A method for evaluating the life of materials under high pressure

Abstract

The present application discloses a method for evaluating the life of a material under high pressure, which is characterized by comprising the following steps: at a temperature of T i and pressure P j Under the conditions of aging test, the sample is subjected to aging test; an aging cycle is formulated, samples are taken regularly, and the temperature T is measured. i and pressure P j The compression permanent deformation value of the sample under the condition of x ; The compression permanent deformation value of the sample ε x The end point of the life of the sample material is 50%, and the temperature T is calculated. i and pressure P j The life of the sample under the condition t k ; The temperature T i and the pressure P j and (T i , P j ) corresponds to the life span t k Substitute into the relationship: #imgabs0# to calculate the estimated coefficients C and E; use the relationship #imgabs1# to predict the material life under a certain temperature and pressure. The life evaluation method provided in this application can evaluate the life of a material under high pressure, and has the characteristics of simple operation and reliable results.

Description

Technical Field

[0001] The invention belongs to the technical field of material aging detection, and in particular relates to a method for evaluating the life of a material under a high-pressure state. Background Art

[0002] Seals are widely used in industry, and the direct consequence of seal failure is the leakage of sealed fluid.

[0003] Rubber sealing materials are affected by heat, oxygen, mechanical stress and contact with oil, water and other media in a long-term use environment, and they will change color, become sticky, become hard and brittle, and their physical and mechanical properties will decrease, thus losing their use value. In daily life and production, it is very important to evaluate the service life of materials.

[0004] The existing method GB / T 20028-2005 "Estimation of service life and maximum operating temperature of vulcanized rubber or thermoplastic rubber using Arrhenius diagram" stipulates the life assessment method of rubber materials under temperature stress. The use environment of rubber sealing materials is complex. In addition to the influence of temperature on their service life, the influence of pressure on their service life cannot be ignored. However, when evaluating the service life of materials under environmental pressure factors, there is a lack of necessary test methods. Summary of the invention

[0005] The present application provides a method for evaluating the life of a material under high pressure, so as to solve the technical problem that the life of a material cannot be evaluated under high pressure.

[0006] A method for evaluating the life of a material under high pressure provided by the present invention comprises the following steps:

[0007] At temperature T i and pressure P j Under the conditions of , the aging test is carried out on the samples;

[0008] Establish an aging cycle, take samples regularly, and measure the temperature T i and pressure P j The compression permanent deformation value of the sample under the condition ε x ;

[0009] The compression set value of the sample is ε x The end point of the life of the sample material is 50%, and the temperature T is calculated. i and pressure P j The life of the sample under the condition t k ;

[0010] The temperature T i and the pressure P j and (T i , P j ) corresponds to the life span tk Substitute into the relation: Calculate the estimated coefficients C and E;

[0011] Using the relationship Predict the lifetime of materials at a certain temperature and pressure;

[0012] Wherein, t is the aging time, unit d, T is the thermodynamic temperature, unit K, P is the ambient pressure, unit MPa, Ea is the apparent activation energy, unit J / mol, R is the molar gas constant, valued at 8.314 J / (mol·K), C and E are coefficients to be estimated;

[0013] Among them, the values ​​of i and j are 1, 2, 3, ..., N, N is the number of test points, the value of x is 1, 2, 3, ..., X, and the value of k is 1, 2, 3, ..., K.

[0014] An optional implementation manner is to calculate the coefficients C and E to be estimated, specifically, to calculate the coefficients C and E to be estimated by using a binary linear regression method.

[0015] An optional implementation manner is to predict the material life at a certain temperature and pressure, specifically, to predict the material life at a certain temperature and pressure using an extrapolation method.

[0016] In an optional embodiment, the temperature T is measured. i and pressure P j The compression permanent deformation value of the sample under the condition ε x Specifically, according to the national standard GB / T 7759.1-2015, the temperature T is measured i and pressure P j The compression permanent deformation value of the sample under the condition ε x .

[0017] An optional implementation method is to calculate the temperature T i and pressure P j The life of the sample under the condition t k , specifically, according to the measured compression set value ε x and the corresponding sampling time, and the compression set value ε is obtained by the insertion method x The aging time when the critical value reaches 50% is the temperature T i and pressure P j The life of the sample under the condition t k .

[0018] Based on the above embodiments, it can be seen that the present invention provides a method for evaluating the life of a material under high pressure, comprising the following steps: at a temperature of T i and pressure P jUnder the conditions of aging test, the sample is subjected to aging test; an aging cycle is established, samples are taken regularly, and the temperature T is measured. i and pressure P j The compression permanent deformation value of the sample under the condition ε x ; The compression permanent deformation value of the sample ε x The end point of the life of the sample material is 50%, and the temperature T is calculated. i and pressure P j The life of the sample under the condition t k ; The temperature T i and the pressure P j and (T i , P j ) corresponds to the life span t k Substitute into the relation: Calculate the estimated coefficients C and E; use the relationship Predict the material life under certain temperature and pressure; where t is the aging time, unit d, T is the thermodynamic temperature, unit K, P is the ambient pressure, unit MPa, Ea is the apparent activation energy, unit J / mol, R is the molar gas constant, valued at 8.314J / (mol·K), C and E are coefficients to be estimated; where i and j are 1, 2, 3, ..., N, N is the number of test points, x is 1, 2, 3, ..., X, and k is 1, 2, 3, ..., K. By correcting the reaction rate constant, the life evaluation experiment under high pressure can be achieved through limited experiments.

[0019] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A schematic flow chart of a method for evaluating the life of a material under high pressure provided by an embodiment of the present invention;

[0022] Figure 2 A data graph showing changes in aging coefficient versus aging time at different temperatures under standard atmospheric pressure provided by an embodiment of the present invention;

[0023] Figure 3 A data graph showing the variation of the aging coefficient with the aging time at different temperatures under high pressure (2MPa) provided by an embodiment of the present invention;

[0024] Figure 4 Another data graph of the variation of the aging coefficient with the aging time at different temperatures under high pressure (3MPa) provided by an embodiment of the present invention;

[0025] Figure 5 A relationship fitting diagram of P, 1\T and ln(t) provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Figure 1 A schematic flow chart of a method for evaluating the life of a material under high pressure provided by an embodiment of the present invention; Figure 2 A data graph showing changes in aging coefficient versus aging time at different temperatures under standard atmospheric pressure provided by an embodiment of the present invention; Figure 3 A fitting relationship diagram of P, 1\T and ln(t) provided in an embodiment of the present invention; Figure 4 Another data graph of the variation of the aging coefficient with the aging time at different temperatures under high pressure (3MPa) provided by an embodiment of the present invention; Figure 5 A relationship fitting diagram of P, 1\T and ln(t) provided in an embodiment of the present invention. Figure 1 to Figure 5 The life evaluation method of the material under high pressure provided in the embodiment of the present invention is described in detail.

[0028] First, a unified description of each embodiment is given:

[0029] K T : Temperature effect of reaction rate constant

[0030] E a : Apparent activation energy, (J / mol)

[0031] R: molar gas constant, [8.314 J / (mol·K)]

[0032] T: Thermodynamic temperature of aging, (K)

[0033] P: Environmental pressure during the test, (MPa)

[0034] F(t): performance index at aging time t

[0035] t: aging time, (d)

[0036] K: Apparent reaction rate constant

[0037] K P : Pressure effect component of reaction rate constant

[0038] A, B, C, D, E: coefficients to be estimated

[0039] 1-ε: Aging coefficient, 1 minus the compression set value

[0040] like Figure 1 As shown, the life assessment method of a material under high pressure includes the following steps:

[0041] S1: At temperature T i and pressure P j Under the conditions of aging test, the samples were subjected to aging test.

[0042] At temperature T i and pressure P j Under the condition of , the aging test is carried out on the sample, and the values ​​of i and j are 1, 2, 3, ..., N, where N is the number of test points. In specific implementation, it can be divided into adjusting the temperature under standard atmospheric pressure conditions for testing, or adjusting the temperature under high pressure conditions for testing. This is convenient for operation and can obtain reliable results.

[0043] S2: Establish an aging cycle, take samples regularly, and measure the temperature T i and pressure P j The compression permanent deformation value of the sample under the condition ε x .

[0044] The specific sampling period is adjusted according to the aging characteristics of the material. The sampling frequency is high in the initial stage, and the sampling frequency is appropriately reduced after the performance decreases and stabilizes in the later stage. After sampling, the temperature T is measured according to the national standard GB / T 7759.1-2015 i and pressure P j The compression permanent deformation value of the sample under the condition ε x , the values ​​of x are 1, 2, 3, …, X.

[0045] S3: The compression set value ε of the sample x The end point of the life of the sample material is 50%, and the temperature T is calculated. i and pressure P j The life of the sample under the condition t k .

[0046] Because the sampling time is intermittent, the compression set value ε of the sample x The sample is not necessarily taken at the right time for 50%, but is usually measured based on the compression permanent deformation value ε of the sample.x When the compression deformation is greater than 50%, it is regarded as the end of the life of the sample material. In this way, it is necessary to calculate the compression permanent deformation value ε of the sample. x The life of the sample when it is equal to 50%. Therefore, calculate the temperature T i and pressure P j The life of the sample under the condition t k , specifically, according to the measured compression set value ε x and the corresponding sampling time, and the compression set value ε is obtained by the insertion method x The aging time when the critical value reaches 50% is the temperature T i and pressure P j The life of the sample under the condition t k , the value of k is 1, 2, 3, …, K.

[0047] S4: Set the temperature T i and the pressure P j and (T i , P j ) corresponds to the life span t k Substitute into the relation: Calculate the estimated coefficients C and E.

[0048] The reaction rate affected by temperature satisfies the Arrhenius equation

[0049] The reaction rate of high pressure environment to material aging is described by exponential model K P =B·e CP .

[0050] In the aging process, it is believed that each stress affects the performance of the material independently. The aging of the material is the superposition of the performance degradation caused by each stress alone. The total reaction rate constant

[0051] During the aging process, the relationship between the aging performance index F(t), the aging time t, and the reaction rate constant K(T) can be expressed by the following equation: F(t)=K·t.

[0052] Taking the natural logarithm of both sides gives the relationship:

[0053] After determining the critical value of the aging performance index, ln F(t) is a constant, and E = ln F(t)-lnD can be used to obtain the relationship between the aging performance degradation time, environmental pressure and thermodynamic temperature:

[0054] The temperature T is obtained through the above steps. i and pressure P jThe life of the sample under the condition t k , T i , P j ,t k Substitute into the relation: The estimated coefficients C and E were calculated using the binary linear regression method.

[0055] S5: Using the relationship Predict the lifetime of materials at certain temperature and pressure.

[0056] Through step S4, the relationship between P, 1\T and ln(t) is obtained, a certain ambient temperature and a certain ambient pressure are introduced into the relationship between P, 1\T and ln(t), and then the material life under a certain temperature and pressure is predicted using the extrapolation method.

[0057] Implementation Cases

[0058] Test sample: EPDM rubber.

[0059] Diagnostic parameter: Compression set.

[0060] Test conditions: 170°C (standard atmospheric pressure), 180°C (standard atmospheric pressure), 190°C (standard atmospheric pressure), 200°C (standard atmospheric pressure), 210°C (standard atmospheric pressure), 170°C (2MPa), 180°C (2MPa), 190°C (2MPa), 200°C (2MPa), 210°C (2MPa), 170°C (3MPa), 180°C (3MPa), 190°C (3MPa), 200°C (3MPa), 210°C (3MPa).

[0061] The test under standard atmospheric pressure is carried out in accordance with GB / T20028-2005. The test under standard atmospheric pressure is carried out in a hot air aging chamber, and the compression permanent deformation is carried out in accordance with GB / T 7759.1-2015. An aging cycle is established, and samples are taken out regularly for compression permanent deformation tests according to national standards. The data obtained are shown in Table 1 and Figure 2 .

[0062] Table 1 Compression permanent deformation values ​​of samples under standard atmospheric pressure

[0063] Time (d) 170℃ 180℃ 190℃ 200℃ 210℃ 1 / / / / 0.67 2 0.90 0.85 0.73 0.69 0.59 3 / / / / 0.54 4 0.85 0.80 0.67 0.61 0.52 5 / / / 0.56 0.50 5.5 / / / / 0.45 6 0.82 0.73 0.61 0.53 0.39 7 / / / 0.5 / 8 / / 0.57 0.47 / 9 / / / 0.46 / 11 / 0.62 0.54 0.43 / 13 / / 0.52 / / 14 0.72 0.58 / / 15 / / 0.50 / / 16 / / 0.48 / / 17 / 0.56 0.45 / / 20 0.66 0.54 / / / 22 / 0.53 / / / 26 / 0.50 / / / 27 0.63 / / / / 28 / 0.48 / / / 29 / 0.47 / / / 31 0.57 0.44 / / / 35 0.54 / / / / 40 0.50 / / / / 47 0.47 / / / / 54 0.44 / / / /

[0064] The insertion method yields the aging time when the compression permanent deformation reaches 50% of the critical value at aging temperatures of 170°C, 180°C, 190°C, 200°C and 210°C under standard atmospheric pressure, respectively, as shown in Table 2.

[0065] Table 2 Aging time at different temperatures under standard atmospheric pressure

[0066] temperature 170℃ 180℃ 190℃ 200℃ 210℃ Aging time / d 42.1 24.3 13.9 7.2 4.2

[0067] The test under high pressure uses a reactor to carry out aging tests, and nitrogen is filled to simulate the use environment pressure. When the reactor pressure is 2MPa, samples are taken out regularly according to the aging cycle to carry out compression permanent deformation tests according to national standards. The data obtained are shown in Table 3 and Figure 3 .

[0068] Table 3 Compression permanent deformation values ​​of samples under high pressure (2MPa) conditions

[0069] Time (h) 170℃ 180℃ 190℃ 200℃ 210℃ 1 0.98 0.95 0.92 0.91 0.86 3 0.96 0.91 0.86 0.82 0.76 5 0.93 0.88 0.81 0.74 0.63 7 0.91 0.86 0.77 0.68 0.52 9 0.88 0.83 0.72 0.62 0.46 12 0.86 0.78 0.67 0.54 0.38 16 0.84 0.73 0.63 0.45 / 20 0.80 0.69 0.58 0.39 / 24 0.76 0.63 0.52 / / 36 0.70 0.56 0.42 / / 48 0.65 0.47 0.34 / / 60 0.61 0.39 / / / 72 0.52 / / / / 96 0.42 / / / / 120 0.37 / / / /

[0070] The insertion method obtained the aging time when the compression permanent deformation reached 50% of the critical value at aging temperatures of 170°C, 180°C, 190°C, 200°C and 210°C under high pressure conditions (2MPa), as shown in Table 4. The aging time to reach the critical value under high pressure conditions was obtained.

[0071] Table 4 Aging time at different temperatures under high pressure (2MPa) conditions

[0072] temperature 170℃ 180℃ 190℃ 200℃ 210℃ Aging time / h 78.9 42.5 26.5 13.8 8.0

[0073] When the reactor pressure is 3 MPa, samples are taken out regularly according to the aging cycle to conduct compression set tests according to national standards. The data obtained are shown in Table 5 and Figure 4 .

[0074] Table 5 Compression permanent deformation values ​​of samples under high pressure (3MPa) conditions

[0075]

[0076]

[0077] By the insertion method, the aging time when the compression permanent deformation reaches 50% of the critical value at aging temperatures of 170°C, 180°C, 190°C, 200°C and 210°C under high pressure conditions (3MPa) is obtained, as shown in Table 6. The aging time to reach the critical value under high pressure conditions is obtained.

[0078] Table 6 Aging time at different temperatures under high pressure (3MPa) conditions

[0079] temperature 170℃ 180℃ 190℃ 200℃ 210℃ Aging time / h 18.7 11.5 6.1 3.4 1.9

[0080] like Figure 5As shown, the test data of thermodynamic temperature, environmental pressure and aging time are fitted by binary linear regression to obtain the estimated coefficients C and E, which are 1.365 and -23.98 respectively. The life evaluation relationship is lnt = 1.2362 × 104 × 1T-1.362·P-23.98.

[0081] Substituting the operating temperature of 70°C and the operating ambient pressure of 2MPa into the equation, the service life is obtained as follows: In line with actual conditions.

[0082] The above embodiments describe the present invention in detail. These descriptions are illustrative rather than restrictive. Several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

[0083] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the disclosure of the invention herein. The present application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the content of the claims.

[0084] The above implementation modes of the present application do not constitute a limitation on the protection scope of the present application.

Claims

1. A method for evaluating the life of a material under high pressure, characterized in that: The following steps are involved: At temperature T i and pressure P j Under the conditions of aging test, the samples are subjected to aging test; Establish an aging cycle, take samples regularly, and measure the temperature T i and pressure P j The compression permanent deformation value of the sample under the condition of x ; The compression set value of the sample is ε x The end point of the life of the sample material is 50%, and the temperature T is calculated. i and pressure P j The life of the sample under the condition t k ; The temperature T i and the pressure P j and (T i , P j ) corresponds to the life span t k Bring it into the relation Calculate the estimated coefficients C and E; Using the relationship Predict the lifetime of materials at a certain temperature and pressure; Wherein, t is the aging time, unit d, T is the thermodynamic temperature, unit K, P is the ambient pressure, unit MPa, Ea is the apparent activation energy, unit J / mol, R is the molar gas constant, valued at 8.314 J / (mol·K), C and E are coefficients to be estimated; Among them, the values ​​of i and j are 1, 2, 3, ..., N, N is the number of test points, the value of x is 1, 2, 3, ..., X, and the value of k is 1, 2, 3, ..., K.

2. The method for evaluating the life of a material under high pressure according to claim 1, characterized in that: The estimated coefficients C and E are calculated. Specifically, the estimated coefficients C and E are calculated using a binary linear regression method.

3. The method for evaluating the life of a material under high pressure according to claim 1, characterized in that: Predicting the material life at a certain temperature and pressure, specifically, using an extrapolation method to predict the material life at a certain temperature and pressure.

4. The method for evaluating the life of a material under high pressure according to claim 1, characterized in that: Measure temperature T i and pressure P j The compression permanent deformation value of the sample under the condition of x Specifically, according to the national standard GB / T 7759.1-2015, the temperature T is measured i and pressure P j The compression permanent deformation value of the sample under the condition of x .

5. The method for evaluating the life of a material under high pressure according to claim 1, characterized in that: Calculate temperature T i and pressure P j The life of the sample under the condition t k , specifically, according to the measured compression set value ε x and the corresponding sampling time, and the compression set value ε is obtained by the insertion method x The aging time when the critical value reaches 50% is the temperature T i and pressure P j The life of the sample under the condition t k .

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