Showing papers on "Ultrasonic testing published in 1981"

Quantitative broadband ultrasonic backscatter: An approach to nondestructive evaluation in acoustically inhomogeneous materials

Abstract: The use of a broadband backscatter technique to obtain the frequency dependence of the longitudinal-wave ultrasonic backscatter coefficient from a collection of scatterers in a solid is investigated. Measurements of the backscatter coefficient were obtained over the range of ultrasonic wave vector magnitude-glass sphere radius product between 0.1 and 3.0 from model systems consisting of dilute suspensions of randomly distributed crown glass spheres in hardened polyester resin. The results of these measurements were in good agreement with theoretical prediction. Consequently, broadband measurements of the ultrasonic backscatter coefficient may represent a useful approach toward characterizing the physical properties of scatterers in intrinsically inhomogeneous materials such as composites, metals, and ceramics, and may represent an approach toward nondestructive evaluation of these materials.

2. Ultrasonic Wave Velocity and Attenuation Measurements

Abstract: Publisher Summary This chapter describes the ultrasonic wave velocity and attenuation measurements. The measurement of the velocity and attenuation of ultrasonic waves have been the basis of evaluation of a wide variety of physical properties of gases, liquids, and solids. In some cases, the measurements have been made with great precision and accuracy. In other cases, the ready availability of the result was more important than extreme precision. A number of sources of error need to be considered if one is measuring velocity and attenuation. In the first place, error is associated with the measurement of such quantities as time and distance. The measurement of velocity involves measurement, either of the time required for the ultrasonic wave to travel a known distance or of the wavelength and frequency. An insidious source of error in velocity measurements in solids is the effect of the transducer producing the ultrasonic waves and of the bond coupling the transducer to the sample. The investigations of the effect of diffraction on velocity and attenuation measurements for the case of circular, axially concentric transmitting and receiving transducers of the same radius are also presented.

Calibration and Performance Evaluation of Miniature Ultrasonic Hydrophones Using Time Delay Spectrometry

Abstract: A novel calibration method suitable for performance evaluation of hydrophones for ultrasonic dosimetry in the frequency range between 1 and 10 MHz is described. The principal advantage of this method over conventional discrete frequency calibration is that it is able to detect rapid and significant variations in frequency response of the ultrasonic hydrophones due to e.g. spurious mechanical resonances. The method employs Time Delay Spectrometry (TDS) technique which not only facilitates assessment of the hydrophone free field parameters in reflective environments but also allows both frequency response and directivity patterns of the ultrasonic hydrophone probes to be determined as a continuous function of frequency. The advantages and limitations of the TDS technique are pointed out.

Method and apparatus for ultrasonic testing of tubular goods

Abstract: The present invention relates to an improved method and apparatus for ultrasonic testing of tubular goods. With the object in mind to provide an ultrasonic test apparatus and method for testing tubular goods that effect plural modes of examination simultaneously and without need for rotation of the tubular goods, a circular array of ultrasonic transducers is provided which examine for each of transverse and longitudinal defects while additional transducers within the same array verify wall thickness of the tubular specimen. Slidable seal enclosure means maintains fluid energy couplant in envelopment of the circular array while allowing axial movement of the test specimen relative thereto. The array and enclosure may be constructed with attached motive means for carrying the array along the horizontal tubular goods while testing, or the array and enclosure may be associated with stationary support structure including motive means for driving the tubular goods axially through the array while testing.

Automatic calibration system for ultrasonic inspection

Abstract: A method and apparatus is disclosed for calibrating an ultrasonic inspection system having a plurality of transducers (12a, 12b, 12c) coupled by a common amplifier (16) to a distance-amplitude correction (D-AC) circuit comprised of a multiplying digital-to-analog converter (26') which receives, as a function of the transit time of an ultrasonic signal measured by a clock counter (34), a D-AC correction stored in a look-up table in a random access memory (24'). The D-AC correction function stored in the look-up table for each transducer is the inverse of a return signal response curve determined by measuring the peak amplitude of return signals from calibration holes at known depths in a test block (10) while in a calibrate mode, i.e., with a switch (SW) in a state to bypass the MDAC. An equation of a curve that best fits the peak measurements is then found by a digital computer (20) and used to determine the values of points along a curve superimposed on the response curve, except at near field where the calibration system is provided with truncation for near-field effects. Inverse values of these points are then stored in the look-up table for use as correction factors applied to the amplitudes of return signals during an inspection mode of operation. In that way, all return signals from flaws of the same size are caused to have the same amplitude regardless of depth, without the need for utilizing tedious and time-consuming manual calibration methods.

Ultrasonic tire testing apparatus

Abstract: An ultrasonic, non-destructive inspection system for detecting separations and/or holes in vehicle tires. The system employs a through transmission method at ultrasonic inspection in which the ultrasonic transmitter array and the ultrasonic receiver array are both mounted in air and in a non-contacting, non-critical relationship with the tire undergoing inspection. The inspection is performed in one revolution of the tire. The ultrasonic transmitters are pulsed and the receivers are sampled during predetermined time intervals which are related to the transmitter/receiver/tire geometry. This eliminates the problems of talk-around and standing waves. The problem of transmitter--transmitter interference is eliminated by transmitter frequency separation and transmitter array pointing geometry. The problem wherein tread pattern fluctuations in the received signal interfere with flaw detection is eliminated by the use of a finite sampled data filter whose period is adjusted to the period of the tread pattern.

Ultrasonic inspection apparatus

Abstract: An ultrasonic inspection apparatus for inspecting a test piece includes an ultrasonic transducer for transmitting test signals into the test piece, for receiving associated response signals reflected back thereto, and for generating a defect signal when a response signal indicates an abnormal condition in the test piece. A control signal generator generates a control signal at predetermined intervals of distance of movement of the transducer relative to the test piece while the transducer generates test signals at a frequency independent the control signal frequency. A principal counter counts the control signals and generates an alarm signal when its count exceeds a value indicating that sufficient defect signals have been generated during movement of the transducer over a predetermined distance to confirm the presence of an unacceptable abnormal condition. A reset counter is connected to the control signal generator for also counting the control signals, is connected to the transducer for receiving defect signals therefrom, and is connected to the principal counter for generating a reset signal therefor. The reset counter is reset by each of the defect signals and generates one reset signal when its count exceeds a predetermined amount indicative of the maximum distance of movement of the transducer during which a defect signal may not be generated from an unacceptable abnormal condition.

Probes for the ultrasonic treatment or inspection of molten aluminum.

Abstract: Special probes (1) for the ultrasonic inspection or treatment of molten aluminum. Such probes employ a special working tip (5) which is made essentially of titanium and is capped with a coating of aluminum by a vacuum vaporization process. Also described is a process for making such probes.

Ultrasonic inspection and deployment apparatus

Abstract: An ultrasonic inspection apparatus for the inspection of metal structures, especially installed pipes The apparatus combines a specimen inspection transducer (43, 44) an acoustical velocity sensing transducer (42), and a surface profiling transducer (41), all in a scanning head (7) A bellows (54) attached to the scanning head contains a volume of oil (51) above the pipe surface (3), serving as acoustical couplant between the scanning head and the pipe The scanning head is mounted on a scanning truck (1) which is mobile around a circular track (2) surrounding the pipe The scanning truck has sufficient motors, gears, and position encoders to allow the scanning head six degrees of motion freedom A computer (23) continually monitors acoustical velocity, and uses that parameterto process surface profiling and inspection data The profiling data is used to automatically control scanning head position and alignment and to define a coordinate system used to identify and interpret inspection data The apparatus is suitable for highly automated, remote application in hostile environments, particularly high temperature and radiation areas

Tool for inspecting defects in irregular weld bodies

Abstract: A tool for manipulating an ultrasonic inspection transducer is actuated to move the transducer over the surface of an irregular weld body. The weld body disclosed, joins the nozzle of a reactor vessel to its vessel, the irregularity of the weld body defined by the intersection of the two cylinders. The transducer is moved over the surface of the weld body and actuated to scan through a predetermined angle in relation to the changing aspect of the geometry of the weld body by a cam mounted at the pivoting center of the tool.

Ultrasonic flaw detection of a pipe

Abstract: A method of ultrasonic flaw detection of a pipe, worth particularly for instance for a heater pipe as is used for catalytic gas reforming with steam. A transmitter probe and a receiver probe are disposed on the pipe outer surface with suitable spacing one from the other both in axial or longitudinal direction and in peripheral direction of the pipe. The transmitter probe launches ultrasonic radiation under proper angle of incidence upon the pipe outer surface at the point of entering material of the pipe, to be refracted under a particular angle of refraction so that it may then pass through the material of the pipe straight to another point upon the pipe outer surface. The receiver probe receives the ultrasonic radiation transmission echo. Flaw in the material of the pipe is detected from fluctuation of the echo, as seen upon scanning the pipe surface by moving the transmitter and receiver probes.

Potential and limits of holographic reconstruction algorithms

Abstract: For the purpose of ultrasonic nondestructive testing of materials, holography in connection with digital reconstruction algorithms has been proposed as a modern tool to extract crack sizes from ultrasonic scattering data. Defining the typical holographic reconstruction algorithm as the application of the scalar Kirchhoff diffraction theory to backward wave propagation, we demonstrate its general incapability of reconstructing equivalent sources, and hence, geometries of scattering bodies. Only the special case of a planar measurement recording surface, that is to say, a hologram plane, and a planar crack with perfectly rigid boundary conditions parallel to the hologram plane and perpendicular to the incident field yields a nearly perfect correlation between crack size and reconstructed image; the reconstruction algorithm is then referred to as the Rayleigh-Sommerfeld formula; it therefore represents the optimal case matched to that special geometrical situation and, hence, may be interpreted as a quasi-matched spatial filter. Using integral equation theory and physical optics, we compute synthetic holographic data for a linear cracklike scatterer for both plane and spherical wave incidence, the latter case simulating a synthetic aperture impulse echo situation, thus illustrating how the Rayleigh-Sommerfeld algorithm or its Fresnel approximation increasingly fail for cracks inclined to the hologram plane and excited nonperpendicularly. Furthermore, we point out how the physical data recording process may additionally influence the reconstruction accuracy, and, finally, guidelines for a careful and serious application of these holographic reconstruction algorithms are given. The theoretical results are supported by measurements.

Probe for the ultrasonic inspection of molten aluminum.

Abstract: PROBE FOR THE ULTRASONIC INSPECTION OF MOLTEN ALUMINUM An ultrasonic testing probe for molten aluminum comprises a probe body having substantially flat end surfaces, one of which forms a working tip and the other receives an ultrasonic transducer, and cooling means surrounding the body at a location between the two ends. The probe body is composed essentially of titanium and has a working tip of 1/8 to 3 inches in length, while the cooling means is adjacent to the working tip and has the capacity of establishing at equilibrium a negative temperature gradient of at least 200.degree.C per inch along the longitudinal axis of the body when the working tip is immersed in molten aluminum, the second end being maintained below 300.degree.C. JHB-16.8.1982 23421

Method of acoustic emission testing of steel vessels or pipelines, especially for nuclear reactor installations

Abstract: Method of acoustic-emission testing of a steel component such as a vessel of pipeline especially of primary circulatory loops of nuclear reactor installations wherein the component, on one hand is subjected to a pressure medium, such as water, and, on the other hand, to ultrasonic pulses emitted during deformation development resulting from growth of cracks therein or from leaks and transmitted through the component, which includes detecting and amplifying the ultrasonic pulses with equipment, respectively, formed of test probes, which are disposed so as to determine respective sources of acoustic emission due to differences in transmission time of the ultrasonic pulses through the component, and of electronic amplifiers operatively associated with the test probes, and then feeding a resultant amplified defect signal from the equipment to a display, the equipment being tuned to reception of a frequency band of acoustic-emission spectrum which is above a limiting frequency fG defined by the relationship: ##EQU1## wherein d is the wall thickness of the component being tested.

Ultrasonic velocity for estimating density of structural ceramics

Abstract: The feasibility of using ultrasonic velocity as a measure of bulk density of sintered alpha silicon carbide was investigated. The material studied was either in the as-sintered condition or hot isostatically pressed in the temperature range from 1850 to 2050 C. Densities varied from approximately 2.8 to 3.2 g cu cm. Results show that the bulk, nominal density of structural grade silicon carbide articles can be estimated from ultrasonic velocity measurements to within 1 percent using 20 MHz longitudinal waves and a commercially available ultrasonic time intervalometer. The ultrasonic velocity measurement technique shows promise for screening out material with unacceptably low density levels.

High temperature pressure coupled ultrasonic waveguide

Abstract: A pressure coupled ultrasonic waveguide is provided to which one end may be attached a transducer and at the other end a high temperature material for continuous ultrasonic testing of the material. The ultrasonic signal is coupled from the waveguide into the material through a thin, dry copper foil.

Application of ultrasonic testing techniques on austenitic welds for fabrication and in-service inspection

Abstract: This paper describes some practical considerations relating to the ultrasonic testing of weld joints in austenitic components, based on the author's experience with components manufactured for, and in service in, nuclear power stations. Problems caused by the effect of grain structure, spurious indications and attenuation of the ultrasound are discussed. The importance of acquiring adequate data from reference blocks is emphasized, and the uses and limitations of various types of angle probe are illustrated.

Program for field validation of the synthetic aperture focusing technique for ultrasonic testing (SAFT UT). Quarterly progress report, November 1980-January 1981

Abstract: The purpose of the project is to validate the usefulness of SAFT UT for industrial nondestructive evaluations (NDE). SAFT UT is an ultrasonic imaging method for accurate measurement of the spatial location and extent of acoustically reflective surfaces (flaws) contained in objects such as structural components and weldments in nuclear power reactor systems. The increased measurement accuracy offered by SAFT, when compared with that provided by measurement methods now in use, will improve the reliability of flaw severity assessments with resultant safety and economic benefits to the nuclear power industry.

Ultrasonic measuring instrument

Abstract: An instrument for distinguishing between gray and ductile cast iron pipes. Signals from a relatively movable pair of ultrasonic probes and a distance transducer are inputs to a circuit for generating a signal related to the velocity of sound through a chord of a pipe.

Ultrasonic wave measuring apparatus

Abstract: PURPOSE:To achieve measurement of ultrasonic waves without errors free from effect on the damping of ultrasonic waves due to bubbles by correcting time until ultrasonic waves are received counting the frequency at which signals of ultrasonic waves exceed a specified level. CONSTITUTION:The frequency N at which ultrasonic waves received by an ultrasonic wave receiver 1 exceed a set level is counted with a counting circuit 4 through a comparator 3. A computing circuit 5 determines a correction value H based on the table to correct measured time between the transmission of the ultrasonic waves and the receiving thereof. This enables the measurement of ultrasonic waves without errors free from effect of possible damping when ultrasonic waves damped due to bubbles or the like. In the table, DELTAT represents time corresponding to one wave length of the ultrasonic wave signals.

Tube-internal test probe in accordance with the ultrasonic pulse echo method for measuring wall thickness on grainy surfaces, preferably for verifying corrosion in tubes

Abstract: For testing for corrosion of narrow thin-walled tubes which are only accessible from the inside, a measuring system is described which operates in accordance with the pulse echo method and makes it possible to measure the accurate position and extent of the defect with high resolution at each place in the tube whilst simultaneously accurately measuring the remaining wall thickness. The position of the wear on the inside or the outside wall is also measured by on-line displaying of the enlarged tube cross-section on a screen. The measuring system consists of the actual internal test probe and the associated evaluating device: the probe is equipped with a rotating ultrasonic test head which irradiates the inside tube wall in the radial direction and scans it helically. The probe is driven by an inbuilt motor with transmission, from the current pulses of which information on the angular position of the rotor is obtained. Inflow and outflow of the coupling medium into and out of a chamber formed from sealing rings is carried out by means of hoses or tubes. The evaluating device contains an electronic circuit which supplies one or respectively two measurement values with each individual transmitted pulse. The internal radius of the tube is derived from the transit time between the transmitted pulse and the echo of entry into the tube wall and the wall thickness is derived from that between entry and rear wall echo. Their combination provides the external radius. From the motor current pulses, electrical values for the angular position are generated taking into consideration the transmission step-down ratio.

Pulse‐echo ultrasonic interferometer for the automatic measurements of velocity and attenuation changes

Abstract: An automatic pulse‐echo ultrasonic interferometer for continuous measurements of sound velocity changes is described. Velocity resolution of about 1 ppm was obtained for a single transit echo. It is an improvement over results obtained by a previous unautomated version of the pulse‐echo interferometer. A simultaneous detection of the amplitude of the measured echo is also possible in this system. Measurements of velocity and attenuation shifts of a surface acoustic wave propagating on an ST‐cut quartz, while being copper deposited, are given.

New instrument for rapid measurement of changes in ultrasonic velocity

Abstract: A new instrument for rapid measurement of changes in ultrasonic velocity in a material has been developed. The changes in velocity are recorded automatically with the time difference between reflection and transmission waves. The minimum recording interval is 1 ms. The relative accuracy is from 10−3 to 10−4 for the velocity change in a sample length of about 6 mm. Two applications are reported.

Electronic scanning type ultrasonic test equipment

Abstract: PURPOSE:To detect a flaw of a stable picture quality with high accuracy, by using an array type probe on which plural vibrators for transmitting and receiving an ultrasonic wave have been provided in parallel, and controlling the timing for energizing and reception of the vibrator. CONSTITUTION:n-number of vibrators 1 provided in parallel are cupled with n- number of ultrasonic transmitters 2, are energized, and an ultrasonic wave is transmitted. A receiving signal detected by the vibrator is amplified, and thereafter, is inputted to an A/D converter 5, and is digitally converted. To the converter 5, a trigger signal is inputted from a receiving delay setting device 6. To transmitting and receiving delay setting devices 3, 6, the timing for sending out a trigger signal is set by a signal from a computer 7. By matching an output time point of the converter 5, the signal is stored in a memory 8, adding it by n-number each. A signal processor 9 selects a range of a beam route for processing the signal by the signal from the computer 7, sets a threshold level, and adds picture sweeping and luminance modulation to a picture display 10 by whether said range has exceeded the level or not, so that a flaw detecting waveform can be observed.

Ultrasonic detection and sizing of two‐dimensional defects at long wavelengths

Abstract: An ultrasonic technique is described for detecting and sizing of two‐dimensional defects. The technique is particularly suitable for detecting two‐dimensional defects in certain butt‐weldments which cannot be fully inspected by conventional radiographic and ultrasonic methods. Use is made of noncontact, electromagnetic‐acoustic transducers to excite and detect shear horizontal (SH) wave probing signals where wavelength is long compared to the defect depth dimensions. The new technique is demonstrated in conjunction with a weld fatigue testing investigation in which it is used to detect natural weld defects and to monitor crack initiation and growth under tension‐tension fatigue loading. An experimental calibration curve is given for sizing two‐dimensional surface defects, and the experimental results are explained in terms of a reciprocity relationship evaluated in the elastostatic limit.

Ultrasonic testing method and apparatus

Abstract: An ultrasonic testing method permits investigating the nodal point in the profile of a cast wheel of a motor vehicle between clinch and wheel flange. Hollow spaces occurring in this area may be tolerated when the remaining wall thicknesses between the profile legs do not drop below a certain thickness. In order to be able to check a wheel in one single measuring process and with a simple measuring geometry, two of the three intermediate leg parts are tested by direct testing by an evaluation of the echo height in consequence of lateral contraction of ultrasonic energy or in consequence of partial reflection which allows one to make conclusions with regard to the cross section and sound spots of the material through which ultrasound was sent, while the remaining part is measured by means of a simple travel time transversely to the residual wall. An apparatus for performing this method is disclosed.