Transducer guided wave electromagnetic acoustic
First Claim
1. A guided wave electromagnetic acoustic transducer for detection of defects and/or or variances in the physical properties of metallic products including rods, wires, bars and tubes, all having a central axis, transmitting and detecting acoustic waves in these products, said transducer comprisinga housing means, electromagnetic means within said housing for establishing a static magnetic field in said metallic products being inspected, electrical conductors for wrapping around said metallic products to encircle the same for producing eddy currents in said products, said conductors being energized by a pulse of a few cycles of high frequency alternating voltage which produces an alternating field in said metallic products, which, in turn, produces eddy currents which flow around the circumference of the section of the metallic product being tested, and means for inducing said eddy currents in said electrical conductor to produce, by the interaction of said eddy currents and said static magnetic field, Lamb waves which propagate along said metallic products in two directions, and means for detection of said Lamb waves to allow said transducer to detect any defects or variances.
0 Assignments
0 Petitions
Accused Products
Abstract
A guided wave electromagnetic acoustic transducer for detecting defects in moving metallic products such as rods, tubes and the like and which has coils energized by pulse of a few cycles of a high frequency alternating voltage which produces an alternating field in the product, the coils being alternately wound and connected in series and measuring dynamic acoustic stress that is a function of the radial distance from the center of the product being tested and produces a reading that is different than that showing a surface defect in the product.
-
Citations
36 Claims
-
1. A guided wave electromagnetic acoustic transducer for detection of defects and/or or variances in the physical properties of metallic products including rods, wires, bars and tubes, all having a central axis, transmitting and detecting acoustic waves in these products, said transducer comprising
a housing means, electromagnetic means within said housing for establishing a static magnetic field in said metallic products being inspected, electrical conductors for wrapping around said metallic products to encircle the same for producing eddy currents in said products, said conductors being energized by a pulse of a few cycles of high frequency alternating voltage which produces an alternating field in said metallic products, which, in turn, produces eddy currents which flow around the circumference of the section of the metallic product being tested, and means for inducing said eddy currents in said electrical conductor to produce, by the interaction of said eddy currents and said static magnetic field, Lamb waves which propagate along said metallic products in two directions, and means for detection of said Lamb waves to allow said transducer to detect any defects or variances.
-
11. A guided wave electromagnetic acoustic transducer for providing transmittal and receiving of acoustic waves to detect variations and/or defects in metallic products with a central axis, said transducer including
at least one segmented magnet for movement to and away from the central axis of such a product so as to allow said magnet to closely encircle said product regardless of the diameter of said product and a set of coil means connected in series so that induced voltages are added to provide maximum signals for detection.
-
14. A guided wave electromagnetic acoustic transducer for providing transmittal and receiving of acoustic waves to detect variations and/or defects in metallic products with a central axis, said transducer including
at least one coil flexibly mounted so as to adapt to the diameter of said products by either moving toward or away from the axis of said product to encircle said product about its diameter, said coils having alternate windings so as to detect Lamb waves measuring the dynamic acoustic stress in said products that is a function of the radial distance from the center of said metallic product therefore producing a reading that interprets reflected waves from a surface defect as smaller than those waves reflected from the center of the metallic product.
-
16. An EMAT to detect defects both along the surface and at the center of various metallic products including rods, tubes, wires and bars, all having a central axis, by transmitting acoustic waves in these products, said EMAT comprising,
housing means means to generate a static magnetic field in said products, means to generate eddy currents in said products to generate, in conjunction with said static magnetic field, Lamb waves along the length of said products, and means to detect said Lamb waves to ascertain the existence of defects either along the surface or in the center of said products, said means for detecting said Lamb waves measuring the dynamic acoustic stress that is a function of the radial distance from the center of the metallic product thus producing a reading that interprets reflected waves from surface defects as smaller than reflected waves from the center of said products.
-
32. The method of detecting defects in metallic products including pipes, rods, bars and wires, said method comprising,
providing a static magnetic field along said metallic product, providing excitation by a pulse of a few cycles of high frequency alternating voltage to produce an alternating field in said product, to provide eddy currents along the length of said product and around the circumference of said product to interact with said static magnet field to produce Lorentz forces, monitoring the Lamb waves created by the interaction and reflection off of defects along the length of said product so as to locate the defect by signal strength.
-
36. A hinged EMAT for testing for defects along the length of installed wires, bars, rods, or tubing and other metallic products where the product is already installed and cannot be removed, said EMAT including:
-
a hinged permanent magnet adapted to open and close around a length of said product and produce a magnetic field therealong, and coil means along the surface of said magnet which encircles said product so as to provide eddy currents to interact with said magnetic field so as to produce measurable Lamb waves for detection of defects in said product, and said permanent magnet surrounding said coil means and including two pole pieces which protect said coil means from wear and guide the EMAT along the metallic product.
-
Specification