Showing papers on "Ultrasonic testing published in 1990"

Developments in ultrasonic modeling with finite element analysis

Abstract: An overview is given of finite element analysis and its application to the modeling of ultrasonic nondestructive evaluation phenomena. Following a discussion of the underlying weighted residual methodology, a mass-lumping technique is described which results in an efficient computer implementation for 2D geometries. Code predictions are compared with both analytical and experimental results, and data from studies of attenuation, anisotropy, defect interactions, and surface waves are given. Initial results from a full 3D formulation are also shown.

High frequency-high temperature ultrasonic transducers

Abstract: Ultrasonic testing is a promising NDE technique for ceramic structural components. The lifetime of such components is controlled by defects and flaws. The critical flaw sizes for high performance ceramics are 25 µm and to detect such small flaws, the frequency of the transducers has to be >30 MHz [1–4]. Such transducers are usually made from ZnO, LiNbO3, LMN composites [5], and PVDF piezoelectric materials However there are no reports of aluminium nitride (AIN) films being used for such applications In this paper the piezoelectric and dielectric properties of A1N films and their application to high frequency devices are discussed and compared with the conventional materials.

Quantitative theory for laser ultrasonic waves in a thin plate

Abstract: Numerical inversion of the Hankel–Laplace transform has been performed for the case of ultrasonic displacements in an infinite, homogeneous, isotropic plate which is excited thermoelastically by a laser pulse. Values for the elastic moduli and the plate thickness may be extracted when the calculated displacements are compared directly to those obtained experimentally. Previous authors have demonstrated methods for determining the elastic modulus in thick plates; this letter shows that using a different method for the development of the theory allows similar modulus determinations to be made for thin as well as thick plates.

A system model for the ultrasonic inspection of smooth planar cracks

Abstract: This paper describes a system model for the ultrasonic inspection of smooth planar cracks in ferritic steel, using pulse-echo probes. The model predicts the echo amplitudes and ranges as functions of the probe position. It is applied to problems of procedure design, assessment, and technical justification on power station plant. The model is implemented as a suite of versatile and user-friendly computer codes, suitable for use by practical NDT engineers, and is supported by a comprehensive user manual. The paper describes the principles of the model and gives examples of its application to power plant problems. Illustrations are also given of the extensive validation which the model has undergone through comparison with experiment.

Ultrasonic contact transducer for point-focussing surface waves

Abstract: An ultrasonic contact transducer for point-focussing surface waves having a narrow beam width and a high sound intensity at a focal point in order to obtain better resolution and high beam intensity, which is applicable to the nondestructive testing technique of the surface or subsurface of a specimen to be tested, is disclosed. The ultrasonic contract transducer generates surface waves, focuses the waves at one point on the surface of the specimen and receives again the signals scattered from the surface flaws or subsurface flaws of the specimen, in order to detect the surface cracks, surface flaws, subsurface flaws of the specimen and to detect the delamination in a thin laminated film. The ultrasonic contact transducer comprises a curved piezoelectric element for generating ultrasonic waves, a acoustic contact lens to enable, in use, the ultrasonic waves generated by the curved piezoelectric element to be focussed at a flat surface of the specimen to enable the detection, sizing and imaging of surface cracks and subsurface detects of the specimen and to detect delamination in the laminated film specimen. The acoustic contact lens further includes a scattering means integrally formed to the acoustic contact lens to scatter the ultrasonic waves reflected from the flat bottom surface of the acoustic contact lens.

Nondestructive characterization of texture and plastic strain ratio of metal sheets with electromagnetic acoustic transducers

Abstract: All the lowest‐order independent CODF (crystallite orientation distribution function) coefficients W400, W420, and W440 of rolled steel sheets, with thickness less than 1 mm, have been obtained nondestructively by using the known single‐crystal elastic constants and the relative ultrasonic velocities measured with EMATs (electromagnetic acoustic transducers). The ultrasonic velocities of all the waves, longitudinal waves, shear waves propagating in the through thickness direction, and SH0 (shear horizontal) plate waves, were measured by the EMATs. No acoustic coupling medium was necessary, making possible quick, accurate, and reproducible measurements. It is shown that the CODF coefficients can be obtained as the solutions of three linear equations in which the measured relative ultrasonic velocities are included. There was an overall correspondence between the ultrasonic pole figures drawn using the obtained CODF coefficients and x‐ray pole figures. All nine elastic constants of a steel sheet were also c...

Ultrasonic measurement methods

Abstract: Ultrasonic Measurement Methods describes methods used in ultrasonic measurements and covers topics ranging from radiated fields of ultrasonic transducers to the measurement of ultrasonic velocity and ultrasonic attenuation, along with the physical principles of measurements with electromagnetic-acoustic transducers (EMATs). Optical detection of ultrasound and measurement of the electrical characteristics of piezoelectric devices are also examined. Comprised of seven chapters, this volume begins with an analysis of the radiated fields of ultrasonic transducers, followed by a discussion on the measurement of ultrasonic velocity and attenuation. The next chapter describes the physical principles of measurement with EMATs and the advantages of such devices based on their couplant-free operation. Optical detection of ultrasound is then considered, together with the problem of measuring the electrical characteristics of piezoelectric resonators and standard methods for obtaining the equivalent electrical parameter values. The final chapter is devoted to ultrasonic pulse scattering in solids and highlights many fascinating examples of wave scattering, some of which are accompanied by theoretical analysis. This book will be of interest to physicists.

Ultrasonic air-in-line detector self-test technique

Abstract: An ultrasonic air-in-line detection system for use in detecting air bubbles in the fluid line of a disposable cassette mounted on a main pump unit is disclosed in which a self-test procedure is periodically used to ensure that any faults in the ultrasonic air-in-line detector which do not fail safe are automatically detected. After a pumping cycle is completed, if the ultrasonic air-in-line detector indicates that there is fluid in the fluid line at the location of the ultrasonic sensor, the operating frequency of the transmitting ultrasonic transducer is changed to a non-resonant frequency for the self-test procedure. If the ultrasonic air-in-line detector still produces a signal indicating that there is fluid in the line, this indicates that there is a failure in the ultrasonic detector and a fault is indicated and the system is shut down.

The propagation of short pulses of ultrasound from a circular source coupled to an isotropic solid

Abstract: New finite‐difference formulations in cylindrical coordinates are given allowing calculations to be made of the field radiated by a circular source coupled to an isotropic solid. Theoretically predicted results are compared with earlier theoretical and experimental results for the case of a pointlike source. Calculations of the spacial distribution of the field radiated by a finite‐sized circular source are compared with stroboscopic visualizations of the field radiated by a transducer typical of those used in nondestructive evaluation using ultrasound. Calculated field‐point particle‐velocity waveforms are compared with experimentally measured waveforms received using a miniature piezoelectric receiver directly coupled to the solid surface as well as with calculated results obtained using an impulse‐response model. Good agreement between theoretical and experimental results is observed. The field radiated into solids is described in terms of plane and edge waves. The results are of particular significance for explaining the limitations of nondestructive evaluation using ultrasonic pulse‐echo techniques.

Ultrasonic testing method

Abstract: An ultrasonic testing method for detection of flaws in a material to be tested having a curved surface portion by use of an ultrasonic probe, wherein a center axis of curvature of the curved surface portion of the material to be tested and the center axis of the probe are set in an eccentric relationship so that the angle of refraction of an ultrasonic wave is 90°, and the probe comprises a tip portion having a curved surface of the same kind as the curved surface portion of the material to be tested and a radius of curvature of from 1.0 to 3.0 times the radius of curvature of the curved surface portion of the material to be tested. The method enables detection of internal flaws in, particularly, a spherical or cylindrical body formed of a ceramic and used as a bearing member.

Ultrasonic inspection of seal integrity of bond lines in sealed containers

Abstract: A method for determining bond integrity of a sealed package has a lid bonded to a container rim by detecting flaws in the bond between the lid and the container. The method comprises: i) positioning the container rim between an ultrasonic transmitter system and an ultrasonic receiver system; ii) ultrasonically coupling the transmitter system and the receiver system to the container rim; iii) transmitting ultrasound waves from the transmitter system through the container rim to the receiver system; iv) generating a signal representative of the ultrasound waves received by the receiver system; and v) analyzing the signal for predetermined signal characteristics representative of a flaw in the bond to identify a flawed package seal.

Ultrasonic texture and stress measurements in anisotropic polycrystalline aggregates

Abstract: A perturbative treatment of ultrasonic Rayleigh wave propagation is applied to investigate the case of an initally deformed metal plate, assumed to be homogeneous and to consist of an orthotropic disribution of cubic crystallites. Time‐of‐flight measurement techniques are proposed for the determination of both stress and texture. An analysis of these experimental results and a comparison with results of both ultrasonic bulk waves and neutron diffraction techniques confirm the reliability of this method. The special case of residual stresses is discussed in detail. Measurements of residual stresses with this technique agree with the results of strain gage measurements.

Ultrasonic tire testing method and apparatus

Abstract: A method and apparatus for non-destructive ultrasonic testing of tires is disclosed wherein an ultrasonic transmitter is positioned outside of the tire and applies pulses of ultrasound to the tire at a plurality of locations around the tire's circumference for transmission through the tire wall and receipt by an ultrasonic receiver located within the tire. The ultrasonic receiver generates signals in response to the received ultrasonic transmissions and a computer processes these signals to generate characterizing data from which defects in the tire may be determined. Signals representative of the defects are then processed to generate a graphic display illustrating the location of the defects with the tire.

On effective spectrum‐based ultrasonic deconvolution techniques for hidden flaw characterization

Abstract: From the pioneering works of Gericke [O. R. Gericke, J. Acoust. Soc. Am. 35, 364–368 (1963)] and some other researchers [L. Adler, K. V. Cook, and W. A. Simpson, ‘‘Ultrasonic frequency analysis,’’ in Research Techniques in Nondestructive Testing, edited by R. S. Sharpe (Academic, London, 1977), Vol. 3; A. F. Brown, ‘‘Ultrasonic spectroscopy,’’ in Ultrasonic Testing, edited by J. Szilard (Wiley, New York, 1982)], frequency spectra of ultrasonic returns form hidden flaws carry a rich amount of information usable for flaw characterization. With a proper modeling of these ultrasonic echoes, the effectiveness of such frequency analyses can be further enhanced by a process called deconvolution or inverse filtering. In this paper, the performances of several deconvolution algorithms when applied to ultrasonic pulse echoes from artificial flaws embedded in some aluminum blocks are investigated. The relative computational complexities of these algorithms are also analyzed and compared. Empirical results shall just...

Ultrasonic inspection apparatus

Abstract: An ultrasonic inspection apparatus comprising a large number of array oscillators (101 ∩ 10n) in a columnar shape. The oscillators are excited sequentially to generate a sequence of ultrasonic beams to scan an object of inspection. The reflection from the object is analyzed to inspect the surface condition of the object and the existence of any fault inside it. Before an inspection, ultrasonic scanning of a reference material having a uniform quality and free from any defects is performed in order to collect the reference data for each ultrasonic beam (each channel). Correction values are prepared on the basis of these reference data and the reception signals obtained by the ultrasonic scanning of the object are corrected by use of these correction values. One correction means determines the ratio of the mean value of the reference value to the reference value of the channel for each channel, multiplies the reception signal of the same channel by the ratio as the correction value and uses the product as the data to be displayed on a display unit (21). Another correction means determines a damping ratio to the reference value of each channel so that the reference value of each channel becomes a minimum value or a predetermined value below the minimum value, and the reception signal of the same channel is damped by a sensitivity leveling circuit (31) using the damping ratio. Variance of sensitivity between the channels can be eliminated by these correction means.

Review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials

Abstract: A review and statistical analysis of the ultrasonic velocity method for estimating the porosity fraction in polycrystalline materials is presented. Initially, a semi-empirical model is developed showing the origin of the linear relationship between ultrasonic velocity and porosity fraction. Then, from a compilation of data produced by many researchers, scatter plots of velocity versus percent porosity data are shown for Al2O3, MgO, porcelain-based ceramics, PZT, SiC, Si3N4, steel, tungsten, UO2,(U0.30Pu0.70)C, and YBa2Cu3O(7-x). Linear regression analysis produced predicted slope, intercept, correlation coefficient, level of significance, and confidence interval statistics for the data. Velocity values predicted from regression analysis for fully-dense materials are in good agreement with those calculated from elastic properties.

Ultrasonic velocity change with creep damage in copper

Abstract: We studied the ultrasonic velocity change caused by the accumulative creep damage in polycrystalline pure copper after high-temperature tensile loading. The propagation velocities of bulk waves, longitudinal and shear waves polarized parallel and perpendicular to the stress direction, showed a strong sensitivity to intergranular creep controlled by grain-boundary cavitation and subsequent microcracking. The velocities decreased slowly with creep time up to approximately 60 pct of the lifetime, when the steady creep shifted to the tertiary creep. Beyond this point, they decreased at ever increasing rates until eventual failure. The total velocity changes amounted to several percent of the original velocities. The creep damage also caused velocity anisotropy in the shear waves. Evolution in the anisotropy revealed that formation of cavity arrays, cavity coalescence, and microcracking, which occurred preferentially on boundaries lying normal to the stress axis, were restricted to the last 20 pct of the lifetime. Metallography and measurements of porosity support the ultrasonic observations.

Ultrasonic Testing by Determination of Material Properties

Abstract: This Chapter deals with the measurement of material properties and of elastic constants, as far as they are of interest for materials testing in general and where they can be carried out by using commercial testing instruments. This excludes therefore many purely scientific problems and measuring methods or permits only their brief mention. For further and more detailed studies the textbook of Tietz [41] is strongly recommended.

Polymer film thickness measurement using laser‐ultrasound techniques

Abstract: The thickness of thin polyester film has been measured using ultrasonic Lamb waves which were generated and detected using noncontacting laser techniques. The uncertainty analysis of such a measurement technique has been examined. Systematic errors in both time of flight and distance between laser generation and detection points were estimated and reduced with the assistance of computerized X‐scan translation techniques. Thickness measurements with uncertainties of less than 3% have been achieved.

Ultrasonic transducer assembly and ultrasonic acoustic microscope

Abstract: Various ultrasonic transducer assemblies are disclosed in which each assembly includes a pair of ultrasonic transducers for emitting or receiving an ultrasonic wave, respectively, and wherein the ultrasonic transducers include a concave shaped ultrasonic transducer and a flat shaped ultrasonic transducer. The ultrasonic transducer assemblies realize excellent magnitude of accuracy, resolving power, versatility and simplicity in handling. In addition, various ultrasonic acoustic microscopes are disclosed incorporating the aforementioned ultrasonic transducer assemblies and realizing the same results thereof.

Semi-automatic system for ultrasonic measurement of texture

Abstract: A means and method for ultrasonic measurement of texture non-destructively and efficiently Texture characteristics are derived by transmitting ultrasound energy into the material, measuring the time it takes to be received by ultrasound receiving means, and calculating velocity of the ultrasound energy from the timed measurements Textured characteristics can then be derived from the velocity calculations One or more sets of ultrasound transmitters and receivers are utilized to derive velocity measurements in different angular orientations through the material and in different ultrasound modes An ultrasound transmitter is utilized to direct ultrasound energy to the material and one or more ultrasound receivers are utilized to receive the same The receivers are at a predetermined fixed distance from the transmitter A control means is utilized to control transmission of the ultrasound, and a processing means derives timing, calculation of velocity and derivation of texture characteristics

Crack detection in silicon nitride by acoustic microscopy

Abstract: The application of low-ductility materials depends upon the successful detection of small defects which might otherwise cause premature failure. In the case of advanced ceramics such as silicon nitride it is required to detect surface-breaking defects whose depth is a few tens of micrometres, which is beyond the resolution limit of most conventional ultrasonic testing. Although scanning acoustic microscopy has been shown to have sufficient resolution to detect such defects, most demonstrations have been limited to specially prepated laboratory test specimens. This paper reports the application of acoustic microscopy to the detection of critical defects in a test-block and in a finished ball-bearing component, both of which were manufactured from the same silicon nitride material. The data demonstrate the importance of choosing a sufficiently high frequency in order to detect shallow surface-opening cracks. Thus defects that could not be detected or resolved at 250 MHz were resolvable at 400 MHz.

Novel High-Frequency Air Transducers

Abstract: Ultrasonic transducers operating in air in the frequency range of 1–10MHz have major applications in robotics and nondestructive evaluation. For robotics applications, high-frequency air transducers make possible range measurements with a resolution in the 30–100 μm range. For nondestructive evaluation, it is possible to make transmission C-scan systems operating in air for the inspection of composites, green ceramics, and even metals at elevated temperatures. In this work, we report on the use of ligneous materials as a matching layer for PZT-based transducers.

Device for testing of oblong objects by means of ultrasonic waves

Abstract: The object of the invention is a device for ultrasonic inspection of cylindrical objects. A transmitting ultrasonic transducer generates ultrasonic waves that are acoustically irradiated into the respective object via a coupling medium. At least three ultrasonic transducers are arranged in a row next to one another along a line. The outer ultrasonic transducers are receiving ultrasonic transducers. The other ultrasonic transducers are transmitting or transmitting/receiving ultrasonic transducers. The line is inclined against the longitudinal axis of the object by an angle which is between 0°and 45°.

Single mode ultrasonic inspection method and apparatus

Abstract: An ultrasonic inspection apparatus is adapted for utilizing both pitch/catch and pulse/echo information obtained utilizing a single mode of wave propagation. The apparatus includes an ultrasonic signal transmitting assembly, a signal receiving assembly, a positioning mechanism, and an arrangement for recording the information received by the signal receiving assembly. The transmitting assembly includes at least one source transducer for transmitting shear mode ultrasonic search signals into the mass of an object to be inspected. The signal receiving assembly receives shear mode ultrasonic catch signals that are produced as the ultrasonic search signals encounter discontinuities in the mass of the object to be inspected and are directed toward and detected by at least one catch transducer. The signal receiving assembly also receives shear mode ultrasonic echo signals that are directed back to a first source transducer. The position determining mechanism is adapted for controlling the position of each source transducer and each catch transducer and for keeping track of the exact position of each transducer as the transducers send and/or receive ultrasonic signals so that signals from common discontinuities may be grouped together or correlated. The recording device records the ultrasonic signals received by the signal receiving assembly in a form that enables the signals to be analyzed to help characterize the acoustic discontinuities in the mass of the object being inspected.

Ultrasonic Inspection of Steam Generator Tubing by Cylindrical Guided Waves

Abstract: In this paper we report on the experimental results demonstrating the potential of using cylindrical guided waves (CGW) for inspection of steam generator tubing (SGT). The CGW ultrasonic technique is intended to complement the present eddy current (EC) practice for in-service inspection as well as to provide an alternative tool for pre-service inspection. Below, we review the current NDE practice for SGT and the motivation of this study.