GLOSSARY OF TERMS

Abrasion test

The process of grinding or wearing away through the use of abrasives; a roughening or scratching of a surface due to abrasive wear.
Abrasive wear

The general category of abrasive wear can be characterized by a single key word – cutting.
Abrasive wear

The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being abraded. Compare with adhesive wear.
Absorbed Does

The amount of energy, imparted to matter by an ionizing particle per unit mass of irradiated material at the place of interest. It is expressed in rads.
Absorption

The taking up of energy from the medium through which it passes.
Absorption Coefficient

The ratio of energy absorbed by a medium or material to the energy incident on the surface. If a flux through a material decreases with distance x in proportion to e-ax, then a is called the absorption coefficient. Also known as the absorption factor; absorption ratio; coefficient of absorption.
Absorption Coefficient, Linear

The fractional decrease in transmitted intensity per unit of absorber thickness. It is usually designated by the symbol µ and expressed in units of (cm-1.2).
Acceptance Standard

A controlled specimen containing natural or artificial discontinuities that are well defined and similar to the maximum acceptable discontinuity, in size and extent, in the product.
Acoustic Emission Testing (AE)

A nondestructive testing method that “listens” for transient elastic-waves generated due to a rapid release of strain energy caused by a structural alteration in a solid material.
Acoustic Impedance (Z)

The resistance of a material to the passage of sound waves. The value of this material property is the product of the material density and sound velocity. The acoustic impedance of a material determines how much sound will be transmitted and reflected when the wave encounters a boundary with another material. The larger the difference in acoustic impedance between two materials, the larger the amount of reflected energy will be.
Acoustic Properties

Intrinsic characteristics of any particular material that describe how sound travels through it. Such characteristics include the density, acoustic impedance, and sound velocity.
Adhesive wear

The removal or displacement of material from a surface by the welding together and subsequent shearing of minute areas of two surfaces that slide across each other under pressure. Compare with abrasive wear.
Adhesive wear

Like abrasive wear, adhesive wear can also be characterized by a single word. In the case of adhesive wear, the word is “welding,” or more precisely, “microwelding.”
Adjustment of a measuring system

Adjustment of a measuring system: set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given values of a quantity to be measured.
Aging tests and conditionings

The plastic and composite materials are used also in situations of exposure to atmospheric agents (UV radiations, oxygen, ozone …) and this can cause a rapid drop of the mechanical properties; to contrast these effects it is necessary to empower polymers with stabilizing substances.

Alligator skin

See orange peel.
Alligatoring

The longitudinal splitting of flat slabs in a piane parallel to the rolled surface. Also called fishmouthing.
Alpha Radiation

A stream of fast-moving helium nuclei. This is a strongly ionizing radiation with very weak penetration (e.g. cannot penetrate a piece of paper).
Alternating Current (AC)

Electric current that reverses direction periodically (usually many times per second).
Ambient

Surrounding; usually used in relation to temperature, as “ambient temperature” surrounding a certain part or assembly.
Amperage

A term used to describe the strength of electric current. The number of electrons moving past a fixed point in a conductor in one second. Measured in amperes. The term amps is often used for short.
Ampere

A standard unit of measure for electric current or the flow of electrons. The amount of current sent by one volt through a resistance of one ohm.
Analysis by Auger spectroscopy

The Auger spectroscopy allows to characterize the chemical composition of the sample surface both qualitatively and quantitatively.

Analysis by Auger spectroscopy for depth profiles

Using this technique can only be detected chemical elements present on the sample surface to a depth of about 1-5 nanometers.
It is possible to select the exact area of ​​interest on which perform the analysis.

Analysis by SEM-FIB

The SEM-FIB is an electron microscope with a resolution of 2nm, which allows to dig without damaging the surface of a sample and look at his section.

Analysis by XPS

The technique X-Ray Photoelectron Spectroscopy (XPS) allows to characterize the surface of a sample from a compositional point of view…
Analysis of additives and combustion gases

The most common polymeric and composite materials are highly flammable, and if it were not for the addition of specific anti-flame additives, the use of these materials would precluded in many fields.
The knowledge, for example, of the index of oxygen in a polymer as well as the level of damage regarding combustion fumes, may direct the purchase of the material according to intended use.

Analysis of phases

Metallic materials have a wide range of mechanical properties and this determines their particular versatility.
Using various techniques and processes, the related properties can be varied by changing peculiar characteristics such as, for example, the resistance.

Analysis of sensitisazion

A microstructural analysis is performed in order to evaluate the microstructure in a metal alloy.
Analysis of surface heat treatments

The heat treatment, whether it is a massive treatment or a superficial one, gives the material the desired characteristics in terms of mechanical properties, surface resistance and tonicity and therefore it guides the behavior in exercise and the mechanical and chemical response that the component presents in exercise conditions.

Analysis of the charges

Analysis through XRD (x-ray diffraction)

The analysis of a X-ray diffraction spectrum of (XRD), while not providing direct information on the chemical composition of a sample, allows to define and quantify the crystalline phases present in any material in the first 20 microns in surface.

Analysis through XRD (x-ray diffraction)

The analysis of a X-ray diffraction spectrum of (XRD), while not providing direct information on the chemical composition …
Angle Beam Testing

An ultrasound testing technique that uses an incidence wave angle other than 90 degrees to the test surface. The refracted angle of the sound energy is calculated using Snell’s law.
Angle Beam Transducers

A device used generated sound energy, send the energy into a material at angle other than 90 degrees to the surface, and receive reflected energy and convert it to electrical pulses.
Angle of Incidence

The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) incident on a body and the local normal to that body.
Angle of Reflection

The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) reflected by a body and the local normal to that body.
Angle of Refraction

The angle between the direction of propagation of an electromagnetic or acoustic wave (or ray) refracted by an optically homogeneous body and the local normal to that body.
Angular Frequency

For any oscillation, the number of vibrations per unit time, multiplied by 2π. Also known as angular velocity and radian frequency.
Annealing twin

A twin formed in a crystal during recrystallization.
Anode

The electrode of an electrolytic cell at which oxidation occurs. Contrast with cathode.
Anode

(1) The positive terminal or the collector of electrons in an electrical system (i.e. the positive terminal of a battery) (2) The electrode at which oxidation or corrosion occurs. It is the opposite of cathode.
Arrest lines (marks)

See beach marks.
A-Scan Display

A data presentation method in which signal amplitude is plotted along the y-axis versus time on the x-axis. The horizontal distance between any two signals represents the material distance between the two conditions causing the signals. In a linear system, the vertical excursion is proportional to the amplitude of the signal.
Asperity

In tribology, a protuberance in the small-scale topographical irregularities of a solid surface.
Atmospheric corrosion

The metals ordinarily used in equipment and structures corrode at a negligibie rate when exposed in to the atmosphere in the absence of moisture to serve as an electrolyte.
Atomic Number

A number representing the positive charge or number of protons in the nucleus of an atom.
Attenuation

The reduction in the level of a quantity, such as the intensity of a wave or radiation.
Attenuation Coefficient

A factor which is determined by the degree of reduction in sound wave energy per unit distance traveled. It is composed of two parts, one (absorption) proportional to frequency, the other (scattering) dependent on the ratio of grain size or particle size to wavelength.
Auger spectroscopy

The Auger spectroscopy allows to characterize the chemical composition of the sample surface both qualitatively and quantitatively.

Austenite

A nonmagnetic solid solution of ferric carbide or carbon in iron. An elevated-temperture parent phase in ferrous metals from which all other low-temperature structures are derived. The normal structures are derived. The normal condition of certain types of stainless steels.
Authorized qualifying body

Body, independent of the employer, authorized by the certification body to prepare and administer qualification examinations.
Axial

Longitudinal, or parallel to the axis or centerline of a part. Usually refers to axial compression or axial tension.
Axial strain

Increase (or decrease) in length resulting from a stress acting parallel to the longitudinal axis of a test specimen.
Back Reflection

The signal received from the far boundary or back surface of a test object.
Back Scatter

Scattered signals that are directed back to the transmitter/receiver.
Background indication

Background indication: indication obtained from a phenomenon, body, or substance similar to the one under investigation, but for which a quantity of interest is supposed not to be present, or is not contributing to the indication.
Backing

Material placed at the reverse side of a joint preparation for the purpose of supporting molten weld metal.
Bacterial and bio-fouling corrosion

Biological organisms affect corrosion processes on metals by directly influencing anodic and cathodic reactions, by affecting protective surface films on metals, by producing corrosive substances and by producing solid deposits.
Bainite

An intermediate transformation product from austenite in the heat treatment of steel. Bainite can somewhat resemble pearlite or martensite, depending on the transformation temperature.
Banded structure

A segregrated structure consisting of alternating, nearly parallel bands of different composition, typically aligned in the direction of primary hot working.
Base gas

Major or only component of a pure or mixed gas.
Base quantity

Quantity in a conventionally chosen subset of a given system of quantities, where no subset quantity can be expressed in terms of the others
Basic examination

Esame di livello 3 che dimostra la conoscenza del candidato sulla tecnologia e sulla scienza dei materiali, relative al settore di attività del candidato, del sistema di qualificazione e di certificazione e dei principi di base dei metodi PND come
richiesto per il livello 2.
Beach marks

Macroscopic (visible) progression marks on a fracture surface that indicate
successive position of the advancing crack front. The classic appearance is of irregular elliptical or semielliptical rings, radiating outward from one or more origins. Beach marks (also known as clamshell marks, tide marks, or arrest marks) are typically found on service fractures where the part is loaded randomly, intermittently, or with periodic variations in mean stress or alternating stress. Not to be confused with striations, which are microscopic and form differently.
Beachmarks

“Beachmarks” are a unique feature found in many fatigue fractures, and their presence is a positive means of identifying fatigue fractures.
Beam Alignment Measurements

Measurements that provide data on the degree of alignment between the sound beam axis and the transducer housing. This information is particularly useful in applications that require a high degree of certainty regarding beam positioning with respect to a mechanical reference surface.
Beam Exit Point

See probe index.
Beam Profiles

A measurement of the intensity of the beam across its width (or profile). It provides valuable information about transducer sound field characteristics.
Beam Spread

The divergence of the sound beam as it travels through a medium. Specifically, the solid angle that contains the main lobe of the beam in the far field.
Black-light

See ultraviolet light.
Blank indication

Blank indication: indication obtained from a phenomenon, body, or substance similar to the one under investigation, but for which a quantity of interest is supposed not to be present, or is not contributing to the indication.
Bottom Echo

See back reflection.
Breaking stress

See rupture stress.
Brinell hardness HB

A number related to the applied load and to the surface area of the permanent impression made by a ball indenter.
Brinell hardness test

A test for determining the hardness of a material by forcing a hard steel or carbide bali of specified diameter into it under a specified load. The result is expressed as the Brinell hardness number.
Brinelling

Damage to a solid bearing surface characterized by one or more plastically formed indentations brought about by overload. This term is often applied in the case of rolling-element bearings. See also false brinelling.
Brittle

Permitting little or no plastic (permanent) deformation prior to fracture.
Brittle crack propagation

A very sudden propagation of a crack with the absorption of no energy except that stored elastically in the body. Microscopic examination may reveal some deformation not noticeable to the unaided eye. Contrast with ductile crack propagation.
Brittle erosion behavior

Erosion behavior having characteristic properties (e. g., little or no plastic flow, the formation of cracks) that can be associated with brittle fracture of the exposed surface. The maximum volume removal occurs at an angle near 90°, in contrast to approximately 25° for ductile erosion behavior.
Brittle fracture

Separation of a solid accompanied by little or no macroscopic plastic deformation. Typically, brittle fracture occurs by rapid crack propagation with less expenditure of energy than for ductile fracture.
Brittle fracture of ductile steels

Brittle fracture of normally ductile steels has occurred primarily in large, continuous, box-like structures such as box beams, pressure vessels, tanks, pipes, ships, bridges, and other restrained structures, frequently joined with welded construction.
Brittleness

The tendency of a material to fracture without first undergoing significant plastic deformation. Contrast with ductility.
B-scan

A data presentation method applied to pulse echo techniques. It produces a two-dimensional view of a cross-sectional plane through the test object. The horizontal sweep is proportional to the distance along the test object and the vertical sweep is proportional to depth, showing the front and back surfaces and discontinuities between.
Buckle

(1)An indented valley in the surface of a sand casting due to expansion of the molding Band. (2) A local waviness in metal bar or sheet, usually transverse to the direction of rolling.
Buckling

A compression phenomenon that occurs when, after some critical level of load, a bulge, bend, bow, kink, or other wavy condition is produced in a beam, column, plate, bar, or sheet product form.
Buckling

Buckling is defined as collapse due to compressive instability. It is most common when long, slender columns are compressed in an axial direction, or when thin-walled tubes are compressed in either an axial direction or a diagonal direction as a result of torsional loading.
Bulk modulus

See bulk modulus of elasticity.
Bulk modulus of elasticity, K

The measure of resistance to change in volume; the ratio of hydrostatic stress to the corresponding unit change in volume.