O-shaped rubber sealing ring service life prediction method coupling temperature and continuous compression stress relaxation

Abstract

The invention relates to a temperature and continuous compression stress relaxation coupled O-shaped rubber sealing ring service life prediction method, and belongs to the technical field of nuclear power equipment material detection. According to the method, compression stress relaxation tests of the O-shaped rubber sealing ring are carried out at different temperatures, relational data of compression stress relaxation, time and temperature are obtained, a physical information neural network is adopted for data fitting, and a quantitative prediction model is established. Compression stress relaxation is used as a service life criterion, and the service life of the O-shaped rubber sealing ring under actual service conditions can be quickly predicted according to different temperatures and failure standards. The method overcomes the problems that a traditional service life prediction method is limited by mechanical property indexes and is insufficient in accuracy, efficient and accurate service life prediction oriented to engineering application is achieved, and the method is suitable for the fields such as nuclear power and the like which have extremely high requirements for sealing reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear power equipment material detection, and more particularly relates to a method for predicting the service life of an O-shaped rubber sealing ring by coupling temperature and continuous compression stress relaxation. BACKGROUND

[0002] O-shaped rubber sealing rings are widely used in industrial production and daily life, and their long-term reliability plays a key role in ensuring normal and safe operation of equipment and avoiding leakage of high-temperature and high-pressure, toxic and harmful, and even radioactive substances. Therefore, it is very important and necessary to develop a reasonable, reliable, and accurate service life prediction method suitable for the actual service conditions of O-shaped rubber sealing rings.

[0003] Traditional service life prediction methods for O-shaped rubber sealing rings are mainly based on thermal-oxidative aging acceleration experiments and tests of the mechanical properties of materials after aging, such as elongation at break, tensile strength at break, hardness, and compression set. These performance test methods are simple, low-cost, and have good applicability in general cases. However, for O-shaped rubber sealing rings used in extreme environments, such as aerospace, deep sea, polar regions, and nuclear energy, their safety is of more concern, and the accuracy of service life prediction is also correspondingly higher, which challenges the applicability of the commonly used mechanical property indicators in traditional service life prediction methods. For example, the dispersion of elongation at break and tensile strength at break is poor, making it difficult to obtain accurate variation rules, the change range of hardness is small, making it difficult to support long-term service life prediction, and compression set cannot be measured because the elasticity of the material is completely lost after aging. Therefore, it is necessary to select a more appropriate but still simple and feasible mechanical property indicator, especially one that is easy to couple with temperature, in order to develop a more accurate service life prediction method for O-shaped rubber sealing rings.

[0004] Compression stress relaxation refers to the phenomenon that the internal stress of a rubber material gradually decreases with time under the condition of constant compression strain, and the value is the ratio of the compression resilience of the material at a certain time to that at the initial time. Generally, the higher the temperature, the more obvious the compression stress relaxation effect, and the faster the ratio decreases. There are mainly two kinds of test methods for resilience. One is to place the compression mold containing the sample into a constant temperature heat aging box, and test the force value every certain time, such as 6, 12, 24, 48, 72 and 168 hours. The advantage is that the test is simple and low in cost, but the dispersion and regularity are usually poor, and it is difficult to be used for accurate life prediction. The other is to use a universal testing machine with a temperature chamber or a continuous compression stress relaxation testing machine to continuously test the resilience value of the sample. Although the structure and performance requirements of the equipment are high, especially the long-term reliability of the equipment, the data obtained by this method have good regularity, which is beneficial to improve the accuracy of life prediction under the condition of temperature coupling. Therefore, it is necessary to develop an O-shaped rubber sealing ring life prediction method coupled with temperature and continuous compression stress relaxation by using the above test device, so as to provide technical support for improving the accuracy of related product reliability evaluation, and can be applied to other rubber materials. SUMMARY

[0005] The technical problem to be solved by the present application is that the existing O-shaped rubber sealing ring life prediction method has poor accuracy in extreme environments, and the traditional mechanical properties such as elongation at break, tensile strength at break, hardness and compression set are easily affected by material dispersion and aging, and are difficult to be effectively coupled with temperature and actual service state, resulting in unreasonable and unreliable life prediction results. The present application provides an O-shaped rubber sealing ring life prediction method which can fully consider the coupling effect of temperature and continuous compression stress relaxation, and has higher prediction accuracy and engineering applicability.

[0006] A method for quickly, accurately and effectively predicting the service life of an O-shaped rubber sealing ring is provided.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] The method comprises:

[0009] A series of O-shaped rubber sealing ring samples to be tested are placed in a 70℃ oven for preheating for 3 hours as heat conditioning, and then placed at room temperature for 16 to 48 hours;

[0010] A universal testing machine or a continuous compression stress relaxation testing machine with a compression test clamp and a temperature chamber is used to perform long-time compression test on the O-shaped rubber sealing ring samples at different temperatures, so as to obtain the change of compression resilience value with time under different temperature conditions;

[0011] Based on the long-time compression test results, the exponential decay law suitable for the compression stress relaxation of rubber materials under different temperature conditions is adopted to establish the quantitative relationship among the compression stress relaxation, time and temperature, thereby obtaining the life prediction model;

[0012] The target service temperature of the O-shaped rubber sealing ring and the compression stress relaxation failure criterion are substituted into the life prediction model, and the calculated time is the predicted service life.

[0013] In one scheme, the long-time compression test is as follows: the O-shaped rubber sealing ring sample is clamped with a compression test clamp matched with a universal testing machine or a continuous compression stress relaxation testing machine, then the clamp and the sample are placed in a temperature box matched with the testing machine, so that the entire sample is subjected to compression test at a set temperature, thereby ensuring the temperature stability and consistency of the test environment, and accurately reflecting the stress and temperature conditions of the sealing ring in actual use.

[0014] In one scheme, the compression rate set by the testing machine is consistent with the compression rate of the O-shaped rubber sealing ring in actual use, so as to ensure that the test results are consistent with the actual service conditions and improve the accuracy of life prediction.

[0015] In one scheme, the temperature selected by the testing machine should be consistent with the aging mechanism of the O-shaped rubber sealing ring material at room temperature or actual service temperature, so as to ensure the applicability and scientificity of the life prediction model.

[0016] The duration of the long-time compression test is set according to actual needs, and is at least a multiple of 3 hours, preferably a multiple of 168 hours (1 week), and the specific test duration is determined according to the longest time that the testing machine can continuously and stably operate, so as to ensure that sufficient long-time data are obtained to support life prediction.

[0017] In one scheme, the life prediction model adopts the exponential decay law suitable for rubber materials, and the established model can quantitatively determine the relationship among compression stress relaxation, time and temperature, thereby providing a reliable basis for life prediction of O-shaped rubber sealing rings under different conditions.

[0018] In one scheme, the compression stress relaxation failure criterion is set according to actual engineering needs, the criterion is that the compression resilience of the sealing ring is reduced to half of the initial value or almost completely loses resilience, and the criterion is substituted into the life prediction model, so as to obtain life data more consistent with the application scenario.

[0019] In one scheme, after the target service temperature of the O-shaped rubber sealing ring and the compression stress relaxation failure criterion are substituted into the life prediction model, the service life of the O-shaped rubber sealing ring at the target service temperature is directly obtained by calculation.

[0020] In one approach, the process of establishing the lifetime prediction model is as follows:

[0021] (1) Under a certain fixed compression ratio and temperature condition, the compression rebound force of the O-ring rubber seal is divided by the initial compression rebound force to obtain the change of compression stress relaxation over time, where the initial compression rebound force refers to the maximum value of the compression rebound force within the test time range of 30±1 minutes.

[0022] (2) Repeat the above operation to obtain n sets of data on the change of compressive stress relaxation over time under n test temperatures at a certain fixed compression ratio;

[0023] (3) Exponential decay model of compressive stress relaxation in rubber materials under different temperature conditions A multinomial regression data processing method is used to fit the obtained n sets of data to establish a compressive stress relaxation mechanism. The quantitative relationship between time t, temperature T, and other factors;

[0024] (4) Introduce a physical information neural network for data fitting;

[0025] (5) The exponential model is mathematically transformed to obtain a lifetime prediction model with compressive stress relaxation and temperature as independent variables and time as the dependent variable. Beneficial effects of this invention:

[0026] 1. This method directly conducts a long-term compression stress relaxation test on O-ring rubber seals in a temperature chamber, avoiding the influence of ambient temperature changes on the accuracy of test results caused by the traditional compression stress relaxation test mode of "taking the sample out of the temperature chamber first and then conducting the test".

[0027] 2. This method performs long-term continuous testing of the compression rebound force of O-ring rubber seals, avoiding the influence of long time intervals on the accuracy of test results in traditional compression stress relaxation tests.

[0028] 3. This method establishes a mathematical model relating compressive stress relaxation, time, and temperature, which can directly predict the service life of O-ring rubber seals at the target service temperature. This method is more accurate than the traditional indirect method of "predicting the service life at a single temperature first, and then using the Arrhenius model to predict the service life at the target temperature". Attached Figure Description

[0029] Figure 1 This is a flowchart of the method of the present invention;

[0030] Figure 2 This is an embodiment of the present invention showing the change of compressive stress relaxation over time at 90°C and the fitted curve.

[0031] Figure 3This is an embodiment of the present invention showing the change of compressive stress relaxation over time at 100°C and the fitted curve.

[0032] Figure 4 This is an embodiment of the present invention showing the change of compressive stress relaxation over time at 110°C and the fitted curve.

[0033] Figure 5 This is an embodiment of the present invention showing the change of compressive stress relaxation over time at 120°C and the fitted curve.

[0034] Figure 6 This invention illustrates the relationship between compressive stress relaxation, time, and temperature, as well as surface fitting, in one embodiment of the invention. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0036] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. To facilitate understanding, the invention will now be described more fully with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the invention more thorough and complete.

[0037] like Figure 1 As shown, the method for predicting the life of O-ring rubber seals based on coupling temperature and continuous compressive stress relaxation proposed in this invention includes the following specific steps:

[0038] Step 1: Place a series of O-ring rubber seal samples to be tested into a 70°C oven for 3 hours as a heat conditioning process, and then place them at room temperature for 16 to 48 hours.

[0039] Step 2: Using a universal testing machine or a continuous compression stress relaxation testing machine equipped with compression test fixtures and a temperature chamber, conduct long-term compression tests on the O-ring rubber seal samples at different temperatures to obtain the changes in compression rebound force over time under different temperature conditions.

[0040] S201. Clamp the O-ring rubber seal sample with the compression test fixture of the universal testing machine or the continuous compression stress relaxation testing machine, and then place it together in the temperature chamber of the testing machine.

[0041] S202. In the control program of the testing machine, set the sample compression rate as required, such as 5%, 10%, etc., which is usually consistent with the compression rate of the O-ring rubber seal during actual use.

[0042] S203. In the control program of the testing machine, the temperature of the temperature chamber shall be set as required, such as 100℃, 120℃, etc., and it shall be ensured that the aging mechanism of the O-ring rubber seal material under the temperature condition is consistent with the room temperature or the actual service temperature.

[0043] S204. In the control program of the testing machine, the test duration should be set as required, and should be at least a multiple of 3 hours. If conditions permit, a multiple of 168 hours, i.e., 1 week, should be used. The specific duration should be determined based on the time during which the testing machine can run continuously and stably.

[0044] S205. In the control program of the testing machine, set the test frequency as required, such as 1 time / second, 1 time / minute, 1 time / hour, etc., depending on the testing capability of the testing machine, but ensure sufficient data for model fitting.

[0045] S206. After the test, the O-ring rubber seal samples were taken out from the temperature chamber and compression test fixture, and the changes in the compression rebound force value were recorded throughout the test.

[0046] S207. Set n test temperatures according to a certain temperature gradient, such as 5℃ and 10℃, and repeat the long-term compression test to obtain n sets of changes in the compression rebound force of the O-ring rubber seal over time under a certain fixed compression ratio.

[0047] Step 3: Based on the results of long-term compression tests, the exponential decay law of compression stress relaxation under different temperature conditions applicable to rubber materials is adopted to establish a quantitative relationship between the three parameters of compression stress relaxation, time, and temperature, thereby obtaining a life prediction model.

[0048] S301. Under a certain fixed compression ratio and temperature condition, the compression rebound force of the O-ring rubber seal is divided by the initial compression rebound force to obtain the change of compression stress relaxation over time, where the initial compression rebound force refers to the maximum value of the compression rebound force within the test time range of 30±1 minutes.

[0049] S302. Repeat the above operation to obtain n sets of data on the change of compressive stress relaxation over time under n test temperatures at a certain fixed compression ratio.

[0050] S303, an exponential decay model for compressive stress relaxation in rubber materials under different temperature conditions. Using data processing methods such as multinomial regression, the obtained n sets of data are fitted to establish a compressive stress relaxation mechanism. The quantitative relationship between time t, temperature T, and time t.

[0051] To further improve the model's accuracy and generalization ability in characterizing the compressive stress relaxation behavior of O-ring rubber seals, Physical-Informed Neural Networks (PINNs) were used to fit experimental data and model lifetime prediction. Unlike traditional PINNs, PINNs not only utilize existing experimental data on compression and rebound forces for supervised learning, but also directly embed the physical laws governing the compressive stress relaxation of rubber materials at different temperatures into the loss function of the neural network.

[0052] Specifically, the stress relaxation process is considered as a function R(t,T) that varies with time t and temperature T (where R is the normalized compressive resilience). Based on the empirical laws governing stress relaxation in rubber materials, it can typically be described by the following exponential differential equation:

[0053]

[0054] Where f(T) is the relaxation rate function that varies with temperature, which can be given by physical empirical formulas such as the Arrhenius equation.

[0055] Based on this, in the construction of PINNs, the first step is to use neural networks. As a compression relaxation prediction model, the inputs are time t and temperature T, and the output is the normalized compression rebound force. The loss function L consists of two parts:

[0056] First, experimental data loss. Used to fit the compression and rebound force data obtained from actual tests at different times and temperatures;

[0057] Second, physical constraint loss This is used to constrain the model output to satisfy the aforementioned differential physical laws. The final training objective is to minimize the total loss.

[0058] L=λ data L data +λ phys L phys

[0059] Where λ data With λ phys This is a weighting coefficient that can be adjusted based on the reliability of the data and physical constraints.

[0060] After network training, the model can not only accurately fit the measured temperature and time interval data, but also demonstrate good rationality and generalization performance in extrapolation prediction based on the embedded physical mechanism. Subsequently, an exponential model transformation can be performed on the compression rebound force time history output by the PINNs model to establish a life prediction model with compression stress relaxation and temperature as independent variables and time as the dependent variable, thereby achieving quantitative prediction of the life of O-ring rubber seals under actual service conditions.

[0061] S304. Perform a mathematical transformation on the exponential model to obtain a lifetime prediction model with compressive stress relaxation and temperature as independent variables and time as the dependent variable.

[0062] Step 4: Substitute the target operating temperature and the failure criterion of compressive stress relaxation of the O-ring into the life prediction model, and the calculated time is the predicted service life.

[0063] S401. Select the target service temperature according to actual engineering requirements, such as room temperature (i.e., 25℃), and substitute it into the life prediction model.

[0064] S402. Based on actual engineering requirements, set the failure criteria for compressive stress relaxation, such as reducing to half of the initial value (i.e., 50%), or complete loss (approximately 1%), and substitute it into the life prediction model.

[0065] S403. The time calculated based on the model is the service life of the O-ring rubber seal at the target service temperature.

[0066] Example 1:

[0067] Prediction of the service life of EPDM rubber O-rings in a large-scale advanced pressurized water reactor nuclear power plant

[0068] An O-ring made of EPDM rubber, with specifications of Φ15.47×3.53mm, is heat-conditioned according to step 1;

[0069] Following step 2, a long-term compression stress relaxation test was conducted using a continuous compression stress relaxation tester. The compression ratio was set to 25%, the test temperature was set to 90℃, 100℃, 110℃, and 120℃, the test duration was set to 5 weeks, and the test frequency was set to 1 time / hour.

[0070] Following step 3, plot the compressive stress relaxation versus time of the O-ring rubber seal under the above four temperature conditions, see... Figures 2 to 6 Furthermore, a quantitative relationship between three parameters—compressive stress relaxation, time, and temperature—was established through surface fitting, as shown in [reference needed]. Figure 6 The corresponding mathematical model is

[0071]

[0072] Following step 4, the long-term service upper limit temperature of 50°C and the value of 1% when the compressive stress relaxation is almost completely lost for EPDM rubber O-rings in nuclear power plants are substituted into the life prediction model. The predicted service life was 1628.44 days, or about 4.5 years, which is on the same order of magnitude as the product's replacement cycle or design service life, proving the reliability of the prediction results.

[0073] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0074] It should be understood that the above detailed description of the technical solutions of the present invention with reference to preferred embodiments is illustrative and not restrictive. Those skilled in the art can modify the technical solutions described in the embodiments or make equivalent substitutions for some of the technical features based on reading this specification; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting the life of an O-ring rubber seal by coupling temperature and continuous compressive stress relaxation, characterized in that: The method includes: A series of O-ring rubber seal samples to be tested were placed in a 70°C oven for 3 hours as a heat conditioning process, and then placed at room temperature for 16 to 48 hours. Using a universal testing machine or a continuous compression stress relaxation testing machine equipped with compression test fixtures and a temperature chamber, long-term compression tests were conducted on O-ring rubber seal samples at different temperatures to obtain the changes in compression rebound force over time under different temperature conditions. Based on the results of long-term compression tests, the exponential decay law of compression stress relaxation under different temperature conditions applicable to rubber materials is adopted to establish a quantitative relationship between three parameters: compression stress relaxation, time, and temperature, thereby obtaining a life prediction model. Substituting the target operating temperature and compressive stress relaxation failure criteria of the O-ring into the life prediction model, the calculated time is the predicted service life.

2. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: The long-term compression test is as follows: the O-ring rubber seal sample is clamped in the compression test fixture of a universal testing machine or a continuous compression stress relaxation testing machine, and then placed together with the fixture into the temperature chamber of the testing machine. The entire sample is subjected to compression test at the set temperature, thereby ensuring the temperature stability and consistency of the test environment and accurately reflecting the stress and temperature conditions of the seal in actual use.

3. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: The compression ratio set on the testing machine is consistent with the compression ratio of the O-ring rubber seal during actual use, so as to ensure that the test results are consistent with the actual service conditions and improve the accuracy of life prediction.

4. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation as described in claim 1, characterized in that: The aging mechanism of the O-ring rubber seal material at the temperature selected by the testing machine is consistent with that at room temperature or actual service temperature. The duration of the long-term compression test should be at least a multiple of 3 hours, preferably a multiple of 168 hours or 1 week. The specific test duration should be determined based on the longest continuous and stable operation time of the testing machine to ensure that data of a sufficient duration is obtained to support life prediction.

5. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: The life prediction model is applicable to the exponential decay law of rubber materials. The established model can quantify the quantitative relationship between compressive stress relaxation, time and temperature, providing a reliable basis for predicting the life of O-ring rubber seals under different working conditions.

6. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: Based on actual engineering needs, a failure criterion for compressive stress relaxation is set. The criterion is that the compression rebound force of the sealing ring drops to half of its initial value or almost completely loses its rebound force. This criterion is then substituted into the life prediction model to obtain life data that is more consistent with the application scenario.

7. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: After substituting the target service temperature of the O-ring rubber seal and the failure criterion for compressive stress relaxation into the life prediction model, the service life of the O-ring rubber seal at the target service temperature can be directly obtained through calculation.

8. The method for predicting the life of an O-ring rubber seal based on coupling temperature and continuous compressive stress relaxation according to claim 1, characterized in that: The process of establishing the lifetime prediction model is as follows: (1) Under a certain fixed compression ratio and temperature condition, the compression rebound force of the O-ring rubber seal is divided by the initial compression rebound force to obtain the change of compression stress relaxation over time, where the initial compression rebound force refers to the maximum value of the compression rebound force within the test time range of 30±1 minutes. (2) Repeat the above operation to obtain n sets of data on the change of compressive stress relaxation over time under n test temperatures at a certain fixed compression ratio; (3) Exponential decay model of compressive stress relaxation in rubber materials under different temperature conditions A multinomial regression data processing method is used to fit the obtained n sets of data to establish a compressive stress relaxation mechanism. The quantitative relationship between time t, temperature T, and other factors; (4) Introduce a physical information neural network for data fitting; (5) The exponential model is mathematically transformed to obtain a lifetime prediction model with compressive stress relaxation and temperature as independent variables and time as the dependent variable.

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