Rockwell International Corporation

USA As Represented by Secretary of the Navy

Electric Power Research Institute Incorporated

Christopher M Fortunko

Robert B Thompson

Carmine F Vasile

Herbert J Shaw

Jacques Souquet

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.

Apparatus and method for nondestructive evaluation of surface flaws in

Disclosed is a method for generating an ultrasonic wave in a material, utilizing a transducer adapted to induce a higher than fundamental mode wave in the material and a signal generator adapted to drive the transducer at a frequency above the cutoff frequency below which the higher mode wave will not propagate. For a horizontal shear wave, optimal transducer efficiency is obtained by selecting a driven frequency between a minimum cutoff frequency f.sub.c =v.sub.s n/2t and an upper frequency sufficiently close to f.sub.c to drive the transducer with at least a preselected increase in efficiency.

Method and apparatus for efficiently generating elastic waves with a

Disclosed is an electromagnetic acoustic transducer for generating and detecting an elliptically polarized ultrasonic wave in an electrically conductive material. The transducer includes a row of uniformly sized, adjacent, alternately oriented permanent magnets, which establish a periodic magnetic field. Coaxially wound around the row is a first coil for inducing an alternating current perpendicular to the field and perpendicular to the periodic direction, while a second coil is wound around the coil orthogonal to the first coil to induce an alternating current perpendicular to the field and parallel to the periodic direction. An ultrasonic ellipsometer includes such a dual coil transmitting transducer for generating an elliptically polarized wave and a dual coil receiving transducer for detecting the wave after it has propagated through an electrically conductive medium. By using the ellipsometer to generate an elliptically polarized wave in a material and detect the change in polarization of the wave after propagating through the material, the apparatus can be employed to examine surface properties of the material.

Ultrasonic ellipsometer

A method and an apparatus are provided for ultrasonically inspecting a cylindrical object. The object is placed between the poles of a magnet to create a circumferential magnetic field in the object. A group of electromagnetic transducers (EMAT's) are placed adjacent the material so that the transducers scan the entire object when it is rotated. When an RF signal is applied to the transducers, elastic waves are generated in the material. These elastic waves reflect from defects in the material and these reflections are received by the transducers.

Ultrasonic inspection of a cylindrical object

A surface acoustic wave bridge for rotation measurement which uses acoustic waves propagated in opposite directions about the circumference of a rotor. The acoustic waves are generated by a transducer adjacent the rotor which is excited by an rf electric field. Clockwise and counterclockwise waves in the surface of the rotor interfere with each other adjacent the transducer to form a bridge system which produces a null when the waves are out of phase. The rf frequency of the electric field is varied to obtain the null and, thus, is a measurement of the rotation rate of the rotor. For the measurement of slow rotation rates two transducers are used to generate the counterrotating acoustic waves in a helical pattern such that the acoustic wave generated by one transducer is received by the other. The outputs of the transducers are detected and provide an approximately linear measurement of slow rotational rates.

Growing community of inventors

Thousand Oaks, CA, United States of America

Christopher M Fortunko