magnetic particle Flashcards
alternating current
electric current periodically reversing in direction
continuous method
the magnetic particle inspection method in which particles in either wet or dry form are applied to the surface of the part at the same time the part is being magnetized
fatigue cracks
progressive cracks that develop in the surface caused by the repeated loading and unloading of the part
defect
a fault in any material or part detrimental to its serviceability. all cracks, seams, laps, etc are not necessary defects as they may not affect the serviceability of the part in which they exist.
direct current
an electric current that flows in one direction
discontinuity
as used in connection with magnetic particle inspection, anything that causes an interruption in the magnetic path. a crack, slag inclusion, gas pocket, etc
evaluation
the determination of the significance of discontinuities from the standpoint of whether they are detrimental defects or inconsequential blemishes.
fatigue
the phenomenon of the progressive fracture of a metal by means of a crack, which spreads under repeated cycles of stress.
ferromagnetic
materials that are strongly attracted by a magnetic field.
circular field
a magnetic field which surrounds a nonmagnetic conductor of electricity or which exists and is completely contained within and also surrounds a magnetic conductor of uniform cross-section. generally applied to the magnetic field within and surrounding any magnetic conductor or part resulting from a current passed through it from one end to the other.
longitudinal field
a field which extends within a part from one or more poles to another or other poles and which is completely through a path external to the part
residual field
the field that remains in a piece of magnetizable material after the magnetizing force has been removed
fluorescence
the property of certain materials of emitting visible light during their subjection to black light
inclusions
impurity particles, usually oxides, sulfides or silicates. generally dispersed at random through the metal
interpretation
the determination of the cause of a magnetic particle indication
laminations
discontinuities in a plate sheet or strip caused by pipe, inclusions, or blowholes from the original ingot usually flat and parallel to the outside surface
lines of force
imaginary lines used to visualized the direction of the force in an external magnetic field. see flux lines
magnetic particle inspection
a nondestructive inspection method for locating discontinuities in ferromagnetic materials through the location of leakage magnetic fields by their attraction for finely divided, ferromagnetic particles.
magnetic writing
a form of non-relative indication some times caused when the surface of a magnetized part comes in contact with another piece of ferromagnetic material
non-relevant indication
a magnetic particle indication due to a leakage magnetic field which is not caused by an actual discontinuity in the magnetized material, but by some other condition which does not affect the usefulness of the part.
permeability
the ability of material to become magnetized. it is the relation between the field strength and the magnetizing force
reluctance
the degree of difficulty with which the magnetic flux is produced. materials of high permeability have low reluctance.
retentivity
the ability of a material to retain a portion of the magnetic field set up in it after the magnetizing force has been removed.
saturation
the point in the magnetization of magnetizable object at which an increase in the magnetizing force produces no increase in the magnetic field within the part
suspension
the correct term applied to the light oil bath in which, is suspended the ferromagnetic particles used in the wet method.
