Apparatus and method for nondestructive evaluation of surface flaws in conductive materials
AssigneeRockwell International Corporation
InventorChristopher M. Fortunko
Life of this patent
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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.
Claims17
An apparatus for detecting a surface anomaly in an electrically conductive sample, comprising:
- a two port ferromagnetic crystal probe, including an input port and an output port;
- and
- an oscillating circuit, including a feedback loop, said ferromagnetic probe being coupled to said loop in a transmission mode through said input and output ports, whereby the precession resonance of the crystal thereby controls the frequency and level of oscillation of said oscillation circuit and eddy currents induced in the surface of the sample by the probe modulate the level and frequency of oscillation in response to a surface anomaly.
An apparatus for detecting a surface anomaly in an electrically conductive sample, comprising:
- an oscillator, including an amplifier for supplying gain to said oscillator and a feedback loop linking the input and output of said amplifier;
- a two port ferromagnetic resonator, including an input port and an output port, coupled to said loop in a transmission mode through said input and output ports;
- a variable attenuator connected within said loop to adjust the power level of said oscillator;
- an adjustable phase shifter connected within said loop for changing the total phase shift of said loop;
- and
- a sensing circuit operably connected to the output of said amplifier to monitor the resonance parameters of said oscillator.
A method for characterizing a surface anomaly in an electrically conductive sample, comprising the steps of:
- generating eddy currents within the surface of the sample by applying a microwave signal to the sample in the presence of a static magnetic field;
- utilizing the electromagnetic field generated by the eddy currents to modulate the power level and frequency of an oscillating circuit through a ferromagnetic resonator coupled to the oscillator in the transmission mode;
- measuring the power level and frequency of oscillation;
- and
- correlating the measured values to standard values to identify an anomaly within the surface of the sample.
A method for characterizing a surface anomaly in an electrically conductive sample, comprising the steps of:
- coupling a two port ferromagnetic resonator into the feedback loop of an oscillator;
- driving the resonator at microwave frequencies to generate eddy currents within the surface of the sample, the eddy currents in turn generating an electromagnetic field;
- modulating the power level and frequency of oscillation of the oscillator in accordance with the effect of the eddy current-induced electromagnetic field on the resonator;
- adjusting the attenuation and the phase shift of the feedback loop to restore the oscillation to that observed in the absence of a flaw;
- and
- correlating the attenuation and phase adjustments required for a flawed sample to those for a non-flawed sample to determine the dimensions of an anomaly within the surface of the flawed sample.
Dependencies are inferred from the claim text.