Abstract: A magnetic flaw detector for use in small-diameter tubular goods employs a second magnetic field to confine a first magnetic field to reside within a desired volumetric region in the wall of a specimen under test. A flux leakage detector and a variable reluctance sensor provide means for detecting and discriminating between defects on the inner and outer surfaces of the specimen.

Abstract: An improved AC susceptometer and methodology for its use which is particularly suitable for the characterization of the properties of superconducting materials. Added to the circuitry of a conventional AC susceptometer is frequency domain analytical equipment for measuring the induced magnetic response. The addition of frequency domain measuring equipment permits the determination of the harmonic components of the induced magnetic response. The measurement of the harmonic components of the response also provides novel methodology for studying the phenomena of flux penetration, flux pinning and movement and permits the measurement of parameters such as lower critical field, critical temperatures, and the irreversibility line.

Abstract: An improved AC susceptometer and methodology for its use which is particularly suitable for the characterization of the properties of superconducting materials. Added to the circuitry of a conventional AC susceptometer is frequency domain analytical equipment for measuring the induced magnetic response. The addition of frequency domain measuring equipment permits the determination of the harmonic components of the induced magnetic response. The measurement of the harmonic components of the response also provides novel methodology for studying the phenomena of flux penetration, flux pinning and movement and permits the measurement of parameters such as lower critical field, critical temperatures, and the irreversibility line.

Abstract: A method and system for accurately inspecting an electroconductive film using an eddy current and a process and apparatus for production of an optical fiber which measures on-line the electrical resistance, which shows the state of formation of the electroconductive hermetic coating of the optical fiber by the electroconductive film inspection method and reflects back the measurement results to the hermetic coating forming conditions are disclosed. Optical fiber is made up of a core, cladding, amorphous carbon film or other electroconductive hermetic coating formed on the outer surface of the cladding, and a protective coating. The electrical resistance of the hermetic coating generates an eddy current at the coating, the eddy current generated is detected, and the phase angle of the complex impedance is detected to enable calculation.

Abstract: An apparatus for detecting the degree of deterioration in lubricating oil including a grid-like capacitive sensor, that uses the lubricating oil as a dielectric medium, and a magnetic field imposed upon the oil to attract ferromagnetic wear particles into the vicinity of the sensor. Preferably, the magnetic field is generated by a permanent magnet and an electromagnetic aligned such that the magnetic field produced by each magnet acts upon the oil along the same axis.

Abstract: A method and apparatus for inspecting the profile of the inner wall of a conduit, such as a heat exchanger in a steam generator by a probe body that includes eddy current sensing coils. The number of eddy current sensing coils is increased for more completely sensing the conduit surface without a corresponding increase in coaxial cables by the use of a bank switch which switches respective banks of coils to existing conduits.

Abstract: A method for improving eddy current flaw detection by simultaneously exciting a select plurality of eddy current probe elements with a multiplicity of select frequencies in a simultaneous parallel or serial manner to form a corresponding multiplicity of direct and/or differential images which can be processed together for improved eddy current image resolution. Select eddy current probe elements when driven at select multiple frequencies further provide a capability for simultaneous flaw detection and characterization by dual resolution scanning. Dual flaw resolution is accomplished by first locating a flaw using low resolution frequencies; and thereupon, switching to higher resolution frequencies to characterize the flaw.

Abstract: Eddy current probes for ferromagnetic tubes of relatively small diameters are disclosed. A probe housing is made of non-ferromagnetic material and shaped to be introduced into the tube for inspection. The probe housing includes at least two eddy current measuring assemblies either of these assemblies includes magnetic field generators for producing a maximum magnetization at a predetermined area of the tube and a minimum magnetization at a diametrically opposite area of the tube. At least one eddy current measuring coil is associated with each magnetic field generator to measure the eddy current generated in the tube and which has a relatively high sensitivity to an anomaly at the maximum magnetization area. Further the current measuring assemblies are spaced apart axially within the housing and are rotated about its central axis by a predetermined angle so that each assembly differs in sensitivity to an anomaly depending upon their location within the housing.

Abstract: An inductance-type displacement sensor which can measure the displacement of a measured object of magnetic material without any contact with the object. A pair of series connected coils is provided adjacent to the object so that the inductance of the coils varies in response to a displacement of the object from a predetermined position. The inductance, the number of windings, the direction of the windings and the section of each of the cores are so set that the magnetic flux produced by one of the coils runs in a direction opposite to that of the magnetic flux produced by the other coil and the densities of the respective magnetic fluxes are identical with each other.

Abstract: Non-destructive methods of measurement for determining the thickness of thin layers, using the magneto-inductive method or the eddy-current method yield measured values which depend not only on the actual layer thickness present, but also on the shape of the measured object. It is the object of the invention to specify in a simple way, and without it being necessary for an operator to change his way of thinking, a device and a method in accordance with which the layer thickness indicated is virtually independent of the shape of the measured object. With regard to the device, this is achieved according to the invention when the probe has at least two different coil devices and, with regard to the method, when a corrected layer thickness is calculated from the different measured values of the two coil devices.

Abstract: A rotary head for scanning the surface of elongated test materials (62) by eddy current transducers (60) is additionally provided with means for magnetization of the test material (62) over an intended test range making it now possible to achieve sensitive testing of non-bare ferromagnetic bars and wires, testing for "smeared cracks" where surface has closed above the material separation, and testing of welded austenitic pipes. For the magnetization, parts of the housing (10) as well as a rotating hollow shaft (40) are employed in the conduction of magnetic flux, and special measures are taken for the homogenization of the magnetic field in the test range.

Abstract: A non-destructive eddy current test device using additive flux/substractive flux switching includes a generator supplying a sinusoidal signal, two power amplifiers of equal and opposite gain, a changeover relay, two impedances and two coils forming a Wheatstone bridge, an amplifier controlled by a binary signal to add or subtract and two synchronous detectors for supplying signals representing the real part and the imaginary part of the difference between the complex impedances of the coils. A control device supplies to the changeover relay and to the amplifier a control signal for obtaining additive or subtractive fluxes in the two coils and for respectively subtracting or adding the two output voltages of the Wheatstone bridge. The device is applicable to the non-destructive testing of metal parts.

Abstract: The invention discloses an inspection system for detecting near surface flaws or defects in conductors using nondestructive eddy current testing suitable for industrial application. The system provides a method and apparatus for acquiring real time, synchronized, discrete eddy current measurement signals from a plurality of sufficiently disposed, spatially correlated eddy current probes then processing and formatting said measurement signals automatically over parallel data channels to accommodate digital processing techniques in order to produce on eddy current image. Utilizing digital image processing provides a capability for improving flaw detection limits while simultaneously enhancing image resolution.

Abstract: A proximity sensor is provided with a means for directly measuring parameters of a proximity sensor coil which permit the determination of both the AC and DC resistances of the coil. These parameters are then used to determine a discriminator value magnitude according to a mathematical relationship that has been predetermined through previous analysis of empirical data for the particular coil and application intended for the proximity sensor. In one particular application of the present invention, the rear AC resistance is utilized and is added to the DC resistance after the DC resistance has been mathematically altered by a preselected factor. Alternative embodiments of the present invention can also utilize the imaginary AC component of the impedance either by itself or in conjunction with the rear AC component of the impedance.

Abstract: An embodiment comprises a generator constituted by a quartz crystal oscillator and programmable frequency dividers; a power amplifier providing a periodic excitation signal, of squarewave form; two coils electromagnetically coupled to a metal part to be tested; and measuring means comprising two synchronous detectors for measuring the real part and the imaginary part of the difference between the complex impedances of the coils. The frequency stability of the generator effects an improvement in the accuracy of the impedance measurements, when these measurements are made at different frequencies. For application to non-destructive testing of metal parts by eddy currents, at different frequencies.

Abstract: A system for identifying and measuring stress at specific locations within a ferromagnetic material by the production and detection of Barkhausen noise during magnetization of the material. The method involves introducing into the material a time varying magnetic field component and a spatially-varying magnetic field component that in combination create a singular zero magnetic flux element within the material that "sweeps" from one position within the material to another and back. By time-gating the detected acoustic Barkhausen signal that results as this zero flux element moves within the material, the signal is isolated as having been generated at a specific depth within the specimen. Since the level of Barkhausen noise varies with stress, a tomographic mapping of stress is obtained for the interior of the ferromagnetic specimen. Through the use of a computer, a three dimensional map of stress in the ferromagnetic material is obtained.

Abstract: The invention is a method and apparatus for characterizing residual uniaxial stress in a ferromagnetic test member by distinguishing between residual stresses resulting from positive (tension) forces and negative (compression) forces by using the distinct and known magnetoacoustic (MAC) and a novel magnetoacoustic emission (MAE) measurement circuit means. A switch permits the selective operation of the respective circuit means.

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: The present invention provides a method and apparatus for performing nondestructive material assessment of service exposed combustion turbine blades. According to the invention, the testing is accomplished by inserting eddy current (EC) probes into the blade's cooling holes, and evaluating the eddy current response of the blade. The eddy current probes are preferably coupled together in a differential mode. The measured response is then compared with a previously determined response corresponding with a known material condition. An assessment of the blade is made on the basis of this comparison.

Abstract: Apparatus for detecting surface flaws in cylindrical articles having central longitudinal axes, including a guide assembly for guiding the cylindrical articles along a displacement path having a central longitudinal axis extending coaxially of the central longitudinal axes of the articles and a detection coil assembly positioned in annular relationship with the displacement path for producing a signal representative of the surface geometry of a cylindrical article which traverses the displacement path.

Abstract: Eddy current probes for detecting defects in a ferromagnetic tube are disclosed. The probe uses partial magnetic saturation and includes two or more eddy current measuring coil assemblies in a probe housing. The coil assemblies are spaced apart from each other and located at positions of different magnetic saturation.

Abstract: Flaws in an electrically conductive sample object are detected by cancelling the magnetic field generated by a detection current passed through the sample object by passing the current back through an unflawed field cancelling object placed next to the sample object, and measuring the uncancelled field produced by any flaw, preferably with a superconducting quantum interference device (SQUID) magnetometer. Elongated objects such as tubes and rods are fed through a sleeve which forms the field cancelling object, with the current applied to the elongated member and passed to the field cancelling sleeve through sliding contacts.

Abstract: A surface impedance measurement device comprises a transmitting antenna producing a magnetic field in the area surrounding a material to be tested and a receiving antenna receiving the magnetic field. An electric voltage wobbled in frequency is applied to the transmitting antenna, and a circuit measures the voltage at the terminals of the second antenna. For the antennae to be applied on the same side of the material to be tested and of which the surface impedance is to be measured, the antennae are superposed by the intermediary of a dielectric wedge in a compact probe. The impedance measurements are then independent of the dimensions and geometry of the material.

Abstract: Both a system and a method for determining the length of a discontinuity such as a crack or other fault in the interior wall of a steam generator heat exchanger tube is disclosed herein. The apparatus generally comprises an elongated probe assembly which includes a plurality of eddy current coils mutually separated at known distances with respect to each other along the longitudinal axis of the probe, and an eddy current coil actuating device for separately and independently actuating each of the coils to provide an adjustable electromagnetic sensing field. In the method of the invention, the probe assembly is positioned adjacent a discontinuity and then each eddy current coil, separated by a known distance, is independently actuated and its reading recorded to determine which of the coils actually detects the discontinuity.

Abstract: A method for contactless measuring the values of magnitudes which relate to an electrically conductive material in solid or liquid form, for instance such magnitudes as the distance of the conductive material from a given point, linear dimension(s) of a body that incorporates such material, the electrical conductivity value of the material, and the temperature of the material. In accordance with the method, an electromagnetic field, generated with the aid of a constant current which flows through at least one field generating coil, is caused to penetrate at least partially into the material. The supply of current to the at least one coil is discontinued subsequent to the magnetic field having penetrated the electrically conductive material to an extent sufficient for the intended magnitude to be measured.

Abstract: A tool dullness indicator and method comprising the measurement of eddy currents at a known, controlled frequency directly in the tool by measuring the phase angle shift in a coil when a sample is put into or next to the coil. The phase angle change caused by presence of a workpiece is measured when the tool is sharp to provide a reference reading taking into account the surface hardness and other bulk properties of the workpiece, and arriving at a parameter that is dependent on eddy current changes, such as phase angle shift or other measurable changes related to eddy currents in the part, and then analyzing the workpiece, either while working, or at a set programmed check time to determine when the tool is dull as a function of the change in eddy current characteristics caused by work hardening.

Abstract: A measuring device for contactless control of a design of structural elements composed of an electrically conductive material comprises at least one coil through which an alternating current flows and whose measuring voltage is influenced by a structural element, and electronic evaluating unit arranged to compare the measuring voltage of the coil influenced by the structural element with a nominal value, the coil being formed as a cylindrical coil.

Abstract: A measuring device for contactless determination of condition of screw shaped structural elements comprises two oppositely located coils supplied with an alternating current spaced from one another so that an electrically conductive structural element passes therebetween, and transporting elements formed so that the structural element is guided on an edge so that a distance between the structural element and at least one of the coils remains constant during a measuring process.

Abstract: Eddy current probes for detecting internal defects in a ferromagnetic tube are disclosed. The probe uses a plurality of eddy current measuring means, each being operated at a different operating point on the impedance diagram. By operating more than one such eddy current measuring means simutaneously, noises by, for example, permeability variation of a ferromagnetic material and internal magnetic deposit, can be made less influential.

Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by a plurality of non-inductive transducers. The transducers are interconnected to produce a composite signal. The composite signal is compared to a reference signal.

Abstract: An array of nested sets of electromagnetic coils. Each set of two coils is useable both as Helmholtz coils and as deGaussing coils. In each set, the two coils are wound in the same direction and the two coils are on a common axis. The common axes of the three sets are mutually orthogonal. For each set of two coils, the outer two ends of the two coils are connected to two single terminals, while the inner two ends of the two coils are connected to one common terminal. By connecting one side of a DC power supply to one single terminal, and by connecting the other side of the DC power supply to the other single terminal, each set of two coils will operate as Helmholtz coils. By connecting one side of a DC power supply to parallel variable resistors, each resistor in turn being connected to a single terminal, and by connecting the other side of the DC power supply to the common terminal, each set of two coils will operate as deGaussing coils.

Abstract: Several phenomena which occur commonly in graphite composites, as well as other materials, and which affect the impedance of an eddy-current probe have been characterized on the complex impedance plane. An eddy-current method is disclosed by which a target material is stimulated at several frequencies, the impedance of the probe is measured and compared to the impedance of reference material, and the condition of the target material is determined. The method described is capable of finding the signatures of a number of conditions commonly found by eddy-currents, and can be programmed to find others, such as conductive and non-conductive plating thicknesses, and inclusions of material with relative ferrous materials. Because the method determines faults on the normalized impedance plane, it is capable of being used on other conductive materials in addition to graphite composites.

Abstract: A rotating head mechanism of a rotary type AC magnetic flux leakage flaw detector comprises a rotating disc which has an opening for passing a test piece for flaw detection, mounting frames which are disposed in the rotating disc so as to oppose to each other with the opening located therebetween, shafts which are rotatably disposed across the mounting frames and each of which has external threads of senses opposite to each other at a position on one side of the opening and a position on the other side thereof, a first nut which engages the external thread of one sense in the external threads of each shaft, a second nut which engages the external thread of the other sense in the external threads of each shaft, a first cradle which is coupled to the first nuts, a second cradle which is coupled to the second nuts, a first exciting magnetic poles/detecting probes-assembly which is mounted on the first cradle, a second exciting magnetic poles/detecting probes-assembly which is mounted on the second cradle, and ro

Abstract: A compound eddy current probe comprising a nest of concentric ferrite cup re probes. Both the inner and outer radii of the activated coil can be selectively altered by operator or automatic program to correspond with the size and thickness of the material under test.

Abstract: An apparatus for measuring the thickness of a coating on a substrate has a bridge circuit including four coils. One coil is placed near the coated substrate and another placed near an uncoated substrate of the same material. An oscillator is connected to the bridge circuit and frequency sweeps, e.g. from 10 KHz to 10 MHz. Phase differences between the voltages induced in the coils are detected to determine conductivity changes with frequency. A method for measuring coating thickness comprises generating variable frequency eddy current in coated and uncoated substrates of the same material and comparing the generated eddy current.

Abstract: Devices and analytical techniques are disclosed for measuring spatial profiles of complex permeability and conductivity of a material by multiple wavenumber interrogations. Coil array structures are disclosed which define a number of different fundamental wavelengths (or wavenumbers). Spatially periodic interrogation signals (of temporal frequency ".omega.") from the coil array structures are attenuated by varying degrees in the material undergoing analysis, depending on the wavenumber ("k"), thereby permitting the derivation of composite complex permeability/conductivity profile.

Abstract: A multiparameter magnetic inspection system for providing an efficient and economical way to derive a plurality of independent measurements regarding magnetic properties of the magnetic material under investigation. The plurality of transducers for a plurality of different types of measurements operatively connected to the specimen. The transducers are in turn connected to analytical circuits for converting transducer signals to meaningful measurement signals of the magnetic properties of the specimen. The measurement signals are processed and can be simultaneously communicated to a control component. The measurement signals can also be selectively plotted against one another. The control component operates the functioning of the analytical circuits and operates and controls components to impose magnetic fields of desired characteristics upon the specimen.

Abstract: An assembly formed by an electronic circuit in which a microprocessor is included that emits a signal from which additional signals are generated by a frequency synthesizer. These signals are applied to coils which form the emitting antenna, after being filtered and amplified. From these signals, the sample signal is generated and is picked up by other receiving antennas. After being amplified and filtered and all the distortion elements removed, the picked up signals are applied to proper frequency filters to obtain at the output signals having amplitudes proportional to those generated in the sample.

Abstract: An eddy current testing device for inspecting test objects, for example billets, with respect to surface defects, for example surface cracks, comprises at least one transducer/sensor, for example a surface transducer or surface transducer arrangement, which is made to scan the surface of the test object. The device is characterized in that the effect of harmless surface blemishes on the testing device is suppressed, at least partially, by compensating for the sensitivity characteristic, in the scan direction of the transducer/sensor, with respect to the surface defect.

Abstract: Detection of both surface defects of a non-ferromagnetic test body as well s the presence of ferromagnetic particles in the test body by inducing eddy currents and D.C. fields in the body. The resulting signal voltages are filtered and separately examined.

Abstract: A ferrous metal inspection device particularly for elongated parts provides high intensity DC magnetic fields in each of two modes contemporaneously. One mode is generated by passing a DC current axially through the part to be inspected and the other is generated by a separate DC current passing through a pair of electromagnet coils positioned one at each axial end of a part to be inspected. Magnetic field lines are thereby generated in a pair of mutually orthogonal planes. Control and polarity of the two direct currents is effected by controlling the phase of conduction of separate corresponding silicon controlled rectifiers. The part to be inspected is drenched with a mixture of fine ferrous particles in a liquid vehicle. Solenoid wound coils connected in series or parallel are placed, one at each end of the part and a third coil surrounds the part circumferentially, thereby producing two substantially orthogonal magnetic fields.

Abstract: A method and apparatus for generating and detecting magnetization responses from ferromagnetic, ferrimagnetic, paramagnetic, or diamagnetic materials comprises a means for generating an alternating magnetic field. The cycle of the alternating magnetic field includes a first magnetization pulse and a second demagnetization pulse, the energy content of the magnetization pulse and the demagnetization pulse being approximately equal, the time duration of the magnetization pulse being substantially longer than the time period of the magnetization pulse, the demagnetization pulse having a higher magnetic field strength than the magnetization pulse magnetic field strength. The effect of the alternating magnetic field on the material to be tested is measured by magnetic field detectors. The field detectors generate electrical signals which are fed to an oscilloscope, a comparator, or a computer for analysis.

Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by using saddle coils which are positioned adjacent the magnetized sections of the elongate object and which detect variations in radial flux. The saddle coils are positioned to have first half circumferential windings located where the magnetic flux density in the elongate object is at a maximum value and second half circumferential windings located where the magnetic flux density in the object is zero.

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: This invention relates to a method and device for measuring the resistivity f materials. In particular, the methods measure resistivity in carbon fiber reinforced composites as well as any materials with a relative magnetic permeability of 1. The measurement may be made with access restricted to a single side of the material under test.

Abstract: A magnetic sensor for the collection and measurement of ferrous particles through the use of an electronic tuned circuit is disclosed. The sensor contains an electrical inductance along with an integral magnet to attract ferrous particles suspended in the fluid. The ferrous particles collecting on the magnetic surface of the sensor causes a change in the inductance of the integral coil which is measured by an electronic circuit. The electronic circuit operating in conjunction with the sensor utilizes a parallel tuned resonant circuit and time variant frequency multiplying to eliminate undesired response changes of the tuned circuit due to the temperature change of the sensor. The sensor may be located in environmental conditions which include a large variation in ambient temperature. The disclosed invention provides for compensation of such undesired changes caused by temperature change so that the actual change of the inductance in the sensor can be monitored without interference.

Abstract: There is disclosed herein a method and apparatus wherein conveyor belt cords are first de-gaussed to remove any stray magnetic fields, and then longitudinal unidirectionally magnetized. The belt is then magnetically scanned and the electrical output signal is passed through a low pass filter in order to produce a break signal indicative of breaks in the magnetically permeable cords of the conveyor belt.

Abstract: Apparatus is disclosed for locating and measuring wear in nuclear reactor control rods. Circumferential and radial eddy current test probes produce outputs corresponding respectively to volume and thickness of the control rod. A method is disclosed to determine cladding wear when the volume and thickness varies beyond preselected limits.

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 device for inspection by eddy current methods of materials exhibiting cumferential conductivity. This device finds application for the inspection of filament-wound carbon fiber reinforced composites which do not usually have sufficient conductivity in the axial direction to allow inspection by conventional surface probes while still providing the desired resolution. This device is also useful in inspecting thick-walled circumferentially conductive materials, including metal, where their thickness would require a surface probe of such diameter as to be impractical.