EP-4100714-B1 - DEVICE FOR REPRODUCIBLY APPLYING STRESS TO TEST BODIES

Inventors

• Braak, Richard

Dates

Publication Date

20260513

Application Date

20201207

Claims (11)

1. Device (1) for applying a defined stress to test specimens (2), comprising • a guide (3) having an inner circumference (3b), the shape of which corresponds to the shape of an outer circumference (2a) of the test specimen (2) and the size of which permits a translational movement of the test specimen (2) to a machining position (4) through the guide (3) with only one degree of freedom, and ∘ engraving means (5) which are designed to exert a specified cutting action of force on the surface of this test specimen (2) in response to a test specimen (2) reaching the machining position (4), wherein the engraving means (5) comprise at least one engraving element (51) and at least one spring element (52), wherein the spring element (52) drives the engraving element (51) in the direction of an inoperative position and wherein a test specimen (2), which reaches the machining position (4), deflects the engraving element (51) out of this inoperative position.
2. Device (1) according to Claim 1, wherein the engraving element (51) is located within the cross section (3c) of the guide (3) or at least protrudes into this cross section (3c) in its inoperative position.
3. Device (1) according to either of Claims 1 and 2, wherein a region of the spring element (52) functionalized for exerting a cutting action of force acts as an engraving element (51).
4. Device (1) according to any of Claims 1 to 3, wherein the engraving means (5) comprise at least one drive source (53), which sets at least one engraving element (51) in periodic motion, wherein the periodic motion leads to the engraving element (51) rubbing against the surface of a test specimen (2) when the engraving element (51) is in contact with the surface.
5. Device (1) according to Claim 4, wherein at least one engraving element (51) is designed as a saw blade (51a).
6. Device (1) according to any of Claims 1 to 5, wherein at least one engraving element (51) comprises a metal main body (51b) which is studded with particles (51c) which are harder than the material of the main body (51b).
7. Device (1) according to any of Claims 1 to 6, further comprising at least one sensor (6), which emits a signal (6a) in response to a test specimen (2) reaching the machining position (4), and at least one drive (7), which is designed to bring at least one engraving element (51) into contact with the surface of this test specimen (2) in response to this signal (6a).
8. Device (1) according to any of Claims 1 to 7, wherein at least one outlet (3d) for a gas is provided on the inner circumference (3b) of the guide (3), the gas pushing a test specimen (2) through the guide (3) during the movement in the direction of the machining position (4).
9. Device (1) according to any of Claims 1 to 8, wherein the guide (3) continues up to an outlet opening (3e) on the other side of the machining position (4), and wherein at least one container (9) is additionally provided, which is capable of receiving both a liquid corrosion medium (10) and at least one test specimen (2) exiting from the outlet opening (3e).
10. Device (1) according to Claim 9, further comprising a feed (11) for an inert gas at least into the region of the guide (3) between the machining position (4) and the outlet opening (3e).
11. Device (1) according to any of Claims 1 to 10, wherein the engraving means (5) are arranged in a chamber (12) which surrounds an outer circumference (3a) of the guide (3), wherein this chamber (12) is divided into several segments (12a-12d), which can be separated from each other by a movement of segments (12a-12d) perpendicular to an axis (3f) of the guide (3).

Description

The present invention relates to subjecting test specimens to a defined stress with the aim of being able to draw conclusions about the quality of a coating of the test specimen from the reaction of the test specimen to this stress. State of the art Many components consist of a relatively inexpensive base material whose surface is coated with a hard coating or other functional layer. The proper functioning of the component may then depend on the functional layer remaining intact. If the base material is coated with an adhesion promoter layer and the functional layer is applied to this adhesion promoter layer, failure of the adhesion promoter layer can also lead to the functional layer detaching. During operation of the component, the aforementioned layers can be locally overloaded. It is an important quality characteristic for the layers whether such damage remains locally confined or whether it propagates further, for example through stress corrosion cracking, even after the overload has ended, and in extreme cases, even a brief local overload can ultimately lead to the layer's failure. Therefore, in the DE 10 2017 220 946 A1 A method has been proposed by which a coating can be applied to a test specimen in a defined and reproducible manner. The local stress can be assessed, and the resulting damage to the coating can be evaluated. In KR 101 484 440 B1 It is about applying a clearly visible and precise marking to a pipe for further processing. In JP H02 243204 A It involves planing the surface of a plastic pipe. Disclosure of the invention Within the scope of the invention, a device for subjecting test specimens to a defined stress was developed. This device is specifically designed to subject a large number of nominally identical test specimens, generated during quality control in series production, to precisely identical stresses. If the resulting damage to the coatings of the components differs, it can be concluded, for example, that there are variations in the quality of the coatings. The device is defined in independent claim 1. The device comprises a guide with which the test specimens can be guided to a machining position in a defined and reproducible manner. For this purpose, the guide has an inner circumference whose shape corresponds to the shape of an outer circumference of the test specimens and whose size allows translational movement of the test specimens through the guide with only one degree of freedom to the machining position. The guide can, in particular, lead the specimens to the machining position in a straight line. Any suitable mechanism can be used to propel the test specimens to the processing position. A particularly advantageous solution is to design the guide as a drop tube into which the test specimens can be thrown, accelerating them by gravity to a defined speed until they reach the processing position. This is especially cost-effective and reliable. The device further comprises engraving means. These engraving means are designed to exert a predetermined cutting force on the surface of a test specimen in response to its reaching the processing position. If this force is identical for all test specimens processed in a series of tests, the respective The resulting damage to surface coatings can be objectively compared. The engraving device comprises at least one engraving element and at least one spring element. The spring element drives the engraving element towards a rest position. A test specimen reaching the machining position deflects the engraving element from this rest position. In this state, the spring element presses the engraving element against the surface of the test specimen with a restoring force. Provided that the spring element operates in its elastic state, this restoring force is the same for all nominally identical test specimens. Thus, all test specimens are subjected to the same qualitative and quantitative stress. The engraving element can, for example, be located within the cross-section of the guide in its rest position or at least project into this cross-section. For this purpose, the guide can, for example, have one or more recesses. The machining position is then the point where the test specimen comes into contact with the engraving medium. The stress applied to the test specimen can, in particular, be a scribing stress. In a particularly advantageous embodiment, a region of the spring element designed to exert a cutting force functions as an engraving element. For example, one or more points can be applied to the spring element in this region. The spring element can also be coated, for example, with diamond paste or another substance containing solid abrasive particles. The engraving element, which exerts a cutting force on the surface of the test specimen, is itself a wear part and must be replaced at regular intervals. To ensure that the stresses applied to the test specimens before and after replacement are identical, it is advantageous if eng