GB2108684A - A method of carrying out crack tests and a test body for this method - Google Patents
A method of carrying out crack tests and a test body for this method Download PDFInfo
- Publication number
- GB2108684A GB2108684A GB08231727A GB8231727A GB2108684A GB 2108684 A GB2108684 A GB 2108684A GB 08231727 A GB08231727 A GB 08231727A GB 8231727 A GB8231727 A GB 8231727A GB 2108684 A GB2108684 A GB 2108684A
- Authority
- GB
- United Kingdom
- Prior art keywords
- crack
- test
- test body
- lacquer
- area
- 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.)
- Granted
Links
- 238000012360 testing method Methods 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000011248 coating agent Substances 0.000 claims abstract description 7
- 238000000576 coating method Methods 0.000 claims abstract description 7
- 230000005855 radiation Effects 0.000 claims abstract description 5
- 230000001154 acute effect Effects 0.000 claims abstract description 3
- 239000004972 Polyurethane varnish Substances 0.000 claims 1
- 239000004922 lacquer Substances 0.000 abstract description 26
- 238000005286 illumination Methods 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 2
- 238000011156 evaluation Methods 0.000 description 4
- 239000003973 paint Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 238000009658 destructive testing Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000004848 polyfunctional curative Substances 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/08—Testing mechanical properties
- G01M11/081—Testing mechanical properties by using a contact-less detection method, i.e. with a camera
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
- G01N19/08—Detecting presence of flaws or irregularities
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0062—Crack or flaws
- G01N2203/0066—Propagation of crack
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/027—Specimens with holes or notches
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
- G01N2203/0652—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors using contrasting ink, painting, staining
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
Landscapes
- Analytical Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
In a method for measuring the length of the cracks and/or the progress of cracks in test bodies, samples of material and components, the surface of the body is pre-treated by grinding an area of the test body, applying a reflective coating, and the body is then subjected to load. The surface (2) of the test area (5) is coated after grinding with a thin layer (3) comprising a transparent lacquer which cracks with the test body (1). The test area (5) is irradiated by an illumination device (4) at an acute angle of incidence ( alpha ), producing substantially total reflection on the layer (3) of lacquer. Due to reflection and refractive effects at the crack area of the layer of lacquer there is a clear high contrast representation of the crack viewable e.g. by camera 6, from a position not reached by radiation reflected by the lacquer surface. <IMAGE>
Description
SPECIFICATION A method of carrying out crack tests and a test body for this method
The invention relates to a method of carrying out cracked tests, more particularly for testing or measuring the length of cracks and/or the progress of cracks in test bodies, samples of material or components. The invention also relates to a test body for carrying out the method.
In a known method of carrying out crack tests using a suitable test body, the surface thereof is highly polished at the area or point on the body where crack formation is anticipated. This is necessary in order to make cracks on the surface of the test body visible, for example on a screen, by an illumination and photographic device and also in order to enable the cracks to be evaluated subsequently. The cracks may be so fine that particularly when not under load they cannot be seen with the naked eye, for example. However, the polishing the test body used in this method is time consuming and expensive.
It is the object of this invention to simplify the known method and to provide a test body in which the formation of cracks and the spread of cracks can be easily recognised, for example on the screen of a viewing and measuring device, or clearly recorded in an evaluation device.
Accordingly, the invention provides a method of carrying out crack tests on a test body which includes the steps of applying to an area of the test body a coating which has a smooth reflective surface and which will crack or tear with the test body, illuminating that surface with radiation at an acute angle of incidence and observing the body from a position not reached by the radiation reflected by the surface.
The method provides a particularly clear and high contrast image of the surface crack, which can be photographed and/or displayed on the screen. The crack shows up light on a dark background. This clear representation of the crack facilitates evaluation and analysis of the test, particularly measurement of the length of the crack and testing of the progress of the crack.
The contrast is largely independent of the width of the crack. The crack can still be seen clearly even when the edges of the crack close when the test body is not under load. In a test body or the like for carrying out the method in accordance with the invention, the surface of the area to be tested may be ground before the thin layer of lacquer or paint is applied. This is less expensive than polishing the area to be tested, as was previously necessary.
The invention is shown schematically in the drawings, using one exemplary embodiment and described in greater detail in the description which follows:
Fig. 1 shows a test arrangement in side view for the purpose of measurement or testing by the method according to the invention;
Fig. 2 shows a cross-section through a test member which has a crack; and
Fig. 3 shows a plan view of the sample with a crack.
The measuring or testing arrangement shown in side view has a test body 1 which is mounted in a vertical testing machine, in a manner not shown, and which can be put under dynamic load.
The load is applied in the plane of the paper or parallel to the plane of the paper in this example and perpendicular to the centre line of the test body 1 shown in the drawing. The test body is a so called CT test object (compact-tension test object) for destructive testing of the stress characteristics. However, other types of test body, samples of material, components or the like can be tested.
The test body 1 has applied to it a thin transparent layer of lacquer 3 on the surface 2 which is to be tested. An illumination device 4 is arranged on the test machine in a suitable manner and a test area 5 of the test body 1 is irradiated by the device 4. The angle a (between the surface 2 of the test body and the axis of the illumination device 4) at which light falis from the illumination device onto the test area 5 should be selected so that the light radiated is reflected as far as possible completely by the layer of lacquer. A light incidence angle m of approximately 20 degrees has proved suitable. The light is arranged to fall onto the crack approximately transversely, i.e. at an angle of approximately 90 degrees. This provides particularly clear display of the crack.
The light incidence angle (a), the direction in which the light falls, and the light intensity can be selected and optimised by the operating staff so that the surface 2 of the test body 1 appears uniformally dark on the screen and a crack appears as bright as possible.
Using a camera 6 the image of the test area 5
is photographed and transmitted to a screen or evaluation device in enlarged form. The progress of a crack can be observed on the screen, for example. Using an evaluation device
measurement of the length of the crack, for example, and other tests can be carried out. The angular arrangement of the camera in relation to the surface of the test body can also be selected to provide good representation of the crack. An angle of approximately 40 degrees between the axis of the camera and a perpendicular to the surface of the test body has proved to be suitable.
Fig. 2 shows a cross-section through a test body having a crack (section A-B in Fig. 3). The test body 1 with the layer of lacquer 3 has a crack 7. The layer of lacquer cracks with the test body.
The light emanating from the illumination device is indicated by straight parallel lines, and, as shown, is effectively completely reflected from the lacquer so that this part of the image appears dark on the screen. In the crack region, on the other hand, the light is scattered reflection or refraction effects occur which lighten the sides of the crack clearly. Because of the total reflection, i.e. total loss of light, over all of the rest of the surface of the test area, a bright and high contrast representation of the crack is given on a dark background.
Fig. 3 shows a portion of a notched and cracked CT-test object 1 in plan view. The crack 7 on the test object 1 is shown as a clear while line on the screen at the test area 5 indicated in broken lines.
Before applying the layer of lacquer the test object is preferably ground at the test area. Very fine work such as mirror polishing is not necessary. The depth of roughness of the surface after grinding should be approximately 10.
A transparent and very shiny synthetic lacquer or paint is used. A mono-component polyurethane lacquer or a bi-component lacquer have proved suitable. The brittleness of the lacquer has to be matched to the 10 extension characteristics of the material to be tested. The layer of lacquer or paint should crack or tear with the test body. The lacquer or paint should not be either too brittle nor too viscous since in either case the crack would not be transferred perfectly from the 15 surface of the test object to the layer of lacquer.
The brittleness of the lacquer can be altered in the case of mono-component lacquer for example by adding softeners or tempering at an elevated temperature. In the case of bi-component lacquer it can 20 be effected by suitable metering of the hardener.
The layer of lacquer has to be sufficiently thick to cover the surface roughness of the surface of the test object so that as little scatting as possible is caused by the surface of the test object since this would interfere with the process. The layer of lacquer cannot be too thick either because in that case the layer might not crack completely and therefore the test results would be falsified. A suitable thickness for the layer of lacquer has proved to be a few hundredths of a millimeter.
The lacquer is applied with a soft brush to the said suitable thickness. After drying and hardening the layer of lacquer exhibits a very smooth and shiny surface so that the incoming light is easily reflected.
Claims (8)
1. A method of carrying out crack tests on a test body which includes the steps of applying to an area of the test body a coating which has a smooth reflective surface and which will crack or tear with the test body, illuminating that surface with radiation at an acute angle of incidence, and observing the body from a position not reached by the radiation reflected by the surface.
2. A method as claimed in claim 1 including the step of grinding said area of the test body before application of the coating.
3. A method as claimed in claim 1 or 2 wherein said angle of incidence is between 10 and 30 degrees.
4. A method as claimed in claim 3 wherein the
body is observed at an angle of about 40 degrees to the point at which the crack is expected.
5. A method as claimed in any preceding claim wherein the coating is transparent.
6. A method as claimed in any preceding claim wherein the coating is a polyurethane varnish.
7. A method as claimed in any preceding claim wherein the coating is few hundreths of a millimeter thick.
8. A test body suitable for crack testing by a method as claimed in any of claims 1 to 7.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19813144379 DE3144379C2 (en) | 1981-11-07 | 1981-11-07 | Procedure for carrying out crack investigations and test specimens for carrying out the procedure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2108684A true GB2108684A (en) | 1983-05-18 |
| GB2108684B GB2108684B (en) | 1985-05-22 |
Family
ID=6145932
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08231727A Expired GB2108684B (en) | 1981-11-07 | 1982-11-05 | A method of carrying out crack tests and a test body for this method |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5887444A (en) |
| DE (1) | DE3144379C2 (en) |
| FR (1) | FR2516244B1 (en) |
| GB (1) | GB2108684B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4574642A (en) * | 1984-11-23 | 1986-03-11 | The Firestone Tire & Rubber Company | Apparatus for automated crack growth rate measurement |
| US4716459A (en) * | 1985-01-25 | 1987-12-29 | Nippon Kokan Kabushiki Kaisha | Fatigue crack position detection apparatus |
| US4911017A (en) * | 1989-04-21 | 1990-03-27 | The Goodyear Tire & Rubber Company | Multiple sample automated cut growth analysis |
| FR2682763A1 (en) * | 1991-10-18 | 1993-04-23 | Schade Kg | METHOD AND DEVICE FOR CONTROLLING THE SCRATCH BEHAVIOR OF FORMED PARTS, ESPECIALLY GLASS FOR MOTOR VEHICLES. |
| EP2990775A1 (en) * | 2014-08-28 | 2016-03-02 | The Boeing Company | Systems and methods for detecting crack growth |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH668483A5 (en) * | 1985-12-17 | 1988-12-30 | Zellweger Uster Ag | METHOD AND DEVICE FOR DETERMINING THE SURFACE STRUCTURE OF A LONG STRETCH TEST BODY, IN PARTICULAR FOR MEASURING THE HAIRNESS OF A YARN. |
| DE9211860U1 (en) * | 1991-09-16 | 1992-11-05 | Lisec, Peter, Amstetten-Hausmening | Arrangement for testing the sealing of insulating glass panes |
| DE102007024059B4 (en) | 2007-05-22 | 2017-11-09 | Illinois Tool Works Inc. | Apparatus and method for evaluating a control body in a color penetration method |
| CN105738230B (en) * | 2016-04-30 | 2018-09-14 | 山西省交通科学研究院 | A kind of asphalt Reflection Cracking performance testing device and test method |
| CN107091610B (en) * | 2017-04-19 | 2019-05-07 | 清华大学 | A three-dimensional dynamic online measuring device for large-scale structures and its measuring method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE534158C (en) * | 1926-12-21 | 1931-09-23 | Maybach Motorenbau G M B H | Method for determining the direction and measuring the surface tension on structural parts |
| US2310845A (en) * | 1940-10-03 | 1943-02-09 | Magnaflux Corp | Method of determining the magnitude of strains in rigid articles |
| US2449883A (en) * | 1945-01-08 | 1948-09-21 | Baldwin Locomotive Works | Fatigue indicator |
| DE1098741B (en) * | 1958-09-25 | 1961-02-02 | Bundesrep Deutschland | Crack extensometer |
| JPS5418157B1 (en) * | 1969-12-27 | 1979-07-05 | ||
| DE2415592C3 (en) * | 1974-03-30 | 1979-06-21 | Phieler, Thomas, 2400 Luebeck | Method for measuring imperfections in an annular sealing zone provided with a sealing compound on the bottom of a rotationally symmetrical cover |
| DE2718086C2 (en) * | 1976-04-24 | 1985-07-11 | Daidotokushuko K.K., Nagoya, Aichi | Device for the detection of surface defects in steel parts |
-
1981
- 1981-11-07 DE DE19813144379 patent/DE3144379C2/en not_active Expired
-
1982
- 1982-05-10 JP JP7676682A patent/JPS5887444A/en active Pending
- 1982-10-04 FR FR8216596A patent/FR2516244B1/en not_active Expired
- 1982-11-05 GB GB08231727A patent/GB2108684B/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4574642A (en) * | 1984-11-23 | 1986-03-11 | The Firestone Tire & Rubber Company | Apparatus for automated crack growth rate measurement |
| US4716459A (en) * | 1985-01-25 | 1987-12-29 | Nippon Kokan Kabushiki Kaisha | Fatigue crack position detection apparatus |
| EP0210278A4 (en) * | 1985-01-25 | 1988-06-27 | Nippon Kokan Kk | APPARATUS FOR DETECTING THE POSITION OF A CRACK CAUSED BY FATIGUE. |
| US4911017A (en) * | 1989-04-21 | 1990-03-27 | The Goodyear Tire & Rubber Company | Multiple sample automated cut growth analysis |
| FR2682763A1 (en) * | 1991-10-18 | 1993-04-23 | Schade Kg | METHOD AND DEVICE FOR CONTROLLING THE SCRATCH BEHAVIOR OF FORMED PARTS, ESPECIALLY GLASS FOR MOTOR VEHICLES. |
| EP2990775A1 (en) * | 2014-08-28 | 2016-03-02 | The Boeing Company | Systems and methods for detecting crack growth |
| US9528945B2 (en) | 2014-08-28 | 2016-12-27 | The Boeing Company | Systems and methods for detecting crack growth |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3144379C2 (en) | 1987-01-02 |
| FR2516244A1 (en) | 1983-05-13 |
| FR2516244B1 (en) | 1985-07-12 |
| GB2108684B (en) | 1985-05-22 |
| JPS5887444A (en) | 1983-05-25 |
| DE3144379A1 (en) | 1983-05-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |