Showing papers on "Ultrasonic testing published in 1975"

Laser generation of ultrasonic waves for nondestructive testing

Abstract: An object is tested for thickness or for presence and location of flaws by impacting a pulsed laser beam on the surface of the object so as to generate ultrasonic waves by rapid heating of a thin surface layer thereon. The reflected ultrasonic echo in the object is detected by monitoring surface motion with a rough surface interferometer.

Ultrasonic pipe testing system

Abstract: An ultrasonic inspection system for providing volumetric testing of circumferential welds in piping or other structural shapes of regular cross section. The inspection system permits inspection in longitudinal, circumferential shear, and axial shear modes and is characterized by having a carriage mountable on the pipe to be inspected with remote control of the position of the test head and remote gathering of data. This system is readily adaptable to the needs of the nuclear industry for inspecting pipes exposed to radiation from a remote location. A further feature of the invention encompasses a flexible boot covering the transducer, the boot being pressurized with a liquid couplant for providing ultrasonic coupling through the pressurized couplant between the object and the boot.

Ultrasonic diagnostic inspection systems

Abstract: An automatic ultrasonic inspection system for automatically testing billets by the pulse reflection type of inspection and further utilizing an ultrasonic transducer for thru-transmission of energy for automatic distance-amplitude correction and including indexing means having an angular scan encoder and an axial scan encoder such that reflections obtained indicative of defects are accurately correlated with their three dimensional positions in the billets. A defect gate receives the reflections through the billet and if a defect meets a preset criteria such defect information is displayed and passed to a computer wherein the position of the defect is stored. The computer can provide various outputs such as alphanumeric-graphic display or printed outputs.

Method of ultrasonic echo flaw detection and device for effecting same

Abstract: In the course of checking an article, there are directed at the point on the article being checked, whereat ultrasonic oscillations generated by an ultrasonic flaw detecting transducer are applied, pulses of ultrasonic oscillations focused at this point, which pulses are sent by a side focusing ultrasonic transducer. The ultrasonic oscillations reflected from the surface of the article, in the form of a divergent beam, are received by two receiving ultrasonic transducers. The received ultrasonic oscillations are compared to obtain a difference signal; a detector head housing is then turned, depending on the magnitude and sign of said difference signal. As the difference signal disappears, the axis of the detector head housing becomes directed along a line normal to the surface of the article and the device serves for ultrasonic echo flaw detection and is provided with apparatus for maintaining constant the distance between the ultrasonic flaw detecting transducer and the surface of the article being checked; it also has apparatus for the orientation of the detector head, which slides over the surface of the article, around the point at which ultrasonic oscillations are applied, and for a deflection of the ultrasonic flaw detecting transducer from the normal by an angle to direct the ultrasonic beam refracted in a line material of the article along a line normal to the surface of the flaw.

Alignment of ultrasonic transducer probe in pulse-echo testing

Abstract: This invention refers to an ultrasonic pulse-echo nondestructive test method and apparatus for causing the axis of an ultrasonic energy search beam path transmitted from an ultrasonic transducer probe to a workpiece to be maintained normal to an irregularly contoured workpiece entrant surface. Electrical circuit means measure and compare the echo signals reflected from the workpiece and cause the search probe to be positioned to maximize the amplitude of the received signals.

Focussing Ultrasound Over a Large Depth with an Annular Transducer-An Alternative Method

Abstract: An alternative method is described for focussing ultrasound over a large depth. The method is useful in B-scan. The final echo signal is obtained as the s u m of two partial echo signals and different segments of an annular transducer are used for transmission and reception of the two partial echo signals. The advantages with respect o a method described previously are simplicity and a higher dynamic range. A lateral resolution of 2 mm is obtained which is almost an order of magnitude better than conventional B-scan. Scans of fetuses in virfo are shown. THE INTRODUCTION 4 E-scan is a technique which is widely used in medical ultrasonic diagnosis and which gives a picture of a cross section of the body (for a short review of B-scan operation see, e.g., [1,2,3]). B-scan has a good longitudinal resolution but a bad lateral resolution, because an unfocussed or only weakly focussed beam is used. It is possible to focus the beam with a large aperture and obtain good Iateral resolution but only over a limited depth of focus. It was shown in Ref. [S] that focussing wit’h an annular t,ransducer gives good lateral resolution over a large depth. Basically this is so because on every point of the axis the contributions of all elements of the annulus add up in phase and give a large amplitude, whereas outside the axis they do not add up in phase. When the beam is focussed with an annular transducer one obtains rather large sidelobes. A method was demonstrated in Ref. [3] for reducing these sidelobes. This method works as follows. The annular transducer is built out of several segments. Manusrript received April 10. 1974; revised June 17, 1974. The authors are with F. Hoffmann-La Roche & Co., AG, Bssel, Switzerland. For a first ultrasound pulse all segments transmit and receive in phase. The echoes so received are stored. For a second pulse, the phase of the pulse transmitt’ed by each segment is made proportional to the angular position of the segment on the ring. On reception the signal received by each segment is multiplied by a phase factor which has the same magnitude but opposite sign as the phase factor of the transmitted pulse. The echoes received from the second pulse are then subtracted from the stored echoes of the first pulse. It. was shown that the following point spread function b ( r ) can be obtained with this method where Jo and Jz are Bessel functions of the zeroth and second order, respectively, R is the radius of the annular transducer, r is the distance of the point reflector from the axis, X is the sound wavelength, and d is the distance between transducer and reflector. The arrangement is illustrated in Fig. 1. In the present paper we will describe a different method for reducing the sidelobes and obtaining the same point spread function as in Eq. ( 1 ) . The new method has the advantages of greater simplicity and of a larger dynamic range. These advantages will be elaborated upon at the end of the next sect’ion. NEW METHOD FOR SIDELOBE REDUCTION The new method will be explained for an annular transducer built out of eight segments and is illustrated in Fig. 2. The segments drawn black transmit sound whereas 12 IEEE TRANSACTIONS ON SONICS AND ULTRASONICS, JANUARY 1975 the Fourier transform of the amplitude distribution on to the width of a segment shown in Fig. 2 and not with respect to the diameter of t,he ring. Additional comment on this is given in Ref. [S].) The contribution ak(r,cp) due to the term exp ( jkcp) is [3,4] NNULAR TRANSDUCER the ring. (Note hat we are only in the far field with respect adr,cp) = exp [jk 6 + v)] Jk (d) . (3) 2 ~ R r FOINT R E R E C r O R J k ( S ) is the Bessel function of the kth order and the other 1. symbols are the same as in Eq. ( 1 ) . \\ Fig. 1. Perspective view of the annular transducer. We therefore obtain for the total amplitude 1. PULSE 2 . PULSE a(r,cp) = +Jo (7) ; Jt (y) cos 2p 21rRr 2 27rRr + Js (y) cos6cp + (4) 2sRr 3* because J k ( S ) = Jr ( m ) for k even. In an analogous way the sensitivity s(r,(p) to a sound source at r and cp for the segment’s shown as receiving in Fig. 2. Transmitting and receiving segments for the first and Fig. 2 is computed as second pulse. Black: transmitting, White: receiving. s(r,cp) = ~ J o (7) + ; J Z (7) cos 2cp 21rRr 2 2aRr 2 27rRr 3* J J S (7) cos6cp f * S * . (5) 0 d 2 n %l2 2n c4 The echo amplitude bl(r,cp) of a point reflector is obtained Fig. 3. Transmitted amplitude a t l (q ) for the first pulse a functhe product’ Of Eqs. (4) and (5) tion of angle ‘p on the ring. 2xRr 4 2aRr bl(r,cp) = 2Jo2 (F) ,z J2’ (7) cos2 2cp the segments drawn white receive sound. Two pulses are used for the sidelobe reduction and between the two pulses J Z (T) J S (7) cos 6cp cos 2cp the configuration is “rotated” by 45’ (by electronically switching on and off appropriate segments), as is seen + . . . . . . ( 6 ) in Fig. 2. The partial echo signals of two pulses are added in order to btain the final echo signal. For the second pulse we obt,ain the echo amplitude We will now analyze this method. The transmitted amplitude atl(cp) on the ring during the first pulse is shown bz ( r , cp ) = 1 ~ ~ 2 (T) 2rRr 4 J ~ Z (T) sin2 zcp in Fig. 3 as a function of angle cp. The maximum amplitude 2 ~ R r 21rRr 3??

Sector scanning ultrasonic inspection apparatus

Abstract: This is an ultrasonic transducer scanning support system comprising at least three arms serially joined in pivotal relation one to the other and to a base. Three position transponders are mounted on the base with each of the pivoted arms operatively coupled to a transponder whereby signals are developed representative of the position of a transducer mounted on the end of the third arm which control the origin of an indicating means to correspond to the position of the transducer.

System for Visualizing and Measuring Ultrasonic Wavefronts

Abstract: A system for the measurement and visualization of ultrasonic wavefronts is described that features high sensitivity and acoustic wavelength limited resolution over apertures up to 15 cm in diameter and at frequencies up to 10 MHz. It operates by interferometrically detecting the motion of a thin, acoustically transparent metallized pellicle as the ultrasonic wave passes through it. The basic arrangement is that of the Michelson interferometer with the addition of an open loop method to stabilize the response and a deflection system in one leg of the interferometer to scan the pellicle.

Ultrasonic test method and apparatus utilizing scattered signals

Abstract: In a pulse-echo ultrasonic test arrangement the back reflected echo acoustic wave signal as well as the scattered longitudinal wave and scattered shear wave signals are utilized in an evaluation circuit for determining more accurately the characteristics of a defect in a workpiece. The evaluation circuit, most suitably, includes a digital computer which in a typical embodiment of the invention is programmed to provide by Fourier transforms the frequency amplitude spectrum and the frequency phase spectrum of the supplied three signals, hence producing six characteristic outputs for a particular defect.

Comparison of an acousto‐optic and a radiation force method of measuring ultrasonic power

Abstract: During the interim period while nationally acceptable methods of measurement of referential standards for ultrasonic power are being developed, comparisons are needed among measurment techniques currently used. This is particularly necessary for determining the acoustic power from ultrasonic medical devices. Such a comparison was made between an optical and a radiation force technique to measure the ultrasonic power output of a 1‐MHz 1‐in.‐diameter PZT crystal from 70 mW to 2.3 W total acoustic power. The optical technique follows the theory of Raman and Nath, assaying the diffraction of monochromatic light by ultrasound. In addition, a correction factor is introduced into the calculation of the phase retardation parameter and eliminates the need to determine the pathlength of the light through the sound. The radiation force technique relates the change of position of an air‐backed, self‐centering, reflecting float to the ultrasonic power. A linear regression analysis between the square of the voltage app...

Method and apparatus for adjusting defect gate in ultrasonic pulse-echo testing

Abstract: The present invention refers to a method of ultrasonic testing a workpiece by the pulse-echo technique and an apparatus therefor. An initial portion of a workpiece to be tested is conveyed past an array of electroacoustic transducer probes. The transit time through the workpiece of the transmitted ultrasonic signals from each probe comprising the array is measured. The maximum measured transit time is stored. Subsequently as a slightly shifted second portion of the workpiece is conveyed past this array of transducers, the transit time through the workpiece of ultrasonic signals transmitted by each probe of the array is again measured. The stored value is updated responsive to the latter obtained values. The final updated value is conducted to a flaw detector circuit for terminating a defect gate used in conjunction with testing the workpiece for defects by the pulse-echo test method.

Apparatus and method for ultrasonic inspection of highly attenuative materials

Abstract: An ultrasonic inspection system is disclosed which provides for penetration of highly attenuative materials by use of the longitudinal mode of particle vibration Separate transmitting and receiving transducers, which are electrically isolated, are utilized in the inspection system as are specially designed transducer wedges producing refracted longitudinal ultrasonic waves

Device for nondestructive ultrasonic testing of cylindrical parts

Abstract: Device for nondestructive ultrasonic testing of cylindrical parts, comprising a basin in which the part to be tested, for example a journal bearing provided with an antifriction alloy is immersed. The basin is mounted on a revolving plate having a gear driven by means of an inclined-tooth pinion. A vertically movable horizontal arm, depending upon diameter of the part to be tested, carries two piezoelectric transducers and an arcograph, the marking of the bonding fault area on the surface of the part to be tested being effected by means of an electric arc produced between one trace element of the arcograph, which receives a voltage signal from the monitor of a fault detector through the control assembly of the arcograph, and the inner surface of the part to be tested. The entire cylindrical surface is explored along a tangent of partially superposed helixes and the pitch of the helix is equal to, or smaller than the diameter of the piezoelectric transducer crystal.

Sled for ultrasonic NDT system

Abstract: An ultrasonic nondestructive testing system and a "sled" for use in such a system are provided for nondestructively inspecting a workpiece. The "sled" includes an ultrasonic search unit effective to radiate or transmit ultrasonic energy in response to a driving signal and to receive ultrasonic energy and produce a received signal corresponding to the incident ultrasonic energy. The sled includes a sealed chamber filled with a liquid couplant. A resilient, elastomeric diaphragm forms one side of the chamber and is adapted to slide along the surface of the workpiece. An ultrasonic search unit projects into the chamber so as to be acoustically coupled to the diaphragm. In addition, an elastomeric member having a high acoustical attenuation and an acoustical impedance corresponding to that of the liquid couplant is provided inside of the chamber for absorbing spurious ultrasonic energy.

Signal Processing in Nondestructive Testing

Abstract: Signal averaging has been used to improve the clarity of flaw indications in an electron beam weld. The delay of an electronic gate has been synchronized to the transducer motion to improve the detectability of a tight interface crack in a tensile specimen. Cross-correlation techniques and multiple transducer arrays have been used to improve the signal-to-noise ratio of artificial flaws in welded panels. Signal averaging has been used to reduce random noise in the through-transmission ultrasonic inspection of a honeycomb composite. Megacycle range ultrasonic flaw information has been recorded on a low frequency FM tape recorder by rapidly sweeping an electronic gate through the time interval of interest. A lock-in amplifier has been used to produce quantitative data in both single-coil and double-coil eddy current systems. Cross-correlation techniques and a multiple-coil eddy current probe have been used to reduce surface roughness noise in an eddy current crack detection system.

Ultrasonic inspection method of pulse reflection defect detection using a thru-transmission automatic distance-amplitude compensation

Abstract: An automatic distance amplitude correction device for automatically correcting for amplitude variations and signals caused by the attenuation of sound propagating through a test specimen wherein a signal is transmitted through a test specimen and the reflection is detected and furthermore, a through signal is detected after the signal has passed through the test specimen only a single time and utilized to provide improved automatic distance amplitude compensation.

Ultrasonic testing of seams

Abstract: The seam of a pipe is tested sequentially from various directions and with differently directed test beams to search for differently oriented defects, and repeatedly for stepwise testing each portion of the same.

Ultrasonic inspection apparatus for vertical members

Abstract: An ultrasonic inspection apparatus for use in inspecting drill pipe or like tubular members being tripped into and out of a well borehole comprises a planarly arranged set of ultrasonic search units, such as wheel search units, arranged on a frame suspendible within the well derrick and defining a vertical passage for the tubular member. Access is provided to the passage by the tubular member from a direction transverse to the longitudinal axis of the tubular member, for example, by providing an openable hinged frame. When in the passage, the search units are urged into contact with and are sonically coupled to the tubular member. The device is manually manipulable to engage and disengage the tubular member to facilitate inspection. A method of inspecting tubular goods on the floor of a drilling rig during a tripping operation is also provided.

Ultrasonic test method and apparatus for testing thick-walled workpieces

Abstract: The invention concerns an apparatus and method for ultrasonically testing thick-walled workpieces at an increased scanning speed by the use of a plurality of ultrasonic test probes wherein the probes are selectively rendered operable. The transmit probes are temporarily inhibited from transmitting search signals into the workpiece for a time interval during which the receipt of a defect responsive echo signal by a receive transducer is anticipated. The scan frequency is determined therefore by a clock circuit and the transmission of search signals is halted only temporarily for a brief period during which time there is no skipping in the predetermined transmitting sequence of the transducer probes.

High‐power, ultrasonic fatigue testing machine

Abstract: A machine capable of fatigue testing high strength alloys at an ultrasonic frequency (20 kHz), and a range of temperatures likely to be encountered by such materials in aerospace and power generation applications and in basic research, is described. The machine is assembled entirely from commercially available components used in ultrasonic joining processes. Basically, it consists of a power supply module and heavy duty transducer capable of delivering up to 1.2 kW of acoustic energy at peak‐to‐peak amplitudes ranging from 10 to 20 μ, which is further amplified by tuned acoustic horns. The machine sets up a 20 kHz standing wave in the resonant test specimen. Peak‐to‐peak displacement amplitudes in the specimen of up to 300 μ (typical stress levels up to 1400 MN/m2) can be achieved. Provisions have also been made to accurately monitor the frequency of testing and the displacement amplitude during the test. As an example of the capabilities of the machine, results of high‐frequency fatigue tests performed o...

Ultrasonic inspection device and system

Abstract: An ultrasonic measuring system particularly suited for measuring the wall thickness of large tubing of widely different shapes and sizes An ultrasonic transducer is adjustably supported in an ultrasonic head assembly so as to provide precise focusing of the energy across a gap to the surface of the part being measured The head assembly is urged against the surface of the part while the two are displaced relative to one another so that the transducer scans a predetermined path along the part Freely rotatable balls carried by the head assembly engage the surface of the part while a column of water is maintained to fill the gap between the transducer and the surface of the part Provision is made for rotating circular parts so that the transducer sweeps out a spiral path over the surface of such parts In the case of non-circular parts, the head assembly is oscillated from side-to-side while the part and the head are moved relative to one another along the longitudinal axis of the part so that the transducer sweeps out a sinusoidal path over a side of the part

Ultrasonic ball bearing testing method - has series of radial and tangential nozzles providing pulsed fluid flow during electronic testing

Abstract: A ball bearing testing device especially for revealing internal defects, has the tested component immersed in a liquid in an ultrasonic testing device, irradiated and rotated, to obtain a complete test. Coupling liquid (1') necessary for the acoustic contact is used at the same time for forming a hydrostatic-dynamic sliding layer (8') between the tested component (6) and the ultrasonic coupling element (4), and also to rotate the component. The top fo the coupling element (4) has a depression (8) to hold the component. Jets (7) are introduced tangentially into this depression, and may be two in number, at different angles.

Ultrasonic inspection recess in heat exchanger and nuclear steam generator tubesheets

Abstract: A vessel with a butted weld seam is provided with an access slot in its surface at a selected distance from the weld seam. An ultrasonic probe engages with a wall of the slot which is aligned with the weld and signals generated by the probe cross the axis of the weld frontally without substantial reflection from adjacent vessel surfaces.

A momentary-contact system for ultrasonic testing of steel at temperatures up to 1 200°C

Abstract: The British Steel Corporation has developed an experimental ndt system for the ultrasonic inspection of steel blooms and billets at elevated temperatures to detect piping and segregation using a momentary-impact pressure coupling technique. The apparatus comprises a steel head assembly mounted for reciprocating movement. Two ultrasonic transducers, one for transmission and the other for reception, are mounted on a split head separated by an acoustic attenuator. The head is reciprocated in such a manner as to cause impact upon the sample with an impulsive blow of short dwell time (

Ultrasonic velocity measurement to inspect malleable iron casting

Abstract: The authors describe the possibilities for the application of measurement of longitudinal ultrasonic waves to ndt with special reference to the inspection of malleable iron castings. They discuss experimental details of such measurements and the problem of its application in industry. They give two examples of applications for castings designed as machine parts: detection of primary graphite; and hardness testing.