Testing machine sample chamber for installation in a testing machine for material testing of a material sample, testing machine and testing procedure for carrying out a material test on a material sample under a fluid atmosphere

Abstract

The invention relates to a testing machine and a testing machine sample chamber (12) for installation in a testing machine (10) for carrying out a material test of a material sample (18) comprising: a sample chamber body (48), a sample holding device (24) for holding the material sample (18) with a first side (26) and a second side (28), a receiving device (32) with a transparent material disc (30), an inlet device (22) for a fluid medium, wherein a sample chamber interior (20) is formed between the material sample (18) and the transparent material disc (30), which can be filled with the fluid. The invention further relates to a testing method for carrying out a material test of a material sample (18), a computer program, a machine learning model and a data processing device for controlling and / or regulating a testing machine (10).

Description

State of the art

[0001] The invention relates to a testing machine sample chamber for installation in a testing machine for material testing of a material sample and a method for carrying out a material test on a material sample under a fluid atmosphere. Furthermore, the invention relates to a testing machine and a method for carrying out the material test on the material sample under a fluid atmosphere. The invention also relates to a computer program and a data processing device, as well as a machine learning model and a use of the testing machine sample chamber.

[0002] Testing machines for conducting material tests are well-known and serve to determine the mechanical properties of materials. These materials include metals such as steel, aluminum, or titanium, as well as materials containing plastics, such as composites. In the automotive industry, suppliers, for example those involved in body-in-white production, are under constant pressure to increase production efficiency, minimize costs, and optimize the quality and precision of the manufactured parts. Material characterization and quality assurance of the materials used are particularly relevant in sheet metal forming. Standardized forming tests, especially deep-drawing tests according to Erichsen (ISO 20482), Nakajima, or Marciniak (ISO 12004), are used in these tests. In these tests, a sheet of material is deformed using a test die, and the deformation and the resulting material changes are measured.

[0003] Simultaneously or alternatively, the forming test is performed cyclically until a failure occurs, typically a fracture or a crack in the sheet metal. Determining the forming limit curve (FLC) is of particular importance for ascertaining the mechanical properties of sheet metal, as well as its stretchability and deep-drawing capabilities. This is referred to as the forming capacity, since the FLC represents a material's ability to be formed. From this, the deformation of the tested sheet metal, from necking to fracture, can be compared and evaluated against existing structural and shape changes in real components. Every material has its own individual forming limit curve (FLC). There is increasing interest in materials testing under fluid exposure, for example, in plant engineering or hydrogen technology.It is desirable to conduct the material testing under a fluid atmosphere, meaning that the material is exposed to the fluid during the testing procedure. In particular, it is of great interest to understand the effects of hydrogen on metallic materials before their use. Therefore, material testing under a hydrogen atmosphere is highly relevant.

[0004] Prior art testing methods exist that utilize a modified setup of the standard tensile test (DIN EN ISO 6892) under hydrogen exposure. In this method, the entire test chamber is placed under a hydrogen atmosphere, for example, under increased pressure, typically 350 bar or 700 bar. An autoclave with a compressor is typically required to create the desired hydrogen atmosphere. This method can be applied to both quasi-static and dynamic material testing. The results are mechanical parameters and characteristic values ​​that reflect the influence of hydrogen on the microstructure.

[0005] A major disadvantage of the described fluid testing, particularly with gases such as hydrogen, is the need for complex and therefore expensive equipment and facilities. The equipment, typically the autoclave and compressor, is costly to purchase and requires intensive maintenance. Furthermore, a relatively large quantity of gas, such as hydrogen, is required. For example, the testing machine must be operated in an accredited gas laboratory, such as a hydrogen laboratory. The time required to fill the test chamber is also significant. Therefore, conducting a complete test of just one material sample can take several hours.

[0006] To investigate the influence of the fluid, for example hydrogen, alternative material tests are performed with conditioned material samples. In this method, the material samples are first exposed to the fluid atmosphere, for example hydrogen, pre-conditioned under a hydrogen atmosphere, and then tested under normal laboratory conditions. This has the advantage that no complex safety concept is required. However, this method has other disadvantages, such as the difficulty in demonstrating the extent to which volatilization of the fluid, for example hydrogen, occurs during the testing of the characteristic parameters and thus influences the results. Disclosure of the invention

[0007] The object of the invention is to create an improved way of carrying out a test of a material sample in a testing machine for determining mechanical properties.

[0008] Furthermore, the object of the invention is to create an improved method for carrying out material testing under a fluid atmosphere in order to obtain mechanical properties.

[0009] Furthermore, the object of the invention is to provide an improved testing machine for carrying out material testing under a fluid atmosphere in order to obtain mechanical parameters.

[0010] Furthermore, the object of the invention is to provide an improved computer program for determining mechanical parameters.

[0011] Furthermore, the object of the invention is to provide a data processing device for a testing machine for control and / or regulation.

[0012] Furthermore, the object of the invention is to provide an improved machine learning model for extracting features, in particular structures, from an image.

[0013] The problems are solved by the features of the independent claims. Favorable embodiments and advantages of the invention become apparent from the further claims, the description, and the drawings.

[0014] The features listed individually in the patent claims can be combined in a technologically meaningful way and can be supplemented by explanatory facts from the description and by details from the figures, showing further embodiment variants of the invention.

[0015] According to a first aspect of the invention, a test chamber for installation in a testing machine is proposed, which is configured for performing a material test on a material sample. The test chamber comprises a sample chamber body, a sample holding device for holding the material sample with a first side and a second side, a receiving device with a transparent material disk, and an inlet device for a fluid medium. An interior space within the sample chamber is formed between the material sample and the transparent material disk, and this interior space can be filled with the fluid. The interior space within the sample chamber can typically enclose a sample chamber volume.

[0016] The test chamber, also known as the sample chamber, can be mobile and transportable. This allows the test chamber to be loaded and prepared externally with the material sample. During preparation, the material sample can be clamped into the sample holder, and the test chamber can be pressurized by introducing fluid. The fluid can be pressurized to a higher pressure than ambient pressure. Fluid pressures of several hundred bar, for example, 350 bar or 700 bar, can be achieved in the test chamber. Once prepared, the test chamber can be installed in the test machine, particularly a standard test machine. The test machine can be configured to perform a Nakajima or Marciniak deep drawing test.By using the testing machine sample chamber, material testing can be carried out under a fluid atmosphere, whereby the material sample can be exposed to fluid during the material testing, in particular for the entire duration of the material testing.

[0017] Alternatively, the test machine sample chamber can be permanently installed in the test machine, and the material sample can be installed at the location of the test machine before each material test and the sample chamber can be flooded with the fluid.

[0018] The sample chamber body can be constructed in one piece; alternatively, the sample chamber body can be constructed in multiple parts, whereby the individual parts can be joined together in a fluid-tight manner.

[0019] The sample holding device can be a sample holder into which the material sample is clamped. The sample can be held by clamping between holding elements, which are designed, for example, as pressure plates. The holding elements can be arranged on both sides, particularly on the first and second sides of the material sample. The holding elements, for example, pressure plates, can be connected by fasteners, such as screws and nuts, so that the material sample is clamped. The holding elements can be integrated into the sample chamber body, for example, as a shoulder.

[0020] The material sample to be examined can be a metal sheet containing an alloy with iron, aluminum, and / or titanium, for example, steel, an aluminum alloy, or a titanium alloy. The material sample can also be made of a composite material, for example, a plastic, or be or contain a carbon fiber and / or glass fiber composite.

[0021] The material sample can typically have a thickness of 0.5 mm to 10 mm. In principle, material samples with other thicknesses can also be used. The force applied to the punch can be adjusted to the thickness of the material sample.

[0022] The possible sample thickness used and the force applied to the punch device of the testing machine and / or the size of the testing fixture can be adjusted to each other.

[0023] The fluid can be a liquid or a gas. For example, the gas can be hydrogen if the material sample is to be examined for the influence of hydrogen on the material's mechanical properties. In particular, the test chamber can be used to investigate hydrogen embrittlement. Typically, the fluid in the test chamber is kept at a pressure higher than ambient pressure, so the material sample is subjected to increased fluid pressure.

[0024] The transparent material disc can be made of a material that is transparent to electromagnetic radiation, particularly electromagnetic radiation in the wavelength range between 100 nm and 1500 nm, preferably visible light or infrared light (IR light). The transparent material disc can also be transparent to X-rays. The transparent material disc can be made of float glass. The advantage of float glass is that it allows for distortion-free imaging of the material sample. Furthermore, float glass can exhibit high flexural strength.

[0025] The test machine sample chamber can be very compact and easily installed in and removed from the test machine. Thanks to the enclosed sample chamber and compact design, a small installation space with a small sample chamber volume can be achieved, thus requiring only a small amount of fluid, such as a small amount of hydrogen.

[0026] It is advantageous to use a separate testing machine sample chamber, as material testing can be performed in laboratories without protective equipment, such as hydrogen protection devices.

[0027] This allows a standard test procedure, such as a Nakajima deep drawing test (ISO 12004), to be performed in a standard testing machine, thereby simplifying qualitative testing under fluid atmospheres, such as hydrogen atmospheres. Thus, material testing can relatively accurately reflect real-world conditions. For example, the hydrogen compatibility of materials, such as metallic samples, can be demonstrated based on the deep drawing test performed.

[0028] With a favorable design of the test chamber, the inlet device can be arranged in the chamber body between the sample holding device and the holding device with the transparent material disc. This allows the fluid, for example, the gas, to be easily introduced into the test chamber. Standard components for fluids, and especially standard components for gases, can be used as inlet devices.

[0029] Depending on the design of the test chamber, the inlet device can have either a gas valve or a liquid valve. In the latter case, filling, and in particular refueling, the test chamber can be carried out using a gas cylinder. This eliminates the need to operate the test machine in a certified gas laboratory. Alternatively, liquid media can be introduced into the test chamber simply and in a controlled manner.

[0030] With a favorable design of the test chamber, a pressure measuring device can be provided for measuring and monitoring pressure, particularly fluid pressure, such as gas pressure, within the chamber. This allows the fluid supply, for example, of the gas, to be regulated and a constant fluid pressure to be maintained within the chamber. Standard components commonly used in plant engineering can be employed.

[0031] With a favorable design of the test chamber, the sample holding device can comprise a first sealing device and retaining elements configured to clamp the material sample and seal the interior of the sample chamber, particularly against ambient pressure. The material sample can be clamped between two retaining elements, for example, by clamping. The retaining elements can be ring-shaped. The retaining elements can enclose the material sample. The retaining elements can be adapted to the geometry of the material sample.

[0032] The first sealing device can be of one or two parts. The sealing device can have two sealing elements, for example, sealing rings, with a first sealing element, for example, a first sealing ring, located on the first side of the material sample and a second sealing element, for example, a second sealing ring, located on the second side of the material sample. Alternatively, the material sample can be clamped between the holding elements, and the holding elements can, by means of the first sealing device, create a seal for the interior of the sample chamber.

[0033] Alternatively, the sealing element can be arranged between the sample chamber body and the material sample. In this case, a recess can be provided in the sample chamber body into which the material sample is placed.

[0034] The sealing element can be arranged between the sample chamber body, in particular the shoulder, and the material sample.

[0035] With a favorable design of the test chamber, the holding device for the transparent material disc can include a second sealing device and retaining elements. These elements are designed to hold the transparent material disc and seal the interior of the sample chamber against ambient pressure. This allows for the use of different transparent material discs, as they are easily interchangeable. For example, a borosilicate glass disc can be used as the transparent material disc. Borosilicate glass is transparent in a wavelength range between 0.3 µm and 3 µm, and it can transmit electromagnetic radiation across a wide wavelength range. Alternatively or additionally, a mica disc can be used as the material disc. The transparent material disc can be made of multiple parts. The transparent material disc can also be float glass.

[0036] The choice of material for the transparent disc is determined by its flexural strength. The required flexural strength depends on the internal pressure in the test chamber of the testing machine. A transparent disc with good thermal shock resistance can be used if the test is performed at elevated temperatures.

[0037] Good thermal shock resistance is important because temperature differences within glass can lead to thermal breakage. The higher the thermal shock resistance of the transparent pane material, the lower the risk of thermal breakage.

[0038] The thermal shock resistance of float glass made from soda-lime silicate glass is relatively low at approximately 40 K, while it is significantly higher for float glass made from borosilicate glass, exceeding 100 K due to its considerably lower coefficient of thermal expansion. The thermal shock resistance of glass can be increased by thermal tempering, resulting in approximately 100 K for partially tempered glass (TVG) and approximately 200 K for fully tempered glass, such as tempered safety glass (ESG).

[0039] According to a further aspect of the invention, a testing machine is proposed which is set up for carrying out a material test on a material sample under fluid exposure and comprises a punch device for exerting a force on a second side of the material sample and an observation device for observing a first side of the material sample, wherein a test machine sample chamber according to the invention is provided. The testing machine can include the test machine sample chamber. The test machine sample chamber can have a sample chamber body.

[0040] In a favorable design of the testing machine, the material sample can be arranged in a sample holding device, and a sample chamber interior, which can be filled with the fluid, can be formed between the material sample and a transparent material disk facing the observation device. It is advantageous that a small sample chamber volume is formed within the sample chamber interior, which can be flooded with the fluid.

[0041] Typically, the testing machine can have a base and travel crossbeam with very good guiding properties and high rigidity. The test machine specimen chamber can be installed between this base and travel crossbeam.

[0042] Furthermore, a digitally controlled servo drive can be provided to drive the punch mechanism. This ensures virtually maintenance-free operation. Measuring, control, and / or regulating electronics can guarantee reliable control of the punch mechanism and the absorption of the forces exerted on the material sample. This allows for high accuracy, high measurement rates, and thus precise and reproducible test results.

[0043] The test machine's sample chamber can be loaded with the material sample externally, particularly outside the test machine, and flooded with the fluid before being installed in the test machine. This allows a standard test machine to be used for material testing, thus expanding its range of applications. Furthermore, improved performance can be achieved because material and fluid changes are simplified. This is advantageously facilitated by the portable sample chamber.

[0044] With a favorable design of the testing machine, the transparent material disc can be held fluid-tight in a receiving device. This allows for the creation of a sealed sample chamber between the material sample and the transparent material disc. The fluid can then be poured into this sample chamber. The sample chamber can thus be formed between two fluid-tight material discs. One of these discs can be the material sample. The disc opposite the material sample can be transparent for observation.

[0045] In a favorable design of the testing machine, an inlet device for the fluid can be provided, which is arranged between the sample holding device and the holder for the transparent material disc. The inlet device can be a valve for the fluid, which is, for example, a liquid or a gas. The inlet device can be controllable, for example, electronically controlled.

[0046] With a favorable design of the testing machine, the observation device can include a first camera and at least one second camera, whose fields of view are directed towards the first side of the material sample and can capture images of the first side of the material sample during a test procedure. This allows changes in the material sample to be observed and documented. The images can be made available for further analysis, for example, digital image correlation.

[0047] In a well-designed testing machine, an evaluation unit can be provided that is connected to the first camera and at least the second camera in such a way that the images from the first and second cameras can be transferred to the evaluation unit. The evaluation unit can be configured to perform digital image correlation. For example, the first and second cameras are electrically connected to the evaluation unit. This allows changes due to the application of force, and thus the determination of mechanical parameters, to be observed.

[0048] The observation device can be more complex. For example, it can include a laser and two cameras. In this setup, laser light is directed onto the surface of the material sample using the laser's light source, creating a speckle pattern that is then recorded by the two cameras.

[0049] Virtual measurement markers can be set and tracked, and a sophisticated correlation algorithm can be applied. The strain on the material sample can then be calculated from the displacement of two consecutively acquired images. The advantage here is that no markings on the material sample are necessary. This allows preparation and cycle times to be reduced to a minimum.

[0050] With a favorable design of the test procedure, the force can be applied to the second side of the material sample by means of a controllable stamp device, whereby a force-displacement-time curve can be recorded.

[0051] With a well-designed testing machine, a control unit can be provided to operate the punch assembly for performing a force-displacement-time test. The punch assembly can, for example, be controlled to apply a linearly increasing force to the material sample. Alternatively, a cyclical increase in force can be achieved by controlling the punch assembly.

[0052] Depending on the design of the testing machine, the evaluation unit and the control and / or regulation unit can be connected electrically or wirelessly. An electrical connection can be implemented using control cables. A wireless connection can be implemented, for example, using Bluetooth or radio technology.

[0053] With a favorable design of the testing machine, the evaluation unit can be set up to document and analyze a deformation of the material sample in order to correlate it with the force-displacement-time curve.

[0054] According to a further aspect of the invention, a computer program is proposed which is configured to evaluate images from a first camera and at least one second camera, employing a method of digital image correlation. The computer program can utilize algorithms from machine learning models that are used to analyze the images from the first and at least the second camera.

[0055] According to a further aspect, a testing procedure for carrying out a material test of a material sample is proposed, wherein a first side of the material sample is exposed to a fluid atmosphere, a force is exerted on a second side of the material sample to achieve a deformation of the material sample, and images, in particular continuously, are taken of the first side of the material sample, whereby the occurrence of damage, in particular failure of the material sample, for example the formation of cracks, is observed and documented.

[0056] With a favorable design of the testing procedure, the images can be captured by a first camera and at least one second camera, both directed at the first side of the material sample. This allows for at least a two-dimensional image of the sample's surface. Alternatively, three or more cameras can be used.

[0057] The observation system can also be more complex. For example, it can include a laser and two cameras. In this setup, laser light is directed onto the surface of the material sample using the laser's light source, creating a speckle pattern that is recorded by the two cameras. Virtual measurement markers can be set and tracked, and a sophisticated correlation algorithm can be applied.

[0058] The strain on the material sample can then be calculated from the displacement of two consecutively captured images. The advantage of this method is that no markings are required on the sample. This allows preparation and cycle times to be reduced to a minimum.

[0059] With a favorable design of the test procedure, the force can be applied to the second side of the material sample by means of a controllable stamp device, whereby a force-displacement-time curve can be recorded.

[0060] In addition, a machine learning model is proposed that is configured to extract features, particularly structures, from an image or images from an observation device, specifically a first and at least a second camera. Advantageously, the extracted features and / or structures can be used to derive results from acquired parameters with and without a fluid atmosphere. The machine learning model can, in particular, be a trained machine learning model.

[0061] According to a further aspect of the invention, a data processing device for controlling and / or regulating a testing machine is proposed. This device is configured to perform a testing procedure on a material sample under a fluid atmosphere and to evaluate images from an observation device of the testing machine. This allows for the optimization of the testing procedure. Likewise, evaluation programs can be used to analyze the data from the observation device.

[0062] According to a further aspect of the invention, the use of a test machine sample chamber in a testing machine for determining the mechanical properties of a material sample under a fluid atmosphere is proposed, wherein the test machine sample chamber can be installed in and removed from the testing machine. This allows material samples to be examined under fluid exposure in a standard testing machine in a simple manner. The material sample can be exposed to the fluid for the entire duration of the test. The fluid can be, for example, a gas. A particularly advantageous application of the test machine sample chamber could be a hydrogen-flooded sample chamber, for example, for investigating hydrogen embrittlement of materials. drawing

[0063] Further advantages will become apparent from the following description of the drawings. The figures in the drawings illustrate exemplary embodiments of the invention. The figures, the description, and the claims contain numerous features in combination. It will be advantageous for those skilled in the art to also consider the features individually and combine them into meaningful further combinations.

[0064] They show, for example: Fig. 1 a schematic simplified representation of a testing machine with a stamping device, an observation device and a testing machine sample chamber; Fig. 2 a test machine sample chamber in a first embodiment; Fig. 3. the assembly of the device according to Fig. 1 after the material test has been carried out and the material sample has failed; Fig. 4 a section of the testing machine from Fig. 1 in sectional view; Fig. 5 a flowchart of an embodiment of the test procedure; Fig. 6. Another flowchart of part of the testing procedure; and Fig. 7 Another flowchart of part of the testing procedure. Embodiments of the invention

[0065] In the figures, similar or equivalent components are numbered with the same reference symbols. The figures merely show examples and are not to be understood as limiting.

[0066] Before the invention is described in detail, it should be noted that it is not limited to the respective components of the device or the respective process steps, as these components and processes may vary. The terms used here are intended solely to describe particular embodiments and are not used restrictively. Furthermore, where the singular or indefinite articles are used in the description or in the claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0067] The directional terminology used below, including terms like "left," "right," "above," "below," "in front," "behind," "after," and the like, serves only to improve the understanding of the figures and is in no way intended to limit their generality. The components and elements depicted, their interpretation, and their use may vary according to the considerations of a person skilled in the art and be adapted to the specific applications.

[0068] Fig. Figure 1 shows a schematic side view of a testing machine 10 with a testing machine sample chamber 12, an observation device 14 and a testing tool 16, which is designed as a stamping device 16.

[0069] The sample chamber 12 is a mobile sample chamber 12 and can be removed from the testing machine 10, loaded, and then reinstalled in the testing machine 10. Clamping a material sample 18 into the sample chamber 12 can be done outside the testing machine 10. Similarly, flooding or filling the interior of the sample chamber 20 with a fluid through an inlet device 22 can be done outside the testing machine 10. The inlet device 22 has a cylindrical inlet opening 21 and an inlet valve (not shown). The interior of the sample chamber 20 encloses a sample chamber volume. The fluid is a gas or a liquid. The gas is selected depending on which gas exposure of the material sample 18 is to be investigated.The gas is, for example, hydrogen, if an investigation is to be carried out into hydrogen embrittlement, i.e. the behavior of material materials under the influence of hydrogen.

[0070] The sample chamber 12 comprises a sample holding device 24 with a first holding device 25 for the material sample 18 and a sealing device 27. The material sample 18 to be tested is clamped into the holding device 25. The holding device 25 can, for example, be a clamping device 25 for a sheet-shaped material sample 18. The material sample 18 is typically a sheet with a geometry adapted for the material test, for example, a circular geometry. The thickness of the material sample 18 is adapted to the material test to be performed. The first holding device 25 is, for example, arranged on the side of the sample chamber 12 facing the test tool 16. The sample holding device 24 is designed to be fluid-tight by means of the sealing device 27. The sealing device 27 can be designed in two parts.

[0071] The material sample 18 has a first side 26 facing the interior of the sample chamber 20, and a second side 28 facing the testing tool 16, typically the punch assembly 16. The testing tool 16 thus acts on the second side 28, which can also be referred to as the back side.

[0072] The shape of the test tool 16, in particular the punch, varies depending on the test to be performed. The following deep-drawing tests, performed with differently shaped test tools 16, are given as examples. In the Nakajima deep-drawing test, the test tool 16 is a hemispherical punch. In the Maciniak deep-drawing test, the test tool 16 is a cylindrical punch.

[0073] The sample chamber 12 further comprises an observation window 36 with a transparent disc 30, which is held fluid-tight in a receiving device 32 by means of a sealing device 34 or is clamped in place. The observation window 36 and the receiving device 32 are, for example, manufactured as a single piece. For example, the observation window 36 comprises a second holding device 33, the sealing device 34, and the transparent material disc 30. A standard component from the companies Metaglas, ACI, or Göttgens can be used, for example, as the observation window 36. The transparent material disc 30 in the observation window 36 is, for example, borosilicate glass and / or mica and / or quartz glass. The receiving device 32 comprises the second sealing device 34 and the second holding device 33.

[0074] The transparent material disc 30 used is transparent to electromagnetic radiation, in particular to electromagnetic radiation in the wavelength range between 0.1 µm and 3 µm.

[0075] Between the observation window 36, in particular the transparent material disc 30, and the second holding device 33, a sealing device 34, suitable for the pressure conditions in the interior of the sample chamber 20, is arranged on both sides of the observation window 36. The transparent material disc 30 is positioned between elements of the sealing device 34 and the second holding device 33. The transparent material disc 30 is typically made of float glass or consists of a float glass sheet. Float glass has a high flexural strength of at least 45 N / mm². 2 Float glass also exhibits high resistance to temperature changes.

[0076] For example, metal gaskets, graphite gaskets, plastic gaskets or mica composite gaskets can be used as elements of the sealing device 34 and the sealing device 24.

[0077] The sample chamber 12 has an inlet device 22 on one or both sides for the fluid, which is introduced into the interior of the sample chamber 20 before the test and floods the interior of the sample chamber 20. The first side 26 of the material sample 14 faces the interior of the sample chamber 20 and is exposed to the fluid before and / or during the test. The fluid is, for example, a gaseous medium. For example, the fluid is a gas, such as hydrogen gas. If hydrogen gas is used as the fluid, a material change in the material sample 18, in particular hydrogen embrittlement of the material sample 18, due to hydrogen exposure and its influence on the behavior of the material sample 18 during a test procedure, in particular a deep drawing test, can be investigated.

[0078] The observation system 14 typically comprises a first camera 38 and at least one second camera 40, which are directed at the first side 26 of the material sample 18, as well as an evaluation unit 42. The first camera 38 and at least the second camera 40 are, for example, digital cameras 38, 40. Images are recorded by the cameras 38, 40, which are then analyzed and evaluated, for example, using a digital image correlation (DIC) method. In this process, the deformation, for example, the degree of deformation, is recorded. The occurrence of cracks 46 can be determined, depending on how the test is conducted. The first camera 38 has a first field of view, and the second camera 40 has a second field of view. The fields of view of the camera 38 and the camera 40 are in Fig. 4 explicitly shown.

[0079] If a trained AI (artificial intelligence) is integrated into the evaluation unit 42, which is trained with images of standard test tests, for example standard tensile tests, mechanical properties of materials under gas exposure, for example hydrogen exposure, can be predicted.

[0080] The observation system 14 with the digital image correlation system is typically a system from the company Zeiss and is called: “Zeiss ARAMIS Adjustable”, which is a modular measuring system for 2D and 3D analyses.

[0081] The ZEISS ARAMIS Adjustable system is typically used for the analysis of statically or dynamically stressed components and materials, providing precise 2D and 3D coordinates for analysis. The system includes cameras 38 and 40, as well as lighting devices (not shown) for illuminating the material sample 18 under examination. At least one camera is used for 2D analysis; preferably, two cameras 38 and 40 are used. Additional cameras are used for 3D analysis.

[0082] The testing machine 10 has a control and / or regulating device 42 for the testing tool 16, which performs the control of the testing tool 16, in particular the punch device 16, and records a force-displacement-time curve.

[0083] Fig. Figure 2 shows a sectional view of the test machine specimen chamber 12 and the punch assembly 16 of the test machine 10 in a first embodiment. The specimen chamber 12 is rotationally symmetrical, preferably cylindrical. The specimen chamber 12 has a specimen chamber body 48. In the first embodiment, the specimen chamber body 48 is a metal cylinder made of aluminum, an aluminum alloy, or a steel alloy. The cylindrical inlet opening 21 is incorporated into the specimen chamber body 48. The specimen chamber body 48 has the holding device 25 for the material specimen 18, which is designed with a shoulder 50 and in which, for example, a recess 52 for receiving a seal 54 of the sealing device 27 is arranged. The seal 54 is a metal seal made of copper or aluminum or an alloy of both elements. The recess 52 is annular, so that the seal 54 can, for example, be implemented as a metal ring.The material sample 18 is pressed onto the sample chamber body 48 by means of a hold-down device, which is a component of the holding device 25, and by means of fasteners 58. The fasteners 58 are, for example, screws or clamps. The number of fasteners 58 is adapted to the diameter of the sample chamber body 48. If the fasteners 58 are screws, a thread is provided on the opposite side of the holding element 25. The seal is formed between the material sample 18 and the holding device 25. The recess 52 can also be omitted if a self-tapping metal gasket 54 is used.

[0084] On the opposite side of the sample chamber body 48, a second recess 60 is incorporated, into which a seal 62 of the sealing device 34 and the transparent material disc 30 are received. The seal 62 is placed directly onto the sample chamber body 48, and the transparent material disc 30 is placed onto the seal 62. Both are fixed by means of fastening elements 64 and seal the interior of the sample chamber 20 in a fluid-tight manner. The fastening elements 64 can be screws. In this case, the sample chamber body has threads on opposite sides. The transparent material disc 30 is, in one embodiment, float glass, which ensures a distortion-free image of the side of the material sample 18 facing the observation device 14. The recess 60, the seal 62, and the fastening elements 64 form the sealing device 34. The seal 62 is a plastic seal, for example, made of Teflon.

[0085] The material sample 18, for example, is a sheet metal sample with a diameter of 250 mm and a thickness of 3 mm. The diameter of the sample chamber body 48 is larger than or approximately equal to the diameter of the material sample 18. The transparent material disk 16 typically has a smaller diameter than the sample chamber body 48.

[0086] Fig. Figure 3 shows the testing machine 10 with the material sample 18 installed in the sample chamber 12 after a test procedure has been carried out. The test procedure was carried out until failure occurred, and the crack 46 in the material sample 18 is clearly visible.

[0087] Fig. Figure 4 shows a schematic sectional view of a section of the testing machine 10 with the sample chamber 12 and two cameras 38 and 40. The first camera 38 has the first field of view 66. The second camera 40 has the second field of view 68. The two fields of view 66 and 68 overlap and can thus image the surface of the material sample 18 facing the cameras 38 and 40.

[0088] Fig. Figure 5 shows an embodiment of a test procedure 100 for carrying out a material test by means of a deep-drawing test. The material sample 18 is installed fluid-tight in the test machine sample chamber 12 in process step S110, using the holding elements 25 and sealing device 27.

[0089] In process step S120, the fluid is introduced into the sample chamber 12 and the inlet device 22 is then closed.

[0090] The sample chamber 12 is installed in the testing machine 10 in process step S130.

[0091] The material testing is then carried out in process step S140.

[0092] Fig. 6 and Fig. Figure 7 shows different configurations of process step S140

[0093] Fig. Figure 6 shows a material test up to the point of failure and the appearance of crack 46. In process step S141, an initial force is applied to the testing tool 16, in particular the punch device 16, and simultaneously one or more images of the first side 26 of the material sample 18 are taken with the observation device 16. In process step S142, the force is increased and further images are taken with the observation device 14.

[0094] In step S143, the force is increased until the crack 46 is detected by the monitoring device 14. Then, in step S144, the force on the piston device 16 is stopped. Typically, the final force, i.e., the maximum force exerted on the piston 16, is recorded and stored. Steps S141, S142, and S143 can contain any number of force increase steps, depending on the chosen increase values ​​and the number of steps selected.

[0095] The force increase should be as slow as possible to allow the hydrogen time to penetrate the material. A strain rate of 0.00005 1 / s is typically achieved and recommended.

[0096] Fig.Figure 7 shows an example of a cyclic material test of material sample 18. Here, the force on the punch assembly 16 is increased in steps S141 to S143, from the initial force in step S141 to a defined, variable final force in step S143. The final force is smaller than the final force that would lead to failure. This force cycle is repeated by returning to step S141 and continuously observing the material sample 18 for changes shown on page 26.

[0097] The test frequency is selected such that the cycles are performed at a very low frequency. Typical frequencies are in the range of < 5 Hz. Cycles can range from 10,000 to 10 million, depending on the requirements.

[0098] The procedure is terminated when a failure occurs, for example, when a crack 46 appears.

[0099] The following is a purely exemplary method for evaluating images taken with at least one camera 38, preferably with two cameras 38 and 40. The method comprises the following steps: 1. Setting up the GOM system on the sample surface (correct focus); 2. Setting the trigger for recording the deformation images; 3. The system records all images until the set shutdown trigger is reached; 4. Creating a series of images, for example a video and / or slideshow, using associated software, in which the deformation is shown, for example by a color representation. Reference sign 10 testing machines 12 Sample chamber 14 Observation system 16 Testing tool, stamping device 18 Material sample 20 Sample chamber interior 21 Entrance 22 Fluid 24 Sample collection device 25 first holding device 26 first page, front 27 first sealing device 28 second page, back 30 transparent material discs 32 Receiving device for the transparent material disc 30 33 second holding device 34 second sealing device 36 observation windows 38 first camera 40 second camera 42 Evaluation unit 44 Control and / or regulating device 46 cracks, cracks 48 sample chamber bodies 50 first paragraph 52 Exclusion 54 Seal 58 Fasteners 60 second paragraph 62 Seal for the transparent material disc 64 Fasteners for the transparent material disc S100 procedure S110 to S144 Procedure steps QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] ISO 20482

[0002] ISO 12004

[0002] DIN-EN-ISO 6892

[0004]

Claims

Testing machine sample chamber (12) for installation in a testing machine (10) for carrying out a material test of a material sample (18) comprising: - a sample chamber body (48), - a sample holding device (24) for holding the material sample (18) with a first side (26) and a second side (28), - a receiving device (32) with a transparent material disc (30), - an inlet device (22) for a fluid medium, - wherein a sample chamber interior (20) is formed between the material sample (18) and the transparent material disc (30), which can be filled with the fluid. Testing machine sample chamber according to claim 1, wherein the inlet device (22) is arranged in the sample chamber body (48) between the sample receiving device (24) and the receiving device (32) with the transparent material disc (30). Testing machine sample chamber according to claim 1 or claim 2, wherein the inlet device (22) has or is a gas valve, or wherein the inlet device (22) has or is a liquid valve. Testing machine sample chamber according to one of the preceding claims, wherein a pressure measuring device is provided for measuring and monitoring a pressure in the sample chamber interior (20). Testing machine sample chamber according to one of the preceding claims, wherein the sample receiving device (24) comprises a first sealing device (25) and a holding device (27) with holding elements (50) which are configured to clamp the material sample (18) and to seal the sample chamber interior (20) against the ambient pressure. Testing machine sample chamber according to one of the preceding claims, wherein the receiving device (32) with the transparent material disc (30) comprises retaining elements (33, 62) and a second sealing device (34) which are configured to hold the transparent material disc (30) and to seal the sample chamber interior (20) against the ambient pressure. Testing machine for carrying out a material test on a material sample (18) under fluid exposure with a punch device (16) for exerting a force on a second side (28) of the material sample (18) and an observation device (14) for observing a first side (26) of the material sample (18), wherein a testing machine sample chamber (12) according to one of claims 1 to 6 is provided. Testing machine according to claim 7, wherein the material sample (18) is arranged in a sample receiving device (24) of the sample chamber (12) and a sample chamber interior (20), which can be filled with the fluid, is formed between the material sample (18) and a transparent material disk (30) facing the observation device (16). Testing machine according to claim 7 or 8, wherein the transparent material disc (30) is held fluid-tight in a receiving device (32). Testing machine according to one of claims 7 to 9, wherein an inlet device (22) for the fluid is provided, which is arranged between the sample receiving device (24) and the receiving device (32) for the transparent material disc (30). Testing machine according to one of claims 7 to 10, wherein the observation device (16) has a first camera (38) and at least one second camera (40), the fields of view (66, 68) of which are directed towards the first side (26) of the material sample (18) and take pictures of the first side (26) of the material sample (18) in a testing procedure. Testing machine according to claim 11, wherein an evaluation device (42) is provided which is electrically or by means of a radio connection connected to the first camera (38) and the second camera (40), and is configured to perform a digital image correlation. Testing machine according to one of claims 7 to 12, wherein a control and / or regulating device (44) is provided by means of which the stamp device (16) can be controlled to perform a force-displacement-time curve. Testing machine according to one of claims 12 to 13, wherein the evaluation unit (42) and the control and / or regulation unit (44) are connected electrically or by means of a wireless connection. Testing machine according to one of claims 12 to 14, wherein the evaluation device (42) is set up to document and analyze a deformation of the material sample (18) in order to correlate it with the force displacement-time curve. Computer program for evaluating images from a first camera (38) and at least one second camera (40), using a method of digital image correlation. Test method for carrying out a material test of a material sample (18), wherein a first side (26) of the material sample (18) is exposed to a fluid atmosphere, a force is applied to a second side (28) of the material sample (28) in order to achieve a deformation of the material sample (18), and images, in particular continuously, are taken of the first side (26) of the material sample (18), whereby the occurrence of damage, in particular failure of the material sample (18), for example the occurrence of one or more cracks (46), is observed and documented. Test method according to claim 17, wherein the images are recorded by a first camera (38) and at least one second camera (40) directed at the first side (26) of the material sample (18). Test method according to claim 17 or 18, wherein the force is applied to the second side (28) of the material sample (18) by means of a controllable punch device (16), wherein a force-displacement-time curve is driven. Machine learning model for extracting features, in particular structures, from an image or images of an observation device (14), in particular a first camera (38) and at least a second camera (40). Data processing device for controlling and / or regulating a testing machine (10) which is set up to carry out a testing procedure on a material sample (18) under a fluid atmosphere and to evaluate one or more images from an observation device (14) of the testing machine (10). Use of a test machine sample chamber (12) in a test machine (10) for determining mechanical properties of a material sample (18), wherein the test machine sample chamber (12) can be installed and removed from the test machine (10).

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