EP1032829A1 - A testing method for machined workpieces - Google Patents
A testing method for machined workpiecesInfo
- Publication number
- EP1032829A1 EP1032829A1 EP97952139A EP97952139A EP1032829A1 EP 1032829 A1 EP1032829 A1 EP 1032829A1 EP 97952139 A EP97952139 A EP 97952139A EP 97952139 A EP97952139 A EP 97952139A EP 1032829 A1 EP1032829 A1 EP 1032829A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- determination
- machined workpieces
- probe
- absolute
- eddy current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000012360 testing method Methods 0.000 title abstract description 7
- 239000000523 sample Substances 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 13
- 230000001627 detrimental effect Effects 0.000 claims abstract description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 239000000956 alloy Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 8
- 238000003754 machining Methods 0.000 description 5
- 230000015556 catabolic process Effects 0.000 description 3
- 238000007689 inspection Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000000254 damaging effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229910000601 superalloy Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
Definitions
- the present invention refers to a method for determination of the presence, if any, of detrimental surface changes, such as increased hardness or residual stress in machined workpieces.
- Another possibility is to try to find cracks in the material, if any, by means of a fluorescent penetrating liquid.
- the machining damages which might be present do not always cause cracks to occur until the part has been loaded and normally this does not occur during the production but only later in service.
- a third frequent inspection method is eddy current testing with a differential probe. In carrying out this test two coils are used and the signal difference between the coils is observed. Said method is also well suited for localising cracks while long-term changes in the materials such as the machining damages aimed at in the present case, may fade away.
- a supplementary checking method over the blue-etch-, the differential probe and the penetration methods would be highly desirable in order to provide for an establishment with certainty whether there are machining damages present due to local over-heating by worn tools, tool breakdown or the like.
- the absolute probe used in connection with the present invention is of simplest possible design. More closely, it has the shape of a body with a cross section adapted to the geometry of the inspected surface and a coil wound around said body. This design makes the probe sensitive to everything having influence on the electrical conductivity or magnetic permeability of the material tested. It is also sensitive to everything which changes the relationship between the surface of the material and the probe. The result thereof is that also minor material changes might be measured such as changes in residual stress, dissolved foreign atoms in small percentages as well as composition variations etc.
- the probe according to the invention is connected to an eddy current instrument and introduced with a uniform speed through the hole in a workpiece which is to be investigated.
- the signal from the instrument is digitalized and stored in e.g. a PC. Measuring data are then treated in order to facilitate the evaluation.
- the cylindrical probe body preferably is made of plastic and has a sufficient length for allowing a simple attachment for automatic measuring.
- the diameter is adapted such that the probe guides itself through the hole .
- the inventive absolute probe also makes it possible to identify surfaces of the workpiece which have been damaged in the manufacture, where the damaging action is very small.
- testing might be automized and the inspection time will be short compared to other testing techniques.
- the evaluation can be automized and measuring data might be stored for being traced and evaluated later.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
The invention refers to a method for determination of the presence, if any, of detrimental surface changes, such as increased hardness or residual stress in machined workpieces. For achieving a very reliable test result, the invention suggests that the determination is made with the aid of an eddy current probe of absolute-type.
Description
A testing method for machined workpieces
The present invention refers to a method for determination of the presence, if any, of detrimental surface changes, such as increased hardness or residual stress in machined workpieces.
For such checking of the presence of machining damages, if any, in rotary parts of aircraft engines, various methods and equipments have been used since long. When it comes to parts made of titanium there has been carried out a so- called blue-etch of the surface of the material for checking machined surfaces. There are, however, two problems in connection with this method when inspecting, namely on one hand that this method is a visually-based one, which requires that one can view the surface satisfactorily (and preferably at right angles) , which causes difficulties in connection with deep holes but does not constitute an obstacle to the inspection of the hole edges including a portion of the hole wall closely ajacent to the edge, and on the other hand that there is a risk that the method is not perfectly reliable when foreign substances might be present in the surface. This might be the case e.g. in connection with a tool breakdown where substances from the tool such as Si, Cr, Ni and Fe or from the environment (oxygen etc) can diffuse into the matrix.
Another possibility is to try to find cracks in the material, if any, by means of a fluorescent penetrating liquid. However, the machining damages which might be present, do not always cause cracks to occur until the part has been loaded and normally this does not occur during the production but only later in service.
A third frequent inspection method is eddy current testing with a differential probe. In carrying out this test two coils are used and the signal difference between the coils is observed. Said method is also well suited for localising cracks while long-term changes in the materials such as the machining damages aimed at in the present case, may fade away.
A supplementary checking method over the blue-etch-, the differential probe and the penetration methods would be highly desirable in order to provide for an establishment with certainty whether there are machining damages present due to local over-heating by worn tools, tool breakdown or the like.
According to the present invention it has been found that the use of an absolute-probe optimized for the present use, implies a very effective possibility to investigate holes made in workpieces of titanium and its alloys, super- alloys and steel for applications in rotary aircraft parts. Should there occur a detrimental heating action of the material during the machining as a consequence of e.g. worn or damaged tools, it is easy to discover with such a probe residual stresses, diffused impurities or composition variations or a more or less heavy deformation of the surface microstructure . The invention will be further described below with reference to the accompanying drawing, in which Fig. 1 discloses a diagrammatical and partly sectioned side elevational view of an absolute probe used according to the invention and introduced into a hole, while Fig. 2 discloses two examples of various microstructures of titanium material .
As is evident from Fig. 1 the absolute probe used in connection with the present invention is of simplest possible design. More closely, it has the shape of a body with a cross section adapted to the geometry of the inspected surface and a coil wound around said body. This design makes the probe sensitive to everything having influence on the electrical conductivity or magnetic permeability of the material tested. It is also sensitive to everything which changes the relationship between the surface of the material and the probe. The result thereof is that also minor material changes might be measured such as changes in residual stress, dissolved foreign atoms in small percentages as well as composition variations etc.
The probe according to the invention is connected to an eddy current instrument and introduced with a uniform speed through the hole in a workpiece which is to be investigated. The signal from the instrument is digitalized and stored in e.g. a PC. Measuring data are then treated in order to facilitate the evaluation. It might also be added that the cylindrical probe body preferably is made of plastic and has a sufficient length for allowing a simple attachment for automatic measuring. The diameter is adapted such that the probe guides itself through the hole . In experiments with the inventive probe there have been found damages which exhibit both a heavily deformed zone and a layer having increased percentages of i.a. iron and oxygen. The hardness in the area has been increased and cracks have occured in parts having been in service. Should said cracks not be discovered in routine maintenance they might propagate sufficiently to cause a breakdown. The
inventive absolute probe also makes it possible to identify surfaces of the workpiece which have been damaged in the manufacture, where the damaging action is very small.
Furthermore, the testing might be automized and the inspection time will be short compared to other testing techniques. The evaluation can be automized and measuring data might be stored for being traced and evaluated later.
Claims
C l a i m
1. A method for determination of the presence, if any, of detrimental surface changes, such as increased hardness or residual stress in machined workpieces, c h a r a c t e r i z e d i n that the determination is made with the aid of an eddy current probe of absolute-type .
AMENDED CLAIMS
[received by the International Bureau on 12 March 1999 (12.03.99); original claim 1 replaced by amended claim 1 (1 page)]
A method for determination of the presence, if any, of detrimental surface changes, such as increased hardness or residual stress, in machined workpieces of titanium and its alloys, c h a r a c t e r i z e d i n that the deter- mination is made with the aid of an eddy current probe of absolute-type .
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/SE1997/001967 WO1999027358A1 (en) | 1997-11-21 | 1997-11-21 | A testing method for machined workpieces |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1032829A1 true EP1032829A1 (en) | 2000-09-06 |
Family
ID=20407090
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97952139A Withdrawn EP1032829A1 (en) | 1997-11-21 | 1997-11-21 | A testing method for machined workpieces |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1032829A1 (en) |
| JP (1) | JP2001524669A (en) |
| CA (1) | CA2310467A1 (en) |
| WO (1) | WO1999027358A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102008052983A1 (en) | 2008-10-23 | 2010-04-29 | Mtu Aero Engines Gmbh | Eddy current sensor and method for determining due to thermal influences modified material properties in a component to be examined by means of the same |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4303885A (en) * | 1979-06-18 | 1981-12-01 | Electric Power Research Institute, Inc. | Digitally controlled multifrequency eddy current test apparatus and method |
| EP0033802B1 (en) * | 1979-12-07 | 1984-08-08 | Thorburn Technics (International) Limited | Eddy current inspection apparatus and probe |
| CA1158314A (en) * | 1980-08-18 | 1983-12-06 | Majesty (Her) In Right Of Canada As Represented By Atomic Energy Of Cana Da Limited | Eddy current surface probe |
| JPS6166958A (en) * | 1984-09-10 | 1986-04-05 | Sumitomo Light Metal Ind Ltd | Absolute value type eddy current flaw detecting device |
| GB2233763B (en) * | 1989-07-07 | 1994-06-15 | Univ Essex | Non-destructive testing of metals |
| US5068608A (en) * | 1989-10-30 | 1991-11-26 | Westinghouse Electric Corp. | Multiple coil eddy current probe system and method for determining the length of a discontinuity |
| US5698977A (en) * | 1993-10-12 | 1997-12-16 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Eddy current method for fatigue testing |
| DE4412042C2 (en) * | 1994-04-08 | 2001-02-22 | Juergen Rohmann | Method and device for eddy current testing of bolt holes in multilayer metallic structures |
-
1997
- 1997-11-21 EP EP97952139A patent/EP1032829A1/en not_active Withdrawn
- 1997-11-21 CA CA002310467A patent/CA2310467A1/en not_active Abandoned
- 1997-11-21 WO PCT/SE1997/001967 patent/WO1999027358A1/en not_active Application Discontinuation
- 1997-11-21 JP JP2000522446A patent/JP2001524669A/en active Pending
Non-Patent Citations (1)
| Title |
|---|
| See references of WO9927358A1 * |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2001524669A (en) | 2001-12-04 |
| CA2310467A1 (en) | 1999-06-03 |
| WO1999027358A1 (en) | 1999-06-03 |
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Legal Events
| Date | Code | Title | Description |
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| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
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| 17P | Request for examination filed |
Effective date: 20000520 |
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| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): BE DE ES FI FR GB IT NL SE |
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| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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| 18D | Application deemed to be withdrawn |
Effective date: 20030603 |