Research Article Ultrasonic Flaw Detection for Quality

Research ArticleUltrasonic Flaw Detection for Quality Assessment ofExplosively Clad Plates

BogumiB Wronka

Faculty of Civil Engineering Mechanics and Petrochemistry Institute of Mechanical EngineeringWarsaw University of Technology ul Łukasiewicza 17 09-400 Płock Poland

Correspondence should be addressed to Bogumił Wronka wronkabpwplockpl

Received 23 May 2013 Revised 29 December 2013 Accepted 2 January 2014 Published 10 March 2014

Academic Editor Markku Leskela

Copyright copy 2014 Bogumił Wronka This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The aim of this work was to study more thoroughly all problems relating to the evaluation of material defects connected with platequality before and after explosive cladding During testing great attention was paid tomaterial defects in plates the reasons for theirappearance and possibility of detecting them by means of ultrasonic technique It was most important to find out which defectswere especially dangerous The results of ultrasonic testing that relate to the quality of initial steel plates are described Modelleddefects of various sizes are ultrasonically tested and analysed The properties of explosive welded joints and cases of cracks in cladplates are tested All these data can be helpful in the context of working out criteria relating to the selection of initial plates forcladding

1 Introduction

Steel plates with explosive cladding are used all over theworldbecause of their special properties The cladding processcauses the significant speed at which large areas can bebonded with the cleanness of weld Welded plates need to behigh quality particularly in safety-critical applications such asin the power petrochemical and electrotechnical industries

Formed clad plates may have material defects whichmay be permissible or nonpermissible depending on theapplication The quality of plates due to their existing defectscan be evaluated well by means of ultrasonic testing Figure 1shows that the final quality of clad plate depends on theexplosive welding process and the quality of initial metalplates

Details about the explosive welding process and thequality inspection of plates are given in [1ndash4] The typicalcourse of welding is shown in Figure 2 Two successive wavestages of loading and unloading of the both plates occurduring the forming of the wavy joint The normal andtangential forces which form the wavy joint surface act in thecollision area In the backing metal the zone of elastic andplastic strain is 975mm thick and depends on the weldingparameters [3] Material strained by the explosive loading

shows greater strain hardening than rolled material at thesame value of strain [2] The behaviour of materials underconditions of dynamic loading is also described in otherpublished papers [5ndash7] Close to the joint surface at thelocation of pearlite fields martensite is sometimes formedA little bit farther from the joint surface at a temperaturebelow 773K and at a pressure above 13GPa iron undergoesthe phase change 120572 999448999471 120576 Such a phase change may appear insteel as well as in iron

All this leads to strain hardening of the joint areaThe effect of the loading stage is the formed wavy jointstrain hardening and internal stresses The unloading stagedevelops in the joint area possible material discontinuitiesfrom the foregoing stage It sometimes happens that the steelplate cracks during the explosive cladding This situation isoften aggravated by poor quality of initial plates used forcladding

The typical defects occurring in the initial thick steelplates with respect to the welding process are consideredDuring explosive loading macro- and microcracks delam-inations and lappings are especially dangerous Under theinfluence of an impulse shock wave these defects cause platedamage during the welding process

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2014 Article ID 171279 8 pageshttpdxdoiorg1011552014171279

2 Advances in Materials Science and Engineering

Ultrasonic testing

Two initial metal platesfor cladding

Explosivewelding

Cladding

and backing metal joined by welding Clade plate

Figure 1 Ultrasonic testing used for initial metal plates beforecladding and clad plate after explosive welding

Explosive

Base metal

Cladding plate

Wavy joint surface Jet

Claddingmetal

Backingmetal

Vd

Vp120573

VC

C

120582

Anvil

Figure 2 The course of the explosive welding process 119881119901 is theflyer plate velocity 119862 is the collision point 119881119862 is the collision pointvelocity 119881119889 is the detonation velocity 120573 is the collision angle and 120582is the joint wavelength

Fast cooling of thick plates within the range of tempera-tures 473ndash293Kmakes it difficult for hydrogen to be expelledfrom steel by diffusion High hydrogen pressure increasesthe size of existing cracks and causes snowflakes to appearalong the plate fibres This phenomenon lowers the plasticand strength properties of material across its fibres Whenthe temperature is too high and the heating time is extendedoxygen permeates from the semifinished steel surface to thegrain boundaries and a network of hot cracks appears

The band arrangement of these inclusions and lap slagshas a significant influence on the anisotropy and mechanicalproperties of steel Insufficient or uneven heating of billetsand improper plastic working cause lapping with visible platelayers Lap blowholes draw holes and nonmetallic inclusionsare the reasons for plate delaminations

The ultrasonic technique takes into account differenttypes of material defects The following types of materialdefects can be discriminated point elongated large andmultiple [8] The type of defect is determined on the basis ofthemaximum echo height of the indication from a defect thedirectional dependence of the echo amplitude and the staticand dynamic envelope of the echo height indication [9 10]The example of the point defect is shown in (Figure 3(a))Theprinciples of such testing for plate inspection are presented inthe literature [11ndash13]

1 2

36

4

5

(a)

12

3

4

5

4

A

A

A1

A1

(b)

Applied criterion

Dimensions

2c1

2c2

a

2a1

2a2

s

s le a1 + a2

a = 2a1 + a2 + s

2c = 2c1

(c)

Figure 3 The ultrasonic echo responses of the point defect (a)1 amplitude 2 A scan (static envelope) 3 range 4 variation ofpeak signal amplitude (dynamic envelope) 5 probe position and 6reflector beam axis tip location technique (b) 1 and 3 echoes 119860 and1198601 at maximum heights 2 variation of peak signal amplitude 4 Ascan and 5 echoes 119860 and 1198601 will be the first to appear when probeis moved backward and forward the dimensions of substitute crack(c)

The assessment of defect size withmanual testing is basedon the maximum echo height techniques (DGS and DAC)and probe movement sizing techniques [8] (Figure 3(b)) Ifcracks lie close to each other (Figure 3(c)) one establishes thesize of a substitute crack [14]

The later contents of this paper refer to more difficult todetect small defects For a small reflector the proportionalityof the echo height indication ℎ119903 and the acoustic pressure 119901 isgenerally known for an equivalent defect that is flat defectnormal to the ultrasonic beam These and other acousticparameters such as the initial acoustic pressure 1199010 the flatreflector surface area 119878119903 with diameter 119889 the transducersurface area 119878119905 the wavelength 120582 and the distance 119897 give thefollowing [11]

ℎ119903 sim 119901 = 1199010

119878119903119878119905

12058221198972 (1)

For the assessment of real defects their experimental shapefactors are needed

The knowledge about the relationship between crack sizeand object load is given by the fracture mechanics [15]

Advances in Materials Science and Engineering 3

2c

2b

120590

120590

120590max

(a)

2b

c

120590

120590

120590max

(b)

Figure 4 Maximum stress distribution 120590max in a steel plate with an internal crack (a) and an external crack (b) caused by stresses 120590

The stress distribution in a modelled plate with an ellipticmicrocrack of dimensions 119887 119888 and a radius of curvature 120588 atthe ends of the major axis were considered (Figure 4) Thestress-concentration factor 120572 according to Inglisrsquos suggestion[14 16] is as follows

120572 =

120590max120590

= 1 +

2119888

119887

= 1 + 2(

119888

120588

)

12

(2)

The factor120572 isminimised for a circle (119888 = 119887) and increasesfor a flat ellipse (119888 ≫ 119887) Its greatest values occur for naturalmicrocracks when the radius value 120588 reaches the interatomicdistance 119886 In welded conditions spherical point defects areless harmful

The typical defects occur in material before cladding aswell as in clad products An abnormal course of the explosivewelding process is able to create subsequent defects in thespecifically formed joints

In this paper there was carried out a model spatialvisualization of the typical defects surfaces with the purposeof attaining their better detectability and usefulness of ultra-sonic technology

2 Results

21 The Modelling of Small Material Defects The criteriawhich admit an initial plate for cladding should be basedon the fracture mechanics Moreover it is essential to knowthe loading and unloading stages of the plates during theexplosive cladding as well as the types and sizes of defectsTherefore the results of ultrasonic testing ofmodelled defectsof various types and sizes were analyzed The results of thesetests will allow a better assessment of the quality of initial andclad plates

The reflector types flat bottom hole hemispherical bot-tom hole and side drilled hole (transverse hole) were modelsof a planar point defect spherical point defect and cylindricalelongated defect respectively The beam of ultrasonic waveswith a far field (Fraunhofer zone) was reflected from thesereflectors The first two reflector surfaces were equal to acircular surface 1198781 = 120587119889

24 and a hemispherical surface

1198782 = 1205871198892119897[2(119897 + 05119889)] respectively (Figure 5)

The third reflector had the cylindrical surface 1198783 Thequarter of that surface limited by the cone (Figure 6(a)) wascalculated by means of the contour integral int

119871119910(119909 119911)d119871 The

curve 119871 was expressed by means of the parametric equations

119871

119909 (119905) = 05119889 cos (119905)for 120572 le 119905 le 1205872

119911 (119905) = 05119889 [1 + sin (119905)](3)

After determining 119903 = 05119889(1 + 119889119897)12 and 1199110 = 119889 + 119897

(Figure 6(a)) and the following transformations the conesurface 119910(119909 119911) was calculated for 119910 ge 0

1199092

1199032+

1199102

1199032=

(119911 minus 1199110)2

(1199110)2

119910 (119909 119911) = radic

1199032

(1199110)2(119911 minus 1199110)

2minus 1199092

119910 (119909 119911) = radic1198892

4119897 (119889 + 119897)

(119911 minus 1199110)2minus 1199092

(4)


Beam probez

d

dy

S1 = 120587d24

l

S2 = 120587d2l[2(l + 05d)]

Figure 5 The reflector surfaces 1198781 and 1198782 which are surrounded bya red line relating to flat bottomhole and hemispherical bottomholerespectively

The complete cylindrical surface 1198783 was calculated afterconverting the contour integral into the definite integral

1198783 = 4int

119871

119910 (119909 119911) d119871

= 4int

1205872

120572

119910 [119909 (119905) 119911 (119905)] radic[1199091015840(119905)]2+ [1199101015840(119905)]2d119905

(5)

After including the above data the complete surface size 1198783equals

1198783 = 2119889int

1205872

120572

(

1198892

4119897 (119897 + 119889)

[119897 + 05119889 minus 05119889 sin (119905)]2

minus[05119889 cos (119905)]2)12

d119905

(6)

The reflection surface profile 1198783 is presented inFigure 6(b)

The dependence of the reflector surfaces 1198781ndash1198783 on diam-eter 119889 is presented in Figure 7

The above arguments were tested on three modelledsteel bars Each had eight hole reflectors of the same typewith diameters ranging from Oslash1 to Oslash8mm The followingholes were made eight flat bottom holes eight hemisphericalbottom holes and eight side drilled holes The pictorialdiagram of the holes configuration in steel bars and thelocation of the probe are shown in Figure 8 The reflectorswere tested with the far field beam (119897 = 28mm)The reflector

0

z

120572

120572

d

r

L

z0

x

14S3

l

(a)

(b)

S3 = 2d ( d2

4l(l + d)[l + 05d minus 05dsin(t)]2

minus [05dcos(t)]2)12

dt

1205872

120572int

Figure 6 Integral limits for the quarter of the cylindrical surface 1198783surrounded by a red line (a) and the surface profile 1198783 surroundedby a red line in the upper part of the cylinder (b)

05 183 317 45 583 717 850

25

50

75

100

Refle

ctor

surfa

cesS

1ndashS3

(mm

2)

S1(d)

S2(d)

S3(d)

S2 = S3 = S1

d2 lt d3 lt d1

d2 d3 d1

Reflector diameters d (mm)d

S2 gt S3 gt S1

Figure 7 The dependence of reflector surfaces 1198781ndash1198783 on theirreflector diameters 119889


38 times 150

8 side drilled holes empty1ndashempty8mm

8 flat and hemispherical bottom holes empty1ndashempty8mm

empty1 empty2 empty3 empty4 empty5 empty6 empty7 empty8

l = 28mm

Figure 8 Pictorial diagram of the hole configuration in the steelbars

diameters 119889were named real defectsThe equivalent reflectorsizes (defects) resulted from measurement with the DGStechnique

For the testing of the equivalent reflectors the ultrasonicflaw detector USM 25S and the probe MB4S made byKrautkramer were used A backwall was used as a referencereflector The mean values of the three measured results arepresented in Figure 9

The ultrasonic oscillograph records are presented inFigure 10

22 Test Results for Clad and Initial Plates

221 The Material Properties in the Joint Area Later testsaimed at the evaluation of the properties of clad andinitial plates An example of the macrostructure of theexplosive welded joint is presented in Figure 11 It is thewavy aluminium-duralumin joint from the carbon steel-aluminium-duralumin clad plate Such clad plates find theirapplication in the shipbuilding industry

The macrostructure shows that both materials presentsignificant strain in the joint area In spite of that there areno signs of material discontinuity

Additionally the material strain hardening in the jointarea was tested by a relative increase in the Vickers hardnessℎ = (HVminusHV0)HV0 HV andHV0 are values of the Vickershardness of the material after welding and in the initial stateThe relative increase in the hardness ℎ for the carbon steel-brass joint is presented in Figure 12

222 Cracks in the Clad Plates Defective clad plates resultedfrom the defective initial plates In order to prove this a cladplate with a network of cracks at the edges was examined(Figure 13)These cracks occurred during thewelding processas a result of the existing defects in the initial steel plate

223 Results of Initial Plates before Welding In one of themodern European steel mills 6ndash60mm thick steel plates weretested ultrasonically The obtained results (European Stan-dard EN 10160) for quality grade 1198780 and 1198782 are presented in

05 183 317 45 583 717 8505

21

37

53

69

85

Equi

vale

nt re

flect

or si

zesD

1ndashD

3(m

m)

D(t)

d1

D1(t)d2

D2(t)

d3D3(t)

D(t) = t

D1(t) = 0938t + 0328

D2(t) = 0158t + 1741

D3(t) = 0191t + 1758

corr(d d) = 1

corr(d d1) = 09983

corr(d d2) = 09780

corr(d d3) = 09760

t d t d t d t

Reflector diameters d (mm)

Figure 9 The experimental correlation (corr) of sizes reflectordiameters 119889 (real defects) and equivalent reflector sizes (equivalentdefects)1198631(119905)ndash1198633(119905)1198631(119905)1198632(119905) and1198633(119905) relating to flat bottomhole hemispherical bottom hole and side drilled hole respectively119863(119905) is the theoretical run 119905 is the programme step (1sdot10minus4) withinthe range of 119889 = 1ndash8mm

Figure 14These data showed cracks in the places of hydrogensegregation (dark cylinders and cones) The greatest numberof defects (172 grade 1198782) can be found in steel plates witha bigger thickness (41ndash50mm thick) Initial steel plates evenabove 100mm thick can be welded

3 Discussion

Thesizes of real surfaces reflecting ultrasonicwave beamwereevaluated which is the original authorrsquos solution Howeverthe sizes of equivalent defects were evaluated in compliancewith the assumptions in the literature [8 11]

In the range of the applied real diameters 119889 and lengths 119897the dimensions courses of the reflected surfaces 1198781ndash1198783 wereobtained which satisfy the condition 1198782 gt 1198783 gt 1198781 (Figure 7)The equality of the tested surfaces 1198782 = 1198783 = 1198781 occurs for thecondition of the diameters dimensions 1198892 lt 1198893 lt 1198891 Thesmaller the diameter 119889 the smaller the difference betweenthe surfaces dimensions 1198781ndash1198783 That property occurs also inthe courses of equivalent reflector sizes from the results ofultrasonic testings though the other functions circumscribethem (Figure 9)

The test results for the flat bottom reflectors (corr(119889 1198891) =09983) show the greatest convergence with the theoreticalrun (corr(119889 119889) = 1) (Figure 9) Significant differences can be


Deleteoff

RecalloffStoreoff

CAL 2 DGS TRIG MEM DATA

ER3970500dB

lowast4SET-

Re5000Da988Sa2894Rs000 lowastPRA

(a)

Deleteoff

RecalloffStoreoff

Rs000 Da968 Re5000CAL 2 DGS TRIG MEM DATA

05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)

Figure 10 The ultrasonic oscillograph records of two reflectors with diameter 119889 = 4mm and a backwall as a reference reflector you can seeequivalent reflector size ER = 397mm for flat bottom hole (a) and side drilled hole with ER = 264mm (b) DGS curve refers to Oslash4mm

Aluminium

Duralumin

Interpass

1mm

Figure 11 The macrostructure of the aluminium-duralumin jointarea showing the wavy joint with interpass and significantlydeformed joint boundary layers of both welded materials

observed for the hemispherical bottom (corr(119889 1198892) = 09780)and side drilled (corr(119889 1198893) = 09760) reflectors The staticenvelopes of the echo height indications from the reflectors inthe gates testify to the shape differences of the tested reflectors(Figure 10)

Obtained results as shown in Figures 11 and 12 testify tostructural and strain hardening changes in the welded jointarea There exists a convergence of the test results with datain the papers [2 6]

If in the joint area of welded materials the plasticitymargin will be exceeded then micro- and macrocracks canappear most oftenThe cracks that started in the initial platesreveal for good in the clad plates in Figure 13 Therefore theinitial plates for explosive cladding should not be appliedwithinadmissible defects sizes which form in different productionstages of those metallurgic products (Figure 14)

In this paper the cracks detectable with a wave ultrasonicbeam referred to flat bottom holes (Figures 5 and 7ndash9)

4 Analysis

The analysis of all tests was carried out with respect tointerdepending factors determining the final quality of theclad plate (Figure 1) Despite the fact that the ultrasonic testswere conducted on modelled samples they complied withstandard procedures and material used in the productionof clad plates The obtained test results can assist in betterdetection and interpretation of defects in initial and cladplates

Distance from the joint boundary (mm)

Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)

minus49 minus345 minus2 minus055minus003

y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess

Figure 12 The relative increases ℎ1 and ℎ2 of the hardness as afunction of distances 1199101 and 1199102 from the joint boundary for thecarbon steel-brass joint ℎ1(119905) and ℎ2(1199051) are curves smoothed bya loess procedure

Finally the ultrasonic testing results confirmed theoreti-cal assumptions In the case of a flat bottom reflector the echoheight indication ℎ119903 is proportional to its reflector surfacearea 119878119903 (1) [11] In the cases of hemispherical bottom and sidedrilled reflectors the interdependence is different It is theresult of smaller acoustic pressures 1199012 lt 1199013 lt 1199011 in spiteof bigger reflector surfaces 1198782 gt 1198783 gt 1198781 (Figure 7) Equation(6) referring to the surface 1198783 was useful for the comparativeevaluation


Nominal fieldNetwork crack zone for repairTorch cut line

22601100 830

120220 220

170

110

1040

300

Figure 13The clad plate made of carbon steel (34mm thick grades1198782 and 1198640) and duplex steel (6mm thick) after ultrasonic testing(ASME SA 578) showing crack networks at edges and vertexes inthe carbon steel plate

0

20

40

60

80

100

Range of plate thickness (mm)

Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71

6ndash10 11ndash20 21ndash30 31ndash40 41ndash50 51ndash60

Figure 14 The division of test plates according to accepted criteriagrade 1198780 (cylinders) and grade 1198782 (cones) accepted (light) anddefective (dark 0ndash172) plates

In the DGS method [8] the most correlation betweenreal and equivalent defects was discovered in case of the flatbottom reflector (Figure 9) The reflector models a crack asa defect that is the most dangerous for the welded plateswith the loading and unloading stages (2) With a backwall asa reference reflector the equivalent reflector sizes for hemi-spherical bottom and side drilled reflectors are significantlysmaller than their real sizes

The aluminium-duralumin wavy joint is of a complexinternal structure (Figure 11) Beside the direct joint thereexist also the segments of interpass The layers of bothadherentmaterials to the joint boundary are clearly deformedwithout the loss of cohesionThis area shows strain hardeningwhich is confirmed by the relative increase in the Vickershardness (Figure 12)

In the clad plate cracks can occur from the borders of thesteel plate of a low quality grade 1198640 (Figure 13) Enlargementof those cracks is especially evident in the thick plates of largerbrittleness The regions with such cracks require furthercorrections of the clad plate before their use The greatestnumber of cracks was found in thick steel plates when theywere tested with ultrasonic technique (Figure 14)These thickplates are commonly used for explosive cladding

In order to obtain the right quality of clad plates goodquality initial plates must be used The poor quality of

the initial plates with nonpermissible cracks is often the maincause of their destruction during explosive cladding Thematerial properties in the joint area as well as cracks must beincluded in the selection criteria of the initial plates (Figure 1)

5 Conclusions

Analysis of test results facilitated presentation of these con-clusions

(i) The ultrasonic technique allows detecting types andsizes of material defects in plates before and aftercladding In case of a greater number of cracks it ispossible to calculate a substitute crack for the fracturemechanics

(ii) When the defect diameters 119889 are the same thecurvilinear surfaces of the defects are larger than theflat surface of the defect However the ultrasonicwavy beam reflected from the diffusing surfaces givesa smaller echo height indication than in the case ofa flat defect The value of acoustic pressure alwaysdetermines the echo height indication from a defect

(iii) In the DGS method the correlation between the sizeof the real and equivalent defect is the largest for theflat surface defect which models the most dangerouscrack defect The smaller correlation of those resultswas obtained for the defects with curvilinear surfaces

(iv) The typical joint area of the explosive clad plateincludes the wavy joint surface without or with seg-ments of the interpass Strain hardened layers of bothmaterials have a limited or an exhausted plasticity andare not deprived of their internal stresses This jointarea is the result of the explosive cladding of the initialplates

(v) In case of an inadequate selection of the initial plateswith a low quality grade of the borders one can expectcracks in the clad plate

(vi) Only the initial plates of adequate quality that is withpermissible defects should be explosively welded Itrefers mostly to thick plates with greater brittlenessIt this way the destruction of expensive clad platesduring the welding process can be prevented

(vii) The explosive welding process the plate quality afterwelding and application of the fracture mechanicsshould be employed to ascertain the criteria for qual-ity selection of the initial plates ready for cladding

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

References

[1] T Z Blazynski Explosive Welding Forming and CompactionApplied Scientific New York NY USA 1983


[2] A A Deribas Fizika Uprocznenija i Svarki Vzryvom NaukaNovosibirsk Russia 1980

[3] B Wronka ldquoTesting of explosive welding and welded jointsWavy character of the process and joint qualityrdquo InternationalJournal of Impact Engineering vol 38 no 5 pp 309ndash313 2011

[4] I Plaksin J Campos J Ribeiro et al ldquoNovelties in physicsof explosive welding and powder compactionrdquo in Proceedingsof the 7th International Conference on Mechanical and PhysicalBehaviour of Materials under Dynamic Loading (Eurodymatrsquo03) pp 797ndash802 Porto Portugal September 2003

[5] B Wronka ldquoTesting of explosive welding and welded jointsJoint mechanism and properties of explosive welded jointsrdquoJournal of Materials Science vol 45 no 15 pp 4078ndash4083 2010

[6] B Wronka ldquoAcoustic and mechanical anisotropy in the testingof explosively welded jointsrdquo Insight vol 52 no 11 pp 603ndash6082010

[7] V Favier S Berbenni X Lemoine andM Berveiller ldquoDynamicbehaviour of steels an elastic-viscoplastic micro-macro poly-crystalline approachrdquo in Proceedings of the 15thDymat TechnicalMeeting Crashworthiness and Constitutive Relationships forEngineering Materials pp 51ndash56 LPMM-University of MetzMetz France 2004

[8] European Standard EN 583-5 ldquoNon-Destructive Testing-Ultrasonic ExaminationmdashPart 5 Characterization and Sizing ofDiscontinuitiesrdquo 2000

[9] European Standard EN 583-2 ldquoNon-Destructive Testing-Ultrasonic ExaminationmdashPart 2 Sensivity and Range Settingrdquo2000

[10] European Standard EN 1713 ldquoNon-Destructive Examination ofWelds-Ultrasonic Examination-Characterization of Indicationsin Weldsrdquo 1998

[11] J Krautkramer and H Krautkramer Ultrasonic Testing ofMaterials Springer New York NY USA 4th edition 1990

[12] C H Gur and Y Keles ldquoUltrasonic characterisation of hot-rolled and heat-treated plain carbon steelsrdquo Insight vol 45 no9 pp 615ndash620 2003

[13] K Yamanaka T Mihara and T Tsuji ldquoEvaluation of closedcracks by analysis of subharmonic ultrasoundrdquo Insight vol 46no 11 pp 666ndash670 2004

[14] M Kocak S Webster J J Janosch R A Ainsworth andR Koers FITNET Fitness-for-Service GKSS Research CentreGeesthacht GmbH 2008

[15] T L Anderson FractureMechanics Fundamentals and Applica-tions CRC Press 3rd edition 2000

[16] C E Inglis ldquoStress in a plate due to the presence of cracks andsharp cornersrdquo Transaction of the Institution of Naval Architectsvol 55 pp 219ndash230 1913 (Reprinted in Fracture MechanicsRetrospective ASTM RPS 1 1987)

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Ultrasonic testing

Two initial metal platesfor cladding

Explosivewelding

Cladding

and backing metal joined by welding Clade plate

Figure 1 Ultrasonic testing used for initial metal plates beforecladding and clad plate after explosive welding

Explosive

Base metal

Cladding plate

Wavy joint surface Jet

Claddingmetal

Backingmetal

Vd

Vp120573

VC

C

120582

Anvil

Figure 2 The course of the explosive welding process 119881119901 is theflyer plate velocity 119862 is the collision point 119881119862 is the collision pointvelocity 119881119889 is the detonation velocity 120573 is the collision angle and 120582is the joint wavelength

Fast cooling of thick plates within the range of tempera-tures 473ndash293Kmakes it difficult for hydrogen to be expelledfrom steel by diffusion High hydrogen pressure increasesthe size of existing cracks and causes snowflakes to appearalong the plate fibres This phenomenon lowers the plasticand strength properties of material across its fibres Whenthe temperature is too high and the heating time is extendedoxygen permeates from the semifinished steel surface to thegrain boundaries and a network of hot cracks appears

The band arrangement of these inclusions and lap slagshas a significant influence on the anisotropy and mechanicalproperties of steel Insufficient or uneven heating of billetsand improper plastic working cause lapping with visible platelayers Lap blowholes draw holes and nonmetallic inclusionsare the reasons for plate delaminations

The ultrasonic technique takes into account differenttypes of material defects The following types of materialdefects can be discriminated point elongated large andmultiple [8] The type of defect is determined on the basis ofthemaximum echo height of the indication from a defect thedirectional dependence of the echo amplitude and the staticand dynamic envelope of the echo height indication [9 10]The example of the point defect is shown in (Figure 3(a))Theprinciples of such testing for plate inspection are presented inthe literature [11ndash13]

1 2

36

4

5

(a)

12

3

4

5

4

A

A

A1

A1

(b)

Applied criterion

Dimensions

2c1

2c2

a

2a1

2a2

s

s le a1 + a2

a = 2a1 + a2 + s

2c = 2c1

(c)

Figure 3 The ultrasonic echo responses of the point defect (a)1 amplitude 2 A scan (static envelope) 3 range 4 variation ofpeak signal amplitude (dynamic envelope) 5 probe position and 6reflector beam axis tip location technique (b) 1 and 3 echoes 119860 and1198601 at maximum heights 2 variation of peak signal amplitude 4 Ascan and 5 echoes 119860 and 1198601 will be the first to appear when probeis moved backward and forward the dimensions of substitute crack(c)

The assessment of defect size withmanual testing is basedon the maximum echo height techniques (DGS and DAC)and probe movement sizing techniques [8] (Figure 3(b)) Ifcracks lie close to each other (Figure 3(c)) one establishes thesize of a substitute crack [14]

The later contents of this paper refer to more difficult todetect small defects For a small reflector the proportionalityof the echo height indication ℎ119903 and the acoustic pressure 119901 isgenerally known for an equivalent defect that is flat defectnormal to the ultrasonic beam These and other acousticparameters such as the initial acoustic pressure 1199010 the flatreflector surface area 119878119903 with diameter 119889 the transducersurface area 119878119905 the wavelength 120582 and the distance 119897 give thefollowing [11]

ℎ119903 sim 119901 = 1199010

119878119903119878119905

12058221198972 (1)

For the assessment of real defects their experimental shapefactors are needed

The knowledge about the relationship between crack sizeand object load is given by the fracture mechanics [15]


2c

2b

120590

120590

120590max

(a)

2b

c

120590

120590

120590max

(b)



120572 =

120590max120590

= 1 +

2119888

119887

= 1 + 2(

119888

120588

)

12

(2)




2 Results






119871119910(119909 119911)d119871 The


119871

119909 (119905) = 05119889 cos (119905)for 120572 le 119905 le 1205872

119911 (119905) = 05119889 [1 + sin (119905)](3)



1199092

1199032+

1199102

1199032=

(119911 minus 1199110)2

(1199110)2

119910 (119909 119911) = radic

1199032

(1199110)2(119911 minus 1199110)

2minus 1199092

119910 (119909 119911) = radic1198892

4119897 (119889 + 119897)

(119911 minus 1199110)2minus 1199092

(4)


Beam probez

d

dy

S1 = 120587d24

l

S2 = 120587d2l[2(l + 05d)]



1198783 = 4int

119871

119910 (119909 119911) d119871

= 4int

1205872

120572

119910 [119909 (119905) 119911 (119905)] radic[1199091015840(119905)]2+ [1199101015840(119905)]2d119905

(5)


1198783 = 2119889int

1205872

120572

(

1198892

4119897 (119897 + 119889)

[119897 + 05119889 minus 05119889 sin (119905)]2

minus[05119889 cos (119905)]2)12

d119905

(6)




0

z

120572

120572

d

r

L

z0

x

14S3

l

(a)

(b)

S3 = 2d ( d2



dt

1205872

120572int


05 183 317 45 583 717 850

25

50

75

100

Refle

ctor

surfa

cesS

1ndashS3

(mm

2)

S1(d)

S2(d)

S3(d)

S2 = S3 = S1

d2 lt d3 lt d1

d2 d3 d1


S2 gt S3 gt S1



38 times 150




l = 28mm











05 183 317 45 583 717 8505

21

37

53

69

85

Equi

vale

nt re

flect

or si

zesD

1ndashD

3(m

m)

D(t)

d1

D1(t)d2

D2(t)

d3D3(t)

D(t) = t

D1(t) = 0938t + 0328

D2(t) = 0158t + 1741

D3(t) = 0191t + 1758

corr(d d) = 1

corr(d d1) = 09983

corr(d d2) = 09780

corr(d d3) = 09760

t d t d t d t




3 Discussion





Deleteoff

RecalloffStoreoff


ER3970500dB

lowast4SET-


(a)

Deleteoff

RecalloffStoreoff


05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)


Aluminium

Duralumin

Interpass

1mm






4 Analysis



Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)


y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




2c

2b

120590

120590

120590max

(a)

2b

c

120590

120590

120590max

(b)



120572 =

120590max120590

= 1 +

2119888

119887

= 1 + 2(

119888

120588

)

12

(2)




2 Results






119871119910(119909 119911)d119871 The


119871

119909 (119905) = 05119889 cos (119905)for 120572 le 119905 le 1205872

119911 (119905) = 05119889 [1 + sin (119905)](3)



1199092

1199032+

1199102

1199032=

(119911 minus 1199110)2

(1199110)2

119910 (119909 119911) = radic

1199032

(1199110)2(119911 minus 1199110)

2minus 1199092

119910 (119909 119911) = radic1198892

4119897 (119889 + 119897)

(119911 minus 1199110)2minus 1199092

(4)


Beam probez

d

dy

S1 = 120587d24

l

S2 = 120587d2l[2(l + 05d)]



1198783 = 4int

119871

119910 (119909 119911) d119871

= 4int

1205872

120572

119910 [119909 (119905) 119911 (119905)] radic[1199091015840(119905)]2+ [1199101015840(119905)]2d119905

(5)


1198783 = 2119889int

1205872

120572

(

1198892

4119897 (119897 + 119889)

[119897 + 05119889 minus 05119889 sin (119905)]2

minus[05119889 cos (119905)]2)12

d119905

(6)




0

z

120572

120572

d

r

L

z0

x

14S3

l

(a)

(b)

S3 = 2d ( d2



dt

1205872

120572int


05 183 317 45 583 717 850

25

50

75

100

Refle

ctor

surfa

cesS

1ndashS3

(mm

2)

S1(d)

S2(d)

S3(d)

S2 = S3 = S1

d2 lt d3 lt d1

d2 d3 d1


S2 gt S3 gt S1



38 times 150




l = 28mm











05 183 317 45 583 717 8505

21

37

53

69

85

Equi

vale

nt re

flect

or si

zesD

1ndashD

3(m

m)

D(t)

d1

D1(t)d2

D2(t)

d3D3(t)

D(t) = t

D1(t) = 0938t + 0328

D2(t) = 0158t + 1741

D3(t) = 0191t + 1758

corr(d d) = 1

corr(d d1) = 09983

corr(d d2) = 09780

corr(d d3) = 09760

t d t d t d t




3 Discussion





Deleteoff

RecalloffStoreoff


ER3970500dB

lowast4SET-


(a)

Deleteoff

RecalloffStoreoff


05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)


Aluminium

Duralumin

Interpass

1mm






4 Analysis



Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)


y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Beam probez

d

dy

S1 = 120587d24

l

S2 = 120587d2l[2(l + 05d)]



1198783 = 4int

119871

119910 (119909 119911) d119871

= 4int

1205872

120572

119910 [119909 (119905) 119911 (119905)] radic[1199091015840(119905)]2+ [1199101015840(119905)]2d119905

(5)


1198783 = 2119889int

1205872

120572

(

1198892

4119897 (119897 + 119889)

[119897 + 05119889 minus 05119889 sin (119905)]2

minus[05119889 cos (119905)]2)12

d119905

(6)




0

z

120572

120572

d

r

L

z0

x

14S3

l

(a)

(b)

S3 = 2d ( d2



dt

1205872

120572int


05 183 317 45 583 717 850

25

50

75

100

Refle

ctor

surfa

cesS

1ndashS3

(mm

2)

S1(d)

S2(d)

S3(d)

S2 = S3 = S1

d2 lt d3 lt d1

d2 d3 d1


S2 gt S3 gt S1



38 times 150




l = 28mm











05 183 317 45 583 717 8505

21

37

53

69

85

Equi

vale

nt re

flect

or si

zesD

1ndashD

3(m

m)

D(t)

d1

D1(t)d2

D2(t)

d3D3(t)

D(t) = t

D1(t) = 0938t + 0328

D2(t) = 0158t + 1741

D3(t) = 0191t + 1758

corr(d d) = 1

corr(d d1) = 09983

corr(d d2) = 09780

corr(d d3) = 09760

t d t d t d t




3 Discussion





Deleteoff

RecalloffStoreoff


ER3970500dB

lowast4SET-


(a)

Deleteoff

RecalloffStoreoff


05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)


Aluminium

Duralumin

Interpass

1mm






4 Analysis



Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)


y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




38 times 150




l = 28mm











05 183 317 45 583 717 8505

21

37

53

69

85

Equi

vale

nt re

flect

or si

zesD

1ndashD

3(m

m)

D(t)

d1

D1(t)d2

D2(t)

d3D3(t)

D(t) = t

D1(t) = 0938t + 0328

D2(t) = 0158t + 1741

D3(t) = 0191t + 1758

corr(d d) = 1

corr(d d1) = 09983

corr(d d2) = 09780

corr(d d3) = 09760

t d t d t d t




3 Discussion





Deleteoff

RecalloffStoreoff


ER3970500dB

lowast4SET-


(a)

Deleteoff

RecalloffStoreoff


05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)


Aluminium

Duralumin

Interpass

1mm






4 Analysis



Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)


y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Deleteoff

RecalloffStoreoff


ER3970500dB

lowast4SET-


(a)

Deleteoff

RecalloffStoreoff


05

MEM

00dB

lowastPRA

lowast10SET-

Sa2832

ER264

(b)


Aluminium

Duralumin

Interpass

1mm






4 Analysis



Jointboundary

Carbon steel Brass

09 235 38

005

013

021

029

037

045

h1h1(t)

h2h2(t1)


y1 t y2 t1

The r

elativ

e inc

reas

e in

the h

ardn

ess





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





22601100 830

120220 220

170

110

1040

300


0

20

40

60

80

100


Qua

ntity

of p

late

s (

)

34 20 28

12355

172

47 002 0 44 71








5 Conclusions











References

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials


























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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