Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 2417 (2003): Glossary of Terms Used in UltrasonicNon-Destructive Testing [MTD 21: Non-Destructive Testing]

IS 2417:2003

Indian Standard

GLOSSARY OF TERMS USED IN ULTRASONICNON-DESTRUCTIVE TESTING

(Second Revision )

{

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“!l

Ics 01,040; 19.100

0 BIS 2003

BUREAU OF INDIAN STANDARDSMANAK BHAVAN. 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

AugiNt 2003 Price Group 6

Non-destructive Testing Sectional Committee, MTD 2 I

FOREWORD

This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft finalizedby the Non-Destructive Testing Sectional Committee had been approved by the Metallurgical Engineering DivisionCouncil.

.

This standard was first published in 1963 and subsequently revised in 1977. In this revision the definition ofvarious terms have been made precise and up to date.

...

IS 2417:2003

Indian Standard

GLOSSARY OF TERMS USED IN ULTRASONICNON-DESTRUCTIVE TESTING

(Second Revision )

1 SCOPE

This standard defines the terms relating to ultrasonic

testing.

2 TERMS AND DEFINITIONS

A

A-scan Display — A cathode-ray tube display orpresentation in which the travel time of the ultrasonicpulse is represented along the X-axis and the pulseamplitude is represented along Y-axis.

Absorption — The 10SSor dissipation of sound energyas it travels through a medium. This loss is due to therelaxation or hysteresis, converted in the form of heatenergy. It is not due to scattering or beam divergence.It forms the part of attenuation.

Accuracy — The deviation of measured value fromthe true value.

Acoustic Impedance — See Specific Acousticimpedance.

Acoustical Impedance Matching — The coupling oftwo media using layers of material with suitableimpedances so as to provide optimum transmission of

acoustical energy between them.

Acoustical Shadow — The effect produced in a body

by its geometry, or by a discontinuity in it, wherebyultrasonic energy when traveling in a particulardirection is prevented from reaching a certain region,within the body.

Amplitude — The vertical pulse height of a signal,

usually base to peak, when indicated by an A-scanpresentation.

Angle of Beam Spread — Half of the solid angleformed by the peripheral rays in the main lobe of theultrasonic beam.

Angle of Incidence — The angle which the axis of anultrasonic beam makes with the normal to a planetangent to a surface at its point of incidence as it travelstowards that surface.

Angle of Reflection — The angle which the axis ofreflected ultrasonic beam makes with the normal tothe tangent plane to a reflecting interface, at the point

1

of incidence of the incident wave, as it travels awayfrom that interface in the same medium.

Angle of Refraction — The angle which the axis ofan ultrasonic beam makes with the normal to a tangentplane at an interface as it travels away from thatinterface into the second medium.

Angle of Squint — The angle between the side edgeof the probe and the projection of the beam axis on theplane of the probe face.

NOTE — For angle probes this normally relates to deviation inthe lateral direction.

Angle Probe — A contact probe from which the mainlobe of waves propagates at any angle, other than 0°or 90°, to the normal to the tangent plane to the surfaceat the place where the probe is positioned.

Array — A single housing containing an orderlyassembly of crystals in line which may be energizedtogether in groups, with or without time delay, to givedirectional effects, focused beams or variable anglebeams.

Area Amplitude Curve — A curve showing therelationship between different areas of reflectingtargets located at a constant distance and their

respective echo amplitude.

Attenuation — The loss or dissipation of sound energyas it travels through the medium. This loss is due tothe combination of absorption and scattering. It doesnot include loss due to mode conversion and beamdivergence.

Attenuation Coefficient — A measure of soundattenuation in a medium. It is also a measure of the

diminution in the amplitude of a wave per unit distancetravelled.

Attenuator — An instrument control by which theamplitude of an ultrasonic signal can be adjusted bycalibrated increments.

Automatic Scanning — Systematic relativedisplacement of the ultrasonic beam and the materialunder test by use of a manipulator, scanner or somegadget other than manual means.

AVG Diagram — A generalized family of curveswhich shows the relationship between normalized

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IS 2417:2003

distance along a beam to gain in decibel compared to projection of the test surface showing in plan view thea particular back wall echo and the specific size of a apparent size and position of reflectors in the volumeflat bottom hole reflector assuming zero attenuation. inspected by scanning an area of test surface line by

line. The pulse amplitude is manifested by the grayB shade or colours defined in an arbitrary colour scheme.

B-Scan Display — A cathode ray tube display orpresentation in which the X-axis represents the probeposition along the scan line and the Y-axis representsthe travel time of the ultrasonic pulse. This shows theapparent size and position of reflectors in the test pieceon a cross-sectional plane which is normal to the testsurface and contains the beam axis of the probe duringa single line scan.

Back Wall Echo — A pulse of ultrasonic energyreflected from the boundary of a body directly oppositeto the surface on which the probe is positioned andreturned to that surface by the shortest possible path.The term is generally restricted to normalcompressional waves and is sometimes referred to as

Calibration Block — A piece of material of specifiedcomposition, heat treatment, geometrical form andsurface texture by means of which the performance ofultrasonic flaw detection equipment can be assessedand calibrated for the examination of material of thesame general composition.

Calibration Reflector — A reflector of ultrasonicwaves, such as a drilled hole (flat bottom or sidedrilled), a machined slot or the end face of a specimenrepresentative of the material under test, which can beused to calibrate or set up the optimum conditions ofthe equipment for inspection purposes.

Combined Double Probe — See Twin Probe.

bottom echo or end echo. Compressional Wave — A form of wave motion in

Backing — The material attached to the rear surface which the particle displacement at each point in a

of the piezoelectric disc to increase the damping of material is parallel to the direction of propagation.

the transducer. Synonymous terms are longitudinal wave, dilatationalwave, and irrotational wave.

Band Width — The difference between twofrequencies on either side of the resonance frequency Contact Scanning — Scanning carried out by means

where the amplitudes are reduced to 0.7 (–3 dB) of the of an ultrasonic probe (or probes) in contact with the

amplitude at the peak frequency in the frequencybody under examination through a very thin layer of

spectrum of the reflected pulse.couplant.

Base Line — The horizontal trace, time of flight orContinuous Wave (CW) — A continuous flow of

distance, across the CRT display in the absence of anyultrasonic waves as opposed to pulse.

signal. Contracted Sweep — A contraction of the horizontal

Beam Angle –– Same as Angle of Refraction,sweep line or time axis on the viewing screen of theultrasonic instrument.

Beam Axis — The locus of points of maximumintensity in the far field in a beam of ultrasonic waves,

Convergence Point — The point of intersection of

and its geometrical prolongation into the near field.the axes of the transmitting and receiving sound fieldsin a twin probe. This is also usually the focus of the

Beam Divergence — The divergence of the main lobe twin probe.of an ultrasonic beam in the far field. Synonymousterm is Beam Spread.

Corner Effect — The reflection of ultrasonic energyback to a point coincident with, or very close to, its

Beam Index — The point on the surface of a body point of origin after impinging successively on two or

through which the beam axis passes (cJ ‘probe index’). three orthogonal surfaces.

Beam Spread — Same as Beam Divergence. Couplant — A liquid or semi-solid medium interposed

Blind Area — See Dead Zone.betsveen the probe and the object under examinationto enhance the transmission of ultrasonic energy

Boundary Echo (First) — A pulse of ultrasonic between them. Synonymous terms are Coupling Film

energy reflected from any boundary of a body to the and Coupling Medium.

surface on which the probe (or probes) is positionedCoupling Film — Same as Couplant.

and returned to that surface by the shortest possiblepath. Coupling Losses — The reduction in amplitude of

cultrasonic waves as a result of their passage throughthe couplant.

C-Scan Display — A two dimensional graphical Coupling Medium — Same as Couplant.

2

IS 2417:2003

Coupling Monitor — A probe operating in the Decibel — A unit used to express the magnitude of areceiving mode and positioned such that it detects change in the amplitude of an ultrasonic signal, definedultrasonic energy originating from a second probe (or by the equation, dB = 2010g10 (A /A2), where A, andprobes) thereby monitoring that successful coupling A2 are the amplitudes of the ultrasonic signals 1 and 2,is taking place between the second probe and the body. respectively.

Critical Angle — The angle of incidence of a beam Defect Detection Sensitivity — The level of

of ultrasound on to an interface at which one of the sensitivity setting of an ultrasonic flaw detector forrefracted wave modes has an angle of refraction of revealing the presence of minimum specific size of90°. defects in a given application.

Cross Talk — Acoustical or electrical signal leakage Delay — A cathode ray tube control that is used toacross an intended barrier between the transmitting and shift the initial part of the time scale laterally.receiving transducer elements such as in case of twin Synonymous terms are Delayed Time Base Sweep andprobe. Synonymous term is Cross Noise. Zero Shift.

Crystal (Ultrasonic) - Part of a single crystal or Delayed Sweep — An A-scan or B-scan presentation

polycrystalline plate having piezoelectric properties, in which the initial part of the screen is shifted.

used for the generation and /or reception of ultrasonicDelayed Time Base Sweep — Same as Delay.

waves. Ceramic material is also usually called as crystal

in ultrasonics though it is not correct in strict sense. Depth of Penetration — Maximum depth in the object

Synonymous term is Transducer Element. under examination where the ultrasonic energy is

Crystal Loading — The mechanical power per unitsufficient for proper detection of discontinuities.

surface area deli~ered by a crystal to a medium Depth Range — See Range.acoustically coupled to it.

DGS Diagram — Same as AVG diagram.Crystal Mosaic — A regular assembly of ultrasoniccrystals, in which each crystal is of identical material

Diffraction — Deviation in the propagation of

and cut, and is mounted in such away that the assemblyultrasonic wave from its normal course. See FresnelDiffraction and Fraunhofer Diffraction.

or matrix of crystals tends to behave as though it werea single cr-ystai. Diffuse Reflection — Reflection of an ultrasonic wave

Curved Crystal — A non-planar crystal generallyused to improve coupling or focusing.

Cylindrical Reflector — A reflecting surface in theform of a circular cylinder.

D

D-Scan Display — A two dimensional graphicalprojection onto a plane normal to the test surface andnormal to the projection of the beam direction on the

test surface, showing the apparent size and position ofreflectors in the volume inspected by scanning an area

of test surface.

Damped Oscillations — Oscillations in which theamplitude of successive cycles diminish.

Dead Zone — The region in a material adjoining thesurface of entry from which no direct echoes fromdiscontinuities can be detected due to the characteristicsof the ultrasonic equipment and probe in associationwit h the material under test and its surface condition.

Decay Technique — A technique of using ultrasonicwaves to assess the quality of a material or a bond by

studying the amplitudes of successive echoes.

dB — Acronym for decibel.

from a rough surface in a manner such that the reflectedenergy is detectable over a range of angles on eitherside of the theoretical angle of specular reflection thatis, reflection in a non-specular manner.

Directional Sensitivity — The relationship betweenthe angle made with the normal to the surface of areflector by z beam of ultrasonic waves and theamplitude of the resultant echo.

Dilatational Wave — See Compressional Wave.

Direct Scan — See Single Traverse Technique,

Discontinuity — A break or interruption, eitherintentional or otherwise, in the normal physical

structure or configuration of material.

Dispersive Medium — A material in which the phasevelocity of an ultrasonic wave varies with frequency.

Distance Amplitude Correction — Change inamplification of ultrasonic signals to provide equalamplitude from equal area reflectors at differentdistances. Synonymous terms are Time CompensatedGain and Swept Gain.

Distance Amplitude Curve — A curve constructedfrom the peak amplitude responses from reflectors ofequal area at different distances in the same material.

3

...

IS 2417:2003

Distortional Wave — See Shear Wave.

Double Bouncer Technique — See Triple TraverseTechnique.

Double Crystal Probe — See Twin Probe.

Double Probe Technique — An ultrasonic testingtechnique involving the use of one probe fortransmission and the other for reception.

Double Skip Technique — An ultrasonic testingtechnique whereby the distance between the pointwhere the waves enter the body and the region underexamination is twice the skip distance.

Double Transreceiver Technique — An ultrasonictesting technique involving the use of two probes; eachbeing used simultaneously as a transmitter and receiver.

Double Traverse Technique — A testing techniquein which a beam of ultrasonic waves is directed into a

region of a body under examination after having beenreflected by a surface of the body. Synonymous termis Single Bounce Technique.

Dry Coupling Probe — A probe fitted with softpolymer pad on its radiating face. The pad, underpressure, adapts to the peaks and troughs of the testsurface, making good contact and obliviating the needof couplant for transmission of ultrasonic waves intothe test material.

Dual Probe — See Twin Probe,

Dynamic Range — The range of signal amplitude thatcan be handled by electronic or ultrasonic equipmentwithout overloading or excessive distortion andwithout being too small for detection. It is usuallyexpressed in decibels (dB).

E

Echo -– A distinct pulse of ultrasonic energy reflected

from any surface or discontinuity. Its display oncathode ray tube is usually a rectified pulse.

Echo Amplitude — See Echo Height.

Echo Height — Amplitude of echo measured frombase of cathode ray tube, when displayed in A-scan.Synonymous terms are Echo Amplitude and PulseAmplitude.

Echo Width — Width of back wall echo with a heightof 80 percent FSH, at near field or focus, read off at ascreen height of 20 percent. [t is a measure of farresolution of probe.

Electromagnetic Acoustic Transducer — Atransducer in which eddy currents are produced at aconducting surface adjacent to the transducer in thepresence of a static magnetic field, the interaction of

two fields producing a mechanical deformation of thesurface thereby generating ultrasonic vibrations andvice versa. Acronym is EMAT.

Electronic Noise — Unwanted, ra~dom signals thatvary rapidly with time, caused by electronic pick upand thermal noise in the amplifier of the flaw detector.

Entry Surface Resolution — Ability to resolve entrysurface echo (transmission pulse in contact testing andinterface echo in immersion testing) from the echo of

a nearby reflector.

Evaluation — The process of deciding the severity ofthe condition after the echoes have been interpreted,Evaluation leads to the decision as to whether the parttested needs to be rejected, salvaged or may be acceptedfor use.

Expanded Time Base Sweep — See Scale Expansion.

F

Far Field — The region in an ultrasonic beam wherethe pressure starts falling as inversely proportional tothe square of the distance due to Fraunhofer diffraction.Synonymous terms are Fraunhofer Region andFraunhofer Zone.

Far Resolution — Ability to resolve echoes from twonearby reflectors in the far field. See also Echo Width.

Filter — Device to suppress unwanted frequency

components electronically. Synonymous term isFrequency Filter.

Flat Bottomed Hole — A cylindrical blind hole witha flat bottom, the flat bottom surface being used as theultrasonic reflector.

Flat Bottomed Hole Equivalent — The size of flatbottomed hole which gives an echo height equal tothat from the discontinuity, at the same distance.

Flaw Echo — Echo from an imperfection in an objectunder examination.

Flaw Location Scale — A specially graduated devicethat can be attached to a shear wave probe which, inconjunction with the position of the flaw echo on thescreen of the cathode ray tube, gives a direct readingof the location of the discontinuity within the body.

Focal Diameter — Diameter of the circle with centreat the focal point in the focal plane, the points at whosecircumference has half the acoustic pressure of that atthe focal point.

Focal Distance — The distance from the transducerto focal point.

Focal Plane — The plane normal to the beam axisand passing through the focal point.

4

.

1

IS 2417:2003

Focal Point — The point in the acoustic field of the Gap Scanning — A form of scanning in which thetransducer having maximum acoustic pressure or a probe carrier follows the contour of the material underpoint from where a small reflector gives maximum examination but the probe, whilst not in direct contactecho height. with its surface, is coupled to it through a layer or jet

Focused Probe — A probe incorporating an acousticof liquid which is maintained between the surfaces of

lens or a suitably curved crystal, so as to producethe probe and the material. Synonymous term is

focusing of the ultrasonic beam.Bubbler Technique.

Fractional Band Width — The ratio of band. widthGate — An electronic means of monitoring a selected

to resonance frequency, usually expressed inregion of the cathode ray tube display of an ultrasonicflaw detector.

percentage.

Fraunhofer Diffraction — It results into theGate Width — The width of the gate on the time scale,

divergence of ultrasonic beam after the last maximalusually expressed as percentage of the range selected.

of the Fresnel region. The acoustic pressure along thebeam axis is inversely proportional to the square ofthe normalized distance.

Fraunhofer Region — Same as Far Field,

Fraunhofer Zone — Same as Far Field.

Fresnel Diffraction — [tresults into the variation ofacoustic pressure near the ultrasonic transducer in theFresnel zone. The pressure along the beam axis showsa number of maximal and minimal.

Fresnel Region — See Near Field.

Fresnel Zone — See Near Field.

Frequency Band Width — Same as Band Width.

Frequency Filter — Same as Filter.

Frequency Spectrum — Variation of signal amplitudewith frequency. The frequency spectrum of an echoshows the variation of amplitude with frequency ofconstituent sine wave pulses. Synonymous term is

Ultrasonic Spectrum.

FSH — Abbreviation for Full Screen Height,equivalent to maximum height of the cathode ray tubedisplay or range of the vertical scale.

Fundamental Resonance Frequency — The lowestfrequency at which the resonance occurs.

Full Skip Technique — An ultrasonic angle beamtesting technique whereby the inspection of a regionof a body is accomplished by using shear wavesentering the same surface at a point that is one fullVee path away.

G

Gain Control — Same as Attenuator.

Gain Reserve — The difference in dB between thegain control positions of the ultrasonic flaw detectorat which the back wall echo at near field length 50

percent FSH and at which the noise level is 2 percentFSH.

Ghost Echo — An unwanted echo or an indicationarising from an incorrectly matched combination ofpulse repetition frequency and sweep frequency (timebase range). Synonymous term is Phantom Echo orWrap Around.

Grass — Spatially random signals arising from thereflection of ultrasonic waves from grain boundariesand/or microscopic reflectors in a material.

Synonymous term is Hash.

Grazing Incidence — Angle of incidence slightly lessthan 90°. Used in immersion testing for directing thebeam on the surface of the sample.

Group Velocity — The velocity with which theenvelope of a wave propagates.

H

Half Skip Technique — An ultrasonic testingtechnique in which the inspection of a surface regionof a body is accomplished by using angle beam enteringfrom the opposite surface of a point corresponding tothe half skip distance.

Hard Faced Probe — A probe in which the contactsurface is of hard material, such as steel or ceramic, tominimize wear and tear.

Harmonics — The integral multiple of fundamentalresonance frequency, the second harmonic being twice

the fundamental frequency.

Hash — Same as Grass.

Head Wave — A shear wave that is generated by modetransformation when a compressional wave travels atgrazing angle on a free solid surface. In steel, forexample, the head wave is at an angle of 33°.

Hole Bottom — The flat reflecting surface of a flatbottom hole.

Holography (Ultrasonic) — An ultrasonic imagefrom two transducers, the beams of which are

positioned to produce an interference pattern, usuallyon a liquid surface, which is illuminated by laser light

5

IS 2417:2003

andproduces a visible indication of ultrasonic waveintensity distribution. One of the transducer beams is

the reference beam.

Horizontal Linearity — Linearity of horizontal scaleof ultrasonic flaw detector measured for distance as afunction of time.

1

Immersion Probe — A compressional wave probedesigned to be used when immersed in a liquid.

Immersion Testing — An ultrasonic testing techniquein which the material under test and the probe(s) are

partially or fully immersed in a fluid usually water.The test surface of the material and the radiating surfaceof the probe must b$ fully submerged in fluid.

Indexing — The automatic measurement of probeposition, usually electrically, to generate probe positiondata that can be recorded.

Indication — Vertical deflection above the time baseon CRT screen.

Indirect Scan — The use of a surface (or surface) ofa body to direct an ultrasonic beam into a particularregion of the body, usually the inaccessible region.

Initial Pulse — The first indication appearing oncathode ray tube which represents the emission ofultrasonic energy from the probe. Synonymous termsare Main Bang and Transmitted Pulse.

Interface — The transition region between twomaterials of different acoustic impedances in acoustical

contact.

Interface Signal — The displayed ultrasonic signalarising from the part reflection of an incident pulse atan interface.

Interface Trigger — An interface signal that is usedas the initiating point from which other timingsequences (for example, gate position) are referenced.

Internal Echoes — Unwanted signals generatedwithin an ultrasonic probe.

Irrotational Wave — Same as Compressional Wave.

L

Lamb Wave — A specific mode of vibration in whichtwo parallel surfaces of the material (such as plate ortube wall) under examination contribute to thepropagation of waves. The waves propagate in thematerial in a direction parallel to the surface of theplate. Lamb waves can be generated only at specific

values of frequency, angle of incidence and materialthickness. Synonymous term is Plate Wave.

beam will not touch the inner wall whilecircumferentially scanning the tubular products fromoutside surface.

Linearity (Amplitude) — Same as Vertical Linearity.

Linearity (Time Base) — Same as Horizontal

Linearity.

Logarithmic Amplifier — An amplifier where the

output is related logarithmically to the amplitude of

the input signal.

Logarithmic Decrement — For a damped train, the

natural logarithm of the ratio of the peak values of the

amplitudes of two successive cycles.

Longitudinal Wave — Same as Compressional Wave.

Longitudinal Wave Probe — A probe used to

generate and receive the longitudinal ultrasonic wave.

Loss of Back Wall Echo — The absence or significantreduction in the amplitude of the indication from back

wall of the test sample.

Love Wave — An acoustical wave which propagates

along a stratum bounded on both sides by layers ofmaterial which differ from the stratum in elastic

properties. The particle displacement of the wave is

parallel to the stratum and perpendicular to the direction

of propagation.

M

Magnetostrictive Transducer — A transducer in

which the application of a magnetic field on the active

element of the transducer produces mechanical

deformation of the active element, thereby generating

ultrasonic vibrations and vice versa.

Main Bang — Same as Initial Pulse.

Maximum Working Range — The total distance thata probe will transmit sufficient energy to find the

smallest reflector to be detected.

Mode — The vibration pattern of waves.

Mode Conversion — The process by which a wave

of a given mode of propagation is caused to generatewaves of other modes by refraction or reflection at a

surface or boundary. Synonymous terms are Mode

Transformation and Wave Transformation.

Mode Transformation — Same as Mode Conversion.

Multiple Echo — The repeated reflection of an

ultrasonic pulse between two or more surfaces or

discontinuities in a body.

Multiplexer — A device for electrically connectingprobes to various channels in sequence.

Limiting Angle — Angle above which the ultrasonic

6

N

N-Distance — The distance from the probe to theN-point.

N-Point — The position in the Near Field where theacoustic pressure on the beam axis reaches a final andlast maximum before beginning a uniform reductionwith distance.

Near Field — The region in an ultrasonic beam that is

subject to variations of acoustic pressure due to Fresneldiffraction effects, extending from the source ofradiation to the last axial maximum in pressure.Synonymous terms are Fresnel Zone, Fresnel Regionand Near Zone.

Near Resolution — Ability to resolve echoes from asmall reflector near the surface and from the surfaceitself. It is usually expressed as diameter in mm of a

side drilled hole at the depth of hole in mm.

Near Zone — Same as Near Field.

Noise — Any undesired signal (acoustic or electrical)that tends to interfere with the reception, interpretationor processing of the desired signal.

Nominal Frequency — The frequency of theultrasonic transducer as specified by the manufacturer,normally the resonance frequency of the piezoelectricdisc used to manufacture the transducer. It is also themean frequency of several probes of same type fromthe same manufacturer.

Normal Probe — A probe from which waves emergeat 90° to the contact surface.

Normal Incidence — A condition where the axis ofthe incident ultrasonic beam is perpendicular to the

entry surface of the test material.

Normalized Distance — The distance from the probedivided by the N-distance. It is a dimensionlessquantity.

o

Oblique Incidence — The impingement of a wave ona surface at any angle to the normal to the tangent planeat the point of incidence other than 0° or grazingincidence.

Opacity Technique — An ultrasonic shear wavetechnique for the examination of thin plate whichmakes use of the principle that if the plate thickness isless than a minimum value, ultrasonic waves at a fixedangle and frequency are unable to propagate. It is aspecial technique employing the characteristics ofLamb waves.

Operating Frequency — The centre frequency in thefrequency spectrum of the echo received (and

IS 2417:2003

generated) by the ultrasonic probe under question.

Operating Range — The distance range for atransducer in which a small reflector, such as a 2 mm

flat bottom hole in low attenuating material, gives aclearly detectable echo.

Optimum Coupling — The coupling that transfersthe maximum energy.

P

Parasitic Echo — See Spurious Echo.

Peripheral Rays — Virtual lines in the far field of the

ultrasonic transducer along which the acoustic pressurefalls to certain value of the pressure at the axis in thesame plane normal to the beam axis. This value is

usually –6dB (50 percent) or –20dB (10 percent).

Phantom Echo — Same as Ghost Echo.

Phase — The parameter defining the position in a cycle

of wave, expressed in time, radian or degree.

Phase Velocity — The velocity with which the phase

propagates along the wave.

Piezoelectric Effect — An effect in which theapplication of an electric field across certain element

produces mechanical deformation of the element andvi~e versa. The phenomenon is known aspiezoelectricity.

Piezoelectric Transducer — A transducer using

piezoelectric material as an active element.

Pitch and Catch Technique — An ultrasonic testing

involving the use of two separate probes; one probe

being used to transmit (pitch) the ultrasonic energy

into a body and the other being positioned so as to

receive (catch) the reflected, or transmitted energy.When both of the probes are on the same side of the

test material, the technique is synonymous to Tandem

Technique and when the probes are on the oppositesides, the technique is synonymous to ThroughTransmission.

Plane Wave — A wave in which points of the samephase lie on parallel plane surfaces.

Plate Wave — Same as Lamb Wave.

PRF — Short form of Pulse Repetition Frequency.

Primary Scan Axis — The major direction of probescanning movement.

Probe — An electromechanical device, usuallyincorporating one or more ultrasonic transducers, and

functioning as a generator and/or receiver of ultrasonicwaves. Synonymous term is Search Unit.

Probe Array — An array of probes which may

7

[S 2417:2003

comprise: (a) probes in a mechanical holder which scan body. Synonymous term is Triple Bounce Technique.together and are used sequentially individually andlorin pairs, or (b) a single unit comprising probes used as

Quality Factor — An assessment of damping of the

in (a).Initial Pulse. It is the ratio of resonance frequency to

band width.Probe Face ——That part of a probe through whichultrasonic waves are transmitted and received.

Probe Index — The point on a shear wave probe or asurface wave probe through which the emergent beamaxis passes.

Probe Shoe — A shaped piece of solid materialinterposed between the probe and the material underexamination for the purpose of improving acousticalcontact. Synonymous term is Shoe.

Probe Shoe Delay — The time taken for the ultrasonicwave to traverse through the probe shoe from the

ultrasonic crystal to shoe face and back.

Proportional Output — An output signal fromultrasonic or electronic equipment which isproportional to the peak amplitude of an inputultrasonic pulse, such as a defect echo.

Pulse — A packet of waves of short duration.

Pulse Amplitude — Same as Echo Height.

Pulse Duration — See Pulse Length,

Pulse Echo Technique — A technique in which thetransmission of ultrasonic waves is done in pulses andthe quality of the material is assessed by the reflection

of pulses from discontinuities or back surface.

Pulse Energy — The total energy associated with asingle pulse.

Pulse Envelope — The outline of a pulse indication.

Pulse Length — The time interval between the leading

and trailing edges of a pulse, usually measured at thehalf pulse amplitude value. Synonymous terms arePulse Duration and Pulse Width.

Pulse Repetition Frequency — The number of pulsestransmitted per second. Short form is PRF.

Pulse Tuning — A control in ultrasonic equipmentused to optimize the response of the probe (along withcable) to the transmitter by changing the shape of thetransmitted pulse.

Pulse Width — Same as Pulse Length.

R

Range — The maximum ultrasonic path length thatmay be displayed on the cathode ray tube at a giventime base setting. Synonymous terms are Depth Rangeand Time Base Range.

Rayleigh Wave — A particular type of surface wavewhich propagates on the surface of a body and whoseeffective penetration is maximum of one wavelength.The particle motion is elliptical and the plane ofvibration is perpendicular to the direction ofpropagation.

Reference Block- A block that is used to provideboth, a measuring scale and an ultrasonic reflection ofknown reflection.

Reference Piece — An aid to interpretation in the formof a test piece of the similar acoustical characteristics,significant dimensions and shape as a particular objectunder examination. Such pieces may or may notcontain natural or artificial imperfections. Synonymous

term is Test Block.

Reference Standard — A piece or block having anartificial] y produced imperfection of predetermineddimensions, usually a notch or a hole, used for the solepurpose of setting up the test sensitivity of theultrasonic flaw detection equipment.

Reflecting Surface — An interface at which the

ultrasonic beam encounters a change in acousticimpedance.

Reflection Coefficient — The ratio of reflected soundamplitude to incident sound amplitude at a reflectingsurface. Synonymous terms is Reflection Factor.

Reflection Factor — Same as Reflection Coefficient.

Reflection Technique — A technique in which thepresence of discontinuities in a material is indicatedby receiving the reflected energy from them.

Reflector — An interface at which an ultrasonic beamencounters a change in acoustic impedance and atwhich at least a part of the ultrasonic energy isreflected.

Q Refracting Prism — See Wedge. A prism, usually of

Q -— Short form of Quality Factor. plastics material, when placed in acoustical contact

Quadruple Traverse Technique — A technique inbetween an ultrasonic transducer and a body will cause

which a beam of ultrasonic waves is directed into aultrasonic waves to be refracted at a known angle intothat body.

region of a body under examination, after having beenreflected successively three times by surfaces ~f the Refractive Index — The ratio of the ultrasonic

8

velocity of an incident wave in one material, to thevelocity of a refracted wave in a second material is therefractive index of second material with respect to thefirst.

Rejection — See Suppression.

Resolution — The ability of ultrasonic flaw detectionsystem to separate the echoes from two targets whichare close together. If the resolution is referred to targetsin depth, it is called axial resolution and if it refers totargets perpendicular to beam axis, it is called lateralresolution. Synonymous term is Resolving Power.

Resolving Power — Same as Resolution.

Resonance Technique — An examination techniquewhich involves varying the frequency of ultrasonicwaves to excite a maximum amplitude of vibration in

a body, or part of a body, generally for the purpose ofdetermining thickness from one side only.

Reverberation Time — The time required for theintensity of an unsustained vibration in a closed systemto come down to one millionth of its initial value, thatis by 60 dB.

RF Display — Display of unrectified signal on theCRT screen.

Ringing Time — The time during which themechanical vibrations of a crystal continue after theelectrical pulse has stopped.

Roof Angle — The angle between the emergingultrasonic beam and normal to the probe’s front surfacein a twin probe.

Rotational Wave — See Shear Wave.

s

SAFT — Acronym for Synthetic Aperture FocusingTechnique. A signal processing method used to reducethe smearing effect in ultrasonic image. The smearing

effect is a result of beam spreading of ultrasonic wavesand makes a straight object look like an arc shapedobject. The arc shaped image takes the size and shapeof the actual object after signal processing.

Saturation — A condition in which an increase in theinput signal does not produce any increase in thedisplay amplitude.

Scale Expansion — An increased speed of time basespot sweep which enables echoes from a selectedregion within the thickness or length of a body to bedisplayed in greater detail on the screen of theultrasonic flaw detector. Synonymous term isExpanded Time Base Sweep.

Scan Pitch — The pitch or distance betweensuccessive lines of scan during movement of the

IS 2417:2003

probe(s) over the scan area.

Scanning — Systematic relative displacement of theultrasonic beam and the material under test.

Scattering — Energy reflected in a random way bysmall reflectors such as grain boundaries, irregularshaped defects, etc, in the path of a beam of ultrasonicwaves.

Schnozzle — See Stand Off Block.

Schlieren System — An optical system used to displayan ultrasonic beam visually, by passing it through atransparent medium.

Screen Marker — Small electronically generatedpulses, following one another at a preset time interval,which are presented on a time base sweep to provide acalibration less dependent on the linearity of the timebase. It is used to measure time or distance.

Synonymous term is Time Marker.

Search Unit — Same as Probe.

Sensitivity — The ability of the ultrasonic flawdetection system to detect the smallest flaw.

Sequence Number — In an automatic testing system,the order of connection of channels and probes requiredto perform defined scans.

Shadow Technique — A technique in which adiscontinuity in a material is revealed by the acousticalshadow it produces.

Shadow Zone — A region in a body which cannot bereached by ultrasonic energy traveling in a given

direction, because of the shape of the body or adiscontinuity in it.

Shear Wave — A form of wave motion in which theparticle displacement at each point in a material is atright angles to the direction of propagation.

Synonymous terms are Distortional Wave, RotationalWave, Transverse Wave.

Shear Wave Probe — A probe for generating ordetecting shear waves.

Short Pulse — A pulse which has a few (usually lessthan 1.5) cycles in the time interval over which itsamplitude exceeds half of its maximum amplitude.

Shoe — Same as Probe Shoe.

Side Drilled Holes — Cylindrical holes drilled parallelto the test surface and at’right angles to the vertical

plane of the probe, the cylindrical surfaces of whichform the ultrasonic reflectors.

Side Lobe — A peak of pronounced shoulder in anultrasonic beam, lying to either side of the main beam.

Signal to Noise Ratio — The ratio of the amplitude

9

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1S 2417:2003

of an ultrasonic echo arising from a discontinuity in a Synonymous term is Schnozzle.material, to the amplitude of the average background - . ‘.

Subsldlary Maximal — Irregular fluctuations in thenoise.

response of a small reflector as an ultrasonic beam isSingle Bounce Technique — Same as Double scanned over it.Traverse Technique.

Single Traverse Technique — An examinationtechnique in which a beam of ultrasonic waves isdirected into a region of a body under examinationwithout intermediate reflection. Synonymous term is

Direct Scan.

Sizing Technique — A technique which enables anestimate of the size of a discontinuity to be made fromits ultrasonic responses. Examples of sizing techniquesare 6 dB drop (half maximum) technique, 20 dB droptechnique, maximum amplitude technique.

Suppression — The reduction of grass by theelimination of all signals below a predeterminedamplitude. Synonymous term is Rejection.

Surface Noise — Unwanted signals at very shortrange, produced by ultrasonic waves being reflectedwithin the coupling film and from irregularities of thesurface.

Surface Preparation — The processing of a surfacenecessary to render it suitable for providing goodacoustical coupling for ultrasonic testing.

Skip Distance — For a beam of shear waves enteringSurface Wave — An ultrasonic wave which

a body, that distance measured over the surface of thepropagates on the surface of a body.

body between the probe index and the point where the Surface Wave Probe — A probe for generating andlbeam axis impinges on the same surface after a single or detecting surface waves.reflection from the opposite surface.

Sweep — Uniform and repetitive movement ofSoft Faced Probe — A probe in which the contact electronic beam across the ho~izontal axis of the CRTsurface is a flexible membrane and the space between screen.the crystal and the membrane is filled with a liquid

Swept Gain — Same as Distance Amplitudecouplant.

Correction.Soft Tipped Probe — A probe in which a thick flexible

Swivel Scan — A shear wave technique used tomedium forms the coupling between its crystal andthe surface of the material under test.

provide information about the form of a previouslylocated discontinuity, the probe(s) being positioned at

Specific Acoustic Impedance — A property of amedium which determines the amount of reflection thatoccurs at an interface with another medium. It is

defined mathematically as the product of the densityof the medium and the velocity of the wave travelingthrough it. Synonymous term is Acoustic Impedance.

Specular Reflection — A mirror like reflection of anultrasonic beam such that the angle of incidence isequal to the angle of reflection.

Spherical Wave — A wave in which points of thesame phase lie on the surfaces of concentric spheres.

a constant distance from, and directed at, thediscontinuity and rotated through an angle up to 360°.

T

Tandem Technique — An angle beam ultrasonictesting involving the use of two separate probes; oneprobe being used to transmit the ultrasonic energy intoa body and the other being positioned so as to receivethe reflected or re-directed energy ilom a discontinuity.It is used to detect vertically oriented flaws in thickmaterial. In variation of the technique, more than two

probes may be used.

Spurious Echo — A term used for any indication not Test Block — Same as Reference Piece.obviously associated with a discontinuity or boundary.

Synonymous term is Parasitic Echo. Test Frequency — Nominal frequency of the

Standing Wave — The resultant of the superpositionultrasonic wave generated by the transducer at whichtesting is deemed to be carried out.

of waves moving in opposite directions with theformation of stationary nodes and antinodes. Test Surface — The surface of a piece of material

Synonymous term is Stationary Wave. through which ultrasonic waves pass.

Stationary Wave — Same as Standing Wave. Threshold — The minimum signal amplitude that isregarded as significant in a particular ultrasonic

Stand Off Block — A block, usually of plastic examination.material, attached to the probe to separate it from thesurface of the test piece. The use of such blocks is Through Transmission — A test method using two

geneml]y confined to compressional wave probes. transducers in which the ultrasonic vibrations are

10

emitted by one and received by another on the oppositeside of the test object. The difference in acousticpressure or intensity at the receiving probe is used ascriterion of soundness.

Time Base — A trace on the screen of a cathode raytube which is generated in such a way that distancealong it is proportional to time.

Time Base Range — Same as Range.

Time Compensated Gain — Same as DistanceAmplitude Correction.

Time Marker — See Screen Marker

Toe in Semi Angle — Half the angle between thenormals to the crystal faces in a twin crystal probe.

TOFD — Acronym for Time Of Flight Diffraction,Technique in which two angle beam probes scan thematerial in tandem. The extremities of the flaw, suchas crack, present in the material will diffract theultrasonic waves and appear in the display at aparticular time of flight depending on the location andsize of flaw.

Tone Burst — A pulse consisting of single frequencysine wave, usually all the cycles having sameamplitude.

Total Attenuation — The diminution of intensity ofa particular mode with travel range, of an ultrasonicbeam of any form, arising from the combined effectsof absorption, scatter and geometric beam spread.

Total (Internal) Reflection — Reflection which

occurs when the angle of incidence is greater than thecritical angle and the reflection coefficient is unity.

Transceiver — A probe used to generate and detectultrasonic energy.

Transducer — An electro acoustical device forconverting electrical energy into acoustical energy andvi~~ l~er.$a.

Transducer Element — Same as Crystal.

Transmission Coefficient — The ratio of ultrasonicwave intensity transmitted across an interface, to thetotal wave energy incident upon the interface.

Transmission Point — The point on the time basethat corresponds to the instant at which ultrasonicenergy enters the material under examination.

Transmission Technique — A technique in whichthe quality of a material is assessed by the intensity ofthe ultrasonic wave incident on a receiving probe afterthe waves have travelled through the material.

Transmitted Pulse — Same as Initial Pulse.

Transverse Wave — Same as Shear Wave.

11

1S 2417:2003

Trigger/Alarm Condition — The condition where theequipment indicates that a portion of materials issugpected.

Trigger/Alarm Level — The level at which theultrasonic equipment is required to differentiatebetween acceptable and suspect material.

Triple Bounce Technique — Same as QuadrupleTraverse Technique.

Triple Traverse Technique — A technique in whicha beam of ultrasonic waves is directed into a region ofa body under examination after having been reflectedsuccessively by two surfaces of the body, Synonymousterms is Double Bounce Technique.

Twin Probe — A probe comprising two separatecrystals in a single housing; one acting as a transmitterand the other as a receiver. Synonymous terms areDouble Crystal Probe and Dual Probe.

uUltrasonic Frequency — Any frequency of vibrationgreater than the range of audibility of the human ear,generally taken as greater than 20 kHz.

Ultrasonic Mode Changer — A device which causesvibration of a particular mode (for examplecompressional ) in one body to produce vibrations ofanother mode (for example shear) in another body.

Ultrasonic Spectrum — Same as FrequencySpectrum.

Ultrasonic Wave — A disturbance (mechanicalvibration) which travels through a material at ultrasonicfrequencies by virtue of the elastic properties of thatmaterial.

vVee Path — The angle beam path starting from probeindex and then striking top and bottom surfacesalternately through the material. The path is usuallyshaped like the reman letter V.

Vertical Linearity — Proportionality of echo heightwith variation in gain of ultrasonic flaw detectorsamplifier for entire range. Deviation fromproportionality is called non-linearity and is usuallyexpressed in percentage.

Video Presentation — CRT display of rectified pulse.

w

Water Path — The distance from the probes frontface to the incident surface of the test sample inimmersion or water column testing.

Wave Front — A continuous surfacelocus of points having the same phase.

which is the

,-

1’

1

1S 2417:2003

Wave Length — Distance between two successiveparticles vibrating in same phase.

Wave Train — A succession of ultrasonic pulses

arising from the same source having the samecharacteristics.

Wave Transformation — Same as Mode Conversion.

Wedge --– A device, usually of plastic material, whenplaced in acoustical contact between an ultrasonictransducer and a body will cause ultrasonic waves tobe refracted at a desired angle into that body.Synonymous term is Refracting Prism if the device is

in prism shape.

Wetting Agent — A substance added to a couplingliquid to decrease its surface tension and thus increaseits wetting ability.

Wheel Probe — A device housing one or more probesinside a liquid tilled tire. The rolling contact areaprovides the coupling between the probes and testsample.

zZero Shift — Same as Delay.

12

Bureau of Indian Standards

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periodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates’-that changes are needed, it is taken up for revision. Llsers of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of

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This Indian Standard has been developed from DOC : No. MTD21 (4240).

Amendments Issued Since Publication

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