Mag Particle Practice Flashcards
An electric current through a wire creates what
It creates a magnetic field around the wire
Since the magnetic lines of force within a bar magnet run the length of the bar, it is said to be
Longitudinally magnetized
Materials which are repelled magnetically are called
Diamagnetic
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 that exit are called
Flux leakage
The pattern of iron powder sprinkled on a paper placed over a bar magnet is called
Magnetograph
A hysteresis loop is used to demonstrate a materials
Stress-strain relationship, magnetic properties
The relative magnetic permeability is dependent on
The specific properties of the material tested. The strength of the applied field
Multiple (more than two) poles existing along the length of a bar magnet are known as
Consequent
The property of a magnetic material to keep or retain a magnetic field after the magnetizing current is removed is called
Retentivity
Magnetic particle testing can be effectively used on which material
Ferromagnetic materials
Magnetic lines of force (Magnetic flux) will…..
Never cross each other
A continuous circular (ring shaped) test object without a leakage magnetic field will have _____ north and south poles
No detectable
The reverse magnetizing force required to remove remnant or residual magnetism and therefore demagnetize the part is called
Coercive force
These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed is a
Paramagnetic material
A narrow hysteresis loop consists of what properties
High permeability, low retentivity, low coercive force, lower reluctance, lower residual magnetism
Rectified alternating current is sometimes referred to as _____ in magnetic particle testing
Half-or full-wave current
Alternating current is the preferred current for detecting ______ discontinuities
Surface
What rule best describes current flow (+ to -) when lines of magnetic force surround a conductor
Right hand rule
The areas on a magnetized part from which the magnetic field is leaving or entering into a part is called
Magnetic poles
A coil shot Is not as effective if the ratio of the long to short dimension is less than
2
When testing for fine shallow surface cracks, the preferred magnetic particle testing method should be
Wet AC
an electric current which flows steadily in one direction is a
Direct current
If 25 mm and 50 mm diameter bars were magnetized by passing the same current through them, the magnetic field would be
Stronger in the 25 mm diameter bar
Calibration of a yoke includes
Lifting a specified weight
Current values when using the headshot on a Mt bench unit are determined by
Determined by diameter of the part
Residual magnetism may be beneficial as an aid
In the interpretation and evaluation of indications
What kind of shot will produce a direct induction circular field in a test part
Head shot
A longitudinal field is generated in a test object by placing it in a coil, or by ____ cables (3 to 7 turns) around a test object
Wrapping
Penetration of the magnetic field, all other factors being equal, is greatest for
Half wave rectified single phase AC
Magnetic flux lines which are parallel to a discontinuity will produce a
No indication
A current passed through a magnetic central conductor will produce a magnetic field that is ____ a non-magnetic central conductor for the same size and current applied to the bar
Equal to
The small jumps in magnetism as a ferromagnetic material is exposed to an increased induction field are termed
Barkhausen effect (looks like stairs)
The unit used to denote flux density (symbol B) is the:
Gauss
The magnetizing force is applied and maintained while the magnetic particles are dusted or flowed onto the surface of the component is considered a
Continuous method
A yoke creates a _____ magnetic field
Longitudinal
The left hand rule for determining magnetic field direction applies to
Modern current theory (- to +)
The fact that only some magnetic domains resume a random orientation when the magnetizing field is removed accounts for what
Retentivity
The build-up of magnetic particle due to excessive magnization of the part under test us called
Furring
What direction of magnetic field is produced when passing a current directly through a test part
Circular
The magnetic field created by a head shot or central conductor is _____ for the entire length of the test object
Uniform
What type of equipment is similar to a temporary horseshoe magnet
Yoke
Magnetic particles should have which of the following properties?
Low retentivity/ high permeability
A magnetic flux leakage field can be caused by magnetic lines of force leaving or entering a test object where their path is _____ by a discontinuity
Distorted
A central conductor will produce a circular field with_____ danger of burning or ruining the test object
Minimal
The purpose of lead contact covers on prods for mpi testing is to
Reduce arc burns
The settling test should be performed once for new mixtures of solution and
Before each use
Ultraviolet radiation intensity used for testing must be a minimum of _____
1000 uW/cm squared
Too much current will produce ______ indication or______ background
Non relevant or excessive
The end of the magnet at which the line of force are thought of entering the magnet is the
South pole
Magnetic line of force can be described as
Having the same strength, seek the path of less resistance, decrease in density with increasing distance from poles (all of the above)
A material is considered demagnetized when
It’s residual magnetism field measures less then 3 gauss
Defects found between prods are aligned _____ the line between the prods:
Parallel to
The width of a magnetic particle indication is what size in relation to the actual flaw
Is always wider than the actual flaw opening
The property of a material that describes the ease with which a magnetic flux is established In a component is called
Permeability
The particle shape of dry magnetic particles that is best suited to detection of weak leakage field from subsurface defects is
Elongated
Electric current periodically reversing in polarity or direction is
Alternating current
In a ferromagnetic material, a region where all the “atomic moments” are aligned parallel to each other is called a
Domain
In order to be detectable by magnetic particle testing, a flaw must
Produce a leakage field at the surface
The point at which the magnetism in a material cannot be increased aven though the magnetizing force continues to increase
Saturation point
The flux density of the magnetism induced by a coil can be controlled by varying
The coil size, the current in the coil, the number of turns in a coil (all of the above)
The negative magnetizing force required to reduce the residual flux density in a part to zero after saturation is called
Coercive force
Where is the most logical place, on a casting, to look for discontinuities
At junction between light and heavy sections
The strength of a circular magnetic field is not diminished by ____ of a part
Length
When the central conductor mpi method is used to inspect a ring shaped object, or short cylinder
Both inside and outside surface and subsurface flaws can be found if the wall thickness is not too great
When welds are required to have only partial penetration used of HWDC yokes often give rise to non relevant indications. This problem can be eliminated by
Using an AC yoke
If a discontinuity is shallow and broad like a scratch, the flux lines my stream-line below the discontinuity. This will result in
A lack of indication
The magnetic field is strongest when
The magnetizing current is flowing
The proper number of amere-turns for a given test specimen being examined by longitudinal magnetism is determined by
It’s length and diameter
A circular field may be induced into a specimen by
Passing current directly through the part
Aircraft, automotive, and railroad components that have been in-service for some time but not near an artificially produced magnetic field are often found to be strongly magnetized. This is a result of
The earth’s magnetic field
A magnetic particle cluster resulting from a true leakage field but not originating from a metal flaw is a
Non-relevant indication
An eye that has adapted to bright daylight is said to be exhibiting
Photopic
Which magnetic particle application technique is the most sensitive
Continuous
Fluorescent magnetic particle indications should be inspected under
An ultraviolet light
The direction of magnetic lines of force are _____ degrees from the direction of current flow
90°
Demagnetization may be accomplished by ____
Heating a material above its curie point
What are 4 methods used with direct induction
Head shot, prods, clamps, magnetic leaches
What are four methods used with indirect induction
Central conductor bar, permanent magnets, ac yoke, coil/solenoid
What is the approximate permeability value for the following diamagnetic, paramagnetic, ferromagnetic
Diamagnetic is less than 1
Paramagnetic is slightly greater than 1
Ferromagnetic is much greater than 1
Its usually preferable to disassemble parts before magnetic particle inspection. True or false
True
Over inspection is not a serious problem in magnetic particle inspection. True/ false
False
Defects in brass parts can be detected with wet fluorescent magnetic particle. True or false
False
What is the most effective way of demagnetization
Heat above curie temp
What is the common unit used to measure wavelength
Nm
List two reasons why the filter should always be in place on a mercury vapor-arc lamp
Removes the short wave ultraviolet light
Removes most of the white light that the lamp produces
All parts with indications should be scrapped. True or false
False
Black powder gives a better visual contrast on dark heat treated scaly parts. True or false
False
A circular field is easily measured with a field meter. True or false
False
When magnetizing a Weld in two directions if the amperage used in the first direction is 750 A and the amperage in the second direction is 400 A. Then the section or part should be demagnetized between operations. True or false
True
Heating to 800°C will cause ferromagnetic material to become magnetic. True or false
False
What is the minimum eye adaptation time required to perform fluorescent magnetic particle examination
5 min in dark room before start of inspection
A pear shaped centrifuge (wet bench) used for fluorescent particle has what size of stem and division
1 ml stem and 0.05 division
Prods should not be used on what type of components or surface
Aerospace components or machined surface
When performing a coil shot with a low fill factor the L/D ratio should be
Between 3-15
List the recommended verification intervals for UV-A, water break test, ammeter check, gaussmeter
UV-A-daily,
water break test-daily,
Ammeter check-6 month, Gaussmeter-6 month
Permanent recording of magnetic particle indication may be done by
Written description, transparent tape, strippable film, photography
When using fluorescent particle, personnel shall not wear what type of eye glasses
Photochromic or that permanently darkened lenses
After demagnetization a calibration field indicator shall not detect magnetic flux fields with an absolute value above
Above 3 G (3x10(to the power of-4) T)
The unit usually used to denote flux density is
Tesla
Magnetic lines of force are most dense at
The poles of the magnet
The proper number of ampere-turns for a given test specimen being examined by longitudinal magnetism is determined by
It’s length and diameter
A circular field may be induced into a specimen by
Passing current directly through the part
An electric yoke produces what kind of field
A longitudinal field
Proper term for calculating magnetic force is called
Amper turns
Magnetic lines of force form a_____
Closed loop
The amount of amperage used for magnetic particle inspection using the prod technique is determined from the
Distance between the prods and thickness of the material
A metal that is difficult to magnetize is said to have
Low permeability
Subsurface discontinuity indications usually appear
Wide and fuzzy
What technique of applying particle provides greater sensitivity in locating subsurface WELD discontinuity
Continuous
When a ferromagnetic object is placed inside a coil carrying an electric current the magnetic lines of flux concentrate themselves in what direction
A longitudinal direction
What are three causes of nonrelevant indication
Sharp corners, heat affected zones, drill hole near surface
Using the residual testing technique, a number of parts are magnetized and laid on a rack prior to application of magnetic particle. Why is it Important that they do not rub or touch each other
It may cause magnetic writing
The strongest magnetic field in a coil is at the_____
Inside edge
Which of the following is most often used for dry magnetic particle inspection
Half wave direct current
In circular magnetization, the magnetic force is expressed in amperes. What term is used to express magnetizing force in longitudinal magnetization?
Amper-turns
