MT lv.2 Flashcards by Ken Thompson

The primary difference between magnetic particle testing and other methods of testing using magnetics, such as electromagnetic resonance, electron paramagnetic resonance and eddy current testing is
a) intensity of field used
b) frequency of field oscillation
c) mono-pole versus bi-pole magnetics
d) none of the above

b) frequency of field oscillation

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Two long conductors (wires) are placed parallel and near to each other. When current flows in the same direction in both wires there will exist a
a) net repulsive force between the wires
b) net attractive force between the wires
c) neutral zone at the midpoint between the wires
d) zone of cold fusion at the core of the wires

b) net attractive force between the wires

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Two long conductors (wires) are placed parallel and near to each other. When current flows in opposite directions in both wires, there will exist a
a) net attractive force between the wires
b) net repulsive force between the wires
c) neutral zone at the mid point between the wires
d) slight increase in gravitons between the wires

b) net repulsive force between the wires

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Magnetic dipole moment is a
a) vector quantity
b) scalar quantity
c) nuclear phenomenon
d) small unit of time

a) vector quantity

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The magnitude of the magnetic dipole moment is directly proportional to
a) the amount of current in a coil conductor
b) the area of a coil conductor
c) both a and b
d) the ratio of current to coil area

c) both a and b

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The magnitude of a magnetic induction field at a perpendicular distance ‘r’ from the centre of a long straight conductor with a current ‘I’ amperes is
a) proportional to the current ‘I’
b) inversely proportional to the distance ‘r’
c) both a and b
d) none of the above

c) both a and b

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When a current is passed through a long circular conductor of radius R such as a wire the maximum magnetic induction field occurs at
a) the centre of the conductor
b) 0.707 R
c) R (ie. the conductor’s surface)
d) 1.414R

c) R (ie. the conductor’s surface)

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The most significant factor contributing to a material possessing magnetic properties is
a) the number of neutrons in the nucleus
b) unpaired electrons in the structure
c) the van Allen belts
d) whether ionic or covalent bonding is responsible for the crystal structure

b) unpaired electrons in the structure

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In normal unmagnetized condition, the domains of a ferromagnetic material are
a) randomly aligned
b) alternately aligned as on a checker board
c) non-existent until an external field is applied
d) found only at the curie point

a) randomly aligned

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In ferromagnetic materials the ratio of the magnetic induction field to the magnetic field intensity is called the
a) susceptibility
b) permeability
c) permissivity
d) magnetic impedance

b) permeability

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The internal magnetic intensity of a specimen brought into an external magnetizing field will always __________ the applied field.
a) be less than
b) equal
c) be greater than
d) reduce

a) be less than

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The slope of the virgin magnetization curve at the origin of a hysteresis plot is called the
a) original magnetization
b) flux density
c) permitivity
d) initial permeability

d) initial permeability

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When a ferromagnetic material is placed in an inducting field H, and H is increased until the incremental permeability is simply the free space permeability this point is called the
a) magnetic saturation
b) inflection point
c) reversal point
d) Barkhausen limit

a) magnetic saturation

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The small jumps in magnetism as a ferromagnetic material is exposed to an increasing induction field are termed
a) incremental permeability
b) Delta M’s
c) magnetic scatter
d) Barkhausen jumps

d) Barkhausen jumps

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A closed magnetic path through one or more materials is considered a magnetic circuit. As such, it can be considered analogous to an electric circuit, the magnetic equivalent to voltage is
a) reluctance
b) magnetostriction
c) magnetomotance
d) magneto-voltage

c) magnetomotance

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Magnetic circuits are equivalent to electric circuits hence have an equivalent equation to Ohm’s law, the term equivalent to electrical resistance in magnetics is
a) coercive force
b) reluctance
c) permeability
d) magnetic flux

b) reluctance

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In a magnetic circuit, which is equivalent to an electric circuit, the magnetic equivalent to electrical current is
a) magnetomotance
b) reluctance
c) permittivity
d) magnetic flux

d) magnetic flux

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The ability of the magnetic particle method to detect subsurface defects is not determined by
a) specimen size
b) defect depth
c) defect orientation
d) strength of applied field

a) specimen size

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Magnetic particle testing makes use of the phenomenon called
a) magnetostriction
b) magnetic-flux-leakage
c) magnetomotive force
d) piezoelectric effect

b) magnetic-flux-leakage

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Which stage of processing can magnetic particle testing be used?
a) Primary production and processing
b) secondary processing or manufacturing
c) in-service
d) all of the above

d) all of the above

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Which of the following should not be in the list?
a) ingot
b) bloom
c) billet
d) slab

a) ingot

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The collection of magnetic particles caught by a leakage field in a magnetic particle test indicates a discontinuity’s
a) location
b) shape
c) size and extent
d) all of the above

d) all of the above

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Very wide surface cracks may not produce a powder pattern because
a) the surface opening is too wide for the particles to bridge
b) detectability is based of the length to width ratio
c) wide cracks are always shallow
d) all of the above

a) the surface opening is too wide for the particles to bridge

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Magnetic particle testing would give best results when used on
a) cast gray iron
b) soft steel
c) hardened steel
d) stainless steel

b) soft steel

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Which of the following might be considered a disadvantage of magnetic particle testing? a) speed of operation b) relative expense c) need to demagnetize parts d) detection of shallow defects

c) need to demagnetize parts

Eddy current testing can also be used to detect surface and sub-surface defects on ferromagnetic materials but is usually inferior to magnetic particle testing because of a) inspection speed b) requirement of large saturating bias fields c) depth and size estimations d) both a and b

d) both a and b

The cause of a magnetic particle indication is always a a) defect b) surface blemish c) discontinuity d) surface breaking crack

c) discontinuity

The void that occurs at the top centre portion of an ingot is usually called a a) hole b) funnel c) shrink cavity d) sprue

c) shrink cavity

Segregation is a(n) _________ process discontinuity. a) inherent b) primary c) secondary d) service

a) inherent

Blowholes not welded shut in subsequent rolling processes can result in a) seams or laminations b) pipe c) segregation d) laps

a) seams or laminations

Seams in bar stock formed from under-filled rolls are usually a) acceptable MPI indications b) not detectable by MPI c) nearly normal to the surface of the bar being formed d) at an acute angle to the surface of the bar being formed

c) nearly normal to the surface of the bar being formed

Seams in barstock formed as a result of over filled rolls are usually a) acceptable MPI indications b) not detectable by MPI c) nearly normal to the surface of the bar d) at an acute angle to the surface of the bar

d) at an acute angle to the surface of the bar

Another name for the "unit pole" is a) mono-pole b) electromagnetic unit c) north seeking pole d) all of the above

b) electromagnetic unit

If a compass needle is brought near a bar magnet the needle will orient itself ______ to the magnetic lines of force at any point. a) parallel b) perpendicular c) toroidally d) transverse

a) parallel

The Weber is the MKS form of magnetic flux. The cgs unit is called the maxwell. 1 weber = ________ maxwells a) 10 b) 100 c) 10^6 d) 10^8

d) 10^8

The magnetic flux per unit area is called the a) flux density b) magnetic density c) magnetic concentration d) saturation factor

a) flux density

Soft iron if brought into the field of a magnet will be a) permanently magnetized b) temporarily magnetized c) electrified d) statically charged

b) temporarily magnetized

The Hall effect is used to a) demagnetize material b) increase the permeability of ferromagnetic materials c) measure magnetic fields d) induce eddy currents

c) measure magnetic fields

A Hall detector can be used to measure a) magnetic field strength b) coercive force in a hysteresis loop c) magnetic field direction d) both a and c

d) both a and c

The negative magnetizing force required to reduce the flux density in a part to zero after saturation is called a) residual force b) coercive force c) demagnetizing field strength d) null force

b) coercive force

The degree to which a material holds a residual magnetic field is termed a) saturation b) negative saturation c) reluctance d) retentivity

d) retentivity

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

b) reluctance

When an electric current, a magnetic field or an electrical potential drops off to zero, the reduction in amplitude of these quantities is given the same term. That term is a) decay b) spin off c) lapse d) lag

a) decay

Pulsating "DC" is considered the result of a) half wave rectified single phase AC b) full wave rectified single phase AC c) full wave rectified three phase AC d) both a and b are considered to pulsate

d) both a and b are considered to pulsate

Commercial single phase alternating current can best be described as a a) straight line of fixe bias b) sine wave c) square wave d) saw tooth wave

b) sine wave

Short duration currents resulting from sudden changes in electric or magnetic condition within a circuit are called a) Bremstrahlung b) Barkhausen noise c) noise spikes d) transient currents

d) transient currents

Which of the following does not belong in the list? a) EMF b) voltage c) reactance d) potential difference

c) reactance

The core material used in an electromagnet is a) any insulator b) heat resistant ceramic c) ferromagnetic d) copper

d) copper

In magnetic particle testing, solenoids are used for a) magnetizing parts b) demagnetizing parts c) to evaluate indications d) both a and b

d) both a and b

The wavelength of blacklight used in fluorescent magnetic particle testing is usually around a) 365nm b) 3650nm c) 285nm d) 2850nm

a) 365nm

A solenoid can be considered to consist of several a) resistors b) capacitors c) diodes d) loops

d) loops

When a current is passed directly through a part the magnetization that results is considered to be a) longitudinal b) circular c) a coil shot d) multi directional

b) circular

A shot of magnetizing current passed through a part while clamped between the clamping contacts of a stationary unit is referred to as a(n) a) induction shot b) coil shot c) central conductor shot d) head shot

d) head shot

A magnetic particle cluster resulting from a true leakage field but not originating from a metal flaw is a(n) a) anomaly b) false indication c) irrelevant indication d) non-relevant indication

d) non-relevant indication

Ohm's law can be expressed as a) E = (I) (R) b) I = (E) (R) c) R = (I) (E) d) E = I R

a) E = (I) (R)

In a D.C. series circuit what resistance is required to cause a voltage drop of 170 volts when 5 amps are flowing? a) 29.5 milli ohms b) 34 ohms c) 165 ohms d) 850 ohms

b) 34 ohms

What is the current through a 50 ohm resistor if the potential across the resistor is 12 volts? a) 240 mA b) 417 mA c) 24 A d) 600 A

a) 240 mA

Which of the following is the relationship for electric power? a) I R b) EI c) E /R d) all of the above

d) all of the above

"Conventional current flow" has electrons moving a) from negative to positive b) from positive to negative c) on the inside of wire conductors d) on the outside of wire conductors

b) from positive to negative

The left hand rule for determining magnetic field direction applies to a) AC circuits only b) DC circuits only c) modern current theory d) conventional current flow theory

c) modern current theory

The purpose of the iron core in an electromagnet is to a) eliminate eddy currents b) increase the magnetic flux density c) brace the coils against the magnetic torque d) provide an electrical ground route

b) increase the magnetic flux density

The lagging of flux density (B) behind the magnetizing force (H) is called a) phase lag b) phase shift c) doppler shift d) hysteresis

d) hysteresis

In a transformer, if the voltage in the secondary winding is stepped down, the current in the secondary will be a) stepped up b) stepped down c) remain the same as the primary d) D. C.

a) stepped up

If Is and Ip are currents, Es and Ep voltages and Ns and Np number to turns in the secondary and primary windings of a transformer, which is not true. a) Ep Ip = Es Is b) Ip/Is = Es/Ep c) Es/Ep = Np/Ns d) Ip/Is = Ns/np

c) Es/Ep = Np/Ns

Alternating current used as a magnetizing source tends to concentrate the magnetic flux near the test piece surface because of a) the inverse square law b) ohm's law c) the skin effect d) the Barkhausen effect

c) the skin effect

Which is not an advantage of using AC for a magnetizing current? a) increased contrast b) the skin effect c) increase mobility d) ease with which the part is demagnetized

a) increased contrast

Penetration of the magnetic field, all other factors being equal, is greatest for a) half wave rectified single phase AC b) full wave rectified single phase AC c) half wave rectified 3 phase AC d) full wave rectified 3 phase AC

a) half wave rectified single phase AC

Ease of demagnetization depends on a) amount of residual magnetism in the part b) if single or 3 phase rectified current was used for magnetization c) the coercive property of the material d) all of the above

c) the coercive property of the material

The temperature at which a ferromagnetic material changes to a paramagnetic material is the a) Neel temperature b) Curie point c) an ambient temperature d) plastic point

c) an ambient temperature

Upon cooling a ferrous alloy below its Curie point, in the absence of an external field it a) remains paramagnetic b) becomes ferromagnetic c) becomes ferromagnetic but unmagnetized d) emits UV light

c) becomes ferromagnetic but unmagnetized

Initial demagnetizing current using electromagnetic techniques should be a) equal to maximum magnetizing current b) slightly higher than maximum magnetizing current c) slightly lower than maximum magnetizing current d) slightly higher than minimum magnetizing current

b) slightly higher than maximum magnetizing current

Which is not a recommended demagnetization technique using an A.C. coil? a) place the part in the coil and gradually reduce the current to zero b) place the part in the coil and expand the coils to twice the diameter while current is on c) with the current on, draw the part through the coil and away to a distance of 2 coil diameters d) none of the above

b) place the part in the coil and expand the coils to twice the diameter while current is on

Why is A.C. not an effective means of demagnetizing large parts? a) because they don't fit into the coil b) due to transformer limitations on the current draw c) because of the skin effect d) because of low transformer efficiency

c) because of the skin effect

To eliminate the circular magnetism that exists in a part by applying a longitudinal field may require several "shots" if the part a) is soft steel b) is hardened steel c) has a large L/D ratio d) is not oriented north-south

c) has a large L/D ratio

Substances whose molecular structure is such that an unbalanced antiparallel electron spin exists are said to have ferrimagnetism. These substances are called a) ferrites b) ferros c) pharaohs d) faeries

a) ferrites

Aircraft, automotive and railroad components that have been inservice for some time but not near an artificially produced magnetic field are often found to be strongly magnetized. This is a result of a) friction between parts b) the earth's magnetic field c) geo-magnetic reversals d) the electric field off the spark plugs

b) the earth's magnetic field

The techniques used for demagnetization using D.C. are a) essentially the same as A.C. b) more effective than A.C. c) both a and b d) less costly than A.C.

c) both a and b

Yoke demagnetization can be more effective than coil methods in some cases because a) they go A.C.-D.C. b) they make contact with the part c) the yoke is always D.C. d) the field can be more concentrated

d) the field can be more concentrated

To detect residual circular magnetism in a circular part using a field meter you must a) hold the meter at 2 positions on the part at right angles to each other b) make a saw cut into the part c) use a circular field meter d) use 2 field meters

b) make a saw cut into the part

A ball bearing is to be tested by MPI. Which is the best option for magnetization? a) a coil shot b) 3 shots at mutual right angles using induced current c) parallel magnetism d) 2 coil shots and one head shot

b) 3 shots at mutual right angles using induced current

Which is not a problem that might result if the wrong choice of particles is made in MPI testing? a) misinterpretation due to distorted indications b) oversensitivity c) failure to form indications d) formation of indications too faint to detect

b) oversensitivity

The single most important property to consider in selection of magnetic particles is a) permeability b) shape c) size d) none of the above

d) none of the above

Magnetic particles used for wet MPI purposes are usually colour coated ___________. a) iron fillings b) cobalt 59 c) ferromagnetic oxides d) Alnico

c) ferromagnetic oxides

Clumping of wet magnetic particles on the test specimen is usually a result of a) the carrier being too viscous b) the test surface being too rough for the particles used c) too high a retentivity of the particles d) relevant indication formation

c) too high a retentivity of the particles

The size of most dry powder magnetic particles used in general flaw detection is a) less than 2 microns in any dimension b) about 3000 to 4000 microns c) a mixture of shapes and sizes d) not a consideration in the test method

c) a mixture of shapes and sizes

The typical size range of dry magnetic particles is a) 1 - 25 æm b) 25 - 100 æm c) 100 - 1000 æm d) 1000 - 5000æm

c) 100 - 1000 æm

The typical size range for wet magnetic particles is a) 1 -25 æm b) 25 -100 æm c) 100 -1000 æm d) 1000 -5000 æm

a) 1 -25 æm

The particle shape of dry magnetic particles that is best suited to detection of weak leakage fields from sub-surface defects is a) spherical b) elongated c) flake d) irregular

b) elongated

The shape of particles used in the wet magnetic particle method is a) elongated b) flake c) spherical d) not important

d) not important

Compared to visible magnetic particles, fluorescent magnetic particles are a) on average smaller b) magnetically less sensitive c) more dense d) magnetically more sensitive

b) magnetically less sensitive

Which is not a colour of magnetic particles that should be used on grit blasted surfaces? a) red b) white c) black d) orange

b) white

The advantage of the oil based magnetic particles as compared to the water based is a) cost of particles b) sensitivity c) the ability to use oil based in either oil or water d) none of the above

d) none of the above

A combination of the residual and continuous MPI methods are sometimes used if a) you are using dry powder b) the part is cylindrical c) the part has relatively high retentivity d) only a single shot is required

c) the part has relatively high retentivity

Wet magnetic particles can be applied by a) using a hose and nozzle to spray the part b) immersing the part in an agitated bath c) both a and b d) none of the above is recommended

c) both a and b

The condition reached in a ferromagnetic material subjected to an A.C. magnetic field such that the incremental permeability is one during part of each cycle is termed a) D.C. saturation b) A.C. saturation c) incremental saturation d) half wave peaking

b) A.C. saturation

What is the condition reached in a ferromagnetic material subjected to a D.C. magnetizing current when the incremental permeability is unity? a) D.C. saturation b) A.C. saturation c) incremental saturation d) magnetic limit

a) D.C. saturation

The portion of an electromagnetic circuit that is inside the coil (winding) is called the a) Helix b) core c) solenoid d) inductor

b) core

When a part is magnetized by a current flow of very brief duration it is said to be a) de-polarized b) zapped c) flash magnetized d) residually magnetized

c) flash magnetized

In full wave rectified A.C. the peak current is a) zero b) 2 times the r.m.s. value c) 2.2 times the r.m.s. value d) 0.707 times the r.m.s. value

b) 2 times the r.m.s. value

When an electric current is forced to flow across a gaseous gap the result is a) fluorescence b) an arc c) an induction field d) Barkhausen noise

b) an arc

Articulated pole pieces are usually found on these. a) yokes b) swinging fields c) Hall detectors d) Berthold penetrameters

a) yokes

The closed path followed by a magnetic flux line or group of flux lines is called a a) bar magnet b) magnetic circuit c) flux core d) magneto-loop

b) magnetic circuit

A device used to measure the strength of magnets or magnetic fields is a a) magnetometer b) penetrameter c) fluxometer d) field densitometer

a) magnetometer

The relative permeability of copper ;is a) 0 b) 1 c) >1 d) <1

d) <1

The relative permeability of a diamagnetic material is a) 0 b) 1 c) >1 d) <1

d) <1

The sensitivity of an MPI test is dependant upon a) magnitude of magnetizing current or field b) the type of test medium c) method of application of particles d) a combination of the above

d) a combination of the above

The type of magnetic particles used in an MPI test is determined by a) defect location, on or below surface b) size of defect c) convenience d) all of the above

d) all of the above

To detect the #3 hole (0.7" dia. 0.21" deep) in a Ketos ring using a central conductor, which would detect the hole using the least current? a) half wave A.C. b) D.C. surge c) straight D.C. d) A.C.

a) half wave A.C.

Sensitivity of the residual method of MPI testing when the test part is immersed a) increases with carrier density b) increases with carrier viscosity c) increases with time immersed d) decreases with particle size

c) increases with time immersed

The standard 1/2 second "shot" duration in the continuous wet method assumes a) correct particle concentration b) A.C. is used c) D.C. is used d) only head shots are required

a) correct particle concentration

The decision to use circular or longitudinal magnetization is determined by a) part shape b) suspected defect orientation and shape c) whether or not you have a coil d) both a and b

d) both a and b

When a tubular part is MPI tested using a head shot where the current is passed through the tube itself the field strength on the inside surface of the tube compared to the outside is a) the same b) zero c) about 1/4 d) 4 times greater

b) zero

Shafts, drums and girders can be _______ magnetized by coiling a flexible cable around the part and passing a current through the cable. a) longitudinally b) circularly c) randomly d) surface

a) longitudinally

As result of a head shot, the magnetic lines of force take the general form of a) a bar magnet b) a horseshoe magnet c) concentric rings about the part axis d) an ellipse

c) concentric rings about the part axis

Equations for ampere turns required for a coil shot are usually qualified by conditions. Which is not a condition usually stipulated? a) part permeability b) maximum part length c) effective coil length d) fill factor

b) maximum part length

When is the equation It = 45000 /(L/D) used? a) for coil shots on parts with an L/D ratio >4 b) for coil shots on parts with an L/D ratio <4 c) for coil shots on parts centred in the coil d) for central conductor shots

b) for coil shots on parts with an L/D ratio <4

Recommended D.C. current for a head shot is based on a part's diameter. Rule of thumb for a head shot is _______ amps / mm part diameter. a) 1 b) 25 c) 40 d) 100

c) 40

?equation? Given a solid steel shaft 1m long and 20 cm diameter, what is the current recommended for a 5 turn coil shot assuming the bar is not centred in the coil? a) 750 amperes b) 1000 amperes c) 1500 amperes d) 2000 amperes

b) 1000 amperes

Given a hollow steel shaft 1m long and 10cm diameter, what magnetizing current would you use with a 5 turn coil with the part at the bottom of the coil? a) 100 amperes b) 200 amperes c) 300 amperes d) 600 amperes

d) 600 amperes

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 it may be possible to damage parts exposed to magnetic particles or the liquid vehicle the inspector may have to a) use dry powder instead of wet method b) use insulated prods c) plug holes and mask surfaces d) use coil shots only

c) plug holes and mask surfaces

Vapour degreasing would not be an effective cleaning method for which material? a) oils b) mineral deposits c) waxes d) greases

b) mineral deposits

A problem with performing an MPI test on a part that does not have its thin layer of paint or plating removed is a) no subsurface defects can be located b) cracks cannot be seen c) the magnetic field disbonds the paint or plating d) all indications have the "fuzzy" subsurface appearance

d) all indications have the "fuzzy" subsurface appearance

A coil shot is not effective if the ratio of the long to short dimension is less than a) 1 b) 2 c) 4 d) 10

b) 2

The purpose of a swinging field set up for MPI testing is to a) reduce set up time b) reduce costs c) improve depth sensitivity d) increase detectability of randomly oriented defects

d) increase detectability of randomly oriented defects

When using 2 A.C. fields to provide a swinging field MPI test ________ to be effective. a) only single phase A.C. is used b) only 3 phase A.C. is used c) the 2 fields must be 50ø to 130ø out of phase d) the 2 fields must be in phase

c) the 2 fields must be 50ø to 130ø out of phase

In the swinging field method of MPI testing the application of the test medium (particles) is a) prior to the field application b) during the field application c) after the field is removed (residual) d) at any time during the test

b) during the field application

Calculations for coil currents for longitudinal magnetization of cylindrical parts assume the cross-sectional area of the coil is at least 10 times the part cross-section. What minimum radius would a coil need to be to test a rod 20cm diameter? a) 31.6cm b) 44.7cm c) 100cm d) 200cm

a) 31.6cm

Although it is possible to magnetize a material whose maximum permeability is 100, a limiting factor might be a) prod spacing needed b) current output of your equipment c) retenitivity of the particles used d) time required to form indications

b) current output of your equipment

A circularly magnetized bar 2 inches in diameter carrying 1000 amps will have a field strength _________ a bar of the same material having a diameter of 4 inches carrying 1000 amp current. a) the same as b) 1/4 that of c) 1/2 that of d) twice that of

d) twice that of

It may be possible to detect cracks on the inside surface of cylinders magnetized using a head shot. This is because a) cracks have depth b) the magnetic field does not reach zero the cylinder radius is zero c) both a and b d) none of the above

a) cracks have depth

When a central conductor is used to induce a circular field in a cylinder, maximum field on the cylinder is had on the cylinder inside surface when the central conductor is a) hollow and non-magnetic b) solid and non-magnetic c) solid and magnetic d) none of the above, central conductor material is not the controlling factor

d) none of the above, central conductor material is not the controlling factor

For very large parts where even stationary MPI units could not supply sufficient current for head or coil shots, it may be possible to secure higher strength fields by means of a) prods or yokes b) swinging field techniques c) transformer amplifiers d) connecting a welding machine in series to the bench unit

a) prods or yokes

In MPI testing of irregular shaped objects using D.C. head shots, field strength is a) uniform at all surfaces b) greater at small diameters or sections c) greater at large diameters or sections d) too convoluted to measure

b) greater at small diameters or sections

Current distribution in a part MPI tested using prods depends on a) prod spacing b) part shape and dimensions c) resistivity of the part d) all of the above

d) all of the above

When you move half the prod spacing from the midpoint of the prod centre-line the field is a) maximum b) minimum c) much less than on the centre-line d) equal to the field on the centre-line

c) much less than on the centre-line

Maximum practical prod spacing is about a) 2 inches 5cm b) 4 inches 10cm c) 8 inches 20 cm d) 10 inches 25 cm

c) 8 inches 20 cm

Another term for the capacitive discharge method of producing magnetizing current is a) rod shot b) A.C. - D.C. pulse c) excitation shot d) surge method

a) rod shot

Prolonged agitation of wet fluorescent magnetic particles in large stationary bench units will result in a) increased retentivity due to work hardening b) reduced sensitivity due to abrading of fluorescent coating c) alteration of re-emitted light frequency d) no changes in any quality of the material

b) reduced sensitivity due to abrading of fluorescent coating

The two main components of a magnetic field indicator are a) a movable magnet and a fixed magnet b) a coil and a moving core c) a non-magnetic needle indicator and a bar magnet d) two coils wound opposite each other

a) a movable magnet and a fixed magnet

The sensing magnet in a magnetic field indicator brought next to a part with an associated external magnetic field will try to rotate ______ to the resultant vector of the two fields. a) clockwise b) counter-clockwise c) parallel d) perpendicular

c) parallel

The pointer, attached to the sensing magnet in a magnetic field indicator points _______ to the field resulting from the interaction of the sensing magnet and the magnetic field of the part tested. a) clockwise b) counter clockwise c) parallel d) perpendicular

d) perpendicular

Accurate calibration of a magnetic field indicator is provided by a) averaging readings from several specimens b) a Helmholtz coil's uniform field c) a shunt meter d) an electro-scope

b) a Helmholtz coil's uniform field

Using a Ketos ring and holding all test parameters constant except for fluorescent particle concentration; hole detectability _________ with increasing particle concentration a) increases constantly b) decreases constantly c) decreases to a minimum then increases d) increases to a maximum then decreases

d) increases to a maximum then decreases

Variation in Ketos ring's permeability can be changed by a) annealing b) using A.C. instead of D.C. techniques c) using D.C. instead of A.C. techniques d) no means as a Ketos ring is a Standard

a) annealing

Magnetic particle inspection quantitative quality indicators can be used for a) establishing wet particle concentrations b) detecting circular magnetism c) determining blacklight intensity d) determining particle size

b) detecting circular magnetism

A Gauss-meter is a device used in conjunction with a ___________ to determine field strength. a) Hall-effect probe b) permanent magnet c) FM antenna d) van der Graff generator

a) Hall-effect probe

A part that has been demagnetized using an A.C. demagnetization coil may be found to contain significant magnetization after being dropped or hammered. This is due to a) work hardening b) the Neel effect c) subsurface domains re-magnetize the outer domains d) the skin effect

c) subsurface domains re-magnetize the outer domains

As magnetizing current is increased in the low to medium current range, magnetic particle indications width a) increases linearly b) remains constant c) initially saturates with the first current surge then decreases d) bears no relation to current

a) increases linearly

A vigorous or cascading application of magnetic particle bath can a) drive indications into surface breaking seams b) wash indications from the location where they were first formed c) aid in particle suspension d) peen seams shut

b) wash indications from the location where they were first formed

To avoid an MPI bath washing an indication away when the current is removed you can a) keep the current on longer to allow bath to drain b) use compressed air to remove excess bath while current is still on c) both a and b d) tap the piece with a plastic mallet while current is on

c) both a and b

Many daylight magnetic particles have fluorescence. The advantage of this is a) visibility can be enhanced using a blacklight in the daylight b) filtering can be used with optical scanners to enhance indications over background c) higher retentivity of particles makes indications bigger d) both a and b

d) both a and b

If very fine particles are used in an MPI test where a large crack occurs they could fill the opening. The bridging that results will a) short circuit the flux leakage lines causing them to remain within the part b) increase the indication width c) increase the indication height above the surface of the test piece d) both b and c

a) short circuit the flux leakage lines causing them to remain within the part

Apart from being annoying, lens fluorescence causes a) filter breakdown b) reduced contrast c) tintinnabulation d) no effect

b) reduced contrast

As it relates to the amplitude of the induced magnetic field, the _______ current value is most significant. a) peak b) RMS c) average d) pre-rectified

a) peak

What is the only acceptable means of determining if magnetization is adequate when the residual method is used? a) gauss/tesla meter b) a test piece (test standard) c) formulae d) all of the above are valid methods

b) a test piece (test standard)

When sufficient magnetization is applied to a piece such that magnetic particles stick to minor surface field leakages not associated with discontinuities the part is said to be a) over magnetized b) in its magneto-strictive mode c) magneto-reluctant d) acceptable

a) over magnetized

A means of overcoming the problem of excessive or over magnetization is a) using longitudinal magnetization b) localizing the magnetizing fields at the surface using A.C. c) hitting the part with a soft faced hammer after magnetizing current is passed through it d) the swinging field technique

b) localizing the magnetizing fields at the surface using A.C.

The magnetic field properties that most affect flux leakage are a) field strength, permeability and angle to defect b) field strength, angle to defect, source (A.C., D.C. permanent magnet c) field strength, transformer efficiency, type (longitudinal or circular) d) permeability, flux leakage curvature, source (A.C. D.C. etc.)

a) field strength, permeability and angle to defect

The magnitude of the voltage induced between the ends of a wire moving through a magnetic field is a) inversely proportional to wire length b) directly proportional to velocity of the wire crossing the flux lines c) inversely proportional to the velocity of the wire crossing the flux lines d) independeant of wire velocity

b) directly proportional to velocity of the wire crossing the flux lines

A simple coil used as a flux sensitive device, when oriented parallel to the surface and positioned statically over the flux leakage field of a crack, will have a) a maximum positive voltage induced b) a maximum negative voltage induced c) 0.707 peak voltage (positive or negative depending on wiring) d) zero voltage

d) zero voltage

Conductive metals do not make good Hall sensors because their a) Hall coefficients are too low b) Hall coefficients are too high c) specific gravity is to high d) inductive impedance is too low

a) Hall coefficients are too low

The frequency of the voltage applied to the crystal in most Hall detectors used in flux sensitive devices is in the ________ range. a) D.C. b) 50 -60 Hz c) kilohertz d) megahertz

c) kilohertz

In a magnetodiode flux sensor, the property that changes with magnetic field intensity is a) resistance b) ductility c) density d) permeability

a) resistance

The purpose of arranging a Hall detector at the mouth or apex of a ferrite ring (ferrite C-core) is to a) eliminate lift off b) provide a magnetic shield c) concentrate flux leakage for better sensitivity d) induce eddy currents that counter the Hall currents

c) concentrate flux leakage for better sensitivity

The difference between ferroprobes and flux gate magnetometers is a) ferroprobes are activated at high frequency b) the number of coils used c) the use of ferrites d) none, they are the same flux detection device but with different names

a) ferroprobes are activated at high frequency

Application of a light lacquer or penetrant developer can be used in dry powder MPI tests to enhance contrast but the disadvantage is a) the powder cannot be reused after being in contact with the contrasting coating b) the coating process can be a time consuming extra step c) the removal of the coating, if needed, can be a time consuming extra step d) both b and c

d) both b and c

The disadvantage of reusing dry powder magnetic particles is a) reduced colour b) reduced contrast c) increased proportion of larger particles d) all of the above

d) all of the above

Dry powders cannot be used in water suspensions for the wet method of MPI because a) they quickly oxidize b) their settling rate is too high c) clumping results d) both a and b

d) both a and b

Light intensity requirements for daylight fluorescent dry magnetic particles are a) the same as for non-fluorescent powder b) the same as for wet fluorescent particles c) not specified in present standards or specifications d) equivalent to that found at the equator on a clear summer evening 1/2 before sunset

c) not specified in present standards or specifications

The problem you would likely encounter if you tried to view daylight fluorescent dry powder in similar conditions used for wet fluorescent MPI (UV light in a darkened area) is a) no fluorescent response is had use a UV lamp b) excessive background fluorescence c) retina damage due to the frequency of light emitted d) no problem at all

b) excessive background fluorescence

Fe3O4 (subscript numbers) is the chemical formula for which iron oxide? a) black b) brown c) red d) all of the above have the same formula

a) black

True material magnetic permeability is not important in magnetic particles until a) A.C. magnetizing currents are used b) D.C. magnetizing currents are used c) the L/D ratio of the joined particles exceeds 1 d) subsurface defects are required to be detected

c) the L/D ratio of the joined particles exceeds 1

If a settling test is performed on fluorescent wet particles, and after allowing the sample to sit unagitated over night (10-15 hours) a thin, brightly fluorescent layer forms on top of the sediment, a) the test is acceptable b) particle breakdown is indicated c) oil carrier breakdown is near d) more dispersing is required

b) particle breakdown is indicated

Higher flash point oil based liquids are preferred for the carriers in wet MPI testing because of a) fire hazard considerations b) operator breathing discomfort considerations c) background fluorescence considerations d) both a and b

d) both a and b

What is it about fluorescent magnetic particles that requires conditioning agents be added to the water used as their carrier? a) they induce rusting action b) their pigments and binders are water repellent c) they are soluble in straight water d) they would sink too quickly without the conditioner

b) their pigments and binders are water repellent

Small amounts of sodium nitrate or sodium chromate in the water based MPI bath are used to a) kill background fluorescence b) reduce foaming that results from agitation of baths c) protect pieces against rusting d) permit MPI on austenitic stainless steels

c) protect pieces against rusting

Addition of a small quantity of mineral oil to an oil based MPI bath is occasionally used to provide rust protection. The risk, however, is that a) viscosity will drop below required limits b) viscosity will rise above required limits c) particle concentration drops excessively d) fluorescent particle breakdown will occur

b) viscosity will rise above required limits

What can oil vehicles used for MPI baths be contaminated with that water vehicles cannot? a) fluorescent pigments and resins b) rust particles c) grease d) water

d) water

A marked increase in background blue fluorescence of the oil vehicle of an MPI bath as compared to the reference sample indicates a) probable oil contamination of bath b) probable water contamination of bath c) fluorescent particle breakdown d) the blacklight is about to fail

a) probable oil contamination of bath

Particle coagulation in an MPI bath can result from a) water contaminants in an oil bath b) oil contaminants in a water bath c) both a and b d) none of the above

c) both a and b

In order that indication to background contrast be maintained so as to ensure consistency of defect detection in an MPI test what is required? a) ensure only visible particles are used (not fluorescent) b) only water as a vehicle should be used c) maintain particle concentration in the bath d) ensure blacklight filter is clean

c) maintain particle concentration in the bath

When using magnetic particle concentrations at the lower limit of the recommended range in a recirculating system, you will a) reduce background b) require frequent concentration checks c) steadily decrease the particle concentration d) all of the above

d) all of the above

Setting speed of an MPI bath sample is accelerated by a) vibration b) magnetized particles c) warming the bath (to 40øC.) d) all of the above

b) magnetized particles

Settling of magnetic particles in the centrifuge tube can be retarded by a) particles getting in each others way b) upward flow of displaced liquid c) both a and b d) no known force or mechanism

c) both a and b

The upper limit for part temperature when using MPI in an oil vehicle is a) 30øC. b) 50øC. c) dependant on fire hazard based on flash point d) primarily a health consideration

d) primarily a health consideration

The quantity measured in blacklight intensity has units of æW/cm . The quantity is a) luminescence b) radiation c) irradiance d) illuminance

c) irradiance

The quantity measured in white light viewing has units of lux. The quantity is a) luminescence b) radiation c) irradiance d) illuminance

d) illuminance

If the eye has no sensitivity to the power irradiated (eg. UV light) photometric units quantifying that light are a) meaningless b) the same as radiometric values c) 1 d) 0

a) meaningless

In the retina the cells responsible for collecting light to visualize images are the a) epithelial cells b) epitonic cells c) neural cells d) cone and rod shaped cells

d) cone and rod shaped cells

An eye that has become accustomed to low light levels is said to exhibit __________ response. a) scotopic b) photopic c) myopic d) mesopic

a) scotopic

An eye that has adapted to bright daylight is said to be exhibiting ________ response. a) scotopic b) photopic c) myopic d) mesopic

b) photopic

The reason you can sometimes detect faint objects in the dark by not looking directly at them is because a) their is a high concentration of cone cells near the fovea b) rod cells are concentrated off axis in the retina c) of Lenz's law d) both a and b

d) both a and b

The electronic equivalent to the MPI term contrast would be a) rise time b) signal-to-noise ratio c) bandwidth d) modulation

b) signal-to-noise ratio

Detection of MPI indications is accomplished by a) the human eye b) imaging detectors c) non-imaging detectors d) all of the above

d) all of the above

At very low light levels (<0.03 cd/m ) colour differentiation is best for a) blue and green b) green and yellow c) blue and red d) none of the above

d) none of the above

The component in wet fluorescent MPI testing that is most likely to cause dermatitis is a) fluorescent dyes b) solvent based carrier c) dissolved salts in the tap water d) ferromagnetic particles

b) solvent based carrier

The mercury vapour arc was selected as a blacklight source because its spectrum a) gives a pure 365nm line with no other interfering energies b) has a smooth rise and fall like the continuous x-ray spectrum but having a peak at 365nm c) has several peaks, one of which is at 365nm d) has no harmful UV emission

c) has several peaks, one of which is at 365nm

Which vision requirement is a critical prerequisite for fluorescent MPI viewing? a) near vision b) far vision c) colour vision d) television

a) near vision

Non-imaging scanners used for indication detection in visible MPI testing systems detect a) magnetic flux variations b) a decrease in reflected light c) an increase in reflected or emitted light d) magneto-luminescence

b) a decrease in reflected light

MT lv.2 Flashcards

(200 cards)