Abstract: An apparatus for measuring acoustic emission is activated only at critical periods which are determined by detection of the background noise from a reference level. An acoustic emission transducer continuously transmits a signal to a detection circuit which delivers the top modulation envelope of the background noise to a comparator at a reference level delivered by a control unit.When a mean level of the background noise does not exceed a threshold reference level the AE is sampled at a low rate, f. When the background noise exceeds the threshold reference level the data sampling unit is activated to sample AE at a much higher rate F. Therefore AE is sampled at a high rate only when the pump or other machine under test is running and at a low rate when the article under test is not operating. The AE testing device also includes a frequency spectrum correlator which allows background noise to activate the increased sampling rate only if the noise is in a given frequency range.

Abstract: A multipurpose in situ underground measurement system comprising a plurality of long electrical resistance elements in the form of rigid reinforcing bars, each having an open loop "hairpin" configuration of shorter length than the other resistance elements. The resistance elements are arranged in pairs in a unitized structure, and grouted in place in the underground volume. The electrical resistance of each element and the difference in electrical resistance of the paired elements are obtained, which difference values may be used in analytical methods involving resistance as a function of temperature. A scanner sequentially connects the resistance-measuring apparatus to each individual pair of elements. A source of heating current is also selectively connectable for heating the elements to an initial predetermined temperature prior to electrical resistance measurements when used as an anemometer.

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 fatigue damage indicator includes a thin plate mounted between or integral with two members to which a stress is to be applied, the disposition of the two members being such that the thin plate is stressed in shear.Slots extending in the direction of the applied stress may be provided to ensure that cracks formed by fatigue stress propagate in a desired direction and the crack propagation is designed to ensure that a part of the plate becomes detached or is bent substantially away.

Abstract: A cryogenic impact testing method of Charpy's and falling weight types which can test a test piece without substantially exposing the test piece with the atmospheric air under the same test piece cooling space, temperature controlling space and impact testing space, and a cryogenic impact testing machine of Charpy's and falling weight types which can execute suitably the above method. Thus, the stable temperature of the test piece can be obtained at the time of testing with highly reliable measured result.

Abstract: This invention provides a rugged dip-type viscometer suitable for use in a rotogravure printing plant, for example. The capillary of the viscometer is joined to a slotted protective collar and gives high precision measurements with inks that contain air.

Abstract: Two ultrasonic wave beams of different frequencies are emitted into a body under consideration from different locations on a surface of the body and a scattered wave beam created at a scattering point in the body by the interaction between the two ultrasonic wave beams is received. The emitting locations of the ultrasonic wave beams and the receiving location of the scattered wave beam are caused to scan. Thus, the stress distribution in the body is measured on the basis of the received outputs resulting from the scanning.

Abstract: A method and apparatus for detecting degradation in wood by applying acoustic waves along the wood grain and measuring the bandwidths and frequencies or standing wave resonances induced in the wood as the frequency of the applied waves is varied. Good quality wood exhibits a substantially harmonic relationship between the frequencies at which resonances occur and the bandwidths of the resonances are relatively small.

Abstract: A water level indicating apparatus (10) has an optical system (22) for establishing an optical signal indicative of water level which signal is split by a beam splitter (18) to transmit the majority of the optical signal to a fiber optic cable (16) and to reflect a part of the signal to a proximately located (13) glass diffuser (14). The end 24 of the cable (16) is reflected in the beam splitter (18) to form a reflection (24') which varies in intensity as the end (24) of the cable (16) is moved with the brightest reflection (24') appearing when the lamp(26) of the optical system (22) is in line with the end (24) of the cable (16).

Abstract: In an exemplary embodiment, an ultrasonic array has an installation for dynamic focusing at least in the transmitting mode. It is the object of the disclosure to avoid excessively great time loss, and yet to permit dynamic focusing also in the transmitting mode. This object is achieved in that, in the case of a specifiable number of depth regions (with a respective fixed focusing in each depth region) preferably associated with each scanning line of the ultrasonic scanning, the transmitting/receiving cycle for each fixed focusing is progressively introduced in such a manner that, for every depth region of each such scanning line, transmission is effected at such a time-point which immediately follows, for example, that time interval in which echo information was received from the chronologically prior-scanned depth region for such scanning line.

Abstract: The present invention relates to a device for stressing a deformable material specimen. The apparatus consists of top plate 11 and bottom plate 12 sandwiching a guide cylinder 13. The specimen 14 is positioned on the bottom plate 12 and attached to a load piston 20 (FIG. 2). Force is applied through top plate 11 into guide cylinder 13. Once specimen 14 has been loaded, the stress is maintained by tightening tie bolt nuts 17.

Abstract: Driver bar assembly for vibration test apparatus, comprising a bar element and a retainer element separably connected thereto; the bar element having a normally vertically disposed base attachable to a pivotally mounted shaker head and a normally horizontally disposed flange adapted to lie in a common plane with and spaced from a slip plate to be driven by the shaker head; the retainer element having a first bracket in which the bar element flange is bracketable, and a second bracket in which the slip plate is bracketable opposite the bar element flange, whereby the flange and slip plate spacing is bridged in vibration transmitting relation between the shaker head and the slip plate; the retainer element being separable from the slip plate and the bar element flange without relative movement of the slip plate and shaker head, the bar element and shaker head being freely angularly movable relative to the slip plate in the separated condition of the retainer element and the bar element.

Abstract: An ultrasonic probe for inspecting the interface between the walls of a double-wall tube comprises a cylindrical body member having two cavities axially spaced apart thereon. The probe is placed in the tube and ultrasonic energy is transmitted from a transducer in its body member to a reflector in one of its cavities and thence into the inner wall of the tube. A second transducer in the probe body member communicates with the second cavity through a collimation passage in the body member, and the amount of ultrasonic energy reflected from the interface between the walls of the tube to a second reflector through the collimation passage to the second transducer depends upon the characteristics of said interface.

Abstract: A tracking generator 21 is slaved to a spectrum analyzer 23 to produce an input signal having a frequency that follows the frequency of the spectrum analyzer sweeping local oscillator 22. The input signal is gated to a transducer 26 by a transmitter gate 25 to produce ultrasonic waves in the sample 28. The resulting ultrasonic echoes are converted into electrical signals by the transducer and then gated into the spectrum analyzer by receiver gate 29. This arrangement produces spectra that are equivalent to shock-exciting the transducer with a true delta function shock-excitation.

Abstract: A system for measuring resonance frequencies in turbine and compressor vanes and propeller blades in which a vane or blade is excited at its base by a vibration generator and the phase of the excitation signal coming out of an acoustic transducer placed at the base is compared to that of the signal coming from a displacement transducer placed at the blade tip. The resulting phase error signal serves to pilot a variable-frequency oscillator which itself feeds the vibration generator, the frequency of which is noted by a frequency meter.

Abstract: A temperature sensor uses a thin film structure having an RF sputtered layer of a temperature sensitive material forming a thermistor element deposited on an electrically insulating and thermally insulating substrate. The sensor may include a plurality of deposited thermistor layers arranged on both sides of the substrate and having electrical connection means attached thereto. The sensor is arranged on a substrate suitable for inclusion in a detector cell forming a chamber arranged to be connected to a source of fluid flow.

Abstract: Method and apparatus are disclosed for measuring the thickness of a workpiece by periodically transmitting ultrasonic pulses into the workpiece, receiving ultrasonic echo pulses reflected from the bottom surface of the workpiece, measuring the period of time elapsed from the time of transmission of each ultrasonic pulse to the time of reception of its related echo pulse by counting the number of clock pulses within the time period, counting each of such measured time periods by clock pulses, and deriving from each of such counted time periods and number of clock pulses within the time periods values a signal representing the thickness of the workpiece, wherein the measurement of the elapsed time period is effected with respect to a plurality of successive echo pulses, during which the phase of the clock pulses is caused to be shifted by a predetermined amount of 2 .pi.

Abstract: Spherical bodies, such as bearing balls, are tested for machining irregularities or structural defects by subjecting them to supersonic vibrations from two or more ultrasound generators through the intermediary of a coupling liquid in which these bodies are immersed. One ultrasound generator has an axis in line with the body being tested while the other generator or generators have axes including acute angles with the radial directions of that body. The body is subjected to rotation in different planes by injecting the coupling liquid, alternately or simultaneously but at varying relative rates, through two different nozzles into an interspace separating the body from a spherically concave supporting surface.

Abstract: A water level indicating apparatus (10) has an optical system (22) for establishing an optical signal indicative of water level which signal is split by a beam splitter (18) to transmit the majority of the optical signal to a fibre optic cable (16) and to reflect a part of the signal to a proximately located (13) glass diffuser (14). The cable (16) extends to a matte screen (12) at a remote location (11) to thus provide a remote (11) optical signal as well as local (13) optical signal indication of the water level.

Abstract: A scanner includes a scan head having a linear array of transducers Xn, and a transmitter 106 which excites the transducers in response to transmit signals TRn from a reference generator 110 so that the transducers emit a plurality of successive bursts of ultrasonic energy, each burst producing a transmitted beam which is steered and focused along a radially-extending scan line. To effect received beam steering and focusing, received signals Sn from the transducers are supplied to a processor 112 along with associated in-phase binary reference signals bn(R) and quadrature binary reference signals bn(I). The received signal is multiplied by a reference signal and the product is integrated for a specific time duration whose time occurrence is used to steer and focus the beam.