• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for testing a body with brittle material behavior, in particular a ceramic body, on suitability for use, wherein the body at least partially subjected to a thermal shock treatment by cooling or heating from a first temperature (T1) to a second temperature (T2) and existing cracks are detected, which is decided on the basis of the detected cracks on the fitness for use of the body. In order to allow a 100% control of bodies with high reliability, a minimum temperature difference between the first temperature (T1) and the second temperature (T2) for the thermal shock treatment is determined according to the invention on the basis of a required breaking strength of the body in use.
    公开号:AT516082A1
    申请号:T50560/2014
    申请日:2014-08-11
    公开日:2016-02-15
    发明作者:
    申请人:Materials Ct Leoben Forschung Gmbh；
    IPC主号:
    专利说明:

    Method for testing a body with brittle material behavior
    The invention relates to a method for testing a body with brittle material behavior, in particular a ceramic body, on suitability for use, the body at least partially subjected to a thermal shock treatment by cooling or heating from a first temperature to a second temperature and existing cracks are detected, which is based on The detected cracks on the suitability of the body is decided.
    Due to their good property profile, ceramic bodies are used in many different fields of technology. The particularly preferred properties of ceramic bodies include in particular a high hardness and excellent wear behavior. This makes ceramic bodies, for example, interesting for use in implants, rolling bearings or cutting elements and other mass-produced goods. Often, these ceramic bodies are exposed to high stresses near the surface in use, possibly even at high temperatures.
    Ceramic bodies can also be used when rapid changes in temperature occur during use, for example in bending-stressed valves, tools, pipes or other parts. But also for components in which high local compressive stresses are given in use, as in rolling or ball bearings, ceramic bodies prove themselves.
    Inherently, ceramic bodies have cracks on the surfaces, but also on the inside, which can be caused, in particular, by the production and / or reworking, for example grinding. Particularly in the case of post-processing, ceramic components are very sensitive, which is why ceramic components are generally often subject to cracks.
    Due to operational stresses, cracks can cause a ceramic component to fail. A crack can grow under load and therefore lead to unwanted material failure.
    Within the scope of the present invention, it was recognized that, depending on the load, a distinction can be made between subcritical and supercritical cracks. Subcritical small cracks, which are usually present in all ceramic bodies or components, do not propagate even under load during use and are therefore not critical. On the other hand, overcritically long cracks can cause them to grow rapidly under load during use and ultimately cause a failure of the component.
    It would be desirable to have a test method that readily allows ceramic bodies or components to be tested for field performance.
    From the state of the art so-called thermal shock processes have become known for ceramic components. In these processes, ceramic components are subjected to a thermal shock treatment prior to use for testing. In the context of the subject invention, a thermal shock treatment is understood to mean a spontaneous, ie in a short time, temperature increase or cooling of a ceramic component.
    A thermal shock treatment of ceramic components is known, for example, from DE 10 2010 017 351 A1, which describes a special method for testing ceramic components for solar absorbers, wherein the ceramic components are exposed within a short time of rapid heating to targeted components to failure bring. A detection of occurring cracks occurs during a subsequent cooling acoustically. If a growth of a crack is detected, the component is eliminated. The disadvantage here is that the appropriately designed test is relatively unspecific. Apart from the fact that this test is not suitable for mechanically highly stressed components, this test method has the particular disadvantage that even components are eliminated that could possibly be useful because only non-critical cracks are detected and no differentiation between critical and non-critical Cracks occurs.
    The object of the invention is to provide a method of the type mentioned, with which a ceramic body is reliably tested for suitability for use and wherein the
    Method is designed so that a variety of ceramic bodies can be subjected to a test.
    This object is achieved if determined in a method of the type mentioned based on a required breaking strength of the body in use a minimum temperature difference between the first temperature and the second temperature for the thermal shock treatment and the body is then subjected to the thermal shock treatment with at least the minimum temperature difference ,
    An advantage achieved by the invention is the fact that even with larger lot sizes 100% applicable overload test (proof test) is given, which is reliable for eliminating defective ceramic parts, but also other body with brittle, especially linear elastic, material behavior suitable, whereby a minimum value of a component strength is ensured. Among other things, the invention utilizes the knowledge that a breaking strength of a body with linearly elastic material behavior in use is determined by already existing near-surface or internal cracks. If a fracture strength of the body to be achieved in use is specified, a fracture toughness of the material is also used to determine a critical crack size for use, which represents a threshold value for the thermal shock treatment.
    As a basis for the interpretation of a test by thermal shock for materials with linear elastic material behavior is based on the Griffith / Irwin criterion, according to which
    where K is the stress intensity factor, Kte is the critical stress intensity factor, aRef is a reference stress in a non-cracked sample, a is the size of the crack, and Y is a geometric factor with which the geometry of the crack, stress field, and specimen is taken into account. Using the equation
    for the thermally induced voltages, where ath stands for the thermally induced voltages and F is a factor for the component geometry and quench parameters lying between 0 and 1, and where E is the Young's modulus, v is the Poisson's ratio and ΔΤ for the temperature difference in the thermal shock treatment, K can be calculated for the actual test in the presence of a crack with the length a as follows:
    To extend a crack or a defect occurs when the stress intensity K reaches the fracture toughness Kte of the material at the location of the crack or defect in accordance with equation (3). By reformulation of the above equation (3), idealized conditions such as temperature-independent material parameters and small changes in stress over the crack profile result in a given critical crack size for a given sample geometry and required (minimum) fracture strength corresponding to a certain critical temperature difference ATC in the thermal shock treatment. Under non-idealized conditions, this temperature difference can be calculated numerically. If the temperature difference is adjusted accordingly, it can be reliably ensured that all of the thermal shock treatment with the given temperature difference and positive tested body in use meet the stress profile. The test conditions ensure that during the thermal shock, stress distributions occur which come as close as possible to the load during use. On the other hand, bodies that led to impermissibly long cracks in the test procedure that could continue to grow in use can be eliminated.
    Appropriately, it is provided that the temperature difference is chosen so that the breaking strength of the body is exceeded in use with a tolerance. Preferably, this tolerance is low, so that is tested just above the final load. If, for example, a breaking strength of 800 MPa is required on the surface, this value can be increased, for example, to 880 MPa for the purposes of the test in order to additionally have a margin of tolerance. This ensures that only bodies are used that have already been tested for a higher load and have withstood this. The tolerance window upwards is usually not more than 20%, preferably not more than 15%, in particular not more than 10%, so that the body in the test method is not stressed significantly beyond the load during use. This ensures that the test conditions, with additional safety, correspond to the conditions of use.
    Although not mandatory, it has been found to be beneficial for certain applications when the body is heated to the first temperature until it is homogeneously at the first temperature in heated areas, and then rapidly cooled. This results in comparatively simple geometric conditions for the calculation of the minimum temperature difference and a simple process control by quenching. However, it is also possible that is dispensed with in a variant of the method on the setting of a constant or homogeneous first temperature in the body to be tested. In this case, only a near-surface region is heated to the first temperature and then rapidly cooled. The same applies if the thermal shock treatment consists of rapid heating. A rapid heating is especially in the case of components in question, in which application-dependent internal tensile stresses occur. As a result, compressive stresses occur in the outer region and tensile stresses in the interior. Insofar as only one point of a component specially stressed in use is to be tested, it may also be sufficient, regardless of the temperature control, to subject it only to the thermal shock treatment. For example, an area-wise rapid heating with a powerful laser can be done.
    The cracks can basically be detected in any way, for example acoustically or by vibration analysis. Cracks inside bodies can be detected by ultrasound or X-rays. In a test of a surface of a body, however, it is particularly preferable and easy if the cracks are optically detected. For this purpose, the cracks can be marked with a crack penetration color. In this case, the body to be tested is immersed, for example, in a colored liquid. The colored liquid remains after removal of the body from the liquid in the cracks and forms them. For this purpose, it is advantageously provided that the cracks are provided with a fluorescent crack penetration color, after which the cracks are made visible under ultraviolet light. The body or bodies to be tested then merely have to be immersed in a liquid and can then be inspected immediately. Body with too large cracks are then eliminated. This method is especially suitable for testing cracks on the surface.
    The method according to the invention is also particularly suitable for being used in a running production. For this purpose, it can be provided that the body is heated in an oven in the passage to the first temperature. For this purpose, for example, a conveyor may be provided, with which the body is transported through the oven. Subsequently, the body can be performed with the conveyor to a quenching agent. In particular, a fluid such as water or oil is suitable as a quenching agent. But also possible is a deterrent with a gas. In a gas quench, the gas can be applied to the body at elevated pressure.
    When the body (s) are delivered to a fluid as a quench with a delivery, the body (s) may simply be dropped into the fluid to achieve the thermal shock treatment. The fluid has a given second temperature. It is also within the scope of the invention that the thermal shock treatment is carried out with a heating and a subsequent quenching in a single device, in particular when working with a gas for a quenching of a first temperature. Heating can be done under any adjustable atmosphere, but also under vacuum. When quenching by means of a gas, it is preferred that the gas is applied under high pressure to the body, e.g. B. with a pressure of 2 bar or more.
    In a further process variant, an inhomogeneous temperature field is set on and / or in the body during the thermal shock treatment, which can be achieved by rapid heating in combination with rapid cooling.
    The thermal shock treatment may refer to a near-surface zone of the body or the entire body. It is also possible that the
    Thermal shock treatment is performed in a range in which there is a maximum load on the body in use. In particular, edges of a body can also be subjected to the thermal shock treatment.
    Further features, advantages and effects of the invention will become apparent from the embodiments illustrated below. In the drawings, to which reference is made, show:
    1 shows a device for thermal shock treatment.
    FIG. 2 shows a schematic representation of a temperature profile during a thermal shock treatment with a device according to FIG. 1; FIG.
    Fig. 3 is a schematic representation of the inspection of bodies with crack penetration.
    In Fig. 1, a device 2 is shown, which is designed in particular for carrying out a method according to the invention in a continuous pass. The device 2 comprises a furnace 3, which is designed as a continuous furnace. Within the furnace 3 is a conveyor 4, for example, a temperature-resistant conveyor belt out. On the conveyor 4 several ceramic body 1 are successively passed through the furnace 3. To the oven 3, a container 5 connects, in which water or other fluid is as a quenching agent. The bodies 1 are brought in the oven 3 on passage to a predetermined first temperature T1, until they ultimately have at the latest at the end of the furnace 3 homogeneously a first temperature T1. Subsequently, the bodies 1 are dropped into the quenching means having a predetermined second temperature T2 which is lower than the first temperature T1. As a result, a thermal shock treatment is brought about. To be able to remove the body 1 in a simple manner under continuous operation from the container 5, a sieve 7 or other means is arranged in this. If the sieve 7 is filled with bodies 1, they are removed with the sieve 7 and immersed in another container 6, which has a solution with a fluorescent crack penetration color. After a brief immersion, the bodies 1 are removed from this further container 6 and then examined optically for supercritically long cracks under a UV light source 8. Body 1, which exceed a permissible maximum crack size, are excreted.
    In Fig. 2 is a highly schematic of a temperature profile of the thermal shock treatment shown. In a first phase, the body or bodies 1 is heated to a predetermined temperature T1. After the body or bodies 1 have homogeneous the first temperature T1, they can be quenched in one or with a medium such as a fluid or gas to a second temperature T2. A temperature difference between the first temperature T1 and the second temperature T2 is designed so that it corresponds with a predetermined tolerance up a mechanical load of a body 1 in use.
    The bodies 1 may be any ceramic bodies 1. In particular, however, the method proves itself in ceramic bodies 1, which should have a particularly high quality on the surface for use, because a material failure can lead to complications that are expensive to fix. These may be, for example, ceramic implants such as artificial joints, dental prostheses or dental bridges, which may require additional surgery of the patient in case of failure. Other application examples relate to rolling elements for rolling bearings, which require complex repairs in case of material failure. In addition, other components such as valves, nozzle body, tool parts or ceramic circuit boards, functional components, etc. can be tested. Some of the components may also contain metallic or organic materials.
    In Fig. 3 is also shown schematically how the crack penetration color after the thermal shock treatment on bodies 1 represents. While a left body 1 has only small and thus acceptable cracks, which are not noticeably grown during the thermal shock treatment, a body 1 shown on the right has two major cracks, which would lead to material failure in use, because the cracks after the thermal shock treatment already are supercritical long. Therefore, the right body 1 is eliminated, whereas the left body 1 is operational.
    For example, a silicon nitride ceramic body 1 may be tested by a method as set forth above before being installed in ball bearings. For this purpose, the body 1 as described subjected to a test by means of thermal shock and then applied with crack penetration to detect supercritical long cracks and thus to be able to excrete defective or not suitable for use body 1 can. With a spherical geometry of the body 1 and a diameter of about 12.7 mm, a tolerance range of 70 MPa can be provided for a desired or required minimum strength of, for example, 700 MPa, so that the load is designed to be 770 MPa. To calculate the temperature difference required for this, the material properties such as density and thermal conductivity are assumed and the heat transfer coefficients are taken into account. For simple geometries such as spheres, the minimum temperature difference can then be calculated analytically if necessary. For example, results for the balls of silicon nitride with a diameter of 12.7 mm at 700 MPa required load and when immersed in moving water, a temperature difference of 700 ° C, so that the first temperature T1 at water as a quenching agent and at a second temperature T2 from 25 ° C to 725 ° C.
    For more complex geometries, a numerical calculation is required, with a presumed temperature-independent heat transfer coefficient depending on the material as a rule of thumb that corresponds to larger bodies 1, a temperature difference of 1 ° C about 2 MPa to 3 MPa. The smaller the bodies 1 of silicon nitride and the lower the quenching intensity, the lower the tension generated per degree of temperature difference in the body 1 in the colder sample part. In the warmer sample part, on the other hand, compressive stresses of a similar height as the tensile stresses occur in the colder sample part.
    It is understood that a test can also be performed in other ways. For example, body 1 can be partially or completely heated with a gas burner and then cooled with an air jet. Also, a thermal shock treatment can be limited to individual areas of a body 1, which is subject to particularly high loads in use.
    In addition to testing by means of a continuous furnace with subsequent quenching in an external unit and a test in a combined heating and quenching plant is advantageous. An example of this is the heating in a Vakuumhärteaggregat, which can be used in the heating with or without vacuum, followed by Hochdruckgasabschreckung.
    权利要求:
    Claims (15)
    [1]
    1. Method for testing a body (1) with brittle material behavior, in particular a ceramic body (1), on suitability for use, wherein the body (1) at least partially a thermal shock treatment by cooling or heating from a first temperature (T1) to a second Temperature (T2) subjected and existing cracks are detected, which is decided on the basis of the detected cracks on the fitness for use of the body (1), characterized in that based on a required breaking strength of the body (1) in use a minimum temperature difference between the first Temperature (T1) and the second temperature (T2) determined for the thermal shock treatment and the body (1) is then subjected to the thermal shock treatment with at least the minimum temperature difference.
    [2]
    2. The method according to claim 1, characterized in that the temperature difference is selected so that the breaking strength of the body (1) is exceeded in use with a tolerance, in particular a maximum tolerance of 20%.
    [3]
    3. The method according to claim 1 or 2, characterized in that the body (1) is heated to the first temperature (T1) until it has homogeneous in heated areas, the first temperature (T1), and then cooled rapidly.
    [4]
    4. The method according to any one of claims 1 to 3, characterized in that the cracks are optically detected.
    [5]
    5. The method according to claim 4, characterized in that the cracks are marked with a crack penetration color.
    [6]
    6. The method according to claim 4 or 5, characterized in that the cracks are provided with a fluorescent crack penetration color, after which the cracks are made visible under ultraviolet light.
    [7]
    7. The method according to any one of claims 1 to 6, characterized in that the body (1) in an oven (3) in the passage to the first temperature (T1) is heated.
    [8]
    8. The method according to claim 7, characterized in that the body (1) on a conveying means (4) through the furnace (3) is transported.
    [9]
    9. The method according to claim 8, characterized in that the body (1) with the conveying means (4) is guided to a quenching agent.
    [10]
    10. The method according to claim 9, characterized in that the quenching agent is a fluid.
    [11]
    11. The method according to any one of claims 1 to 6, characterized in that the thermal shock treatment is carried out with a heating and a subsequent quenching in a single device.
    [12]
    12. The method according to claim 11, characterized in that the quenching takes place by means of a gas under high pressure.
    [13]
    13. The method according to any one of claims 1 to 12, characterized in that in the thermal shock treatment, an inhomogeneous temperature field on and / or in the body (1) is adjusted.
    [14]
    14. The method according to any one of claims 1 to 13, characterized in that the thermal shock treatment is performed in a range in which a maximum load of the body (1) is given in use.
    [15]
    15. The method according to any one of claims 1 to 14, characterized in that edges of a body (1) are subjected to the thermal shock treatment.
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    同族专利:
    公开号 | 公开日
    WO2016023055A1|2016-02-18|
    EP3180610A1|2017-06-21|
    AT516082B1|2018-02-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP0129419A1|1983-06-17|1984-12-27|Ngk Insulators, Ltd.|A ceramic testing method|
    EP0872725A1|1997-04-15|1998-10-21|Eaton Corporation|Method for detecting defect in ceramic body and apparatus therefor|
    DE102007045636A1|2007-09-25|2009-04-02|Robert Bosch Gmbh|Method for determining the thermal shock robustness and material strength of brittle-failing materials|
    DE4419750C1|1994-06-06|1995-06-22|Siemens Ag|Ceramic component testing system for heat shield or turbine blade|
    JPH0886731A|1994-09-19|1996-04-02|Toshiba Corp|Temperature difference setting method in thermal shock test|
    DE102010017351B4|2010-06-14|2021-12-23|Saint-Gobain Industriekeramik Rödental GmbH|Method for testing ceramic components that can withstand high thermal loads|DE102016201647A1|2016-02-03|2017-08-03|Aktiebolaget Skf|Method for testing a ceramic component|
    CN108735856A|2017-04-21|2018-11-02|隆基绿能科技股份有限公司|Silicon chip detection method and its silicon wafer carrying device used|
    DE102019219552A1|2019-12-13|2021-06-17|Robert Bosch Gmbh|Method for testing a ceramic sensor element for an exhaust gas sensor|
    法律状态:
    2021-12-15| HA| Change or addition of new inventor|Inventor name: ROBERT DANZER, AT Effective date: 20211021 Inventor name: PETER SUPANCIC, AT Effective date: 20211021 |
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50560/2014A|AT516082B1|2014-08-11|2014-08-11|Method for testing a body with brittle material behavior|ATA50560/2014A| AT516082B1|2014-08-11|2014-08-11|Method for testing a body with brittle material behavior|
    PCT/AT2015/050194| WO2016023055A1|2014-08-11|2015-08-10|Method for testing a body with brittle material behavior|
    EP15756545.8A| EP3180610A1|2014-08-11|2015-08-10|Method for testing a body with brittle material behavior|
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