WO2000042382A1 - Method and apparatus for measuring of displacements within a plane - Google Patents
Method and apparatus for measuring of displacements within a plane Download PDFInfo
- Publication number
- WO2000042382A1 WO2000042382A1 PCT/NL2000/000027 NL0000027W WO0042382A1 WO 2000042382 A1 WO2000042382 A1 WO 2000042382A1 NL 0000027 W NL0000027 W NL 0000027W WO 0042382 A1 WO0042382 A1 WO 0042382A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- depicting
- plane
- carrier
- displacement
- depiction
- 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.)
- Ceased
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
Definitions
- the present invention relates to a method for measuring the displacement within a plane of at least a part of a body relative to a reference position, comprising of: - depicting on a carrier by means of depicting means a structure applied to a surface extending over at least the part of the body;
- Displacements within a plane are displacements of a boundary surface of a body parallel to the boundary surface.
- An example of a displacement within a plane is the displacement of a sheet of paper over a desk-top.
- Displacements outside a plane are displacements transversely of the boundary surface of the body, thus for instance perpendicularly upward movement of a horizontal sheet of paper.
- the present invention applies however only to displacements within a plane.
- Such a method finds application for instance in the measuring of slow and small displacements within a plane, particularly of pipes under pressure. This includes particularly, though not exclusively, the determining of phenomena such as stretch, creep and so on.
- this method makes use of coherent light which must be generated by a laser light source.
- the laser light sources are costly devices and require complicated auxiliary equipment for the application of this method.
- the invention therefore provides such a method, wherein the structure is permanently present on at least the part of the body prior to making of the first depiction, and the depicting of the structure on the carriers of the structure takes place by means of noncoherent light.
- the structure is arranged on at least the part of the body prior to the depicting of the structure.
- An irregular structure is preferably arranged herein, so that the comparison between the depictions can be performed easily.
- the structure must be such that the desired local resolution in the displacement is obtained.
- a method is otherwise known from EP-A-0 603 062 for measuring the deformation in paper after the paper has been subjected to forces. For this purpose markings are arranged at predetermined locations on the paper, the paper is subjected to forces and the markings are then depicted. Only discrete markings are herein depicted, and not structures extending over a surface .
- the present invention also provides an apparatus for measuring the displacement within a plane of at least a part of the body relative to the reference position, comprising:
- - comparing means for comparing structures depicted on the carrier at an interval and deriving herefrom the displacements within a plane of the part of the body, wherein the structure is permanently present on at least the part of the body prior to making of the first depiction, and the depicting of the structure on the carrier takes place by means of non-coherent light.
- figure 1 shows a schematic view of an apparatus used in performing the method according to the present invention
- figure 2 shows a schematic perspective view of an apparatus according to a preferred embodiment of the invention.
- figure 1 shows a body 1, wherein it is desired to measure the displacement within a plane or the stretch thereof.
- a structure 2 is situated for this purpose on body 1.
- This structure is formed for instance by a structure inherently present on the body, for instance in the form of the natural roughness of the material, although the structure can likewise be formed by an irregular structure specifically applied to the body.
- Use is made in the present invention of normal, i.e. non-coherent, light. Use is made for this purpose of a separate light source 6 in the form of a lamp. It is also important that light source 6 occupies a fixed position relative to camera 3 by means of the mechanical construction 4.
- the signal from the electronic camera is fed to a computer 7, where the signal is converted into digital form and stored. It is of course possible, when a digital camera is used, for the signal to be immediately available in digital form. A first recording is thus made .
- the memory of the computer herein forms the carrier on which the depiction is made.
- FIG. 2 shows a preferred embodiment of the apparatus according to the invention.
- the apparatus is suitable for recording the displacement and deforming of the wall of a pipe 8, for instance a steam pipe heavily loaded in terms of temperature and pressure.
- a pipe for instance a steam pipe heavily loaded in terms of temperature and pressure.
- shut down the steam pipe and the equipment connected thereto to take a sample of the pipe wall and to examine the microstructures of the sample. It will be apparent that shutting down such a steam pipe is highly undesirable in respect of the resulting shut-down of an entire installation.
- the method according to the invention allows the condition of the material, in particular creep and deformation, to be determined without destructive examination.
- a small plate 9 of an inert metal, for instance gold, is fixed onto pipe wall 8. It is important to fix the small plate, for instance by welding, such that the small plate readily follows the movements of the metal of the pipe. It is important for the same reason that the small plate be thin.
- the small plate serves only for durable preserving of the structure. For this purpose the plate is fixed for instance by welding, wherein it must be ensured that the structure of the pipe wall is not damaged. Possible artefacts of the welding are removed after the welding, the small plate is made smooth and a structure is applied thereto, for instance by radiation.
- a fastening bracket 10 is then arranged on the plate. A method of fastening is also chosen for this purpose which results in a fixed positioning and wherein the functionality of pipe 8 is not affected.
- Bracket 10 comprises a plate 11 which lies against the outer side of the pipe and in which a window is recessed at the position of small plate 9.
- a pipe piece 13 provided on its outside with a supporting ring 14 is mounted fixedly on the plate around the window.
- the pipe piece On its upper edge the pipe piece comprises a female part 15 of a bayonet fitting. The thus formed bracket forms the fixed part of the positioning means.
- an electronic camera or digital camera 4 the housing of which is connected to a cylinder jacket-shaped body 16 in which the objective and the lighting equipment are received.
- Cylindrical body 16 is connected at its end to a pipe 18 by a tapering part 17.
- the end of pipe 18 is provided with a collar 19 which, like pipe 18, fits around pipe piece 13.
- a good positioning in axial direction can be obtained by moving the whole unit as far as the bottom surface of collar 19 against the upper surface of ring 14.
- a good positioning in radial direction is obtained by the fit of pipe piece 13 inside pipe 18, while the bayonet ensures a good positioning in rotation direction.
- An additional fixing is obtained by a pin/snap connection extending through collar 19 and ring 14.
- the program determines the similarities between the areas on both carriers and computes the displacement relative to a reference point of these areas with great similarity.
- a depiction can be made herefrom of the displacement within a plane, whereby stretch, creep and similar phenomena can be determined.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention relates to a method for measuring the displacement within a plane of at least a part of a body relative to a reference position, comprising of: depicting on a carrier by means of depicting means a structure applied to a surface extending over at least said part of the body; retaining the depiction of the structure on the carrier; depicting the structure after a period of time on a second carrier by means of the depicting means; comparing the structures depicted on the carriers; and deriving the displacement within a plane of at least said part of the body from the comparison, wherein the structure is permanently present on at least said part of the body prior to making of the first depiction, and the depicting of the structure on the carriers takes place by means of non-coherent light. The invention also relates to an apparatus for performing such a method.
Description
METHOD AND APPARATUS FOR MEASURING OF DISPLACEMENTS WITHIN A PLANE
The present invention relates to a method for measuring the displacement within a plane of at least a part of a body relative to a reference position, comprising of: - depicting on a carrier by means of depicting means a structure applied to a surface extending over at least the part of the body;
- retaining the depiction of the structure on the carrier; - depicting the structure after a period of time on a second carrier by means of the depicting means;
- comparing the structures depicted on the carriers ; and
- deriving from the comparison the displacement within a plane of at least the part of the body.
Displacements within a plane are displacements of a boundary surface of a body parallel to the boundary surface. An example of a displacement within a plane is the displacement of a sheet of paper over a desk-top. Displacements outside a plane are displacements transversely of the boundary surface of the body, thus for instance perpendicularly upward movement of a horizontal sheet of paper. The present invention applies however only to displacements within a plane. Such a method finds application for instance in the measuring of slow and small displacements within a plane, particularly of pipes under pressure. This includes particularly, though not exclusively, the determining of phenomena such as stretch, creep and so on.
It is important in determining or predicting these phenomena to be able to accurately record minimal displacements within a plane.
Such a method for this purpose is known from NL-A-9200087.
To produce the depiction this method makes use of coherent light which must be generated by a laser light source. The laser light sources are costly devices and require complicated auxiliary equipment for the application of this method.
It is pointed out here that the displacements to be measured within a plane do not lie in the order of magnitude of millimetres but rather in the order of magnitude of micrometres . In order to be able to make a usable depiction here it is important that sufficient precision is achieved. Surprisingly, the inventors have found that it is also possible to achieve the required precision by means of non-coherent light.
The invention therefore provides such a method, wherein the structure is permanently present on at least the part of the body prior to making of the first depiction, and the depicting of the structure on the carriers of the structure takes place by means of noncoherent light.
These measures allow the use of light sources for generating non-coherent light, wherein use can even be made of normal sunlight, so that separate light sources are no longer necessary.
For making of the depiction use can therefore be made of typical electronic or digital cameras which are provided for instance with a CCD chip.
According to a preferred embodiment the structure is arranged on at least the part of the body prior to the depicting of the structure.
It is also possible for the structure to be already present naturally on the part of the body.
An irregular structure is preferably arranged herein, so that the comparison between the depictions can be performed easily. The structure must be such that the desired local resolution in the displacement is obtained.
A method is otherwise known from EP-A-0 603 062 for measuring the deformation in paper after the paper has been subjected to forces. For this purpose markings are arranged at predetermined locations on the paper, the paper is subjected to forces and the markings are then depicted. Only discrete markings are herein depicted, and not structures extending over a surface .
The present invention also provides an apparatus for measuring the displacement within a plane of at least a part of the body relative to the reference position, comprising:
- depicting means for depicting on a carrier a structure arranged on at least a part of the body; and
- comparing means for comparing structures depicted on the carrier at an interval and deriving herefrom the displacements within a plane of the part of the body, wherein the structure is permanently present on at least the part of the body prior to making of the first depiction, and the depicting of the structure on the carrier takes place by means of non-coherent light.
Other attractive preferred embodiments are stated in the remaining sub-claims.
The invention will be elucidated hereinbelow with reference to the annexed figures, in which: figure 1 shows a schematic view of an apparatus used in performing the method according to the present invention; and figure 2 shows a schematic perspective view of an apparatus according to a preferred embodiment of the invention.
The situation of figure 1 shows a body 1, wherein it is desired to measure the displacement within a plane or the stretch thereof.
A structure 2 is situated for this purpose on body 1. This structure is formed for instance by a structure inherently present on the body, for instance in the form of the natural roughness of the material,
although the structure can likewise be formed by an irregular structure specifically applied to the body.
In order to depict the structure on body 1 use is made of an electronic or digital camera 3 and of a positioning device formed by a mechanical construction 4 on which camera 3 is fixedly mounted, wherein it is wished to determine the displacement within a plane of structure 2 relative to the reference depiction.
Use is made in the present invention of normal, i.e. non-coherent, light. Use is made for this purpose of a separate light source 6 in the form of a lamp. It is also important that light source 6 occupies a fixed position relative to camera 3 by means of the mechanical construction 4. The signal from the electronic camera is fed to a computer 7, where the signal is converted into digital form and stored. It is of course possible, when a digital camera is used, for the signal to be immediately available in digital form. A first recording is thus made . The memory of the computer herein forms the carrier on which the depiction is made.
In order to be able to determine the stretch, creep or other displacements within a plane of object 1, a new recording will have to be made after a period of time. This is made in similar manner to the first recording and stored in another part of the memory of computer 7.
It is then possible to determine the stretch by comparing the two depictions stored in the memory of the PC . Figure 2 shows a preferred embodiment of the apparatus according to the invention. The apparatus is suitable for recording the displacement and deforming of the wall of a pipe 8, for instance a steam pipe heavily loaded in terms of temperature and pressure. In order to establish the condition of this steam pipe it is known to shut down the steam pipe and the equipment connected thereto, to take a sample of the pipe wall and to examine the microstructures of the sample. It will be apparent that shutting down such a steam pipe is highly
undesirable in respect of the resulting shut-down of an entire installation.
The method according to the invention allows the condition of the material, in particular creep and deformation, to be determined without destructive examination.
To this end a small plate 9 of an inert metal, for instance gold, is fixed onto pipe wall 8. It is important to fix the small plate, for instance by welding, such that the small plate readily follows the movements of the metal of the pipe. It is important for the same reason that the small plate be thin. The small plate serves only for durable preserving of the structure. For this purpose the plate is fixed for instance by welding, wherein it must be ensured that the structure of the pipe wall is not damaged. Possible artefacts of the welding are removed after the welding, the small plate is made smooth and a structure is applied thereto, for instance by radiation. A fastening bracket 10 is then arranged on the plate. A method of fastening is also chosen for this purpose which results in a fixed positioning and wherein the functionality of pipe 8 is not affected.
Bracket 10 comprises a plate 11 which lies against the outer side of the pipe and in which a window is recessed at the position of small plate 9. A pipe piece 13 provided on its outside with a supporting ring 14 is mounted fixedly on the plate around the window. On its upper edge the pipe piece comprises a female part 15 of a bayonet fitting. The thus formed bracket forms the fixed part of the positioning means.
Use is further made of an electronic camera or digital camera 4, the housing of which is connected to a cylinder jacket-shaped body 16 in which the objective and the lighting equipment are received. Cylindrical body 16 is connected at its end to a pipe 18 by a tapering part 17.
For temporary fixing of the thus formed frame to the fixed part of the positioning means the end of
pipe 18 is provided with a collar 19 which, like pipe 18, fits around pipe piece 13. A good positioning in axial direction can be obtained by moving the whole unit as far as the bottom surface of collar 19 against the upper surface of ring 14. A good positioning in radial direction is obtained by the fit of pipe piece 13 inside pipe 18, while the bayonet ensures a good positioning in rotation direction. An additional fixing is obtained by a pin/snap connection extending through collar 19 and ring 14.
During a comparing method executed by the PC the program determines the similarities between the areas on both carriers and computes the displacement relative to a reference point of these areas with great similarity. A depiction can be made herefrom of the displacement within a plane, whereby stretch, creep and similar phenomena can be determined.
It is also important in order to determine displacements with a high resolution that an entire surface is depicted and not just a number of points.
Claims
1. Method for measuring the displacement within a plane of at least a part of a body relative to a reference position, comprising of:
- depicting on a carrier by means of depicting means a structure applied to a surface extending over at least said part of the body; - retaining the depiction of the structure on the carrier;
- depicting the structure after a period of time on a second carrier by means of the depicting means;
- comparing the structures depicted on the carriers; and
- deriving the displacement within a plane of at least said part of the body from the comparison, characterized in that the structure is permanently present on at least said part of the body prior to making of the first depiction, and that the depicting of the structure on the carriers takes place by means of non-coherent light.
2. Method as claimed in claim 1, characterized in that prior to the depicting of the structure the structure is arranged on at least said part of the body.
3. Method as claimed in claim 2, characterized in that the body is of metal and that a layer manufactured from an inert metal , to which the structure is applied, is arranged on the part of the body to be examined.
4. Method as claimed in claim 3, characterized in that the structure is only applied to the layer of an inert metal after this layer has been arranged on the metal body.
5. Method as claimed in any of the foregoing claims, characterized in that prior to performing of a first measurement positioning means for the means for recording the structure are arranged on the body.
6. Method as claimed in claim 5, characterized in that at least the location where the inert metal is arranged is ground before the positioning means are arranged on the body.
7. Method as claimed in any of the foregoing claims, characterized in that prior to performing of the method the location on the body is determined where defects in the wall of the body will most probably occur.
8. Method as claimed in any of the foregoing claims, characterized in that the structure is depicted in electronic or digital form on the carriers and that the comparison of the depicted structures and the deriving of the displacement within a plane takes place using a computer.
9. Method as claimed in any of the foregoing claims, characterized in that the structure is irregular.
10. Apparatus for measuring the displacement within a plane of at least a part of a body relative to a reference position, comprising: - depicting means for depicting on a carrier a structure arranged on at least a part of the body; and
- comparing means for comparing structures depicted on the carrier at an interval and deriving herefrom the displacements within a plane of said part of the body, characterized in that the depicting means are adapted to make the depiction using non-coherent light.
11. Apparatus as claimed in claim 10, characterized in that the depicting means comprise an electronic or digital camera and that the apparatus comprises positioning means which are mounted in at least partially fixed manner on the object.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU23318/00A AU2331800A (en) | 1999-01-15 | 2000-01-14 | Method and apparatus for measuring of displacements within plane |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1011035 | 1999-01-15 | ||
| NL1011035A NL1011035C2 (en) | 1999-01-15 | 1999-01-15 | Method and device for measuring in-plane displacements. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2000042382A1 true WO2000042382A1 (en) | 2000-07-20 |
Family
ID=19768478
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/NL2000/000027 Ceased WO2000042382A1 (en) | 1999-01-15 | 2000-01-14 | Method and apparatus for measuring of displacements within a plane |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU2331800A (en) |
| NL (1) | NL1011035C2 (en) |
| WO (1) | WO2000042382A1 (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1979000320A1 (en) * | 1977-11-25 | 1979-06-14 | Nat Res Dev | Method and apparatus for sensing in-plane deformation of a surface |
| JPS57125803A (en) * | 1981-01-29 | 1982-08-05 | Toyoda Gosei Co Ltd | Method for measuring strain of sample surface |
| DE3631187A1 (en) * | 1986-09-12 | 1988-03-24 | Schoeffel Manfred Dipl Ing | Method and device for determining the distance between marks on measured objects |
| EP0603062A1 (en) * | 1992-12-17 | 1994-06-22 | Centre De Recherche Saint-Gobain Papier-Bois Gie | Method and device for the non-destructive real time measurement of mechanical properties of a sheet material |
| JPH0755437A (en) * | 1993-08-23 | 1995-03-03 | Japan Tobacco Inc | Camera for optical extensometer |
| WO1998021547A1 (en) * | 1996-11-13 | 1998-05-22 | Noranda Inc. | Optical strain sensor and method for the measurement of microdeformations |
-
1999
- 1999-01-15 NL NL1011035A patent/NL1011035C2/en not_active IP Right Cessation
-
2000
- 2000-01-14 AU AU23318/00A patent/AU2331800A/en not_active Abandoned
- 2000-01-14 WO PCT/NL2000/000027 patent/WO2000042382A1/en not_active Ceased
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1979000320A1 (en) * | 1977-11-25 | 1979-06-14 | Nat Res Dev | Method and apparatus for sensing in-plane deformation of a surface |
| JPS57125803A (en) * | 1981-01-29 | 1982-08-05 | Toyoda Gosei Co Ltd | Method for measuring strain of sample surface |
| DE3631187A1 (en) * | 1986-09-12 | 1988-03-24 | Schoeffel Manfred Dipl Ing | Method and device for determining the distance between marks on measured objects |
| EP0603062A1 (en) * | 1992-12-17 | 1994-06-22 | Centre De Recherche Saint-Gobain Papier-Bois Gie | Method and device for the non-destructive real time measurement of mechanical properties of a sheet material |
| JPH0755437A (en) * | 1993-08-23 | 1995-03-03 | Japan Tobacco Inc | Camera for optical extensometer |
| WO1998021547A1 (en) * | 1996-11-13 | 1998-05-22 | Noranda Inc. | Optical strain sensor and method for the measurement of microdeformations |
Non-Patent Citations (2)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN vol. 6, no. 221 (P - 153)<1099> 5 November 1982 (1982-11-05) * |
| PATENT ABSTRACTS OF JAPAN vol. 95, no. 6 31 July 1995 (1995-07-31) * |
Also Published As
| Publication number | Publication date |
|---|---|
| NL1011035C2 (en) | 2000-07-18 |
| AU2331800A (en) | 2000-08-01 |
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