An Introduction to Radiography

D.S.KUSHWAH,NDT SERVICES

NONDESTRUCTIVE TESTING.

AN INTRODUCTION.


WHAT IS NONDESTRUCTIVE TESTING?

NONDESTRUCTIVE TESTING IS THE NAME GIVEN TO SEVERAL TESTING METHODS

COLLECTIVELY.THESE TESTING METHODS HELP US IN DETECTING DEFECTS IN

MATERIALS WITHOUT CAUSING ANY CHANGE IN OR DAMAGE TO THE TESTED MATERIALS.


WHICH ARE THE COMMON NDT METHODS?

THE MOST COMMONLY USEDNDT METHODS ARE:

RADIOGRAPHIC EXAMINATION.ULTRASONIC FLAW DETECTION.

MAGNETIC PARTICLE EXAMINATION.LIQUID PENETRANT EXAMINATION.

EDDY CURRENT EXAMINATION.MAGNETIC FLUX LEAKAGE METHODS.

VISUAL EXAMINATION.ACCOUSTIC EMMISSION.

THERMOGRAPHY


WHAT ARE THE MATERIAL DEFECTS?[1]

ENGINEERING INDUSTRY MAKES USE OF A GREAT VARIETY OF MATERIALS IN

MANUFACTURING USEFUL PRODUCTS NEEDED BY THE SOCIETY.SOME OF THESE PRODUTS,

FOR EXAMPLE,ARE:MACHINE TOOLS.

A RANGE OF MACHINERY FOR MANUFACTURING CONSUMER GOODS.

HEAVY MACHINERY FOR CONSTRUCTION INDUSTRY.



MACHINERY FOR MINING INDUSTRY.

PLANT EQUIPMENTS FOR FERTILIZER,PETROCHEMICALS,OIL REFINING AND CHEMICAL MANUFACTURING INDUSTRIES.

EQUIPMENTS FOR POWER GENERATION.

TRANSPORTAION INDUSTRY : SHIPBUILDING,RAILWAYS, AUTOMOBILES, AVIATION.



IN MAUFACTURING ALL THESE GOODS, THE MANUFACTURING INDUSTRIES MAKE USE OF MANY DIFFERENT MATERIALS. SOME OF THE MOST COMMONLY USED MATERIALS ARE:

WOOD.

METALS:

IRON AND ITS ALLOYS: SUCH AS CARBON STEEL,LOW ALLOY STEELS,HIGH ALLOY STEELS ETC.

NICKEL AND CHROMIUM ALLOYS.

ALUMUNUM AND ALUMINUM ALLOYS CONTAINING MAINLY MAGNESIUM,AND OR TITANIUM.



COPPER AND COPPER ALLOYS CONTAINING OTHER METALS LIKE ZINK, TIN ETC.THESE

ALLOYS ARE KNOWN AS BRASS, BRONZE ETC.

LEAD AND TIN ALLOYS FOR BEARING SURFACES.

CERAMICS AND GLASSES.

PLASTICS.

COMPOSITES.



THE INDUSTRIAL MATERIALS LISTED ABOVE HAVE TO PASS THROUGH A SERIES OF POCESSES BEFORE THEY TAKE THEIR FINAL FORM IN WHICH THEY ARE USABLE .

ALL THESE PROCESSES ARE INTENDED TO GIVE THE MATERIALS THE PROPERTIES WHICH WILL MAKE THEM USABLE EITHER FOR A PARTICULAR APPLICATION , OR FOR A RANGE OF APPLICATIONS.

HOWEVER, ANY MANUFACTURING PROCESS HAS POSSIBILITY OF FAILURES WHICH INTRODUCE UNINTENDED AND UNDESIRABLE CHANGES IN THE INTENDED PROPERTIES. SUCH DEVIATIONS IN THE MATERIAL PROPERTIESARE KNOWN AS FLAWS.



A CATEGORY OF SUCH UNINTENDED AND UNDESRIRABLE PROPERTIES RESULTING FROM PROCESS FAILURES IS KNOWN AS “DISCONTINUITY”.

A DISCONTINUITY IS AN ABRUPT CHANGE IN THE CONTINUITY OF A MATERIAL. IN THE NEXT SLIDE WE WILL DISCUSS THE TYPES OF DISCONTINUITIES ASSOCIATED WITH DIFFERENT MANUFACTURING PROCESSES.



CASTINGS MAY HAVE ENTRAPPED GAS,COMMONLY KNOWN AS BLOWHOLES OR POROSITY.

CASTINGS ALSO HAVE CAVITIES AND SPONGINESS RESULTING FROM SHRINKAGE.

ROLLED METAL SECTIONS HAVE SEAMS,STRINGERS,INCLUSIONS AND CRACKS.

FORGINGS HAVE CRACKS AND LAPS.

PLATES HAVE LAMINATIONS AND SLIVERS.

WELDED JOINDS HAVE INCLUSIONS ,POROSITY AND INCOMPLETE PENETRATION OR FUSION.

COMPOSITES HAVE DEBONDS.

CERAMICS HAVE CRACKS.



EVERY COMPONENT OF A MACHINE OR AN EQUIPMENT OR A MEMBER OF A STRUCTURE IS LOADED AND IS EXPECTED TO WITHSTAND SERVICE STRESSES DURING THE DESIGN LIFETIME OF THE COMPONENT,EQUIPMENT OR STRUCTURE.

THE ABILITY OF SUCH MATERIAL TO WITHSTAND THE SERVICE STRESSES IS ADVERSELY AFFECTED IN THE PRESENCE OF ONE OR MORE DISCONTINUITIES..



THOSE DISCONTINUITIES WHICH RENDER A MATERIAL UNFIT FOR THE INTENDED SERVICE ARE CALLED

‘’ DEFECTS’’. BECAUSE THE DEFECTS CAN CAUSE PREMATURE AND SUDDEN FAILLURE OF A STRESSED COMPONENT, THE MANUFACTURING PROCESSES ARE REFINED TO GIVE AS DEFECT FREE A PRODUCT AS POSSIBLE.SINCE DEFECTS CAN OCCUR EVEN IN A WELL DEVELOPED AND WELL MONITORED MAUFACTURING PROCESS, IT BECOMES NECESSARY TO DETECT THE DEFECTS WITHOUT AFFECTING THE MATERIAL IN ANY MANNER. THIS TASK IS ACCOMPLISHED USING ONE OF THE SEVERAL NONDESTRUCTIVE TESTING METHODS.


NONDESTRUCTIVE TESTING METHODSRADIOGRAPHY.[1]RADIORAPHIC PROCESS.[1]

RADIOGRAPHIC EXAMINATION ENABLES US TO SEE THE DISCONTINUITIES WHICH ARE TOTALLY WITHIN THE EXAMINED ARTICLE. NO OTHER NDT METHOD CAN PRODUCE IMAGES AS EASY TO UNDERSTAND, NOR HAS THE SIMPLICITY OF THE RADIOGRAPHIC TESTING PROCEDURES. THESE TWO FEATURES HAVE MADE THE RADIORAPHIC INSPECTION MOST WIDELY USED NDT METHOD IN INDUSTRY.RADIOGRAHIC EXAMINATION IS BASED ON THE PROPERTIES OF IONIZING RADIATIONS LIKE X RAYS AND GAMMA RAYS .WHEN THESE RADIATIONS PASS THROUGH ANY MATERIAL,THEIR INTENSITY CHANGES [REDUCES] DEPENDING ON THE TYPE OF RADIATION, DENSITY AND ATOMIC NUMBER OF THE MATERIAL, AND THE THICKNESS OF THE MATERIAL IN THEIR PATH. THIS IS THEPHENOMENA OF “ATTENUATION ”.


NONDESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIORAPHIC PROCESS.[2]

THE RADIATIONS, AFTER PASSING THROUGH THE MATERIAL, CARRY THE INFORMATION REGARDING THE PRESENCE OF DISCONTINUITIES IN THE FORM OF CHANGES IN THE INTENSITIES OF THE RADIANTENERGY. SOME DISCONTINUITIES ARE EITHER VOIDS OR MATTER HAVING LESSER DENSITY COMPARED TO THE MATERIAL PATH IN THE DISCONTINUITY FREE AREA. SO THE RADIATION INTENSITIES ARE HIGHER FOR RADIATION WHICH HAS PASSED THROUGH SUCH DISCONTINUITIES .ON THE OTHER HAND ,IF THE DISCONTINUITY HAS HIGHER DENSIY, THE RADIATION PASSING THROUGH SUCH A DISONTINUITY HAS LOWER INTENSITY.


NONDESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIORAPHIC PROCESS.[3]

THIS FIGURE SHOWS HOW THE BEAM OF XRAYSORIGINATING FROM THE FOCAL SPOT OF THE X RAY TUBE HAS UNIFORM INTENSITY BEFORE PASSING THROUGH THE TEST OBJECT, HOW THE INTENSITY OF THE XRAY BEAM CHANGES DEPENDING UPON THE MATERIAL PRESENT IN ITSPATH AND HOW THESE CHANGED INTENSITIES ARE RECORDED BY THE XRAY FILM AS AREAS HAVING DIFFERENT DEGREE OF DARKENING OFTHE PROCESSED XRAY FILM. THE DEGREE OF DARKNESS OF PROCESSED XRAY FILM IS MEASURED IN TERMS OF THE DEGREE OF OPACITY OF THE FILM AND IS CALLED DENSITY.


NONDESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS[4]RADIATION SOURCES.[1]

RADIATIONS FOR NONDESTRUCTIVE TESTING IS OBTAINED FROM A VAREITY OF SOURCES. ALL THE SOURCES USED IN RADIOGRAPHY EMIT ELECTROMAGNETIC RADIATIONS IN THE RANGE OF WAVELENGTHS WHICH HAVE THE ABILITY TO PENETRATE AND PASS THROUGH MATTER. SOME OTHER IMPORTANT PROPERTIES OF THESE RADIATIONS ARE:

[1] THEY ARE INVISBLE.

[2] THEY INTERACT WITH THE MATTER IN SEVERAL DIFFERENT WAYS. ONE OF THESE

INTERACTIONS IONIZES THE MATTER ,HENCE THESE RADIATIONS ARE ALSO KNOWN AS

IONIZING RADIATIONS.

[3] THE INTERACTIONS OF RADIATIONS WITH MATTER CHANGE BOTH THE INTENSITY AND

ENERGY OF THE ORIGINAL RADIATION.


NONDESTRUCTIVE TESTING METHODS-RADIOGRAPHY.RADIOGRAPHIC PROCESSRADIATION SOURCES.[2]

[4] THESE RADIATIONS TRAVEL IN A STRAIGHT LINE.

[5] EXPOSURE TO THESE RADIATIONS IS INJURIOUS TOLIVING CELLS .

[6] THESE RADIATIONS CAUSE THE PHOTOSENSITIVE COATING OF PHOTOGRAHIC FILMS , PLATES ANDPAPER TO BE AFFECTED AS IF THE SAME WERE EXPOSED TO VISIBLE LIGHT, CAUSING THE COATINGS TO BLACKEN AFTER IT IS SUBJECTEDTO FILM DEVELOPING PROCESS.

[7 ] NONE OF THE SENSORY ORGANS CAN DETECT THE PRESENCE OF THESE RADIATIONS.



PENETRATING RADIATIONS FOR RADIOGRAPHY ARE GIVEN OFF BY THE FOLLWING RADIATION SOURCES.

X-RAY MACHINES-LOW ENERGY-60 KV TO 140 KV.X-RAY MACHINES- MEDIUM ENERGY 140 KV TO 350 KV

X-RAY MACHINES MAKE USE OF ULTRA HIGH VACUUM X-RAY TUBE, HIGH VOLTAGE TRANSFORMERS,CONTROL ELECTRONICS, TUBE

HOUSING WITH PROTECTIVE SHIELDING AND PORT FOR DIRECTING AND LIMITING X-RAYS IN THE DESIRED DIRECTION. HIGH VOLTAGE

CABLES ESTABLSH INTERCONNECTION OF ALL THESE COMPONENTS.

HIGH ENERGY X-RAY SOURCES: BETATRONS.

BETATRONS HAVE DOUGHNUT SHAPED ,EVACUATED CIRCULAR PATHS ALONG WHICH ELECTRONS ARE ACCELERATED AND GAIN

ENERGY WITH EACH SUCCESSIVE ORBIT.DEFLECTION TOWARDS AND COLLISON WITH TARGET PRODUCES HIGH ENERGY X-RAYS.



HIGH ENERGY X-RAY SOURCES: BETATRONS.

BETATRONS HAVE DOUGHNUT SHAPED ,EVACUATED CIRCULAR PATHS ALONG WHICH ELECTRONS ARE ACCELERATED AND GAIN

ENERGY WITH EACH SUCCESSIVE ORBIT.DEFLECTION TOWARDS AND COLLISON WITH TARGET PRODUCES HIGH ENERGY X-RAYS.

HIGH ENERGY X-RAY SOURCES: LINEAR ACCELERATORS.

LINEAR ACCELERATORSMAKE USE OF MICROWAVE GUIDES TO ACCELERATE ELECRONS ALONG A LINEAR PATH TO COLLIDE WITH A

TRANSMISSION TYPE TARGET AND PRODUCE HIGH ENERGY X-RAYS.



RADIOACTIVE MATERIALS[ISOTOPES]:IRIDIUM 192,COBALT 60,CESIUM137,SELENIUM 75 .

THESE MATERIALS ARE PRODUCED IN ATOMIC REACTORS.EACH OF THEM PRODUCES ELECTROMAGNETIC RADIATIONS CALLED GAMMA RAYS. EACH SOURCE PRODUCES GAMMA RAYS HAVING CHARACTERESTIC ENERGY OR SEVERAL DISCREET ENERGIES.THESE SOURCES UNDERGO A DECAY PROCESS WHICH CAUSES GRADUAL REDUCTION IN THEIR ACTIVITY. THE PERIOD DURING WHICH THEIR ACTIVITY BECOMES HALF OF INITIAL ACTIVITY,IS KNOWN AS HALF LIFEOF THAT RADIOACTIVE SUBSTANCE.EACH SOURCE ALSO HAS ITS CHARACTERESTIC RADIATION ENERGY OUTPUT PER UNIT OF RADIOVCTIVITY.

THE RADIATIONS FROM THESE SOURCES CANNOT BE EITHER SWITCHED ON OR OFF


NONDESTRUCTIVE TESTING METHODS-RADIOGRAPHY.RADIOGRAPHIC PROCESSRADIATION SOURCES.[7] BETATRON

Betatron is an equipment for generating high energy xrays[1 MeV to 30 MeV]. Massive size and heavy weight notwithstanding, many were built and are still in use throughout the world.


NONDESTRUCTIVE TESTING METHODS-RADIOGRAPHY.RADIOGRAPHIC PROCESSRADIATION SOURCES.[8] LINEAR ACCELERATOR.

Linear accelerator is another type of high energy x-ray generator.This is the latest development and currently most high energy machines are of this type.Linacs use microwves and waveguides to accelerate the electrons to impart them high energy.These machines work to produce x-rays at upto 50MeV,and they are lighter than the betatrons.


NONDESTRUCTIVE TESTINGMETHODS.RADIOGRAPHY.RADIOGRAPHIC PROCESS[4]RADIATION UNITS.

UNITS OF RADIOACTIVITY:

THE ENRGY RADIATED BY THE RADIOACTIVE SUBSTANCE IS THE RESULT OF UNSTABLE STATE OF SOME OF THEATOMS WHICH HAVE A NUCLEUS IN EXCITED STATE DUE TO ITS EXCESS ENERGY AND EXTRA NEUTRON.SUCH ATOMS DISINTEGRATE GIVING OFF EXCESS ENERGY AS GAMMA RAYS,BETA RAYS OR ALPHA PARTICLES.

THE DEGREE OF RADIOACTIVITY PRESENT IN A SUBSTANCE IS MEASURED IN TERMS OF THE NUMBER OF RADIOACTIVE ATOMS DISINTEGRATING EVERY SECOND.THE UNITS OF RADIOACTIVITY ARE CURIE AND BACQUEREL.CURIE: ONE CURIE CORRESPONDS TO 3.7*1010 DISINTEGRATIONS PER SECOND.BACQUEREL: CORRESPONDS TO ONE DISINTEGRATION PER SECOND. Therefore:

ONE CURIE = 3.7*1010 BACQERELS =37 G Bq.

THE QUANTITY OF RADIANT ENERGY IS MEASURED IN TERMS OF THE DEGREE OF IONIZATION PRODUCED IN THE 1 CC VOLUME OF DRY AIR AT STANDARD TEMPERATURE AND PRESSURE.

UNITS OF IONOZING RADIATIONS ARE:ROENTGEN: 1 ROENTGEN OF RADIANT ENERGY PRODUCES 1 E.S.U. OF CHARGE OF EITHER

SIGN IN DRY AIR AT STANDARD TEMPERATURE AND PRESSURE .

SIEVERT: SIEVERT IS THE NEW INTERNATIONAL UNIT.1 SIEVERT IS EQUAL TO 100ROENTGENS.


NON DESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS .DETECTION AND RECORDING OF RADIOGRAPHIC INFORMATION.[1]

THE INFORMATION CONTAINED IN THE RADIATION BEAM IN THE FORM OF CHANGED

INTENSITIES,CAN BE READ BY USING DIFFERENT TYPES OF DETECTION AND RECORDING DEVICES.THESE DEVICES ARE:

RADIOGRAPHIC FILM. [X-RAY FILM]. PHOTOGRAPHIC PAPER

BOTH X-RAY FILMS AND PHOTOGRAPHIC PAPER CONVERT DIFFERENCES IN RADIATION INTENSITIES INTO

PERMANENT IMAGES HAVING DEGREES OF BLACKNING OF PHOTOSENSITIVE COATING IN PROPORTION TO THE

RADIATION INTENSITIES TO WHICH THEY ARE EXPOSED.

FLUORESCENT SCREENS. [FLUOROSCOPY]FLUORESCENT SCREENS CONVERT RADIATION INTENSITIES TO VISIBLE LIGHT.FLUOROSCOPIC IMAGES HAVE LOW LIGHT

INTENSITIES AND NEED ADDITIONAL PROCESSING FOR BETTER READABILITY AND RECORDING OF IMAGES.


NON DESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS .DETECTION AND RECORDING OF RADIOGRAPHIC INFORMATION[2]

IMAGE INTENSIFIERS.IMAGE INTENSIFIERS ARE ELECROTRONIC DEVICES WHICH

CONVERT LOW INTENSITY FLUOROSCOPIC IMAGE INTO ELCTRONIC IMAGE,INTENSIFY IT, AND THEN CONVERT THIS ELECTRONIC IMAGE INTO VISIBLE IMAGE FOR VIEWING ON

VIDEO MONITOR.

CCD CAMERAS.CCD CAMERAS WORK LIKE IMAGE INTENSIFIERS BUT THEY

ARE SOLID STATE DEVICES WHICH ARE LIGHT,COMPACT AND MORE EFFICIENT AS COMPARED TO IMAGE INTENSIFIERS.

AMORPHOUS SILICON FLAT PANELS.FLAT PANELS ARE THE LATEST DEVELOPMENT.THEY

CONVERT X-RAY INTENSITIES DIRECTY INTO VISIBLE IMAGE FOR VIEWING ON A VIDEO MONITOR.


NON DESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS .DETECTION AND RECORDING OF RADIOGRAPHIC INFORMATION[2]

THE RADIOGRAPHIC PROCESS CONSISTS OF PRODUCING SHADOWS OF DETECTABLE FEATURES IN A TEST OBJECT IN THE PLANE OF THE DETECTOR.THE DEPTH INFORMATION IS SUPERIMPOSED TO FORM IMAGES IN THE DETECTOR PLANE. THUS, THE RADIOGRAPH IS THE IMAGE OF THE TEST OBJECT PRODUCED BY RADIATION BEAM WHICH HAS PASSED THROUGH IT AND HAS EXOPSED THE X RAY FILM IN PROPORTION TO THE INTENSITIES IN THE TRANSMITTED BEAM.

THIS PROCESS PRODUCES THE IMAGES OF DISCONTINUITIES IN THE TEST OBJECT, ALL OF THEM IN ONE PLANE,THAT IS, THE PLANE OF THE DETECTOR,WHICH IN THE CASE OF FILM RADIOGRAPHY, IS THE XRAY FILM.

THE IMAGE OF A DISCONTINUITY IS FORMED IN A MANNER SIMILAR TO THE FORMATION OF A SHADOW OF AN OPAQUE OBJECT FORMED BY

VISIBLE LIGHT. DEPENDING ON THE RELATIVE POSITIONS OF THE SOURCE OF RADIATION,THE TEST OBJECT AND THE XRAY FILM

PLANE,THE IMAGE MAY HAVE [1]ENLARGEMENT. [2] DISTORTION OR BOTH.


NON DESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS .IMAGE FORMATION- GEOMETRIC FACTORS.

THESE FIGURES ILLUSTRATE HOW THERADIOGRAPHIC IMAGES FAIL TO DEPICTTHE OBJECT FAITHFULLY:[A] THE SHAPE OF THE OBJECT IN FIG. C ISCORRECTLY IMAGED,BUT WITHMAGNIFICATION.

[B]THE EDGES OF THE IMAGE ARE BLURRED, THIS ISKNOWN AS UNSHARPNESS.

[C]THE EDGES ARE STILL SOMEWHAT BLIRRED, BUT THE UNSHARPNESS IS REDUCEDDUE TO INCREASED SOURCE TO FILM DISTANCE.

[E] AND[F] THE IMAGE IS DISTORTED AND THE SHAPE OF THE IMAGE IS ELLIPTICAL,NOT CIRCULAR, WHICH IS THE TRUESHAPE OF THE OBJECT.THIS IS KNOWN ASDISTORTION.

FROM THE FIGURE WE CAN CONCLUDE THAT:

UNSHARPNESS CAN BE REDUCED BY[a] REDUCING THE SOURCE SIZE.

[b] REDUCING THE OBJECT TO IMAGING PLANE DISTANCE [c] INCREASING THE SOURCE TO FILM DISTANCE.


NON DESTRUCTIVE TESTING METHODSRADIOGRAPHY.RADIOGRAPHIC PROCESS .X-RAY FILMS.

X RAY FILMS HAVE POLYSTER BASE WITH BLUISH TINT. THIS BASE IS COATED WITHPHOTOSENSITIVE EMULSION.THE PROCESS OF COATING CONSISTS OF MANYTREATMENTS TO GIVE THE FINISHED PRODUCT PROPERTIES LIKE RESISTENCE TO DAMAGE THROUGH NORMAL HANDLING ,ADHERENCE OF EMULSION TO THE BASE WHEN BEINGPROCESSED IN FILM DEVELOPING CHEMICALS AND PRODUCE IMAGES OF DESIRED QUALITY.



INHERENT UNSHARPNESS :THE FILM EMULSION CONSISTS OF GRAINS OF SILVER HALIDE WHICH ,WHEN EXPOSED TO RADIATIONS, FORMS LATENT IMAGE. THE SILVER HALIDE GRAINS FORMING THIS LATENT IMAGE ARE REDUCED TO METALLIC SILVER BY THE CHEMICAL PROCESS OF DEVELOPING AND FIXING.SINCE THESE SPECKS OF SILVER HAVE DISCREET SIZE,UNDER MAGNIFICATION YOU CAN SEE THAT THE APPARENTLY DARK AREA OF EXPOSED EMULSION IS ACTUALLY SEVERAL ISLANDS OF SILVER IN TRANSPRENT AREAS OF THE FILM BASE,FROM WHICH UNAFFECTED SILVER HALIDE IS REMOVED. THUS THE IMAGE HAS GRAININESS GIVING RISE TO UNSHARPNESS.THIS IS THE CHARACTERISTIC OF X-RAY FILMS AND IS CALLED “INHERENTUNSHARPNESS.”



GEOMETRICAL UNSHARPNESS:

WE HAVE SEEN THE FIGURES WHICH ILLUSTRATED THE EFFECT OF THE SIZE OF RADIATION SOURCE, SOURCE TO FILM DISTANCE AND THE OBJECT TO FILMDISTANCE ON THE DEFINITION OF THE EDGES OF THE IMAGE OF AN OBJECT.

A COMBINATION OF THESE THREE VARIABLES PRODUCES A CERTAINAMOUNT OF FUZZINES IN THE EDGES OF THE IMAGE.THIS IS KNOWN AS UNSHARPNESS, AND THE UNSHARPNESS RESULTING FROM A COMBINATION OFTHESE PARAMETERS IS CALLED “GEOMETRICAL UNSHARPNESS.” THIS IS DENOTED AS “Ug”.

IT CAN BE SEEN THAT BY CHOOSING A VERY SMALL RADIATION SOURCE, ANDPLACING IT AS FAR AWAY FROM THE OBJECT AS PRACICAL, WE CAN REDUCE

THE GEOMETRICAL UNSHARPNESS VALUE TO THE EXTENT THAT NO IMAGE UNSHARPNESS IS DETECTED BY THE EYES OF THE OBSERVER. HOWEVER, IN PRACTICE ,THE UNSHARPNESS CANNOT BE REDUCED BELOW A CERTAIN MINIMUM VALUE.THIS IS DUE TO THE FACT,THAT A CERTAINAMOUNT OF IMAGE UNSHARPNESS IS INHERENT PROPERTY OF THE XRAY FILM . IT IS CALLED ‘INHERENT UNSHARPNESS AND DENOTED AS “ Ui ” .


NONDESTRUCTIVE TESTING METHODS:RADIOGRAPHY.CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS:[2]CHARACTERESTICS OF XRAY FILM.

FROM THE NATURE OF IMAGE UNSHARPNESS ,WE CAN SEE THAT THE DETECTION OF THIN DISCONTINUITIES IS LIMITED BY THE INHERENT UNSHARPNESS OF THE XRAY FILM.WITH DECREASING INHERENT UNSHARPNESS THE FILM SPEED DECREASES,THAT IS,THE FILMS NEED HIGHER RADIATION DOSE TO PRODUCE OPTIMUM IMAGE QUALITY.

XRAY FILMS ARE AVAILABLE IN A RANGE OF FILM SPEEDS WITH CORRESPONDING

IMAGE SHARPNESS . [DEFINITION OF THIN FLAWS].

A FILM COOSEN FOR A PARTICULAR INSPECTION TASK IS USUALLY A COMPROMISE BETWEEN THE SPEED OF THE FILM [WHICH IS IMPORTANT FOR THE ECONOMY OF INSPECTION ] AND THE SHARPNESS OF THE IMAGE WHICH CAN BE PRODUCED,DUE TO THE INHERENT UNSHARPNESS. INHERENT UNSHARPNESS IS ALSO QUALITATIVELY EXPRESSED AS FILM GRAININESS.THE IMAGE IN A PROCESSED X RAY FILM CONSISTS OF DISTINCT ISLANDS OF OPAQUE METALLIC SILVER AGAINST THE TRANSPARENT BACKGROUND PROVIDE BY THE POLYSTER BASE.THESE DISCONTINUOUS ELEMENTS FORMING THE IMAGE GIVE RISE TO GRAININESS, AND CONSEQUENT UNSHARPNESS..


SO THE FIRST ELEMENT IN CONTROLLING THE QUALITY OF RADIOGRAPHIC IMAGE IS THE :

INHERENT UNSHARPNESS OF THE XRAY FILMS

THE NEXT IMPORTANT CHARACTERESTIC WHICH INFLUENCES THE RADIOGRAPHIC QUALITY IS:

FILM CONTRAST.

TO UNDERSTAND THE CONCEPT OF FILM CONTRAST ONE MUST BE FAMILIAR WITH THE TERM FILM DENSITY.

FILM DENSITY IS THE MEASURE OF THE OPACITY OF THE PROCESSED XRAY FILMS. AN XRAY FILM AFTER BEING EXPOSED TO RADIATIONS, AND AFTER BEING PROCESSED IN FILM

PROCESSING CHEMICALS,IS KNOWN AS A RADIOGRAPH.

A RADIOGRAPH HAS OPAQUE ISLANDS OF METALLIC SILVER ON A TRANSPARENT BACKGROUND OF POLYESTER BASE. WHEN WE VIEW THIS RADIOGRAPH BY HOLDING IT

AGAINST A SOURCE OF LIGHT, ONLY A PART OF THE INCIDENT LIGHT PASSES THROUGH THE FILM. GREATER THE AMOUNT OF METALLIC SILVER ON THE RADIOGRAPH, LESS AND LESS

LIGHT IS TRANSMITTED.

THAT IS ,THE RADIOGRAPH IS MORE AND MORE OPAQUE. THIS DEGREE OF OPACITY IS EXPRESSED AS DENSITY OF A RADIOGRAPH.




RADIOGRAPHIC DENSITY IS DEFINED AS:

DENSITY= log10INTENSITY OF LIGHT INCIDENT ON THE RADIOGRAPH

INTENSITY OF LIGHT TRANSMITTED THROUGH THE RADIOGRAPH

THUS, FOR I0 / It RATIOS OF DIFFERENT VALUES:

RATIO LOG RATIO[DENSITY] REMARK.1. 0. 100% light is transmitted. Density is 0.10. 1. 10% light is transmitted. Density is 1.100. 2. 1% light is transmitted. Density is 2.1000. 3. 0.1% light is transmitted. Density is 3.10000. 4. 0.01% light is transmitted. Density is 4.


NONDESTRUCTIVE TESTING METHODS:RADIOGRAPHY.CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS:[5]CHARACTERESTICS OF XRAY FILM

HAVING FAMILIARIZED OURSELVES WITH THE CONCEPT OF DENSITY ,THE NEXT STEP IS TO UNDERSTAND THE RELATIONSHIP BETWEEN THE RADIATION EXPOSURE RECEIVED BY THE FILM AND THE CORRESPONDING DENSITY IN A RADIOGRAPH. THIS RELATIONSHIP IS GRAPHICALLY REPRESENTED BY PLOTTING THE EXPOSURE VERSUS DENSITY RELATION ON SEMILOG GRAPH PAPER. THE VALUES OF EXPOSURE ARE PLOTTED ON THE X-AXIS ,AS LOGRITHM OF RELATIVE EXPOSURES. LOG SCALE OFFERS THE ADVANTAGE OF BEING ABLE TO ACCOMMODATE A VERY LARGE RANGE OF EXPOSURE VALUES ON THIS AXIS. THE RATIO BETWEEN THE VALUES OF SMALLEST EXPOSURE AND THE LARGEST EXPOSURE, BOTH REPRESENTED ON THIS AXIS COULD BE AS LARGE AS 1:100000 .THIS WOULD NOT BE POSSIBLE ON A LINEAR SCALE.

DENSITY IS PLOTTED ON Y –AXIS , THE VALUES ARE LINEAR . USUALLY UPTO 4.

THIS GRAPHICAL REPRESENTATIO OF EXPOSURE VS.DENSITY RELATION IS CALLED THE CHARACTERESTIC CURVE OF THE X-RAY FILM. THIS CURVE IS DRAWN FOR EACH TYPE OF FILM WITH SPECIFIED PROCESSING CONDITIONS AS ESSENTIAL PART OF THE PARAMETERS OF CHARACTERESTIC CURVE .THE RADIATION SOURCE OR THE RADIATION ENERGY DO NOT INFLUENCE THE SHAPE OF THE CHARACTERESTIC CURVE.

THE CHARACTERESTIC CURVE PROVIDES US WITH QUANTITATIVE MEASUREMENT OF SOME IMPORTANT PROPERTIES OF X-RAY FILM.


NONDESTRUCTIVE TESTING METHODS.CONTOLLING QUALITY OF RADIOGRAPHIC PROCESS [6]CHARACTERESTICS OF XRAY FILM

THE FIGURE SHOWS A TYPICAL CHACTERESTIC CURVE OF AN XRAY FILM.IT IS ALSO KNOWN AS SENSITOMETRIC CURVE.ON X AXIS WE HAVE LOG EXPOSURE,THE VALUES CORRESPONDING TO ARBITRARILY CHOSEN UNIT EXPOSURE[ 0 ON THE X-AXIS] AND THE MULTIPLES OF THIS UNIT EXPOSURE UPTO 1000 TIMES OF THE UNIT EXPOSURE{ 3 ON THE X-AXIS] ARE PLOTTED ON THIS AXIS

WE SEE THAT UPTO A DENSITY OF 1.0-1.5 THE CHNGE IN DENSITY IS NOT PROPORTIONAL TO THE EXPOSURE.NEAR PROPORTIONAL INCREASE IN DENSITY OCCURS BEYOND DENSITY 1.5.THE CURVE FROM THIS POINT ONWARDS REPRESENTS NEARLY LINEAR CHANGE IN DENSITY WITH INCREASING EXPOSURE..IF WE EXTEND THE STRAIGHT LINE PORTION OF THIS CURVE TO INTERCEPT X-AXIS, THE ANGLE IT FORMS WITH THE X-AXIS DETERMINES HOW MUCH THE DENSITY WILL CAHNGE FOR A GIVEN EXPOSURE INTERVAL.


NONDESTRUCTIVE TESTING METHODS:RADIOGRAPHY.CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS:[7]CHARACTERESTICS OF XRAY FILM

IT CAN BE VISUALIZED THAT FOR A GIVEN CHANGE IN THE THICNESS OF THE SPECIMEN,THERE WILL BE A CERTAIN CHANGE IN THE EXPOSURE RECEIVED BY THE FILM.THIS DIFFERENCE IN EXPOSURE IS CALLED THE EXPOSURE INTERVAL.HIGHER THE DENSITY DIFFERENCE CORRESPONDING TO A PARTICULAR VALUE OF THE EXPOSURE INTERVAL,GREATER THE ABILITY OF THE RADIOGRAPH TO MAKE SMALL CHANGE IN THICKNESS VISIBLE. .THIS MEANS A GREATER SESITIVITY OF INSPECTION.

THIS PROPERTY OF XRAY FILM IS CALLED FILM COTRAST AND IS EXPRESSED AS GRADIENT OF THE CURVE AT A PARTICULAR DENSITY.THE NUMERICAL VALUE OF THE GRADIENT, AS CAN BE SEEN FROM THE FIGURE WILL BE EQUAL TO TRGNIOETRIC RATIO TAN FOR THE ANGLE FORMED BY THE TANGENT AT ANY POINT OF THE CURVE,AND X-AXIS.


NONDESTRUCTIVE TESTING METHODS.CONTROLLING QUALITY OF RADIOGRAPHIC PROCESS.[7]REVIEW OF PREVIOUS THREE SLIDES.

WE NOW KNOW THAT THE RADIOGRAPHIC IMAGE OF A DISCONTINUITY WILL BE PROJECTED ON THE FILM WITH THE GREATEST FIDELITY IF:

MAGNIFICATION AND DISTORTION ARE CONTROLLED THROUGH CONTROLLING THE GEOMETRICAL PARAMETERS OF HE EXPOSURE AS UNDER:[a] THE SOURCE POSITIONED ON THE LINE PERPENDICULAR

TO THE FILM PLANE.[b] KEEPING THE FILM IN AS CLOSE CONTACT WITH

THE OBJECT AS POSSIBLE.[C] CHOOSING THE SOURCE TO FILM DISTANCE SO THAT THE

GEOMETRICAL UNSHARPNESS IS LESS THAN THEINHERENT UNSHARPNESS OF THE FILM.

[D] EXPOSING THE FILM TO A DEGREE THAT WILL GIVE RADIOGRAPHIC DENSITY IN THE REGION OF SENSITOMETRIC CURVE WHICH HAS HIGH GRADIENT,AND HENCE

GREATEST CONTRAST


NONDESTRUCTIVE TESTING METHODSCONTROLLING THE QUALITY OF RADIORAPHIC ROCESS.[8]IMAGE QUALITY INDICATORS.

AN INSPECTOR EVALUATING THE RADIOGRAPH HAS TO KNOW WHETHER THE RADIOGRAPHIC TECHNIQUE HAS BEEN CORRECTLY APPLIED TO PRODUCE THE RADIOGRAPHS CAPABLE OF SHOWING THE FLAWS OF INTEREST FOR THAT PARTICULAR APPLICATION. TO PROVIDE AN OBJECTIVE ASSESMENT OF THECORRECTNESS OF THE TECHNIQUE,THE IMAGE QUALITY INDICATORS ARE USED.ASTM AND ASME HAVE TWO TYPES OF IMAGE QUALITY INDICATORS.

[1] PLAQUE TYPE.[2] WIRE TYPE.

PLAQUE TYPE IMAGE QUALITY INDICATORS [IQI IN SHORT] ARE RECTANGULAR SHIMS OF METAL PRODUCED IN A RANGE OF THICKNESSES ,HAVING THREE DRILLED HOLES,EACH HAVING DIAMETRE EQUAL TO 1,2 AND FOUR TIMES THE THICKNESS OF THE SHIM.THE THICNESS OF A SHIM IS CHOOSE TO BE 2% OF THE OBJECT THICKNESS UNDER EXAMINATION OR AS CLOSE TO 2% AS AVILABLE IN THE STANDARD THICNESSES PROVIDED IN THE IQI SPEC. THIS IQI IS PLACED ON THE ONJECT ON THE SOURCE SIDE,WHEN THE EXPOSURE IS MADE.

THE VISIBILITY OF THIS SHIM AND THAT OF THE HOLES IN THE SHIM IN THE RADIOGRAPH PROVDES THE MEASURE OF THE SUCCESS OF RADIOGRAPHIC TECHNIQUE.FOR EXAMPLE,IF THE IQI OUTLINE,ITS BODY AND 4T AND 2T HOLES ARE CLEARLY VISIBLE, THEN THE RADIOGRAPH IS SAID TO HAVE ATTAINED THE QUALITY LEVEL 2-2T.[ AN IQI HAVING THICNESS EQUAL TO 2% OF THE OBJECT THICKNESS AND THE HOLE HAVING

DIAMETER EQUAL TO 2 TIMES THE IQI THICNESS ARE VISIBLE .]


NONDESTRUCTIVE TESTING METHODSCONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS[9]IMAGE QUALITY INDICATORS.

ty

THE FIGURE SHOWS THE DESIGN OF IMAGE QUALITY INDICATOR CONFORMING TO ASTM, WHICH IS ADOPTED BY ASME B.&P.V.CODE.THE THICKNESS STARTS AT .0005” AND INCREASES IN STEPS OF ).005 “.FROM ).0.060”TO 0.100”,IQI’S HAVE 2.25”X1.0”SIZE.FOR HIGHER THICKESSES, IQI THICNESSFROM 0.060’TO 0.160”,THE IQI’S ÁRE MADE AS SHOWN IN LOWERMOST FIGURE.THIS RANGE OF IQI’S POROVIDE 2% THICKNESS FOR MATERIAL THICNESS FROM )0.25” TO 8 ‘’.IQI ACCORDING TO FIG1 &2 CARRY IDENTIFICATION IN LEAD FIGURES SHOWINGTHE THICKNESS IN NEAREST THOUSANDTH OF AN INCH.THE CICULAR IQI DOES NOT HAVE IDENTIFICATION ,BUT THE THICKNESS CAN BE FOUND FROM THE DIMENSIONS OF THE DIAMETER WHICH IS 4 TIMES THE THICKNESS..


CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS[10]WIRE TYPE IQI.-1


CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS[11]WIRE TYPE IQI.-2


CONTROLLING THE RADIOGRAPHIC PROCESSWIRE TYPE IQI.-3


CONTROLLING RADIOGRAPHIC PROCESS:[12]Wire type IQI-4


CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS[13].WIRE TYPE IQI-5

WIRE TYE IMAGE QUALITY INDICATORS HAVE PARALLEL WIRES ENCAPSULED IN CLEAR VINYL PLASTIC.ASTM HAS 6 WIRE,WITH THE THICKEST WIRE TO THE LEFT,AND WIRE DIAMETER DECREASING TOWARDS RIGHT.IQI ACCORDING TODIN STANDARD HAVE SEVEN WIRES WUTH THINNEST WIRE AT RIGHT AND DIAMETER DECREASING TOWARDS LEFT.BOTH TYPES HAVE THE INFORMATIONABOUT WIRE MATERIAL.ASTM IQI SHOWS THE DIAMETER OF THE THICKEST WIRE,AND DIN IQI SHOWS THE NUMBERS ALLOTED TO THES WIRES AS PER ISO SYSTEM. THE WIRE IQI’S OFFER THE FOLLOWING ADVANTAGES OVER THE PLAQUE TYPE IQI’S:

THE DIAMETER OF THE THINNEST WIRE VISBLE ENABLES US TO COMPUTE THE NUMERICAL VALUE OF THE RADIOGRAPHIC SENSITIVITY.THIS VALUE ACCOUNTS BOTH FOR RADIOGRAPHIC CONTRAST AND DEFINITION OR RESOLUTION.

PLAQUE TYPE IQI’S ARE GENERALLY PLACED ON THE PARENT PLATE WHEN INSPECTING WELDS.WIRE TYPE IQI’S CAN BE PLACED ACROSS THE WELDS AND HENCE THEY MONITOR SENSITIVITY ON THE WELDING ITSELF.


NONDESTRUCTIVE TESTING METHODSCONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS [14] [14]FILM PROCESSING.

INHERENT UNSHARPNESS OF THE FILM AND FILM CONTRAST ARE THE VALUES DEPENDENT UPON THE FILM PROCESSING TECHNIQUE ALSO.THE EXPECTED RESULTS OF RADIOGRAPHIC QUALITY WILL NOT BE ATTAINED IF THE PROCESSING OF EXPOSED FILMS IS NON STANDARD.

.A STANDARDIZED DEVELOPING PROCESS REQUIRES THAT:

THE STRENGTH [CONCENTRATION] OF CHEMICALS WHICH CONVERT EXPOSED GRAINS TO METALLIC SILVER IS WITHIN A NARROW RANGE.

THE PROCESS OF DEVELOPING IS CARRIED OUT AT THE SOLUTION TEMPERATURE WITHIN A RECOMMENDED RANGE OF TEMPERATURE.

THE DEVELOPING TIME IS ADJUSTED FOR THE DEVELOPING TEMPERATURE AS RECOMMENDED BY THE FILM MANUFACTURER. DEPARTURE FROM STANDARDIZED DEVELOPING PROCESS RESULTS INTO POOR QUALITY RADIOGRAPHS.

WEAK DEVELOPING SOLUTION AND/OR INSUFFICIENT DEVELOPING TIMEAND /OR TOO LOW A DEVELOPING TEMPERATURE RESULTS INTO RADIOGRAPHS HAVING LESS THAN REQUIRED DENSITY AND LOW CONTRAST.SUCH RADIOGRAPHS LACK THE REQUIRED PENETRAMETER VISIBILITY.


CONTROLLING THE QUALITY OF RADIOGRAPHIC PROCESS.THE CAUSES FOR POOR RADIOGRAPHIC QUALITY.[1]

THE EFFECTS OF VARIATIONS IN RADIATION EXPOSURE:

AN INCORRECTLY EXPOSED X-RAY FILM WILL BE EITHER OVEREXPOSED OR UNDEREXPOSED.BOTH CAUSE POOR RADIOGRAPHIC QUALITY.

AN UNDEREXPOSED FILM WILL FAIL TO ATTAIN THE DENSITY AT WHICH THE RADIOGRAPH WILL HAVE THE BEST SENSITIVITY.SUCH RADIOGRAPH WILL HAVE POOR VISIBILITY OF DETAIL DUE TO LOW CONTRAST.

IF AN ATTEMPT IS MADE TO INCREASE THE DENSITY BY IBCREASING THE DEVELOPMENT TIME,THERE WILL BE SOME INCREASE IN DENSITY, BUT THE CONTRAST WILL CONTINUE TO BE POOR AND THE RADIOGRAPH WILL FAIL TO MEET THE REQUIRED STANDARDS.

AN OVEREXPOSED FILM MAY HAVE SO HIGH THE DENSITY, THAT EVEN A VERY POWERFUL SOURCE OF LIGHT MAY FAILTO MAKE ANY DETAIL VISIBLE.

IF AN ATTEMPT IS MADE TO CONTROL DENSITY EITHER BY DILUTING THE DEVELOPER,OR BY COOLING THE DEVELOPING SOLUTION OR BY REDUCING THE DEVELOPMENT TIME,IT MAY BE POSSIBLE TO RECORD CORRECT DENSITY BUT THE CONTRAST IN EVERY CASE WILL BE TOO POOR TO SHOW ANY WORTHWHILE DETAIL.


CONTROLLINGTHE QUALITY OF RADIOGRAPHIC PROCESS.CAUSE FOR POOR RADIOGRAPHIC QUALITY.[4]

INCCORRECT DARK ROOM PACTICES CAUSING POOR RADIOGRAPHIC QUALITY.WHEN THE FILM HANGERS ARE REMOVED FROM THE DEVELOPER AFTER

DEVELOPING THEY SHOULD NEVER BE EXAMINED IN AIR FOR ANY REASON AND SHOULD BE IMMERSED IN THE STOP BATH AFTER A VERY BRIEF DRAINING.IF

THE HANGERS ARE HELD IN AIR TO ALLOW COMPLETE DRAINING OF DEVELOPER,THE PATH OF THE DEVELOPER FLOW ON THE FILM WILL DEVELOP

DIFFERENT DENSITY ,GIVING RISE TO STREAKS.FILMS MUST BE HANDLED GENTLY,AVOIDING EXCESS PRESSURE,

BENDING,RUBBING AGAINST ANY SURFACE AND PERMITTING MINIMUM CONTACT BETWEEN THE FINGERS AND THE FILM.

ALL DARKROOM SURFACES MUST BE CLEAN AND DRY.THE HANGERS USED FORMOUNTING THE FILMS FOR DEVELOPING SHOULD HAVE ABSOLUTELY NO TRACE OF CHEMICALS OR WATER FROM THE PREVIOUS USE.FAILURES TO TAKE THESE PRECAUTIONS CAN COMPLETELY RUIN THE RESULTS AND WASTE THE EFFORTS

PUT IN EXPOSING THE RADIOGRAPH ON THE JOB.


RADIOGRAPHIC EXAMINATION.INTERPRETATION OF RADIOGRAPHS.[1]

THE RDIOGRAPHIC EXAMINATION IS EFFECTIVE WHEN:[a] THE RADIOGRAPHS ARE PRODUCED BY APPLYING THE TECHNIQUE CORRECTLY

,SO THAT THE RADIOGRAPHS HAVE THE REQUIRED DENSITY,IMAGE SHARPNESS,RADIOGRAPHIC CONTRAST AND FREEDOM FROM ARTIFACTS.

[IMAGES FROM FAULTY RADIOGRPHIC PROCESSING OF FILMS]

[b] WHEN THE RADIOGRAPHS ARE EVALUATED BY A PERSON TRAINED,QUALIFIED AND CERTIFIED TO CARRY OUT SUCH EVALUATION.

BASICS OF FILM INTERPRETATION

THE RADIOGRAPH SHOULD BE EXAMINED IN A ROOM HAVING SUBDUED LIGHTING WHICH DOES NOT DIRECTLY FALL ON THE FILM VIEWER SURFACE.THERE

SHOULD NOT BE ANY SHADOWS FALLING ON THIS SURFACE.



THE FILM VIEWER MUST HAVE A SOURCE OF LIGHT STRONGENOUGH TO PERMIT COMFORTABLE VIEWING OF RADIOGRPHS HAVING DENSITY

UPTO 3.5.THE LIGHT INTENSITY ON THE SURFACE OF THE VIEWER MUST BE REASONABLY

UNIFORM.THE VIEWER SHALL HAVE EFFECTIVE ARRANGEMENT TO REMOVE HEAT AND KEEP THE VIEWNG SURFACE REASONABLY COOL.

THE RADIOGRAPH SHALL FIRST BE EXAMINED IN THE LIGHT REFLECTED FROM THR SURFACE OF THE FILM,TO SEE IF THE SURFACE IS CLEAN,HAS NO

SCRATCHES,AND THE WORKMANSHIP IS GOOD.THEN THE RADIOGRAPH SHOULD BE EXAMINED IN THE TRANSMITTED LIGHT.THE LIGHT INTENSITY OF THE ILLUMINATOR SHOULD ABE ADJUSTED SO THAT THE IQI

IMAGE HAS THE BEST VISIBILITY.THE RADIOGRAPHIC DENSITY IN THE AREA OF INTEREST SHALL BE ASSESED

USING EITHER DENSITY COMPARISON STRIP OR DENSITOMETER.THE VARIATION OF DENSITY WITHIN THE AREA OF INTEREST SHALL BE NOTED AND MAX. AND MIN.

DENSITIES RECORDED.



A person entrusted with the evaluation of radiographs:Must have understanding of radiographic technique, types of artifacts likely to exist as confusing images or masking true indications.Must have understanding of the manufacturing process, the types and probable locations of flaws, nature of flaws and their radiographic appearance.Must have familiarity with the properties of common engineering materials and the changes brought about by the nature of processing to which they are subjected.A clear understanding of the applicable specification or standard to be followed in accepting or rejecting the flaws.In most cases the acceptance standard is an important part of the contract between the buyer and the suppliers. In such cases it is prudent for the interpreter to follow the standard stipulations diligently and not allow his judgment to be influenced by extraneous factors.


NONDESTRUCTIVE TESTING.

THANK YOU D.S.KUSHWAH, NDT SERVICES.

.

An Introduction to Radiography

Documents

Transcript of An Introduction to Radiography