Abstract: A method and apparatus for inserting an eddy current hole probe into a hole specimen and automatically moving the probe in two orthogonal (X, Y) directions in response to the impedance change of an eddy current coil located in the probe as a function of distance from the surface of the hole. The probe is centered in the hole by a system controller which operates to minimize the composite deviation value of the coil impedance. The diameter of the hole is then determined from the average impedance measurement. Following this, a plot of the hole eccentricity is generated by determining the impedance deviation from the average coil impedance value as a function of the angular rotation of the probe in the hole. Measurements of the hole eccentricity for a plurality of hole depths provides an indication of the hole eccentricity profile.

Abstract: A method and apparatus for inserting and moving a sensing assembly with a mechanical positioning assembly to a desired remote location of a surface of a specimen under test and measuring angle and/or deflection by sensing the change in the impedance of at least one sensor coil located in a base plate which has a rotatable conductive plate pivotally mounted thereon so as to uncover the sensor coil(s) whose impedance changes as a function of deflection away from the center line of the base plate in response to the movement of the rotator plate when contacting the surface of the specimen under test. The apparatus includes the combination of a system controller, a sensing assembly, an eddy current impedance measuring apparatus, and a mechanical positioning assembly driven by the impedance measuring apparatus to position the sensing assembly at a desired location of the specimen.

Abstract: A device for the determination of residual stress in a material sample consisting of a sensor coil, adjacent the material sample, whose resistance varies according to the amount of stress within the material sample, a mechanical push-pull machine for imparting a gradually increasing compressional and tensional force on the material sample, and an impedance gain/phase analyzer and PC for sending an input signal to and receiving an input signal from the sensor coil. The PC will measure and record the change in resistance of the sensor coil and the corresponding amount of strain of the sample. The PC will then determine from the measurements of change of resistance and corresponding strain of the sample the point at which the resistance of the sensor coil is at a minimum and the corresponding value and type of strain of the sample at that minimum resistance point thereby enabling a calculation of the residual stress in the sample.

Abstract: An improved NDE method utilizes a laser source with modulator and scanning mirror, a pancake shape eddy current detecting coil, a lock-in amplifier, a system controller, and an impedance gain/phase analyzer. The laser is directed by the scanning mirror to a specimen to be analyzed. A very localized or small area of the specimen is impacted directly by the laser beam creating a thermal and stress wave in the specimen. An impedance gain/phase analyzer is connected to the eddy current detecting coil and to a lock-in amplifier through the system controller. The lock-in amplifier is also synchronized to the laser modulator. The system controller is used to control the lock-in amplifier, scanning mirror, and to process data from the analyzer. Raster scanning of the laser beam across the speciment allows the detection by the coil of the laser generated thermal and elastic strains induced in the specimen by the laser. The rastering of the laser beam is controlled by the controller by positioning the mirror.

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.