Abstract: Apparatus is disclosed for determining the degree of stiffness of a sheet, for example a banknote, the stiffness being indicative of the condition of the banknote. The banknote (4) is drawn around a bobbin-shaped drum (1) by means of a pair of belts (2, 3) which grip a central portion of the banknote. The inner belt (2) drives or is driven by the central portion of the drum (1). The concave shape of the drum (1) imparts a curvature to the banknote in an axial plane, while the banknote is simultaneously curved in an orthogonal plane as it is wrapped around the drum. As the banknote passes around the drum it emits an audible noise which is picked up by a microphone (5). The amplitude of the microphone signal (7) is proportional to the crispness of the banknote and is indicative of the age of the banknote.

Abstract: An improved acoustic emission transducer is provided for sensing surface flat frequency response displacement waveforms which transducer is arranged in a packaged form to provide a device of rugged construction which is substantially immune to rough handling, which is smaller in size, and which is easy to use. The arrangement includes a sensor element mounted with an inertia mass comprised of a material substantially matching the impedence of the sensing element, and of substantial size in order to clamp one phase of the sensor element from high frequency motions. The device is mounted in a housing under a continuously applied positive pressure or force in order to maintain the sensor element in the clamped position regardless of orientation of the transducer, which has the effect of reducing undershoot, among other things, in the output response signal produced by the transducer.

Abstract: Apparatus for picking-up and analyzing emitted accoustic and ultrasonic signals by means of a piezoelectric pick-up element connected to an amplifier with high input resistance, the output of the amplifier being connected for further evaluation to selective circuits and to an evaluation device. The piezoelectric pick-up element is situated in a casing, said casing being fixed to a hollow body being tested as by a strap encompassing at least partly both the casing and the tested hollow body.

Abstract: A method for localizing and analyzing sound emissions, wherein the position of the sound emission source is determined by incoming sound pulses at various measuring locations. The arrival time of a pulse or of a pulse characteristic is measured in three or more adjacent portions of each measuring location whose width is smaller than the expected sound field diameter. From this, the propagation time difference for the portion of each measuring location is determined and the sound arrival direction is determined from these propagation time difference values for each measuring location. Subsequently, the position of the sound emission source is determined from these direction values and the position coordinates of the measuring locations.The device for carrying out this method has three or more separate converter elements (1) for each receiver measurement head (E) whose total width is smaller than the expected sound field diameter.

Abstract: There is disclosed a system for guiding, positioning, and measuring through robot control, a tool and a work zone relative to each other, by a noncontacting probe of at least one transceiver for generating shock waves, and for sensing their reflections, with one or more multiple apertured lenses for focusing and concentrating such shock waves and their reflections.

Abstract: A printed wiring board inspection, work logging and information system having a plurality of inspection and identification stations therein. The inspection stations include an ultrasonic and thermal testing station as well as a video testing station while the identification stations include circuit board identification as well as repair record identification. The information obtained from these stations as well as information obtained from circuit wiring boards positioning are fed into a computer which processes this information into an output which sets forth lists of defective joints, views of defective joints, instructions for board disposition, history of board repair and analysis of board history.

Abstract: Acoustic emissions are detected so that the amount of wear on the interior of a conduit can be directly determined. The acoustic emissions arise from plastic deformations and fractures caused by the fluid and particulate substances therein flowing through the conduit and impinging upon the interior surface of the conduit or by cavitation. The apparatus as disclosed has the capability to detect and also locate the surface area where wear is occurring.

Abstract: An apparatus for detecting cracks possibly produced in a workpiece whose distortion is being removed under pressure exerted by a pressing rod of a distortion removing machine. A detection signal produced by a sensor embedded in the pressing rod during a first predetermined period is compared with a first predetermined signal level for determining whether or not the cracking occurs in the workpiece. A detection signal produced by the acoustic emission sensor during a second predetermined period in which the workpiece is subjected to the pressure of the pressing rod without involving cracks is compared with a second predetermined signal level to determine whether or not the detecting apparatus itself operates normally.

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

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: An automatic pull tester and an acoustic emission system are herein combined to analyze the failure modes of lead frames bonded to integrated circuits. By using a discriminant analysis technique, a specific failure mode can be determined in real-time by first measuring up to five variables during the pulling operation. The five variables that may be measured comprise acoustic emission signals of a first amplitude (AE1), acoustic emission signals of a second amplitude (AE2), the time elapsed until failure (.DELTA.t), the number (n) of acoustic emission bursts above a first threshold, to the peak pulling force at failure (L.sub.max). Next, the variables measured are incorporated into a plurality of predetermined functions, each function corresponding to one failure mode (FM1 to FM5). The failure mode of the bond is determined by selecting the function having the highest value (FIG. 4).

Abstract: In a method and apparatus for monitoring tool wear, noise emission signals associated with a cutting operation of the tool are monitored and evaluated to determine when the tool has become blunt. With the system disclosed, friction noises associated with the cutting tool are excluded from analysis.

Abstract: This disclosure is directed to an acoustic Barkhausen stress detector apparatus and a method of obtaining measurements of stress in or determination of the microstructure of ferromagnetic materials. In the preferred and illustrated embodiment, stress or microstructure information in a ferromagnetic specimen is tested and measured through application of a variable magnetic field. A sensitive acoustic detecting device including an input transducer(s) and amplifier(s) forms a signal based on Barkhausen acoustic phenomena which arise from a change in the magnetic field strength. Barkhausen acoustic information is in the form of vibrations produced within the material which occur as magnetic domain walls shift. The domain wall shifts occur at various locations within the material of interest, and the acoustic vibrations are propagated through the material and are observable at the surface by one or more transducers.

Abstract: A method for the quality control of processes and construction components by diagnosing their sound vibrations during a predetermined period of time. The invention has the purpose of objectively and reliably evaluating acoustic vibrations, independent of the subjective evaluation of monitoring personnel, which can also detect very fine differences in the vibration behavior of the monitored device at an early time. To this end, the invention provides two possible solutions. In one method according to the invention, the oscillation height (.DELTA.A.sub.1 . . . .DELTA.A.sub.n) of the amplitudes of the signals are measured, depending upon a predetermined discharge time of an integrator (FIG. 1). In a second method, the impulse density of those impulses of the signal which exceed a predetermined threshold value (S) are measured.

Abstract: A method is disclosed by which incipient cracks are detected in the rotor of a fluid powered turbine while the turbine is on-line and running under substantially normal load. In a preferred form of the invention, vibrations are monitored in the rotor and signature analysis of the normal background vibration pattern is obtained to establish the spectral content of the normal vibration signal. The turbine rotor is then transitorily perturbed, preferably by changing the temperature of the motive fluid (steam temperature is changed for example in a steam driven turbine), and the signature analysis is again performed to determine changes in the vibration pattern. An increase in the amplitude of the fundamental frequency and the appearance and increase in amplitude of higher harmonics following rotor perturbation is indicative of the presence and size of a crack in the rotor.

Abstract: AE signals due to a crack developed in a metal test object are detected by a number of AE sensors mounted on the metal test object. Based on time differences between the signals from the respective AE sensors, crack source points are determined. Then, based on the crack source points, a crack source plane is determined. The crack source plane is divided into a number of areas and a point of maximum number of crack source points in each of the areas is determined. Based on the points of maximum number of crack source points in the respective areas, a shape of the crack in the test object is determined.

Abstract: A metallic wave guide having a smooth protected surface is connected at one end to a metal structural member under test and at the other to a metal plate to which a piezo electric crystal transducer of preselected frequency response is attached. The lengths of primary and secondary wave guides are carefully selected to control attenuation and time delay of the acoustical energy transmitted along the wave guides to balance inputs and provide repeatable testing data.

Abstract: This disclosure is directed to techniques for proof testing a laminated ceramic capacitor chip (10) by placing the capacitor on a planar base (26) and applying a load thereto in a direction perpendicular to the laminations. The load is applied by a compliant ram (27) and acoustic emissions emanating from the capacitor (10) pass through the ram to a transducer (28) mounted thereon. The acoustic emissions are converted to electrical signals by the transducer (28) and are forwarded to processing circuitry (29) to compare the acoustic emission signals to previously developed signals from stressed physically acceptable capacitors (10) to determine the acceptability thereof.

Abstract: Probe method and means are disclosed for guiding and positioning a robot-actuated tool, such as a gripper or a welding head, through at least one transceiver for generating and sensing focused shockwaves, the probe being associated with the tool for relative movement with respect to the object or objects being sensed, without physically contacting the same.

Abstract: An apparatus is provided for use as an onboard monitor and warning system attached to a fiberglas boom to detect potentially hazardous loads by detecting and counting acoustic emissions produced in the boom by the breakage of glass fibers. The monitor and warning system produce a warning signal when the number of acoustic emissions detected in a selected period of time indicates the existence of a potentially hazardous load. The apparatus includes a piezoelectric transducer which may be placed in contact with the surface of the fiberglas to produce electrical signals corresponding to pressure waves detected in the fiberglas. Apparatus is provided for distinguishing by the electrical signals those pressure waves which are acoustic emissions associated with the breakage of glass fibers from all other pressure waves.

Abstract: A method and apparatus for analyzing selected properties of a ferromagnetic material by magnetically inducing acoustic emissions in the material. The acoustic emission response is measured at a plurality of values of a selected response parameter, the response parameter being characterized by an acoustic emission response which, for each of its selected values, varies in mutual nonlinearity with the acoustic emission responses for the other selected values. The measured acoustic emission responses are compared to each other and to standard responses, thereby providing a more reliable measurement of the selected property than is attainable by analyzing at only one value of the response parameter. Comparing the ratio between acoustic emission responses at different values of the selected response parameter, with standard response ratios for the same response parameter values, further enhances reliability of the measurement.

Abstract: Initiation and propagation of cracks in materials is detected and monitored by (a) adhering an acoustical emitter to the area of the material to be monitored, and (b) monitoring for acoustical signals emitted by the adhered emitter, said signals produced by cracks in the material initiating in or propagating into the acoustical emitter. An acoustical emitter such as brittle plastic, glass rods or strips and metal such as tin or cadmium can be used.

Abstract: A method of testing a product for the detection of the presence therein of a defect such as a void or an inclusion, comprises cutting the product and examining the resultant noise for the presence therein of an acoustic component representative of the presence of the inclusion. The method is applied to the processing of metal into slabs, bars, rods, wire strip etc., where the ends must be cropped to remove defective material, specifically to the continuous processing of strip metal where metal strips are joined continuously end-to-end, and where the ends of each strip as rolled may include undesired inclusions such as slag. A leading end piece is cropped by a shear, and the cropping of such pieces is continued until the testing method shows that the material at the place of the cut is free of the undesired inclusions.

Abstract: A method and apparatus for inspection of ceramic parts for defects utilizes the application of an electrical test voltage to the part to be inspected, and at the same time subjecting the part to acoustic emission analysis. Use of the acoustic emission analysis allows discovery of not only defects which may arise because of the application of the electric current, but also defects or structural damage which are already existant in the part to be tested. An apparatus for carrying out the method on a high-volume basis allows rapid insertion and removal of a part between electrodes and clamps the part in place during testing.

Abstract: A non-destructive test apparatus for obtaining advance warning of impending mechanical failure by the detection and analysis of ultrasonic frequency signals which are generated internally by the equipment being tested. The detector apparatus of the present invention receives and displays in audible and/or visual form a primary carrier frequency which indicates wearing surfaces and which is characteristic of an incipient mechanical malfunction. The detector apparatus is further capable of recording signals received for subsequent evaluation and use by maintenance personnel as part of an integrated planned maintenance program.

Abstract: The disclosure is directed to a technique for monitoring signals emanating from a ceramic article (10) during a soldering operation. In order to determine whether the signals are stress wave emissions (SWE's) or noise the number of pulses (41) of the monitored signal having an amplitude exceeding a preset threshold (51), during a period of time, are counted. A count (62) proportional to the area under the envelope of the detected signal during the period of time is also made. A ratio of the count related to the area under the envelope to the pulse count is formed and compared to an empirically developed range of ratios which are indicative of a stress wave emission signal.

Abstract: A method of detecting and monitoring leaks in the piping of a nuclear reactor senses the acoustic energy from the leak and analyzes its frequency spectrum versus acoustic amplitude. A choke flow condition will exist where the leak flows at sonic velocity; here the acoustic energy is directly proportional to the area of the crack producing the leak. This is utilized to provide an indication of crack enlargement.

Abstract: Apparatus for the on-line detection and location of weld flaws wherein the acoustic emissions from a fault are segregated from other acoustic emissions by recognizing those emissions from the weld zone falling within a predetermined band of frequencies and locating the fault by determining the time required for the recognized emissions to travel to two spaced apart predetermined points.

Abstract: The explosion or destruction of a superconducting system which may occur when an abnormal state arises in any part of the system if allowed to develop into a catastrophic quenching is prevented by providing the system with an acoustic wave detecting device adapted to detect the acoustic waves emitted upon occurrence of the abnormal state, analyze the acoustic waves detected in the form of signals to determine the extent of the abnormal state, foretell stepwise the approach of catastrophic quenching and, on the basis of the data thus obtained, effect proper feedback to the system.

Abstract: A sand transport detector which detects the discrete impingements of sand particles on an elongated probe member inserted into the sand. A piezoelectric transducer element is cemented to the probe and produces an output signal when impingement occurs. With an electronic circuit coupled to the transducer, an indication of sand transport may be obtained.

Abstract: A method of estimating ground pressure in rock samples by making use of the Kaiser effect of acoustic emission. The method comprises the steps of applying load to a rock sample, increasing the load and counting the summation of the acoustic emissions produced from the interior of the rock sample. The ground pressure is determined from the magnitude and direction of hysteretic maximum stress in the ground where the rock sample was extracted.

Abstract: A device for acquiring and displaying acoustic emission fatigue data so as to facilitate the interpretation of dynamic micromechanical failure processes in materials. The load on a specimen under cyclic loading is monitored by a load cell whose output is sent to a cycle counter. The specimen is also monitored by a transducer which senses acoustic emissions. The signal produced by the transducer passes through a preamplifier, filter, amplifier and threshold detector to a pulse generator whose output is connected to the intensity modulation input of an oscilloscope or other cartesian coordinate arraying device. The load cell output is also connected to the vertical deflection input of the oscilloscope. The counter output is connected to the horizontal deflection input of the oscilloscope.

Abstract: Stress wave emission signals emanating from a weld during an AC welding operation are detected during (1) the time when the AC power is on, (2) the post weld time period, and (3) during each half-cycle of the AC weld when the absolute magnitude of the current is decaying. The stress wave emission signals are counted in each of these periods and compared to predetermined ranges of values to determine the acceptability of the weld.

Abstract: Signals emanating from a weld are detected during the post weld period and excursions of the detected signal above a predetermined threshold are counted. Simultaneously, an envelope of the signal is developed and excursions thereof above the threshold are also counted. A ratio of the signal excursion count to the envelope excursion count is formed. The ratio so formed is compared to known ranges of ratio values to determine whether the detected signal is mechanical noise or a stress wave emission signal.