize visibility
The deeper a subsurface defect gets below the surface
a) the greater the flux leakage it produces
b) the harder it gets to magnetize the part
c) the larger it must be to be detectable
d) all of the above
c) the larger it must be to be detectable
In order to detect a flaw by magnetic particle testing the magnetic field must
a) alternate
b) pulse
c) run parallel to the principal plane of the flaw
d) intercept the principal plane of the flaw
d) intercept the principal plane of the flaw
The cgs unit of magnetizing force (H) is the
a) Oersted
b) Gauss
c) Tesla
d) Weber
a) Oersted
The cgs unit of flux density (B) is the
a) Oersted
b) Gauss
c) Tesla
d) Weber
b) Gauss
If the ends of a long bar magnet are bent to form a circle and the ends perfectly fused together the result will be
a) the magnet will no longer attract ferromagnetic material
b) a circular magnetic field
c) no magnetic flux leakage field
d) all of the above
d) all of the above
A bar magnet would be considered to be
a) circularly magnetized
b) longitudinally magnetized
c) electromagnetically poled
d) cross-polarized
b) longitudinally magnetized
Which of the following is not a characteristic of magnetic flux lines?
a) they attract each other
b) they form continuous loops
c) they do not cross each other
d) they decrease in intensity with distance from the surface
a) they attract each other
Inside a bar magnet magnetic flux lines are considered to flow from
a) north to south
b) south to north
c) east to west
d) west to east
b) south to north
The direction of magnetic lines of force around a current carrying conductor is
a) parallel to the conductor
b) at right angles to the conductor
c) 45 degrees out of phase to the applied current
d) parallel or perpendicular to the conductor depending on which current flow convention is used
b) at right angles to the conductor
If a nail is brought to a bar magnet it is held by the magnet. If another nail is now brought to touch the first nail it is held to the first nail. Subsequent nails can be held in a long chain. This is a result of
a) induced magnetism
b) nail bonding
c) domain transfer
d) natural attraction of nail points to nail heads
a) induced magnetism
The end of the compass needle that points towards the northern region of the earth is called
a) the north seeking pole
b) the magnetic north pole
c) the magnetic south pole
d) both a and b
d) both a and b
The magnetic north pole is located
a) at 90ø north latitude
b) somewhere in northern Canada
c) at the north geographic pole
d) at Greenwich England
b) somewhere in northern Canada
A single line of force represents the unit of magnetic flux in a field. This is called a(n)
a) oersted
b) gauss
c) weber
d) maxwell
d) maxwell
A magnet can lose its magnetism by
a) heating
b) hammering
c) both a and b
d) no known means
c) both a and b
Removal of magnetism from a part is termed
a) domain scattering
b) demagnetization
c) stress relieving
d) the Hall effect
b) demagnetization
A permanent magnet configured such that both north and south poles are adjacent is usually termed a
a) longitudinal magnet
b) circular magnet
c) parallel magnet
d) horseshoe magnet
d) horseshoe magnet
The “image” of a magnetic field produced by placing a magnet under a paper and sprinkling iron fillings on the top of the paper is called
a) magnetic projection
b) magnetic holography
c) a magnetograph
d) flux painting
c) a magnetograph
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
Electric current which at regular intervals reverses its direction of flow is called
a) AC
b) DC
c) alternating
d) both a and c
d) both a and c
In direct current flow electric circuits the unit of current is the
a) ampere
b) ohm
c) mho
d) volt
a) ampere
In alternating current electric circuits the unit of current flow is the
a) ampere
b) ohm
c) volt
d) deci Bell
a) ampere
Opposition to electric current flow in a D.C. circuit is termed
a) ohmage
b) resistance
c) reactance
d) reluctance
b) resistance
The unit of electrical resistance is the
a) ampere
b) coulomb
c) ohm
d) volt
c) ohm
The unit of potential difference in an electric circuit is the
a) ampere
b) ohm
c) volt
d) Coulomb
c) volt
A ferromagnetic material surrounded by a current carrying coil becomes
a) diamagnetic
b) magnetized
c) an electromagnet
d) both b and c
d) both b and c
The unit of inductance is the
a) farad
b) henry
c) Coulomb
d) abvolt
b) henry
The ability of a material to emit visible light while being irradiated by UV light is called
a) fluorescence
b) phosphorescence
c) iridescence
d) Birefringence
a) fluorescence
The typical duration of a coil shot is
a) a fraction of a second
b) 1 second
c) 2 seconds
d) 5 seconds
a) a fraction of a second
The clamping contacts on a large stationary magnetic particle testing unit are called
a) prods
b) heads
c) poles
d) shunts
b) heads
When a part is magnetized such that the flux lines run essentially parallel to the long axis of the part it is called
a) parallel magnetization
b) circular magnetization
c) longitudinal magnetization
d) a long shot
c) longitudinal magnetization
In magnetic particle testing prods are
a) hand held electrodes
b) never used
c) used for longitudinal magnetization
d) substitutes for the central conductor
a) hand held electrodes
The relationship relating electric current flow, voltage and resistance in electric circuits is
a) relativity
b) Ohm’s law
c) Snell’s law
d) Kirchoff’s law
b) Ohm’s law
In electric circuit terminology the usual symbol for current is
a) A
b) E
c) I
d) C
c) I
In electric circuit terminology, the usual symbol for voltage is
a) E
b) I
c) V
d) both a) and c) are used
d) both a) and c) are used
The common unit of electric power is
a) amperes
b) volts
c) watts
d) horsepower
c) watts
To determine the direction of magnetic field lines in a conductor (assuming - to + current flow) you can use
a) the left hand rule
b) the right hand rule
c) a Galvanometer
d) a Wheatstone bridge
a) the left hand rule
For a single straight conductor, assuming modern theory current flow, the fingers on the left hand point
a) in the direction of the magnetic field lines
b) against the magnetic field lines
c) in the directions of the electron flow
d) opposite to the electron flow
a) in the direction of the magnetic field lines
In the left hand rule as applied to a solenoid, the fingers point in the direction of
a) north
b) south
c) current flow
d) force on the conductor
c) current flow
In the left hand rule, as it applies to a solenoid, the thumb point in the direction of
a) north
b) south
c) current flow
d) force on the conductor
a) north
The relative amount of flux linkage between two coils (as in a transformer) is called
a) mutual inductance
b) figure of merit
c) coupling coefficient
d) flux factor
c) coupling coefficient
In order to operate as a transformer, two coils must be linked by a(n)
a) iron core
b) air core
c) alternating magnetic field
d) copper wire
c) alternating magnetic field
The difference between a yoke and prods in magnetic particle testing is
a) a yoke produces a circular field and prods a longitudinal
b) a yoke produces a longitudinal field and prods a circular
c) a yoke produces a longitudinal field and prods a parallel
d) none, the both produce circular fields
b) a yoke produces a longitudinal field and prods a circular
As one increases the size of the MPI test system from small yokes and portable units to large bench units the single most significant difference is
a) length of piece that can be tested
b) the ability to use liquid suspensions in the big units
c) the amount of magnetizing current available
d) type of magnetic field that can be generated
c) the amount of magnetizing current available
When single phase AC is halfwave rectified it is sometimes called half wave direct current. The reference to direct current is because
a) Lenz’s law applies
b) current amplitude does not change
c) current flow direction does not change
d) all of the above
d) all of the above
A part that has been magnetized by ________ requires demagnetization.
a) mechanical means
b) magnetic particle testing
c) a magnetic chuck
d) none of the above
d) none of the above
Demagnetization of a part is usually required when the part is
a) used near magnetically affected instruments
b) part of a moving assembly
c) to be finish machined
d) all of the above
d) all of the above
The Curie point is
a) 320øC.
b) 1650øF.
c) varies with the position on the earth relative to the north magnetic pole
d) varies for each ferromagnetic alloy
d) varies for each ferromagnetic alloy
The number of reversals normally required to properly demagnetize a part using electromagnetic means is
a) 1
b) 2-5
c) 10-30
d) 50-100
c) 10-30
Demagnetization can be accomplished using
a) A.C.
b) D.C.
c) a yoke
d) all of the above
d) all of the above
The advantage of using reversing D.C. for demagnetization is
a) low heating effect
b) deep penetration
c) only one reversal is needed
d) all of the above
b) deep penetration
The magnetic flux in a part increases as applied field is increased. The flux moves along the virgin curve of the hysteresis curve
a) once each cycle of applied A.C. field
b) twice each cycle of applied A.C. field
c) only once when the part is completely demagnetized
d) for paramagnetic materials only
c) only once when the part is completely demagnetized
For demagnetizing large parts, field reversals are usually _________.
a) lower frequency than for small parts
b) higher frequency than for small parts
c) the same frequency as for small parts
d) not needed
a) lower frequency than for small parts
For best demagnetization results using a coil with A.C. and passing parts through it you should
a) pass the part through with its long axis parallel to the coil axis
b) hold the part close to the coil
c) both a and b
d) switch the current on only when the part is centered along its length in the coil
c) both a and b
Small parts can be demagnetized in multiple lots by passing them through an A.C. coil provided they are
a) stacked in a basket
b) apart in single layer
c) oriented long axis parallel to coil axis
d) both b and c
d) both b and c
For rings and hollow parts a handy means of A.C. demagnetization is
a) using a yoke
b) a central conductor using decreasing current
c) surge pulses through prod contacts
d) swinging field technique
b) a central conductor using decreasing current
The most likely tool you would use to determine if a part has been adequately demagnetized is the
a) Hall detector
b) field meter
c) electrogram
d) magnetometer
b) field meter
A problem with doing a head shot on a ball bearing is
a) arc burns damage the surface
b) no defects are found
c) the field is distorted too much
d) they cannot be demagnetized
a) arc burns damage the surface
The two classifications of media in MPI are
a) fluorescent and non-fluorescent
b) wet and dry
c) magnetic and para-magnetic
d) high temperature and low temper
b) wet and dry
What shape is used for the particles used in magnetic particle testing?
a) acicular (elongated)
b) spherical and flake
c) irregular
d) all of the above
d) all of the above
Which is a type of particle available for magnetic particle testing?
a) wet visible particles
b) dry fluorescent particles
c) dry visible particles
d) all of the above
d) all of the above
What is the result if magnetic particles are made of a material of high coercive force?
a) decreased mobility
b) high background
c) masking of defects
d) all of the above
d) all of the above
Large sized particles are not used in wet magnetic particle testing because
a) they drop from suspension too quickly
b) they form misleading indications called drainage lines
c) circulation pumps cannot move them off the tank bottom
d) both a and b
d) both a and b
The purpose of large particles in the dry powder mix is to
a) detect large defects
b) reduced background by “sweeping”
c) locate subsurface defects
d) both a and b
d) both a and b
The reason agglomerations of fine magnetic particles tend to move through the liquid they are suspended in is
a) increased mass
b) increased field strength
c) both a and b
d) the fluid dynamic shape that is taken on
c) both a and b
Maximum particle mobility is had for dry magnetic particles with _______ shape.
a) spherical
b) elongated
c) flake
d) irregular
a) spherical
The reason for adding a portion of spherical shaped magnetic particles to a batch of elongated shaped dry powder magnetic particles is to
a) increase density
b) increase mobility
c) increase sensitivity
d) increase contrast
b) increase mobility
The difference in colour between an MPI indication and the background colour of the part tested is critical in evaluation of a part. The colour difference is referred to as
a) contrast
b) lumens
c) luminosity
d) indication intensity
a) contrast
Dry magnetic particles should be applied so they have a minimum velocity when they reach the test part. The reason being
a) to avoid a peening effect on the part
b) to ensure they can be caught by leakage fields
c) so pigments are not knocked off
d) all of the above
b) to ensure they can be caught by leakage fields
The choice of colour of dry magnetic particle to use depends on
a) colour of part being tested
b) ambient light at the test location
c) type of defect required to be found
d) both a and b
d) both a and b
What is the name of the technique whereby a part is magnetized first and the particles applied after the magnetizing force is removed?
a) residual method
b) leakage field method
c) time lapse MPI
d) delay technique
a) residual method
What is the name of the MPI technique whereby the magnetic particles are applied to a part only during the time the magnetizing force is applied?
a) the inertial technique
b) the continuous method
c) the synchronized method
d) the time-metered method
b) the continuous method
The localized overheating of a part being magnetic particle tested, arising from high resistance or sparking at the electrical contact point is
a) burning (or arcing)
b) coagulation
c) feedback
d) background noise
a) burning (or arcing)
The general appearance of the test surface on which indications are to be viewed is termed
a) purple haze
b) backdrop
c) background
d) carrier
c) background
The purpose of contact pads placed on the electrodes used in MPI is
a) ornamental
b) to redirect flux patterns
c) top secret
d) to improve electrical contact
d) to improve electrical contact
The buildup of magnetic particles due to excessive magnetization of the part under test is called
a) furring
b) fall-out
c) magnetic hair
d) magnetic writing
a) furring
A “split-coil” attachment for MPI use is used for
a) varying the number of turns in a coil
b) varying the magnetizing current strength in the part
c) positioning over a part with no free ends for normal coil access
d) both a and b
c) positioning over a part with no free ends for normal coil access
A five turn coil on a bench unit is 30cm diameter. If 2000amps are passed through it will result in
a) 10,000 ampere turns
b) 12,000 ampere turns
c) 60,000 ampere turns
d) unknown
a) 10,000 ampere turns
The process whereby the magnitude and significance of an indication is determined is termed
a) examination
b) interpretation
c) evaluation
d) rejection
c) evaluation
A “keeper” is used on a permanent magnet to complete the magnetic circuit. The purpose of this is to
a) prevent loss of magnetism
b) provide an intensification of flux
c) provide longitudinal magnetization
d) provide circular magnetization
a) prevent loss of magnetism
Parallel magnetization is
a) not possible
b) not a recommended practice for MPI testing
c) the same as longitudinal magnetization
d) a substitute for overall magnetization
b) not a recommended practice for MPI testing
The non-relevant indication resulting when the surface of a magnetized part comes in contact with another piece of ferromagnetic material is
a) bearding
b) furring
c) magnetic writing
d) break lines
c) magnetic writing
Which of the following materials has the highest relative permeability
a) iron
b) vacuum
c) air
d) gold
a) iron
The two basic decisions made before an MPI test is carried out are
a) minimum size of defect to find and type of current to use
b) minimum size of defect to find and type of particle to use
c) type of current and type of particle to use
d) which code to use and how fast to perform the test
c) type of current and type of particle to use
To detect a flaw in a low carbon steel shaft, if you suspect the flaw is about 6mm (1/4”) below the surface which method would you use?
a) A.C.
b) half wave rectified A.C.
c) an A.C. yoke
d) a pair of permanent magnets
b) half wave rectified A.C.
Which is the best material for detecting defects wholly below the surface using MPI tests?
a) dry powder
b) wet fluorescent
c) wet visible
d) all are about equal for the same current
a) dry powder
Low carbon steels must have the continuous method of MPI testing used on them due to
a) the skin effect
b) the Hall effect
c) low retentivity
d) carborization occurring from the residual method
c) low retentivity
The magnetizing current in the continuous wet method, when the bath is applied by flooding from a nozzle, is usually applied
a) during the whole time it takes to wet the part
b) immediately after flooding is stopped
c) after the bath stops dripping from the part
d) both before and after bath application
b) immediately after flooding is stopped
The normal duration required for a magnetizing “shot” in the continuous wet method is about
a) 1/4 to 1/2 second
b) 1/2 to 1 second
c) 1 to 2 seconds
d) 2 to 5 seconds
a) 1/4 to 1/2 second
Prods or clamps are used to produce which type of magnetization?
a) longitudinal
b) circular
c) parallel
d) swinging field
b) circular
When a central conductor is used inside a tube the type of magnetization employed for the testing of that tube is
a) longitudinal
b) circular
c) parallel
d) swinging field
b) circular
Generally an electromagnetic yoke is considered to be used for producing
a) longitudinal magnetization
b) circular magnetization
c) field distortions
d) either a or b depending on if it is an A.C. or D.C. yoke
a) longitudinal magnetization
Field strengths of the magnetic field produced by a solenoid (or coil) can be changed by
a) changing the number of coil loops
b) changing the current in the coil
c) both a and b
d) none of the above
c) both a and b
For the same diameter, length and current used, the difference between using a non-magnetic and a ferro-magnetic central conductor is
a) magnitude of magnetic field on the outside surface of the conductor
b) directions of defects detected
c) both a and b
d) no difference
a) magnitude of magnetic field on the outside surface
When performing MPI using prods, the current used depends on
a) prod spacing
b) part thickness
c) prod diameter
d) both a and b
d) both a and b
The guideline to use 40 amperes of magnetizing current per mm of part diameter applies to
a) head shots
b) coil shots
c) central conductor shots
d) de-magnetization
a) head shots
If using the rule of thumb of 40 amps per mm of part diameter for a head shot, what current is required to magnetize a 20mm diameter copper bar?
a) 400 amp
b) 800 amp
c) 1600 amp
d) none of the above
d) none of the above
If 24000 ampere turns are required for coil shot using a 5 turn bench coil, what should your current setting be?
a) 2400 amps
b) 4800 amps
c) 12000 amps
d) 24000 amps
b) 4800 amps
In what way does surface roughness hinder the MPI test on a part?
a) hindrance of particle migration
b) reduction in contrast
c) distortion of the magnetic field
d) all of the above
d) all of the above
What do the following cleaning methods all have in common? Shot blasting, sand blasting, wire brushing and scraping
a) none are used for precleaning a part for MPI
b) none require electricity
c) all are mechanical methods
d) all are environmentally friendly
c) all are mechanical methods
Which cleaning method is not likely to be used to remove oil films prior to an MPI test?
a) vapour degreasing
b) wire brushing
c) steam cleaning
d) ultrasonic cleaning
b) wire brushing
The magnetic field produced by a yoke made of permanent magnets is _______ between the poles.
a) longitudinal
b) circular
c) both a and b
d) constantly varying
a) longitudinal
The swinging field MPI technique is used with
a) sequenced D.C.
b) combined D.C. and A.C. fields
c) combined A.C. fields
d) all of the above
d) all of the above
The advantage of the swinging field or multidirectional magnetization technique is
a) cost of equipment
b) detection of small defects
c) time saving because it is single step test
d) both b and c
d) both b and c
When permeability of a material is quoted without an additional qualifying term the permeability referred to is
a) initial permeability
b) incremental permeability
c) maximum permeability
d) osmotic permeability
c) maximum permeability
Current for circular magnetization of a part whose maximum permeability is 500 will be ___________ compared to a part with maximum permeability of 4000.
a) more
b) less
c) about the same
d) it depends if A.C. or D.C. is used
a) more
In MPI a handy rule of thumb relating current flow and suspected flaw orientation is; current flow should be directed _______ major axis.
a) under suspected defects’
b) parallel to suspected defects’
c) perpendicular to suspected defects’
d) diagonally to suspected defects
b) parallel to suspected defects’
The strength of a circular magnetic field is not diminished by ________ of a part.
a) permeability
b) diameter
c) length
d) any of the above
c) length
A 2cm diameter pipe and a 2cm diameter bar of the same steel alloy are each circularly magnetized by a 1000 amp D.C. head shot. The strongest magnetic field will occur on the surface of the __________-.
a) bar
b) pipe
c) pipe if its wall is less than 0.5cm
d) none of the above, fields will be equal
d) none of the above, fields will be equal
When a hollow non-magnetic central conductor is used to induce a circular magnetic field in a ferro-magnetic cylinder maximum field strength is at the
a) central conductor’s outside surface
b) central conductor’s inside surface
c) magnetic material’s inside surface
d) magnetic material’s outside surface
c) magnetic material’s inside surface
When A.C. is used instead of D.C. for a head shot on a steel tube, the field on the inside surface of the tube is
a) much less
b) much more
c) nearly the same
d) both are exactly zero
d) both are exactly zero
