Abstract: A current of predetermined frequency is fed to a coil wound around a ferromagnetic core through a fixed impedance means. A magnetic flux measurement is performed in terms of a level of a DC component of a voltage generated across the coil. A DC bias is added to the current of predetermined frequency, and the resultant current is applied through the fixed impedance means to the coil wound around the ferromagnetic core. A magnetic flux measurement is performed in terms of a level of a DC component of the voltage across the coil. A magnetic flux measuring method and apparatus for embodying the same have a high sensitivity in detecting a minute magnetic flux and an improved temperature characteristic because an output voltage little varies against a temperature variation.

Abstract: A test head through which passes a test object has at least one test probe guided in a circular orbital path around the test object. The shape of the circular orbital path of the probe, when considered in the travel direction of the object, diverges in a predetermined manner from a circular shape. A rotor guides the probe on a circular path, and the rotational axis of the rotor can be tilted with respect to the travel direction of the test object. The rotor is driven by a driving unit positioned laterally to the travel direction on a base plate by a belt drive which runs in a transmission element carrying the test head and linking it with a drive unit.

Abstract: A system and method of automatic, in-line electrical quality control of a carbon anode including detecting internal flaws in the carbon anode by measuring an eddy-current loss of the carbon anode and determining intrinsic resistivity of the carbon anode by measuring resistivity of the carbon anode and determining the electrical quality of the carbon anode according to the measured eddy-current loss and the measured resistivity.

Abstract: The detection of an internal damage in an FRP member constituted by reinforcing fibers, a matrix resin and magnetic members having a magneto-mechanical property is conducted by disposing the magnetic members in the FRP member, and measuring a change in the magnetic properties of the magnetic members by a non-destructive inspection method.

Abstract: A microcomputer or PC based non-destructive coated-object testing system and method combines thermoelectrically measured surface coating thickness data with flaw/crack depth data determined from eddy current measurements of the surface of the object to locate and selectively identify faults or cracks which penetrate the surface coating. The microcomputer controls scanning of eddy-current and thermoelectric probes over the object surface and stores measured data along with surface coordinate information to provide a color-keyed graphics display of surface conditions for visual analysis.

Abstract: A method for nondestructive examination of an object of type having localized permeability variations therein and varying surface conditions and grain structures comprises the steps of AC flux saturating a localized surface area of the object so as to magnetically saturate the surface area to quiet localized permeability variations therein and to set up a stabilized high level primary field on the surface substantially unalterable by the varying surface conditions and grain structures in the object and detecting eddy currents in the surface area. Coil structure and apparatus for implementing the method are also defined. Further, the method is disclosed as being implemented in part by the use of components of a pre-existing object evaluation device.

Abstract: An eddy current imaging system includes an eddy current sensing coil positioned proximate a workpiece for scanning the workpiece to produce a signal indicative of the integrity of the workpiece for regions in an x,y array of data. Such a signal may be a complex impedance signal representative of the amplitude and/or the phase of the signal. Two data processing techniques are disclosed for enhancing the display of a flay in the workpiece. The first includes the step of calculating a spatial derivative of the amplitude and/or phase indicative signal from the coil and providing an image of the spatial derivative to produce a C scan of the spatial derivative. The second includes the steps of determining the regions of maximum ascent and/or descent of the signal for regions in the scan and calculating an impedance plane trajectory from the data array of path points for displaying a reconstructed optimum signal independent of path pattern.

Abstract: An eddy current flaw detection apparatus, having: a pair of detecting coils disposed in a separated manner along a transit path of a conductor and coaxial with the conductor, magnetic fields generated by said detecting coils being in anti-phase; an alternating current bridge circuit, two sides of a bridge of which are comprising the detecting coils, and which, when a relative change occurs in inductances of the detecting coils and equilibrium of the bridge is thus disturbed, outputs an abnormality detection signal; a pair of resonance coils, which are disposed between the detecting coils, and coaxial with the detecting coils, and magnetic fields of which are in phase, and which are so set that in a state in which the bridge is in equilibrium, induction currents generated by said resonance coils cancel each other out; and a capacity circuit for the purpose of bringing oscillation frequencies of the detecting coils into resonance, which is connected to the resonance coils.

Abstract: An apparatus for detecting crack on an elongated metal strip employs a plurality of surface condition detecting means operating in synchronism with each other so as to detect the surface conditions of the orientations of the steel belt, which orientations are longitudinally the same position but transversely at different position. The apparatus further includes means for deriving a difference of outputs between the plurality of the surface condition detecting means. A discriminator means is also provided in the apparatus for discriminating the surface condition of the strip on the basis of the difference derived by the difference deriving means.

Abstract: An eddy current flaw detecting endoscope apparatus has an endoscope having an elongate insertable part and an objective optical system provided on the tip side of the insertable part. A flaw detecting device is provided on the tip side of the endoscope. A signal processing device processes a signal for the flaw detecting device. An eddy current flaw detecting apparatus detects a flaw in an object to be inspected and generates a flaw detecting signal. A controlling device generates a control signal controlling a controlled device with a flaw detecting signal of the eddy current flaw detecting apparatus.

Abstract: A method for operating a computer to control the manufacture process of zirconium tubes in a pilger mill operation, the computer including an electronic memory and being coupled to the pilger mill to receive, as input, data related to the operation of the mill. The method comprising, in one embodiment, the steps of storing in the computer memory respective test signals, each test signal corresponding to a signal obtained by inspecting a tube manufactured by the mill with a respective, known defective operation condition, inspecting a zirconium tube finished by the manufacture process and generating a signal representative of the physical dimensions and material configuration of the tube, comparing the generated representative signal of the zirconium tube with the stored test signals, alerting an operator if the generated representative signal of the zirconium tube correlates to a stored test signal, and identifying the defective operation condition which corresponds to the correlated stored test signal.

Abstract: A method of nondestructively inspecting a magnetic substance such as metal pipe and bar stocks, wherein the method provides a detection coil having a diameter which is specified based on the length of existent peripheral surface flaws such that the directional sensitivity of the detection coil relative to those flaws is improved. The magnetic substance is moved along an axis thereof and has an eddy current induced therein. Relative rotation of the detection coil around the magnetic substance is effected to permit detection of surface flaws.

Abstract: A phase-difference eddy current imaging system has a bridge circuit including a pair of coils with one or both coils disposed proximate an object that may contain one or more flaws. An oscillator is coupled to the bridge circuit and also to a pair of phase detectors that are coupled to the coils. A differential amplifier is coupled to the phase detectors for providing a comparison signal. A method for eddy current imaging using phase difference detection comprises providing relative movement between an object and at least one of a pair of coils, measuring the phase of the effective reactance in each of the coils, comparing the measured values, and formatting the compared values as a function of spatial position.

Abstract: A device for detecting irregularities in the surface of an object comprises at least one transducer which is movable relative to the surface of the object and an associated signal-processing unit which receives and processes output signals generated by the transducer. The signal-processing unit includes two electrical circuits, the first circuit providing a signal A which is derived from the output signal from the transducer and the second circuit including an analog shift register to provide a signal B which is derived from the output signal from the transducer and which is time delayed relative to signal A. The signal-processing unit also includes means for combining signals A and B to provide a measuring signal C.

Abstract: A flaw detector includes a readout unit; a sensor of cycles or lines, and a mechanism for driving the magnitogram and a magnetosensitive transducer. A permanent memory is made as a magnetic medium and a recording magnetic head, a test data processing unit, an interface, and a computing device are provided.

Abstract: This invention relates to a method for nondestructive inspection (NDI) of mposite materials comprising conductive fibers. The depth of broken fiber damage in nonmetal matrix composites such as graphite/epoxy and carbon/carbon materials may be ascertained and eddy current inspection is extended to include thick metal sections by this method. Inspection is possible with access limited to a single surface.

Abstract: A transducer for object examination comprises a conductive member of generally disc-shape having an opening of generally triangular configuration extending from the periphery of the member toward its center with opposed sidewalls of the opening in nonparallel relation to one another. A winding is applied to the perimeter of the conductive member and spans the opening. In certain instances, the transducer winding defines successive courses in each turn thereof which are of respective different diameter.

Abstract: An apparatus for the inspection of a stack of cylindrical objects such as roller bearings, uses an eddy current probe. The probe is positioned at an angle with respect to the surfaces of the objects in order to achieve an acceptable signal and then the objects are rotated while the probe is advanced along them to fully scan the surfaces.

Abstract: An apparatus and method for non-invasive sensing of bone healing is disclosed. The apparatus and method uses an electromagnetic field to measure impedance changes at and about the bone fracture site during the healing process. The impedance change at the fracture site is a direct indication of the mechanical strength of the fracture site. A multi-coil sensor array is taught, which may be sutured to the patient's skin or mounted onto a plug that is inserted through a window in the cast.

Abstract: A slag detector apparatus for detecting onset of 5% or less slag entrainment in a stream of molten metal employs a detection coil having an axial length at least equal to the length of a globule of molten metal in the stream being composed of a continuous succession of recurring cyclical globules of molten metal, and an impedance detector for periodic sampling and smoothing of the fluctuations of the terminal impedance of the detector coil corresponding to the fluctuating cross-sectional dimension of the stream. The detector coil is part of a signal sensitivity enhancement circuit in the apparatus which also includes a tunable capacitor connected with the detector coil. The capacitor is used for tuning the circuit to its resonance frequency so that the capacitive reactance of the circuit due to the presence of the capacitor cancels the inductive reactance of the circuit due to the presence of the coil so as to leave only an impedance that is due to resistance of the coil.

Abstract: A method and apparatus for detecting conductive material contained in glass fiber, in which it is possible to detect fine conductive material contained in glass fiber under the condition that the glass fiber is running in the process of manufacturing the glass fiber, and in which it is possible to detect only the conductive material accurately without being affected by moisture or the like.

Abstract: The object of the invention is a method and a device for materials testing using the eddy-current principle. If a coil (30) is moved in relation to test specimens, magnetic alternating fields with differing frequencies are generated, these fields induce eddy-currents that cause a secondary field in the coil (30). A number of test specimens having the same structure and the same dimensions are measured. The measured values are stored. The coordinates of the center of gravity of the measured values in the complex plane are then determined. The the phase angle is determined of that axis which runs longitudinally through the field (20) formed by the measured values in the complex plane. The center of gravity is then rotated into the origin of the coordinate system and the axis into a coordinate axis. Then a threshold value envelope determining a fault boundary is placed around the field of the measured values.

Abstract: A testing device for storing and/or processing of fault signals obtained from at least one transducer with associated electronic equipment, which fault signals are at least partially derived from one or more features, for example a defect on a test object, such as a steel blank. The fault signals are supplied to at least one discriminating circuit to distinguish between relevant and trivial fault signals. The relevant signals are then supplied to a plurality of different signal processing circuits which, for example, operate in parallel but independently.

Abstract: Typical defects are detected on a product moving relative to detecting means. An alternating magnetic field is generated in order to provoke the circulation of eddy currents on the surface of the product. A signal representative of the variations of the eddy currents is collected by means of a differential sensor and is demodulated by projection along an angle of adjustable phase in order to detect the disturbances introduced by the defects to be detected. This angle of phase is determined so that the projection of the collected signal has a minimum mean value, in order to eliminate disturbances of the collected signal due to repetitive surface irregularities. The component of the collected signal obtained by the projection is converted into digital form, and the digital signal thus obtained is filtered using a digital filter whose characteristics are predetermined as a function of a type of defect to be detected.

Abstract: A device for measuring or testing of an object, for example rolled wire, a tube, or a billet, to detect surface discontinuities employs a sensing transducer which is oscillated backwards and forwards over the surface of the test object by means of a motor, the oscillations taking place in the form of a curved path extending transversely of the longitudinal extent of the object.

Abstract: Apparatus for determining the location of surface defects on a test piece of electrically conductive material by scanning the surface with at least one sensor arrangement comprising proximity sensors based on eddy current induction. The test piece may be moveable, e.g. advanced, in relation to the holder arrangement which is arranged to move the sensor arrangement in a sweeping or scanning movement from one side of the test piece to the other. The position of the edge of the test piece, is determined successively, e.g. for each scan cycle and the location of detected cracks is calculated with a starting point from the detected edge position.

Abstract: A system and method for nondestructive testing of a part using eddy current impedance measuring techniques. An eddy current probe is positioned above the surface of the part for measuring an induced eddy current signal and generating an electrical signal representative thereof. A first and second movement signal is generated representative of a first and second scan direction of the probe. Relative movement is effected between the probe and the part, whereby the probe scans the part for producing electrical signals varying as a function of eddy current signal. The electrical signals are converted to mutually perpendicular drive signals representative of the eddy current signature at a corresponding location of the part. The first and second movement signals are combined with the mutually perpendicular drive signals of and second composite signal which varies as a function of the movement of the probe and eddy current signal.

Abstract: A rotating-probe type defect detecting device, used for continuous inspection of an elongated test object moving in the longitudinal direction, such as round metal bar drawn out from a set of dies, comprising a plurality of test probes supported by a rotating frame structure around the object in a plane orthogonal to the central axis of the object for revolving about the object at high rotational stability, is provided. The device includes an inventive circuit for processing the output signals of the probes to enhance defect indicative portions of the signals and suppress the noise level, thereby exhibiting an improved detection characteristic of high signal-to-noise (S/N) ratio.

Abstract: Method and apparatus for scanning a generally cylindrical workpiece for flaws. A cylindrical metallic sleeve is rotatably supported about a workpiece path of travel. Two differentially wound energization coils surround the sleeve near two apertures in the sleeve. The coils are energized with a high frequency signal that induces eddy currents in the workpiece. The apertures periodically disrupt the eddy current inducing magnetic fields and enhances signals from the coils indicative of the presence of flaws in the workpiece.

Abstract: An invention is disclosed which supports an eddy curent probe at a predetermined distance from a surface to be scanned. In another embodiment, the probe is scanned by rotation about an axis and along an arc of predetermined length and position.

Abstract: A flaw detection apparatus for detecting flaws at the outer surface of a product, such as a steel bar, wire or steel pipe, which is round in section and produced by the hot rolling, by use of a probe of non-contact type and rotating around the product to be inspected, the apparatus providing a means for suppressing vibrations of an object to be inspected, a means for measuring a distance (lift-off) between the object to be inspected and the probe, and a means for carrying out positional control on the basis of the detection result of the lift-off measurement so that the axis of rotation of probe is allowed to be coincident with the axis of object to be inspected.

Abstract: An eddy current crack detection system has an inductive probe coil forming part of an oscillatory circuit. The coil voltage is fed to a measuring device a change in amplitude of the coil voltage being used as an indication of a crack. In order to compensate for lift-off in the amplitude of the coil voltage, a control signal is generated related to the magnitude of lift-off, and controls the value of a variable damping resistor in the oscillatory circuit.

Abstract: A method of detecting a flaw in a moving chain is disclosed in which two identical free-running oscillators are used, and through the inductive core of one a chain is passed. A comparator circuit monitors the oscillators' outputs so that changes in mass of the chain may be sensed.

Abstract: A liftoff suppression apparatus utilizing a liftoff sensing coil to sense the amount a ferromagnetic resonance probe lifts off the test surface during flaw detection and utilizing the liftoff signal to modulate the probe's field modulating coil to suppress the liftoff effects.

Abstract: Method for determining the position and depth of unevenness in an inner surface of a pipe with the aid of a scanning head which is adapted to travel through the pipe and which is rotatable about the pipe axis. The invention provides an inductive, or capacitive, depth scanning process, which operates in a contact-free manner with respect to the inner pipe surface. This is attained by means of an inductive method in that, as is illustrated in the drawing, there is arranged at a distance from the pipe inner surface the scanning head which is guided and in which a coil (2) of a measuring, resonant circuit is mounted and, above the inner periphery of the pipe, a coil 1 of a reference, resonant circuit is arranged, and then, after the frequencies of both resonant circuits have been brought, prior to measuring, to an identical value in each of a multiplying circuit (10, 7, 13 respectively 11, 8, 14), they are measured and converted into an adjustable difference of the multiplied frequencies (f.sub.1, f.sub.

Abstract: Nondestructive method of electromagnetically detecting flaws in a metallic object, comprising: placing an object to be tested for flaws adjacent a sensing head which comprises a portion of a sensor ring made of electrically conductive material and arranged inside an electromagnetic coupling coil excited by a high frequency current; causing the object and the sensing head to move relative to each other so that a flaw in the object causes the impedance of the coil to change; and detecting the change of the impedance.An apparatus for carrying out the method is also provided.

Abstract: A computer-based eddy current nondestructive or ultrasonic testing system automatically inspects rolling mill roll surface defects during roll grinding operations comprising articulated probe means, eddy current, or ultrasonic, test instrument means, computer means, display and printer means. The articulated probe mechanism is mounted on a traversing roll grinder carriage, is automatically positioned over the test roll in response to control means initiated by the grinder operator, and has a probe head with a controlled fluid bearing, air or liquid, to automatically maintain probe-head-to-test roll gap. One or multiple eddy current, or ultrasonic, probes in the test head generate anamoly test signals, which, together with a probe head temperature sensor signal, are processed in a modified test instrument and the computer. Computer plots defects signals as color bars vs. probe position and displays these bars graphically and other messages on a color CRT display and/or a graph printer.

Abstract: An eddy current test apparatus and method in which multiple sequential test frequencies are employed. The voltage induced in a sensing coil at said test frequencies are multiplexed and frequency translated to provide a single frequency for processing. The apparatus employs a single channel to process the induced voltages.

Abstract: In ferromagnetic resonance (FMR) probe apparatus for detecting surface flaws in a metal surface, probe impedance changes resulting from flaws are distinguished from impedance changes resulting from probe lift-off from the metal surface. A constant magnitude dc magnetic field and a constant frequency and constant magnitude rf magnetic field are applied to the ferromagnetic crystal and the real and imaginary components of probe impedance are detected. The impedance changes due to flaws are at least partially orthogonal to the impedance changes due to lift-out, and by observing probe impedance on an oscilloscope the presence of a flow or the occurrence of lift-off are readily identified.

Abstract: An eddy current flaw detection system for inspecting a workpiece for surface flaws is described. The system has a search unit for mounting a pair of eddy current search coils in close proximity to a workpiece at locations which are longitudinally spaced with respect to the workpiece. The system is disclosed in the environment of a workpiece support and transport mechanism which causes a workpiece to rotate and move axially with respect to the search unit.Coil energizing and detection circuitry is provided having a pair of eddy current channels. Each channel energizes a connected one of the search coils to induce eddy currents within a workpiece at slightly different energization frequencies. Each channel has an output for producing signals indicating the presence and severity of detected flaws. The coil energization at different frequencies results in each coil responding to self induced eddy currents rather than currents induced by the other of the two coils.

Abstract: Digitally controlled eddy current test apparatus for detecting flaws, their extent and location. The apparatus provides absolute and differential measurements. The apparatus employs multi-frequencies with the signals from the test coils mixed in a predetermined manner to reduce unwanted signals such as may be introduced by wobble (lift-off) and support plates.

Abstract: An apparatus for characterizing a surface anomaly in an electrically conductive sample includes an oscillator with an amplifier for supplying gain to the oscillator, a feedback loop linking the input and output of the amplifier, a two port ferromagnetic resonator connected within the loop to modulate the level and frequency of oscillation of the oscillator in response to eddy currents induced in the surface of the sample by the resonator, a variable attenuator connected within the loop to adjust the power level of the oscillator, and an adjustable phase shifter connected within the loop for changing the total phase shift of the loop. A sensing circuit is operably connected to the output of the amplifier to monitor the resonance parameters of the oscillator.

Abstract: A probe and method for detecting surface flaws in metals. The probe operates at microwave frequencies and uses a ferromagnetic resonator. The resonator experiences a frequency shift when brought into proximity with a metal because of the perturbations of the demagnetizing fields at the boundaries of the resonator. A crack in the metal additionally disturbs the field and causes additional perturbations of the frequency. The perturbations in frequency are detected to provide an indication of flaws in the surface of the metal.

Abstract: Inspection equipment for detecting defects in the surface of steel billets or other elongate members includes high-frequency energized eddy-current surface scanning probe which transmits signals representative of the surface condition and the probe surface spacing to a dual-channel receiver.The signals from both channels of the receiver are combined to provide outputs representative of the surface condition compensating for changes in sensitivity resulting from changes in the probe spacing during scanning.Probes may be positioned above the plane surfaces and/or the corners of the billet. The latter being positively located through rollers which bear against the two sides of the billet which flank the edge under inspection.

Abstract: The surface defect detecting apparatus for rotating cylindrical metal pieces which move in a lengthwise direction relative to a sensor block, has a plurality of eddy-current flaw detecting coils facing the test piece. The sensor block rotates about a horizontal axis extending vertically with respect to the axis of the test piece to follow up deflections of the test piece in the direction of the axis of rotation. Front and rear ends of the sensor block, have a pair of guide wheels that engage the piece; also present are color marking nozzles for marking defective areas in response to detector signals. Relative movement in the longitudinal direction of the test piece is carried out by means of a carriage carrying the sensor block. Each guide wheel is spaced from another in a plane transverse to the longitudinal direction of the test piece.

Abstract: A surface defect detecting apparatus having at least one sensor block for movement in respect of rotating cylindrically shaped electrically conductive metallic material to be inspected by scanning an outer portion of the surface of the material. The sensor block has spaced guide wheels at front and rear parts thereof in the spiral scanning direction which rotate in response to the rotation of the material; and a coil holder for supporting a plurality of eddy-current flaw detecting coils arranged longitudinally in a row in the direction of movement, intermediate between pairs of guide wheels at the front and rear parts opposite to the outer surface of said material with a predetermined gap therebetween. A turning wheel at each of the front and rear parts of the coil holder is rotatable with respect to the outer surface of the material so as to maintain the predetermined gap.

Abstract: A method and device for nondestructive testing of articles using the eddy principle current and multifrequency technique. The characteristic feature is that the measurement is generally independent of the position of the article to be tested in relation to the pickup probe. In comparison with known devices the present device is easy to handle.

Abstract: A test head for the inductive surface testing of metallic workpieces is provided with eddy-current probes respectively disposed in a plurality of holes in a holder. Each eddy-current probe is part of an individual resonant circuit and formed of coil with a ferrite core, the axis of the coil extending substantially at right angles to the workpiece surface. The holder comprises an electrically or magnetically conductive material, thereby increasing the area over which the field of each said probe is effective.

Abstract: Apparatus mounted on a vehicle is arranged to provide a signal indicative of the spacing between the vehicle and a metal article being less than a predetermined amount, the predetermined amount being small compared with the length of the vehicle. The apparatus in combination with the vehicle comprises a plurality of sensor units mounted externally of the vehicle and each comprising a coil, the sensor units being arranged electrically in parallel to each other. A respective oscillator circuit is coupled to each coil to generate a respective electromagnetic field, and to provide an output signal in response to any disturbance of a respective one of the electromagnetic fields as a result of the spacing between the vehicle and the metal article being less than the predetermined amount.

Abstract: A method and apparatus for electromagnetic testing of magnetic and/or electrically conductive materials. The apparatus includes the usual test probe which carries excitation and pickup coils and is placed against a test piece of magnetic and/or electrically conductive material. The invention eliminates inaccuracies in the test caused by variable distances or gaps between the probe and test piece surface. Properties of the test pieces are determined by applying a controlled alternating drive current to the excitation coil so as to produce a predetermined a-c voltage in the pickup coil and measuring the drive current applied to the excitation coil when the time-integral of the voltage induced in the a-c pickup coil corresponds to zero magnetic flux in the gaps.