Abstract: A zero crossing detector including timing and logic circuitry for ascertaining and eliminating undesirable waveform characteristics. If a zero crossing indication occurs within a set time period after a trigger event due to a phase inversion or noise, then the indication is ignored. Conversely, if a zero crossing does not occur within a second set time period due to a phase reversal, an artificial crossing will be indicated. By establishing these bounds, the system will function within a specified frequency band.

Abstract: An apparatus and method for measuring particle agglomeration or dispersion in fluid mixtures, such as polymer melts, resides in a piezoelectric transducer, a spherical fused quartz lens, and a fluid housing. A repetitive, broadband, ultrasonic wave is produced by the transducer and is sent into the lens, which also serves to isolate the transducer from the mixture. The ultrasonic wave meets a spherical dimple at the end of the lens which focuses a portion of it into a diffraction limited spot or "interrogation zone". Since the intensity of the wave is large in the interrogation zone, small changes in the impedance of the fluid in this zone, caused by passing agglomerates, will cause large fluctuations in the intensity of the back scattered wave, which is monitored by the transducer between pulses and displayed by associated electronic elements.

Abstract: Traversing energy flux transmitted into a fiber/matrix composite structure is propagated through the structure in directions which vary depending upon the elastic stiffness condition of the composite. Degradation in elastic stiffness of the composite, from any cause, will result in variations in the direction of travel of the flux through the composite. By determining the direction of flux propagation in the composite, or the portion of the composite structure from which the flux is detected as it exits the structure, the condition of the composite structure, independent of the source of degradation, can be determined.

Abstract: Methods and apparatus are disclosed for monitoring and controlling potential residual stress relief mechanisms in composite epoxy resin materials. Passive and injected, or active, acoustic signals originating in or propagated through a specimen material during the formation process produce signatures identifiable with known residual stress relief mechanisms. Real-time control of material temperature and external pressure during formation in response to acoustic signals measured or observed in relation to desired acoustic signature minimizes formation of undesired material properties.

Abstract: An ultrasonic defect monitor for a moving workpiece is disclosed, including first and second test probes on opposite sides of an area of interest. The detected signals are processed for display by both a threshold monitor circuit, and an integrator-threshold-monitor circuit each connected to an output indicating unit for providing defect indications.

Abstract: A welded steel pipe being turned is subjected to a static magnetic field formed by a sensor. The sensor includes an electromagnet and a transmission and reception coil attached to the end surface of the electromagnet pole facing the steel pipe. The electromagnet is energized by a dc power supply and the transmission coil is supplied a pulse current at certain intervals. As the transmission coil is energized by the pulse current, transverse ultrasonic waves are generated in the steel pipe. The transverse ultrasonic wave propagates through the pipe in the thickness direction thereof and is reflected by the inner surface of the pipe and reaches the outer surface where it is detected by the reception coil. The signal received by the reception coil is amplified by an amplifier and fed to a signal processor which then locates the position of the weld according to the amplitude of the received signals.

Abstract: The present method relates to the measurement of fibrous material, such as slivers and rovings, by ultrasonics. By a suitable arrangement of a sound source and a sound pick-up with the fibrous material disposed therebetween, only those sound waves arrive at the sound pick-up which have penetrated the fibrous material. All lagging disturbing signals which are generated by reflections and interferences are suppressed by the pulsed operation of the sound source and by the corresponding gating of the sound pick-up, as a result of which, the value to be measured, namely, the quantity of fibers present at any time in the measuring data, is substantially free from disturbing influences. This measured value may be used as a value for the cross-sectional regularity, or as a controlled variable for the production of regular rovings or slivers.

Abstract: An instrument for determining the concentration of solid particles dispersed in a liquid medium, (e.g. coal in oil), comprises (a) an ultrasonic pulser, (b) an ultrasonic receiver, (c) a gated peak detector, (d) signal conditioning and display circuits and (e) an ultrasonic transducer assembly including a layer of known impedance to receive the dispersion. The pulser produces an impulse which is converted by the transducer to an ultrasonic wave, which passes through and is reflected back by the interface between the layer and the dispersion to the ultrasonic receiver and passed to the gated peak detector which measures the peak amplitude of the echo from the layer/dispersion interface. The peak amplitude is then converted by the signal conditioning and display circuits to produce a display of the amplitude and/or the solids content of the dispersion.

Abstract: The attenuation of RF pulses passing through a mineral slurry is determined by measuring the amplitude of the envelope produced by a series of successively occurring attenuated electrical pulses. The pulses are applied to the input of a variable gain amplifier, the gain of which is under control of a digital processor. The peak amplitude of each pulse is compared with a fixed reference voltage. The contents of a storage register associated with the processor is modified dependent upon whether the pulse amplitude is geater or less than the reference voltage. The contents of the register is used to control the gain of the variable gain amplifier in such a way that the amplitude of the next successive pulse will approach the value of the reference voltage. After the last pulse has been measured, the gain of the amplifier is inversely proportional to the amplitude of the pulse envelope, and the contents of the successive approximation register will also be proportional to the amplitude of the pulse envelope.

Abstract: Ultrasonic wave attenuation is determined for a plurality of limited volumes of tissue comprising a body under examination by directing ultrasonic waves through each limited volume along a plurality of vectors, determining a measure of attenuation of the limited volume by detecting the frequency shift of reflections of the ultrasonic wave along each vector, and averaging the attenuation of each limited volume from each vector intersecting the limited volume.

Abstract: The ultrasonic wave attenuation of tissue undergoing examination is determined by directing a plurality of ultrasonic signals into the tissue, receiving and detecting a measure (e.g. zero crossings) of the frequencies of ultrasonic signals reflected from various depths in said tissue, and averaging the measures of the frequencies for each of the various depths. Attenuation of the tissue between a first depth and a second depth is determined from a comparison of the averaged measure at the first depth and the averaged measure at the second depth.

Abstract: Time gain control of a variable gain amplifier in an ultrasonic scanning system is defined from ultrasonic attenuation of tissue under examination. An ultrasonic signal is directed into the tissue and a reflected signal is detected. The frequency of the reflected signal is measured, and frequency dependent scatter perturbations are identified and eliminated from the measured frequency. Tissue attenuation is then established from the measured frequency after perturbations are eliminated.

Abstract: A system for the detection of wing icing by monitoring variations in flexural waves transmitted through the outer plate material of an aircraft airfoil. The flexural waves in the plate of the wing airfoil are more subject to variation from the accumulation of ice on the wing than the compressional waves. The flexural waves are detected apart from the compressional waves, which tend to remain relatively constant, to provide an indication of icing. Changes in amplitude, phase or dispersion characteristics of the flexural waves are detected to indicate ice buildup, and, in one embodiment, these values are ratioed to the corresponding levels in the compressional wave in order to provide compensation for variations other than ice buildup. The ultrasonic waves may be coupled directly from a transducer to the airfoil plate or via an ultrasonic waveguide interposed between the transducer and the plate.

Abstract: A method for measuring the physical characteristics of an object through the use of an ultrasonic wave, which comprises the steps of transmitting an ultrasonic pulse to the object, receiving a reflected wave from the object, analyzing the spectrum of a parameter representing the strength of the reflected wave and obtaining a center frequency of the spectrum to measure the physical characteristics of the object. The center frequency is used as a function of distance or time to obtain its differential or difference coefficient, or a computation similar to that for an X-ray computer tomography is carried out, thereby to obtaining an attenuation slope and other data to be used as the physical characteristics of the object.

Abstract: A time gain control (TGC) signal for a variable gain amplifier in an ultrasonic scanner is derived by determining the attenuation at many levels in the object under examination and then constructing the TGC signal based on the cumulative attenuation of an ultrasonic signal through the object. A zero crossing detector such as a Schmitt triggered monostable multivibrator receives a reflected ultrasonic wave signal and generates pulses which are counted during time intervals corresponding to a depth level in the object. By comparing the zero crossing density at one level to the zero crossing density at another level a measure of attenuation between the two levels is obtained.

Abstract: This ultrasonic imaging apparatus has an array (44, 52 or 100) of transducer elements (44, 50 or 104) for transmitting ultrasonic signals having a first predetermined center frequency (fc1) into an object (12) to be analyzed through use of the transmitted signals reflected from within the object. A means (150, 116-1 through 116-X and 120-1 through 120-X) is connected to transmit the ultrasonic signals from the array (44, 52 or 104) in a stepped array mode. A means (150, 116-1 through 116-X and 120-1 through 120-X) is connected to transmit the ultrasonic signals from the array (44, 52 or 104) in an angle scanning mode. There is a means (150, 128-1 through 128-X) for focusing the transmitted signals at a desired depth within the object (12). The reflected signals sensed by the apparatus have a second center frequency (fc2) less than the first center frequency (fc1) as a result of signal attenuation by the object (12).

Abstract: An ultrasonic imaging apparatus has an array (10 or 100) of transducer elements (14 or 104) for transmitting ultrasonic signals into an object (12) to be analyzed through use of the transmitted signals reflected from the object and sensed by the apparatus. The transmitted signals have a first predetermined center frequency. The reflected signals sensed by the apparatus have a second center frequency less than the first center frequency as a result of signal attenuation by the object. A means (70, 62 or 150, 152-1 through 152-X) is connected to select a number of transducers (14 or 104) in the array (10 or 100) for transmitting and/or receiving the ultrasonic signals based on the second center frequency. Adjusting the number of transmitting and/or receiving transducers (14 or 104) with changes in frequency produced by signal attenuation gives improved image resolution under a wider variety of use conditions than with prior art ultrasonic imaging apparatus.

Abstract: Ultrasonic wave attenuation in an object is determined from the number of zero crossings of a reflected signal as a function of depth. The zero crossing density is indicative of the frequency spectrum, and by comparing the zero crossing density at one level to the zero crossing density at a second level a measure of attenuation therebetween is obtained. Apparatus for implementing the method comprises a zero crossing detector such as a Schmitt triggered monostable multivibrator and a pulse counter.

Abstract: The apparatus provides for detection of variation in acoustic properties at a metal to air interface (18) such as may be caused by arrival of drops of leaking liquid. Ultrasonic signal pulses from transducer (14) are reflected many times back and forth across rod (11) between the transducer and the interface (18). Change in diminution of amplitude with successive reflection can be detected over a multiplicity (e.g. 10) of reflections and indicates change in the acoustic properties of the interface. Comparison is made between a selected early reflected signal pulse and a selected later reflection. Response is inhibited in respect of intermediate reflections.

Abstract: A measurement method and system for measuring characteristics of attenuation of domains in an object comprises transmitting ultrasonic waves into the object and receiving ultrasonic waves reflected from the object. The measured characteristics of attenuation of reflected waves is determined using signal intensities. A plurality of ultrasonic waves having different frequencies are transmitted either simultaneously or alternately to an object, and the reflected waves are received from the object. The signal intensities corresponding to the transmission frequencies among the reflected waves are stored and the signal intensity ratio is calculated. The signal intensity ratio indicates the attenuation characteristic. The attenuation coefficient can also be obtained using a time interval from the transmission time to the time of the reflected wave is received. The attenuation slope can be obtained from this attenuation coefficient and the frequency difference between transmitted ultrasonic waves.

Abstract: A method for detecting brazing defects in a plate-fin type heat exchanger with a brazed core structure having a number of wavy fin members alternately with a number of parallelly spaced plate members, in which a pulsed sound in the frequency range of several tens KHz to several hundreds KHz is transmitted across the fin and plate members from a pulser located on one outermost plate member to a sensor located on the other outermost plate member, detecting the positions and sizes of brazing defects two-dimensionally on a plane on the basis of the level of sound received by the sensor. Three-dimensional detection of the position of the defect is also possible by combining therewith a radiographic inspection using a radiant ray source which is located on one lateral side of the core structure to irradiate a radiant ray in a direction substantially parallel with the plate members of the core structure.

Abstract: The average particle size for particles distributed in a slurry is determined by transmitting at least one beam of ultrasonic rays of a certain frequency into the slurry, detecting, by separate detector means, on one hand ultrasonic radiation that passes through the slurry and, on the other hand, ultrasonic radiation scattered in the slurry, said detector means forming first and second signals corresponding to the intensities of the passed-through and the scattered radiation respectively, determining the scattering attenuation factor on the basis of said first and second signals and the total attenuation factor by using the intensity of passed-through radiation obtained with pure water, and determining the particle size with the help of the scattering attenuation factor, whereby the radio of said factor and the total attenuation factor is formed in order to eliminate influence of the slurry density.

Abstract: A frost sensor for detecting the presence of frost uses an acoustic device having an acoustic transmitting medium made of a magnetostrictive material, particularly an amorphous metal alloy, of a ribbon shape, as means for detecting the frost.

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.

Abstract: Method and apparatus for measuring an attenuation characteristic in a region of interest using ultrasound wherein two statistically independent set of values are accumulated as a difference between logarithms of pairs of each signal set, and the attenuation characteristic calculated as a central tendency parameter of each set of values.

Abstract: A method of detecting and identifying particulates in the recirculating fluid flow for an oil recovery system by counting the number of ultrasonic pulses reflected from the particulates and comparing the number counted with the amount of attenuation of ultrasonic energy across the flow.

Abstract: An apparatus and method for quantitative nondestructive testing (NDT) of a wire wherein noncontacting ultrasonics is used. A transmitter-transducer coil is held in close proximity of a test wire or tube and high amplitude electrical current pulses are passed in the coil. A magnetic field perpendicular to the longitudinal axis of the wire is applied in the region. As a result of the electrical current pulses in the transducer coil, eddy currents are produced on the surface of the test wire. As a result of the magnetic field applied in the region, these eddy currents lead to Lorentz forces in the wire, which in turn generate corresponding torsional waves in the test wire. These waves speed down the wire and are received by a reciprocal transduction process, by means of a receiver-transducer. The velocity and attenuation measurements of the torsional waves along the axis of the test wire are made precisely and accurately via multiple-transducer setups.

Abstract: A piezoelectric sensor consists of material for transmitting elastic waves and has a surface subjected to the condensation and presence of dew and liquid to be detected. A wave producing device includes a transmitter for producing an acoustic surface wave on the surface in conjunction with piezoelectric phenomena of the sensor. A detector includes a receiver for receiving the wave after transmission thereof across the surface. The wave is variably attenuated in transmission between the transmitter and receiver in accordance with dew or liquid on the surface. A measuring device measures the attenuation of the detected wave and thereby indicates the dew point or presence of liquid on the surface.

Abstract: The invention relates to a device for acoustically controlling the setting and hardening characteristics of a material such as cement. This device comprises a cell body defining a cylindrical body, or measuring chamber, which contains a receptacle adapted to receive the material to be tested. The measuring chamber is extended by its two ends by two cylindrical passages coaxial to said chamber, which comprise each a threaded portion and are associated to sealing means; said cell body further includes two electro-acoustic transducers which are arranged at mutually opposed locations and are facing each other. The novel device is adapted to be used for determining and controlling the setting, hardening and mechanical strength characteristics of cement or similar material under conditions of high pressure and elevated temperatures.

Abstract: Disclosed is a method for determining the dispersion of a surface acoustic wave in an object, including the steps of generating a broadband acoustic wave in a surface of the object, detecting the wave at first location on the surface, and detecting the wave at a second location on the surface. Fourier transforms of the first and second detected waves are calculated, then the change in phase .DELTA..phi.(f) of the frequency component f of the detected wave, between the first and second locations, is computed from the phase components of the quotient of the two transforms. The dispersion of the wave in the surface is given by the formulav(f)=(2.pi.f .DELTA.l/.DELTA..phi.(f))In a pulse-echo version of the method, the wave is generated and detected at the first location, and generated and detected at the second location, the dispersion then being according to the formulav(f)=4.pi.f .DELTA.l/.DELTA..phi.(f)).

Abstract: Sheet or plate stock is used as to defects by a row of ultrasonic transmitting transducers on one side and receiving transducers on the other. The transmitting transducers receive frequency-modulated signals via individual buffers, and the receiving transducers feed individual, digital amplitude envelope minima to detection circuits whose outputs are fed to a computer which also feeds operating parameters to the source for the modulated signals. Different types (autonomy) of the receiver channels are described as well as diagnostic and setup procedures.

Abstract: A method of testing new fuel rods for assemblies for nuclear reactors.Ultrasonic waves are transmitted in the canning tube of the fuel element disposed in the open, with an oblique incidence with respect to the axis of the tube, from one region of the side wall of the tube. By reflection at the walls of the canning tube, these waves produce plate waves or Lamb waves. These Lamb waves are picked up after a certain distance has been covered along the length of the canning tube and the attenuation undergone by these Lamb waves is measured. From this, by comparison with the attenuation results obtained at another part of the length of the tube or with a standard tube, data on the possible presence of moisture in the fuel rod is deduced. The invention particularly applies to the testing of fuel rods of assemblies for a pressurized water nuclear reactor.

Abstract: An ultrasonic probe for propagating an ultrasonic surface wave which is constrained along the probe with the evanescent pressure field penetrating the subject in a direction orthogonal to the axis of the probe. The ultrasonic probe may then be placed about a plurality of orientations, passing the evanescent pressure field through the subject along the plurality of orientations and detecting the loss of energy in each successive pressure field propagation. A data processing system for processing and correlating each successive detected energy loss in each propagation direction can produce a resultant computed tomographic image of a defined plane through the subject.

Abstract: An arrangement for deleting liquid in a line, using non-intrusive ultrasonic techniques is disclosed. In this arrangement, four piezoelectric crystals are arranged in pairs about a 0.072 inch o.d. pipe. An ultrasonic tone burst is transmitted along the pipe, between crystal pairs, and the amplitude of the received tone burst indicates the absence/presence of liquid in the pipe.

Abstract: A detecting transmitter device installed in operative proximity with a surface to be observed includes an ultrasonic waveguide installed in such surface. Electronic equipment electrically connected to the ultrasonic waveguide transmits ultrasonic waves to the waveguide. The ultrasonic waves proceed in the waveguide. The equipment also receives the ultrasonic waves from the waveguide. The degree of attenuation of the waves in the waveguide depend upon the difference in viscosity and other mechanical properties of water and ice, whereby the detecting transmitter device and the electronic equipment detect freezing of the surface by attenuation of the waves in the waveguide.

Abstract: An ultrasonic flaw detection system automatically measures attenuation of an input signal from a receiver transducer that provides a reference level. Successive amplifier stages having stepped gains provide graduated output levels that are detected and stored by individual peak readers. Sampled output levels are compared in comparators and with a reference voltage generated by a digital-to-analog converter to produce a binary output corresponding to each signal as a first coarse attenuation level. Logic control and timing circuitry selects the output level corresponding to one of the signals having a peak voltage in a predetermined range. A logarithmic converter and comparator provide a fine attenuation reading which is summed with the coarse reading in digital form. This is decoded and displayed as a total attenuation readout.

Abstract: Method of and apparatus for the continuous measurement of changes in rheological properties of monomers during polymerization. Longitudinal ultrasonic oscillations are introduced into the polymerizing system, and oscillations received after passage through a part of the polymerization system are monitored as the polymerization process proceeds. The ultrasonic oscillations have a frequency of 0.02 to 100 MHz. The monitoring may be of the absorption of the oscillations and/or the rate of propagation of the oscillations.

Abstract: The invention is in the monitoring of physical parameters relating to various fluids and polymers by contacting same with the surface of a piezoelectric material unit through which is passing a surface acoustic wave, and measuring the alteration of that wave as an indication of these parameters. The invention is also in apparati for monitoring certain of said parameters.

Abstract: A method of discriminating solid golf balls from thread-wound golf balls which includes the steps of holding the golf ball to be discriminated between a transmitter coupled to an ultrasonic wave oscillator and a receiver coupled to an ultrasonic detector for detecting the ultrasonic wave received by the receiver, applying from the transmitter, the ultrasonic wave having a frequency which can propagate through the solid golf ball, but can not propagate therethrough, to the golf ball to be discriminated, and detecting presence of the ultrasonic wave reaching the receiver through the golf ball to be discriminated by the ultrasonic wave detector.

Abstract: Techniques for a broad band high frequency acoustic investigation of a subsurface formation around a borehole are described utilizing a range of acoustic frequencies selected to produce detectable acoustic backscatter from grains within the subsurface formation. The acoustic backscatter is detected and a spectrum thereof is produced and averaged over adjacent subsurface formation regions. A subsurface formation parameter such as the frequency dependency of the attenuation of the backscatter is determined from an analysis of the spectrum to provide an indication of the granularity property of the subsurface formation. Use of a broad range of frequencies enables a determination of the subsurface formation parameter over a large range of grain sizes. In another technique the spectrum of the detected backscatter is modified to remove the effect of the frequency response of the system with which the investigation is made.

Abstract: Disclosed is a method for evaluating a discontinuity in an object. As used to measure the depth of a surface discontinuity in a plate type of object, the method includes the steps of generating a horizontally polarized shear wave in the object directed substantially along the axis of the discontinuity, passing the generated wave through an aperture to diffract the wave prior to its arrival at the discontinuity, detecting the wave after it has propagated through the discontinuity, and calculating the depth of the discontinuity by correlating the phase and amplitude of the detected wave to the phase and amplitude of a similar wave propagated in a region of the object which is free of discontinuities.

Abstract: Device enabling the direct measurement of the overall insulation level of an acoustic insulation medium with respect to a reference excitation noise signal when said medium is subject to an actual excitation noise signal deviating from the reference excitation noise signal. The device comprises two microphones receiving a first and a second alternating signal respectively representing the noise signal actually transmitted through the medium and the actual excitation noise signal and a read only memory storing spectral components of the reference excitation noise signal in a plurality of given spectral bands. The first and the second alternating signals are decomposed into alternating spectral components in these spectral bands and the alternating spectral components of the second signal are rectified in order to obtain rectified spectral components.

Abstract: A method and apparatus is provided for determining the attenuation coefficients within a body of material by transmitting sonic pressure pulses into the material, analyzing the spectrum amplitude of the echoes returning from the boundaries within the material, calculating the attenuation coefficients of the material between the boundaries and comparing the measured coefficients to those of normal and abnormal tissue. The wave shape of the transmitted pulses is adjusted so that the pulses generate echoes with uniform spectrum amplitude (white echoes) from each boundary within the material. Given the characteristics of the pulses which generate white echoes from the boundaries of each tissue segment and given the thickness of the material between each pair of boundaries, the attenuation coefficients of the material are calculated. The attenuation coefficients are displayed in any manner desired, including traditional B- and M-mode displays.

Abstract: A hollow, projectile-shaped body containing an acoustical transducer is rased into the sea such that the body descends in free fall until it strikes and penetrates the sea floor, coming to a rest therein. Acoustic signals emanating from the acoustic transducer are processed to generate a direct current analog signal which is a function of the acoustical attenuation of the acoustic signals from a time immediately preceding the body striking the sea floor surface until the body comes to rest in the sea floor, thereby obtaining an indication of the physical characteristics of the sea floor.

Abstract: A method of displaying information obtained by pulse-echo ultrasonic examination of an object, particularly in medical diagnostic examination, comprises forming a first display representing the positions of acoustic impedance discontinuities within the object and simultaneously incorporating in the display other parameters relating to the object.

Abstract: Apparatus for measuring distance between a gauge head orifice, and the front planar surface of an object by sensing acoustic pressure near the gauge head orifice. The acoustic pressure is initially generated by an audio oscillator activating a speaker which emits acoustic waves through a first orifice. Acoustic pressure is sensed through a second orifice, proximate to the first, and the pressure is converted to an electrical signal which is processed to yield a distance signal for a display. Two similar distance gauges spaced apart on opposite sides of a planar member at a known distance are used to compute the thickness of the planar member.

Abstract: The presence or absence of liquid at a particular location of a tank or pipe is sensed through the wall of the container by a single ultrasonic transducer which may be secured to the outer surface of the container by hand pressure, by clamping, or by cementing. Detection is obtained through the damping effect of either liquid or air within the container on multiple interface reflections of a longitudinal sonic beam in the container wall. The first return signal amplitude adjusts the gain of the monitoring circuit and allows the measurement of the percentage decay of the return signal and the comparison of the decay to the known decay rate if the container was either empty or full at the point of measurement. Output circuits are provided to give a full or empty output signal, or to provide output control signals in response to the fluid level measurement. A fault alarm signal is also produced to indicate that the transducer is not properly coupled to the container or that the circuit is working improperly.

Abstract: A circuit means including a power source, a cathode ray tube, a source of high frequency sound, a transducer means for emitting and receiving sound signals, and mode control means for varying the visible output of energy across said cathode ray tube for making various anatomical measurements by emitting high frequency sound into an anatomy through said transducer, whereby the amplitude and frequency of reflected signals received by said transducer will be visibly reflected on said cathode ray tube.

Abstract: Disclosure is made of a method for checking the thickness of sheet materials, whereby acoustic oscillation is sent in the form of a traveling wave through a material being checked roughly perpendicularly to its surface. The amplitude of the acoustic oscillations that have passed through the material being checked is measured and compared to that of a reference signal, whereby the thickness of the sheet material is determined. The proposed device for checking the thickness of sheet materials comprises an acoustical radiator and an acoustical receiver. The working surface of the radiator and receiver are roughly parallel to the surface of a material being checked, which material is placed between the radiator and receiver. The distance between the radiator and receiver is selected to be in excess of the spatial extension of the traveling wave during each measurement period.

Abstract: A method of non-destructively testing materials comprises directing an incident beam of ultrasonic waves onto the surface of a material and detecting the beam reflected by the surface, the angle of incidence and the wavelength of the ultrasonic waves being detected, and the critical angle of incidence at which the energy of the reflected beam passes through a minimum being determined for at least two different wavelengths. A curve is then prepared showing how the critical angle or a quantity dependent thereon varies with the wavelength or a quantity dependent thereon. Apparatus for carrying out the method comprises a goniometer for transmitting the incident ultrasonic beam and detecting the reflected beam, means for varying the angle of incidence of the beam, means for varying the wavelength of the waves, and means for determining the critical angles of incidence. The invention is applicable inter alia to the testing of tempered steel components.