초록 ▼

A method for the detection and the characterization of corrosion in multi-layer metallic structures using a pulsed eddy current technique. For this technique, a coil (or coils) is used both as field source (driven by a square wave voltage-controlled excitation), and/or as field sensor (measuring a t

A method for the detection and the characterization of corrosion in multi-layer metallic structures using a pulsed eddy current technique. For this technique, a coil (or coils) is used both as field source (driven by a square wave voltage-controlled excitation), and/or as field sensor (measuring a transient response). The field sensor allows the capture of information about the condition of the area of the structure under inspection. The ability of this technique to detect corrosion hinges on the use of a transient response feature (i.e., Lift-off Point of Intersection) to infer the presence of material loss. With the help of a calibration standard, the Lift-off Point of Intersection provides the ability to quantify material loss in multi-layered structures. The results obtained with this method are independent of lift-off variations inherent to field inspections (i.e., changes in distance between the transducer and test object).

대표청구항 ▼

1. A method for detecting defects in a metallic structure, the method comprising locating a transducer at a first distance from said metal structure at one area that lacks any significant defects in the structure, activating said transducer with a square wave voltage-controlled excitation to generat

1. A method for detecting defects in a metallic structure, the method comprising locating a transducer at a first distance from said metal structure at one area that lacks any significant defects in the structure, activating said transducer with a square wave voltage-controlled excitation to generate eddy currents in the structure and then sensing, with at least one magnetic flux sensor, time-varying magnetic fields generated by the transducer and said eddy currents, signals obtained from said at least one sensor being recorded, this process being repeated to obtain at least one other recorded signal that is obtained with the transducer being located in the same location but at a different lift-off distance from said one area, determining where the recorded signals cross to establish a Lift-off Point of Intersection at a point in time, placing said transducer at other areas of said structure which are to be tested for defects, activating said transducer with similar voltage-controlled excitation as applied at said one area, then obtaining and recording signals sensed from the time-varying magnetic fields generated by the transducer and eddy currents in a similar manner as at said one area, comparing the recorded signals amplitudes which are obtained at said other areas at said point in time with those of signals obtained at said one area wherein differences in signal amplitude provides indications of any defects present and a quantitative evaluation of such defects at areas being tested.