Title of Invention

"METHOD AND SYSTEM FOR NON-DESTRUCTIVE CONTROL OF A SURFACE USING A DYE PRODUCT"

Abstract A method of non-destructive testing of the state of a surface which may have cracks in it by observing waves emitted by a dye applied to the surface and present in the cracks in response to an incident excitation beam of wavelength appropriate to the dye, in which an ultraviolet incident beam is used, characterized in that a rectilinearly polarized ultraviolet beam is used and in that the waves emitted by the dye are observed through a rotatable polarized wave analyser that is first rotated to eliminate from observation the wave due to residual dye on the surface and then to determine the depths of the cracks.
Full Text The invention relates to techniques for nondestructive dye penetration testing of the state of a surface, such as the dye penetration and magnetoscopic techniques in particular.
Non-destructive dye penetration testing, which is used in particular for checking for the presence of cracks in a surface, entails the application to that surface of a dye under conditions enabling the dye to penetrate into the defects to be detected, illuminating the surface with incident light, and observing the light emitted by the dye present in the cracks and by the residual dye on the surface.
The surface is illuminated by a beam from a mercury vapor lamp, for example, or from a neon tube, and which includes radiation capable of exciting the dye, which responds by emitting visible monochromatic light that can be observed by means of a photosensitive system, for example, possibly associated with means for producing a digital image that is then processed by an image processing system.
The color of the visible light depends on the dye used. It is orange, for example, if the dye is rhodamine 6G.
A technique of the above kind is described in the publication FR 2 711 426, for example.
The problem arises of optimizing the observation, in particular optimizing the observation of cracks, which is disturbed by the simultaneous observation of an image of residual traces of dye which remain on the surface.
One proposal for optimizing the observation involves processing the digital image, for example as described in the aforementioned publication.
Another problem is determining the depth of the cracks.
The publication FR 2 73 6 152 describes a method and a dye penetration system for determining the dimensions of defects.
The above two publications indicate the difficulty and the consequential complexity of methods and systems that have been designed to optimize the images and to assess the dimensions of cracks.
The present invention provides a method and a system which are remarkably simple, which optimize the images and which assess the depth of the cracks.
The invention is based on the observation that when the dye is excited by a rectilinearly polarized wave the dye in an area of the surface or in a crack emits a rectilinearly polarized wave at an angle to the incident rectilinearly polarized wave which depends on the thickness of the product in the area or the crack concerned.
The invention uses the angle between the incident rectilinearly polarized wave and the rectilinearly polarized wave emitted by the dye to eliminate from the observation areas where residual dye is present on the surface and retain only areas in which the dye has penetrated into the cracks. This approach is based on the fact that the angle corresponding to a wave reflected by residual dye on the surface is different from that corresponding to the dye present in a crack because the thickness of the residual dye on the surface is always less than the thickness of dye in a crack.
According to another aspect of the invention, the angles corresponding to the cracks are used to determine the depths of the cracks.
A system for implementing the invention therefore includes means for producing a rectilinearly polarized incident wave at a wavelength chosen to excite the dye,
transmission means for guiding the wave toward the surface to be studied, observation means for observing rectilinearly polarized waves emitted by dye on the surface and in the cracks, and means on the path of the emitted waves, between the surface and the observation means, for selecting emitted waves according to the angle between the incident rectilinearly polarized wave and the rectilinearly polarized wave emitted by the dye.
The surface under examination is illuminated with a rectilinearly polarized wave from a non-polarized light source associated with a polarizer or preferably from a polarized light source.
This applies in particular to a laser, which delivers a rectilinearly polarized wave with parallel edges.
The laser has the further advantage of emitting perfectly monochromatic light in a very fine beam which is coherent over great distances.
Rectilinearly polarized waves emitted by the dye are selected by one or more polarized wave analyzers on the path of the waves.
Embodiments of the invention are described hereinafter with reference to the figures of the accompanying drawings, in which:
- figure 1 is a diagram of a first embodiment of a system according to the invention applied to a dye penetration technique for observing cracks in a surface;
- figure 2 is a diagram of a second embodiment using a dye penetration technique for simultaneously observing two opposite faces of a part which can rotate and move along X, Y and Z axes;
- figure 3 is a diagram of a third embodiment using a dye penetration technique for simultaneously observing two opposite faces of a plate and including a set of oscillating mirrors which are controlled to scan the
incident beam over the faces observed;
- figure 4 is a diagram of a fourth embodiment using a dye penetration technique for examining bores or cells; and
- figure 5 is a diagram of a fifth embodiment applied to the magnetoscopic testing of bars.
The systems implementing the invention shown in the figures include:
- a laser (1),
- transmission means (T) for transmitting the beam from the laser to a surface (S) to be studied or to a calibration surface, and
- an observation video camera (2) equipped with a telephoto lens and an analyzer (3).
The laser (1) preferably emits polarized ultraviolet light centered on a wavelength appropriate to the dye used, for example a wavelength of 330 nanometres.
The transmission means (T) can be of highly varied types:
- in the figure 1 embodiment, the beam from the laser (1) is transmitted by optical fibers (4) to the surface (5) to be examined,
- in the figure 2 embodiment a plate (5) at the exit of the laser (1) splits the laser beam into a portion (6) which is conveyed by optical fibers or otherwise to a surface (7) of a part (8) to be observed and a portion (9) which is conveyed by optical fibers or otherwise to an opposite surface (10) of the part (8),
- in the figure 3 embodiment a plate (5) at the exit from the laser (1) , as in the figure 2 embodiment, splits the beam from the laser into two beams (6, 9) which illuminate two respective faces (7) and (10) of a wall (8) ; in this example the system includes two sets of mirrors (M) and (MM) for transmitting the two beams to the surfaces (7, 10) ,
- in the figure 4 embodiment, the beam from the laser (1) is transmitted by optical fibers (4) to an endoscope (11) which enables the beam to reach areas to which access is difficult, for example to illuminate the internal surface of a bore or a cell, and
- in the figure 5 embodiment, the beam from the laser (1) passes through a plate (12) and is then conveyed to the surface to be examined, in this instance that of a bar (13), by optical fibers (14).
The above examples do not exclude other transmission means.
The incident laser beam is much narrower than the beam from a mercury vapor lamp or a neon tube. The invention therefore provides means for scanning the beam over the surface to be examined, either by moving the beam or by moving the surface.
In the figure 2 embodiment, the part (8) to be examined is placed on a turntable (15) which can be moved in translation along an axis (X) and which can move up and down along an axis (Z) parallel to the rotation axis of the part.
In the figure 3 embodiment, the mirrors for reflecting the two portions of the beams from the laser comprise, firstly, fixed mirrors (Ml, M2) and, secondly, mirrors (MM1, MM2, MM3 and MM4) which can oscillate under the control of a computer programmed so that the beams scan the surfaces to be examined.
In the figure 4 embodiment, the endoscope includes a support 16 which can rotate about a rotation axis (R) , a telescopic waveguide (17) along the rotation axis (Z) and an end prism (18) which can move along the (X, Y) axes, and the part (P) which includes the bores (19) to be examined is placed on a turntable (20) . The line (21) in the figure symbolizes the fact that the end prism (18) can be lowered into the bore (19).
In the figure 5 embodiment, the part (13) observed is a bar which can rotate and the end of the fiber optic guide (14) is carried by a carriage (22) which can move parallel to the bar.
The observation video camera (2) and its polarized wave analyzer (3) are duplicated if it is necessary to observe two surfaces simultaneously, as is the case in the figure 2 and 3 embodiments.
Splitter plates are used, if required, to pass the incident rays and deflect the emergent rays (figures 3 and 5).
In the figure 4 embodiment, an optical fiber coupler (23) is used to enable the same bundle of optical fibers (4) to transmit the incident beam from the laser (1) to the part (P) and to transmit the wave emitted by the excited dye to the video camera (2).
This is possible because the video camera used is not sensitive to ultraviolet radiation.
The equipment is calibrated in a manner known per se using a block with cracks of known depth that has been prepared by dye penetration or magnetoscopy.
In the absence of the analyzer (3), or by locking the analyzer to the polarity of the laser (1) , the image observed shows the presence of cracks in the block buried in light spots with the same wavelength caused by residual dye on the surface of the block.
If the analyzer according to the invention is rotated, the unwanted spots are seen to disappear progressively, leaving only the images due to the calibration cracks for one particular angle of rotation of the analyzer.
The analyzer is rotated further to eliminate the successive images of cracks in increasing depth order: it is therefore possible to draw up a calibration curve relating the angle of rotation of the analyzer to the depth
of the cracks, enabling the depths of cracks in a surface examined to be determined subsequently.
A double analyzer is preferably used, i.e. an analyzer which includes two successive analyzers (3a, 3b) , namely a front analyzer (3a) eliminating unwanted spots and a rear analyzer (3b) determining the depth of the cracks.
The two analyzers are mounted in a common turret, for example, and are rotated at the same time until the unwanted spots are eliminated, after which only one of the analyzers is rotated, to evaluate the depths of the cracks.
Each analyzer is of a type known in the art, for example a plate on one face of which are parallel lines of identical prisms.
The invention is not limited to the above embodiments.










WE CLAIM:-
1. A method of non-destructive testing of the state of a surface which may have cracks in it by observing waves emitted by a dye applied to the surface and present in the cracks in response to an incident excitation beam of wavelength appropriate to the dye, in which an ultraviolet incident beam is used, characterized in that a rectilinearly polarized ultraviolet beam is used and in that the waves emitted by the dye are observed through a rotatable polarized wave analyser that is first rotated to eliminate from observation the wave due to residual dye on the surface and then to determine the depths of the cracks.
2. A method as claimed in claim 1, wherein the ultraviolet beam is centred on a wavelength of 330 nanometers.
3. A method as claimed in claim 1 or claim 2, wherein the waves emitted by the dye are observed using a video camera that is not sensitive to ultraviolet radiation.
4. A method as claimed in any one of claims 1 to 3, wherein a calibration process establishes angles of rotation of the analyser which successively eliminate from observation cracks of increasing depth.
5. A method as claimed in any one of claims 1 to 4, wherein said surface is scanned with the incident beam by moving the surface or the incident beam during observation.
6. A system for implementing a dye penetration or magneto scopic method using a dye present in the cracks of a surface to be examined by a method as claimed in claim 1, which system includes:
production means (1) for producing an ultraviolet beam, transmission means (T) for guiding that beam toward the surface to be examined.
observation means (2) for observing waves emitted by the dye due
to the incident wave,
characterized in that said production means (1) are chosen to produce a rectilinearly polarized ultraviolet beam, and in that the device includes a rotary analyser (3) of polarized waves on the path of the waves emitted by the dye between the surface and the observation means (2) so that rotating the analyser first progressively eliminates from observation the unwanted spots and then determines the depths of the cracks.
7. A system as claimed in claim 6, wherein the production means (1) comprise a laser generator.
8. A system as claimed in claim 6 or claim 7, wherein the ultraviolet beam is centred on a wavelength of 330 nanometers.
9. A system as claimed in any one of claims 6 to 8, wherein a video camera that is not sensitive to ultraviolet radiation is used for observation.
10. A system as claimed in any one of claims 6 to 9, including means for moving the surface or the incident beam to scan the surface with the incident wave during observation.
11. A system as claimed in claim 10, including oscillating mirrors (MM) controlled by computer to deflect the incident beam to cause it to scan the surface.
12. A system as claimed in claim 10 or claim 11, wherein the transmission means (T) include an endoscope (11) terminating in a prism (18) adapted to enter a bore or a cell of a part to be examined.
13. A system as claimed in any one of claims 6 to 12, wherein the
angles of rotation of the rotatable analyser (3) have been calibrated in
correspondence with the depths of cracks.
14. A system as claimed in any one of claims 6 to 12, wherein the
rotatable analyser consists of two successive rotatable analysers (3a,3b)
respectively for eliminating unwanted spots due to residual dye on the
surface and for determining the depth of cracks.

Documents:

abstract.jpg

in-pct-2001-97-del-abstract.pdf

in-pct-2001-97-del-claims.pdf

in-pct-2001-97-del-correspondence-others.pdf

in-pct-2001-97-del-correspondence-po.pdf

in-pct-2001-97-del-description (complete).pdf

in-pct-2001-97-del-drawings.pdf

in-pct-2001-97-del-form-1.pdf

in-pct-2001-97-del-form-19.pdf

in-pct-2001-97-del-form-2.pdf

in-pct-2001-97-del-form-3.pdf

in-pct-2001-97-del-form-5.pdf

in-pct-2001-97-del-gpa.pdf

in-pct-2001-97-del-petition-137.pdf

in-pct-2001-97-del-petition-138.pdf


Patent Number 250925
Indian Patent Application Number IN/PCT/2001/00097/DEL
PG Journal Number 06/2012
Publication Date 10-Feb-2012
Grant Date 07-Feb-2012
Date of Filing 05-Feb-2001
Name of Patentee HOLORES INC
Applicant Address 1426 SW OSPREY COVE, PORT ST LUCIE, FL 34986, USA,
Inventors:
# Inventor's Name Inventor's Address
1 PIERRE-MARIE PAILLIOTET 20 SQUARE BAUDELAIRE,91450 SOISY SUR SEINE,FRANCE,
PCT International Classification Number G01N 21/91
PCT International Application Number PCT/FR99/01942
PCT International Filing date 1999-08-05
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 98 10062 1999-08-05 France