Showing papers on "Ultrasonic testing published in 1989"

The role of piezocomposites in ultrasonic transducers

Abstract: Combining a piezoelectric ceramic and a passive polymer to form a piezocomposite allows the transducer engineer to design new piezoelectrics that offer substantial advantages over the conventional piezoelectric ceramics and polymers. The rod composite geometry provides materials with enhanced electromechanical coupling and with acoustic impedance close to that of tissue; these factors yield transducers for medical ultrasonic imaging with high sensitivity and compact impulse response. The dice-and-fill technique produces piezocomposites that can be readily formed into complex shapes to facilitate focusing the ultrasonic beam. Proper design of the rod spacing yields materials that exhibit low crosstalk between array elements formed by patterning the electrode alone, without cutting between the elements. In this way, curved annular arrays have been made that provide high-quality clinical images of substantial diagnostic value to physicians. Included is an extensive bibliography of papers documenting the role of piezocomposites in ultrasonic imaging transducers. >

Analytic comparison of the sensitivities of bulk‐wave, surface‐wave, and flexural plate‐wave ultrasonic gravimetric sensors

Abstract: We show that, for small added masses, the sensitivities of bulk‐mode, surface‐mode, and flexural plate‐mode gravimetric ultrasonic sensors are respectively 2/ρλ, ≊1/ρλ, and 1/2ρd, where ρ is the density of the sensor substrate material, λ is the wavelength, and d is the plate thickness of the flexural‐mode sensor.

Ultrasonic non-destructive evaluation of thin specimens

Abstract: In the field of non-destructive evaluation of materials, conventional ultrasonic measurement techniques are limited to materials having a thickness which is relatively large compared to the wavelength of the ultrasonic signal used. The present technique enables the accurate ultrasonic non-destructive measurement of materials which are relatively small compared to the wavelength of the ultrasonic signal used. Ultrasonic signals received from a thin material are processed in the frequency-domain either directly or by use of a Fast Fourier Transform. Specifically, the frequency response of the ultrasonic transducers used in the measurement is removed from the frequency response of the signal received when measuring the material. This yields a frequency response which is indicative of the material alone. Then, the measured frequency response of the material is evaluated to determine unknown parameters of the material. For instance, the phase of the measured signal is determined over a predetermined frequency range (usually the bandwidth of the transducers), and the phase is used to determine the speed of ultrasonic waves travelling in the material for frequencies within the predetermined range. Likewise, the magnitude of the measured signal is determined over the predetermined frequency range, and the magnitude is used to determine the attenuation of ultrasonic waves travelling in the material for frequencies within the predetermined range.

A laser study of transient Lamb waves in thin materials

Abstract: A method is described by which transient ultrasonic Lamb waves may be generated and detected within thin materials, using laser techniques. The material is thin enough that only the two lowest‐order modes of Lamb waves need be considered. These are the a0 mode, which is dispersive in the thin plate limit, and the s0 mode, which is not. Signal processing techniques were used to determine the dispersion characteristics of the a0 mode, and the velocity of the s0 mode, in both aluminum and metallic glass samples. From these measurements, it was possible to estimate both the thickness of the samples and their elastic constants. The errors involved in such a measurement are discussed.

Nondestructive evaluation of adhesive joints by guided waves

Abstract: Guided waves in an adhesive layer between two adherend half‐spaces are shown to be uniquely sensitive to most types of bond defects. A simple experimental technique based on ultrasonic transmission mesurement is introduced to detect leaky guided modes in the interface layer. Experimental results for these dispersive guided modes are shown to be in good quantitative agreement with theoretical predictions. The suggested technique might find numerous applications in nondestructive evaluation of different bonds of layered structure such as adhesive and brazed joints.

A paraxial theory for the propagation of ultrasonic beams in anisotropic solids

Abstract: The necessity of nondestructively inspecting cast steels, weldments, composites, and other inherently anisotropic materials has stimulated considerable interest in wave propagation in anisotropic media. Here, the problem of an ultrasonic beam traveling in an anisotropic medium is formulated in terms of an angular spectrum of plane waves. Through the use of small angle approximations, the integral representation is reduced to a summation of Gauss–Hermite eigensolutions. The anisotropic effects of beam skew and excess beam divergence enter into the solution through parameters that are simply interpreted in terms of the slowness surface. Both time harmonic and pulsed solutions are discussed. Formulas are also presented for transmission of a beam through a curved interface between two media. Examples are given illustrating how this method may be applied to predicting beam patterns during ultrasonic inspections.

Ultrasonic inspection apparatus with centering means for tubular members

Abstract: Pipe inspection apparatus comprising transducers for transmitting pulsed beams of ultrasonic energy longitudinally, transversely and obliquely into the wall of the pipe for detection of flaws. The apparatus includes a motor driven chuck 18 for rotating the transducers about the a pipe P and motor driven roller 12 for axial movement of the pipe whereby the transducers move in a helical scanning path. A control system 60 maintains the axes of the pipe and circle array of transducers in coincidence and with hydraulic controls 80 maintains each transducer at fixed distance to the pipe for sonically coupling thereto by a flowing liquid whereby a shear wave is generated by each beam in the tubular wall. The transducers comprise multiple pairs, the members of which are diametrically opposed and transmit in opposite directions, for transmitting longitudinally at angles of 12°, 27° and 42° to the pipe axis both clockwise and counterclockwise with one transducer of each pair disposed to transmit forward and the other reverse. For longitudinal flaws, one transducer of a pair transmits transverse clockwise and the other transverse counterclockwise. All transducers which transmit in a given direction are arrayed in the axial direction of the pipe. Pulsers 103, 161 simultaneously and repetitively energize and de-energize all forward transmitting transducers and after each such transmission pulsers 105, 162 simultaneously and repetitively energize and de-energize all reverse transducers. Reflection signals of predetermined strength are recorded and activate an alarm. A compressional wave transducer for determining wall thickness is included.

Ultrasonic liquid level monitoring system

Abstract: A liquid level measuring system having a tubular ultrasonic probe with a length in excess of the depth of liquid to be measured; for vertical insertion into a tank. A transducer inside the tube, at a first distance above the bottom end of probe body, responds transmits a sinusoidal acoustical pulse through the probe to the surface of the liquid. An echo returns from the surface of the liquid to the transducer and provides a sinusoidal echo signal. A receiver responds to the echo signal by providing a start signal corresponding to the transmitter signal crossing a predetermined amplitude in a predetermined direction and by providing a stop signal corresponding to a first selected echo signal crossing a second predetermined reference level in a predetermined direction. The speed of sound in the liquid is measured by measuring the echo time to a calibration rod in the tube at a known distance from the transducer. A timer measures the time between the start and stop signals and provides the time to a sequential controller. The depth of the liquid and the leak rate of the tank are calculated for display.

Determination of fruit and vegetable properties by ultrasonic excitation

Abstract: Problems involved in non-desctructive quality determination of fresh food products through sonic and ultrasonic excitation were discussed. An experimental setup for basic measurements of acoustic properties of fruits and vegetables was described. Preliminary tests were made with tissue specimens of some fruit and vegetables; the velocity of wave propagation, the attenuation rate, and the reflection properties of these products were calculated. The results demonstrate the feasibility of low frequency ultrasonic testing of agricultural products.

High-rangeability ultrasonic gas flowmeter for monitoring flare gas

Abstract: A transit-time ultrasonic gas flowmeter for high-rangeability requirements, such as those encountered in flare-gas flow-metering, is presented. The concept of ray rescue angle for the orientation of the ultrasonic transducers in single-beam transit-time ultrasonic flowmeters is introduced to overcome the problem of ultrasonic beam drift in high-velocity flows. To overcome problems associated with noise at high velocities, a chirp signal is used. To preserve the accuracy of the meter at low velocities near zero flow, a combination of chirp and continuous-wave signals is used to interrogate the flow. Overall system performance is presented, based on results from extensive wind-tunnel tests. >

Pulsed ultrasonic doppler borehole fluid measuring apparatus

Abstract: A measuring device for use in a producing well is set forth It includes a sonde having upper and lower centralizers to define an annular flow space therearound In the preferred embodiment, a motor driven sensor preferably a piezoelectric combination transmitter and receiver is, included to transmit and then receive ultrasonic pulses They are transmitted downwardly from the housing into fluid flowing in the well Reflective interfaces are defined by material differences Gas bubbles droplets and particles in the fluid flow and phases between oil and water, etc form reflective interfaces to create a scattering effect to transmitted ultrasonic pulses so that a return pulse is formed The pulses encodes fluid flow velocity as a result of the Doppler shift

Robotic acoustic seam tracking: system development and application

Abstract: The description of an ultrasonic-based seam-tracking robotic system that guides a nonwelding torch along different welding grooves is presented. A 100 kHz airborne transducer is used to inspect the workpiece ahead of a welding torch and measures the joint orientation and lateral deviation caused by curvature or discontinuities in the joint part. Data pertaining to the joint orientation and lateral deviation (echo pulse amplitude and time of flight) are obtained periodically by sampling equi-spaced points along the joint as the torch advances. A trajectory-generating algorithm uses this data to calculate the x, y, theta coordinates of the torch-tip trajectory needed to meet the tracking requirements. The experimental results from a feasibility study conducted to determine if this system could be used for tracking during live welding are also presented. >

Ultrasonic testing of metal-matrix composite materials

Abstract: The mechanical properties of a metal matrix composite material e.g. a bar 12 depend upon both the proportion of filler and the proportion of voids or pores. The filler proportion and the porosity can be assessed non-destructively by causing ultrasonic waves to propagate through a specimen, and measuring both the wave velocity and attenuation in the specimen. These measured values are compared (for example graphically) with those obtained with material of known filler volume fraction and porosity, and hence the unknown values determined. The apparatus 10 includes a tank 14 containing water 16 (as a coupling fluid). The tank has leaky seals 18. Two transducers 20, 22 are provided and a computer 24 is used to provide the results.

Quench detection of superconducting magnets using ultrasonic wave

Abstract: An ultrasonic quench-detection method for superconducting magnets is presented. This nondestructive method monitors the change of the acoustic transfer function of a superconducting magnet induced by a local temperature rise or an epoxy crack. Experiments were carried out on a small epoxy-impregnated magnet. The experimental results show that a local temperature rise of about 2-3 K can be detected by this method. It is concluded that the technique can provide early quench warning by monitoring continuously the change of the acoustic transfer function of the magnet. >

Nondestructive Evaluation of Adhesive Bond Quality: State of the Art Review

Abstract: : This state-of-the-art report describes the bonding process, the destructive methods used to measure bond strength, and the various NDE methods that have been evaluated for determining the quality of a bond. These NDE methods include sonics, ultrasonics, acoustic emission, nuclear magnetic resonance, x-ray and neutron radiography, optical holography, and thermography. Each of these methods has shown some limited success in detecting debond conditions. At the present time, however, it appears that only the sonic, ultrasonic, and nuclear magnetic resonance methods have the potential capability to differentiate qualitatively the gradations between a good bond and a debond and thus provide a correlation to bond strength. Nondestructive testing; Adhesive bonds; Adhesive bond testing; Adhesive bond strength; Sonic testing; Ultrasonic testing.

Ultrasonic study on structural instability of Bi2Sr2Ca1Cu2O8 single crystal

Abstract: The velocity and attenuation vs temperature of ultrasonic longitudinal wave propagated along two directions in the c-plane at 10° to the a and b axes were measured for a Bi2Sr2CA1Cu2O8 single crystal. The anisotropic elasticity in the c-plane is manifested. One direction shows obvious softening minimum around 250 K, the other reveals only monotonic stiffening down to Tc. The origin of the overall trend of elastic stiffening and some discrepancies appearing in the measurements so far for high Tc materials are analyzed or clarified. Attenuation peaks at 95K, 150K, and 250K are attributed to phase-like transition of first order.

Ultrasonic flaw detection apparatus

Abstract: PURPOSE: To judge and evaluate the shape, dimension and position of a flaw with high accuracy on the basis of the peak value and position of the max. echo of a receiving signal group and the position data of a probe by detecting a flaw by deflecting ultrasonic beam fanwise and dividing receiving signals into groups at every reflecting source. CONSTITUTION: Ultrasonic beam 4 is allowed to be incident on an object 2 to be inspected by the array probe 3a and phased array flaw detector 14 on the surface of the object 2 to be inspected and propagation times t 1 , t 2 in which a flaw part echo F and a bottom surface part echo B become the max. values P 1 , P 2 are calculated on the basis of the developing time t 0 of a transmission pulse S by a peak detector 9. The surface direction position X and thickness direction position Y of the sample 2 are set and the coordinates of the flaw part of a peak echo reflecting source are calculated and stored in a memory apparatus 11 along with the position data of the probe 3a obtained by means of a position detector 10. A control apparatus 15 divides receiving signals at the time of sector scanning into groups at an echo peak position to perform B-scope display and an image 1, a flaw part image 17 and a bottom surface image coinciding with flaws 1a, 1b and the shapes of the upper surface and bottom surface 2a of the sample are provided. Since images are sharp, highly accurate judgement can be performed. COPYRIGHT: (C)1991,JPO&Japio

Welding state monitoring device

Abstract: PURPOSE: To contribute to automation and unmanned operation of welding and improvement of quality by immersing a flange of a holding part of an object while being welded in a liquid and detecting an ultrasonic signal transmitted through the liquid CONSTITUTION: The ultrasonic signal produced by the object while being welded is detected to monitor a welding state by using an ultrasonic sensor 5 The flange 3 is then provided on the holding part 2 to hold the object 1 while being welding The flange 3 is immersed in the liquid 4 having little attenuation for ultrasonic waves The ultrasonic signal transmitted through the liquid 4 is then detected by the ultrasonic sensor 5 By this method, the device having high capacity can be used and further, monitoring capacity can be increased even for noises generated from a main spindle, etc COPYRIGHT: (C)1991,JPO&Japio

Ultrasonic wire bonder

Abstract: An ultrasonic wire bonder includes first and second ultrasonic wave applying devices, the direction of vibration of the first ultrasonic wave being orthogonal to that of the second ultrasonic wave. One of the first and second ultrasonic waves or a composite ultrasonic wave thereof is applied to a capillary and/or a support base for wire bonding, depending upon the bonding direction along which a wire is extended, or the inner lead longitudinal direction. A unit for detecting the positions of a semiconductor chip and lead frame may be provided to adjust a position and control the ultrasonic wave to be applied.

Nondestructive monitoring of materials properties

Abstract: This book contains the proceedings of a symposium on nondestructive monitoring of materials properties. The papers include: NDT techniques for monitoring material degradation and A study of high temperature damage processes using microradiography.

Ultrasonic nondestructive evaluation of solid-solid bonds

Abstract: The solid-state bonding of metals, e.g. diffusion bonding, friction welding, and inertial welding, is finding increasing use in the fabrication of structural components. A summary is presented of recent progress toward the development of nondestructive techniques to monitor the quality of such bonds. Emphasis is placed on the characterization of a particular microstructural origin of bond weakness, a distributed array of microcracks in the bond plane. Included is a discussion of theories for the interaction of ultrasound with such distributed defects, results of model experiments designed to validate the theories, and applications of techniques based on the resulting understanding to fracture studies of bonded surfaces and to inspection of aircraft engine turbine rotors. >

Statistical Pattern Recognition Techniques: A Sample Problem of Ultrasonic Determination of Interfacial Weakness in Adhesive Joints

Abstract: A pattern recognition approach was applied to the analysis of ultrasonic echo signals from two classes of aluminum-to-aluminum adhesive bonds. The two classes differed in the surface preparation of the adherends prior to bonding, resulting in different interfacial properties of the joints. These properties have a crucial effect on the long-term adhesive properties of the specimens. Application of advanced signal processing and pattern recognition techniques enabled the classification of the joints according to the surface preparation of the adherends, based on features extracted from the ultrasonic signals. The statistics yielded an upper bound for the probability of mis-classification of the specimens. The sensitivity of certain features, extracted from the ultrasonic signal, to the interfacial characteristics of the specimens is explained by means of the natural frequencies of a joint's components and surface condition of the adherends. This leads to a method for selecting the optimal probe frequency for carrying out the ultrasonic inspection.

Dispersion relations of plate modes in anisotropic polycrystalline sheets

Abstract: The presence of texture can explain the anisotropy of ultrasonic propagation velocities in polycrystalline materials. This paper derives dispersion relations with which the phase velocities can be calculated for plate modes guided along an arbitrary direction in the plane of an orthorhombic sheet. The effect of texture is brought into the analysis through the crystallites’ orientation distribution coefficients (ODCs). The dispersion relations are split into two parts, one for the P–SV motion and the other for the SH motion. The result for the symmetric P–SV motion approaches the angular variation in the velocity of the lowest (S0) mode with decreasing frequency. The anisotropy in Rayleigh surface wave velocity is also derived as a solution in the high‐frequency limit. These limiting solutions are useful for the nondestructive characterization of texture from ultrasonic velocity measurements.

Probe for ultrasonic flaw detectors

Abstract: A probe for ultrasonic flaw detectors includes a transducer and either a protection plate to protect the transducer or a metallic part for attaching the transducer directly to the object to be tested for flaws, these two parts being bonded to each other with a heat-resisting brazing or soldering material. Because of its high bonding strength, the probe thus formed is not only capable of serving both in high and low temperature ranges, but also may be used in a roving mode or in a stationary mode in testing the object.

Nondestructive evaluation of material properties with EMAT (formability in cold rolled steel sheets and residual stress in railroad wheel)

Abstract: Ultrasonic techniques using an EMAT (electromagnetic acoustic transducer) for evaluating material properties were developed. Two items are described. One is the evaluation of the formability in cold-rolled steel sheets by using the S/sub 0/-mode plate-wave EMAT. The other is the measurement by the stress in the rim of railroad wheels by using two polarized SH-waves EMATs. The experimental results obtained in these techniques agree with theoretical predictions, and the techniques are useful for monitoring the material properties. >

Positioning assembly for a transducer in a boresonic inspection system

Abstract: An immersion base ultrasonic inspection system for interrogating the bore and near bore material of turbine and generator rotors by passing ultrasonic search units through the rotor bore. This system utilizes variable focus array inspection transducers in a shear mode inspection of the near bore material. The system includes a positioning assembly for a transducer which includes carriage means for supporting the transducer and a first positioning means for tilting one end of the carriage means in a radial axial plane whereby the transducer may be positioned at an angle to a longitudinal axis of the system. A second positioning means is provided for circumferentially rotating the transducer to a known and repeatable angular position. Position resolver means are coupled to the first and second positioning means.

Ultrasonic testing of concrete

Abstract: A research project concerning the use of ultrasonic technology for detection of deterioration in concrete is reported. The development possibilities for the technology in detecting damage on the basis of excitation of broadband sound pulses and with evaluation based on digital signal analysis are discussed. Results are presented from a series of tests on concrete cylinders with fatigue-induced cracks. For the covering abstract of the conference see IRRD 858334. The French title of this paper is:- Controle du beton par ultrasons. The German title of this paper is:- Ultraschallpruefung von Beton.