GB2225511A - Ultrasonic transducer for defectoscopy - Google Patents

Description

1 n=OIIC T=WM &R DWEGASCOPY The invention relates to instrumentation means

and in particular to ultrasonic transducers for use def ec t osc op y.

The invention em be used for nonaestructive test ing of materials and products, %eluding welds, metal structures of diverse application, naelew reactor casings and assemblies, in shipbuilding and civil engUeering, e.g. trunk pipeline construction, and oteer similar objects in various fields of macnine building and civil engineering.

E-nown in the art is an ultrasonic transducer with a variable aLgle of ultrasonic bean injection, the transducer copprisinG a prism with a conical cavity is LousinG a rotatable asseCly carrying the piezo electric element. In such a transducer the anle of ultrasonic be= injection is varied by turning the rotatable assembly with the piezoelectric element respective to the prisi.

A drawback of such transducers is the iposskility of automatic incidence angle variation and determination of the instanteous value of Ms angle, this providinG eLly detection of a uefect, but not its coordinazes and its deptn and thus ioairing -uae productivity and validity of quality control.

in 2 Also known in the art are ultrasonic transducers with a semicirculart positionally sensitive to eddy cur-rents plate is used to electrically control the angular position of the entire transducer waica also comprises a radiatort aspherical acoustic lens and radiator servodrive. Such a transducer is inertial due to its servocLrive, this restricting tae scanning speed of the ultrasonic beam.

ApproachinG tiae tecunical essence of the present invention is the autoscanning ultrasonic transducer v-h an ultrasonic prism in which a cavity touses a it rotatable assembly mounting at least one piezoelectric elemen-u.

"'his transducer cororises a irive in the L Uorm of two electromagnets. The rotatable assembly contains a strip of ferroma6netic material, tiais plank mounting tlie piezoelectric elements and serving as the electromagnet' s armature.

A disadvantage of tais transducer is a low quality control productivity due to restrictions on the oscillation rate of the assembly carryin6 piezoelectric elements imposed by turbulence and viscosity of the f taliquid medium (usually oil). AnotLer arawback o. -s transducer is its reduced sensitivity and the presence of a dead Zone due to rereflections wit.---in the i=e,-sion liquid from the boundary betweex, the liqujd C-n"z V th-e -L'o5y. lesides, t.ris, it is L.-Dosss:i:ble to o'bza-J..rdata on the instanteous value of the be" incidence angle and therefore this transducer is incapable of providU6 -a two-dimensional VaSe of tie object' s area being monitored.

It is an objective of the invention to provide an ultrasonic transducer for defectoscopy, waich is capable of quickly generating, two-dimensional image of the object being inspected.

mother objective of the invention is to provide a Ugner productivity of tie inspection process.

Yet "other objective is to improve the validity of the inspection process, These wd other objectives axe achieved by that the ultrasonic tvansducer for defecooscopy wita automan tic ultrasonic beam scanning according to the invention coorises a prism wita a cavity housinG at least one piezoelectric element mounted on an assembly for said piezoelectric element rotation, a drive for ultrasonic beam scanning interlinked to Me piezoelectric element rotation assembly wd fitted to the prism, and a sensor of the ultrasonic scanning beam incidence aLSle coaled to the piezoelectric element rotation asseOly and mounted on tie prism.

It is eye"ient to gTovide tie Ocidence aL61e sensor with a movable member fitted to tne piezoelectric element rotation asseOll and a swaoionary me0er wiK wita two inductively coaled windiLls mounied oL the J+ prism and interacting witr- the movable member to generate a signal proportional to the angle of oncidence or angle of ultrasonic beam injection.

The incidence angle sensor of the scanning ultra- sonic beam may include a rotation an61e arrester to limit the angle of rotation of the piezoelectric element rotation assembly, tr-is arrester comprising two elastic mechanical repellers mounted to the prism and,-lso two pins fitted to prism on both sides of the movable member wita each of the pins linked to its respective Ln- echaLical repelleX, and a mode control switch which in i-us first- state holds the movable member in a nrutral position by means of the mechanical repellers and in its second state provides reciprocal displacement of the movable member between the spaced weenanical repellers.

It proved to be auvantageous to embody the mechanical repellers as a sinnle elastic member wnich holds the movable member in its neutral positien by tne free ends of this elastic member.

It is also advisable tnat the rotation angle arre-ster should comprise two resz mounted on a pris= on- each side of the r_ovable re=ber ana interseting with respective meccanical repellers when tais movable memiber is in neutral Dositicn.

It is drive ior ultrasonic bea= seai-,ring includes an AC elec-vrora:7net it is advar-ta--eous to electrically C3 C2 connect the contacts of the mode control switch to the AC electromagnet windin6 so tnat wnen these contacts are open the movable member is in its neutral postion and when the contacts are closed the mecnanical repellers release the movable member for reciprocal movement.

13 The incidence an gle sensor of the scanning ultrasonic beam may be equipped with a spring fitted to the prism and spring-loading the movable me=berg the C) spring stiffness being preferrably selected so as to ensure the mechanical resonant frequency of the incidence ariGle sensor of:' the scanning ultrasonic beam being equal to or less tran the frequency of movable me=ber displacement.

It is also expeuient to include a ferromagnetic element in the ultrasonic beam scan drive; this element, may be a permanent magnet roanteci on tne pierzoelectric ele-ment rotation asse=bly witu one pole uirected toward the interpole gap of the AC electro- magnet, It is furtner expedient to provide the piezoelectric element rotation a- 'sewrly Witn a body of revolution mounting az least one piezoelectric element and ferromagnetic elemenz, tais body of revolatior- 25being positioned inside the prism cavit-;, wit-r a gap v filled by a sc)u-nd conducting liquid and mec-,anically linked to the movable element of the incidence azgle sensor of the Scanning ultrasonic beazi, zte wiUJt.- 6 0 of the gap between the body of revolution selected to be a multiple of halfwaves of the ultrasonic wave in the sound conducting liquid filling the prism cavi- ty.

Such an embodiment of the ultrasonic transducer for defectoscopy improves the validity of object in spection and also increases the operator's productivity, Other objectives advantages and features of the invention will be evident from the following descrip- tion of examples of its embodiment and accompanying cLrawings, wherein:

c) Fig. 1 illustrates tr-e general appearance of the ultrasonic transducer of the Invention; Fig. 2 shows a section along line II-II of the 15 transducer of Fig. J; Fig. 3 depicts the rotation an61e a=estex of the invention and the movable member Jin its neutral position, general appearance; 4 show.s the c,-.L.e retaT.J,-or. a-riC-le ar-.eszar in 20 itis other state; and Fig. 5 presents the circuit dia6ra--oof drive for ul- vrasonic beam sc;Rn-niiig according to the invention.

Detailed Descriotion of the!,-1Ve"--v.LOr, !lie ultrasonic t-rhansduce2 for ce-L'ec-uo-zcopy -,vi-ja -c'uito-a-cie ultrasonic bea= scanning comp-rises zr:Lsz. 1 l, 2) az azially symmetu--.!L-., e.g.

1, - - cal, cavity 2 hous-Jnj Diezoelec-uric e-.LezeLt 'FiG. 2, 13 - 1? jiiich is mounted onto piezoelectric element rotation assembly 4. The number of piezoeleczric element 3 positionea inside cavity 2 may be greater -Utlan one and is determined by the sonic test procedure and the 5 taickness of the object under inspection.

For the sake of simplicity, only one piezoelectric element 3 is snown in the d-awing mounted onto daw,per 5 fabricated for example from epoxy, r. esin with a filling.

1) Iias tailpiece 6 protruaing Asselcily 4 (- C) oat ot prism 1 via gland 7.,,aviGy 2 (Fig. 2) is f illed souni condic-ving licuia, e.g. -jecrinical oil or glycerine.

1he contacless drive for ultrasonic bea= scanning is fitted -o -orisj: 1 anki:zeciiaric ally coupled to tile 3otation assembly 4. The d-rive coin; D2ises A.CO electro- magne-. & wita two windings 9 and 10 on coTe 11.

jhe t--ansducer of the in,,,,ention also inclucLes a sca=ing ultrasoric beam incidence anSle sensoT w.'Lio.i contains a movable member 122- (Fig. It 3) in tiae form of a szrip fit-. ed to tailpiece o ana a Stationary as-seml,ly o. Uwo inductivel7 coupleL viirdints I-- a d ol 4) MoanteJ ori. b--acke-, 15 i-- muz"ally s.

parallel planes. '.'tie tu:!ns windin-s I-, and 14 a-re -1 4-- 71 - iarZ_ L. - U.

-ilar in snape. racke-, l- is to er ce by sc a" 1C. "-ovc:l is pos---t-DrLc-a betwe-er. v;Ji-nzin.-s 5:.n-J I" -)az7a--,lel to 8 1 P their planes and iteracts witL these windings 13 and 14 so that a signal proportional to the an6le of ultrasonic beam incidence or injection is generated (the object under test is not shown in the drawinG); the ultrasonic transducer is mounted onto the object under 4 for the latter's defectoscooic studies and inspection f quality control.

The incidence angle sensor also comprises an arrester to limit the stroke of the rotation assembly 49 this arrester containing two elastic mechanical repellers 17 and 16 fitted to prism 1 and interacting wita movable member 12. Prism 1 also mountes two pins 19 and 209 each for its respective repeller, 17 and lo. Pins Tj and 20 are positioned -Go both. sides of movable member 12. TLe ar-,ester further comDrises switch 21 waich is engaged witia repellers 17 and 16 and correspondingly ensures -repelle:os 17 and Jo being posit'-oned to one oil two posit--bns relative to movable member 12.

As seen in FiEs. 3, 4, repellers 17 and 18 are e.mbod-.Led as a sin6le sprin6 mezber in the f orm Of a s-DrinL, wire fitzed to pins 1,. ana 20 ana navin, free ends 222: and Prism I also mounts rests 24 and 25 LO-L -repel lers 17 and 1,-, respectively, to wnicu, re,,ellers 11,7 and 16 ar e D r e s s ed v., a, en m. oveo 1 e mefo e, 12 is i - S neutral positior, and ea aged by repellers Ir-, aLa In 9 as shown in Fig. 3.

The inciaence antle sensor is provided with spring 26 (Fig. 1) to engage movable member 12 to stationary scaft 27 mounted. on prism 1 and thus spring-load movable member 12 relative to prism 1. The stiffness of spring 26 is selected so as to provide the frequency of incidence angle sensor mechanical resonance being equal to or lower than the frequency of movable member 12 dis-z51ace-ment or the rate of ultrasonic beam scan- nin6.

Spring 2b serves to ensure a uniform stroke of Uhe =ovable me=ber 12 and due to such a stiffness provides thLe uesired, e.g. linear, law 01. ultrasonic beaj. incidence var.Lation wi-ul tizie.

The ultrasonic beam scan drive comprises a ferromagnetic element in the form of a permanent magnet 2d fit.,,.ed to asze=bly 4 2). One pole o.i.. per=anent ma6net, 2o is -,irecteci toward. trie inter pole ---ap 29 o-" electroma-nez d wnose wirdi-m-.s 9 and Q C) C 10 are electrically connected in series with contacts of srItell 31 3) and terrainals 31 of the' po-ser supply (.-ot snown).

Assembly 4 2) cc)nLa,-r-s a body of revolu- tion, in the example being desc--,ibe.,JL - a cylindrical LO,,.JLy wilJ-c-n is positioned. in cavity 2 c'& p-s- 1 a sap 2-5 o'-j Q' revolatiozil moun-,s piezoelectric element andl perzamen-.

magnet 28 and is engaged to movable member 12 via tailpiece 6.

The gap 11111 between body 32 and prism 1 is of a width equal to a multiple of halfwaves of the ultra sonic wave in the liquid filling cavity 2, i.e.

1 = n /2, where is the wavelen6ta and n is an integer (n The ultrasonic transducer functions as follows.

In the constant incidence angle mode 3) mecrianical repellej,s 17 and it5 are brou6ht to6etaer by the mode control switch 21 slider waich, in turL, opens contacts 30 and disconnects windings 9 and 10 of electromagnet 6 from the control voltage. At the same time meGi-ianical repellers 22 and 23 are pressed against rests 24 and 259 respectively, and tiaus immobilize the piezoelectric element rotation assembly 4 so that the piezoelectric element 3 in asseffoly 4 - by movable member 12 to a position correspondi s s e the ultrasonic ing to a standard inciaence angle o.L beam.

In the scanning mode (Fig. 4) mechanical repellers 17 and 16 are brouz:, at aparst- on stationary p4-ns 1 and 20, waile switca 21 in its turn closes --mleczJ 10 of ric contacts 30 to connect windin,:,s an.

electromagnet 8 to tiae power con-Vro'l v,:,! taSe is a_)-plied to electroma,:.,neetv c via close%.:, switon 21 and generates an, AC, magnetic field to at-Vraot-

2 11 or repel permanent magnet 2d and taus induces oscillations of the rotation assembly 4 and therefore the engaged to it movable member 12 within the preset scanning sector. Spring 26 serves to improve the stroke uniformity of the piezoelectric element rotation assembly 4 and features a stiffness such that the resonant frequency of assembly 4 is not below its rate of rocking. lovable member 12 swings between windings 13 and 14 and taus perio--ically varies tneir mutLial inductance and therefore the magnitude of electric signals induced in one of these windings; -G&,.úis electric signal constitutes tt- e output signal of the incidence angle sensor.

-ion of the ultrasonic Adjustments and calibrat.uransducer necessitate zlie availability c" th- constant incidence angle mode in w.ic.. scannin, is s.Uoppei and piezoelectric element 3 is in a fixed poskiior-9 so vnat Urle transducer functions as a common inclined trans ducer.

laus the autoscaniin.. transducer of tre invention CJ provides a two- to tiir,-:,ef old increase in productivity -o =-d an improved validiQy o: ultrasonic tes-us due Lly ose.

ar, increased frequency of movable asse--L.-,, "Ila- tions provided by -Vne use of a contactless drives a 23 ser-s4-tivity c--. tr-e 'crarsAJacer at- a -n-=rro-,,,er uead zone, tae ava-.'Llabili-.y of dalua or, 'GLe ",eous value of' tne ultrasonic beai incidence azile, u 1 and the ability to set the transducer to a position corresponding to tue ultrasonic beam's standard angle of incidence.

A 4HAT WS =M IS:

1. A ultrasonic transducer for defectoscopy with automatic ultrasonic beam scanning, the transducer comprising a prism with a cavity nousins at least one piezoelectric element and assembly for rotating the mounted thereof said piezoelectric element 1 said transducer further coprisin6 a supersonic beam scan dr&e intercoupled to the piezoelectric element rotation assembly and moantea- on tie prism$ and a sen- sor of the incidence angle of the scanning ultrasonic beam also coupled to the piezoelectric element rouation assembly and also mouncea- on the prism

Claims (1)

1. 2. The ultrasonic transducer W Claim 1, wherein me incidence angle sensor

   of the scanninG ultraonic beam comprises a movable me=er mounte! on the piezoelectric element rotation assetbly, and a stationary assembly witn two inductively couplei windinjs mounted on the pris= and inzeractinj witn the movable meGer to generate an electric signal proportional to A the angle of incidence or injection of the ultrasonic beam.

   3. Tie UPraSOAC zransiucer & ilaii c, weerecinciaence the sensor of the aLC1e of ulurasonic beam comprises an a2restor to Init one zotatioL anale o:

   one yiezoeleco2ic elemeW rotation asaeOiy, ine arrester proviaea wi= nwo elastic secoanic repellers 14 mounted on the -Pr-isr..

   4. The ultrasonic transducer of Claim 39 wnerein the rotation angle arrester comprises two stationary pins located on the prism to both sides of.!-us respective the movable membery each pin engage i meenanical repellerg the arrester further cokprising mode control switch to hold the movable member in neutral position when the switch is set to one working position and releasing the movable member to reciprocably move between the brouGht apart inecaa nical repelle-- when the switch is in its other work.ing position.

   r'. inhe ultrasonic transducer of Claims or 4 11 A.

   whe.rein the meenanical re L.

   v - pellers aze a s-nCle sp--ng element nolding tne movable member in i-.s neuzral POS.L-ulon by the free spring ends.

   6. The ultrasonic transduce-- of anny '31aim fro-- 3 to 5, wnerein the rotatioL angle arre-slier comp-rises vvjo --eszs mounted on tne pri-EX tO bOZr- SICeS Of tZe movable member and engaged wizh their respective meenanical repellers wrien the L.Ova:rjle member is set Z0 zhe ne.--z-,al Ltion.

   nsducer c-' o: -u-e !he ul,,zasoiiic tzany J Claims 4 to b, wherein ultrasonic be-am sea-, IA..r iv e 25 c- On z a ins an AGG e 1 e c t, r o magr, e -., wn J 1 e t L.-:- c j r.-u ac z s o--' the mode control are connec-ue--J zo, -.he electromagnet's so thaz zr---se conzac-js are open wuen ttLe movable member is set to its neutral position and closed when the mechanical repellers release tae movable member for reciprocal motion.

   8. The ultrasonic transducer of either of the Claims 2 to 7, wherein the sensor of the scanning ultrasonic beam incidence angle is equipped with a sprinG fixed to the prism and spring-loadInG the movable inember.

   9. Trie ultrasonic transducer Oft' IJIaim d) - the mechani- wherein the spring stiffness is suet that cal resonant frequency of the sensor of the scenning ultrasonic beam incidence angle is equal to or less 0 movable member r_ovement.

   tLan the rate of 10. The ultrasonic transducer of Glair. 7 in conunction v;:Lt"- Claims 8 or 9, iv.-.erein the ultrasonic bear- scan drive comprises a. ferroma-netic element 0 fittec, to tne piezoelectric element rotation assembly, Tne ulzDasonic transaucer of ilaiz 1Gy where in tne ferromagnetie element is a oerzanerz ina,,net one pole directed towards the interpole t;ap of the;.C electromagnet.

   12. An ultrasonic transducer 2,-,cording to Claim 2 in conjunction- witn Claizs IG or 1,1, ir. wrnien the piezoelectric element rotation assembly comprises 2 5 a "L-.;c)dy o.'1. revoluzion w.-Ltr- at least one oieroelecz--ic elerrent ard -J2erro=agne-.ic element P-ounted on tais boj,y of revcluc,'Lc--, wj-icz is witt a sap 0 16 within the prisml s cavity filled with a sound conductivity liquid and is engaged to the movable member of the incidence angle sensor of the scanning ultrasonic beam.

   13. The ultrasonic transducer of Claim 12y wherein the width of the gap between the body of revolution and the prism constitutes a multiple of halfwaves of the ultrasonic wave in the sound conducting liquid which fills the prism cavity.

   14. An ultrasonic transducer for defectoscopy as described above with reference to the accompanying drawings.

   Pub'isbed 1990 at The Patent Office. State House. 55 71 High HoIborn. LondonWC1R4TP. Further copies maybe obtainedfrom The Patent Office Sales Branch, St Ma-,-y Cray. Orpington. Kent ER5 3RD Printed by Multiplex techniques Itzi. St Mary Cray, Kent. Can 1,'87