 Bending beam strain gauging method and test setup for carrying out such a strain gauging method
专利摘要:
The invention relates to a strain measurement method for determining the stretchability of thin layers of a wall paint (20) or a multilayer wall coating system (25), and comprises the following steps: - providing a bending beam (1) made of an absorbent material with a beam length (L); - Arranging a notch (2) on a broad side (11) in the middle (L / 2) of the bending beam (1); alternatively - applying a wall paint (20) on the smooth broad side (12) opposite the notched broad side (11); or - applying a multi-layer wall coating system (25) to the notched broad side (11) of the bending beam (1); and further - arranging measuring points (M) on the applied wall paint (20) or wall coating system (25); - Recording at least one initial length (L0) between measuring points (M) on the undeformed bending beam (1); - performing a three-point bending test with a test device; - Recording the bending deformation of the bending beam (1) with an industrial camera (7); - Stop the three-point bending test as soon as there is cracking with hairline cracks; - Determine the change in length ΔL of the wall coating (20) or wall coating system (25) applied to the bending beam (1). 公开号:AT521308A1 申请号:T50471/2018 申请日:2018-06-12 公开日:2019-12-15 发明作者:Ddipl Ing Aleksandar Radoevski Bsc 申请人:Univ Wien Tech； IPC主号:
专利说明:
Summary The invention relates to a strain measurement method for determining the stretchability of thin layers of a wall paint (20) or a multilayer wall coating system (25), and comprises the following steps: - Providing a bending beam (1) made of an absorbent material with a beam length (L); - Arranging a notch (2) on a broad side (11) in the middle (L / 2) of the bending beam (1); optionally - Applying a wall paint (20) on the smooth broad side (12) opposite the notched broad side (11); or - Applying a multi-layer wall coating system (25) on the notched broad side (11) of the bending beam (1); as well as further - Arranging measuring points (M) on the applied wall paint (20) or wall coating system (25); - Recording at least one initial length (L0) between measuring points (M) on the undeformed bending beam (1); - performing a three-point bending test with a test device; - Recording the bending deformation of the bending beam (1) with an industrial camera (7); - Stop the three-point bending test as soon as there is cracking with hairline cracks; - Determine the change in length Al of the wall coating (20) or wall coating system (25) applied to the bending beam (1). Fig. 1/39 P17285 Bending beam strain gauging method and test setup for carrying out such a strain gauging method The present invention relates to a strain measurement method for determining the stretchability of thin layers of a wall paint or a multi-layer wall coating system. Likewise, within the scope of the invention, variants of a test set-up for carrying out the strain measurement method according to the invention are also specified, with which test set-up the stretchability of thin layers of a wall paint or a multi-layer wall coating system can be determined. To the best of the knowledge of the applicant, at least in Europe there is currently no standardized measuring method that would be suitable for determining the elasticity of wall coatings or interior coatings or the elasticity and crack bridging capacity of multi-layer wall coating systems for building spaces. In the following, the term interior coating is understood to mean a wall or ceiling coating which is intended for use in the interior, possibly also in the exterior in building construction. For example, it means dispersion paints, latex paints, silicate paints or lime paints. Wall or ceiling coatings of this type are usually applied to largely crack-free building surfaces, for example interior walls or interior ceilings. The term multi-layer wall coating system is understood below to mean a system which is used for coating building surfaces which have cracks or cracks. For this purpose, cracks and cracks in the interior wall or ceiling to be coated are usually first filled or covered with a filler. If necessary, a reinforcing layer, which is expediently designed, for example, as a glass fiber fleece, can also be applied with the filler to cover wall cracks or wall cracks. After the leveling compound has hardened and, if necessary, can be reworked or sanded, the crack-free building wall or ceiling can then be painted with a suitable wall or ceiling paint. The multilayer wall coating system therefore in any case comprises a leveling compound layer, which is applied in sections in the area of unevenness in the wall, and a wall coating above it. If necessary, an additional reinforcement layer can also be present in such a wall coating system. For the sake of simplicity, the following is briefly referred to as a wall paint, provided that a wall or ceiling coating is meant with a paint. Furthermore, the term wall coating system is used as soon as a multilayer / 39 P17285 Coating system for the wall or ceiling coating is meant, which relates to at least a portion of a leveling compound layer including a wall coating applied over it, wherein an additional reinforcement layer can optionally form a further layer of the wall coating system. There are only standardized test methods for determining the crack bridging capacity of coatings for mineral substrates and concrete outdoors (DIN EN 1062-7) as well as for plastic-modified bitumen thick coatings for waterproofing buildings (DIN EN 15812). However, these test methods are not suitable for assessing the elasticity and crack bridging ability of wall coatings or multi-layer wall coating systems, since the coating materials to be tested do not withstand the loads caused by the measuring devices established for the aforementioned tests. In addition, these unsuitable test methods would not provide comparable, accurate measurements of the elasticity and crack bridging ability when testing such wall coatings or multi-layer wall coating systems. Currently, these parameters for wall coatings or multi-layer wall coating systems are only estimated on the basis of empirical values and information from processors such as master painters. A method for determining mechanical properties of thin layers has become known from the prior art from document DE 19802716 C2, in which a three-point bending test is used to determine the yield strength, tensile strength, fracture toughness and modulus of elasticity of thin layers Layers that are applied to a metallic specimen made of high-strength steel as the carrier material. However, this method has been developed for testing thin layers, such as those used in mechanical engineering, and is not suitable as a test method in the construction industry, among other things, because of the metallic substrate material that is completely unsuitable for wall coatings or wall coating systems. Furthermore, a notch remains there, which is provided for weakening or as a crack starter for a fatigue crack in the carrier material, during the coating test. Furthermore, a test specimen for determining the crack bridging method of paint systems on silicate substrates has become known from the prior art from the publication DD 266 175 A1. A creep test rig with a prismatic test specimen is used, which consists of a silicate building material and which is reinforced with a modified reinforcing steel rod with a reduced diameter in the middle. This test specimen is subjected to a tensile test so that cracks appear on its surface. The test specimen is then coated with an emulsion paint and subjected to a further long-term tensile test after it dries out. The crack bridging behavior of the coating with emulsion paint and the determination of the crack opening profiles / 39 P17285 is based on the expansion of the reinforcing steel rod. However, a stretchability measurement is not possible with this creep test bench. In addition, the strain measurement of the reinforcing steel reinforcement takes place optically without any measurement data acquisition. There has therefore long been an urgent need to develop a test method that provides accurate and reliably reproducible measurement values for the elasticity and crack bridging ability of wall coatings or interior coatings or of multi-layer wall coating systems. Such a test method is also of great economic interest, since on the basis of comparable, reproducible measured values with regard to elasticity and crack bridging ability, the selection of suitable wall coatings or wall coating systems, for example for the renovation of old buildings, is to be made easier in the future, thereby also saving renovation costs for the interior renovation of buildings. The present invention therefore has the task of avoiding the disadvantages known from the prior art and of specifying a strain measurement method which is suitable for determining the extensibility and crack bridging capacity of wall paints or wall coating systems. According to the invention, a strain measurement method for determining the stretchability of thin layers of a wall paint or a multi-layer wall coating system comprises the following steps: Provision of a bending beam made of an absorbent material, the bending beam having a beam length and a rectangular cross section with a beam width and with a beam thickness; -b- arranging a notch on a broad side of the bending beam in the middle of the length of its beam length and transversely to the longitudinal direction of the bending beam, the notch having a notch depth and a notch width and extending over the entire beam width; optionally - after a first test arrangement -c1- applying a wall paint along a section with a sample layer length on the smooth broad side of the bending beam opposite the notched broad side on both sides of the length center of its beam length; or - alternatively after a second test arrangement -c2- applying a multi-layer wall coating system along a section with a sample layer length on the notched broad side of the bending beam on both sides of the length center of its beam length; as well as further -d- arranging measuring points in at least one sample length interval of the sample layer length of the applied wall coating or of the multi-layer wall coating system; / 39 P17285 recording at least one initial length as a distance measure between measuring points of the at least one sample length interval on the undeformed bending beam; -f- performing a three-point bending test with a tester, the Bending beam is positioned on two side supports in such a way that the side coated with the wall paint or the multi-layer wall coating system is oriented towards the side supports and is opposite a test stamp in the middle of the length of the bending beam; -g- Recording the bending deformation of the bending beam during the three-point bending test with an industrial camera which captures the coated side of the bending beam opposite the central test stamp; -h- End the three-point bending test as soon as a crack formation with hairline cracks in the wall coating or in the multi-layer wall coating system is detected in a cracking zone on the coated side of the bending beam; Determine the change in length Al of the wall paint or wall coating system applied to the bending beam as the difference of at least one condition length in the event of crack formation, which condition length is obtained as a distance measure between measuring points of the at least one sample length interval in the case of crack formation on the deformed bending beam, and the initial length of the at least one sample length interval on the undeformed bending beam , The test method according to the invention for determining the extensibility of thin layers of a wall paint or a multi-layer wall coating system is comparable in terms of the experimental setup with the three-point bending test according to DIN EN ISO 178 with the title "Plastics - Determination of the Bending Properties". The structure of the three-point bending test also serves to achieve a bending of a bending beam in order to test a coating applied thereon when carrying out the strain measurement method according to the invention. In the strain measuring method according to the invention, a bending beam made of an absorbent material is first provided according to method step -a-, the bending beam having a beam length and a rectangular cross section with a beam width and with a beam thickness. The absorbent material for the production of the bending beam should have the same or similar properties as far as possible with regard to its absorbency and its bending stiffness as a mineral substrate, for example an interior masonry provided with lime plaster or cement plaster, on which wall paints or multi-layer wall coating systems are usually applied. In the preliminary tests, drywall boards, in particular cement-bonded particle boards, have proven to be a suitable carrier material for such a bending beam. Then, according to method step -b-, a notch is made on a broad side of the bending beam in the middle of the length of its beam length and transversely to the longitudinal direction of the bending beam / 39 P17285 arranged. The notch has a defined notch depth and a defined notch width and runs across the entire beam width. The notch leads to a conscious weakening of the bending beam. This means that during the bending deformation, the bending beam is stretched particularly strongly in the area of the notch. Alternatively, two different test arrangements can be realized with the strain measuring method according to the invention. According to method step -c1-, according to a first test arrangement, a wall coating is applied along a section with a sample layer length on the smooth broad side of the bending beam, which is opposite the notched broad side. The wall paint is applied to the smooth broadside on both sides of the middle along a section of its beam length. With this first test arrangement, a wall or ceiling coating is simulated, such as that which is applied, for example, to a smooth or previously smoothed wall surface of an interior of a building as a conventional wall coating. For example, dispersion paints, latex paints, silicate paints or lime paints can be used as wall paints. As a result of the arrangement of the notch on the broad side opposite the wall coating, a concentrated expansion formation takes place in the area of the notch in the middle of the length of the bending beam during the test process. That area of the wall paint that is applied on the smooth broad side opposite the notch is particularly strongly deformed by bending expansion. The crack formation in the wall coating on the smooth broad side of the bending beam is thus advantageously limited to a narrow crack formation zone, which can be detected particularly precisely with an industrial camera during the bending deformation. As will be explained in more detail below, the stretchability ε of the wall coating tested can be determined using this first test arrangement. As an alternative to method step -c1-, a multi-layer wall coating system can be tested in a method step -c2- according to a second test arrangement. This multi-layer wall coating system is applied along a section with a sample layer length on the notched broad side of the bending beam on both sides of the middle of its length. In contrast to a simple wall coating to be tested, the multi-layer wall coating system is therefore deliberately applied to the notched broad side of the bending beam. The notch in the cantilever simulates a crack or crack in the masonry using the strain measurement method, which has to be filled before applying a coat of paint. For this purpose, a leveling compound, which is intended for use in construction, in particular in drywall construction, is applied to fill the notch on the notched broad side of the bending beam with a layer height or layer thickness of the leveling compound. Common fillers for filling cracks and cracks in the masonry of the inner walls or ceilings of a building usually contain binders such as gypsum (calcium sulfate dihydrate) or a co-polymer. / 39 P17285 In addition, it may be necessary to insert a reinforcing layer, for example a joint cover strip made of a glass fleece, into the filler in order to increase the tensile strength of the filler in the dried, hardened state. Optionally, it is also possible to use the strain measurement method to test wall coating systems that are reinforced with one or more reinforcement layers. After the filler has hardened, which may also be reinforced with a reinforcing layer, and an optional further processing step, in which the filler is still smoothed or sanded, a wall coating is finally applied to the filler as a top layer of the wall coating system. Due to the arrangement of the wall coating system on the notched broadside, a concentrated strain deformation occurs in the area of the notch in the center of the length of the bending beam during the test process. That area of the wall coating system which is applied to the notched broadside in the area directly adjacent to the notch is thereby particularly strongly deformed. The crack formation in the wall coating system on the notched broad side of the bending beam is thus advantageously restricted to a narrow crack formation zone in the area of the spackled notch, which in turn can be recorded particularly precisely with an industrial camera during the bending deformation. As will be explained in detail below, this second test arrangement can be used to determine both the extensibility ε of the multi-layer wall coating system tested and its crack bridging capacity. The subsequent further process steps -d- to -i- are each carried out analogously for the two different test arrangements. According to method step -d-corresponding measuring points are applied in at least one sample length interval of the sample layer length of the applied wall coating or the multi-layer wall coating system. The interval sections of one or more sample length intervals are each applied symmetrically from the center of the length of the bending beam in its longitudinal direction. Due to the notch on one of the two broad sides, the middle of the length of the bending beam is the critical weak point of the bending beam, where the cracking zone occurs first during the bending deformation. According to method step -e-, an exact detection and recording of the initial lengths of the sample length intervals is then carried out on the still undeformed bending beam as distance measurements between measuring points of the corresponding sample length intervals. In the subsequent process step -f-, a three-point bending test is carried out with a corresponding test device, the bending beam being positioned on two side supports in such a way that the side coated with the wall paint or the multi-layer wall coating system is oriented towards the side supports and one in the middle of the length of the bending beam lies the central test stamp. The person to be examined / 39 P17285 Bending beam is thus inserted into the test device in such a way that the test punch arranged in the center of the bending beam, which is positioned on the opposite side of the two supports of the testing device, presses on the uncoated or uncoated broad side of the bending beam. The wall coating to be tested or the wall coating system to be tested is therefore located on the broad side of the bending beam opposite the center of the test stamp and facing away from it, which is stretched during the bending deformation. The test device for applying force during the bending deformation is expediently equipped with supports and with a test stamp which have test bench rollers as roller bearings. This ensures a torque and displacement-free mounting or bending load of the bending beam during the bending deformation. Such test bench rolls for storage on the two supports and at the free end of the test punch each have the same dimensions - i.e. the same roll diameter and a cylinder length that corresponds at least to the beam width of the bending beam and are advantageously made of the same material, for example of metal, preferably made of steel. According to method step -g-, the crack formation in the wall coating to be tested or in the wall coating system to be tested is recorded with an industrial camera during the three-point bending test, that is to say during the bending deformation of the bending beam. The industrial camera captures the coated side of the bending beam opposite the central test stamp. For this purpose, the crack formation during the bending deformation of the bending beam is expediently recorded using an optical deformation analysis by means of digital image correlation (in short: DIC, digital image correlation). This requires an industrial camera that records the deformation on the bending beam to be tested during the bending process, and appropriate measuring software that stores and evaluates the recorded deformations and displacements. These components - i.e. the industrial camera including the associated measurement software, a corresponding measurement computer for recording, storing and evaluating the measurement data as well as the cabling required for the signal connection of the individual components - form a so-called video extensometer. The mode of operation and the construction of such a video extensometer are known to the person skilled in the art in the field of strain measurement methods. The video extensometer uses the video extensometer to determine length displacements or elongations due to the bending deformation of the bending beam using measuring points that are applied to the bending beam in the desired measuring range of the sample layer length of the wall coating or the wall coating system. These measurement points are advantageously selected or are designed such that they can be detected in the representation of the industrial camera as a gray value pattern or speckle pattern. / 39 P17285 The measurement points are particularly expediently applied in several sample length intervals on both sides of the length center of the bending beam in the area of the sample layer length. For example, by default, a first sample length interval is selected such that its interval length corresponds to one tenth of the total beam length of the bending beam. A second sample length interval is selected, for example, in such a way that its interval length corresponds to a third of the total beam length of the bending beam. In the case of the second test arrangement, i.e. if a multi-layer wall coating system is applied to the notched broad side of the bending beam, a third sample length interval is expediently applied with measuring points on the wall coating system in such a way that the measuring points directly adjoin the spackled notch. The crack bridging capacity of the wall coating system can be determined with this third sample length interval, the interval length of which corresponds approximately to the sum of the notch width and twice half the measuring point width. According to process step -h-, the three-point bending test is terminated as soon as the industrial camera or the video extensometer detects crack formation with hairline cracks in the wall coating or in the multi-layer wall coating system in a cracking zone on the coated side of the bending beam. Finally, according to method step -i-, the change in length A L of the wall coating or wall coating system applied to the bending beam is determined as the difference of at least one condition length in the event of crack formation, which condition length is obtained as a distance measure between measuring points of the at least one sample length interval in the event of crack formation on the deformed bending beam, and the initial length of the at least one sample length interval on the undeformed bending beam. There is therefore a comparison of the state lengths of one or more sample length intervals with already recognizable crack formation after the bending deformation with the correlating sample length intervals before the bending deformation of the bending beam. With a strain measurement method according to the invention, the stretchability ε of the wall coating tested or the multi-layer wall coating system can advantageously be determined by calculation as the ratio of the change in length AL of the bending beam to the original initial length, the change in length AL being expressed as the difference between the deformed state length when the crack is formed and the original initial length. To calculate the maximum elasticity ε (in [%]) of the wall coating tested or the multi-layer wall coating system, first change the length AL of the bending beam (in [mm]) as the difference between the deformed state length L 1 when the crack is formed and the original initial length Lo before the bending deformation calculated using the following formula (1): Al = L1 - Lo in [mm] (1) / 39 P17285 According to the following formula (2), the extensibility ε of the wall coating tested or the multi-layer wall coating system is expressed as the ratio of the change in length Al of the bending beam to the original initial length Lo: ε = (Al / Lo) * 100 in [%] (2) Advantageously, with a strain measurement method according to the invention, the crack bridging capacity LR of the multi-layer wall coating system tested can also be calculated as the difference between the deformed state length of the sample length interval in the case of crack formation, which sample length interval has measuring points directly adjacent to the notch, and the original starting length of this sample length interval with measuring points directly adjacent to the notch. For the determination of the crack bridging capacity of the tested multi-layer wall coating system with the second test arrangement, i.e. if a multi-layer wall coating system is applied to the notched broad side of the bending beam, a third sample length interval is applied to the wall coating system with measuring points, the measuring points of this third sample length interval being directly overlapped to the overlapped Adjacent notch. With this third sample length interval, the interval length of which corresponds approximately to the sum of the notch width plus twice the value of half the measuring point width of the measuring points directly adjacent to the notch, the crack bridging capacity LR (in [mm]) of the wall coating system can be calculated as the difference between the deformed state length Lr3 of the sample length interval and crack formation , which sample length interval has measuring points directly adjacent to the notch, for the original starting length LP3 of this sample length interval with measuring points directly adjacent to the notch, are calculated according to the following formula (3): Lr = Lr3 - Lp3 in [mm] (3) In a strain measurement method according to the invention, the deformed length of state in the event of cracks forming in hairline cracks in the wall paint or in the multi-layer wall coating system with a crack opening of at least 0.2 mm can be determined particularly expediently. Hairline cracks with a crack opening of at least 0.2 mm have the advantage that they can already be recognized with the naked eye. In addition, this measure of crack openings has already been reflected in standards. For example, according to DIN 18550-1 ("Planning, preparation and execution of interior and exterior plasters"), cracks are only designated as optical and / or technical defects from a width of 0.2 mm. With the help of the industrial camera or the video extensometer, the subsequent evaluation of the bending deformation of the bending beam can be used to determine the point in time at which cracking occurred, in which the corresponding hairline cracks with a crack opening of 0.2 mm first appeared in the cracking zone. This at the time during the bending deformation / 39 P17285 related condition lengths Li are then, as described above, for further evaluation to determine the elasticity or the crack bridging assets herangezog en · In a particularly expedient variant of the strain measurement method according to the invention, the bending beam can have a beam thickness of 10 mm to 40 mm, preferably 20 mm to 28 mm, particularly preferably 24 mm. In preliminary tests, these bar thicknesses have proven to be particularly useful for carrying out the bending test. On the one hand, such bending beams are still thin enough to be handled by one person. On the other hand, such bending beams are sufficiently thick to be able to arrange a continuous notch transversely to the longitudinal direction of the bending beam on a broad side of the bending beam. It can be advantageous if, in a strain measurement method according to the invention, the bending beam has a beam width that corresponds to three times the value of the beam thickness, and a beam length that corresponds to twelve times the value of the beam thickness. For example, bending beams are particularly expediently used, which have a beam length of 300 mm, a beam width of 75 mm and a beam thickness of 24 mm. In a strain measurement method according to the invention, the bending beam can expediently have a notch with a notch depth which is from 20% to 80% of the beam thickness, preferably from 40% to 60% of the beam thickness, particularly preferably 50% of the beam thickness. It is essential that the selected notch depth in the two test arrangements does not impair the load-bearing capacity of the bending beam, so that the beam fails before the test procedure due to its own weight or undergoes bending deformations. In a further advantageous embodiment, in a strain measurement method according to the invention, the bending beam can have a notch with a notch width of 2 mm to 4 mm. A notch with this notch width can expediently be arranged on the bending beam, for example using a circular saw. It can be particularly advantageous if, in a strain measuring method according to the invention, the bending beam is made from a composite panel containing wood and cement. Preliminary tests have shown that such so-called cement-bonded particle boards are particularly suitable as composite materials as bending beams, since they advantageously have a suction behavior similar to that of mineral plaster and have sufficient strength and good workability. A bending beam is expediently used in a strain measuring method according to the invention, the - from 50% by volume to 70% by volume of wood or wood chips, - from 20% by volume to 40% by volume of cement, / 39 P17285 - from 7% by volume to 15% by volume of bound water and - Contains from 0% by volume to 3% by volume of additional hydration additives. Composite panels with such a composition, which contain cement as a hydraulic binder and possibly further additional binders as hydration additives, offer the advantage of being sufficiently absorbent to apply a wall paint or a multi-layer wall coating system and of having sufficient flexural rigidity in order not to be undesirable Way to deform before the test due to their own weight. The above-mentioned objects of the invention are also achieved with a test setup for carrying out a strain measurement method according to the invention. According to a first test arrangement, a test setup according to the invention for carrying out a strain measurement method for determining the stretchability of thin layers of a wall paint comprises - A bending beam and a test device equipped with an industrial camera and measuring software for carrying out a three-point bending test, the industrial camera being designed to record the deformation on the bending beam to be tested during the bending process, and the measuring software being designed for this is to save and evaluate the recorded deformations and displacements; in which - The bending beam is made of an absorbent material, has a beam length and a rectangular cross-section with a beam width and with a beam thickness, wherein a notch is arranged on a broad side of the bending beam in the middle of the length of its beam length and transversely to the longitudinal direction of the bending beam, the notch has a notch depth and a notch width and runs across the entire width of the bar; such as - A wall coating is applied along a section with a sample layer length on the smooth broad side of the bending beam opposite the notched broad side, on both sides of the middle length of its beam length; as well as further Measuring points are arranged in at least one sample length interval of the sample layer length of the applied wall coating; in which - At least one output length is recorded as a distance measure between measuring points of the at least one sample length interval on the undeformed bending beam; in which - The bending beam for carrying out a three-point bending test is positioned on two lateral supports of the test device in such a way that the side coated with the wall paint is oriented towards the lateral supports and is opposite a test stamp of the test device arranged in the center of the length of the bending beam; where / 39 P17285 - The bending deformation of the bending beam is recorded during the three-point bending test with an industrial camera, which industrial camera captures the coated side of the bending beam opposite the central test stamp; such as - The test device is configured such that the three-point bending test ends as soon as the industrial camera detects cracking with hairline cracks in the wall coating in a cracking zone on the coated side of the bending beam. In an alternative configuration according to a second test arrangement, a test setup according to the invention for carrying out a strain measurement method for determining the stretchability of thin layers of a multi-layer wall coating system - Includes a bending beam and a test device equipped with an industrial camera and measuring software for carrying out a three-point bending test, the industrial camera being designed to record the deformation on the bending beam to be tested during the bending process, and the measuring software is to save and evaluate the recorded deformations and displacements; in which - The bending beam is made of an absorbent material, has a beam length and a rectangular cross-section with a beam width and with a beam thickness, wherein a notch is arranged on a broad side of the bending beam in the middle of the length of its beam length and transversely to the longitudinal direction of the bending beam, the notch has a notch depth and a notch width and runs across the entire width of the bar; such as - A multilayer wall coating system is applied along a section with a sample layer length on the notched broad side of the bending beam on both sides of the middle of its length; as well as further Measuring points are arranged in at least one sample length interval of the sample layer length of the applied wall coating; in which - At least one output length is recorded as a distance measure between measuring points of the at least one sample length interval on the undeformed bending beam; in which - The bending beam for carrying out a three-point bending test is positioned on two lateral supports of the test device in such a way that the side coated with the wall paint is oriented towards the lateral supports and is opposite a test stamp of the test device arranged in the center of the length of the bending beam; in which - The bending deformation of the bending beam is recorded during the three-point bending test with an industrial camera, which industrial camera captures the coated side of the bending beam opposite the central test stamp; and / 39 P17285 - The test device is configured such that the three-point bending test ends as soon as the industrial camera detects cracking with hairline cracks in the wall coating in a cracking zone on the coated side of the bending beam. As already stated at the beginning, certain components of the test device thus form the industrial camera together with the associated measurement software, a corresponding measurement computer for recording, storing and evaluating the measurement data, and any cabling required for the signal connection of the individual components - a so-called video extensometer. The mode of operation and the construction of such a video extensometer are known to the person skilled in the art in the field of strain measurement methods. The video extensometer uses the video extensometer to determine length displacements or elongations due to the bending deformation of the bending beam using measuring points that are applied to the bending beam in the desired measuring range of the sample layer length of the wall coating or the wall coating system in one or more sample length intervals. These measuring points are advantageously selected or are designed such that they can be detected in the representation of the industrial camera as a gray value pattern or speckle pattern. In an advantageous development of the invention, in a test set-up after the end of the three-point bending test, the measurement software of the test device can determine the change in length Al of the wall paint or wall coating system applied to the bending beam as the difference of at least one condition length in the event of cracking, which condition length is the distance between the measurement points of the at least one corresponds to a sample length interval in the case of crack formation on the deformed bending beam, and determine the starting length of the at least one sample length interval on the undeformed bending beam by calculation. With a test set-up according to the invention, the change in length A1 of the wall coating applied to the bending beam caused by the bending deformation can be determined in accordance with the first test arrangement for a wall coating to be tested. The elasticity ε of the wall coating tested can then be determined using the calculation scheme described above. With a test set-up according to the invention, the change in length A1 of the wall coating system applied to the bending beam, which is caused by the bending deformation, can also be determined for a multilayer wall coating system to be tested. Subsequently, the elasticity ε can also be determined for the multilayer wall coating system tested using the calculation scheme set out above. The crack bridging capacity of the tested multi-layer wall coating system can also be determined using the calculation scheme set out above. / 39 P17285 Further details, features and advantages of the invention result from the following explanation of exemplary embodiments shown schematically in the drawings. The drawings show: - Fig · 1 in a side view, a first test arrangement of Dehnmessverfahrens according to the Invention with a bending beam for testing the elasticity of a wall or ceiling paint; 1A is an enlarged detailed view of the first test arrangement shown in FIG. 1 in the starting position with an undeformed bending beam; FIG. 1B shows the first test arrangement shown in FIG. 1A after bending deformation of the bending beam; - Fi g · 2 in a side view a second test arrangement of the strain measuring method according to the invention with a bending beam for testing the extensibility and crack bridging ability of a multi-layer wall or ceiling coating system; 2A shows an enlarged detailed view of the second test arrangement shown in FIG Starting position with an undeformed bending beam; 2B shows the second test arrangement shown in FIG. 2A after a bending deformation of the bending beam; - Fi g. 3 an isometric view obliquely from the front of a bending beam with a notch in the middle and transverse to the longitudinal direction of the bending beam; - Fi g. 4 shows a schematic side view of the test setup of a bending beam strain measuring method using a high-resolution industrial camera; - Fi g. 5 shows a plan view of the smooth broad side of a bending beam prepared for the first test arrangement of the strain measuring method according to the invention; FIG. 5A shows the bending beam shown in FIG. 5 together with one applied to it Wall or. Ceiling painting and applied measuring points; - Fi g. 6 is a top view of the notched broad side of a bending beam prepared for the second test arrangement of the strain measuring method according to the invention; - Fig. 6A shows the bending beam shown in Fig. 6, including one applied to it Wall or ceiling coating system and applied measuring points. Fig. 1 shows a first test arrangement of the strain measuring method according to the invention with a bending beam 1 for testing the extensibility of a wall or ceiling paint 20, which for the sake of simplicity will be referred to as wall paint 20 below, as is evidently also the case for painting by others Building parts such as can be used for painting building ceilings. The bending beam 1 has a beam length L, a beam width B and a beam thickness D or material thickness. The bending beam 1 is made here, for example, from a cement-bonded particle board, which is particularly advantageously suitable as an absorbent carrier material for a wall paint 20. For example, the bending beam shown here has 1/39 P17285 a beam length L of around 300 mm, a beam width B of around 75 mm and a beam thickness D or material thickness of 24 mm. According to the first test arrangement illustrated in FIG. 1, a broad side 11 of the bending beam 1 has a notch 2 with a notch depth d and a notch width l in the middle of its longitudinal direction L / 2. The notched broad side 11 here forms the upper side of the bending beam 1 in FIG. 1. The notch depth d here is, for example, 50% of the beam thickness D of the bending beam 1, thus a notch depth d of 12 mm. The notch width l is measured in the longitudinal direction L of the bending beam 1 and is here, for example, 3 mm. The notch 2 runs on the notched broad side 11 of the bending beam 1 transversely to its longitudinal direction. The bending beam 1 is tested in a three-point bending test in the strain measuring method according to the invention, the three pressure points here each being designed as test bench rollers 4. For this purpose, the bending beam 1 is positioned on two spaced-apart supports 6, which are designed here as test bench rollers 4, and is loaded during the bending test in the middle between the two supports 6 with a test punch 5 with a bending force F and is deformed during the bending test. The bending force F acts in the direction of the arrow F perpendicular downward directly in the area of the notch 2. The notch 2 serves to weaken the material of the bending beam 1 and has the effect that the bending stress of the bending beam 1 during the bending test is specified in the area of the notch 2 and here the bending deformation due to compression of the notched broad side 11 is particularly high. It is thus achieved that on the smooth broad side 12 of the bending beam 1, which is shown here in FIG. 1 as the underside of the bending beam 1, the stretch on the smooth broad side 12 is particularly high in that area which is opposite the top notch 2. According to the first test arrangement, the notched broad side 11 is loaded with the test stamp 5 during the bending test. The side opposite the notched broad side 11 is referred to below as the smooth broad side 12 of the bending beam 1. The smooth broad side 12, which is positioned in FIG. 1 as the underside of the bending beam 1, faces away from the test stamp 5 during the three-point bending test and serves as a sample carrier side for the wall paints 20 or wall coatings 25 to be tested. In terms of a balance of forces during the bending test, half of the bending force F / 2 acts on the two supports 6. The test bench rollers 4 are each designed as metal rollers and each have a radius r. The supports 6 are set so that an edge distance x remains on the smooth broad side 12 between the roller axis of the test bench rollers 4 forming the supports 6 and the lateral bar edge of the bending beam 1, which corresponds here to one and a half times the radius r of the test bench rollers 4. The diameter of the test stand rollers 4 is selected here such that it corresponds approximately to the beam thickness D or material thickness of the bending beam 1. The length of the test bench rollers 4 corresponds at least to the beam width B of the bending beam 1. / 39 P17285 In the first test arrangement of the strain measurement method sketched in FIG. 1, a wall coating 20 with a layer height is applied to the smooth broad side 12 of the bending beam 1, which, according to FIG. 1, is the underside of the bending beam 1 and the notched broad side 11 on the upper side of the bending beam 1 h and with a sample layer length Lp. The area of the wall paint 20 is chosen such that the sample layer length LP is applied symmetrically on both sides of the center L / 2 of the bending beam 1 and extends in the longitudinal direction about half the beam length L of the bending beam 1. Or in other words: Starting from the edge of the beam on the narrow sides of the bending beam 1, about a quarter of the total length of the beam L of the smooth broad side 12 remains free of the wall coating 20 to be tested. What is essential, however, is that the wall coating 20 in the area of the middle L / 2 of the bending beam 1 is applied and thus lies opposite the area of the notched broad side 11 of the bending beam 1 provided with the notch 2. FIG. 1A shows an enlarged detailed view of the first test arrangement shown in FIG. 1 in the starting position with the bending beam 1 still undeformed. Before the stretch measurement process begins, 20 markings are arranged on the wall coating, which are applied symmetrically in the longitudinal direction on both sides of the length center L / 2 of the bending beam 1 become. The center of length L / 2 of the bending beam 1 corresponds to the weakening zone of the notch 2 on the opposite notched broad side 11 of the bending beam. For this purpose, a first sample length interval LP1 and a second sample length interval LP2 are expediently applied to the wall paint 20. The first sample length interval LP1 corresponds to a tenth of the total bending beam length L. The second sample length interval LP2 corresponds to a third of the total bending beam length L. Using markings, initial lengths L0 can be measured on the still undeformed bending beam 1 before the start of a bending deformation. FIG. 1B shows the first test arrangement shown in FIG. 1A after a bending deformation of the bending beam 1. For this purpose, the bending beam 1 is loaded with a bending force F in the middle between the two supports 6 with the test stamp 5 and is deformed during the bending test. Because of the notch 2 on the notched broad side 11 of the bending beam 1, the deformation by the bending force F is concentrated in the area of the notch 2. The notched broad side 11 of the bending beam 1 is thus particularly strongly compressed in the area of the notch 2. As already mentioned above, conversely, that area of the wall paint 20 on the smooth broad side 12 which is opposite the notch 2 is stretched particularly strongly during the deformation. During the deformation, a cracking zone R is formed in the wall coating 20, starting in this area, which is particularly stressed by stretching, on the smooth broad side 12 of the bending beam 1. Thus, during the bending test, first cracks in the wall paint occur particularly advantageously first in this section on the smooth broad side 12 of the bending beam 1, which is opposite the notch 2. This crack formation zone R is defined as a zone with first hairline cracks in the wall paint 20, which has a crack width of greater / 39 P17285 or equal to 0.2 mm and are therefore already visible to the naked eye as cracks in the wall paint. In order to be able to observe the crack formation in real time if possible, a high-resolution industrial camera is expediently used to document the bending test. The changes in length of the previously recorded output lengths L0 or the previously recorded lengths of the sample length intervals LP1, LP2 are also recorded by the industrial camera. The originally recorded length dimensions and initial lengths in the undeformed state before the bending deformation of the bending beam 1 can advantageously be compared with those enlarged sample length intervals LR1, LR2 at the time when crack formation in the crack formation zone R is already recognizable after the bending deformation of the bending beam 1 has taken place. The first sample length interval LR1 if crack formation has already occurred after the bending deformation corresponds to a first sample length interval LP1 which has been enlarged by bending deformation. Analogously to this, the second sample length interval LR2 in the case of crack formation that has already occurred after the bending deformation of the bending beam 1 corresponds to a second sample length interval LP2 that has been enlarged due to the bending deformation. The stretchability of the wall coating 20 tested can be determined with these measurement data obtained in the first measurement arrangement. 2 shows a second test arrangement of the strain measurement method according to the invention with a bending beam 1 for testing the extensibility and the crack bridging capacity of a multi-layer wall or ceiling coating system 25, which here comprises a filler 21 and a wall paint 20 applied to the filler 21. The wall or ceiling coating system 25 is briefly referred to below as the wall coating system 25, as this is also suitable for coating other parts of the building, such as building ceilings. According to the second test arrangement illustrated in FIG. 2, the notched broad side 11 of the bending beam 1 has a notch 2 with a notch depth d and a notch width l in the length center L / 2 transverse to its longitudinal direction. The notch depth d here is, for example, 50% of the beam thickness D of the bending beam 1, thus a notch depth d of 12 mm. The notch width l is measured in the longitudinal direction L of the bending beam 1 and is here, for example, 3 mm. The notch 2 runs on the notched broad side 11 of the bending beam 1 transversely to its longitudinal direction. The notched broad side 11 is located in FIG. 2 on the underside of the bending beam 1. The notch 2 is also used here for the targeted weakening of the material of the bending beam 1 in order to achieve a particularly strong elongation of the notched broad side 11 during the bending test in the region of the notch 2. Furthermore, the notch 2 in the second test arrangement serves as a model of an artificially generated crack in a building wall or ceiling, which is covered with a filler 21 before the application of a wall paint 20. For this purpose, in preparation for the bending test on the notched broad side 11 of the undeformed bending beam 1, that is to say on the side that carries the notch 2 and that in the following / 39 P17285 Bending test is opposite the test stamp 5, first filler 21 is applied with a layer height H or layer thickness. The notch 2 is also filled with the filler 21. For this purpose, the notch 2 is first filled in plan and then, after the filler 21 has hardened, the further filler layer 21 is applied in the notch 2. The filler 21 is applied flatly in the longitudinal direction L of the bending beam 1 at least along a section with a sample layer length LP. After the filler 21 has hardened, a wall paint 20 with a layer height h or layer thickness is then applied to the already hardened filler 21. The combination of a layer of a filler 21 and one or more layers of a wall paint 20 is referred to as a wall coating system 25. FIG. 2A shows the second test arrangement shown in FIG. 2 in the starting position with an undeformed bending beam 1. In FIG. 2A, a reinforcement layer 22 made of a glass fiber fleece within the layer height H of the filler compound 21 is indicated. A wall coating system 25 can, for example, also include such a reinforcement layer 22, which is expediently designed as a glass fiber fleece and is usually inserted into the filler 21 approximately in the middle of the layer height H or layer thickness. For this purpose, a thin layer of filler 21 is first applied, which covers the notch 2. The reinforcement layer 22 can then be placed on top and covered with a further thin layer of the filler 21 in order to obtain a reinforced filler 21 with a layer height H. FIG. 2B shows the second test arrangement shown in FIG. 2A after a bending deformation of the bending beam 1. As already described above with reference to FIG. 1B, the bending beam 1 is also shown in FIG. 2B in the middle between the two supports 6 with the test stamp 5 loaded with a bending force F and deformed during the bending test. Because of the notch 2 on the notched broad side 11 of the bending beam 1, the deformation by the bending force F is concentrated in the area of the notch 2. The smooth broad side 12 of the bending beam 1, which forms the top of the bending beam in FIG. 2B, is thus particularly strongly compressed in the area of the notch 2. That area of the wall coating system 25 on the notched broad side 11 in the area of the notch 2 is stretched particularly strongly during the deformation. During the deformation, a crack formation zone R is formed in the wall coating system 25 in this area, which is particularly stressed by expansion, on the notched broad side 11 of the bending beam 1. Thus, during the bending test, first cracks in the wall coating 20 or in the filler 21 applied underneath occur particularly advantageously first in this section in the region of the notch 2 on the underside of the bending beam 1. This crack formation zone R is again defined as a zone with first hairline cracks in one or more layers of the wall coating system 25. By definition, hairline cracks here have a crack width of greater than or equal to 0.2 mm and are therefore already visible to the naked eye as cracks. / 39 P17285 In order to be able to observe the crack formation in real time as far as possible, an industrial camera is also expediently used here in the second test arrangement to document the bending test. Analogous to the first test arrangement, the changes in length of the previously recorded output lengths Lo or sample length intervals Lp1, Lp2, Lp3 are recorded by the industrial camera. For this purpose, a first sample length interval LP1 and a second sample length interval LP2 are expediently applied to the wall coating system 25 to be tested, analogously to the first test arrangement. The first sample length interval Lpi - analogous to the first test arrangement - again corresponds to one tenth of the total bending beam length L. The second sample length interval Lp2 again corresponds to one third of the total bending beam length L. In addition, a further, third sample length interval L P3 is applied as part of the test of the wall coating system 25 , which specifies the sample length section of the measuring points which directly adjoin the notch 2. The third sample length interval Lp3 thus corresponds to the notch width l and twice the value of half the spacing width of the distance of a measuring point from the notch 2. Using appropriate measuring point markings, the starting lengths L0 can be measured on the still undeformed bending beam 1 before the start of a bending deformation. The originally recorded length dimensions and initial lengths in the undeformed state before the bending deformation of the bending beam 1 can advantageously be compared with those enlarged sample length intervals LR1, LR2, LR3 at the time when crack formation begins in the crack formation zone R after the bending deformation of the bending beam 1 has taken place. The first sample length interval LR1 in turn corresponds to the sample length interval LP1 if crack formation has already occurred after the bending deformation. The second sample length interval LR2 corresponds to the sample length interval LP2 if crack formation has already occurred after the bending deformation of the bending beam 1. Likewise, the third sample length interval LR3 shows if the crack formation has already occurred after the bending deformation of the bending beam 1, the change in the notch width 1 compared to the original sample length interval LP3 on the undeformed bending area. With these measurement data obtained in accordance with the second test arrangement, the extensibility and the crack bridging capacity of the wall coating system 25 under test can be determined. 3 illustrates a bending beam 1 with a notch 2 transverse to the longitudinal direction L of the bending beam 1. The bending beam 1 shown here is made from a cement-bonded particle board, which is particularly advantageous as an absorbent carrier material for applying a wall coating 20 to be tested and / or a wall coating system 25 is suitable. FIG. 4 shows a schematic side view of the test setup of a bending beam strain measurement method according to the first test arrangement using a high-resolution industrial camera 7. For this purpose, the industrial camera 7 is, for example, below the bending beam 1/39 P17285 and mounted at a distance from it in the area between the two supports 6. In this position, the industrial camera 7 ensures an unrestricted view of the smooth broad side 12 of the bending beam 1 together with the wall coating 20 to be tested. As already explained above, according to the first test arrangement, the bending beam 1 with the wall coating 20 to be tested is prepared so that the wall coating 20 is applied to the smooth broad side 12 of the bending beam 1. After the wall paint 20 has hardened and after corresponding sample length intervals Lp1, Lp2, Lp3 have been arranged on the wall paint 20 by means of measuring points M, the bending beam 1 is positioned in the test device in such a way that the wall paint 20 is oriented towards the industrial camera 7. For the sake of simplicity, the other components in addition to the industrial camera 7 for measuring data acquisition and evaluation - that is, a corresponding measurement data computer for recording, storing and evaluating the measurement data and any cabling required for signal connection of the individual components - are in simplicity Fig. 4 is not explicitly shown. The industrial camera 7 therefore also symbolizes here other required components and devices which are known to the person skilled in the art and which are used together as a video extensometer for detecting strain measurements. With this test setup, as shown in FIG. 4, a wall coating system 25 to be tested according to the second test arrangement can of course also be measured. The arrangement of the bending beam 1 required for this corresponds to the view in FIG. 2. As already explained above, according to the second test arrangement, the bending beam 1 is prepared with the wall coating system 25 to be tested in such a way that the wall coating system 25 is applied to the notched broad side 11 of the bending beam 1 becomes. After the wall coating system 25 has hardened and after corresponding sample length intervals LP1, LP2, LP3 have been arranged on the wall coating system 25 by means of measuring points M, the bending beam 1 is positioned in the test device such that the wall coating system 25 is oriented toward the industrial camera 7. FIG. 5 shows the smooth broad side 12 of a bending beam 1 prepared for the first test arrangement of the strain measuring method according to the invention. The view of FIG. 5 therefore corresponds to the bottom view of the bending beam 1 illustrated in FIG. 1. The notch 2 is here in FIG Rear side, that is to say arranged on the notched broad side 11 of the bending beam 1 opposite the smooth broad side 12. FIG. 5A shows the bending beam 1 shown in FIG. 5 together with the wall coating 20 applied to it on the smooth broad side 12 along a sample layer length LP. There are several measuring points M on the wall coating for detecting the changes in length of the output lengths L0 detected thereby, corresponding to the sample length intervals LP1 or LP2, attached with an industrial camera. In the undeformed state, the originally recorded initial lengths Lo can advantageously be compared with those / 39 before the bending deformation of the bending beam 1 P17285 State lengths Li of the sample length intervals Lri, Lr2 enlarged by bending deformation can be compared at the time when cracking has occurred in the cracking zone R of the bending beam 1. The change in length Al of the wall coating 20 applied to the bending beam 1 caused by the bending deformation is determined in this way. The elasticity ε of the wall coating 20 tested can then be determined on the basis of the calculation scheme set out above. FIG. 6 shows the notched broad side 11 of a bending beam 1 prepared for the second test arrangement of the strain measuring method according to the invention. The view of FIG. 6 therefore corresponds to the bottom view of the bending beam 1 illustrated in FIG. 2. The notch 2 is here in FIG visible broad side 11 of the bending beam 1 is arranged. FIG. 6A shows the bending beam 1 shown in FIG. 6 together with the wall coating system 25 applied thereon on the notched broad side 11 along a sample layer length Lp, which here comprises, for example, a layer of filler 21, which is covered by a wall paint 20. A number of measuring points M for detecting the changes in length of the previously recorded output lengths L0 or sample length intervals Lp1, Lp2, Lp3 are again mounted on the wall paint 20 with an industrial camera. The originally recorded length dimensions and initial lengths in the undeformed state before the bending deformation of the bending beam 1 can advantageously be compared with those enlarged state lengths L1 of the sample length intervals LR1, LR2, LR3 after the bending deformation of the bending beam 1 has taken place, that is to say when crack formation has already occurred in the crack formation zone R. The change in length Al of the wall coating system 25 applied to the bending beam 1 caused by the bending deformation is determined in this way. The extensibility ε of the multilayer wall coating system 25 tested can then be determined by calculation. Likewise, the crack bridging capacity of the multilayer wall coating system 25 tested can be determined on the basis of the calculation scheme set out above. / 39 P17285 List of reference numbers 124567111220212225BDdFF / 2HHLL / 2lLpLoLilpiLp2Lp 3lRILr2lr3MR bending beamscoreTest bench roll test stamp supportindustrial cameranotched broadside of the cantilever smooth broadside of the cantilever painted wall or ceilingPutty reinforcement layer Wall coating system Beam width of the bending beam Beam thickness or material thickness of the bending beam Notch depthbending forceHalf of the bending forceLayer height or layer thickness of the fillerLayer height or layer thickness of the wall coatingBeam length of the bending beam Center of length of the bending beamNotch width in the longitudinal direction of the bending beam sample layer lengthInitial length before the bending formation, corresponds to Lp1, Lp2 or Lp3 state length in the event of crack formation, corresponds to Lr1, Lr2 or Lr3 sample length interval 1 before the bending deformation; 1/10 of the bending beam length L sample length interval 2 before the bending deformation; 1/3 of the bending beam length L sample length interval 3 before bending deformation sample length interval 1 for crack formation after bending deformation sample length interval 2 for crack formation after bending deformation sample length interval 3 for crack formation after bending deformation measuring pointCracking zone; Zone with hairline cracks r Radius of the test bench roll x margin / 39 P17285
权利要求:
Claims (13) [1] claims 1. Strain measurement method for determining the stretchability of thin layers of a Wall painting (20) or a multi-layer wall coating system (25), characterized by the following steps: -a- Providing a bending beam (1) made of an absorbent material, the bending beam (1) having a beam length (L) and a rectangular cross section with a beam width (B) and with a beam thickness (D); -b- Arranging a notch (2) on a broad side (11) of the bending beam (1) in the middle (L / 2) of its beam length (L) and transversely to the longitudinal direction of the bending beam (1), the notch (2) one Notch depth (d) and a notch width (l) and extends over the entire bar width (B); optionally - after a first test arrangement -c1- applying a wall paint (20) along a section with a sample layer length (LP) on the smooth broad side (12) of the bending beam (1) opposite the notched broad side (11) on both sides of the center length (L / 2 ) its bars are long (L) ; or - alternatively after a second test arrangement -c2- applying a multi-layer wall coating system (25) along a section with a sample layer length (LP) on the notched broad side (11) of the bending beam (1) on both sides of the length center (L / 2) of its beam length (L ); as well as further -d- arranging measuring points (M) in at least one sample length interval (LP1, LP2, LP3) of the sample layer length (LP) of the applied wall paint (20) or of the multi-layer wall coating system (25); -e- Recording at least one initial length (L0) as a distance measure between measuring points (M) of the at least one sample length interval (LP1, LP2, LP3) on the undeformed bending beam (1); -f- performing a three-point bending test with a tester, the Bending beam (1) is positioned on two side supports (6) in such a way that the side coated with the wall paint (20) or the multi-layer wall coating system (25) is oriented towards the side supports (6) and one in the middle (L / 2 ) of the bending beam (1) opposite the central test stamp (5); -g- recording the bending deformation of the bending beam (1) during the three-point bending test with an industrial camera (7) which captures the coated side of the bending beam (1) opposite the central test stamp (5); -h- End the three-point bending test as soon as a crack formation with hairline cracks in the wall coating (20) or in the multi-layer wall coating system (25) is detected in a crack formation zone (R) of the coated side of the bending beam (1); 24/39 P17285 -i- Determine the change in length Al of the wall paint (20) or wall coating system (25) applied to the bending beam (1) as the difference of at least one condition length (L1) in the event of cracking, which condition length (L1) as a distance measure between measuring points (M) of the at least one sample length interval (Lr1, Lr2, Lr3) is obtained in the event of crack formation on the deformed bending beam (1), and the initial length (L0) of the at least one sample length interval (LP1, LP2, LP3) on the undeformed bending beam (1). [2] 2. Strain measurement method according to claim 1, characterized in that the extensibility ε of the wall coating (20) or the multi-layer wall coating system (25) tested is calculated as the ratio of the change in length Al of the bending beam (1) to the original initial length (L0), the change in length Al is expressed as the difference between the deformed state length (L1) and the original starting length (L0) when cracks develop. [3] 3. Strain measurement method according to claim 1 or 2, characterized in that the crack bridging capacity of the tested multilayer wall coating system (25) as a difference from the deformed state length (L1) of the sample length interval (Lr3) in the event of cracking, which sample length interval (Lrs) directly to the notch (2) has adjacent measuring points (M), the original starting length (L0) of this sample length interval (LP3) is calculated with measuring points (M) directly adjacent to the notch (2). [4] 4. Strain measurement method according to one of claims 1 to 3, characterized in that the deformed length of state (L1) in the case of cracks formation of hairline cracks in the wall paint (20) or in the multi-layer wall coating system (25) is determined with a crack opening of at least 0.2 mm. [5] 5. Strain measurement method according to one of claims 1 to 4, characterized in that the bending beam (1) has a beam thickness (D) from 10 mm to 40 mm, preferably from 20 mm to 28 mm, particularly preferably from 24 mm. [6] 6. Strain measuring method according to one of claims 1 to 5, characterized in that the bending beam (1) has a beam width (B) which corresponds to three times the value of the beam thickness (D), and has a beam length (L) which is twelve times the value corresponds to the bar thickness (D). [7] 7. Strain measurement method according to one of claims 1 to 6, characterized in that the bending beam (1) has a notch (2) with a notch depth (d) which is from 20% to 80% of the beam thickness (D), preferably from 40% up to 60% of the bar thickness (D), particularly preferably 50% of the bar thickness (D). 25/39 P17285 [8] 8. Strain measuring method according to one of claims 1 to 7, characterized in that the bending beam (1) has a notch (2) with a notch width (l) of 2 mm to 4 mm. [9] 9. Strain measuring method according to one of claims 1 to 8, characterized in that the bending beam (1) is made of a composite plate containing wood and cement. [10] 10. Strain measuring method according to claim 9, characterized in that the bending beam (1) - from 50% by volume to 70% by volume of wood or wood chips, - from 20% by volume to 40% by volume of cement, - from 7% by volume to 15% by volume of bound water and - Contains from 0% by volume to 3% by volume of additional hydration additives. [11] 11. Test setup for carrying out a strain measurement method according to one of claims 1 to 10 for determining the stretchability of thin layers of a wall paint (20) according to a first test arrangement, characterized in that - The test setup comprises a bending beam (1) and a test device equipped with an industrial camera (7) and with measuring software for carrying out a three-point bending test, the industrial camera being designed to measure the deformation on the bending beam to be tested (1) to record during the bending process, and the measuring software is designed to store and evaluate the recorded deformations and displacements; in which - The bending beam (1) is made of an absorbent material, has a beam length (L) and a rectangular cross section with a beam width (B) and with a beam thickness (D), with a notch (2) on a broad side (11) of the Bending beam (1) is arranged in the center length (L / 2) of its beam length (L) and transversely to the longitudinal direction of the bending beam (1), the notch (2) having a notch depth (d) and a notch width (l) and over the entire bar width (B) runs; such as - A wall coating (20) is applied along a section with a sample layer length (Lp) on the smooth broad side (12) of the bending beam (1) opposite the notched broad side (11) on both sides of the length center (L / 2) of its beam length (L); as well as further Measuring points (M) are arranged in at least one sample length interval (L P1 , L P2 , L P3 ) of the sample layer length (LP) of the applied wall coating (20), - wherein at least one output length (Lo) is recorded as a distance measure between measuring points (M) of the at least one sample length interval (LP1, LP2, LP3) on the undeformed bending beam (1); 26/39 P17285 [12] 12th wherein the bending beam (1) is positioned to carry out a three-point bending test on two lateral supports (6) of the test device such that the side coated with the wall paint (20) is oriented towards the lateral supports (6) and one in Center length (L / 2) of the bending beam (1) arranged in the middle Test stamp (5) opposite the test device; wherein the bending deformation of the bending beam (1) is recorded during the three-point bending test with an industrial camera (7), which industrial camera (7) captures the coated side of the bending beam (1) opposite the central test stamp (5); wherein the test device is configured such that the three-point bending test ends as soon as the industrial camera (7) detects cracks with hairline cracks in the wall paint (20) in a cracking zone (R) of the coated side of the bending beam (1). Test set-up for carrying out a strain measurement method according to one of claims 1 to 10 for determining the stretchability of thin layers of a multilayer wall coating system (25) according to a second test arrangement, characterized in that the test set-up has a bending beam (1) and one with an industrial camera (7) and with a measuring software equipped test device for performing a three-point bending test, the industrial camera being designed to record the deformation on the bending beam to be tested (1) during the bending process, and the measuring software being designed to record the recorded deformations and Save and evaluate shifts; wherein the bending beam (1) is provided from an absorbent material, has a beam length (L) and a rectangular cross section with a beam width (B) and with a beam thickness (D), with a notch (2) on a broad side (11) of the Bending beam (1) is arranged in the center length (L / 2) of its beam length (L) and transversely to the longitudinal direction of the bending beam (1), the notch (2) having a notch depth (d) and a notch width (l) and over the entire bar width (B) runs; and a multilayer wall coating system (25) is applied along a section with a sample layer length (LP) to the notched broad side (11) of the bending beam (1) on both sides of the length center (L / 2) of its beam length (L); and further measuring points (M) are arranged in at least one sample length interval (Lp1, Lp2, Lp3) of the sample layer length (LP) of the applied wall coating (20), at least one starting length (L0) being the distance between measuring points (M) of the at least one sample length interval ( LP1, LP2, LP3) is recorded on the undeformed bending beam (1); 27/39 P17285 - The bending beam (1) for performing a three-point bending test on two side supports (6) of the test device is positioned such that the side coated with the wall paint (20) is oriented towards the side supports (6) and one in the middle of the length (L / 2) of the bending beam (1), the test ram (5), which is arranged centrally, is opposite the test device; in which - The bending deformation of the bending beam (1) is recorded during the three-point bending test with an industrial camera (7), which industrial camera (7) detects the coated side of the bending beam (1) opposite the central test stamp (5); in which - The test device is configured such that the three-point bending test ends as soon as the industrial camera (7) in a cracking zone (R) of the coated side of the bending beam (1) detects cracking with hairline cracks in the wall paint (20). [13] 13. Test structure according to claim 11 or 12, characterized in that after the end of the three-point bending test, the measuring software of the test device changes the length Al of the wall coating (20) or wall coating system (25) applied to the bending beam (1) as the difference of at least one State length (L1) in the event of crack formation, which state length (L1) corresponds to the distance between measuring points (M) of the at least one sample length interval (LR1, LR2, LR3) in the event of crack formation on the deformed bending beam (1), and the initial length (L0) of the at least one sample length interval (LP1, LP2, LP3) on the undeformed bending beam (1) determined by calculation. 28/39 P17285 1.5
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同族专利:
公开号 | 公开日 EP3581882A1|2019-12-18| AT521308B1|2020-02-15|
引用文献:
公开号 | 申请日 | 公开日 | 申请人 | 专利标题 CN103728186A|2013-12-26|2014-04-16|清华大学|On-line observable high-temperature three-point bend test system|DE102015122052B4|2015-12-17|2021-12-16|Meik Andre Landwehr|Spin test device and measurement method|DD266175A1|1987-11-18|1989-03-22|Bauakademie Ddr|TESTING BUTTER FOR DETERMINING THE RISSOVERING BEHAVIOR OF PAINTING SYSTEMS ON SILICATE SUBSTRATES| DE19802716C2|1997-03-07|2000-05-18|Dresden Ev Inst Festkoerper|Method for determining mechanical properties of thin layers|CN111089802A|2020-01-07|2020-05-01|陈鑫淑|Electric power fitting test accessory| CN111157329B|2020-02-12|2021-11-23|上海交通大学|Low-temperature CTOD testing device and method|
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申请号 | 申请日 | 专利标题 ATA50471/2018A|AT521308B1|2018-06-12|2018-06-12|Bending beam strain gauging method and test setup for carrying out such a strain gauging method|ATA50471/2018A| AT521308B1|2018-06-12|2018-06-12|Bending beam strain gauging method and test setup for carrying out such a strain gauging method| EP19177904.0A| EP3581882A1|2018-06-12|2019-06-03|Flexion beam flex measurement method and test structure for for carrying out such a method| 相关专利
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