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 Title: |
US6218846:
Multi-probe impedance measurement system and method for detection of flaws in conductive articles
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Ludwig, Reinhold; Worcester, MA
McNeill, John A.; Stow, MA
Stander, Jennifer A.; Boylston, MA
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| Assignee: |
Worcester Polytechnic Institute, Worcester, MA
other patents from WORCESTER POLYTECHNIC INSTITUTE (633135) (approx. 25)
News, Profiles, Stocks and More about this company
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| Published / Filed: |
2001-04-17
/ 1997-08-01
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| Application Number: |
US1997000904789
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| IPC Code: |
Advanced:
G01R 1/073;
G01R 31/28;
Core:
more...
IPC-7:
G01R 27/00;
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| ECLA Code: |
G01R1/073B4; G01R31/28B5B;
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| U.S. Class: |
Current:
324/713;
324/715;
324/718;
Original:
324/713;
324/715;
324/718;
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| Field of Search: |
324/713,715,718,722,724
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| Priority Number: |
| 1997-08-01 |
US1997000904789 |
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| Abstract: |
An innovative multi-dimensional, low frequency, impedance measurement probe array, measurement system, and method are disclosed for detecting flaws in conductive articles. The device and method provide for contacting a conductive article with an multi-probe array of current and voltage probes, injecting current sequentially through a plurality of current probe pairs and measuring absolute or relative voltages with a plurality of voltage probes and voltage probe pairs across the surface of an article for each current flow condition. The device and method further provide for constructing a voltage profile across the surface of an article where disruptions in the voltage profile enable detection of the presence, location and orientation of flaws for flaw sizes as low as 20 um. The innovative probe array and method provide for rapidly detecting cracks, inclusions, defects and other flaws in conductive articles and can be adapted and deployed as either a two-dimensional, planar array or three-dimensional shaped array for a variety of sample configurations and surfaces. By utilizing a plurality of current and voltage probes in an array format, the device and method overcomes existing limitations of conventional linear probes and traditional methods by enabling flaw detection over larger areas in a single probe placement while achieving a high degree of sensitivity and precision in determining flaw location and orientation.
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| Attorney, Agent or Firm: |
Creehan, R. Dennis ;
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| Primary / Asst. Examiners: |
Ballato, Josie; Sundaram, T. R.
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| Maintenance Status: |
R2 Reinstated
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| INPADOC Legal Status: |
Show legal status actions
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| Family: |
None
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First Claim:
Show all 33 claims |
What is claimed is:
1. A method for detecting flaws in a conductive article comprising:
- contacting a surface of said article with a non-linear array of probes comprising at least three voltage probes and at least three current probes;
- selecting predetermined pairs of said current probes;
- selecting predetermined pairs of said voltage probes;
- passing current through said article by means of each of said predetermined pairs of said current probes, said current passing sequentially through each of said current probe pairs, one pair at a time, at varying directions to said voltage probes;
- measuring voltage produced by each of said currents at predetermined locations on a surface of said article, said voltage measured between each of said pairs of said voltage probes for each current flow condition; and
- detecting the presence, location, size and orientation of flaws in said article, wherein the presence of said flaws in said article creates a detectable and statistically significant disturbance in a voltage profile generated from said voltages measured over said surface of said article, said disturbances indicative of the location, size, depth and orientation of said flaws.
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| Background / Summary: |
Show background / summary
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| Drawing Descriptions: |
Show drawing descriptions
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| Description: |
Show description
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| Forward References: |
Show 11 U.S. patent(s) that reference this one
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| Foreign References: |
None
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| Other References: |
Anonymous, "AT&T Microhmeter User Guide", AT&T Product Manual, Feb. 1986.
A.D. Seagar, et al., "Theorectical limits to sensitivity and resolustion in impedance imaging", Clin.Phys.Physiol.Meas., 1987, vol. 8, Suppl. A, p.13-31.
B.H.Brown, et al., "The Sheffield data collection system", Clin.Phys.Physiol.Meas., 1987, vol. 8, Suppl. A, p.91-97.
H.M.Powell, et al., "Impedance imaging using linear electrode arrays", Clin.Phys.Physiol.Meas., 1987, vol. 8, Suppl. A, p.109-118.
K. Ikeda, et al., "Electrical potential drop method for evaluatig crack depth", International Journal of Fracture 47:25-38, 1991.
(14 pages)
[ISI abstract]
P.R.Frise, et al., "Improved Probe Array for ACPD Crack Measurements", British Journal of NDT, vol. 34, No. 1, Jan. 1992, p.15-19.
(5 pages)
[ISI abstract]
Barend Van Den Bos, "The DC Potential Drop Method for Non Destructive Testing of P/M Components in Green and Sintered State", Jernkontorets Forskning, Final Report, Project No. 8076/92, Serie D (T080-37), Nr 750, Jun. 28, 1996.
R.L.Cohen, et al., "Characterization of Metals and Alloys by Electrical Resistivity Measurements", Materials Evaluation/ 41/ Aug. 1983, p. 1074-1077.
(4 pages)
Cited by 2 patents
Leander F. Pease III, Flaw Detection in P/M Parts via Real Time X-Ray Analysis, Eddy Currents, and Electrical Resistivity, 1988 Int. Powder Metallurgy Conf., MPIF (Princeton, NJ, 1988) p. 105-125.
Anna Lewis, et al., "Resistivity Measurement for Evaluation of Coating Thickness", Materials Evaluation / Feb. 1991, p. 132-135.
(4 pages)
[ISI abstract]
Leander F. Pease III, "Crack Detection in Green and Sintered P/M Parts", 1992 Powder Metallurgy World Congress, San Francisco, CA, Jun. 21-26, 1992, p. 1-24.
Duane P. Johnson, et al., "Nondestructive Flaw Detection and Density Measurements in Powder Metallurgy Parts", Advances in P/M and Particulate Materials, vol. 2, MPIF (Princeton, NJ, 1992) p. 281-289.
R.E. Shannon, et al., "Nondesctructive Evaluation for Large-Scale Metal-Matrix Composite Billet Processing", Metallurgical Transactions A, vol. 23A, May 1992, p. 1541-1549.
(9 pages)
[ISI abstract]
Duane P. Johnson, "Nondestructive Flaw Detection and Density Measurements in Powder Metallurgy Parts--Part II", Industrial Heating / Aug. 1996, p. 41-45.
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