Showing papers on "Ultrasonic testing published in 1986"

Ultrasonic testing of materials

Abstract: An ultrasonic apparatus for testing a material comprises an oscillator (10) which generates a selected frequency in the ultrasonic range. A transducer (1) is connected to the oscillator (10) for applying an ultrasonic signal to the material and for receiving an echo signal back from the material. A phase detector (5) receives the echo signal and an in-phase oscillator signal to generate a first display signal, and a phase detector (6) receives a quadrature signal (90° out of phase from the oscillator signal) and the echo signal to generate a second display signal. The first and second display signals are utilised in a visual display, such as a cathode ray tube (8), to generate an image. The image changes according to the phase shift between the ultrasonic signal transmitted into the material and the echo signal, which, in turn, can be utilised to determine the presence and depth of a flaw or boundary in the material.

SAFT — the evolution of a signal processing technology for ultrasonic testing

Abstract: This paper is a review of the development of the synthetic aperture focusing technique (SAFT) for use in ultrasonic testing. The equations for processing the data using the SAFT algorithm in several modes are described. This paper also compares the results obtained using full 3D processing against line SAFT processing. It then briefly discusses ways to reduce the processing time for the SAFT algorithm.

Quantitative grain size evaluation using ultrasonic backscattered echoes

Abstract: Grain size characterization using ultrasonic backscattered signals is an important problem in nondestructive testing of materials. In this paper, a heuristic model which relates the statistical characteristics of the measured signal to the mean ultrasonic wavelet and attenuation coefficient in different regions of the sample is investigated. The losses in the backscattered signal are examined using temporal averaging, correlation, and probability distribution functions of the segmented data. Furthermore, homomorphic processing is used in a novel application to estimate the mean ultrasonic wavelet (as it propagates through the sample) and the frequency‐dependent attenuation. In the work presented, heat‐treated stainless steel samples with various grain sizes are examined. The processed experimental results support the feasibility of the grain size evaluation techniques presented here using the backscattered grain signal.

Ultrasonic method to determine gas porosity in aluminum alloy castings: Theory and experiment

Abstract: The characterization of porosity in solids using the frequency dependence of the ultrasonic attenuation is discussed both from the theoretical and experimental viewpoint. The major thrust of our work is the determination of the volume fraction and size of the voids for the case of dilute porosity (<6%) in structural materials. An aluminum alloy (A357) was chosen for study due to its economic importance in large‐scale casting and the particular suitability of aluminum for this type of study. Following recent papers the attenuation is described by an independent scatterer model for spherical voids. Numerical results are presented in a form suitable for use with a range of materials. A method for determining the volume fraction and pore size is given. Specific tabular results are given for stainless steel, IN‐100, Ti, Si3N4, as well as aluminum. Figures of merit which partially describe those situations in which the method is usable are also presented. In the experimental work a digitized spectrum analysis system was used to measure the frequency dependence of the attenuation coefficient in A357 aluminum cast alloys. In the cast materials the average pore size was in the order of 100 μm and the pore concentration varied from essentially 0 to 6%. It was found that experimental measurement of the attenuation could be fit by the theoretical model. The resulting parameters yield a good estimate of the pore volume fraction.

Method and system for ultrasonic detection of flaws in test objects

Abstract: A method, apparatus and system for the ultrasonic detection and evaluation of flaws in annular test objects including an arrangement of ultrasonic transducers that are rotated about the outer surface of the test object and provide an ultrasonic indication fo flaws in the object, and for electronically collecting, storing, and analyzing the flaw data gathered by the ultrasonic transducers, to further provide a predetermined objective indicia of acceptablility concerning the structural integrity of the test object.

Corrosion monitoring in industrial plants using nondestructive testing and electrochemical methods

Abstract: The nondestructive testing (NDT) section begins with a paper that discusses the attributes of neutron radiography and its advantages over other NDT methods. Other techniques examined in this section include ultrasonic test systems, acoustic emission, a computer-based automated system, ultrasonic imaging, and eddy current. Section two begins with a review of electrochemical methods of monitoring corrosion. Topics covered include polarization resistance, stress corrosion cracking, localized corrosion, polarization diagrams, hydrogen probes, AC impedance, and occluded cell corrosion.

Ultrasonic instrument to measure the gas velocity and/or the solids loading in a flowing gas stream

Abstract: A flow meter (10) particularly adapted for measuring the mass flow rate of pulverized coal being introduced into large scale power generation boilers. The meter includes a transmitter (14) which generates a pulsed beam of ultrasonic impulses. A receiver (18) is positioned across the flow filed from the transmitter and receives the ultrasound pulses. The meter measures the downstream drift of the ultrasound pulses and their attenuation which is related to flow velocity and concentration, respectively. The instrument includes electronic circuitry (28) for automatically adjusting the relationship between transmitter and receiver, and performs numerical analysis routines on the signal outputted from the receiver to provide a signal related to coal concentration and velocity.

Variable angle transducer system and apparatus for pulse echo inspection of laminated parts through a full radial arc

Abstract: A system and apparatus for ultrasonic pulse echo inspection of corners in laminated parts. A variable angle transducer including transducer, fixed reflector, and rotating reflector which effects scanning of the radial arc being tested by the sonic output from the transducer provides ultrasonic information which is processed through an ultrasonic signal processing system which digitizes, stores and displays the information.

A Therapeutic Ultrasound System Incorporating Real-Time Ultrasonic Scanning

Abstract: A system has been developed combining a real-time B-scan unit with a high-intensity, focused, therapeutic ultrasound system. This system permits precise aiming of focused therapy beams; it also provides viewing and data collection of diagnostic information concurrently with therapeutic applications. The device consists of a standard rapid-scan diagnostic probe mounted on our conventional therapeutic transducer assembly. A plastic scaled overlay of the therapeutic beam profile is placed over the diagnostic B-scan system's monitor. Simple targets have been developed to assure proper alignment of the components. The system has been used to apply intense ultrasound to tissue and to monitor the insonified tissue during and immediately after insonification. Dynamic responses within tissues and test targets have been documented. The system is being applied clinically for hyperthermia induction in ocular tumors. It is also being used in animal experiments involving ultrasonic tumor ablation, vitreous-membrane disruption and vitreous-hemorrhage dispersion.

Theoretical comparison of ultrasonic signal amplitudes from smooth and rough defects

Abstract: The effects of surface roughness on ultrasonic wave scattering from planar, crack-like defects are examined using a theoretical approach. The mean, or coherent, amplitude scattered in and around the specular direction is evaluated in the far field of the defect. An estimate of the random, or diffuse, component of the scattered field is then made. The defects are taken to be rectangular in shape, with a random roughness varying in one direction only, such that the two faces of the defect are ‘corrugated’. No interactions between the two defect faces occur. The response of these defects to a continuous plane wave is evaluated using elastic Kirchhoff theory, leading to restrictions on the rate of change of surface gradient. Results from this work are of relevance to ultrasonic testing techniques using the specular, or near specular, signal, eg near-normal pulse-echo investigations or tandem inspection of vertical, or near-vertical, defects. Both direct and mode-converted signal amplitudes are calculated and the variation of these signals with increasing surface roughness is discussed. Considerable decreases in specular signal (up to ∼ 13 dB) can be expected for average roughnesses of about 1 10 of the incident wavelength, depending on the incident and scattered wavemodes.

Matrix Array Transducer and Flexible Matrix Arry Transducer

Abstract: A 3.5MHz matrix array transducer (MAT) which has 2560 small 1.5mm-square elementary vibrators arranged two-dimensionally in 80 rows along the X-axis and 32 columns along Y-axis has been developed. The use of a silicon adhesive for bonding together small 2mm-square vibrator of 3MHz has made it possible to produce a flexible matrix array transducer (FMAT). A 2.3MHz circular matrix array transducer (CMAT) with 288 elements of 2x5mm-square circularly arranged in 36 rows and 8 columns in width has been developed for nondestractive inspection of steel thick wall pipes being used in a nuclear reactor. The resultant characteristics of these transducers are described.

Ultrasonic system for the detection of transient liquid/gas interfaces using the pulse‐echo technique

Abstract: An ultrasonic method has been chosen to examine liquid/gas interfacial areas in closed systems. Although commercial equipment was used for the transducer and ultrasonic analyzer, commercial transient memory devices were inadequate. Consequently, a real‐time data analysis and transient memory (DATM) unit was designed and constructed. A series of flight times for a succession of 1024 signals are calculated and recorded in the transient memory. The system clock operates at 10 MHz and increments a 12‐bit binary counter. The counter is capable of measuring return signal times as long as 212 μs (4.096 ms) with a 1‐μs resolution. The data are available as analog voltages for display on an oscilloscope or the digital data may be directly transferred to a microcomputer for analysis, display, or archival storage. The DATM device was successfully applied, collecting data for the analysis of rising bubbles in metallurgical systems and two‐phase flow in horizontal tubes.

Method and device for magnetic and ultrasonic testing of ferro-magnetic objects

Abstract: The subject of the invention is a method and a device for non-destructive testing of ferromagnetic bodies (1) for structural faults. The bodies (1) are magnetized. Structural faults cause changes in the magnetic field pattern which are measured with magnetic field detectors (6). Surface waves are generated electro-dynamically utilizing the magnetic field generated for magnetizing the body (1). Those structural faults extending up to the surface can be detected with the surface waves. To distinguish between the structural faults extending to the surface of the body at one point and those structural faults inside the body (1), it is determined whether the measured values gained both from the leakage flux and from the surface waves indicate structural faults or whether only the measured values gained from the leakage flux indicate structural faults.

Apparatus and technique for reconstruction of flaws using model‐based elastic wave inverse ultrasonic scattering

Abstract: An automated multiviewing ultrasonic apparatus and signal processing routine have been developed for utilization in nondestructive evaluation (NDE) of materials. The instrument has been developed to take advantage of recent advances in long and intermediate wavelength inverse scattering of elastic waves, and provides a 3‐D reconstruction of a flaw. Although the reconstruction obtained does not contain fine details of the flaw’s structure, it provides sufficient information about the flaw (size, orientation, and selected materials properties) so that failure‐predictive decisions can be made.

Ultrasonic inspection system

Abstract: An ultrasonic inspection system for performing in-service inspection of atomic reactors and the like includes a remote inspector including a transducer holding device of novel design and function. The holding device basically comprises an outer housing; an inner housing rotatably retained within said outer housing; an ultrasonic transducer retained within said inner housing; retention means for selectively positioning said transducer within said inner housing; and means for locking said transducer within said inner housing at a selected position.

Method for installing offshore jack-up structures

Abstract: A method for installing an offshore jack-up structure having a buoyant platform to be towed and a plurality of legs, the method comprising the steps of: (a) providing a pair of ultrasonic transmitter-receivers on a longitudinal and horizontal center line of the platform, (b) providing of ultrasonic transmitters on a longitudinal and horizontal center line of a target structure to which the rig is approached; and (c) receiving signals transmitted from the ultrasonic transmitters of the target structure by the ultrasonic transmitter-receivers of the platform to determine a relative distance between the rig and the target structure.

On ultrasonic detection of surface features

Abstract: Ultrasonic range finding is an inexpensive means of obtaining 3-dimensional information about the surrounding environment. Because of this ultrasonic detection methods have received considerable attention recently, particularly in the robotic community. Unfortunately, ultrasonic range finding suffers from shortcomings that are not found in more expensive techniques such as laser range finding. For example, a laser range finder can determine both range from the sensor and location of the reflection surface due to the narrow beam used. The ultrasonic range finder beam is much larger and reflection surface location can only be determined approximately for any single range sample (it is only known that a reflecting surface lies somewhere on a segment of the surface of a sphere of range radius centered on the sensor). This paper discusses techniques for obtaining much better surface information under certain conditions. These techniques form the foundation for more sophisticated methods described in another paper for extracting surface features. The techniques can be used with other range sensors and look particularly promising for adaptively controlling a laser range finder. We will outline the mathematical techniques employed and discuss some experience obtained with a robot mounted ultrasonic range sensor.

Test piece for ultrasonic testing

Abstract: A device is provided for ultrasonic testing, particularly for monitoring the measuring precision and the calibrating of high resolution ultrasonic testing apparatus or ultrasonic testing heads. The device includes a powder-metallurgically produced test piece element. The test piece element includes insert elements immovably fixed to an interior surface of a capsule. Powder is provided in the capsule which is poured to surround the immovably fixed insert elements. The powder is subjected to changed temperature and pressure thereby forming the test piece. A process for producing the apparatus is also provided.

Ultrasonic inspection apparatus and method for locating multiple defects in eccentric wall tubular goods

Abstract: An ultrasonic inspection apparatus is shown for locating multiple defects in eccentric wall tubing or goods. A plurality of transducers are arranged in mated pairs, each of the pairs including a sender element for transmitting an ultrasonic shear wave and a receiver element for receiving a reflected ultrasonic wave component from the tubular goods being inspected. Each sender element is a point focus transducer having sufficiently high resolution to maintained detectability of defects in the tubular goods. Each receiver element is a wide focal width transducer having a large effective beam width area to compensate for eccentricity in the wall of the tubular goods.

Procedure for flaw detection in cast stainless steel

Abstract: A method of ultrasonic flaw detection in cast stainless steel components incorporating the steps of determining the nature of the microstructure of the cast stainless steel at the site of the flaw detection measurements by ultrasonic elements independent of the component thickness at the site; choosing from a plurality of flaw detection techniques, one such technique appropriate to the nature of the microstructure as determined and detecting flaws by use of the chosen technique.

Apparatus and method for sending out and receiving ultrasonic wave signals

Abstract: An ultrasonic inspection apparatus and method in which a linear array of acoustic transmitters and receivers are disposed adjacent to a workpiece, and alternating potential source is connected to some of the acoustic transmitters to project a side lobe of an acoustic wave toward a specific zone of the workpiece. Thereafter, the connections between some of the acoustic transmitters and the potential source are automatically changed, to move the specific zone as many times as may be necessary to provided scanning of the workpiece.

Ultrasonic inspection system with linear transducer array

Abstract: Ultrasonic inspection apparatus includes a linear array of transmitting transducers and a linear array of receiving trans­ducers providing TTU mode ultrasonic inspection. One to four transmitting transducers may be simultaneously pulsed as a group, and one to four receiving transducers may be simultaneously con­nected in common in a group by operation of a connection circuit. The connection circuit includes a plurality of multiplexor cir­cuits having their signal inputs connected in common to respec­tive receiving transducers and their address terminals connected to the data output terminals of programmable read only memory de­vices. Calibration means are provided for correcting the output signals produced by the receiving transducers to compensate for variations in the response of individual transducers.

Ultrasonic imaging of layered structures utilizing nondestructive subnanosecond photoacoustic pulse generation

Abstract: We describe a photoacoustic ultrasonic imaging system that can provide separate acoustic information on a thick substrate and a thin coating simultaneously. This is achieved by generating an ultranarrow longitudinal pulse on the opaque layered sample, and detecting the series of substrate and coating echoes in high time resolution. The echo times, attenuations, and acoustic dispersions in each series provide information on the substrate or coating separately. New photoacoustic images of coatings and of substrates for coated ceramic substrates are presented.

Ultrasonic Pin Scanning Microscope a New Approach to Ultrasonic Microscopy

Abstract: SZRdbaARY An acoustical scanning microscope having a pin probe instead of acoustical lens was developed. The probe is a cone ahaped pin with ultrasonic transducer attached to broader 8urface.The narrower end which ie flat polished is located very close to polished surface of the sample. To avoid phase problems at the flat transducer the c onical probe has narrow opening angle of about 20 degress The probe can be made of material having very low acoustical losses like sapphire and well matched to the m aterial of the sample 80 the energy losses during acoustical signal transmiasion can be made very small. Thie enable us to make the tip of the pin very narrow to improve laterel resolution beyond the on e expected in a lens system at the same f requenay.

Ultrasonic test head

Abstract: An ultrasonic test head including an oscillating crystal (1). A damping body (2) is mounted on the side of the crystal which faces away from the sonic beam direction. The damping body includes a plurality of sound-conducting and sound-absorbing lamellae (3, 5) which are stacked alternately on one another and each have one side thereof coupled to the oscillating crystal (1) thereby providing a high acoustic impedance as well as a high acoustic absorption.

A Comparison of New Ultrasonic Cement and Casing Evaluation Logs With Standard Cement Bond Logs

Abstract: New ultrasonic inspection techniques have been implemented to evaluate cement bond and casing conditions. These techniques, relying on state of the art downhole, high-speed waveform digitization, can successfully determine cement voids and channels and also provide accurate bond information in the presence of a microannulus. The downhole microprocessor controlled electronics transmits the digitized waveforms to the surface for computations and display. The downhole waveforms are then viewed by the operator in real time to insure proper log quality. Numerous log examples showing comparisons with the standard Cement Bond Log (CBL) demonstrate that the accuracy and resolution of the new approach provide much more information. Casing conditions are determined using both acoustic caliper measurements and a new casing thickness measurement technique. The acoustic caliper measurement not only determines accurately the casing inside diameter, but also detects the pipe gap at casing collars. The new measurement determines actual casing thickness variations due to internal or external pipe wear or corrosion. Experimental results along with log examples show the effectiveness and accuracy of measuring the actual casing thickness at the well site in real time.

Application of Digital Pulse Shaping by Least Squares Method to Ultrasonic Signals in Composites

Abstract: For ultrasonic testing in composites, a signal processing tool is identified that can significantly enhance the sharpness of ultrasonic waveforms and provide clearer pictures of the nature of the material flaw. The technique artificially improves the resolution of the system to discrete events by pulse shaping the measured waveform based on the signal from a reference. The optimum pulse shape operator is determined from a least-squares method in the z-domain.

Evaluation of Ultrasonic Beam Models for the Case of a Piston Transducer Radiating Through A Liquid-Solid Interface

Abstract: In order to accurately predict the performance of immersion ultrasonic inspection techniques, it is necessary to have a model for the transducer radiation process. This model should include the case of propagation of the ultrasonic beam at oblique incidence through liquid-solid interfaces of complex geometries. Included should be the effects of diffraction, refraction, focussing and aberrations upon the beam shape.