- A casting defect, detectable at magnifications not exceeding ten diameters,
consisting of voids in the form of stringers shorter than shrinkage cracks.
This defect results from contraction during solidification where there is
not an adequate opportunity to supply filler material to compensate for the
shrinkage. It is usually associated with abrupt changes in section size.
- The structure of metals as revealed by examination of the etched surface
of a polished specimen at a magnification not exceeding ten diameters.
- Magnet -
Any piece of iron, steel or magnetite that has the property of attracting
iron or steel.
Behavior - When two materials attract or repel each
- This refers
to a break in the magnetic uniformity of the part-a sudden change in permeability.
A magnetic discontinuity may not be related to any actual physical break in
the metal, but it may produce a magnetic particle indication.
Domain - A region in which the magnetic fields of
atoms are grouped together and aligned.
Field - The space in which a magnetic force is exerted. This space exists
within and around a magnetized material and a conductor carrying electrical
- The measured intensity of a magnetic field at a specific point. Usually
expressed in amperes/meter or oersteds.
Force - See Magnetic field strength.
Flux - A measure of quantity of magnetism, taking
account of the strength and the extent of a magnetic field. The total number
or lines of force existing in a magnetic circuit.
Flux Density (B) - The normal magnetic flux per unit
area. Usual expressed in Tesla or Gauss.
Lines of Force - Imaginary lines in the magnetic
field indicating how strong the magnetic force is (the closer together the
lines, the stronger the force).
Loop - If a conductor carrying an electric current is bent in a loop,
the magnetic lines of force enter on one side of space within the loop is
found to contain a magnetic field which has very definite directional properties.
Polarity is created within the coil with one end being a north pole and the
opposite end a south pole. The space enclosed by the loops is longitudinally
Materials - Materials are affected by magnetism in two general ways.
Some of them are attracted by a magnet, while others exert a repellent force.
The first is called "paramagnetic" and the later "diamagnetic."
In Magnetic particle inspection we are not ordinarily concerned with either
of the two classes, but with what may be termed a subdivision of the first
class called "ferromagnetic materials."
Moment - The ratio between the maximum torque exerted
on a magnet, current-carrying coil or moving charge situated in a magnetic
field and the strength of that field.)
Particle Inspection - A method of detecting cracks
or defects by establishing a magnetic field in the object and using iron filings
to see if the field lines are constant.
Particle Testing - (see Magnetic Particle
Permeability - The ratio of the magnetic flux density,
B, in a substance to the external field strength.
Poles - Any place that a magnetic line of force
exits or enters the magnet is called a pole.
Testing (MT) - A nondestructive testing method used
for defect detection.
Hard Alloy - A ferromagnetic alloy capable of being magnetized permanently
because of its ability to retain induced magnetization and magnetic poles
after removal of externally applied fields; an alloy with high coercive force.
The name is based on the face that the quality of the early permanent magnets
was related to their hardness.
Soft Alloy - A ferromagnetic alloy that becomes magnetized readily
upon application of a field and that returns to practically a nonmagnetic
condition when the field is removed; an alloy with the properties of high
magnetic permeability, low coercive force and low magnetic hysteresis loss.
- The force of attraction or repulsion in a material.
- The property and the extent of being magnetized. Quantitatively, the magnetic
moment per unit volume of a substance.
Force - The total force tending to set up a magnetic flux in a magnetic
circuit. It is usually designated by the letter "H"and the unit
is the "Oersted."
- A picture of a magnetic field made by the use of iron powder under conditions
that allow it to arrange itself into the pattern of the field.
- Deformation of a ferromagnetic material (such
as iron and steel) subjected to a magnetic field.
- See initial pulse.
- The characteristic of metals which permits plastic deformation in compression
- In immersion testing, a device for angular orientation of the transducer.
- Marie &
Pierre Curies - Discovered two radioactive
elements in pitchblende (polonium and radium). They were later awarded the
- A series of indications on the horizontal trace of the cathode ray tube
to show increments of time or distance.
- The very hard structure in certain irons and steels that is usually formed
by quenching (rapid cooling) from an elevated temperature. Martensite may
or may not be tempered to reduce hardness and increase ductility and toughness.
- Mass Numbers
- The number of protons and neutrons in a atoms.
Noise - Random signals caused by the material structure of the test
object. A component of background noise.
- The principal phase of a metal in which another constituent is embedded.
For example, in gray cast iron, the metal is the matrix in which that graphite
flakes are embedded.
- Matter -
Anything that has mass and occupies space.
Permissible Dose (MPD) - That dose of ionizing radiation which competent
authorities have established as the maximum that can be absorbed without undue
risk to human health.
Free Path - Average distance a particle travels between collisions.
Life - The average time during which an atom or other system exists
in a particular form.
Attenuation - Measuring the ultrasonic absorption
and the scattering of a material.
– The properties of a material that reveal its elastic and inelastic
(plastic) behavior when force is applied, thereby indicating its suitability
for mechanical (load-bearing) application, fatigue limit, hardness, modulus
of elasticity, tensile strength, and yield strength.
(megahertz) - One million Hertz per second.
Processes - The chemical and physical processes
continuously going on in living organisms and cells.
- An opaque, lustrous elemental chemical substance that is a good conductor
of heat and electricity and, when polished, a good reflector of light. Most
elemental metals are malleable and ductile and are, in general, heavier than
the other elemental substances.
- Pertaining to examination of a metallic surface with the aid of a microscope.
The surface is usually polished to make it flat, and may be etched with various
chemicals to reveal the microstructure.
- the science dealing with the constitution and structure of metals and alloys
as revealed by the unaided eye or by such tools as low powered magnification,
optical microscope, electron microscope and x-ray diffraction.
- The science and technology of metals.
- Metal Smear
- When defects that are normally open to the surface
are partially or completely be covered over.
- One million electron volts.
- A prefix that divides a basic unit by one million.
- A crack of microscopic proportions.
- A graphic reproduction of the surface of a prepared specimen, usually etched,
at a magnification greater than ten diameter. If produced by photographic
means it is called a photomicrograph ( not a microphotograph).
- The hardness of microscopic areas or of the individual microconstituents
in a metal, as measured by such means as Tukon. Knoop or scratch methods.
Stresses - Residual stresses which vary from tension to compression
in a distance (presumably approximating the grain size) which is small compared
to the gage length in ordinary strain measurements. Hence not detectable by
dissection methods; they can sometimes be measured by x-ray shift.
- Segregation with a grain, crystal or small particle. Also called coring.
- A casting defect, not detectable at magnifications lower than ten diameters,
consisting of interdendritic voids. This defect results from contraction during
solidification where there is not an adequate opportunity to supply filler
material to compensate for shrinkage. Alloys with a wide range in solidification
temperature are particularly susceptible.
- The structure of polished and etched metals as revealed by a microscope
at a magnification greater than 25-50 times.
- A prefix that divides a basic unit by one thousand.
- Unit of electric current equal to one thousandth of an ampere.
- One thousandth of roentgen.
Angle Beam Block - A specific type of reference standard used primarily
for the angle beam method, but also for straight beam and surface wave tests.
- Appears as prominent darkened areas of variable dimensions with a definite
- The manner in which an acoustic wave is propagated, as characterized by
the particle motion in the wave (shear, Lamb, surface or longitudinal).
- Mode Conversion
- The change of ultrasonic wave propagation mode upon reflection and/or refraction
at an interface.
of Vibration - Type of wave motion. Three common modes used in ultrasonic
testing are longitudinal, transverse and surface wave.
- The treatment of a aluminum silicon alloys in the molten state with a small
percentage of an alkaline metal or salt, such as sodium fluoride, to change
the size and shape of the silicon particles in the solid metal.
Analysis - An instrumentation method, which separates desirable from
undesirable frequency signals from the modulating envelope of the carrier
- Test sample must move at constant speed.
- A measure of the stiffness of a metal in the elastic range. The degree to
which a metal will deflect when a given load of imposed on a given shape.
Also called Young’s modulus.
- A form or cavity into which molten metal is poured to produce a desired
shape. Molds may be made of sand, plaster or metal and frequently require
the use of cores and inserts for special applications.
- A Combination of two or more atoms held together
by chemical bonds.
- The linear momentum (p) of a body is the product
of its mass (m) and its velocity (v), i.e. p=mv.
- Periodic or continuous determination of the amount of ionizing radiation
or radioactive contamination present in an occupied region.
Techniques - These kind of techniques simply involve collecting data at
several different frequencies and then comparing the data or mixing the data
in some way.
- Any stress state in which two or three principal stresses are not zero.
Magnetization - Two or more separate fields, having different directions
can be imposed upon a part sequentially in rapid succession. When this is
done magnetic particle indications are formed when discontinuities are located
favorably with respect to the directions of each of the fields, and will persist
as long as the rapid alternations of field direction continue. This, in effect,
does constitute two or more fields in different directions at the same time,
and enables the detection of discontinuities oriented in all directions in
Back Reflections - Repetitive echoes from the far boundary of the
- Mutual Inductance
- When one circuit induces current flow in a second