Showing papers on "Ultrasonic testing published in 1978"

Method of forming and ultrasonic testing articles of near net shape from powder metal

Abstract: A method for sonic testing powder metal articles made by hot isostatic pressing in a thick-walled container including the steps of preparing the composite thick-walled container and article for sonic testing by machining sonic surfaces in the exterior surface of the thick-walled container and thereafter sonic testing the article through the walls of the container.

Phase insensitive acoustoelectric transducer

Abstract: Conventional ultrasonic transducers transform acoustic waves into electrical signals preserving phase and amplitude information. When the acoustic wavelength is significantly smaller than the transducer diameter, severe phase modulation of the electrical signal can occur. This results in anomalous attenuation measurements, background noise in nondestructive evaluation, and in general complicates data interpretation. This article describes and evaluates a phase-insensitive transducer based on the acoustoelectric effect. Theory of operation of the acoustoelectric transducer (AET) is discussed, and some optimization procedures outlined for its use. Directivity data for the AET are contrasted with a conventional piezoelectric transducer. In addition, transmission scanning data of phantom flaws in metal plates are presented for both transducers and demonstrate a significant improvement in resolution with the AET.

Ultrasonic couplant gel compositions and method for employing same

Abstract: Substantially non-pollutant and non-toxic water washable composition in the form of a gel for use in non-destructive ultrasonic inspection of surface and subsurface flaws and discontinuities in bodies comprising a (1) poly(oxypropylene) poly(oxyethylene) condensate having a molecular weight ranging from about 1,000 to about 15,000, and (2) silica, particularly fumed silica, such silica being present in certain proportions, e.g. about 5% by weight of the composition. The composition or gel is applied to a surface of a body such as a metal aircraft structural part, and a probe or transducer of an ultrasonic testing device is contacted or pressed against the gel, and the transducer is caused to move or slide in various directions on the gel to transmit ultrasonic energy through the gel and the object, to inspect the object and locate any surface or subsurface flaws or discontinuities.

Ultrasonic inspection device and method of inspection

Abstract: An ultrasonic inspection device for nondestructive inspection of cylindrical members includes a pair of resilient inspection wheels which house multiple ultrasonic transducers The inspection wheels are mounted in a carriage so as to ride along the surface of a rotating cylindrical member being inspected Relative longitudinal motion between the carriage and the cylindrical member allows the inspection wheels to transcribe helical paths over the surface of the member

Ultrasonic inspection system including apparatus and method for tracking and recording the location of an inspection probe

Abstract: An ultrasonic inspection system for inspecting objects, such as pipe, is disclosed which includes an ultrasonic inspection probe or search unit, and the usual ultrasonic transducers and electronics associated with the probe. The system also includes novel apparatus for continuously tracking and recording operation with respect to a reference point or area, on the object being inspected. For this purpose, the inspection probe includes one or more sources of radiant energy which are periodically actuated as the probe is moved about the object being inspected, and a plurality of receiving devices or microphones located at a fixed relationship with respect to the area being inspected or to a known reference point on the area, such as a weld. The location of the probe can be determined and recorded from information obtained by receipt of the signals from the source of radiant energy by two or more of the receiving devices. In order to permit the yaw of the inspection probe with respect to the centerline of the pipe to also be determined, and more accurately locate the inspection transducer of the probe at least two sources of radiant energy may be utilized at the inspection probe and the respective sources may be actuated at different time intervals to avoid interference between the tracking signals from the respective sources.

Ultrasonic inspection of a cylindrical object

Abstract: A method and an apparatus are provided for ultrasonically inspecting a cylindrical object. The object is placed between the poles of a magnet to create a circumferential magnetic field in the object. A group of electromagnetic transducers (EMAT's) are placed adjacent the material so that the transducers scan the entire object when it is rotated. When an RF signal is applied to the transducers, elastic waves are generated in the material. These elastic waves reflect from defects in the material and these reflections are received by the transducers.

Effects of embedded steel bars upon ultrasonic testing of concrete

Abstract: Synopsis Ultrasonic testing of a reinforced concrete member by means of the Pundit apparatus is affected by the steel bars embedded in the concrete. An investigation of the effects of the reinforcement has been made, using the bar diameter and the concrete strength as the variables. It is found that the steel bar appears to act compositely with the surrounding concrete in transmitting ultrasonic pulses. The effective pulse velocity is somewhat between the pulse velocities in the two separate media, and varies with the diameter of the bar and the pulse velocity in the concrete. An empirical formula for the effective pulse velocity is proposed. On the basis of this formula and further theoretical consideration, the zone of steel influence is defined. A correction factor is derived whereby the measured pulse velocity in a concrete–steel medium is adjusted to give the pulse velocity in the plain concrete.

Ultrasonic Testing for Determining Dynamic Soil Moduli

Abstract: Determination of dynamic E- and G-moduli of a silty clay material were made by measuring directly the velocity of both ultrasonic longitudinal and shear waves transmitted through the material. The equipment, developed at the University of Missouri-Rolla, allows dynamic, nondestructive testing of soil materials to be conducted rapidly and easily.

Pipe inspection system and method

Abstract: A portable apparatus for nondestructive ultrasonic inspection of oil field tubular goods includes a deck which mounts spaced drive rollers for rotating the pipe being inspected. A substantially box-shaped carriage moves on tracks above the pipe to allow a pair of ultrasonic inspection wheels to traverse the pipe. The combination of pipe rotation and carriage movement causes the inspection wheels to trace helical paths on the surface of the pipe. In an alternative embodiment, the rotating pipe is drive longitudinally through stationary ultrasonic equipment. A programmed control system and a method of ultrasonic inspection also are disclosed.

Automatic self-checking of test equipment

Abstract: Equipment for ultrasonic testing structural materials includes transducers and test electronics normally operated in sequential test cycles each cycle including the generation of a test pulse to be sent into the test object and subsequently, upon interaction with the test object, return signals (echos) are received and processed, e.g. as to transit time, amplitude, contour, etc. Self-checking is carried out in three phases. One phase uses simulated receiver signals for operatively disconnected transducers, to be processed by the electronics as if they were echos; a second phase uses simulated transducer inputs and analogous processing and a third phase uses a reference body as test body simulation for conduction of "tests". The results of signal processing are compared with reference signals and correlation of deviations and absence of deviations is used to isolate malfunctions.

Ultrasonic tube inspection

Abstract: A method and apparatus for graphically displaying the measurements obtained with an ultrasonic inspection instrument of the pulse-echo type. The instrument is designed to inspect tubular members for primarily internal corrosion and display the results on the face of a cathode ray tube.

Method for damping an ultrasonic transducer

Abstract: In an ultrasonic wave generator or receiver using an ultrasonic wave transducer, a negative immittance converter is inserted in a circuit of the generator or receiver in order to cancel components which impede the damping characteristics of the ultrasonic transducer.

Hydrodynamic ultrasonic probe

Abstract: An improved probe for in-service ultrasonic inspection of long lengths of a workpiece, such as small diameter tubing from the interior The improved probe utilizes a conventional transducer or transducers configured to inspect the tubing for flaws and/or wall thickness variations The probe utilizes a hydraulic technique, in place of the conventional mechanical guides or bushings, which allows the probe to move rectilinearly or rotationally while preventing cocking thereof in the tube and provides damping vibration of the probe The probe thus has lower friction and higher inspection speed than presently known probes

Automatic ultrasonic test equipment for cylindrical prods. - has transducer arrays concentric to test piece for continuous testing and fault detection

Abstract: The test piece (4) is passed in the axial direction through an ultrasonic field generated by the transducers (2, 3) arranged around its periphery in two parallel rings (6, 7). The test piece is not rotated. The transducers are adjustable both circumferentially and axially. Time multiplexing reduces acoustic interference. Performance may be further improved by the choice of sequence by which individual transducers are transmitters and receivers. Longitudinal, transverse and oblique faults may be detected in objects of circular cross section, e.g. tubes, rods at e.g. 300 metres per minute, using impulse reflection techniques.

Ultrasonic testing of austenitic stainless steel welds False indications and the cause of their occurence

Abstract: A study has been made into the causes of the false indications sometimes observed upon ultrasonic inspection of austenitic stainless steel welds. The path taken by transverse ultrasonic waves through an austenitic stainless steel specimen embodying a butt-weld was traced by repeatedly shaving the surface of the specimen and scanning at each stage the newly uncovered surface with a dynamic sensor to obtain a C-scan of the through-transmission pattern of the beam penetrating through the surface. This showed that the false indications are back reflections, from the metal surface, of waves that have propagated along dendritic crystal formations developed in the weld metal. The present work provides evidence that certain indications obtained on austenitic stainless steel welds are in fact spurious, and should not be ascribed to defects in the weld.

Nondestructive testing for heritage structures

Abstract: A general discussion of application of some examination techniques to historic materials and structures, including radiography, termography, ultrasonic testing, load tests, magnetometry. Inspection of wood and metal. Deficiencies of building envelope. Detection of hidden architectural details. Testing of floor. Detection of voids in masonry.

Ultrasonic testing system

Abstract: An ultrasonic system for detection of defects is provided including a pulse-echo instrument having a cathode ray tube on which an A-scan visual indication of flaws is produced and including a doppler circuit arranged to produce a doppler signal in an audible range in response to movement of a transducer relative to defects in a pipe seam or other region being investigated. The doppler signal is applied to earphones, permitting the existence of defects to be reliably determined audibly, after which the defects may be more carefully studied through the visual indications on the cathode ray tube. The doppler signal is also recorded on one track of a magnetic tape with operator's comments being recorded on a second track of the same tape. The doppler circuit includes an oscillator operated during a gating time interval to generate a reference signal, a phase detector responsive to a reference signal and to echo ignals, and a sample and hold circuit for storing the output of the phase detector from one cycle to the next.

Method and device for ultrasonic inspection of materials

Abstract: A method for ultrasonic inspection of materials in which a reception and processing of ultrasonic vibrations reflected from a material being inspected is followed by separating signals from noise at a level that for each period of radiating ultrasonic vibrations is automatically set to be equal to the mean noise power per interval of time selected within the maximum sensitivity zone of a preceding period of radiating ultrasonic vibrations.

Computer controlled ultrasonic defect gate

Abstract: An ultrasonic inspection system including a defect gate which can be interfaced with a digital computer. A high frequency precision oscillator and two preset counters define the start and duration of a gate period or window corresponding to an inspection depth range within the test specimen. The magnitudes and locations of the two or more largest defect indications within a gate window are determined and made available to the computer for analysis and diagnosis. A rear interface gate window is provided and a determination is made as to the presence or absence within the rear interface gate window of a signal representing the rear interface of the specimen. The distance between the interrogating transducer and the test specimen front interface is also determined at each point. Means are provided for real time control of the inspection system parameters by the computer to allow adaptive control of the inspection process based on real time diagnosis of the test data.

Ultrasonic testing of welds in wheels

Abstract: Methods and means for testing and storing data relating to the quality of resistance spot welds in an automotive wheel are provided. The wheel may be rotated for one revolution or less, dependent upon the number of transducers used, while a counter generates pulse signals representative of the locations of the wheel as it is revolved. Ultrasonic signals are transmitted towards and received from locations in the wheel at which the presence of welds is being tested. Storage devices, responsive to signals from the counter and the received ultrasonic signals store counts representative of the locations on the wheel where acceptable welds start and end to thereby determine the diameters of the welds. The data stored also indicate locations and durations of voids in the welded areas.

Development of Ultrasonic Techniques for Remote Monitoring of Erosive Wear in Coal-Conversion Systems

Abstract: Erosive wear of metallic t ransfer lines and fittings in coal-conversion plants is produced by particulate matter in the two-phase flow. Ultrasonic erosive-wear monitoring systems incorporating convectively cooled waveguides have been developed and installed on elevated-temperature, high-pressure components for real-time on-line data a cquisition. Problems of hightemperature coupling of acoustic waveguides to transfer lines, reliability of acoustic coupling of transducers to waveguides for long periods under varying conditions out of doors, and factors affecting remote high-frequency measurements have been examined. Waveguides of Type 304 stainless steel and low carbon steel have been tested f or reliability and ease of field installation.

Film strip positioning for x-ray testing of pipes

Abstract: An apparatus for X-ray testing of pipes following ultrasonic testing includes a reversible roller track for telescoping a pipe upon a cantilever arm which can be moved up and down on a stand and carrying an endless belt with resilient U-shaped holders for supporting film strips to be moved into the pipe and adjacent to suspected defects. Reversal of the belt drive permits removal of the exposed film strips as the pipe is moved out.

Ultrasonic testing at high temperatures

Abstract: Hot products such as steel create particular problems in inspection by ultrasonics. These have been largely overcome by a noncontact method known as electromagnetic acoustics, now in industrial use

Method for ultrasonic inspection of materials and device for effecting same

Abstract: According to the proposed method for ultrasonic inspection of materials, aeception and processing of ultrasonic vibrations reflected from a material being tested are followed by separating signals from noise at a preset level, which is carried out by means of time selection of signals performed within time intervals during which the signals' amplitudes exceed the preset level. In the device for effecting the method of this invention, an output of an ultrasonic generator, whose input is connected to one of the outputs of a synchronizer, is connected to an input of an ultrasonic converter acoustically coupled to the material being tested. An output of the ultrasonic converter is connected to an input of a reflected ultrasonic vibrations preprocessing unit whose output is electrically coupled to one of inputs of a signals recording unit. The coupling is effected either via a high-frequency amplifier, a no-noise-cutoff detector and a unit for separating signals from noise at a preset level, which are placed in series, or via the unit for separating signals from noise at a preset level, the high-frequency amplifier and the no-noise-cutoff detector placed in series. The unit for separating signals from noise at a preset level contains a gate pulse forming circuit and an AND circuit whose first input is electrically coupled to an input of the gate pulse forming circuit, the latter's output being connected to a second input of the AND circuit.

Ultrasonic characterization of austenitic welds

Abstract: Nondestructive evaluation of austenitic stainles steel weld metal is a very difficult problem. Mechanical anisotropy appears to be a major contribution and is caused by preferred local orientation of elongated subgrains and preferred crystallographic orientation. The result of this anisotropy is the directional dependence of the ultrasonic velocities (shear and longitudinal) and ultrasonic attenuation. The directional dependence of these ultrasonic parameters causes large errors in locating and sizing flaws in welds. Initial studies were carried out in a type 308 stainless steel electroslag weld to characterize this anisotropy. The apparent symmetry in the macrostructure of the electroslag weld leads us to expect orthotropic symmetry in elastic constants. A technique was developed to measure variations in velocity and attenuation with direction. The velocity data compared favorably to theoretical calculations using this orthotropic model. From the velocity data all elastic constants and engineering constants for this weld were determined. Studies of other types of welds showed that orthotropic symmetry is typical of austenitic welds. Data will be presented to show how anisotropy affects defect location and sizing in welds.

Pulser for ultrasonic inspection system

Abstract: A pulser circuit for providing electrical exciting pulses to a transducer in an ultrasonic testing apparatus in which a transducer transmits ultrasonic energy corresponding to the pulses into a test specimen. The pulser circuit includes a capacitor connected in series with a source of charging potential and a load impedance. A pair of switching transistors are connected in parallel and to the capacitor and the charging potential. A second switching transistor is connected directly across the capacitor. The first switching transistors turn on and cause the charged capacitor to develop the leading edge of a pulse across the load impedance. The leading edge turns on the second switching transistor which provides a direct discharge path for the capacitor and thereby shapes the pulse. Diode means is connected across the load impedance to assist in rapid recharging of the capacitor. The diode means is forward biased to provide a clamped reference potential for the pulse.

An evaluation of ultrasonic probes by the photoelastic visualisation method

Abstract: An assessment of ultrasonic probe performance is described in which ultrasonic waves have been visualised by the photoelastic method. A qualitative examination of selected compressional, shear and Rayleigh wave probes has been produced. Ultrasonic wave generation and wave interactions with artificial and "natural" defects in glass testpieces are displayed. In addition the practicability of quantifying ultrasonic wave stresses has been demonstrated. Based on this examination the optimization of probe design in particular cases has become possible. Solutions to ultrasonic inspection problems within the railway industry are reviewed in which specially designed ultrasonic probes are employed. In particular the examination of axles and rails are discussed in which a variation in probe design was necessary due to features of defect orientation.