Development of acoustic methods and production of modern digital devices and technologies for ultrasonic non-destructive testing

Transcription

1 ULTAGASAS Journa, Utrasound Institute, Kaunas, Lithuania For a papers of this pubication cick: ISSN ULTAGASAS, Nr.4( Deveopment of acoustic methods and production of modern digita devices and technoogies for utrasonic non-destructive testing A. Samokrutov, V. Shevadykin, V. Bobrov, V. Kozov Joint Stock Company esearch Institute Of Introscopy of MSIA«SPECTUM». Buid. 1, 35 St. Usacheva, Moscow, , ussia, Phone/fax: ( ; ( E-mai: samokrutov@acsys.ru Abstract Acoustic fieds, formed in soid haf-space by sma aperture sources of norma and tangent forces are investigated. Methods of utrasonic testing, using transducers with dry point contact and eectro-magnetic acoustic transducers are proposed. esuts of investigated of muti-eements antenna are presented the exampes of soving the specific tasks for testing the concrete structures, rais, weds and others a given. The information about the new up-to-date digita equipment, deveoped basing on information technoogies is presented. Keywords: acoustic method, deveoped basing on information technoogies. Introduction The significant roe in effective production and safe expoitation of structures pay technoogies and means of Nondestructive Testing and Technica Diagnostics, based on different principes of materias and fieds interaction [1]. The most widey appicabe method is utrasonic testing, based on excitation of utrasound in the object under a test with piezoeectric or eectromagnetic transducers. Among the probems, imiting impementation of utrasonic methods, is the necessity of creation and hoding the stabie acoustic contact, therefore the researchers pay serious attention to methods of utrasound excitation of different types in wide frequency range, using transducers with a dry point contact (DPC and eectromagneticacoustic transducers (EMATs [1-3]. Another direction of deveopment and improvement of methods, equipment and testing technoogy is impementation of muti-eement antenna arrays with sma-aperture transducers and digita data processing. The muti-eement transducers and antenna arrays (both inear and two dimensiona are the new stage in deveopment of transducers with a iquid contact type. The main advantage of these muti-channe transducers is the possibiity of eectronic contro over the input ange, position of focus point and wave type due to independent deay for every eement when sending and receiving acoustic signas. Investigations of the use of phased antenna arrays and EMATs were made by speciaists of esearch Institute of Introscopy of MSIA SPECTUM, Moscow. As a resut, these types of transducers aow avoid the infuence of unstabe acoustic contact on testing and aow impementation of new methods of utrasound excitation and signa processing (such as pusing with phasemanipuated signas, SAFT, correation data processing and other. Basing on the resuts of investigation, the speciaists deveoped the number of devices and equipment for utrasonic nondestructive testing of concrete with echo technique, for thickness measurement in a wide range using piezoeectric and EMA transducers, for guided wave testing of rais, for tomographic testing of weds. These devices and equipment simpify the testing procedures and technoogies, improve the metroogica characteristics of equipment, reduce the infuence of human factor and improve the objectivity of utrasonic testing resuts [1, 3-11]. Acoustic fieds of sma-aperture piezoeectric transducers (SAT. To determine conditions for effective excitation of shear and ongitudina waves the investigations of acoustic fieds, formed in a soid haf-space by sma-aperture sources of norma and tangentia forces, and experimenta researches of echo-signas characteristics for utrasonic waves sent by SAT in different materias, were made [4-11]. The tangentia force creates on the boundary of a soid isotropic haf-space in eastic body osciations, due to two mechanisms: compression and shear deformation. This causes excitation and propagation of different wave types: ongitudina, shear, surface waves. When anayzing the fieds of piezoeectric transducers with a dry point contact, which are the eements of antenna array, with aperture equa or smaer then the waveength (SAT, was described the muti-mode 3D fied of eastic tensions, excited by the norma or tangentia force, acting on the boundary of haf-space. Fig. 1. Cacuation scheme for fied of norma F Tz or tangentia F Tx harmonic force source 1

2 ISSN ULTAGASAS, Nr.4( According to the superposition principe each iquid type transducer can be represented as a number of norma force point sources, acting in imits of transducer s aperture on the surface of haf-space. The different types of transducers (straight beam, ange, focused and other are modeed by the corresponding ampitude and phase distribution of forces in aperture imits. For DPC transducers and EMATs the force can have tangentia or norma vector with regard to the surface of haf-space. The paper [4] represents the theoretica cacuation of ongitudina and shear wave shift (Fig. 1, excited at an arbitrary point of a haf-space, for SATs of different types: DPC transducer with perpendicuar vibration of type, DPC transducer with tangentia vibration of wear tip and for rectanguar piezoeement acting with norma force. The cacuations are made for D mode, and then using Smirnov-Soboev method were transformed to 3D mode. For a point source of a norma force the foowing equations of ongitudina and shear shift components were obtained: i k FT z k e Ur ( k k sin θ, μ π W( k U z = Ur ; (1 3 F i k cos θ T z k e Ur k k sin θ, μ π W( k U z = Ur. In spherica coordinates the dispacement in radia direction n r (ongitudina waves is given by U = U = U r + U z F i k T z k. ( e ( k k sin θ μ π W ( k In tangentia direction n r θ (shear waves: U = Uθ = Ur U z F 3 i k T z k e. (3 k k sin θ μ π W ( k For a point source of tangentia force the foowing dispacement components equations are vaid: 3 FT x k sin θ U cosϕ r μ π W ( k k k sin θ U z = U r ; i k e 4 F i k cos(θ cos θ e T x k U cosϕ r, μ π W ( k U z = U r. In spherica coordinates the ongitudina waves dispacement in radia direction n r is given by:, (4 U = U = U r + U z F 3 i k T x k e cosϕ k k sin θ μ π W ( k (5 The shear waves in tangentia direction n r (not accounting θ SH poarization dispacement: U = Uθ = Ur U z F 4 i k T x k ϕ cos (θ e. (6 cos μ π W ( k For D task with SH poarization the dispacement ampitude of ongitudina wave (vector ength, detected as a square root from squared projections sum is determined by the vaue (received from Eq. above U = U. For a shear wave U = Uθ + Uϕ F 8 i k T x k θ. (7 cos ( e cos θ cos ϕ + sin ϕ π μ W ( k θ sin For square source of a norma force on the hafwave surface were cacuated the foowing equations of dispacement components for ongitudina and shear waves in spherica coordinates: U = U = Ur Uz P 0 S π μ F ( k n пр k ( k k W ( k a cosϕ F n sin θ ( k Uθ = Ur U z i k e b sinϕ 3 P0 k k k sin θ Sпр (9 π μ W ( k i k e Fn ( k a cosϕ Fn ( k b sinϕ. These equations aowed anayze characteristics of SAT and antenna arrays. For matrix antenna arrays buit from SAT with DPC in the frequency range khz (which are appicabe for concrete and composites testing were anaysed the 3D images of directivity patterns for ongitudina and transversa waves using SATs with DPC of tangentia (Fig. and norma (Fig. 3 wear tip vibration. а b Fig.. 3D directivity pattern for SAT with DPC with a norma vibration of wear tip: а for ongitudina wave; b for shear wave ; (8 13

3 ISSN ULTAGASAS, Nr.4( а b Fig. 3. 3D directivity pattern for SAT with DPC with a tangentia vibration of wear tip: а for ongitudina wave; b for shear wave Using SATs with DPC with a tangentia type of vibration gives new possibiities for NDT, providing sending and reception of shear waves in non-metaic testing objects without coupants (dry contact. The tota number of eements and configuration of the antenna array depend on the necessary atera resoution and reation of signas to non-correated noises with correation radius γ cor. The atera resoution of antenna array, focused in a point, does not depend on the way of focus creation and is defined by the ange θ, under which the aperture A is seen from the point of geometrica focus: λ z d 0 f = λ. (10 θ sin A For the aperture A with the foca point diameter d f and the distance to the aperture side from focus point z 0 the number of eements in the antenna array wi be given by the foowing equation: z n = A = λ 0. (11 rcor d f rcor For non-destructive testing of ong objects, such as pipeines, rais, roing pates and other, antenna arrays from SATs with DPC, phased aong the surface, are appicabe (Fig. 4. For SATs with DPC with a tangentia vibration of the wear tip for θ =90 Eq.7 wi transform to the function of directivity versus the ange ϕ : F i k T x e U = sinϕ. (1 π μ changes from 90 to 0º the eve of SH-wave fas according to the sinusoida aw. The inear equidistant chain from n eements forms the additive antenna. The phase condition of such antenna array for puse signas is the providing of the signa time deay dt when sending and receiving by one eement: Δ dt =, C where C is the veocity of shear waves. The directivity pattern equation for inear continuous antenna arrays with the base ength B in far zone wi be the foowing: πb sin sin( ϕ λ U ( ϕ =, (13 πb sin( ϕ λ where λ is the shear wave ength; ϕ is the ange between the antenna axis and the required direction on the surface of a hafspace. Further we sha anayze the possibiities of optimization of inear arrays parameters for meta testing (Fig 5, buit as a inear set of simiar rectanguar SATs. Fig. 5. Linear antenna array Basing on Eq. 8 and.9 were obtained the fied characteristics for eastic parameters, corresponding to stee, and for eement size a=0, mm and b=15mm at main frequency f=,5 MHz. Let us determine the optima size of eement a in area of focusing according to Eq.9. Fig. 6 represents D dependence graph of the normaized modue of shear wave as a function of two variabes: a and propagation direction ange - θ at ϕ = 0. Fig. 4. SH-wave for guided wave testing At ϕ = 90, that means in the direction of y axis, is the maxima excitation of SH-wave, when the ange ϕ Fig. 6. Dependence of shear wave norma vaue modue as a function of two variabes - width of the eement a and ange θ at ϕ = 0 It is found that at vaue of a ess then 0,6 mm the shear wave eve reduction wi not be more then 6 db. The 14

4 ISSN ULTAGASAS, Nr.4( wear pate wi worsen the reation of ongitudina and shear waves eves, its optima thickness p shoud be found experimentay. Fig. 7 represents the graphica image of dependence of shear vibrations modues as a function of parameters b and ϕ at θ = 50º, corresponding to the direction of the pattern maximum. Basing on this dependence and on methodoogica aspects the parameter b for eement of antenna array can be 15 mm. Estimation of resoution parameters can be made using Eq.10 for a near fied zone and Eq.13 for a far fied zone. Fig. 7. Dependence of shear osciations asa function of parameters b and ϕ at θ = 50º For reconstruction of interna structure of the object under a test with antenna arrays SAFT-C agorithm is impemented. The idea of this agorithm is in coherent accumuation of signas, corresponding to the definite areas, at the condition of existence of non-correated echosignas. In case of two-dimensiona matrix antenna array for the point F in a hafspace x f, y f, z f the normaized refection coefficient wi be cacuated by the foowing equation: I F 1 = M j m im j= 0 i= 0 A( r, r U i j t i, j 0 + r i + r c j, (14 where i the number of the sending eement; j is the number of the receiving eement; A( r, r weight coefficient, showing the infuence of the directivity pattern for sending and receiving eements; U i, j ( t time puseecho reaization for the corresponding pair of eements; t 0 i j time of constant hardware deay; ri, r j distance from sending and receiving eements to the focus point F; с utrasonic wave veocity; M = im jm tota number of used echo-signas reaizations. For 3D reconstruction of a haf-space area, imited by x m, y m, z m, the genera equation for cacuation of refection coefficient set (3D image wi be the foowing: I F ( x, y, z = j m im y m xm zm 1 ri + rj =. A( ri, r j U i, j t0 + M j= 0 i= 0 y= 0 x= 0 z= 0 c (15 The reconstruction step shoud not exceed λ 4 to avoid oosing the defects, therefore the number of operations for reaization of this agorithm wi be the foowing: 64xm ym zm N op = M 3 χ = 64MV f c 3, (16 where V the voume of testing area. The number of operations is the group of cacuations for one point in the space and from one reaization. For concrete testing with the antenna array, consisting of 36 SAT shear wave eements (i m = 36; j m = 36, with operation frequency f = 50 khz, and at a reconstruction area of 1 m 3, (utrasound veocity in concrete 700 m/sec the number of operations wi be N op = For testing of stee weds the one-dimensiona antenna array is appicabe and the reconstruction of one B-scan (cross-section is made. In this case the equation for efficiency wi have the foowing view: f N op = 16MS, (17 c where S is the area of crossection of reconstruction. The number of eements in the antenna array is 3 (i m =3; j m = 3; operating frequency f =,5 MHz, reconstructed area 1000 mm, shear wave veocity 350m/sec. The number of operations wi be a b c Fig. 8. Directivity patterns of transducers with DPC: a with norma vibration of the wear tip; b with tangentia vibration of the type, section aong the vibration vector; c with tangentia vibration of the type, section perpendicuar to osciation vector; 1 ongitudina waves; shear waves 15

5 ISSN ULTAGASAS, Nr.4( N op = 9, For weds a rea-time tomography it is necessary to form not ess then 5 images pro 1 sec, which is due to a sma size and ow power consumption of handhed means is possibe with the use of speciaized processors. To estimate the rea characteristics of transducers with DPC the measurements of parameters and directivities patterns of transducers in a puse mode were made. Anaysis of the echo-signa shape and spectrum characteristic for TD0 transducers type with tangentia vibration of wear tip (manufactured by Acoustic Contro Systems, ussia showed spectrum maximum at the frequency of 55 khz and width of the spectrum 65 khz at the eve 6dB, which is corresponding to the reative bandwidth of 118%. The simiar characteristics have SATs with DPC with a norma vibration of the wear tip (LD0 type, due to simiar construction and high damping. The coefficient of doube eectro-acoustic conversion for SATs with DPC of TD0 type is 70 db. This parameter is db ess then for the transducers with a iquid contact type. Fig. 1 represents the measurements resuts of directivity patterns for SAT with DPC of TD0 and LD0 type transducers with tangentia and norma vibrations of the wear tip correspondingy. Measurements were made on the concrete haf-space 0.3 m in radius made from cement 400 and granite fiing (size does not exceed 8 mm. The experimentay obtained resuts fuy correspond to theoretica modes with accuracy up to 5%. The anaysis of absoute signa eves, obtained with SATs with DPC of two types in a soid body shows that the efficiency of sending and reception of shear waves is by 10 db higher in comparison with ongitudina waves, if the SATs with tangentia vibration of the wear tip are used. To estimate the reation of informative signas to noise for puse-echomethod of concrete testing the eves of the backwa signas and structure noise, surface waves of, L and SH types on the concrete mark 400 with granite fiing (15 mm sized were measured for SATs with DPC of TD0 and LD0 types. The signas of surface waves were registered directy after pacing SATs on the testing object surface at different distances. The eve of backwa signas was estimated by signa ampitude, received with using through-transmission method on different thicknesses. The effective vaue of structura noise σ n was cacuated from the statistica processing of arge massive of non-correated reaizations. Comparing the obtained resuts the foowing concusions can be made: the eve of the backwa signa is 10-1 db higher than the structura noise eve for shear wave than for ongitudina waves. As the theoretica investigation of SATs with DPC and experiments showed the shear wave is excited more efficienty than the ongitudina and the structure noise eve does not depend on the direction of the excitation force, because it is appearing due to mutipe re-refections and transformations of utrasonic osciations. Basing on the obtained resuts we can concude that for puse-echomethod of concrete testing the shear waves, formed by SATs with DPC with tangentia vibration of the wear tip are more effective. At that the average backwa signa-to-noise ratio can be from 0 to 10dB for shear wave, and for ongitudina waves this ratio is 10-1 db worse. For quantitative estimation of structure noise parameters the correation radius was used. The correation radius is the size of minima circe area on the surface of haf-space inside of which the crosscorreation coefficient between echo-reaization of structura noise received from any point inside the area and echo-reaization in the center of the area is not ess then 0,5. Basing on the investigation resuts the foowing requirements for antenna arrays appicabe for thickness gauging and tomography of concrete were formuated: For thickness measurements of widey-spread concretes (marks the sufficient is the antenna array from 4 eements of SATs with DPC with tangentia vibration of the wear tip (simiar to TD0 by eectroacoustic parameters. These transducers are arranged in groups of 1 eements for sending and receiving and are paced in one housing. The step between SATs is 0 mm. The view of such antenna array and backwa signas, received with the antenna array on the concrete bock 400 mm thick are represented on Fig. 9. The upper backwa signa was received in the area of monoith concrete and the ower signa received in the area with the hoe 30 mm in diameter. The concrete thickness measurement error on is 7% at the error probabiity of 0,97. Fig eement antenna array buit from SATs with DPC for concrete thickness measurement and received echo-signas For the tomography of concrete structures the antenna array consisting of 36 SATs with DPC arranged in a square matrix 6 x 6 was deveoped. As eements the SATs with tangentia vibration of the wear tips with the operating frequency 55 khz were used. Each eement has own ampifier and generator and has an independent spring oad to the testing surface. The controing board aows independent use of every eement both in sending and receiving mode. Simutaneousy can operate ony a pair of eements. The received signas are digitized and sent to a PC. Using the antenna array and data processing with the SAFT-C agorithm we can reconstruct tomograms of B- type, representing the possibiities of the puse-echomethod for concrete testing. For trias we used a concrete bock (concrete mark 400 with a midde size fiing (15 mm. The thickness of the bock is 400 mm. Fig. 10 represents 16

6 ISSN ULTAGASAS, Nr.4( the resuts: 1 image of the sphere 100 mm in diameter inside the bock; image of the sphere 50 mm in diameter inside the bock; 3 the backwa image. Fig 17 b represents the reconstruction of the cross section of channes inside the bock: 1 a channe 30 mm in diameter at the depth 50 mm; a channe 1 mm in diameter at the depth 30 mm; 3 - a channe 30 mm in diameter at the depth 350 mm behind the channe ; 4 backwa. For the case 3 (Fig. 17b the signa / noise ratio is ess then 10 db. Fig. 10. Tomograms of a concrete bock with interna artificia defects, obtained after testing with 36 eement antenna array The experiments made aowed to confirm the appicabiity and efficiency of the antenna array from SATs with DPC for soving different tasks of concrete testing in range of thickness mm. At that the operation using shear waves is more sensitive and gives a higher resoution. Basing on utrasonic the transducers with DPC and shear vibration of wear tip the foowing equipment was deveoped: the ow-frequency faw detector for concrete A10 MONOLITH and the tester UK1401 [7]. Fig. 11 represents the process of testing the contact ine support at the Moscow aiway using the utrasonic tester UK1401. The instrument has two buit-in transducers fixed on the base 150 mm. The UK1401 tester aows measuring time or veocity of utrasound propagation in a materia using surface sounding method with an error of not more then 1%. It can be used for estimation of concrete strength by changes in utrasound veocity in materia. Aso, it aows to estimate the crack depth for the cracks coming to the surface, in the range of depths mm. Fig. 11. UT tester UK1401. Testing of contact ine support The transducers with a ongitudina vibration of the wear tip can be used for measuring of the ayeigh wave veocity in materias at surface sounding of materias. The short signas of these transducers aow using them for estimation of integrity of materias and presence of defects inside, ocated aong one coordinate axis. If the waveength is more then the atera size of the object, then this object can act as a wave guide and different types of core waves are propagating on the ong distances. The exampe of such appication of the transducers is puse-echomethod of testing the state and ength of stee anchor bots buit in concrete. Fig. 1 represents two osciograms, received with a pair of transducers with shear vibration of the wear tip on the modes of anchor bots 1 m ong and 30 mm in diameter. The transducers were set near each other on the side of the bot near one end and the vibration vectors were oriented across the bots axis. The upper signas in Fig. 1 a were received on a free ying bot, showing absence of a contact between the bot and concrete. The signas in Fig. 1 b were obtained on the bot buit in concrete, when ony 50 mm of bot were eft above the concrete. The significant difference of signas character gives information about the quaity of the contact between the bot and the concrete. The deay time between the signas gives information about the bot ength or ength of its non-damaged part. Fig. 1. Echo-signa osciograms received on anchor bot end: (a free ying bot; (b buit-in concrete bot Guided wave faw detection of rais The guided wave faw detection of rais at owfrequencies can be appicabe for testing without the necessity of scanning the whoe surface of the object. The rais head, web and foot in this case are acting as separate independent waves guided. The ongitudina (symmetric, fexura by thickness (asymmetric and SH-waves are propagating in them. The utrasound veocity propagation was measured by the through-transmission method using a pair of SATs with DPC (TD0 type perpendicuar to the rais axis. For sounding the rais on the base of 1500 mm and more the veocity is (3090 ± 10 m/sec, which is ower then the shear wave veocity and can be expained by the guided wave propagation of utrasonic signa in a rai. The resuts of signa spectrum measurements showed that the time deay interva of about 00 μs from the moment of the signa reception is characterized with a dominated spectrum in the range of khz. To estimate the possibiities of the guided wave method we carried out the physica modeing of 8 eement inear phased antenna array (eements of TD0 types [8]. 17

7 ISSN ULTAGASAS, Nr.4( The experiments were made of a rai 590 mm ong with an artificia defect of a gash type (5 x 5 mm, which is 15% of the cross section of the rai, at the distance of 1000 mm from the rai s end. The distance from the end of antenna array to the rais butt-end is 00 mm. The resuts of experiments showed that the signa peak ampitude from the defect (maximum at 70 μs exceeds the of noise eve of 15 db and in comparison to the ampitude from the butt end is 5-7 times ower. The guided wave method aows detecting defects ike cross cracks in rais head with a size of about 15% area of the rai head cross section and more. To estimate the maxima possibe testing distance the specia phased antenna array from 1 eements with DPC for guided wave testing was deveoped and tested on the rais up to 5 meters ong. The informative signas spectrum ies in the range 10-5 khz. The reation between peak signas from the butt-end of rai to the noise eve exceeds 30 db. The equivaent utrasound veocities are 94, 933, 91 and 907 m/sec for distances 5, 10, 15 and 0 m correspondingy. The difference in veocities is not significant so the average veocity 90 m/sec was used for testing. The signa eves from the rai s butt-end were measured versus the distance. The resuts are presented in Fig. 13 as interpoated dependence of the signa versus the distance to the butt-end. Ampitude, V 0 Distance, m Fig. 13 Echo-signa ampitude from the rai s butt-end versus the distance between the antenna array and the butt-end From the resuts of the experiments it can be concuded that the guided wave method can be reaized with inear antenna arrays, buit from SATs with DPC with tangentia vibration of wear tip. The number of eements in antenna array can vary from 8 to 1. The operation frequencies are in the range khz. The optima osciation mode propagation veocity is 90 m-sec. The dead zone is not more then 500 mm. Such antenna array aows detecting defects with cross section area ess the 15% of section area of guided wave at the distance up to 0 m with the signa/noise ratio not worse then 10 db. Due to use of synthetic focusing it is possibe to contro the testing direction. It provides two directiona scanning from the pace of antenna array and therefore increasing efficiency of rais testing. These resuts were used when deveoping the guided wave faw detector for rais AK14, presented in Fig.14. In comparison with the known equipment for faw detection this faw detector soves more efficienty the probem of ocaization of defects at the distance 0.5 to 30 meters from one set of antenna array with accuracy 0,1 m. The device was tested and impemented in rai weding factories and departments of ussian aiways. Fig. 14. ais testing process with the guided wave faw detector AK 14 Utrasonic thickness gauges for testing of metas One of the most widey spread non-destructive testing procedures of metas is thickness measurements of the objects, providing correspondence of the required sizes at production and finding of deviations from thicknesses during expoitation in critica conditions ike high temperature or high pressure, in a corrosive environment. Using the agorithm of autocorreation data processing it is possibe to avoid the infuence of therma and reverberation noises and to determine the period of mutipe signas repetition and therefore cacuate the thickness of the object under a test. In order to investigate the metroogica characteristics of this measuring method the data set was created using the set of standard bocks from AMG-6 aoy (KMT 9р with the highy damped straight beam singe crysta transducer S3567 (produced by Acoustic Contro Systems, Ltd., ussia [8]. The absoute error of measurements in this case with autocorreation function agorithm in the thickness range 0,8 0 mm is not more then 13 μm, which is 3,8 time better then in comparison with measurements made by the doube crysta transducer П11-10,0-6/ and V-correction in the thickness gauge type А109. The main advantage of the proposed method of acoustic signas processing is the possibiity of soving the probems of thickness measurements using non-coupant method of EMA transduction. The investigation carried out showed the efficiency of processing signas from EMAT, which aows the measurements of smaer thicknesses up to 0,5 mm. For the tasks of thickness measurements the foowing instruments were deveoped: A107 and A107C sma size portabe utrasonic thickness gauges with an easy, user-friendy interface, high sensitivity for express measurements of thickness on stee; A108 universa thickness gauge of wide appication for wide thickness range and wearproof transducer for operation on rough 18

8 ISSN ULTAGASAS, Nr.4( surfaces at operating temperatures from 30 up to +55ºС, A109 universa thickness gauge for a big number of measurements with possibiity of data storing (Fig. 15. Fig. 15. Digita utrasonic thickness gauges А107, А108, A109 A thickness gauges have Certificates of Type Approva [5, 8]. EMA thickness gauge A170 [6, 11] is appicabe for thickness measurement of roing pates, cyindrica and spherica objects after stamping, miing and etching in thickness range 0,5-100 mm, the minima possibe curvature radius at that is 30 mm and the aowed error of measurement is not higher then 0,01 mm (Fig. 16. The EMA transducer is made using the nonvoatie constant magnets from Nd-Fe-B aoy, which made it possibe to create sma, portabe, ow power consuming thickness gauge. have showed that the spectrum has maximum at the frequency of 1,8 MHz and the spectrum width 1,0 MHz at the eve 6 db, which corresponds to the reative bandwidth of 55%. Measurement of directivity pattern for a singe highfrequency SAT of the antenna array for ongitudina and shear waves was made on the speciay made stee sampes with side hoes 6 mm in diameter, ocated at the same distance but under different anges with respect to the pacing of SAT. The resuts are presented in Fig. 17, where 1 directivity pattern of ongitudina wave SAT, - directivity pattern of shear wave SAT. Fig. 17. Directivity pattern of ongitudina and shear waves for a singe high-frequency SAT of antenna array with a iquid contact Fig.16. Process of thickness measurement The agorithm of data processing aows searching mode and indication of the smaest thickness vaue for the testing object or of its part. The resuts of measurements can be saved in a nonvoatie memory of the device and transferred to the externa PC through USB port for further processing, printing and storing. The deveopment of the portabe EMA device for acoustic measurements with one-side access aows estimation of anisotropy of materia and estimation of deformation mode of units and parts of structures [11]. Utrasonic detection of faws in weds using digita technoogies For optimization of a high-frequency antenna array parameters for weds testing the experiments of the test mode of the antenna array with the foowing parameters were made (Fig 5: a = 0,6 mm, Δ = 1,5 mm, b = 15 mm, the number of eements 18 with a ceramic wear pate (type XC 0.8 mm thick. A eements are damped [10]. The parameters of a the eements are identica. The investigations The resuts showed that the singe SAT with the size 0,5 x 15 mm forms puses of two wave types: ongitudina and shear, which confirms the possibiity of excitation SH waves with an antenna array without anguar prism. The correspondence of their eve with the accuracy up to 30% is the same as obtained by cacuations, which is 0,5 of the maxima ampitude of the ongitudina wave. The width of directivity pattern main obe is the same as was cacuated. The experimenta tests of the inear antenna array for tomography of metas using ongitudina and shear waves were performed with the mode of the antenna array on the caibration bock SO-. After processing of the signas picked up on this bock, the tomogram of the cross section area with a hoe 6 mm in diameter ying at the depth 44 mm was reconstructed using the SAFT-C agorithm (Fig.18. For reconstruction the term A( ri, r j of Eq.15 was taken as 1, at that on the tomogram (Fig. 18 a it is ceary seen both the image of the hoe formed by shear waves (on the right and the image of the backwa formed by ongitudina waves (on the eft. Fig. 18b presents the tomogram of the interna structure of the auminium bock with severa side hoes mm in diameter, ocated on the circe side 44 mm diameter. The antenna array was paced in the midde of this circe on the surface of the bock. When using the correcting directivity pattern of eements on the tomogram (Fig. 18b, it is possibe to see the maxima number of defects. 19

9 ISSN ULTAGASAS, Nr.4( The experiments confirmed the suitabiity of the antenna array buit from SAT with a iquid contact type for testing a meta structures and weds. For producing the array it is optima to use piezo-composite ceramics with the step of eements 0,8 mm, thickness of eements not more then 0,4 mm and the wear pate thickness not more then 0,5 mm. Expert, which can operate in the temperature range starting from -30º С and the utrasonic tomograph A150 with a inear antenna array (Fig19. Fig. 19. Digita utrasonic faw detectors A11 MASTE, A114 EXPET a A these instruments were speciay designed for operation both in aboratories and in fied conditions, using the conventiona methods of utrasonic non-destructive testing. A these instruments possess buit in arge configurations ibrary for quick adjustment of the device under different transducers and different operating modes for easier data anaysis. Besides the deveopment and production of modern equipment for non-destructive testing a great attention in the Scientific esearch Institute of Introscopy SPECTUM is devoted to raising the ski eves of speciaists in NDT customers and users of the equipment. There is a specia study center in SPECTUM, providing studies and trainings in different fieds of NDT and issuing certificates of I, II and III eves speciaists of the internationa quaification. There is aso informationa and technica support, consutancies on appication of the equipment, upgrading of systems and repair and post-saes service provided. eferences b Fig. 18. econstructed with SAFT-C tomograms, buit on a test sampe SO- and on sampe from auminium aoy 90-95% of weds are tested with a portabe handhed utrasonic equipment. In most cases NDT of metas is performed in fied conditions or hard-to-reach areas, therefore the sma size, but most functiona devices are more and more demanded. The distinctive features of handhed utrasonic faw detectors and tomographic systems, produced by Scientific esearch Institute of Introscopy SPECTUM [6-11], is the fuy digita channe, which enabed to unify the functiona circuits and design soutions, speed up the new deveopments and widen the spectrum of utrasonic transducers and antenna arrays, which can operate with the devices. Among the devices of wide appication the company produced the sma and ight utrasonic faw detector A11 Master and the utrasonic faw detector A Non-Destructive Testing. Handbook in 7 voumes. Edited by Member of AS V.V. Kuev. Moscow: Mashinostroenie Vo.3. P Lange Ju. V. Acoustic ow-frequency methods and means of nondestructive testing for sandwich type structures. M.: Mashinostroenie P Dzenis V. V. Appication of utrasonic transducers with point contact for Bob-Destructive Testing. iga: Zinatne P Daniov V. N., Samokrutov A. A. Modeing of piezo-transducers with dry point contact operation in sending mode. Defectoscopy Samokrutov A. A. Modern utrasonic equipment for Non- Destructive Testing of structures from metas. Metaurgist P Samokrutov A. A., Bobrov V. T., Shevadykin V. G., Kozov V. N., Aekhin A. G., Zhukov A. V. EMA thickness gauge for aerospace industry. XVI ussian Scientific Conference Non- Destructive Testing and Diagnostics. St.-Petersburg, 9-1 September 00. Book of abstracts. Abstract Shevadykin V. G., Samokrutov A. A., Kozov V. N. Utrasonic ow-frequency short puse transducers with dry point contact. Deveopment and Appication. Internationa Symposium NDT-CE. Berin Sept Kozov V. N., Samokrutov A. A., Shevadykin V. G. Utrasonic thickness measurement by mutipe echo-signas. Testing. Diagnostics P

10 ISSN ULTAGASAS, Nr.4( Gurvich A. K., Kozov V. N., Samokrutov A. A., Shevadykin V.G. Non-destructive testing of rais in case of guided waves use. 16 th Word Conference on Nondestructive Testing. Montréa, Canada. August 30 September 3, 004. Book of Abstracts. TS P Samokrutov A. A., Lutkevich A M. Weds utrasonic tomography based on phased antenna arrays with sma-aperture transducers. 16th Word Conference on Nondestructive Testing. Montréa, Canada. August 30 September 3, 004. Book of Abstracts. TS P Samokrutov A. A., Aekhin A. G., Ivchenko V. V., Bobrov V. T. Industria wa thickness testing of rocket airframe paneing for POTON. 3rd Internationa exhibition and conference Non- Destructive Testing and Technica Diagnostics in Industry, Moscow March 004. Book of Abstracts. P. 45. A. Samokrutov, V. Shevadykin, V. Bobrov, V. Kozov Akustinių neardomųjų bandymų metodų ir šiuoaikinės skaitinių įrenginių gamybos technoogijos tobuinimas eziumė Tiriamos akustinės sritys, suformuoti normuotieji kontroės šatiniai. Pasiūyti utragarsinės kontroės metodai, panaudojant sausojo kontakto keitikius. Tiriami ir eektromagnetiniai akustiniai keitikiai. Pateikti skeidimo mutikeitikių tyrimų rezutatai, įvertinti apibrėžtų uždavinių sprendimo pavyzdžiai, norint patikrinti konkrečias struktūras, pavyzdžiui, geežinkeio bėgius, suvirinimo vietas ir kt. Pateikta informacija apie naują šiuoaikinę skaitinę įrangą, kurioje informacinės technoogijos dar abiau ištobuintos. eceived