Abstract: A method for the rapid acoustic emission testing of pressure vessels wherein the flow rate of the pressurizing fluid is increased while maintaining the velocity of the pressurizing fluid, as it enters the pressure vessel, below the velocity which would cause the generation of flow noise.

Abstract: A method for testing fiberglass sucker rods wherein the rod is pulled to a predetermined stress level while measuring the load, elongation and acoustic emissions. The load versus displacement is plotted in real time while the measured values are used to calculate the modulus of elasticity for various load ranges. From the measurements and calculated modulus of elasticity the quality of the rod can be determined.

Abstract: In a method for testing steam turbine rotors for embrittlement to determine which rotors to retire and which rotors to continue in operation, a varying magnetic field is applied to the rotor in a waveform to produce a detectable Barkhausen effect in the flux density developed in the rotor. The resulting Barkhausen burst of pulses is detected and is displayed on an oscilloscope. In addition, the pulse amplitude distribution of the pulses in the burst is plotted. The oscilloscope display and the pulse height distribution curve are compared with corresponding representations of the Barkhausen effect produced from a test sample known not to be embrittled, or from the rotor itself at a previous time, to make a determination of whether the rotor has become embrittled and whether to continue operation of the rotor.

Abstract: A non-destructive method for using the mechanical Barkhausen noise phenomenon, caused in fereromagnetic materials by the dislocation motion and the changing external mechanical loading, especially in determining the fatigue strength of the material. The test piece is cyclically loaded with continuously or incrementally increasing amplitude in the presence or absence of a stable magnetic field by which the test piece is magnetized and, simultaneously, measurement is made of the maximum value obtained as a function of one of: the effective value, the size distribution and the mean value of the mechanical Barkhausen noise pulses induced during fatigue of the test piece. The loading amplitude at which such maximum value is reached corresponds to a fatigue strength equal to the fatigue limit of the test piece, the latter having been subjected to a prior loading process to create a lattice defect pattern in the test piece when no stable magnetizing field is present.

Abstract: The invention is a method of determining whether an adhesively bonded joint between two structural elements meets established strength requirements. The method comprises the following steps: (1) Determining by test the levels of acoustic energy to be directed and/or focused by a transducer 12 on a minute area of the adhesively bonded joint 14 and further the application times thereof.

Abstract: Apparatus for automatically inspecting brittle articles such as containers of glass and the like has element (50) which applies a force to each article in turn, so as to propagate any cracks in the glass. Ultrasonic vibrations created during the propagation of a crack is transmitted via a constant laminar stream of liquid (76) from which the vibrations are received by a transducer head (94) of the crack detection equipment, which triggers an alarm, a visual display and/or an automatic marking or rejection device.

Abstract: Acoustic emission monitoring is a non-destructive testing technique that ects ultra-high frequency sound that stressed metal emits. In straightening a gun tube the workpiece is at first under no stress, is elastically deformed (with total springback when pressure is released), is plastically deformed (with some springback upon release of pressure), or it cracks under too great a pressure. Each of these stages produces a distinctly different type of acoustic emission. By listening to the workpiece during the pressing operation the operator can be alerted as to the stage the workpiece is in and he can adjust his operation accordingly.

Abstract: A method of measuring a characteristic of a material in a structure is the subject of the present invention. A known stress relationship S=TC/J is utilized in practicing the method of the present invention. In the foregoing formula S=strength in p.s.i.; T=torque force in pounds/inch; C=distance to the point of interest in inches; and J=.pi./2r.sup.4 where J is the polar moment of inertia for a circle of radius r (in inches). A drive head is adhesively secured to a segment of the structure to be tested. A known torque force is then applied to the drive head and this known force is translated into a measurement of the material characteristic utilizing the formula indicated. The method may be utilized to test the ultimate shear strength by failing the material or may be utilized to measure strength up to a design criteria without carrying the material to failure. Other material characteristics may also be measured utilizing the known formula set forth above and other known relationships.

Abstract: Integrity of acetylene cylinder filler material is accurately and easily determined by monitoring acoustic emission counts as a function of load and establishing the distinctive signature of faulty filler material.

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: A damping device for use with acoustic information generation machines for isolating a generation portion of the generation device from contamination by extraneous acoustic emissions. A metal isolation piece consisting of a shape-memory alloy is disposed between an extraneous noise source and the generation portion of the device. Acoustic information generation devices in accordance with the present invention include phonograph record playing devices and testing devices for recording acoustic signals generated upon stressing a test piece. Thus, the present invention provides improved phonograph record playing devices and an improved testing device.

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: 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: 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: 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: 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: As leads that have been thermocompressively bonded to ceramic substrates are pulled to destruction, stress waves are monitored and counted. The total count is compared to empirically developed ranges associated with known failures to determine the failure mode (e.g., lead failure, gold-to-gold failure, ceramic pullout).

Abstract: A vibrator is held in contact with a structure undergoing testing, such as n airplane wing. Vibrations are distributed through the structure and structural defects such as fissures will respond by emitting an acoustic signal. The acoustic signal may occur over a wide frequency range. A pick-up having a crystal transducer also makes contact with the surface of the structure to detect acoustic emissions. The crystal has a wide band response capable of detecting structural defect acoustic emissions. The pick-up has electrical leads connected thereto so that the acoustic emissions are converted to electrical signals which may be recorded or viewed on an oscilloscope. Movement of the pick-up across the surface of the structure will help determine the location of the structural defect.