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: An engine roughness sensor for generating speed normalized digital roughness signals indicative of the variations in magnitude between successive torque impulses imparted to the engine's crankshaft by measuring the period or time it takes the crankshaft to rotate through the same angle for each torque impulse is disclosed herein. The digital roughness signal is normalized as a function of engine speed by dividing the measured magnitude of each torque impulse by a signal indicative of the engine speed to reduce the magnitude of operator induced variations in the generated roughness signals. In an alternate embodiment, the disclosed engine roughness sensor generates a second difference roughness signal which is the difference between the sequentially generated roughness signals.

Abstract: A closed loop engine roughness fuel control for an internal combustion engine operative to maintain the operation of the engine at a predetermined roughness level is disclosed herein. The control measures two rotational intervals within each torque impulse imparted to the engine's crankshaft by the combustion process and generates a speed normalized engine roughness signal indicative of the engine's actual roughness. The engine roughness signal is multiplied by the engine speed and summed with a reference signal to generate a bias signal operative to modify the quantity of fuel being delivered to the engine maintaining the operation of the engine at a predetermined roughness level. A signal indicative of the first derivative of the engine speed is also summed with the reference and roughness signal to compensate for false roughness signals generated during transient modes of operation.

Abstract: A visual graphical display of instantaneous mechanical vibration versus frequency over a selected frequency spectrum is presented to provide a vibration analyst with a prompt overall visual impression of the mechanical vibration characteristics of a rotating device which is under surveillance. In an alternative application, the visual display permits a rapid adjustment of an electrical bandpass filter of an associated vibration analyzer. The device employs several trains of diodes which are arranged so that one or more diode in each train is illuminated at any one moment.

Abstract: A system for carrying out vibrational analysis of machinery and the like wherein a voltage controlled filter is combined with a phase-locked feedback loop to detect maximum amplitude within a given frequency band. A simply derived readout of frequency and amplitude is made available with the arrangement and operation over three or more decades of frequency is availed without manual switching and the like.

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: The impact signal derived from an acoustic transducer has a unique signature represented by its frequency spectrum. The present invention generates under predetermined conditions with objects, each of definite weight and form, a series of impact signals for reference purposes and correlates an actual impact signal from an unknown impacting object with such reference impact signals by comparing the frequency spectra, thereby to indirectly recognize the impacting object.

Abstract: An apparatus and method for determining the material properties characterizing a fluid contained in a cavity inside a solid comprises analyzing the resonances in the amplitude of elastic waves scattered by the cavity. Specifically, the resonance positions and their widths are used to determine the sound speed and the density of the cavity filler. The sound speed is found from the spacing between two consecutive overtones of any mode, which asymptotically becomes uniform for the higher-index overtones. The density is obtained from the width of any high order resonance and accordingly, all the information about the material composition of the filler is contained, and can be extracted, from the high-frequency asymptotic region.

Abstract: The shear absorption of a viscoelastic material is determined by directing acoustical energy at the viscoelastic material and sampling the backscattered signals that result when compressional waves propagate through the material and are scattered by either a fluid-filled or evacuated cavity contained therein. The backscattered signals are converted to a resonance amplitude versus frequency domain and the shear absorption of the viscoelastic material is determined from the frequency and the half-width of the resonance peaks.

Abstract: A data acquisition system utilizing a microcomputer and incorporating a plurality of monitors each adapted to produce an electrical signal indicative of a physical condition of apparatus to be monitored. The electrical signals are fed via multiplexing equipment and analog-to-digital converters into the microcomputer which is equipped with print-out means. The system is such that the level of any one or all of the signals from the respective monitors can be printed out as well as a change in the condition of any signal. Means are incorporated into the computer for calculating and printing the trend (i.e., the slope of a plot of signal amplitude versus time) of a succession of stored signals from any monitor which would indicate a probable malfunction of a device being monitored and the probable time to failure. In the case where the signals from the monitors comprise vibration signals, the system performs an automatic frequency spectrum analysis whenever a probable or actual malfunction is detected.

Abstract: An ultrasonic search unit for locating defective fuel elements within a fuel assembly used in a water cooled nuclear reactor is presented. The unit is capable of freely traversing the restricted spaces between the fuel elements.

Abstract: An apparatus and a method are provided for detecting and measuring vibrations of a selected portion of a drill string in a bore hole. The vibrations are detected by a transducer which produces an electrical signal representative of the vibrations. The signal is applied to a band-pass filter which produces an output signal representative of vibrations occurring at frequencies within the pass band of the filter. The pass band is repetitively stepped through a predetermined frequency range under the control of digital circuitry.