US 4,727,321 AGranted

Method and device for magnetic and ultrasonic testing of ferro-magnetic objects

AssigneeNukem GmbH

InventorGerhard Huschelrath

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Abstract

The subject of the invention is a method and a device for non-destructive testing of ferromagnetic bodies (1) for structural faults. The bodies (1) are magnetized. Structural faults cause changes in the magnetic field pattern which are measured with magnetic field detectors (6). Surface waves are generated electro-dynamically utilizing the magnetic field generated for magnetizing the body (1). Those structural faults extending up to the surface can be detected with the surface waves. To distinguish between the structural faults extending to the surface of the body at one point and those structural faults inside the body (1), it is determined whether the measured values gained both from the leakage flux and from the surface waves indicate structural faults or whether only the measured values gained from the leakage flux indicate structural faults.

Claims17

Dependent claims

A method of selectively, non-destructively testing ferromagnetic bodies for structural anomalies during a relative motion between a measuring apparatus and a respective body, in which at least one magnetic field is generated causing leakage flux in case of structural anomalies, which flux is measured by at least one magnetic field detector, and ultrasonic waves are generated making use of the magnetic field in conjunction with at least one electro-dynamic transducer, these ultrasonic waves being reflected from structural anomalies and measured by said at least one electro-dynamic transducer, characterized by the following steps,

(a) generating the ultrasonic waves as surface waves, detecting structural anomalies reaching the surface of the respective body from the measured reflected waves;
(b) distinguishing structural anomalies reaching the surface at one point on said body from structural anomalies not reaching the surface, by detecting whether both the leakage flux measurement and the surface wave measurement are indicating structural anomalies at said point, or whether the leakage flux measurement only is indicating structural anomalies, indications of structural anomalies by both measurements signifying that a structural anomaly reaching the surface exists, and
(c) upon determining that a structural anomaly reaching the surface of the body exists, determining the depth of impression of the structural anomaly from the size and/or the form of the leakage flux measured value at said point.

An apparatus for the non-destructive testing of ferro-magnetic bodies for structural anomalies during a relative motion between a measuring device and the respective body, in which, on the one hand, at least one magnetic field is generated causing leakage flux in case of structural anomalies, which flux is measured by at least one magnetic field detector, and, on the other hand, ultrasonic waves are generated, making use of the magnetic field, by means of at least one electro-dynamic transducer, these ultrasonic waves being reflected from structural anomalies and measured by said at least one electrodynamic transducer, characterized by the following features

(a) for generating the magnetic field, at least two magnets, with their pole shoes at a distance from each other, are pointed at the surface of the body to be tested;
(b) a magnetic field detector is arranged in the space between the pole shoes close to the surface of the body;
(c) at a place close to the surface of the body, where the magnetic field has field components both perpendicular to the surface and extending in the direction of the surface and parallel thereto, there is arranged the electro-dynamic transducer having a transmitting coil;
(d) the electro-dynamic transducer including a receiving coil which is connected to a first input of an interconnection logic via a threshold value detector, the magnetic field detector being connected to the input of a computerized signal processing circuit, the output of which is connected to a second input of the interconnection logic circuit, and
(e) the output of said interconnection logic being connected to a first input of a defect register, a second input of said defect register being connected to the output of said signal processing circuit such that a value from the interconnection logic or the computerized signal processing circuit can be read in said defect register in synchronism with test timing pulses generated in the transmitting coil of the electro-dynamic transducer, the output of said interconnection logic providing an indication of whether an anomaly is an internal or an external anomaly, and the output of said signal processing circuit providing an indication of the depth of said anomaly

2 more elements

Dependencies are inferred from the claim text.