Showing papers on "Ultrasonic testing published in 1979"

Method and apparatus for non-destructive inspection of tires

Abstract: A pulsed through-transmission ultrasonic non-destructive inspection of the internal structure in a tire wall is effected. The ultrasonic inspection is preferably carried out through the walls of a rotating inflated tire with the ultrasonic transducers being automatically moved toward the inner and outer tire wall surfaces to optimum relative distances of separation during an inspection cycle. The transducers disposed inside the inflated tire are preferably mounted for automatic retraction into a protected space during tire mounting and demounting operations. Such ultrasonic inspection techniques may be combined with conventional tire buffing methods and apparatus as practiced in tire retreading operations.

Programmed controller for ultrasonic testing

Abstract: A system for ultrasonically testing the material of a turbine rotor includes a drive unit for axially indexing and angularly orienting a plurality of crystal transducers through the bore of the turbine rotor under test; an ultrasonic tester for electronically activating the crystal transducers as they are indexed through the rotor bore to transmit ultrasonic signals which are propagated through the rotor material and for receiving the back reflected echo signals corresponding to the ultrasonic transmissions; and a programmed electronic controller electrically interfaced to the drive unit and ultrasonic tester for adaptively coordinating the operation thereof in a selected one of a plurality of control modes to observe generated anomaly indications and measured test data parameters from the drive unit and ultrasonic tester which are used to determine the size and location of a detected potential imperfection in the rotor material and to adaptively control the drive unit in accordance with a function based on the anomaly indications and observed measured parameters of the drive unit and ultrasonic tester. Accordingly, prespecified portions of the observed measured parameters are automatically recorded, at times, during the ultrasonic testing operations to provide information relating to the size and location of the potential imperfections.

Angular Response of Piezoelectric Elements in Phased Array Ultrasound Scanners

Abstract: Abstruct-In the design of phased linear array sector scanners for medical applications, it is important to preserve uniform response at each angle throughout the sector scan of k45". Examination of Linear array transducers showed reduced transmit pressure and receive sensitivity a t angles beyond * 20" by individual array elements. The angular response of piezoelectric elements, many wavelengths long and approximately one wavelength or less in width, do not agree with the predictions of simple diffraction theory for plane apertures. Continuous wave (CW) angular response measurements using the RCA Ultrasonovision of individual piezoelectric elements 0.6 h t o 2 h wide indicated this behavior was independent of inter-element coupling and pulse excitation effects within a linear array transducer. Spectral analysis of isolated elements showed a significant amount of energy coupled into the transverse mode due to the small aspect ratio of width to thickness dimensions of the piezoelectric elements. A fist-order hvo-dimensional numerical model, based on thickness mode and transverse mode vibrations, resulted in angular response functions which agree well with experimental measurements.

Tone-Burst Testing of Pulse-Echo Transducers

Abstract: Ultrasonic transducers for nondestructive inspection and for medical diagnosis are built as self-contained units to be held by hand or in fixtures. They radiate into solids or into liquid baths, and receive signals propagated through these media. The transducers are encased and have protective layers over their radiating piezoelectric elements. To achieve depth resolution, damping backings are bonded to the piezoelectric elements to generate broad bandwidths and hence short impulse responses. These transducers have been analyzed theoretically by Sittig as electromechanical transmission lines. In this paper, Sittig’s program is used t o calculate the time and frequency response of several transducer configurations with families of values for their electromechanical parameters. Experimental methods are summarized and presented for the evaluation of transducers. It appears that there is sufficient difference between everyday practice and the present state of the art (both Manuscript received June 13, 1978. The author is with the Manufacturing Processes Laboratory, Ford Motor Company, Detroit, MI 48239. theoretical and experimental) to yield opportunities for significant improvements in transducer fabrication and testing.

Ultrasonic test method and apparatus with coupling liquid temperature compensation

Abstract: In an ultrasonic pulse-echo test measuring or gaging system wherein a workpiece is coupled to the ultrasonic transducer by a liquid coupling medium, the temperature of the liquid affects precise measurement of the workpiece as the acoustic velocity of a liquid changes with temperature To compensate for the change of acoustic velocity during measurement periodically a search pulse is transmitted along its normal path over a calibrated fixed distance The resulting transit time value is converted to a distance value and compared witht the calibrated distance value Any difference in the values updates a compensation factor which subsequently is used in the test system Periodic updating may be set to occur, for example, every one-half second

Improved ultrasonic nondestructive testing of pressure vessels

Abstract: Progress in the development of synthetic aperture imaging techniques and a flaw detection technique for ultrasonic pulse-echo flaw evaluation is described. Synthetic aperture test results using narrow-beam probes show increased signal-to-noise ratios. Processing times for synthetic apertures constructed with wide-beam probes have been reduced. Results of deconvolution combined with synthetic aperture processing show enhanced resolution. Also included are images from scans over curved surfaces, initial results of a parameter study, a method for flaw detection based on time series models, and progress in the development of graphical displays.

Ultrasonic Transducer Characterization at the NBS

Abstract: The design of high-frequency high-efficiency underwater acoustic transducers with good impulse response is discussed. Cross correlation of the impulse response of a particular design with that of an ideal transducer provides a parameter whose maximization is sought. Results indicate agreat flexibility in the choice of material combinations for quarter wavelength matching layers. T HE BROADENING of the frequency response of piezoelectric disk transducers radiating into a water load by use of single or multiple acoustic impedance matching layers is well known [ l ] . The best pulse response is obtained when a zero acoustic reflection coefficient exists over a wide frequency range at the disk-surface/load-medium interface together with the complete absorption of any acoustic energy incident on the backing medium, However, such an arrangement is both difficult t o realize and would be of low sensitivity. If the disk is air-backed, then, excepting losses, all the acoustic energy generated eventually enters the load-medium, giving a high sensitivity transducer. The use of transition layers between the disk face and the load-medium to improve the pulse response while retaining the high sensitivity of an air-backed disk is explored in detail. An equivalent circuit representation of the transducer, built around the Mason model [2] was employed to obtain a quantity x( t ) , defined as the inverse Fourier transform of the complex ratio F/V (see Fig. (I)) at discrete time intervals of (4f0)-’ S , fo being the piezoelectric disk thickness frequency. The quantity x ( t ) is termed the transducer impulse response. Limitations of the equivalent circuit in representing a piezoelectric disk are essentially those listed by Kossoff [ l ] . Manuscript received August 15, 1978;revised September 12, 1978. The author is with the Geophysics Group, School of Physics, Univer‘Throughout the paper, this term refers to the acoustic reflection at sity of Bath, England. the radiating surface of the piezoelectric disk. Fig. 1. Schematic diagram of transducer indicates where electrical input voltage V and output force F are measured. The performance of a particular transducer configuration is assessed by comparing its impulse response x 2 ( t ) with the impulse response of an air-backed piezoelectric disk radiating into an infinite medium of characteristic acoustic impedance equal to that of the disk material; the latter impulse response is here designated the ideal impulse response x1 (t). Quantitative comparisons of performance are available through R 1 2 , the maximum value of the normalized cross correlation function between x , ( t ) and x 2 ( t ) . It is well known that an acoustic match between the disk and the load-medium is obtained at the same number ( N ) of frequencies as there are quarter wavelength transition layers if the transition layer acoustic impedances Pi are all the geometric mean of those of their two contiguous materials. That is PN-i= dPN+I-iPN-,-i; i = O ; . . , N 1 (1) where i = 0 refers to the load (water) and i = N t 1 to the piezoelectric disk (PZT-SA): Po = 1.5 * lo6 and PN+ I = 33.7 . lo6 kg m-2s-1. The zero’s of the reflection coefficient’ can be made to coalesce at&, the frequency at which the layers are quarter wavelength, if the Pi are selected by what might be termed the binomial method: PN-~=PN+I-~(P~/P~+I)~~; i =O,N1;

Ultrasonic nondestructive testing apparatus

Abstract: An ultrasonic inspection apparatus for the inspection of underwater structures consisting of means for scanning a beam of ultrasound over the surface of the structure at a predetermined angle of incidence, means for receiving and displaying echo signals from the structure indicative of discontinuities within the structure, the action of the display means being initiated by control signals derived from echo signals returning from the surface of the structure, thereby rendering the displayed signals independent of the separation between the scanning means and the surface of the structure.

Method and means for ultrasonic inspection

Abstract: Ultrasonic inspection of a structure such as steel tubing is enhanced by moving the ultrasonic wave transmitter and receiver through the pipe and periodically injecting an ultrasonic pulse into the tube. Reflected waves are received during a sample period after each pulse injection. By proper selection of linear displacement between pulses and the sample time interval, the time reference of received signals can be adjusted whereby signals reflected from only one direction are coherently added.

Ultrasonic testing of weld seams of pipes for detecting transversely extending defects

Abstract: OF THE DISCLOSURE Ultrasonic test equipment for testing the welding seam a thick wall includes transducers arranged in tandem and along the welding seam, whereby a tandem pair inspects in any instance two surface-near zones (inner and outer surface) as well as an interior zone. One of the trans-ducers of the pair participates in a function test. Two pairs cover the same zones, but from opposite sides.

A High-Speed Ultrasonic Sing-Around System

Abstract: An ultrasonic sing-around system has been developed that allows the measurement of the velocity of sound in a sample to an accuracy of a few parts in 104 in a period of 10 ?s A facility is also provided to store a succession of measured sing-around periods This approach enables the continuous measurement of the velocity of sound in materials undergoing rapid changes of thermodynamic parameters such as temperature, magnetic field, or pressure to be achieved As an example, the magnetic-field variations of the velocity of sound in a magnetic gadolinium-yttrium alloy are reported

Apparatus and method for ultrasonic inspection of round stock such as tubing, pipe and rod

Abstract: Directed to non-destructive testing, particularly ultrasonic inspection of round stock such as tubing, pipe and rod wherein the inspection is conducted within a water tank to provide ultrasonic coupling of the ultrasonic probe or probes employed wherein the distance between the probe or probes and the surface of the round stock being inspected is maintained essentially constant during the course of the test to assure reliable inspection results and wherein the materials handling aspects of the testing are simplified.

Ultrasonic Temperature Profiling System for Detecting Critical Heat Flux in Non-Uniformly Heated Tube Bundles

Abstract: A new ultrasonic instrument system was developed and applied to the problem of detecting critical heat flux (CHF) in experiments that simulate a nuclear reactor fuel assembly. This instrumentation system used the principles of ultrasonic thermometry to detect and localte CHF in a tube bundle with non-uniform axial heat generation. The technique consists of measuring the time between pairs of ultrasonic echoes that reflect from a sequence of evenly spaced discontinuities along a sensor. Each measurement of time is directly related to the temperature of a specific segment of a sensor. The system was designed to handle many 16-zone sensors at a high rate of data acquisition so that CHF could be rapidly detected and accurately located. This paper includes a description of the sensor and the signal processing techniques as well as examples of the system's response to CHF.

Equivalent Electrical Networks for Transversely Vibrating Bars and Their Applications

Abstract: piezoelectric ceramic vibrators with high electromechanical coupling,” IEEE Trans. Ultrason. Eng., pp. 32-39, July 1963. . . 1974, pp. 2 4 X [ l41 R. S. Mezrich, K. F. Etzold, and D. H. R. Vilkomerson, “System for visualizing and measuring ultrasonic wavefronts,” Acoustical Holography vol. 6, N. Booth, Ed. New York: Plenum Press, 1975, pp. 165-191. [ 151 J. A. Kisslo, 0. T. von Ramm, and F. L. Thurstone, “Cardiac imaging using a phased array ultrasound system II: clinical techniques and application,” Circulation, 5 3 , 1976.

Process and apparatus for automatically adjusting ultrasonic test heads

Abstract: There is described a process for automatically adjusting the angle of inclination and the focus distance of ultrasonic heads in reference to the test piece in devices for the non-destructive testing of work pieces, especially tubes, using a computer where both the adjustment of the angle and the distance are adjusted and examined in each case by two angular transmitters operating mechanically independent from one another and absolutely coded for use by program of the computer. There is also described an apparatus for carrying out the process.

Detection of flaws in used railroad rail by ultrasonic inspection techniques

Abstract: The qualitative differences in the responses of new and used rail to ultrasonic inspection have been known for some time. The material presented in this paper quantifies the actual responses obtained from a collection of four rail samples which are typical of rail used on United States' railways. One of the samples was new, and three were used. Reflection and refraction data obtained through the rail head and probe interface indicate that the material properties in the head of used rail are anisotropic. As a result of this anisotropy, ultrasonic rail inspection systems, calibrated according to Sneil's Law in an isotropic rail, may not be fully effective in locating transverse defects (taches ovales) in rail heads.

Ultrasonic test head positioning for non-destructive testing - using water film supporting head on surface without contact

Abstract: The device for ultrasonic test heads for non-destructive material testing enables the heads to be guided to defined positions w.r.t. the surfaces of workpieces without using expensive control devices and without damage to or wear on the test heads or workpieces. This is achieved using a simple mechanical guide but avoiding direct mechanical contact with the workpiece. The contact is prevented by a film of fluid between the surface of the workpiece and the ultrasonic test head. A foot section (2) contains several nozzles (4) and tubes (4a) of small dia. supplied with fluid from a reservoir (6) in the top (1) of the device. The nozzles are arranged on a circle around the test head. The film is formed using water.

Method for transferring ultrasonic energy to or from an object and focused ultrasonic transducer

Abstract: A piezoelectric crystal (12) has a concave active surface and a high acoustical impedance. A flat layer (15) of molded material having a low acoustical impedance faces the active surface of the crystal to form a space therebetween. An intermediate layer (16) of molded material having an intermediate acoustical impedance fills the space between the crystal and the flat layer. Preferably, the intermediate material has a sonic velocity near that of water, and the flat layer has a uniform thickness of approximately 1/4 of the average wavelength of the ultrasonic energy emitted by the crystal, A housing (10) supports the crystal, the flat layer, and the intermediate layer.

Ultrasonic testing of weld between tube and plate - utilises movable probe mounted in tube using mandrel

Abstract: A movable ultrasonic probe connected to an echograph is used to check mechanical piece parts and partic. the welding between a tube and transverse plate. A thin wal tube (1) is fitted to thick transverse plate (2) and welded (3). An ultrasonic probe (10) is assembled to tube using mandrel (11) with toroidal sealing joints (12, 13) for liq. coupling medium. A pin (14) permits extension of mandrel by a spacer (15). This spacer houses a reflector block (17) to reflect ultrasonic waves from probe (24) through a hole (18) in spacer wall to the welded joint. A micrometer drives a shaft (31) to drive screw thread (20a) on spacer through nut (25) in support base (26) to move probe vertically.

Measurement of Very Small Vibration Amplitude in Ultrasonic Transducer by Means of a Laser Probe

Abstract: A highly precise and stable "laser probe" to measure a very small displacement and vibration amplitude was performed by using an optical interferometer with He-Ne laser. This laser probe is composed of two optical paths named " twin path " so close and symmetric with each other that the measurements are not disturbed by acoustic noise, low frequency ambient vibration, atmospheric fluctuation and room temperature change. The minimum detectable amplitude of the quartz plate by using this laser probe was found to be 3 X lo-' A with a final noise band width of 0.017 Hz. To show the feasibility of the laser probe, the distribution of the displacement and the vibration amplitude of an ultrasonic transducer were measured by applying dc and ac voltage respectively.

Size measurement and characterisation of weld defects by ultrasonic testing. part 1 - non-planar defects in ferritic steels

Abstract: Reports from the fabrication industry on the misinterpretation of defects with conventional manual ultrasonic testing have been widespread. Over-estimation of defects has resulted in unnecessary, expensive and time consuming repair and under-estimation may have led to significant defects being allowed into service. This paper reports on a program to define the problem by studying the interaction of ultrasound with weld defects using conventional equipment and assessment techniques, and to establish how the more recently developed and sophisticated techniques can be used to advantage. The present collaborative program of work is aimed to quantifying ultrasonic testing capability by providing detailed information on the application of both conventional and more specialized ultrasonic techniques to a large sample of defects and features in ferritic steel weldments in the 38 to 95mm thickness range.

Stimulating electro-acoustical transducers

Abstract: A transducer for launching ultrasonic test signals is stimulated by an electrical signal which is of trapezoidal contour. Particularly the trailing edge of the signal is to decline at a rate similar at least as to order of magnitude to the rise time, and occurring in synchronism with a natural zero crossing of the vibration of the transducer to fully develop at least one full ultrasonic oscillation.

PMMA fracture surface produced by ultrasonically modulated tensile stress

Abstract: Ultrasonic shear waves with a large amplitude and a frequency of 3.63 MHz were applied to a notched PMMA plate under uniaxial tension in order to produce artificial Wallner lines by altering the direction of the maximum principal stress during the rapid growth of fracture. The amplitude of the lines generated was found to be of the order of 10–102 nm and has been shown to change proportionally to the input‐wave amplitude. The interference colors observed indicate that the PMMA crack front is very liable to proceed inside the crazed layer ahead of the front; despite the intensive ultrasonic stress modulation very few cracks which reached or crossed the craze‐matrix boundaries were found.

Improvements in or relating to an ultrasonic nondestructive testing apparatus

Abstract: An ultrasonic inspection apparatus for the inspection of underwater structures consisting of means for scanning a beam of ultrasound over the surface of the structure at a predetermined angle of incidence, means for receiving and displaying echo signals from the structure indicative of discontinuities within the structure, the action of the display means being initiated by control signals derived from echo signals returning from the surface of the structure, thereby rendering the displayed signals independent of the separation between the scanning means and the surface of the structure.

Method and apparatus for ultrasonic tube inspection

Abstract: A method and apparatus for graphically displaying by means of an oscilloscope the measurements obtained with an ultrasonic inspection instrument (11) of the pulse-echo type. The instrument is designed to inspect tubular members (10) for primarily internal corrosion and to display the results on the face of a cathode ray tube (27). The oscilloscope produces a pictorial representation of the tube wall thickness.

Practical application of ultrasonic testing of austenitic weld joints

Abstract: The difficulties associated with ultrasonic testing of austenitic welds and parent materials are well known, but recent efforts in the research and development of new testing methods have brought advances. The practical application of the special testing techniques, however, still poses problems, as the requirements placed upon the testing personnel are very high. This report presents an outline for the development of a testing procedure, although it is necessary to proceed step by step, and each case has to be investigated anew. Some typical examination results obtained with special probes are mentioned. Furthermore, we deal with problem of occurrences of spurious indications.

Method of ultrasonic testing of the weld between a pipe and a plug to obturate this pipe, and plug adapted to this method

Abstract: A method of ultrasonic testing of a weld (c) between a pipe (2) and a plug (4) to obturate the pipe. This method is characterised in that it consists: on the one hand in forming in the outer wall of the plug (4) a circular depression having an annular surface (8") and a cylindrical surface (8') respectively intended to be in contact with one of the end edges of the pipe (2) and the portion of the inner wall of the said pipe adjacent to the said end edge of the pipe and, on the other hand, in forming in the said plug (4) a cavity (12) opening out at one of its ends and extending from this end beyond the said annular surface (8") and, after having made the weld between the said annular surface and the said end edge of the pipe (2), in the ultrasonic testing of the depth of the weld (C) in the vicinity of the said annular surface. Application to the ultrasonic testing of a weld (C) between a pipe (2) and a plug (4) to obturate the latter.