Showing papers on "Ultrasonic testing published in 1987"

Inhomogeneous wave generation and propagation in lossy anisotropic solids. Application to the characterization of viscoelastic composite materials

Abstract: This article develops a method for investigating some anisotropic media, such as composites, by the use of ultrasonic waves transmitted through a plate‐shaped sample immersed in water. The discussion begins with Christoffel’s equations for plane linear anelastic waves under the assumptions that for small angles of incidence the wave modes are plane and inhomogeneous and that the anisotropy is representable by hexagonal symmetry. The water–sample interface is treated using the law of Snell–Descartes for nonabsorbing media and takes into account mode conversion and the generation of acoustic surface waves. The method produces viscoelastic constants and relative attenuation coefficients as a function of the angle of refraction. The experimental measurement apparatus is described and data are given for the 25‐layer unidirectional Gr/epoxy composite. Results are presented in terms of slowness, damping vector, and attenuation curves. The results are significant in that they demonstrate the anisotropy both for t...

Ultrasonic probe having an ultrasonic propagation medium

Abstract: An ultrasonic probe having an ultrasonic propagation medium (8) is used in medical ultrasonic diagnostic systems for examination and inspection of inside of an examining body (9) by transmitting and receiving ultrasonic signals. The ultrasonic probe comprises a body (1), and the ultrasonic propagation medium (8) made of rubber cross-linked by cross linking agent. The ultrasonic propagation medium (8) is interposed between the examining body (9) and a portion for transmitting and receiving ultrasonic waves of the body (1) of the ultrasonic probe when the ultrasonic propagation medium (8) is used.

Texture of polycrystalline metals characterized by ultrasonic velocity measurements

Abstract: An ultrasonic method is presented for the nondestructive evaluation of the rolling texture in polycrystalline aggregate of cubic metals. Use is made of the elastic anisotropy measured by the propagation velocities of Rayleigh surface waves and surface skimming SH waves in the rolling plane. These velocity anisotropies permit the evaluation of the lowest three coefficients in the series expansion of the orientation distribution function and then enable the calculation of ‘‘ultrasonic pole figures’’ for the surface texture. The correspondence with the conventional x‐ray pole figures is comparatively good for the aluminum alloy tested, showing that the ultrasonic pole figures properly approximate the conventional x‐ray pole figures. The limitation and application are discussed.

Ultrasonic inspection probe for laminated structures

Abstract: An ultrasonic inspection probe for locating and sizing flaws in the radius region (20) and adjacent areas of a laminated structure (10), such as a composite "T" stiffener (30). The probe includes a plurality of shoes (48, 50, 52, 54, 56, 58) that are arranged for coordinated movement relative to the part under inspection. Each shoe includes a plurality of ultrasonic transducers that are arranged in predetermined adjacent relationships to one another and operated in timed sequence in one or more through-transmission, pulse echo or loss-of-back modes to effect an ultrasonic scan in one direction through the part while the transducers are moved together in another direction along the part. Inspection of the radius region is effected using combinations of angular pulse echo inspection (PEF, PEA, LL45P, RL45P), "radius-to-radius" through-transmission inspection at an angle through the radius region (RTT, RTR, L37.5T, L37.5R, U37.5T, U37.5R), and "flange-to-radius" through-transmission inspection normally into the upper flange (RU45T) and angularly out through the radius RU45R, LU45R).

Boresonic inspection system

Abstract: An immersion based ultrasonic inspection system is disclosed which is used to interrogate 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. A ranging transducer is provided which is used to correct the surface time of the inspection beam. A mapping transducer and blind bore sensor allow diameter mapping of the rotor bore as well as a blind rotor end sensing as the scan head carrying the transducers enters the bore. A scan head centering device or chuck deploys four radial arms to center and support the scan head. Each arm has a roller attached to the end which contacts the bore and rolls along so that the bore will not be damaged as the scan head passes through the bore. The chuck is driven by an electric motor and coupled to a resolver allowing the chuck to be adjusted according to bore geometry mapped by the mapping transducer. The chuck includes a pneumatic disengagement device for fail-safe disengagement of the centering arms to allow retrieval of the scan head in the event of motor or wiring failure. The chuck also includes cable pathways for control cables for the various scan head motion axes. An inspection transducer carriage is provided that provides three axes of motion to the inspection transducer. A radial motion is provided by two radial support assemblies driven by an electric motor and coupled to a resolver allowing radial position to be accurately determined.

Implementation of a Real-Time Ultrasonic Saft System for Inspection of Nuclear Reactor Components

Abstract: In recent years, the Pacific Northwest Laboratory has been developing the Synthetic Aperture Focusing Technique for Ultrasonic Testing (SAFT-UT) for the U.S. Nuclear Regulatory Commission (NRC). The program objective has been to develop and validate the SAFT-UT technology for inservice inspection of nuclear power plant components. This technique utilizes the full three-dimensional SAFT algorithm computed in the time domain. The project has included development of a field-usable, real-time SAFT-UT imaging system, and also enhancement of the SAFT-UT algorithm to achieve real-time rates. This paper discusses techniques that have been employed to achieve these goals, including a description of the system, system performance data, and a discussion of a real-time SAFT processor peripheral device for performing the computer-intensive SAFT algorithm computations. An overall view of the SAFT-UT system itself will also be discussed.

Ultrasonic NDE of cast stainless steel

Abstract: The microstructure of cast stainless steel can vary considerably, from elastically isotropic with an equiaxial, relatively small grain structure to elastically anistropic with a columnar grain structure to a combination of the two. The ultrasonic inspection of this material may be optimized if the grain structure is known. Shear waves will be more effective with the isotropic material whereas longitudinal waves will be better for the anisotropic material because of beam-focusing effects. In this paper, the results of experiments to characterize the microstructure by use of ultrasonic waves are discussed. It is shown that velocity of sound and beam skewing can be measured accurately enough to characterize cast stainless steel even in thick-walled reactor components. The consequences for field inspections are discussed, along with some results obtained from preservice field tests.

Point-Source/Point-Receiver Materials Testing

Abstract: Conventional measurements in the ultrasonic testing of materials, when used as the basis of a materials characterization procedure, typically rely on one or two piezoelectric transducers operating as source and receiver, attached to a specimen to launch and detect ultrasonic waves in the object to be characterized. Measurements of signal arrival time (or velocity) and amplitude (or attenuation), possibly as a function of frequency, are then correlated with the composition and the macro- and micro-structure of the material, which may include voids, flaws and inclusions distributed through a region of the material. While relative measurements of the time-of-flight and ultrasonic amplitudes do not! present extraordinary measurement challenges, absolute measurements do. It is unfortunate that absolute quantities are often required since they are difficult to obtain reliably with a conventional piezoelectric transducer-based ultrasonic system. For this reason, a considerable effort over the past decade has been undertaken to develop and improve non-contact methods for generating and detecting ultrasonic signals in materials. However, a limiting factor of all the existing non-contact measurement systems is the care required for their use and their reduced sensitivity in comparison to-those utilizing piezoelectric transducers.

Fiber optic sensing for ultrasonic NDE

Abstract: An innovative approach to nondestructive evaluation (NDE) using noncontacting optical sensors has demonstrated. In this effort a single mode optical fiber interferometer (OFI) was used to sense the presence and form of Rayleigh waves traveling along the surface of a steel test bar at a velocity of nearly 3mm/µs. Acousto-optic time-domain data was successfully used to detect the presence and locate the position of a test “flaw” (a machined slot) in the bar, and spectrum analysis was used to estimate its geometry and size. This approach has many potential applications in the ultrasonic evaluation of real flaws in structures with complex geometries. Coupled with the authors' earlier work demonstrating the feasibility of generating acoustic waves in metals using laser light pulses transmitted through the fiber optic probes, this latest achievement points to the development of a fully noncontacting, fiber optic based thermal-acousto-photonic (TAP) NDE system, with potential applications to the reliability testing of many important structures where composition, scale, geometry, or restricted access preclude the use of conventional NDE techniques.

Development and Comparison of Beam Models for Two-Media Ultrasonic Inspection

Abstract: This paper reports on an effort to model the radiation pattern of a submerged ultrasonic transducer exciting a beam which is incident on a liquid-solid interface. The important aspects of this process are the diffraction of the beam as it propagates in the liquid and solid media, focussing of the beam due to a lens at the transducer face and/or the curvature of the interface, and aberrations induced by refraction at the interface.

Air-Coupled Ultrasonic Transducer for NDE

Abstract: A high efficiency air-coupled transducer has been developed for applications in NDE. The transducer consists of multiple layers of readily available materials to match the impedance of a piezoelectric material to that of air. Transducers can be built to operate at frequencies as high as 450 KHz and can be incorporated into noncontact NDE systems. Laboratory and limited on-line evaluation of the air-coupled transducers have demonstrated applicebility of the technology to inspection, material property evaluation and intrinsically safe proximitv sensing and gauging.

Ultrasonic wave propagation in temperature gradients

Abstract: Ultrasonic methods are being developed for sensing and control of high temperature material processes such as welding and solidification. One of the problems in these methods is the distortion of the sound field caused by the change in material properties due to temperature gradients. This paper describes a ray-tracing method for calculating the effects of temperature on ultrasonic propagation in such systems. In the ray-tracing method, the material is conceptually divided into a number of plane layers. The refraction at each layer boundary is calculated from Snell's law using the sound speeds determined from the temperatures of the adjacent layers. The time required for an ultrasonic pulse to traverse each layer is also calculated, allowing the determination of the total time along a particular path. The method is applied to calculating the time of arrival of echoes from various interfaces around a molten weld pool.

Ultrasonic wheel probe with improved acoustic barrier

Abstract: This invention relates generally to an ultrasonic wheel probe for rolling along a workpiece to be tested for flaws, having a plurality of ultrasonic acoustic transducers and an acoustic barrier that rest in a coupling fluid. The instant invention comprises an improved means for detecting the distance between the transducer array and the surface of the workpiece.

Ultrasonic Robotic Sensor with Lateral Resolution

Abstract: Ultrasonic robotic sensors with high axial resolution, using the novel L2QZ transducers for broadband airborne ultrasound, have been extended so that they can also evaluate lateral details of a situation confronting them by using the motion of a robot's arm. This motion produces a synthetic aperture, as the situation is seen repetitively from various aspects by the ultrasonic system mounted on the robot's gripper. For the evaluation of these sequences we use simple time-offlight algorithms or ultrasonic holography imaging algorithms derived from wave theory. Our L2QZ-transducers yield good resolution in the axial and lateral directions. With the typical bandwith of 250 kHz and a center frequency of 200 kHz a resolution of about 1 mm is achieved in both the lateral and axial direction.

Test piece for inspection by ultrasonic method

Abstract: A test piece for use in ultrasonic testing of materials or of powdered metallurgically manufactured workpieces to witness minute flaws, in which reference flaws are incorporated in at least one surface of the test piece or in the joint zone between test piece sections.

Automatic ultrasonic testing method

Abstract: In an automatic ultrasonic testing method for automatically detecting internal flaws of an article (1) such as a solid-core station post insulator and a long-rod insulator, ultrasonic noise is liable to be generated in the ultrasonic testing waveform. To improve the detection of peaks caused by flaws, use is made of a standard waveform having a plurality of maximum peak hold data values predetermined intervals at all the detecting points. This waveform is obtained by detecting the waveforms of normal article including the ultrasonic noise, with which the ultrasonic testing waveforms of an article to be tested are compared. Therefore, it is possible to eliminate instability of the ultrasonic testing waveform and to detect a flaw echo having a level lower than that of the peak ultrasonic noise.

Ultrasonic pole figure for the texture of aluminum alloy

Abstract: An approximate method is proposed to calculate the pole figure diagrams based on the elastic anisotropy measured by ultrasonic velocity experiments. An example is taken from the surface texture of rolled plates of aluminum alloy 7075‐T651, for which the angular dependence of the Rayleigh wave is measured in the rolling plane and analyzed to obtain the expansion coefficients of orientation distribution function. The ultrasonic pole figures are favorably compared with the conventional x‐ray pole figures, both demonstrating a single texture centered over (001)[110] orientation.

A spherical capacitance transducer for ultrasonic displacement measurements in NDE

Abstract: A capacitance transducer is described which is particularly suitable for the measurement of ultrasonic surface acoustic transients. The transducer has a small spherical electrode in a simple construction which is straightforward to use in comparison with other designs. A typical transducer has been compared experimentally with a parallel-plate capacitance probe using laser-generated acoustic transients as a standard source. The transducer is shown to have a frequency response in excess of 5 MHz with a sensitivity of 1.5 mV nm-1 for Rayleigh surface transients a few nanometres in amplitude.

Ultrasonic wave phase matching apparatus

Abstract: In the ultrasonic wave phase matching diagnostic apparatus described in the specification, an array of ultrasonic transducers is arranged to transmit ultrasonic waves to an object to be investigated and to receive ultrasonic waves returned from the object. Focusing of the waves to a point in the object is accomplished by selective delaying of the transmitted signals from each of the ultrasonic transducers, and similar delays are imposed on received signals to define a focal point for signals received from the object. Scanning of the object is provided by stepwise changes in the ultrasonic transducers used for transmitting and receiving ultrasonic signals, and half-pitch scanning may be effected by using different numbers of ultrasonic transducers for transmission and reception of the ultrasonic waves.

Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Development of Nondestructive Testing Systems for In Situ Evaluation of Concrete Structures

Abstract: : An effort was made to develop an ultrasonic pulse-echo system for the investigation and evaluation of the interior of concrete structures. The large pulse-echo transducer fabricated at Ohio State University (OSU) was obtained for study. Experimental transducers were fabricated and bandwidths were altered and optimized. Transducer area and frequency of operation were determined and various piezoelectric materials were studied; acoustic and electrical matching were employed to optimize signal strength and signal-to-noise (S/N) ratio. The final prototype transducers were constructed of lead metaniobate (EC-82) lead zirconate titanate (PZT-5H). The transducer area and mass was reduced by 90 percent and the S/N ratio was increased by 200 percent when compared with the OSU transducer. The pitch-catch prototype configuration was used to successfully measure the thickness of a 9-1/4-in. concrete test slab with a S/N ratio of 18. The system is presently useful for making thickness measurements on concrete pavements and floor slabs. Limited tests have shown that a metal plate and a plastic pipe can be located in a concrete slab of 9-in. thickness or less. Also, a thickness measurement was made on concrete by generating wideband acoustic (sonic and ultrasonic) energy by an impact hammer and detecting the echoes with a low Q resonant receiver centered at 180 kHz.

Transducer Models for the Finite Element Simulation of Ultrasonic NDT Phenomena

Abstract: Numerical studies of realistic ultrasonic NDT situations in their most general form assume arbitrarily shaped defects excited by pulsed transducer waves all subject to the specimen’s external boundaries. The combination of three features, transmitter model, ultrasound/defect interaction, and receiver model makes a thorough quantitative evaluation extremely difficult, Although a numerical finite element code capable of handling ultrasonic wave propagation and scattering has been developed [1,2] the overall system remains incomplete without apropriate transducer models.

Combustion of multicomponent systems in an ultrasonic field

Abstract: A study was made of the dependence of combustion rate for the systems Ti-C-Ni and Ti-C-Ni-Mo, involving a readily-melting inert component, on ultrasonic field parameters. Curves were derived for the dependence of combustion rate on ultrasonic vibration amplitude. An increase in amplitude up to certain threshold values led to a reduction in combustion rate. Above these values there was an increase in combustion rate not in excess of the combustion rate in the absence of an ultrasonic field. A reduction in acoustic power also increased the rate of combustion. These results, along with the effects of the particle dispersivity, different concentrations of the metal fractions, and other parameters on the combustion-ultrasonic interactions, were analyzed.

Analysis of the RFC/NDE System Performance Evaluation Experiments

Abstract: The RFC/NDE System comprises automated eddy current and ultrasonic inspection stations developed by Systems Research Laboratories for Air Force depot level inspections of aircraft engines. The system performance is being evaluated through a series of experiments whose objectives are to quantify crack detection capability as a function of crack size in various engine components. This paper presents the eddy current results from the first (preliminary) phase of this evaluation.

High‐sensitivity ultrasonic interferometer for the detection of magnetic phase transitions

Abstract: An improved technique is described for the detection of magnetic phase transitions using acoustic waves with electrical interferometry. The method employs zinc oxide transducers sputtered directly onto the sample. These transducers operate efficiently at frequencies up to 3 GHz, corresponding to acoustic wavelengths of the order of 2 μm. By measuring the phase of high‐order multiple echoes, changes in sample thickness and/or velocity of parts in 109 can be detected. The method has been used to determine the phase diagram of the metamagnet dysprosium aluminum garnet for magnetic fields parallel to [001]. General agreement with earlier determinations based on thermodynamic measurements is obtained.

Ultrasonic test equipment

Abstract: PURPOSE:To improve the precision of flaw detection by detecting the relative speed between an ultrasonic test equipment and a body to be detected by a detecting means and converting it into an electric signal, and controlling the rotating speed of a driving means by a control means on the basis of the electric signal. CONSTITUTION:An ultrasonic transducer 3 is fixed to a center fixation shaft 2 fixed to the main body of the ultrasonic test equipment through a fitting member 1. Further, tire side members 4a and 4b are fixed rotatably on the shaft 2 through bearings 5a and 5b. Nearly cylindrical urethane 6 is fixed as a tire outer peripheral part is fixed nearby outer peripheries of the members 4a and 4b and an ultrasonic transmission medium 8 is held in the tire 7 consisting of the urethane 6 and members 4a and 4b watertightly with a seal 9. An ultrasonic wave 10 transmitted by the transducer 3 is propagated in the medium 8 to enter the object body 11 through the tire outer peripheral part made of the urethane 6, and then propagated in the object body; and a reflected wave from the object body 11 is detected by the transducer 3 and a signal analyzing device analyzes the presence, kind, etc., of a defect.

Calibration of ultrasonic transducers

Abstract: An ultrasonic test set is calibrated in terms of its frequency characterization by establishing a response trace on a monitor screen of the test set when the probe of the test set is applied to a standard test article, a digitizing camera is arranged for scanning the trace on the test set monitor, and a digital computer receives the digital output signal on the digitizing camera and processes the signal by sampling the signal trace at discrete points with respect to time; the digital computer provides an output on output means such as a monitor screen and/or printer which provides information on the frequency characterization of the ultrasonic test device and includes a frequency spectrum. The apparatus can be implemented by a combination of commercially available and known separate elements providing a cheap and effective apparatus and method for calibration purposes.

High Frequency Ultrasonic Characterization of Sintered SiC

Abstract: High frequency (60 to 160 MHz) ultrasonic nondestructive evaluation was used to characterize variations in density and microstructural constituents of sintered SiC bars. Ultrasonic characterization methods included longitudinal velocity, reflection coefficient, and precise attenuation measurements. The SiC bars were tailored to provide bulk densities ranging from 90 to 98 percent of theoretical, average grain sizes ranging from 3.0 to 12.0 microns, and average pore sizes ranging from 1.5 to 4.0 microns. Velocity correlated with specimen bulk density irrespective of specimen average grain size, average pore size, and average pore orientation. Attenuation coefficient was found to be sensitive to both density and average pore size variations, but was not affected by large differences in average grain size.