Combined leakage field and eddy current flaw detector

Claim 2

A pickup probe for scanning the surface of a magnetized workpiece and measuring stray fields adjacent said surface in the region of discontinuities in the workpiece and measuring magnetic fields reradiated from eddy currents in said surface, said probe including the combination of a magnetic core, first means on said core for inducing said eddy currents in the surface of said workpiece, second means on said core for inducing a magnetic field within said core which combines with the stray field and the reradiated field to form a resultant field in the core, and third means on said core coupled to said resultant field to produce a corresponding electrical signal.

Claim 3

The pickup probe of claim 1 wherein said first means includes a primary winding for creating a magnetic field in said core which extends into the workpiece and creates said eddy currents, said core is adapted to be disposed adjacent the workpiece to receive the magnetic fields reradiated by the eddy currents, and said third means is responsive to said received fields whereby said electric signal has a portion which is a function of the eddy currents.

Claim 4

The pickup probe of claim 1 wherein said core is adapted to be disposed adjacent the workpiece whereby at least a portion of the stray field is coupled in said core, said second means includes a primary winding for inducing the magnetic field in said core, said induced field combining with the portion of the stray field in said core to form a resultant field, Said third means is responsive to the resultant field and is effective to produce a signal which includes a portion that is a function of the stray field.

Claim 5

The nondestructive testing system of claim 12 wherein said source of alternating driving signal is operative to create said eddy currents during certain intervals whereby said first part of said signal corresponding to the eddy currents occurs during said certain intervals and the second part of said signal corresponding to the stray fields occurs during other intervals.

Claim 6

The pickup probe of claim 1 wherein said first means includes a primary winding for creating a magnetic field in said core which extends into the workpiece and creates eddy currents, said core is adapted to be disposed adjacent the workpiece whereby at least a portion of the magnetic fields reradiated by the eddy currents extend into said core and at least a portion of the stray fields extend into said core, said second means includes a primary winding for inducing a magnetic field in said core, said induced field combining with the portion of the stray field in said core to form a resultant field, said third means is responsive to the reradiated field and the resultant field and is effective to produce a signal having a first portion which is a function of the eddy currents and a portion that is a function of the stray field.

Claim 7

A pickup probe for scanning the surface of a magnetized workpiece and measuring the stray fields adjacent the surface in the region of discontinuities in the workpiece and measuring the magnetic fields reradiated by the eddy currents in said surface, said probe including the combination of a core of magnetic material, a first primary coupled to said core and adapted to be connected to a source of an alternating driving signal whereby the core radiates an alternating field into the workpiece and induces eddy currents in said surface, said core being adapted to receive at least a portion of the magnetic stray fields adjacent the surface and also receive at least a portion of the magnetic fields reradiated by the eddy currents, a second primary coupled to said core for circulating a magnetic field in the core for combining with the portion of the stray field therein to create a resultant field, and a secondary on said core and coupled to the fields therein, said secondary being responsive to the resultant field and to the portion of the reradiated field in the core to produce a signal having a first part which is a function of the stray fields and a second part which is a function of the eddy currents.

Claim 8

A pickup probe for scanning the surface of a magnetized workpiece and measuring the stray fields adjacent the surface in the region of discontinuities in the workpiece and measuring the magnetic fields reradiated by the eddy currents in said surface, said probe including the combination of a core of magnetic material, a first primary coupled to said core and adapted to be connected to a source of an alternating driving signal whereby the core radiates an alternating field into the workpiece and induces eddy currents in said surface, said core being adapted to receive at least a portion of the magnetic stray fields adjacent the surface and also receive at least a portion of the magnetic fields reradiated by the eddy currents, a second primary coupled to said core for circulating a magnetic field in the core for combining with the portion of the stray field therein to create a resultant field, and a secondary on said core and coupled to the fields therein, said secondary being responsive to the resultant field and to the portion of the reradiated field in the core to produce a signal having a first part which is a function of the stray fields and a second part which is a function of the eddy currents.

Claim 9

The pickup probe of claim 5 wherein the core is an annular ring.

Claim 10

The pickup probe of claim 6 wherein the first primary is a winding which extends around the diametrically opposite sides of the ring and produces an alternating magnetic field which extends beyond the core, said core being adapted to be positioned adjacent the workpiece whereby said field extends into the workpiece and creates eddy currents and the fields reradiated by the currents extend into the core.

Claim 11

The pickup probe of claim 6 wherein the second primary is a winding which extends around one side of the ring and produces an annular flux field within the core, and said core being effective to receive at least a portion of stray field whereby the annular field and received portion of the stray field combine in the opposite sides of the core to form resultant fields within said core.

Claim 12

In a device of the class described for scanning the surface of a magnetized workpiece and measuring the stray magnetic fields adjacent said surface in the region of discontinuities in the workpiece and the magnetic fields reradiated by the eddy currents on said surface, said device including the combination of an annular core of magnetic material adapted to scan across the surface of the workpiece, a first primary winding on said core effective to create a magnetic flux field in said core which extends into the workpiece, a second primary winding on said core to produce an annular magnetic flux field within the core, a source of driving signals, means effective to intermittently couple said source to the first primary winding whereby said first primary winding is effective to radiate the magnetic field into the workpiece and induce eddy currents in the workpiece said means being effective to intermittently couple said source to the second primary winding whereby the annular field from the second primary produces a resultant field in the annular core, and a secondary winding on the core and coupled to the magnetic fields therein to produce a signal having a first part which corresponds to the eddy currents and a second part which corresponds to the stray fields.

Claim 13

In a device of the class described for scanning the surface of a magnetized workpiece and measuring the stray magnetic fields adjacent said surface in the region of discontinuities in the workpiece and the magnetic fields reradiated by the eddy currents on said surface, said device including the combination of an annular core of magnetic material adapted to scan across the surface of the workpiece, a first primary winding on said core effective to create a magnetic flux field in said core which extends into the workpiece, a second primary winding on said core to produce an annular magnetic flux field within the core, a source of driving signals, means effective to intermittently couple said source to the first primary winding whereby said first primary winding is effective to radiate the magnetic field into the workpiece and induce eddy currents in the workpiece said means being effective to intermittently couple said source to the second primary winding whereby the annular field from the second primary produces a resultant field in the annular core, and a secondary winding on the core and coupled to the magnetic fields therein to produce a signal having a first part which corresponds to the eddy currents and a second part which corresponds to the stray fields.

Claim 14

The combination of claim 9 including means for magnetizing said workpiece to produce stray fields adjacent the surface of the workpiece.

Claim 15

The combination of claim 9 including means responsive to said signal to indicate the characteristics of said workpiece.

Claim 16

A nondestructive testing system for detecting discontinuities in a workpiece, said system including the combination of means for magnetizing the workpiece whereby stray fields are produced above the surface of the workpiece in the region of discontinuities in the workpiece, a ring core of magnetic material, a first primary winding on said core, a source of alternating driving signals connected to said primary winding to produce an alternating magnetic field, said primary winding being diametrically wound around said core whereby said alternating magnetic fields extends diametrically across said core and into the workpiece so as to induce eddy currents in said surface, said core being adapted to receive at least a portion of the magnetic field reradiated by said eddy currents and at least a portion of the magnetic stray fields, a second primary winding coupled to said core for circulating an annular magnetic field extending circumferentially around the core and combining with the stray fields in said opposite sides thereof to create resultant fields in said opposite sides, a secondary winding wound diametrically around said core and coupled to the difference between said resultant fields whereby said secondary winding produces an electrical signal having a first part corresponding to the eddy currents and a second part corresponding to the stray fields.

Claim 17

A nondestructive testing system for detecting discontinuities in a workpiece, said system including the combination of means for magnetizing the workpiece whereby stray fields are produced above the surface of the workpiece in the region of discontinuities in the workpiece, a ring core of magnetic material, a first primary winding on said core, a source of alternating driving signals connected to said primary winding to produce an alternating magnetic field, said primary winding being diametrically wound around said core whereby said alternating magnetic fields extends diametrically across said core and into the workpiece so as to induce eddy currents in said surface, said core being adapted to receive at least a portion of the magnetic field reradiated by said eddy currents and at least a portion of the magnetic stray fields, a second primary winding coupled to said core for circulating an annular magnetic field extending circumferentially around the core and combining with the stray fields in said opposite sides thereof to create resultant fields in said opposite sides, a secondary winding wound diametrically around said core and coupled to the difference between said resultant fields whereby said secondary winding produces an electrical signal having a first part corresponding to the eddy currents and a second part corresponding to the stray fields.

Claim 18

The nondestructive testing system of claim 13 including output means having a first portion responsive during said certain intervals to the first part of said signal and a second portion responsive during said other intervals to the second part of said signal.

Claim 19

A pickup probe for use in a nondestructive testing system for inspecting a workpiece having stray fields above the surface thereof in the region of discontinuities, said pickup probe including the combination of a ring core of magnetic material adapted to scan across the surface of the workpiece, a first primary winding on said core adapted to be connected to a source of driving signals, said winding being wound diametrically around said ring core whereby the magnetic flux field created by said driving signals extend diametrically through said core and into the workpiece to create eddy currents on the surface thereof, a second primary winding on said core adapted to be connected to a signal source, said second primary winding being effective to produce an annular magnetic flux field within the core, the magnetic field reradiated by said eddy current and said stray field extending through said core and forming resultant fields in the opposite sides of said ring core, and a secondary winding on said core disposed diametrically thereof and coupled to said resultant fields, said secondary winding being effective to produce a signal having a first part corresponding to the eddy currents and a seconD part corresponding to the stray fields.

Claim 20

A pickup probe for use in a nondestructive testing system for inspecting a workpiece having stray fields above the surface thereof in the region of discontinuities, said pickup probe including the combination of a ring core of magnetic material adapted to scan across the surface of the workpiece, a first primary winding on said core adapted to be connected to a source of driving signals, said winding being wound diametrically around said ring core whereby the magnetic flux field created by said driving signals extend diametrically through said core and into the workpiece to create eddy currents on the surface thereof, a second primary winding on said core adapted to be connected to a signal source, said second primary winding being effective to produce an annular magnetic flux field within the core, the magnetic field reradiated by said eddy current and said stray field extending through said core and forming resultant fields in the opposite sides of said ring core, and a secondary winding on said core disposed diametrically thereof and coupled to said resultant fields, said secondary winding being effective to produce a signal having a first part corresponding to the eddy currents and a seconD part corresponding to the stray fields.