O-ring reliability testing device and testing method

Abstract

This invention relates to the field of O-ring testing technology, specifically an O-ring reliability testing device and method. The device includes an upper flange, a lower flange, an upper test cylinder, and a lower test cylinder. The upper flange has a through-hole in its center. The lower part of the upper test cylinder passes through the mounting hole and its outer edge sits on the upper side of the upper flange. A first groove is provided on the upper side of the upper test cylinder, within which a force sensor is installed. A pressure application mechanism is located above the force sensor. The upper test cylinder has a medium hole and a pressure gauge probe port, with a pressure gauge connected to the probe port. An annular extrusion surface is provided at the lower end of the upper test cylinder. A lower flange is located below the upper flange, and a second groove is provided in the center of the lower flange. This invention has a reasonable and compact structure and is easy to use. By synchronously, in-situ, and continuously monitoring the contact stress relaxation behavior and minute leakage rate of the O-ring, it provides technical support for quantifying the critical stress threshold for seal failure and establishing an accurate life prediction model.

Description

Technical Field

[0001] This invention relates to the field of O-ring testing technology, specifically an O-ring reliability testing device and method. Background Technology

[0002] With the rapid commercialization of clean energy technologies, including hydrogen, methanol, and liquid ammonia, O-rings, as key components in storage containers, gas filling guns, and pipeline valves, directly impact the safety of the entire system due to their reliability in high-pressure fluid environments. In actual operating conditions, O-rings not only withstand fluid pressures as high as 35 MPa or even exceeding 70 MPa, but also face chemical aging caused by fluid-specific permeation and swelling, as well as the inherent physical stress relaxation (CSR) phenomenon of rubber materials. Stress relaxation refers to the characteristic of rubber's resilience (contact stress) gradually decreasing over time under constant compression. When the contact stress decreases below the medium pressure, the seal fails. Therefore, developing a testing device that can realistically simulate high-pressure fluid conditions and simultaneously monitor the evolution of seal contact force and leakage behavior is an urgent need in the industry.

[0003] Currently, performance testing for O-rings is mainly divided into material-level testing and component-level testing, but existing technical solutions have significant limitations in monitoring stress relaxation caused by high-pressure fluid coupling.

[0004] Firstly, there is the compression aging test technique based on standard fixtures (such as ISO 3384 or ASTM D6147). These devices typically consist of parallel steel plates and fastening components. However, this design has several drawbacks: firstly, the test objects are often standard rubber blocks or cylindrical specimens, rather than actual O-ring seals, causing them to ignore the crucial influence of annular geometry and size effects on contact stress distribution; secondly, these devices usually expose the entire sample to an environmental chamber, failing to construct a true sealing interface pressure difference state of "high-pressure fluid on one side and atmosphere on the other," resulting in test results that only reflect the material's bulk relaxation characteristics under no-medium pressure, severely deviating from actual service conditions.

[0005] Secondly, there are O-ring component aging and deformation testing devices based on static compression constraints. These devices utilize physical means such as thread engagement or mechanical pressing to construct a fixed geometric space to achieve forced clamping of the O-ring. However, the shortcomings of this design are as follows: On the one hand, its structure is limited to simulating the mechanical clamping of the O-ring in the initial assembly state, completely stripping away the "internal sealing" mechanism under actual working conditions. This results in the O-ring lacking the "self-tightening" effect driven by the internal pressure of the medium, and the stress mode is seriously out of sync with the real high-pressure sealing environment. On the other hand, these devices usually focus on examining the static deformation of the material itself, such as permanent compression deformation. They cannot measure the actual medium leakage rate, nor do they have in-situ monitoring methods for stress relaxation processes, making it difficult to reveal the dynamic evolution mechanism of material failure due to contact stress attenuation during long-term service.

[0006] Finally, there are pressure testing devices based on simulated containers. These devices typically construct a sealed autoclave or simulated chamber, using O-rings as end cap seals. While this can realistically replicate the internal high-pressure fluid environment and operating conditions, this design has several drawbacks: First, its monitoring logic exhibits significant lag, passively identifying "leakage" only through a drop in pressure gauge readings, essentially capturing only the final moment of failure. Second, these devices have a technological blind spot, completely lacking in-situ monitoring methods for contact stress relaxation. This leaves the contact force attenuation process caused by cross-linking breakage or physical relaxation within the rubber in a black box, unable to identify the significantly reduced sealing margin of the O-ring before leakage occurs, and struggling to establish a dynamic correlation between microscopic aging and macroscopic sealing performance. Summary of the Invention

[0007] This invention provides an O-ring reliability testing device and method, which overcomes the shortcomings of the prior art and effectively solves the problem of significant limitations in the performance testing of existing O-rings.

[0008] One of the technical solutions of the present invention is achieved through the following measures: an O-ring reliability testing device, comprising an upper flange, a lower flange, an upper test cylinder, and a lower test cylinder. The upper flange has a through mounting hole in the middle, the lower part of the upper test cylinder passes through the mounting hole and its outer edge sits on the upper side of the upper flange, the upper side of the upper test cylinder has a first slot, a force sensor is provided in the first slot, a pressure application mechanism is provided on the upper side of the force sensor, the upper test cylinder has a medium hole and a pressure gauge probe port, the pressure gauge probe port is connected to a pressure gauge, the lower end of the upper test cylinder has an annular extrusion surface, the lower flange is provided below the upper flange, the lower flange has a second slot in the middle, the lower test cylinder sits in the second slot, the upper side of the lower test cylinder has an annular groove corresponding to the position of the extrusion surface, and the upper flange and the lower flange are fixed by fastening bolts.

[0009] The following are further optimizations and / or improvements to the above-mentioned technical solution: Preferably, the pressure application mechanism includes a loading gland and a loading bolt. The loading gland has at least three threaded holes evenly distributed on it. The upper test cylinder corresponding to the position of the threaded hole is provided with a through hole. The lower end of the loading bolt passes through the threaded hole and the through hole in sequence and is threadedly connected to the upper test cylinder.

[0010] Preferably, it includes three annular grooves: the inner annular groove is a test groove, the middle one is a leakage groove, the leakage groove is connected to a helium mass spectrometer leak detector or a micro flow meter through a pipeline, and the outer one is a sealing groove, with an outer sealing ring installed inside the sealing groove.

[0011] Preferably, a limiter is provided between the upper flange and the lower flange.

[0012] Preferably, three force sensors are evenly distributed in the first slot.

[0013] The second technical solution of the present invention is achieved through the following measures: a testing method for an O-ring reliability testing device, which is carried out according to the following steps. Insert the selected lower test cylinder into the second slot of the lower flange, and place the O-ring to be tested coated with grease into the inner annular groove; The upper test cylinder is placed on the O-ring through the upper flange, and three force sensors are placed into the first slot of the upper test cylinder. The loading gland and upper flange are initially fixed with loading bolts, and the upper flange and lower flange are fixed with fastening bolts. The pressure limiter is tightened. After installation, the initial contact force of the force sensor is adjusted, and the tightening degree of the loading bolts is adjusted to control the clamping force of the loading gland. When the test cylinder needs to be filled with gas, first use nitrogen to replace the air in the test cylinder three times, and then fill it with the target gas to the target pressure. The data acquisition system synchronously records force sensor values ​​at a frequency of 1Hz. F sensor Pressure gauge pressure and leakage rate of helium mass spectrometer leak detector or microflow meter, when F t The experiment will be terminated when the degradation reaches the preset failure threshold or when macroscopic leakage occurs.

[0014] Preferably, the value read by the force sensor F sensor Including the elasticity of O-rings F seal The axial force exerted on the upper test cylinder by the superimposed internal and external pressure difference Pressurize the interior to P in External filling pressure is P out , A in and A outThese represent the effective areas of internal and external pressure, respectively, and the values ​​read by the stripping force sensor. F sensor O-ring rebound force under dual pressure fields F seal .

[0015] Preferably, based on the resilience F seal Construct a feature lifetime prediction model: In the formula, The degree of aging is defined by the reduction of resilience. Initial rebound force, real-time rebound force, activation energy Ea (unit: J / mol), Boltzmann constant K, absolute temperature T, P H Fluid pressure, β pressure sensitivity index, t running time, η characteristic lifetime (related to temperature and pressure), m shape parameter, γ fluid pressure acceleration index, F(t) cumulative failure probability up to time t; The construction process is as follows, under a given temperature T and fluid pressure P H Accelerated aging tests were conducted on multiple O-ring samples under the specified conditions. This indicates the real-time rebound force, which is the sum of the real-time rebound force and the initial rebound force. By comparison, the degree of aging based on the decrease in resilience can be obtained. Artificially set failure criteria, for example when or equivalent When the O-ring is considered to have failed, the time corresponding to the first time each sample reaches this failure criterion is specified. To obtain the failure lifetime data of the sample under the specified temperature and pressure conditions, the above process was repeated for multiple samples to obtain a set of failure times. This set of failure lifetime data was then substituted into the Weibull distribution model. By performing a fitting, the shape parameter m and characteristic lifetime η are obtained, where η is the value at the given temperature T and fluid pressure P. H The characteristic lifetime under the given conditions represents the time corresponding to a cumulative failure probability of approximately 63.2%. If we further consider the accelerating effects of different temperatures and fluid pressures on lifetime, we can substitute the η obtained from fitting under different operating conditions into the equation. And taking its natural logarithm, we get Finally, with As the dependent variable, with Perform multiple linear regression on the independent variables, where the intercept corresponds to The slope of the term corresponds to The slope of the term corresponds to Therefore, we can obtain the results separately. Finally, a characteristic lifetime prediction model that varies with temperature and fluid pressure was established.

[0016] Preferably, the stress relaxation behavior of the O-ring under high-pressure fluid environment is predicted, and its stress relaxation function is as follows: In the formula, Let be the equivalent seal holding stress at time t. Initial compressive stress; E i ,τ i， The elastic modulus and relaxation time constant of the i-th Maxwell element, k H The attenuation factor, C, of ​​the mechanical properties of materials due to fluid infiltration. H (t) represents the fluid concentration inside the O-ring at time t, which can be determined using Fick's second law: D H The diffusion coefficient of the fluid in rubber increases with increasing temperature. Initial conditions... Boundary condition: Surface fluid partial pressure P H To remain constant; The construction process is as follows: the rebound force of the O-ring is collected under constant compression ratio and high pressure fluid environment. The attenuation curve is calculated, and based on the equivalent force-bearing area A between the O-ring and the sealing surface, the measured rebound force is converted into a stress attenuation curve, i.e. Then, a creep-relaxation-fluid diffusion coupled prediction model is established, in which the generalized Maxwell model is used to describe the viscoelastic stress relaxation behavior of rubber materials, expressed as follows: At the same time, Fick's second law is adopted. Calculate the concentration distribution C of the high-pressure fluid inside the O-ring over time. H (t), and then introduce the fluid attenuation coefficient k H The coupled stress prediction model is obtained. Subsequently, the measured stress attenuation curve was used. Construct an error function for the target data. The relaxation unit modulus Ei, relaxation time constant τi, and diffusion coefficient D are continuously adjusted using nonlinear least squares method, genetic algorithm, or particle swarm optimization algorithm. H and the fluid attenuation coefficient k H This minimizes the error function J. Once the fitting error between the model's predicted curve and the measured curve meets a set threshold, the identified model parameters are obtained. These parameters are then substituted back into the coupled model to calculate the stress at any time t. and corresponding rebound force This enables the prediction of stress relaxation and rebound force attenuation of O-rings under long-term high-pressure fluid conditions.

[0017] This invention has a reasonable and compact structure and is easy to use. By synchronously, in-situ and continuously monitoring the contact stress relaxation behavior and trace leakage rate of O-rings, it provides technical support for quantifying the critical stress threshold of seal failure and establishing an accurate life prediction model. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the front cross-sectional structure according to an embodiment of the present invention.

[0019] Appendix Figure 2 This is a structural diagram showing the partial decomposition of the present invention.

[0020] The codes in the attached diagram are as follows: 1 for upper flange, 2 for lower flange, 3 for upper test cylinder, 4 for lower test cylinder, 5 for mounting hole, 6 for first slot, 7 for force sensor, 8 for medium hole, 9 for pressure gauge probe, 10 for annular extrusion surface, 11 for second slot, 12 for limiter, 13 for loading gland, 14 for loading bolt, 15 for test groove, 16 for leakage groove, 17 for sealing groove, and 18 for outer sealing ring. Detailed Implementation

[0021] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0022] In this invention, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as front, back, top, bottom, left, right, etc. The positional relationships are determined based on the layout direction of the attached diagram in the instruction manual.

[0023] The present invention will be further described below with reference to embodiments and accompanying drawings: As attached Figure 1 , 2 As shown, the O-ring reliability testing device includes an upper flange 1, a lower flange 2, an upper test cylinder 3, and a lower test cylinder 4. The upper flange 1 has a through mounting hole 5 in the middle. The lower part of the upper test cylinder 3 passes through the mounting hole 5 and its outer edge sits on the upper side of the upper flange 1. The upper side of the upper test cylinder 3 has a first slot 6, and a force sensor 7 is installed in the first slot 6. A pressure application mechanism is installed on the upper side of the force sensor 7. The upper test cylinder 3 has a medium hole 8 and a pressure gauge detection port 9. A pressure gauge is connected to the pressure gauge detection port 9. The lower end of the upper test cylinder 3 has an annular extrusion surface 10. The lower flange 2 is located below the upper flange 1. The lower flange 2 has a second slot 11 in the middle. The lower test cylinder 4 is seated in the second slot 11. The upper side of the lower test cylinder 4 has an annular groove corresponding to the position of the extrusion surface. The upper flange 1 and the lower flange 2 are fixed by fastening bolts.

[0024] Depending on the requirements, the filling medium can be selected, such as liquid or gas. For example, during testing, the entire testing device can be placed in an external environment simulation device (high-temperature autoclave, high-temperature precision oven, or oil bath). While maintaining an internal hydrogen-filled state, multi-physical stress fields such as high-temperature oxygen, corrosive liquid immersion (such as H2S, brine, or acidic gas) can be applied simultaneously. A temperature cycling spectrum can be set, such as raising the temperature from room temperature to 150°C, maintaining it for 48 hours, and then cooling it down to simulate accelerated aging and stress corrosion cracking. The force sensor 7 uses a high-temperature resistant silicon-on-insulator pressure sensor 7, which can operate stably for a long time at 175°C without additional cooling measures.

[0025] The main materials of the upper flange 1, lower flange 2, upper test cylinder 3, and lower test cylinder 4 can be Hastelloy C-276 or Inconel 718. Alternatively, depending on requirements, the lower test cylinder 4 component 3 can be replaced with a transparent material, such as sapphire glass or thickened PMMA under low-pressure conditions. Combined with a bottom camera, this allows for observation of the contact width change of the O-ring during the extrusion process, achieving dual verification through both optical and mechanical means.

[0026] This invention places the force sensor 7 in the non-medium-contact area (atmospheric environment) at the top of the device, completely avoiding corrosion and penetration damage to the force sensor 7 by the high-pressure medium; the medium hole 8 is set on the side wall of the upper test cylinder 3, making the air path connection more compact. Compared with slotting the flange joint surface, this design avoids the sealing surface being interrupted by the air path, improving the reliability of the high-pressure seal; a split design that decouples the load-bearing component and the test component is adopted. For O-rings of different specifications, only a low-cost test cylinder needs to be replaced to share the force sensor 7 and other components, which greatly reduces the cost and cycle of a single experiment. By monitoring the pressure curve of the pressure gauge, the failure status of the O-ring is judged. When the internal pressure suddenly drops, it indicates that the O-ring has failed.

[0027] The above-mentioned O-ring reliability testing device can be further optimized and / or improved according to actual needs: As attached Figure 1 , 2 As shown, the pressure application mechanism includes a loading gland 13 and a loading bolt 14. The loading gland 13 has at least three threaded holes evenly distributed on it. The upper test cylinder 3 corresponding to the threaded hole position has a through hole. The lower end of the loading bolt 14 passes through the threaded hole and the through hole in sequence and is threadedly connected to the upper test cylinder 3. During testing, the axial force applied to the O-ring can be adjusted by tightening the loading bolt 14 diagonally in stages.

[0028] As attached Figure 1 , 2As shown, the device includes three annular grooves: the innermost annular groove is the test groove 15; the middle groove is the leakage groove 16, which is connected to a helium mass spectrometer leak detector or a micro-flowmeter via a pipeline; and the outer groove is the sealing groove 17, within which an outer sealing ring 18 is installed. When it is necessary to observe the influence of the external high-pressure medium, the outer sealing ring 18 is removed; when it is not necessary to observe the external high-pressure medium, the outer perimeter is sealed by the outer sealing ring 18. When the tested O-ring seal fails and the internal medium leaks, the medium condition collected by the helium mass spectrometer leak detector or the micro-flowmeter is compared with the pressure gauge readings to determine the failure condition.

[0029] As attached Figure 1 , 2 As shown, a limit switch 12 is provided between the upper flange 1 and the lower flange 2. The limit switch 12 is introduced to eliminate human error and prevent overload of the force sensor 7. The height of the limit switch 12... H limit After rigorous calculation: ,in, H closed This is the reference height when the device is closed. δ Set the target compression ratio (e.g., 20%). h ring The diameter of the O-ring cross-section is specified. During installation, simply tighten the fastening bolts until the upper and lower flanges 2 rigidly contact the limiters 12 to ensure that the O-ring compression ratio is precisely locked at the preset value and will not drift due to vibration during long-term testing.

[0030] As attached Figure 1 , 2 As shown, three force sensors 7 are evenly distributed in the first slot 6. The three force sensors 7 can monitor the force in different directions. When the force is different, the tightness of the loading bolt 14 at the corresponding position is adjusted to ensure that the force in each direction is similar.

[0031] As attached Figure 1 , 2 As shown, proceed with the following steps. Insert the selected lower test cylinder 4 into the second slot 11 of the lower flange 2, and place the O-ring to be tested coated with grease into the inner annular groove. The upper test cylinder 3 passes through the upper flange 1 and is placed on the O-ring. Three force sensors 7 are placed into the first slot 6 of the upper test cylinder 3. The loading gland 13 and the upper flange 1 are initially fixed by the loading bolts 14, and the upper flange 1 and the lower flange 2 are fixed by the fastening bolts. The pressure limiter 12 is tightened. After installation, the initial contact force of the force sensor 7 is adjusted, and the tightening degree of the loading bolts 14 is adjusted to control the clamping force of the loading gland 13. When gas needs to be filled into the upper test cylinder 3, the air inside the upper test cylinder 3 is first replaced three times with nitrogen, and then the target gas is filled to the target pressure; the data acquisition system synchronously records the values ​​of the force sensor 7 at a frequency of 1Hz. F sensor Pressure gauge pressure and leakage rate of helium mass spectrometer leak detector or microflow meter, when F t The experiment will be terminated when the degradation reaches the preset failure threshold or when macroscopic leakage occurs.

[0032] As attached Figure 1 , 2 As shown, the values ​​read by the force sensor F sensor Including the elasticity of O-rings F seal The axial force exerted on the upper test cylinder by the superimposed internal and external pressure difference Pressurize the interior to P in External filling pressure is P out , A in and A out These represent the effective areas of internal and external pressure, respectively, and the values ​​read by the stripping force sensor 7. F sensor O-ring rebound force under dual pressure fields F seal .

[0033] As attached Figure 1 , 2 As shown, based on the rebound force F seal Construct a feature lifetime prediction model: In the formula, The degree of aging is defined by the reduction of resilience. Initial rebound force, True resilience after aging time t, activation energy Ea (unit: J / mol), Boltzmann constant K, absolute temperature T, P H Fluid pressure, β pressure sensitivity index, t running time, η characteristic lifetime (related to temperature and pressure), m shape parameter, γ fluid pressure acceleration index, F(t) cumulative failure probability up to time t; The construction process is as follows, under a given temperature T and fluid pressure P H Accelerated aging tests were conducted on multiple O-ring samples under the specified conditions. This indicates the real-time rebound force, which is the sum of the real-time rebound force and the initial rebound force. By comparison, the degree of aging based on the decrease in resilience can be obtained. Artificially set failure criteria, for example when or equivalent When the O-ring is considered to have failed, the time corresponding to the first time each sample reaches this failure criterion is specified. To obtain the failure lifetime data of the sample under the specified temperature and pressure conditions, the above process was repeated for multiple samples to obtain a set of failure times. This set of failure lifetime data was then substituted into the Weibull distribution model. By performing a fitting, the shape parameter m and characteristic lifetime η are obtained, where η is the value at the given temperature T and fluid pressure P. H The characteristic lifetime under the given conditions represents the time corresponding to a cumulative failure probability of approximately 63.2%. If we further consider the accelerating effects of different temperatures and fluid pressures on lifetime, we can substitute the η obtained from fitting under different operating conditions into the equation. And taking its natural logarithm, we get Finally, with As the dependent variable, with Perform multiple linear regression on the independent variables, where the intercept corresponds to The slope of the term corresponds to The slope of the term corresponds to Therefore, we can obtain the results separately. Finally, a characteristic lifetime prediction model that varies with temperature and fluid pressure was established.

[0034] The specific operation process is as follows: First, the assembled test device, filled with fluid at the target pressure, is placed in a high-temperature environmental chamber, and a thermo-oxidative aging test is conducted using a set temperature cycling spectrum. The O-ring reliability test device adopts a split structure and limiter 12 design to ensure that the O-ring compression remains constant under drastic temperature changes. During the test, the system synchronously records the force sensor 7 value, cavity pressure, and leakage rate at a frequency of 1Hz. At a preset time point, the experiment is paused, and O-ring samples are removed to measure their hardness, tensile strength, and elongation at break, etc., to quantify the degree of aging. Simultaneously, an online mass spectrometer connected to the side wall vent is used to monitor fluid leakage signals to determine whether penetration failure has occurred. Multiple sets of aging degree-time data under different temperatures and pressures are subjected to nonlinear regression to fit parameters such as activation energy and pressure sensitivity index in the Arrhenius double exponential aging rate equation, and a lifetime prediction model is constructed by combining it with the Weibull distribution. Finally, the remaining aging lifetime curve is output to evaluate the long-term reliability of the O-ring under actual working conditions.

[0035] As attached Figure 1 , 2 As shown, the stress relaxation behavior of the O-ring under high-pressure fluid environment is predicted, and its stress relaxation function is as follows: In the formula, Let be the equivalent seal holding stress at time t. Initial compressive stress; E i ,τ i， The elastic modulus and relaxation time constant of the i-th Maxwell element, k H The attenuation factor, C, of ​​the mechanical properties of materials due to fluid infiltration. H (t) represents the fluid concentration inside the O-ring at time t, which can be determined using Fick's second law: D H The diffusion coefficient of the fluid in rubber increases with increasing temperature. Initial conditions... Boundary condition: Surface fluid partial pressure P H To remain constant; The construction process is as follows: the rebound force of the O-ring is collected under constant compression ratio and high pressure fluid environment. The attenuation curve is calculated, and based on the equivalent force-bearing area A between the O-ring and the sealing surface, the measured rebound force is converted into a stress attenuation curve, i.e. Then, a creep-relaxation-fluid diffusion coupled prediction model is established, in which the generalized Maxwell model is used to describe the viscoelastic stress relaxation behavior of rubber materials, expressed as follows: At the same time, Fick's second law is adopted. Calculate the concentration distribution C of the high-pressure fluid inside the O-ring over time. H (t), and then introduce the fluid attenuation coefficient k H The coupled stress prediction model is obtained. Subsequently, the measured stress attenuation curve was used. Construct an error function for the target data. The relaxation unit modulus Ei, relaxation time constant τi, and diffusion coefficient D are continuously adjusted using nonlinear least squares method, genetic algorithm, or particle swarm optimization algorithm. H and the fluid attenuation coefficient k H This minimizes the error function J. Once the fitting error between the model's predicted curve and the measured curve meets a set threshold, the identified model parameters are obtained. These parameters are then substituted back into the coupled model to calculate the stress at any time t. and corresponding rebound force This enables the prediction of stress relaxation and rebound force attenuation of O-rings under long-term high-pressure fluid conditions.

[0036] In high-pressure fluid environments, O-ring materials undergo stress relaxation due to prolonged pressure, leading to a decrease in sealing pressure and potentially causing leakage. Since the stress attenuation curve obtained by dividing the measured rebound force by the stress area only reflects the mechanical changes under the current test conditions, it cannot reveal the coupling effect between viscoelastic relaxation, creep deformation, and high-pressure fluid diffusion weakening within the O-ring material. Furthermore, it is difficult to extrapolate and predict the sealing performance degradation over longer periods or under different pressure, temperature, and medium conditions. Therefore, a creep-relaxation-fluid diffusion coupled model is needed to fit the measured curve and perform parameter inversion to obtain physically meaningful model parameters and achieve long-term stress relaxation prediction.

[0037] The specific steps are as follows: First, assemble the device at room temperature: Place the O-ring to be tested in the annular groove of the lower test cylinder 4, cover it with the upper test cylinder 3 assembly, and install three force sensors 7 in the first slot 6 of the force sensor 7 at the top of the upper test cylinder 3; then, fit the upper flange 1 assembly, insert the limiter 12, and tighten it in a diagonal sequence (i.e., tighten it gradually in several rounds according to the "diagonal cross" sequence) until the limiter 12 is completely pressed shut. At this time, the reading of the force sensor 7 is the initial contact force. Next, replace the air in the chamber with nitrogen three times through the side wall air passage, fill it with high-pressure fluid to the target pressure, and push the entire device into the constant temperature chamber to start the test. The data acquisition system continuously records the output value of the force sensor 7, the fluid pressure in the chamber, and possible leakage signals at a frequency of 1Hz. Throughout the testing cycle, no destructive sampling is required; the relaxation process can be characterized solely by real-time mechanical response data. The measured force decay curve is substituted into the viscoelastic-hydrogen diffusion coupling model, and the hydrogen concentration is calculated using Fick's second law. Maxwell element parameters, hydrogen attenuation coefficient, and diffusion coefficient are then identified through inversion. This allows for accurate prediction of the stress decay of the O-ring under long-term high-pressure fluid conditions and determination of whether it falls below the critical stress threshold required to maintain a seal, thereby assessing the sealing reliability of the O-ring during long-term service.

[0038] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. An O-ring reliability testing device, characterized in that... The device includes an upper flange, a lower flange, an upper test cylinder, and a lower test cylinder. The upper flange has a through mounting hole in the middle. The lower part of the upper test cylinder passes through the mounting hole and its outer edge sits on the upper side of the upper flange. The upper side of the upper test cylinder has a first slot, in which a force sensor is installed. A pressure application mechanism is installed on the upper side of the force sensor. The upper test cylinder has a medium hole and a pressure gauge probe port, which is connected to a pressure gauge. The lower end of the upper test cylinder has an annular extrusion surface. The lower flange is located below the upper flange. The lower flange has a second slot in the middle, in which the lower test cylinder sits. The upper side of the lower test cylinder has an annular groove corresponding to the extrusion surface. The upper flange and the lower flange are fixed by fastening bolts.

2. The O-ring reliability testing device according to claim 1, characterized in that... The pressure application mechanism includes a loading gland and a loading bolt. The loading gland has at least three threaded holes evenly distributed on it. The upper test cylinder corresponding to the position of the threaded hole is provided with a through hole. The lower end of the loading bolt passes through the threaded hole and the through hole in sequence and is then threadedly connected to the upper test cylinder.

3. The O-ring reliability testing device according to claim 1 or 2, characterized in that... It includes three annular grooves: the inner annular groove is the test groove, the middle one is the leakage groove, the leakage groove is connected to a helium mass spectrometer leak detector or a micro flow meter through a pipeline, and the outer one is the sealing groove, with an outer sealing ring installed inside the sealing groove.

4. The O-ring reliability testing device according to claim 1 or 2, characterized in that... A limiter is provided between the upper flange and the lower flange; or / and, three force sensors are evenly distributed in the first slot.

5. The O-ring reliability testing device according to claim 3, characterized in that... A limiter is provided between the upper flange and the lower flange; or / and, three force sensors are evenly distributed in the first slot.

6. A testing method using the O-ring reliability testing device described in claim 5, characterized in that... Follow these steps. Insert the selected lower test cylinder into the second slot of the lower flange, and place the O-ring to be tested coated with grease into the inner annular groove; The upper test cylinder is placed on the O-ring through the upper flange, and three force sensors are placed into the first slot of the upper test cylinder. The loading gland and upper flange are initially fixed with loading bolts, and the upper flange and lower flange are fixed with fastening bolts. The pressure limiter is tightened. After installation, the initial contact force of the force sensor is adjusted, and the tightening degree of the loading bolts is adjusted to control the clamping force of the loading gland. When the test cylinder needs to be filled with gas, first use nitrogen to replace the air in the test cylinder three times, and then fill it with the target gas to the target pressure. The data acquisition system synchronously records force sensor values ​​at a frequency of 1Hz. F sensor Pressure gauge pressure and leakage rate of helium mass spectrometer leak detector or microflow meter, when F t The experiment will be terminated when the degradation reaches the preset failure threshold or when macroscopic leakage occurs.

7. The test method according to claim 6, characterized in that... Values ​​read by the force sensor F sensor Including the elasticity of O-rings F seal The axial force exerted on the upper test cylinder by the superimposed internal and external pressure difference Pressurize the interior to P in External filling pressure is P out , A in and A out These represent the effective areas of internal and external pressure, respectively, and the values ​​read by the stripping force sensor. F sensor O-ring rebound force under dual pressure fields F seal .

8. The test method according to claim 7, characterized in that... Based on rebound force F seal Construct a feature lifetime prediction model: In the formula, The degree of aging is defined by the reduction of resilience. Initial rebound force, Real-time rebound force, Ea activation energy (unit: J / mol), K Boltzmann constant, T absolute temperature, P H Fluid pressure, β pressure sensitivity index, t running time, η characteristic lifetime (related to temperature and pressure), m shape parameter, γ fluid pressure acceleration index, F(t) cumulative failure probability up to time t; The construction process is as follows, under a given temperature T and fluid pressure P H Accelerated aging tests were conducted on multiple O-ring samples under the specified conditions. This indicates the real-time rebound force, which is the sum of the real-time rebound force and the initial rebound force. By comparison, the degree of aging based on the decrease in resilience can be obtained. Artificially set failure criteria, for example when or equivalent When the O-ring is considered to have failed, the time corresponding to the first time each sample reaches this failure criterion is specified. To obtain the failure lifetime data of the sample under the specified temperature and pressure conditions, the above process was repeated for multiple samples to obtain a set of failure times. This set of failure lifetime data was then substituted into the Weibull distribution model. By performing a fitting, the shape parameter m and characteristic lifetime η are obtained, where η is the value at the given temperature T and fluid pressure P. H The characteristic lifetime under the given conditions represents the time corresponding to a cumulative failure probability of approximately 63.2%. If we further consider the accelerating effects of different temperatures and fluid pressures on lifetime, we can substitute the η obtained from fitting under different operating conditions into the equation. And taking its natural logarithm, we get Finally, with As the dependent variable, with Perform multiple linear regression on the independent variables, where the intercept corresponds to The slope of the term corresponds to The slope of the term corresponds to Therefore, we can obtain the results separately. Finally, a characteristic lifetime prediction model that varies with temperature and fluid pressure was established.

9. The test method according to claim 7, characterized in that... The stress relaxation behavior of the O-ring under high-pressure fluid environment is predicted, and its stress relaxation function is shown below: In the formula, Let be the equivalent seal holding stress at time t. Initial compressive stress; E i ,τ i The elastic modulus and relaxation time constant of the i-th Maxwell element, k H The attenuation factor, C, of ​​the mechanical properties of materials due to fluid infiltration. H (t) represents the fluid concentration inside the O-ring at time t, which can be determined using Fick's second law: D H The diffusion coefficient of the fluid in rubber increases with increasing temperature. Initial conditions: C H (0) = 0, Boundary condition: Surface fluid partial pressure P H To remain constant; The construction process is as follows: the rebound force of the O-ring is collected under constant compression ratio and high pressure fluid environment. The attenuation curve is calculated, and based on the equivalent force-bearing area A between the O-ring and the sealing surface, the measured rebound force is converted into a stress attenuation curve, i.e. Then, a creep-relaxation-fluid diffusion coupled prediction model is established, in which the generalized Maxwell model is used to describe the viscoelastic stress relaxation behavior of rubber materials, expressed as follows: At the same time, Fick's second law is adopted. Calculate the concentration distribution C of the high-pressure fluid inside the O-ring over time. H (t), and then introduce the fluid attenuation coefficient k H The coupled stress prediction model is obtained. Subsequently, the measured stress attenuation curve was used. Construct an error function for the target data. The relaxation unit modulus Ei, relaxation time constant τi, and diffusion coefficient D are continuously adjusted using nonlinear least squares method, genetic algorithm, or particle swarm optimization algorithm. H and the fluid attenuation coefficient k H This minimizes the error function J. Once the fitting error between the model's predicted curve and the measured curve meets a set threshold, the identified model parameters are obtained. These parameters are then substituted back into the coupled model to calculate the stress at any time t. and corresponding rebound force This enables the prediction of stress relaxation and rebound force attenuation of O-rings under long-term high-pressure fluid conditions.

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