WO2019169833A1 - 管材剩余使用寿命的测试方法和测试系统 - Google Patents

管材剩余使用寿命的测试方法和测试系统 Download PDF

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Publication number
WO2019169833A1
WO2019169833A1 PCT/CN2018/101826 CN2018101826W WO2019169833A1 WO 2019169833 A1 WO2019169833 A1 WO 2019169833A1 CN 2018101826 W CN2018101826 W CN 2018101826W WO 2019169833 A1 WO2019169833 A1 WO 2019169833A1
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test
strain hardening
modulus value
service life
sample
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PCT/CN2018/101826
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English (en)
French (fr)
Inventor
杨波
王志刚
李茂东
翟伟
李仕平
黄国家
张双红
笪箐
丁金森
涂欣
伍振凌
何颖怡
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广州特种承压设备检测研究院
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Publication of WO2019169833A1 publication Critical patent/WO2019169833A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light

Definitions

  • the present application relates to material testing techniques, and more particularly to a test method and test system for the remaining service life of a pipe.
  • Polyethylene (PE) gas pipelines have gradually replaced steel pipes due to their strong corrosion resistance, good mechanical properties, long service life and environmental protection. As a common means of natural gas transportation, they are widely used in urban gas pipeline networks.
  • the in-service polyethylene gas pipe is mainly made of the third generation PE100 grade pipe. Its design life is 58 years, and it has been put into use for about 20 years. Since the gas pipe is buried underground all the year round, it is continuously subjected to soil pressure and hot oxygen. A variety of external factors such as aging, point load and corrosion, with the increase of service time, the pipe itself is easy to form local stress concentration, and finally the pipe is prone to slow crack failure, which directly affects the remaining service life of the in-service PE gas pipe.
  • In-service PE gas pipes are pressure-bearing special equipments, all of which are inflammable and explosive. Once gas leakage occurs, the consequences will be fatal; therefore, the remaining service life of PE gas pipes in service can reach the pre-design life, directly It affects the normal operation of the city gas pipeline network and the safety of people's lives and property, and is an important technical indicator.
  • there is a lack of rapid and effective evaluation method for the remaining service life of PE gas pipes in service Many cities' gas pipeline networks cannot replace the failed pipes in time and effectively due to the lack of accurate and effective effective prediction methods for remaining service life. Gas leakage accidents and quality safety accidents have occurred, and even caused explosions, causing serious hidden dangers to urban public safety.
  • the remaining service life prediction acceleration evaluation method can provide a strong safety guarantee for the quality and cost control of PE gas pipe, shorten the development cycle of the new gas pipe special resin, and ensure the safe operation of the existing gas pipeline system.
  • the object of the present application is to address at least one of the above technical drawbacks, in particular for the problem that the remaining service life of the piping system is difficult to estimate.
  • the present application provides a test method for the remaining service life of a pipe, comprising: obtaining a strain hardening modulus value ⁇ G p > corresponding to each of at least three polyethylene materials of a known design service life T; according to the strain hardening modulus Value ⁇ G p > with the design lifetime T, build function:
  • T a 0 + a 1 ⁇ ⁇ G p > + a 2 ⁇ ⁇ G p > 2 + ... + a n ⁇ ⁇ G p > n , where a 0 , a 1 , a 2 ...
  • a n is a preset coefficient, n is a preset maximum number of the functions, taking a positive integer; obtaining a test sample from an in-service polyethylene pipe; measuring a strain hardening modulus value ⁇ G P ' of the test sample Substituting the strain hardening modulus value ⁇ G P ' of the test sample into the function to replace the strain hardening modulus value ⁇ G P >, and calculating the service life, the service life being the remainder of the test sample Service life.
  • the method further comprises: determining whether to replace the in-service polyethylene pipe according to the remaining service life.
  • the determining whether to replace the in-service polyethylene pipe comprises: replacing the in-service polyethylene pipe when the remaining service life is not greater than a first preset value; and when the remaining service life is greater than the first The predetermined value is less than the second preset value, and the in-service polyethylene pipe is periodically detected.
  • the obtaining a strain hardening modulus value ⁇ G P > of at least three polyethylene materials having a known design service life T comprises: preparing a standard sample of the at least three polyethylene materials, each polyethylene At least five standard samples are prepared from the material; the strain hardening modulus value ⁇ G Pi > of each of the standard samples is obtained by a high temperature tensile test, where i is the number of the standard sample; The strain hardening modulus value ⁇ G Pi > of the sheet standard sample, the root mean square average value of the strain hardening modulus value of each polyethylene material is calculated, and the root mean square average value is used as the strain hardening modulus value ⁇ G P >.
  • the standard sample of the at least three polyethylene materials is prepared, and at least five standard samples are prepared for each polyethylene material, including: preparing the at least each of the polyethylene materials in a compression molding apparatus Five standard samples, the standard sample is a dumbbell-shaped sheet comprising a middle test portion and a clamping portion at both ends, the dumbbell-shaped sheet having a thickness of 0.3 mm to 1 mm; and the at least five standard samples are placed After annealing at 115 ° C - 125 ° C for one hour, the sample was cooled to room temperature at a cooling rate of less than 2 ° C / min.
  • the strain hardening modulus value ⁇ G Pi > of each of the standard samples is obtained by a high temperature tensile test, comprising: placing the dumbbell-shaped sheet in an incubator at 80 ° C for 30 min - 60 min The two end clamping portions were clamped on a high-temperature tensile tester, and a pre-stress of 0.4 MPa was applied at a strain rate of 5 mm/min; the dumbbell-shaped sheet was stretched at a constant moving speed of 20 mm/min, and the collection center a data value of a stretching ratio ⁇ between 8 and 12 in the middle test portion, the stretching ratio
  • L 0 is the initial length of the middle test portion
  • the L is the length after stretching of the middle test portion
  • the correspondence between the stretch ratio ⁇ and the true stress ⁇ true during the stretching is recorded:
  • F is the tensile force corresponding to the data value of the draw ratio
  • a 0 is the initial cross-sectional area of the middle portion of the dumbbell-shaped sheet
  • the obtaining a test sample from the in-service polyethylene pipe comprises: obtaining a test material from the in-service polyethylene pipe, and processing the test material into the test sample in a sample preparation machine;
  • the test sample is a dumbbell-shaped sheet including a middle test portion and a clamping portion at both ends, and the dumbbell-shaped sheet has a thickness of 0.3 mm to 1 mm.
  • the measuring the strain hardening modulus value G P ' of the test sample comprises: placing the test sample in an incubator at 80 ° C for 30 min - 60 min; The end clamping portion was clamped on a high temperature tensile tester, and a pre-stress of 0.4 MPa was applied at a strain rate of 5 mm/min; the test specimen was stretched at a constant moving speed of 20 mm/min, and the middle of the test specimen was collected.
  • the strain hardening modulus value ⁇ G P '> includes: determining a strain hardening modulus value ⁇ G Pi '> of each test piece of the test piece; calculating a mean square of the strain hardening modulus value ⁇ G Pi '> The root mean value is taken as the strain hardening modulus value ⁇ G P '> of the test sample.
  • the present application also provides a test system for the remaining service life of a pipe, comprising: a sample preparation device for obtaining a test sample from an in-service polyethylene pipe; and a tensile test device for measuring strain hardening of the test sample Modulus value ⁇ G P '>; central processor: strain hardening modulus value ⁇ G P > of at least three polyethylene materials for obtaining a known design service life T, the at least three polyethylene materials being different Model of polyethylene material; according to the strain hardening modulus value ⁇ G P > and the design service life T, the construction function:
  • T a 0 + a 1 ⁇ ⁇ G p > + a 2 ⁇ ⁇ G p > 2 + ... + a n ⁇ ⁇ G p > n , where a 0 , a 1 , a 2 ... a n is a preset coefficient, n is a preset maximum number of times of the function, and takes a positive integer; substituting the strain hardening modulus value ⁇ G P '> of the test sample into the function to replace the strain hardening modulus value ⁇ G P >, the service life is calculated, and the service life is the remaining service life of the test specimen.
  • This application first analyzes the polyethylene material with a known design life T to construct a strain hardening modulus value ⁇ G P > as a function of the design service life T; and then obtain the test from the in-service polyethylene pipe. a sample, measuring a strain hardening modulus value ⁇ G P '> of the in-service polyethylene pipe, and finally substituting the function to replace the strain hardening modulus value ⁇ G P >, obtaining a service life, that is, the test sample The remaining life.
  • the remaining service life of the test specimen as the reference value of the remaining service life of the in-service polyethylene pipe due to slow crack propagation, the risk of failure of the in-service polyethylene pipe due to slow crack propagation can be found in time.
  • the present application can effectively evaluate the remaining service life of different in-service polyethylene pipes to take different treatment measures for the in-service polyethylene pipe according to the remaining service life.
  • the present application can correct the strain hardening modulus values of the polyethylene materials known in the prior art by measuring the strain hardening modulus values of a plurality of the standard samples and taking the root mean square average value;
  • the production parameters and measurement parameters of the standard sample are used as the measurement parameters of the subsequent test sample, and the calculation result of the remaining service life can be further improved; the application is particularly suitable for the analysis of the remaining service life of the gas pipeline.
  • FIG. 1 is a schematic flow chart of a first embodiment of a testing method according to the present application.
  • FIG. 2 is a schematic structural view of an embodiment of a tensile testing device according to the present application.
  • FIG. 3 is a schematic structural view of still another embodiment of the tensile testing device of the present application.
  • FIG. 4 is a schematic structural view of another embodiment of the tensile testing device of the present application.
  • the present application provides a first embodiment of a test method for remaining service life of a pipe, comprising the following steps:
  • Step S10 obtaining a strain hardening modulus value ⁇ G P > corresponding to each of at least three kinds of polyethylene materials having a known design service life T;
  • Performance parameters of various materials have been disclosed in the prior art, such as elastic modulus, Poisson's ratio, density, coefficient of thermal expansion, yield strength, tensile strength, elongation, strain hardening modulus, and the like of the material.
  • the strain hardening modulus value in the performance parameter is related to the slow crack propagation height of the material, so the slow speed of the material can be estimated by the strain hardening modulus value of the test material. The remaining service life of crack propagation and failure.
  • the strain hardening modulus value ⁇ G P > of a different type of polyethylene material of known design life T is subjected to correlation analysis to obtain the strain hardening modulus value ⁇ G P > and the design service life T
  • Different types of polyethylene materials include pipes made of different grades of polyethylene materials named by various polyethylene manufacturers, for example, pipes made of 100 grade high density polyethylene, designed for a service life of 58 years, or The pipe made of crack-resistant polyethylene PE100-RC has a design service life of 100 years.
  • the design service life T corresponding to the strain hardening modulus value ⁇ G P > may be a value of each manufacturer's trademark, or may be tested by itself to obtain a more accurate design life T value.
  • Step S20 construct a function according to the strain hardening modulus value ⁇ G P > and the design service life T:
  • T a 0 + a 1 ⁇ ⁇ G p > + a 2 ⁇ ⁇ G p > 2 + ... + a n ⁇ ⁇ G p > n , where a 0 , a 1 , a 2 ... a n is a preset coefficient, n is the preset maximum number of times of the function, and takes a positive integer;
  • the design life T and the strain hardening modulus value ⁇ G P > of at least three different types of polyethylene materials can be solved by Newton iterative method and the like, and the preset coefficients are obtained.
  • the value is obtained as a function of the strain hardening modulus value ⁇ G P > and the design service life T.
  • the strain hardening modulus value ⁇ G P > and the design service life T of the same type of polyethylene material are taken as an array.
  • a straight line equation with an error function of zero can be obtained, but the error is large;
  • the present application may take more of the array to obtain a fitting equation of n times, and improve the accuracy of constructing the function.
  • the number of the arrays may exceed the positive integer n, and then the function of minimizing the error is fitted by Newton iteration method, so that the function error of the fitting is further reduced; a part of the values in the array may be located in the fitting On the function curve, another part is evenly distributed on both sides of the function curve. The more the number of arrays, the lower the error rate of the constructed function.
  • Step S30 obtaining a test sample from the in-service polyethylene pipe
  • the in-service polyethylene pipe is a pipe in use, such as a gas pipe buried in the ground. After fitting the strain hardening modulus value ⁇ G P > as a function of the design service life T in step S20, it is only necessary to obtain the strain hardening modulus value of the in-service polyethylene pipe to obtain the in-service aggregation. The remaining life of the ethylene pipe.
  • the step of obtaining a test sample from an in-service polyethylene pipe may include the step of directly taking a portion of the pipe sample from the in-service polyethylene pipe and processing the sample into a suitable test sample shape.
  • Step S40 measuring a strain hardening modulus value ⁇ G P '> of the test sample
  • the strain hardening modulus value ⁇ G P ' of the test sample is measured by using an existing tensile test equipment, and a suitable tensile test may be designed or assembled according to the specific conditions of the test sample. device. Measuring the strain hardening modulus value ⁇ G P ' of the test sample> the selected parameter is preferably a strain hardening modulus value corresponding to each of at least three polyethylene materials measuring the known design service life T ⁇ G P > The selected parameters are consistent; the parameters include the size of the test sample, the heating temperature and time of the test sample, the tensile force and the stretching time during the stretching process.
  • Step S50 Calculate the remaining service life of the test sample according to the function and the strain hardening modulus value ⁇ G P ' of the test sample.
  • the service life of the test sample is obtained, and the calculated service life at this time is the remaining service life of the test sample. Since the material of the test sample is taken from the in-service polyethylene pipe, the material has changed in the use environment, and the change is the same as the in-service polyethylene pipe still in use, so the remainder of the test sample can be passed.
  • the service life estimates the remaining service life of the in-service polyethylene pipe.
  • the remaining service life of the in-service polyethylene pipe may be the same as the remaining service life of the test sample, and there may be a certain proportional relationship.
  • Existing polyethylene pipes may cause defects in production, transportation and construction, and in subsequent use, they may be affected by external factors such as temperature, pressure and point load, and may have creep, stress relaxation, and rapid crack propagation.
  • Various failure modes such as slow crack propagation and material aging; among them, slow crack propagation is the most important failure mode.
  • the existing polyethylene pipe has been estimated in design life, the actual service life of the pipe does not necessarily match the design service life due to factors such as actual use parameters and different use environments.
  • slow crack propagation is the most important failure mode of the pipe, and the remaining service life of the slow crack propagation is highly correlated with the strain hardening modulus value. Therefore, the strain hardening modulus can be constructed by analysis first.
  • the value is a function of the design service life, and the test sample is taken from the in-service polyethylene pipe to calculate the remaining service life of the test sample according to the strain hardening modulus value ⁇ G P ' of the test sample. According to the remaining service life of the test sample, the remaining service life of the in-service polyethylene pipe corresponding to failure due to slow crack propagation may be estimated.
  • this application can timely discover the risk of failure of the in-service polyethylene pipe due to slow crack propagation, and avoid the danger caused by the failure of the in-service pipeline before the design service life, such as the gas leakage caused by the slow crack propagation of the polyethylene gas pipeline. Accidents, etc.; through this application, the remaining service life of different polyethylene pipes in service can be effectively evaluated to differently treat the in-service polyethylene pipes according to the remaining service life.
  • the present application provides another embodiment: after calculating the remaining service life of the test sample, the method further includes:
  • the test sample is taken from the in-service polyethylene pipe
  • the test sample may be subsequently processed into a shape suitable for testing, and the remaining service life of the test sample is actually in service.
  • the in-service polyethylene pipe Refer to the specific environment of the in-service polyethylene pipe, the safety factor, the processing technology of the test sample, etc., and judge whether it needs to be replaced according to the remaining service life.
  • the in-service polyethylene pipe due to the harsh environment, the service life of the service pipe is 20 years away from the original design, but the remaining service life calculated by the test method of the present application is only 3 years, and the in-service polyethylene pipe involves environmental pollution.
  • the user can comprehensively judge whether it is necessary to replace the in-service polyethylene pipe immediately according to the various factors, or replace the in-service polyethylene pipe at the latest, or replace the in-service polyethylene pipe with Other materials.
  • the present application proposes another embodiment: the determining whether to replace the in-service polyethylene pipe includes:
  • the in-service polyethylene pipe is periodically detected.
  • corresponding measures may be taken according to the value of the remaining service life, such as immediately replacing the in-service polyethylene pipe, or periodically testing the in-service polyethylene pipe to provide a reference for user decision-making.
  • Different parameters can also be set according to the conditions of use of the in-service polyethylene pipe. For example, for the water supply pipeline, if the remaining service life is more than 5 years, continue to use normally; if the remaining service life is more than 2 years less than 5 years, it is regularly tested once a year to monitor the use of the in-service polyethylene pipe. In case, the water pipe is prevented from bursting; for the gas pipeline, if the remaining service life is less than 5 years and less than 8 years, it is regularly tested once a year to monitor the in-service polyethylene pipe to prevent gas leakage.
  • the present application also proposes a second embodiment: the strain hardening modulus value ⁇ G P > of at least three polyethylene materials for which the known design lifetime T is obtained, including:
  • the strain hardening modulus value ⁇ G Pi > of each of the standard samples is obtained by a high temperature tensile test, where i is the number of the standard sample;
  • the strain hardening modulus value ⁇ G P > and the design service life T of various polyethylene materials are known in the prior art, the improvement of the material processing process, the test environment, the test equipment, etc. are improved, so as to improve the calculation of the remaining The accuracy of the service life can be re-measured for the value of the known strain hardening modulus value ⁇ G P >.
  • the strain hardening modulus value ⁇ G Pi > of each of the standard samples is obtained, and the strain hardening of each polyethylene material is obtained.
  • the average root mean square of the modulus is ⁇ G P >, which further improves the accuracy of the strain hardening modulus value ⁇ G P >.
  • the present application further proposes another embodiment: preparing the standard sample of the at least three polyethylene materials, and preparing at least five standard samples for each polyethylene material, including:
  • the at least five standard samples of each polyethylene material are prepared in a compression molding apparatus, the standard sample being a dumbbell-shaped sheet including a middle test portion and a clamping portion at both ends, the thickness of the dumbbell-shaped sheet 0.3mm-1mm;
  • the sample After annealing the at least five standard samples in an environment of 115 ° C - 125 ° C for one hour, the sample was cooled to room temperature at a cooling rate of less than 2 ° C / min.
  • the preset number of the standard sample may be twice or three times the actual target quantity, so as to avoid the occurrence of defects or defects in the standard sample during the manufacturing process. Insufficient and reserve enough test quantities for subsequent tensile testing to prevent too many tensile test failures and require more of the standard sample.
  • the shape of the standard sample can be referred to the shape of the existing tensile test, and the thickness can be determined according to the thickness of the in-service polyethylene pipe.
  • the present application further provides an embodiment in which the strain hardening modulus value ⁇ G Pi > of each of the standard samples is obtained by a high temperature tensile test, including:
  • dumbbell-shaped sheet Place the dumbbell-shaped sheet in an incubator at 80 ° C for 30 min - 60 min;
  • the two end clamping portions are clamped on a high temperature tensile testing machine, and a pre-stress of 0.4 MPa is applied at a strain rate of 5 mm/min;
  • the dumbbell-shaped sheet was stretched at a constant moving speed of 20 mm/min, and the data value of the stretching ratio ⁇ of the middle test portion between 8 and 12 was collected, the stretching ratio Where L 0 is the initial length of the middle test portion, and L is the length after stretching of the middle test portion;
  • ⁇ j is the value of the corresponding true stress ⁇ true when ⁇ takes the jth value
  • ⁇ j+1 is ⁇ when the j+1th value is obtained, corresponding to The value of the true stress ⁇ true
  • m is the upper limit of the number of ⁇ values
  • N is the total number of said standard samples measured.
  • the present application further proposes another embodiment: the obtaining a test sample from an in-service polyethylene pipe, comprising:
  • the test sample is a dumbbell-shaped sheet including a middle test portion and a clamping portion at both ends
  • the dumbbell-shaped sheet has a thickness of 0.3 mm to 1 mm.
  • the test sample in this embodiment may obtain a material from the in-service polyethylene pipe, and then place the material in a sample machine for cutting processing to be processed into a dumbbell shape conforming to the shape of the standard sample. Sheet.
  • the parameter for measuring the strain hardening modulus value G P ' of the test sample may also be the same as the parameter for measuring the standard sample, so the strain hardening modulus value of the test sample is measured.
  • ⁇ G P '> including:
  • test sample Place the test sample in an incubator at 80 ° C for 30 min - 60 min;
  • the clamping portion of the test sample was clamped on a high-temperature tensile tester, and a pre-stress of 0.4 MPa was applied at a strain rate of 5 mm/min;
  • the test specimen was stretched at a constant moving speed of 20 mm/min, and a data value of a draw ratio ⁇ ' of 8-12 between the middle portion of the test specimen was collected, the draw ratio
  • L 0 ' is the initial length of the test portion in the middle portion of the test sample
  • L' is the length after stretching of the test portion in the middle portion of the test sample
  • the strain hardening modulus value ⁇ G P '> of the test sample including:
  • the root mean square average value of the strain hardening modulus value ⁇ G Pi '> was calculated, and the root mean square average value was taken as the strain hardening modulus value ⁇ G P '> of the test sample.
  • the strain hardening modulus value ⁇ G Pi '> of the plurality of test specimens is taken as the root mean square average value, and the reliability of the strain hardening modulus value ⁇ G P '> can be further improved.
  • test sample may be taken from different positions of the in-service polyethylene pipe to obtain the remaining service life of the test sample at different positions, thereby enabling the user to understand the remaining use of the in-service polyethylene pipe at different positions.
  • the difference in life is to be treated differently; or the strain hardening modulus value ⁇ G Pi '> of the test specimen at different positions is taken as the root mean square average value as the overall strain hardening modulus value of the position of the test specimen ⁇ G P '> to reduce the chance of error caused by a single test sample.
  • test specimens it is also possible to take a plurality of test specimens at the same position of the in-service polyethylene pipe to prepare a plurality of test specimens, and to take a plurality of test specimens at another position to prepare a plurality of test specimens. As another set of test samples to further improve the accuracy of the test.
  • the present application also provides a test system for the remaining service life of the pipe, comprising:
  • Sample preparation device used for obtaining test samples from in-service polyethylene pipes
  • Tensile test device for measuring the strain hardening modulus value ⁇ G P '> of the test sample
  • T a 0 + a 1 ⁇ ⁇ G p > + a 2 ⁇ ⁇ G p > 2 + ... + a n ⁇ ⁇ G p > n , where a 0 , a 1 , a 2 ... a n is a preset coefficient, n is a preset maximum number of times of the function, and takes a positive integer; substituting the strain hardening modulus value ⁇ G P '> of the test sample into the function to replace the strain hardening modulus value ⁇ G P >, the service life is calculated, and the service life is the remaining service life of the test specimen.
  • the sample preparation device may be an existing sample preparation machine, and the tensile test device may be a high temperature tensile test machine.
  • the high temperature tensile testing machine can adopt the tensile structure shown in FIG. 2 to FIG. 4, including:
  • a pair of clamps 2 that is, a first clamp 2A and a second clamp 2B in the drawing, the first clamp 2A and the second clamp 2B are fixed to the frame 1, and the first clamp 2A and the second clamp 2B are provided with clamps
  • the clamping groove at one end of the sample 9 is opposite to the opening direction of the clamping groove of the first jig 2A and the second jig 2B to respectively clamp the two ends of the sample 9 to fix the sample 9;
  • the moving device 3 at least one jig is fixed to the frame 1 by the moving device 3 to move one of the jigs in a direction away from or close to the other jig; in FIG. 2, the first jig 2A is fixed by the moving device 3, moving The device 3 can drive the first clamp 2A to move upward or downward in the illustration to increase or decrease the distance between the first clamp 2A and the second clamp 2B to reach the first clamp 2A and the second clamp 2B.
  • auxiliary locking device is fixed on the clamp 2, the auxiliary locking device includes a locking station and a avoidance station, and when the auxiliary locking device is located at the locking station, the clamping groove is applied Auxiliary clamping force to increase the clamping force on the sample 9, so that the sample 9 is not easy to slide or shift during the stretching process, and the accuracy of the tensile test is increased;
  • the force measuring device 4 is connected to at least one clamp for measuring the tensile force generated when the moving device 3 moves; taking FIG. 2 as an example, since the sample 9 is clamped to the first clamp 2A and the second clamp 2B Between when the moving device 3 drives the first clamp 2A to move upward, the sample 9 will generate a certain resistance; when the tensile force exceeds the resistance, the distance between the first clamp 2A and the second clamp 2B increases.
  • the sample 9 is elongated; the force measuring device 4 is used to measure the tensile force when the sample 9 is elongated;
  • the length measuring device is fixed to the frame 1, and includes a measuring head whose measuring range is larger than the moving range of the jig 2 to measure the real-time length of the sample 9 being elongated during the movement of the jig 2.
  • the auxiliary locking device is pre-located in the avoidance station, so that both ends of the sample 9 are respectively inserted into the clamping groove of the first jig 2A and the clamping groove of the second jig 2B and clamped; Immediately after, the auxiliary locking device is adjusted to the locking station to increase the clamping force on the sample 9; the moving device 3 is restarted, so that the moving device 3 drives the first clamp 2A away from the second clamp 2B.
  • the direction of movement for example, moving upward in FIG. 2, causes the sample 9 to be stretched; during the stretching process, the force measuring device 4 measures the tensile force of the tensile sample 9, and the length measuring device measures the real time of the sample 9.
  • Stretching length the aforementioned strain hardening modulus value can be calculated according to the tensile force and the stretching length.
  • the auxiliary locking device in the application can strengthen the friction between the sample 9 and the clamp 2, so that the sample 9 is not easy to slide during the stretching process, thereby improving the precision of the tensile test and reducing the tensile test sample. The probability of failure.
  • each of the clamps includes a pair of clamping panels 21 and a fixing seat 22 having a positioning groove in the middle, and the pair of clamping panels 21 are fixed on opposite sides of the positioning groove;
  • One surface of the clamping panel 21 is a fixing surface provided with an anti-slip pattern, and the other surface is an adjustment surface to which a screw is connected; and the clamping groove is formed between the fixing surfaces of the pair of clamping panels 21,
  • One end of the screw is rotatably fixed to the adjusting surface, and the other end penetrates the fixing base and is connected with an adjusting knob 23, and the rotating shaft of the screw is perpendicular to the adjusting surface to convert the rotation of the adjusting knob 23 into a clamping
  • the panel 21 moves linearly along the direction of the rotation axis of the screw to adjust the distance between the pair of clamping panels 21, thereby clamping the sample 9 of different thicknesses; after the test is completed, the clamping panel 21 is enlarged by the adjustment knob 23.
  • the distance is also convenient for taking out sample 9.
  • the adjustment knobs 23 on the two clamps may be disposed on the same side to adjust the clamp panel 21 on the same side of the clamp 2 to avoid misalignment of the clamping groove and ensure clamping
  • the sample 9 is held in a vertical or horizontal position to improve the test accuracy; and it is also convenient to reserve the adjustment space on one side of the test device.
  • the auxiliary locking device includes a first locking mechanism and a second locking mechanism
  • Each of the clamping panels 21 is respectively provided with a card slot 211, and the lock first locking mechanism and the second locking mechanism respectively comprise two ribs, and the two ribs respectively and the pair of clips
  • the card slot 211 on the same side of the panel 21 is matched; when the auxiliary locking device is located in the locking station, the two ribs are respectively inserted into the card slots 211 on the same side of the pair of clamping panels 21 Inside.
  • the clamping force between the two clamping panels 21 is maintained; in particular, when the lock first locking mechanism and the second locking mechanism
  • the distance between the two ribs of each locking mechanism is adjustable, and by narrowing the distance between the two ribs, the two clamping panels 21 can be added.
  • the clamping force between the two causes the sample 9 held between the two holding panels 21 to not slip.
  • the card slot and the position of the rib can also play the same role; that is, the auxiliary locking device includes a first locking mechanism and a second locking mechanism; each of the clamping panels Two sides of the 21 are respectively provided with ribs, and the lock first locking mechanism and the second locking mechanism respectively comprise two card slots, and the two card slots are respectively on the same side of the pair of clamping panels 21
  • the ribs are matched; when the auxiliary locking device is located at the locking station, the ribs on the same side of the pair of clamping panels 21 are respectively inserted into the two card slots.
  • the lock first locking mechanism and the second locking mechanism are mechanisms capable of applying an auxiliary clamping force
  • the distance between the two card slots of each locking mechanism is adjustable by reducing the two cards The distance between the slots increases the clamping force between the two clamping panels 21.
  • At least one of the pair of clamping panels 21 may be provided with a recess, the shape of which may coincide with the shape of one end of the clamped sample 9, or the size of the partial shape may be larger than the contour of one end of the sample 9, only The concave portion can catch the sample 9 and is not easy to slip.
  • the recess may be disposed on only one of the clamping panels 21; more preferably, the pair of clamping panels 21 are provided with the recesses, the recesses having a depth less than half the thickness of the sample 9, ie:
  • the thickness of the sample 9 is greater than the sum of the depths of the two recesses to equalize the force of the two clamping panels 21, improving the reliability of the clamping and the service life of the clamping panel 21.
  • the recess can also position the sample 9 to hold the sample 9 in the optimum position.
  • the depth of the recess may be from 0.1 mm to 3 mm depending on the thickness of the sample 9.
  • the surface of the recess is provided with a non-slip pattern to increase the friction between the sample 9 and the recess when the sample 9 is stretched, thereby increasing the clamping force.
  • each of the clamps 2 further comprises a sample positioning device, as shown in FIG. 4, the sample positioning device comprises a fixing assembly 51 and a positioning assembly 52, and the fixing assembly 51 is fixed to one On the side of the clamping panel 21, the positioning assembly 52 is perpendicular to the clamping panel 21 and faces the other clamping panel 21.
  • the sample positioning device comprises a fixing assembly 51 and a positioning assembly 52, and the fixing assembly 51 is fixed to one
  • the positioning assembly 52 is perpendicular to the clamping panel 21 and faces the other clamping panel 21.
  • a sliding slot may be disposed on the fixing component 51 to enable the sample positioning device to slide along the sliding slot to adjust the position of the positioning assembly 52 to adjust the positioning reference position of the sample 9.
  • the measuring head of the length measuring device comprises a first measuring rod 61 which is aligned with one end of the length of the sample 9 to be tested, and a second measuring rod 62 which is aligned with the other end of the length of the sample 9 to be tested;
  • the first measuring rod 61 moves in synchronism with one of the jigs
  • the second measuring rod 62 moves in synchronism with the other jig to ensure that the distance between the first measuring rod 61 and the second measuring rod 62 is synchronized with the length of the sample 9.
  • one or both of the clamps 2 can also be in a stationary state, and the corresponding first measuring rod 61 and/or second measuring rod 62 are also in a stationary state.
  • the two measuring rods in this embodiment can be mounted on the frame 1 or can be mounted on a sliding rail 8 and can be separated according to the stretching of the sample 9 to identify the tensile length of the sample 9 in real time. .
  • the measuring head comprises a non-contact video optical measuring component.
  • the non-contact video optical measuring component is an optical measuring method for measuring the line deformation between two points of a target member or an object, and is usually composed of a lighting field, a camera and a control chip.
  • the deformation process is directly recorded by the camera, and the measured signal is not required to be amplified and digital-analog converted, the measurement speed and accuracy are improved, and the measurement accuracy is higher than the existing extensometer; moreover, the non-contact measurement does not test Any damage is caused, thus avoiding the influence on the tensile test; during the test, the measuring head is not required to be removed, and the strain of the sample can be tracked throughout the process; and the sample is prevented from being broken when the sample is broken in the existing stretching equipment. The danger of falling down and falling.
  • the pair of clamps 2 in the present application may be arranged up and down, or may be arranged left and right.
  • the first clamp 2A and the second clamp 2B is set up and down.
  • the moving device 3 is fixed above the upper clamp, as shown in FIG. 2, the force measuring device 4 is fixed to the bottom of the lower clamp, and passes through The tensile force applied to the lower jig was measured to obtain the tensile force of the tensile sample 9.
  • the tensile testing device in the present application may further include a heating device 7 for heating the sample 9 to increase the activity of the polymer material to obtain tensile test results under different parameter conditions.

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Abstract

一种管材剩余使用寿命的测试方法和测试系统，管材剩余使用寿命的测试方法包括：获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞（S10）；根据应变硬化模量值＜G P＞与设计使用寿命值T构建函数：T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n，其中，a 0、a 1、a 2......a n为预设系数，n为预设的函数最高次数，取正整数（S20）；从在役管材中获取测试试样（a）（S30）；测量测试试样（a）的应变硬化模量值＜G P'＞（S40）；将测试试样（a）的应变硬化模量值＜G P'＞代入函数替换应变硬化模量值＜G P＞，算出使用寿命，即为测试试样（a）的剩余使用寿命（S50）。可得到测试试样（a）的剩余使用寿命，以作为在役管材因慢速裂纹扩展而失效的剩余使用寿命参考数值，及时发现在役管材因慢速裂纹扩展而失效的风险。

Description

管材剩余使用寿命的测试方法和测试系统 技术领域
本申请涉及材料测试技术，尤其是一种管材剩余使用寿命的测试方法和测试系统。
背景技术
聚乙烯(PE)燃气管道由于其耐腐蚀性强、力学性能好、使用寿命长及环保等优势已逐步取代钢管，作为天然气输送的常用手段，在城市燃气管道网中广泛使用。目前，铺设的在役聚乙烯燃气管材主要为第三代PE100级管材，其设计寿命为58年，至今已经投入使用约20年左右；由于燃气管材常年深埋地底，持续受到土壤压力、热氧老化、点载荷及腐蚀等各种外界因素影响，随着服役时间的增加，管材自身容易形成局部应力集中，最终导致管材容易出现慢速裂纹失效，直接影响在役PE燃气管材的剩余使用寿命。在役PE燃气管材是承压特种设备，运输的都是易燃易爆品，一旦发生燃气泄漏，后果将是致命的；所以，在役PE燃气管材剩余使用寿命能否达到预先设计寿命，直接影响到城市燃气管道网的正常运行及人民的生命财产安全，是一项及其重要的技术指标。但到目前为止，缺乏针对在役PE燃气管材剩余使用寿命的快速有效评价方法，不少城市的燃气管道网由于缺乏准确有效的剩余使用寿命有效预测方法，无法及时有效地对失效管材进行更换，导致燃气泄漏事故和质量安全事故时有发生，甚至还引发了爆炸事故，给城市公共安全造成了严重的隐患。
因此,准确有效地对在役PE管材剩余使用寿命分析，以及时更换失效管材，可有效减少燃气泄露等事故；而且，提出一种试验周期短、试验条件简单、成本低的在役PE燃气管材剩余使用寿命预测加速评价方法，可为PE燃气管材的质量和成本控制提供强有力的安全保证，可缩短新型燃气管材专用树脂的开发周期，还可保障现有燃气管道系统的安全运行。
发明内容
本申请的目的旨在至少解决上述技术缺陷之一，特别是针对管道系统的剩余使用寿命难以估算的问题。
本申请提供了一种管材剩余使用寿命的测试方法，包括：获取已知设计使用寿命T的至少三种聚乙烯材料各自对应的应变硬化模量值<G p>；根据所述应变硬化模量值<G p>与所述设计使用寿命T，构建函数：
T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n,其中，a 0、a 1、a 2……a n为预设系数，n为预设的所述函数最高次数，取正整数；从在役聚乙烯管材中获取测试试样；测量所述测试试样的应变硬化模量值＜G P'＞；将所述测试试样的应变硬化模量值＜G P'＞代入所述函数替换应变硬化模量值＜G P＞，算出使用寿命，所述使用寿命为所述测试试样的剩余使用寿命。
优选地，所述推算所述测试试样的剩余使用寿命之后，还包括：根据所述剩余使用寿命，判断是否更换所述在役聚乙烯管材。
优选地，所述判断是否更换在役聚乙烯管材，包括：当所述剩余使用寿命不大于第一预设值，则更换所述在役聚乙烯管材；当所述剩余使用寿命大于所述第一预设值、 小于第二预设值，则定期检测所述在役聚乙烯管材。
优选地，所述获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，包括：制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样；通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞，其中，i为所述标准试样的编号；根据所述每片标准试样的应变硬化模量值＜G Pi＞，计算每种聚乙烯材料的应变硬化模量值的均方根平均值，将所述均方根平均值作为所述应变硬化模量值＜G P＞。
优选地，所述制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样,包括：在压模设备中制备出每种聚乙烯材料的所述至少五片标准试样，所述标准试样为包括中部测试部分和两端夹持部分的哑铃状薄片，所述哑铃状薄片的厚度为0.3mm-1mm；将所述至少五片标准试样置于115℃-125℃的环境下退火一小时后，以小于2℃/min的冷却速度使试样冷却至室温。
优选地，所述通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞,包括：将所述哑铃状薄片置于80℃的恒温箱中放置30min-60min；将所述两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；以20mm/min的恒定移动速度拉伸所述哑铃状薄片，收集所述中部测试部分的拉伸比λ在8-12之间的数据值，所述拉伸比
Figure PCTCN2018101826-appb-000001
其中L 0为所述中部测试部分的初始长度，所述L为所述中部测试部分拉伸后的长度；记录所述拉伸比λ和所述拉伸过程中真应力σ true的对应关系：
Figure PCTCN2018101826-appb-000002
其中,F为与所述拉伸比的数据值对应的拉伸力，A 0为所述哑铃状薄片中部测试部分的初始横截面积；根据Neo-Hookean本构模型，以及λ＝12与λ＝8时，所述对应关系的斜率K，确定每片所述标准试样的应变硬化模量值＜G Pi＞为：＜G Pi＞＝20K。
优选地，所述从在役聚乙烯管材中获取测试试样，包括：从所述在役聚乙烯管材中获取测试材料，将所述测试材料在制样机中加工为所述测试试样；所述测试试样为包括中部测试部分和两端夹持部分的哑铃状薄片，所述哑铃状薄片的厚度为0.3mm-1mm
优选地，所述测量所述测试试样的应变硬化模量值G P'，包括：将所述测试试样置于80℃的恒温箱中放置30min-60min；将所述测试试样的两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；以20mm/min的恒定移动速度拉伸所述测试试样，收集所述测试试样中部测试部分的拉伸比λ’在8-12之间的数据值，所述拉伸比
Figure PCTCN2018101826-appb-000003
其中L 0’为所述测试试样中部测试部分的初始长度，所述L’为所述测试试样中部测试部分拉伸后的长度；记录所述拉伸比λ’和所述拉伸过程中真应力σ true’的对应关系：
Figure PCTCN2018101826-appb-000004
其中,F’为与所述拉伸比λ’的数据值对应 的拉伸力，A0’为所述测试试样中部测试部分的初始横截面积；根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值＜G P'＞为＜G P'＞＝20K’。
优选地，所述测试试样至少为两片；所述根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值＜G P'＞，包括：确定每一片所述测试试样的应变硬化模量值＜G Pi'＞；计算所述应变硬化模量值＜G Pi'＞的均方根平均值，将所述均方根平均值作为所述测试试样的应变硬化模量值＜G P'＞。
本申请还提出一种管材剩余使用寿命的测试系统，包括：制样装置：用于从在役聚乙烯管材中获取测试试样；拉伸测试装置：用于测量所述测试试样的应变硬化模量值＜G P'＞；中央处理器：用于获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，所述至少三种聚乙烯材料为不同型号的聚乙烯材料；根据所述应变硬化模量值＜G P＞与所述设计使用寿命T，构建函数：
T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n,其中，a 0、a 1、a 2……a n为预设系数，n为预设的所述函数最高次数，取正整数；将所述测试试样的应变硬化模量值＜G P'＞代入所述函数替换应变硬化模量值＜G P＞，算出使用寿命，所述使用寿命为所述测试试样的剩余使用寿命。
本申请的有益效果如下：
1、本申请首先对已知设计使用寿命T的聚乙烯材料进行分析，以构建应变硬化模量值＜G P＞与所述设计使用寿命T的函数；再从在役聚乙烯管材中获取测试试样，测量所述在役聚乙烯管材的应变硬化模量值＜G P'＞，最后代入所述函数替换应变硬化模量值＜G P＞，得到使用寿命，即为所述测试试样的剩余使用寿命。通过采用所述测试试样的剩余使用寿命作为所述在役聚乙烯管材因慢速裂纹扩展而失效的剩余使用寿命参考数值，可及时发现在役聚乙烯管材因慢速裂纹扩展而失效的风险；本申请可有效评估不同的在役聚乙烯管材的剩余使用寿命，以根据所述剩余使用寿命对所述在役聚乙烯管材采取不同处理措施。
2、本申请可通过测量多个所述标准试样的应变硬化模量值，并取均方根平均值，以修正现有技术中已知聚乙烯材料的应变硬化模量值；并将所述标准试样的制作参数和测量参数作为后续测试试样的测量参数，可进一步提高所述剩余使用寿命的推算结果；本申请尤其适用于燃气管道的剩余使用寿命分析。
本申请附加的方面和优点将在下面的描述中部分给出，这些将从下面的描述中变得明显，或通过本申请的实践了解到。
附图说明
本申请上述的和/或附加的方面和优点从下面结合附图对实施例的描述中将变 得明显和容易理解，其中：
图1为本申请所述测试方法第一实施例的流程示意图。
图2为本申请中拉伸测试装置一个实施例的结构示意图；
图3为本申请中拉伸测试装置又一实施例的结构示意图；
图4为本申请中拉伸测试装置另一实施例的结构示意图。
具体实施方式
下面详细描述本申请的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，仅用于解释本申请，而不能解释为对本申请的限制。
本技术领域技术人员可以理解，除非特意声明，这里使用的单数形式“一”、“一个”、“所述”和“该”也可包括复数形式。应该进一步理解的是，本申请的说明书中使用的措辞“包括”是指存在所述特征、整数、步骤、操作、元件和/或组件，但是并不排除存在或添加一个或多个其他特征、整数、步骤、操作、元件、组件和/或它们的组。应该理解，当我们称元件被“连接”到另一元件时，它可以直接连接到其他元件，或者也可以存在中间元件。此外，这里使用的“连接”可以包括无线连接。这里使用的措辞“和/或”包括一个或更多个相关联的列出项的全部或任一单元和全部组合。
本技术领域技术人员可以理解，除非另外定义，这里使用的所有术语(包括技术术语和科学术语)，具有与本申请所属领域中的普通技术人员的一般理解相同的意义。还应该理解的是，诸如通用字典中定义的那些术语，应该被理解为具有与现有技术的上下文中的意义一致的意义，并且除非像这里一样被特定定义，否则不会用理想化或过于正式的含义来解释。
如图1所示的流程图，本申请提出一种管材剩余使用寿命的测试方法第一实施例，包括如下步骤：
步骤S10：获取已知设计使用寿命T的至少三种聚乙烯材料各自对应的应变硬化模量值＜G P＞；
现有技术中已公开多种材料的性能参数，例如材料的弹性模量、泊松比、密度、热膨胀系数、屈服强度、抗拉强度、伸长率、应变硬化模量值等。在材料测试过程中，通过相关性分析，可发现所述性能参数中的应变硬化模量值与材料的慢速裂纹扩展高度相关，故可通过测试材料的应变硬化模量值推算材料的慢速裂纹扩展而失效的剩余使用寿命。
对已知设计使用寿命T的不同型号的聚乙烯材料的应变硬化模量值＜G P＞，进行相关性分析，可获得所述应变硬化模量值＜G P＞与所述设计使用寿命T之间的函数关系。不同型号的聚乙烯材料包括各聚乙烯生厂商命名的不同牌号的聚乙烯材料制成的管材，例如：采用100级高密度聚乙烯制成的管材，其设计使用寿命T为58年，或采用耐开裂聚乙烯PE100-RC制作的管材，其设计使用寿命T为100年等。
所述应变硬化模量值＜G P＞所对应的设计使用寿命T可采用各厂商标称的数值，亦可自行进行测试，以获得更准确的设计使用寿命T的数值。
步骤S20：根据所述应变硬化模量值＜G P＞与所述设计使用寿命T，构建函数：
T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n,其中，a 0、a 1、a 2……a n为预设系数，n为预设的所述函数最高次数，取正整数；
在本申请中，已知至少三种不同型号聚乙烯材料各自对应的设计使用寿命T和应变硬化模量值＜G P＞，可通过牛顿迭代法等分析方法求解方程，得到各预设系数的数值，从而得到应变硬化模量值＜G P＞与设计使用寿命T之间的函数关系。将同一种型号聚乙烯材料的应变硬化模量值＜G P＞和设计使用寿命T作为一个数组，当有两组数组时，可求得误差函数为零的直线方程，但其误差较大；为提高迭代精度，本申请可取更多所述数组，以获得一元n次的拟合方程，提高构建所述函数的准确性。所述数组的个数可超过所述正整数n，再通过牛顿迭代法拟合出最小化误差的函数，以使拟合的函数误差进一步缩小；所述数组中的一部分数值可能位于拟合的函数曲线上，另一部分则均匀地分布于所述函数曲线的两侧。所述数组的数量越多，构建的函数误差率越低。
步骤S30：从在役聚乙烯管材中获取测试试样；
所述在役聚乙烯管材为正在使用中的管材，例如埋于地下的燃气管材等。在步骤S20中拟合出所述应变硬化模量值＜G P＞与所述设计使用寿命T的函数后，只需得到在役聚乙烯管材的应变硬化模量值即可得出在役聚乙烯管材的剩余使用寿命。所述从在役聚乙烯管材中获取测试试样的步骤，可包括直接从在役聚乙烯管材中截取部分管材样品，并将该样品加工为合适的测试试样形状的步骤。
步骤S40：测量所述测试试样的应变硬化模量值＜G P'＞；
所述测量所述测试试样的应变硬化模量值＜G P'＞可采用现有的拉伸实验设备进行测量，亦可根据所述测试试样的具体条件设计或组装合适的拉伸试验设备。测量所述测试试样的应变硬化模量值＜G P'＞所选用的参数优选地与测量所述已知设计使用寿命T的至少三种聚乙烯材料各自对应的应变硬化模量值＜G P＞所选用的的参数一致；所述参数包括测试试样的尺寸、测试试样的加热温度与时间、拉伸过程中的拉伸力与拉伸时间等。
步骤S50：根据所述函数与所述测试试样的应变硬化模量值＜G P'＞，推算所述测试试样的剩余使用寿命。
得到所述测试试样的应变硬化模量值＜G P'＞后，将其代入步骤S20中构建的函数(具体为将＜G P'＞替换函数中的＜G P＞)，即可计算得到所述测试试样的使用寿命，此时所计算得出的使用寿命即所述测试试样的剩余使用寿命。由于所述测试试样的材料取自在役聚乙烯管材，其材料在使用环境中已发生变化，且变化与仍在使用中的在役聚乙烯管材相同，故可通过该测试试样的剩余使用寿命推算在役聚乙烯管材的剩余使用寿命。在役聚乙烯管材的剩余使用寿命可与所述测试试样的剩余使用寿命相同，亦可存在一定的比例关系。
现有的聚乙烯管材在生产、运输及施工等过程中可能造成的缺陷，并在后续使用 中，受到温度、压力和点载荷等外界因素的影响，可能存在蠕变、应力松弛、快速裂纹扩展、慢速裂纹扩展及材料老化等多种失效模式；其中，慢速裂纹扩展是最主要的失效模式。虽然现有的聚乙烯管材在设计时已预估设计使用寿命，但由于实际使用参数的不同、使用环境的不同等因素影响，管材的实际使用寿命并不一定与设计使用寿命相符。如前所述，慢速裂纹扩展是管材最主要的失效模式，而慢速裂纹扩展的剩余使用寿命又与所述应变硬化模量值高度相关，故本申请可先通过分析构建应变硬化模量值与设计使用寿命的函数关系,再从在役聚乙烯管材中获取测试试样，以根据所述测试试样的应变硬化模量值＜G P'＞推算所述测试试样的剩余使用寿命；根据所述测试试样的剩余使用寿命即可推算所述在役聚乙烯管材因慢速裂纹扩展而失效的情况下对应的剩余使用寿命。
故本申请可及时发现在役聚乙烯管材因慢速裂纹扩展而失效的风险，避免了在役管道在设计使用寿命之前失效而引发的危险，例如聚乙烯燃气管道因慢速裂纹扩展引发燃气泄漏事故等；通过本申请，可有效评估在役的不同聚乙烯管材的剩余使用寿命，以根据所述剩余使用寿命对在役聚乙烯管材进行不同处理。
基于前一实施例中所述测试试样的剩余使用寿命，本申请提出另一实施例：所述推算所述测试试样的剩余使用寿命之后，还包括：
根据所述剩余使用寿命，判断是否更换所述在役聚乙烯管材。
虽然所述测试试样取自于所述在役聚乙烯管材，但所述测试试样后续可能存在加工成型为适合测试的形状等工艺，故所述测试试样的剩余使用寿命与实际在役聚乙烯管材的剩余使用寿命可能存在差距，可参考所述在役聚乙烯管材的使用环境、安全系数、所述测试试样的加工工艺等具体情况，根据所述剩余使用寿命，判断是否需要更换所述在役聚乙烯管材。例如：由于使用环境恶劣，在役管材距离原设计使用寿命还有20年，但采用本申请的测试方法推算出的所述剩余使用寿命仅为3年，且该在役聚乙烯管材涉及环境污染物质的输送，用户可根据所述多种因素综合判断是否需要立即更换所述在役聚乙烯管材，或最迟于何时更换该在役聚乙烯管材，或将该在役聚乙烯管材替换为其它材质。
基于上一实施例，本申请提出另一实施例：所述判断是否更换在役聚乙烯管材，包括：
当所述剩余使用寿命不大于第一预设值，则更换所述在役聚乙烯管材；
当所述剩余使用寿命大于所述第一预设值、小于第二预设值，则定期检测所述在役聚乙烯管材。
在实际应用中，可根据所述剩余使用寿命的数值采取对应的措施，例如立即更换所述在役聚乙烯管材，或定期检测所述在役聚乙烯管材，以便为用户决策提供参考。还可根据所述在役聚乙烯管材的使用条件设置不同的参数。例如：对于给水管道，若所述剩余使用寿命大于5年，在继续正常使用；若所述剩余使用寿命大于2年小于5年，则每年定期检测一次，以监控该在役聚乙烯管材的使用情况，防止水管爆裂；对于燃气管道，若所述剩余使用寿命大于5年小于8年，则每年定期检测一次，以监控该在役聚乙烯管材，防止燃气泄漏。
基于第一实施例，本申请还提出第二实施例：所述获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，包括：
制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样；
通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞，其中，i为所述标准试样的编号；
根据所述每片标准试样的应变硬化模量值＜G Pi＞，计算每种聚乙烯材料的应变硬化模量值的均方根平均值，将所述均方根平均值作为所述应变硬化模量值＜G P＞。
虽然现有技术中已知多种聚乙烯材料的应变硬化模量值＜G P＞与设计使用寿命T，但由于材料本身加工工艺的改进、测试环境、测试设备等改进，为提高推算所述剩余使用寿命的精度，可对已知应变硬化模量值＜G P＞的数值重新进行测定。本实施例通过重新制作每种聚乙烯材料的至少五片标准试样，以分别得到每片所述标准试样的应变硬化模量值＜G Pi＞，再将每种聚乙烯材料的应变硬化模量的均方根平均值作为＜G P＞，可进一步提高应变硬化模量值＜G P＞的精度。
基于第二实施例，本申请还提出另一实施例：所述制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样,包括：
在压模设备中制备出每种聚乙烯材料的所述至少五片标准试样，所述标准试样为包括中部测试部分和两端夹持部分的哑铃状薄片，所述哑铃状薄片的厚度为0.3mm-1mm；
将所述至少五片标准试样置于115℃-125℃的环境下退火一小时后，以小于2℃/min的冷却速度使试样冷却至室温。
制作所述标准试样时，预设的所述标准试样的数目可为实际目标数量的两倍或三倍，以避免所述标准试样在制作过程中产生瑕疵或成为不良品而导致数量不足，并为后续拉伸测试预留足够的测试数量，以防止拉伸测试失败次数过多而需要更多的所述标准试样。所述标准试样的形状可参照现有拉伸测试的形状，其厚度可根据在役聚乙烯管材的厚度确定。
基于上一实施例，本申请进一步提出如下实施例：所述通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞,包括：
将所述哑铃状薄片置于80℃的恒温箱中放置30min-60min；
将所述两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；
以20mm/min的恒定移动速度拉伸所述哑铃状薄片，收集所述中部测试部分的拉伸比λ在8-12之间的数据值，所述拉伸比
Figure PCTCN2018101826-appb-000005
其中L 0为所述中部测试部分的初始长度，L为所述中部测试部分拉伸后的长度；
记录所述拉伸比λ和所述拉伸过程中真应力σ true的对应关系：
Figure PCTCN2018101826-appb-000006
其中,F为与所述拉伸比的数据值对应的拉伸力，A 0为所述哑铃状薄片中部测试部分的初始横截面积；
根据Neo-Hookean本构模型，以及λ＝12与λ＝8时，所述对应关系的斜率K，确定每片所述标准试样的应变硬化模量值＜G Pi＞为：
＜G Pi＞＝20K。
在本实施例中，所述＜G Pi＞＝20K的具体推算过程如下：
Figure PCTCN2018101826-appb-000007
其中j为拉伸测试中λ的取值编号，σ j为λ取第j个值时，对应的的真应力σ true的值，σ j+1为λ取第j+1个值时，对应的真应力σ true的值，m为λ取值个数的数量上限；将
Figure PCTCN2018101826-appb-000008
代入上述公式，根据Neo-Hookean本构模型，可推导出：
Figure PCTCN2018101826-appb-000009
其中，K为λ∈(λ 1,λ 2)时所述对应关系的斜率，C为常数；当取λ 1＝8、λ 2＝12时，
Figure PCTCN2018101826-appb-000010
则有：
Figure PCTCN2018101826-appb-000011
得到每片所述标准试样的应变硬化模量值＜G Pi＞后，再根据所述每片标准试样的应变硬化模量值＜G Pi＞，计算每种聚乙烯材料的应变硬化模量的均方根平均值，将所述均方根平均值作为所述应变硬化模量值＜G P＞，即：
Figure PCTCN2018101826-appb-000012
其中，N为测量的所述标准试样的总数量。
基于第二实施例，本申请还提出另一实施例：所述从在役聚乙烯管材中获取测试试样，包括：
从所述在役聚乙烯管材中获取测试材料，将所述测试材料在制样机中加工为所述测试试样；所述测试试样为包括中部测试部分和两端夹持部分的哑铃状薄片，所述哑铃状薄片的厚度为0.3mm-1mm。
本实施例中的所述测试试样可从所述在役聚乙烯管材中获取材料，再将该材料置于制样机中进行切削加工，以加工为与所述标准试样形状一致的哑铃状薄片。
进一步地，所述测量所述测试试样的应变硬化模量值G P'的参数亦可与测量所述标准试样的参数相同，故所述测量所述测试试样的应变硬化模量值＜G P'＞，包括：
将所述测试试样置于80℃的恒温箱中放置30min-60min；
将所述测试试样的两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；
以20mm/min的恒定移动速度拉伸所述测试试样，收集所述测试试样中部测试部分的拉伸比λ’在8-12之间的数据值，所述拉伸比
Figure PCTCN2018101826-appb-000013
其中L 0’为所述测试试样中部测试部分的初始长度，L’为所述测试试样中部测试部分拉伸后的长度；
记录所述拉伸比λ’和所述拉伸过程中真应力σ true’的对应关系：
Figure PCTCN2018101826-appb-000014
其中,F’为与所述拉伸比λ’的数据值对应的拉伸力，A 0’为所述测试试样中部测试部分的初始横截面积；
根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值G P’为
＜G P'＞＝20K’。
所述＜G P'＞＝20K’的推算过程与所述标准试样中的推算过程相同，在此不再赘述。
为提高测试的准确性，所述测试试样至少为两片；所述根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值＜G P'＞，包括：
确定每一片所述测试试样的应变硬化模量值＜G Pi’＞；
计算所述应变硬化模量值＜G Pi’＞的均方根平均值，将所述均方根平均值作为所述测试试样的应变硬化模量值＜G P'＞。
本实施例对多片所述测试试样的应变硬化模量值＜G Pi’＞取均方根平均值，可进一步提高所述应变硬化模量值＜G P'＞的可靠性。
进一步地，所述测试试样可取自所述在役聚乙烯管材不同的位置，以得到不同位置的测试试样的剩余使用寿命，从而使用户了解在役聚乙烯管材在不同位置的剩余使用寿命差异，以进行不同处理；或将不同位置的测试试样的应变硬化模量值＜G Pi’＞取均方根平均值，作为所述测试试样所在位置的整体应变硬化模量值＜G P’＞，以减少单一测试试样带来的偶然性误差。当然，亦可在所述在役聚乙烯管材的同一位置取材，制作成多片测试试样，以作为一组测试试样；并在另一位置亦取材，制作成多片测试试样，以作为另一组测试试样，以进一步提高测试的准确性。
根据所述测试方法，本申请还提出一种管材剩余使用寿命的测试系统，包括：
制样装置：用于从在役聚乙烯管材中获取测试试样；
拉伸测试装置：用于测量所述测试试样的应变硬化模量值＜G P'＞；
中央处理器：用于获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，所述至少三种聚乙烯材料为不同型号的聚乙烯材料；根据所述应变硬 化模量值＜G P＞与所述设计使用寿命T，构建函数：
T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n,其中，a 0、a 1、a 2……a n为预设系数，n为预设的所述函数最高次数，取正整数；将所述测试试样的应变硬化模量值＜G P'＞代入所述函数替换应变硬化模量值＜G P＞，算出使用寿命，所述使用寿命为所述测试试样的剩余使用寿命。
所述制样装置可以为现有的制样机，所述拉伸测试装置可为高温拉伸试验机。所述高温拉伸试验机可采用图2-图4所示的拉伸结构，包括：
机架1；
一对夹具2,即图中的第一夹具2A和第二夹具2B，第一夹具2A和第二夹具2B固定于机架1上，第一夹具2A和第二夹具2B上设置有用于夹持试样9一端的夹持槽，第一夹具2A和第二夹具2B的夹持槽开口方向相对，以分别夹持试样9的两端，将试样9固定；
移动装置3，至少一个夹具通过移动装置3固定于机架1上，以使其中一个夹具在远离或靠近另一个夹具的方向上移动；在图2中第一夹具2A通过移动装置3固定，移动装置3可带动第一夹具2A朝向图示中的上方或下方运动，以使第一夹具2A与第二夹具2B之间的距离增大或缩小，达到拉伸第一夹具2A与第二夹具2B之间的试样9的目的；
辅助锁紧装置，固定于夹具2上，所述辅助锁紧装置包括锁紧工位和避让工位，当所述辅助锁紧装置位于所述锁紧工位时，对所述夹持槽施加辅助夹紧力，以增加对试样9的夹持力，使试样9在拉伸过程中不易滑动或移位，增加拉伸测试的准确率；
测力装置4，与至少一个夹具连接，用于测量所述移动装置3移动时产生的拉伸力；以图2为例，由于试样9被夹持于第一夹具2A与第二夹具2B之间，当移动装置3带动第一夹具2A向上运动时，试样9将产生一定的阻力；当拉伸力超过所述阻力时，第一夹具2A与第二夹具2B之间的距离增大，试样9被拉长；所述测力装置4即用于测量试样9被拉长时的拉伸力；
测长装置，固定于机架1上，包括测量头，所述测量头的测量范围大于夹具2的移动范围，以测量夹具2移动过程中，试样9被拉长的实时长度。
使用时，所述辅助锁紧装置预先位于所述避让工位，以使试样9的两端分别插入第一夹具2A的夹持槽和第二夹具2B的夹持槽内并夹紧；夹紧后，所述辅助锁紧装置调整至所述锁紧工位，以增加对试样9的夹持力；再启动移动装置3，使移动装置3带动第一夹具2A朝远离第二夹具2B的方向移动，例如向图2中的上方运动，使试样9拉伸；在拉伸过程中，测力装置4测量拉伸试样9的拉伸力，测长装置测量试样9的实时拉伸长度；根据所述拉伸力与实施拉伸长度即可计算出前述的应变硬化模量值。本申请中的所述辅助锁紧装置可加强试样9与夹具2之间的摩擦力，以使试样9在拉伸过程中不易滑动，从而提高拉伸试验的精度，减少拉伸试样的失败概率。
参照图3和图4所示，每个夹具包括一对夹持面板21和中部开设有定位槽的固定座22，所述一对夹持面板21固定于所述定位槽相对的两侧；每个所述夹持面板21的一面为设有防滑纹的固定面，另一面为连接有螺杆的调节面；所述一对夹持面板21的固定面之间形成所述夹持槽，所述螺杆一端可转动地固定于所述调节面，另一端贯穿所述固定座且连接有调节旋钮23，所述螺杆的旋转轴与所述调节面垂直，以将调节旋钮23的转动转化为夹持面板21沿螺杆旋转轴方向的直线移动，以调整一对夹持面 板21之间的距离，从而夹持不同厚度的试样9；试验完成后，通过调节旋钮23增大夹持面板21之间的距离，也便于取出试样9。
两个夹具(第一夹具2A和第二夹具2B)上的调节旋钮23可设置于同一侧，以调整夹具2同一侧的夹持面板21，避免造成所述夹持槽的错位，确保夹持的试样9保持垂直或水平的位置，提高测试准确度；而且，亦便于在测试设备的一侧预留调节空间。
结合图4所示，所述辅助锁紧装置包括第一锁紧机构和第二锁紧机构；
每个夹持面板21的两侧分别设有卡槽211，所述锁第一锁紧机构和第二锁紧机构分别包括两条凸棱，所述两条凸棱分别与所述一对夹持面板21同侧的卡槽211相匹配；当所述辅助锁紧装置位于所述锁紧工位时，所述两条凸棱分别插入所述一对夹持面板21同侧的卡槽211内。
该实施例中的卡槽211和所述凸棱配合时，起到保持两个夹持面板21之间夹持力的作用；尤其是当所述锁第一锁紧机构和第二锁紧机构为可施加辅助夹紧力的机构时，每个锁紧机构的两条凸棱之间的距离可调，通过缩小所述两个凸棱之间的距离，可增加两个夹持面板21之间的夹持力，从而使夹持于两个夹持面板21之间的试样9不会滑移。
所述卡槽与所述凸棱的位置调换时，亦可起到同样的作用；即：所述辅助锁紧装置包括第一锁紧机构和第二锁紧机构；每个所述夹持面板21的两侧分别设有凸棱，所述锁第一锁紧机构和第二锁紧机构分别包括两条卡槽，所述两条卡槽分别与所述一对夹持面板21同侧的凸棱相匹配；当所述辅助锁紧装置位于所述锁紧工位时，所述一对夹持面板21同侧的凸棱分别插入所述两条卡槽内。当所述锁第一锁紧机构和第二锁紧机构为可施加辅助夹紧力的机构时，每个锁紧机构的两条卡槽之间的距离可调，通过缩小所述两个卡槽之间的距离，可增加两个夹持面板21之间的夹持力。
一对夹持面板21中的至少一个可设有凹部，所述凹部的形状可与夹持的试样9一端的形状一致，亦可局部形状的尺寸大于试样9一端的轮廓尺寸，只需所述凹部可卡住试样9不易滑移即可。
所述凹部可仅设于一个夹持面板21上；更佳地：所述一对夹持面板21上均设有所述凹部，所述凹部的深度小于试样9厚度的一半，即：所述试样9的厚度大于两个凹部的深度之和，以使两个夹持面板21的受力均衡，提高夹持的可靠性与夹持面板21的使用寿命。当两个夹持面板21上的所述凹部扣合并抵持于于试样9上时，两个夹持面板21之间仍有部分间隙，以便对所述试样9施加夹持力；而且该凹部还可对试样9起到定位作用，以使试样9夹持于最佳位置。根据试样9的厚度，所述凹部的深度可为0.1mm-3mm。
为进一步提升夹持效果，所述凹部表面设有防滑纹，以在拉伸试样9时，增加试样9与凹部之间的摩擦力，从而增大夹持力。
为便于夹持试样9，所述每个所述夹具2还包括试样定位装置，如图4所示，所述试样定位装置包括固定组件51和定位组件52，固定组件51固定于一个夹持面板21的侧面，定位组件52与夹持面板21垂直，且朝向于另一个夹持面板21。夹持试样9时，如图3所示，试样9的一侧可抵靠于定位组件52上，以将定位组件52作为试样9定位的参照物，使试样9夹持于合适的位置。所述固定组件51上可设置滑槽，以使所述试样定位装置可沿滑槽滑动，以调整定位组件52的位置，从而调整试样9的定位参考位置。
在另一实施例中，所述测长装置的测量头包括可与试样9待测长度一端对齐的第一测量杆61，与试样9待测长度另一端对齐的第二测量杆62；第一测量杆61与一个夹具同步运动，第二测量杆62与另一个夹具同步运动，以保证第一测量杆61与第二测量杆62之间的距离与试样9的长度同步。当然，所述夹具2中的一个或两个亦可为静止状态，则对应的第一测量杆61和/或第二测量杆62也是静止状态。本实施例中的两个测量杆可装设于机架1上，亦可装设于一滑轨8上，可随试样9的拉伸而分开，以实时标识试样9的拉伸长度。
更佳地，所述测量头包括非接触视频光学测量组件。非接触视频光学测量组件是用光学的方法测量目标构件或物体两点之间线变形的一种仪器，通常由照明场、相机和控制芯片三部分组成。通过相机直接记录变形过程，无需将测量的信号进行放大和数模转化处理，提高了测量速度和准确度，测量精度也较现有的伸长计高；而且，非接触式测量不会对试样造成任何伤害，从而避免了对拉伸测试的影响；测试过程中，也无需取下测量头，可全程跟踪试样的应变；也避免了现有拉伸设备中试样断裂时，导致伸长计掉落而摔坏的危险。
本申请中的一对夹具2,即图示的第一夹具2A和第二夹具2B，可上下设置，亦可左右设置，为避免重力对测试的影响，优选地第一夹具2A和第二夹具2B为上下设置。当所述一对夹具2为上下设置的上夹具与下夹具时，移动装置3固定于所述上夹具上方，如图2所示，所述测力装置4固定于所述下夹具底部，通过检测下夹具受到的拉伸力，得到拉伸试样9的拉伸力。
本申请中的拉伸测试装置还可包括加热装置7，以对试样9进行加热，提高高分子材料的活性，以得到不同参数条件下的拉伸测试结果。
以上所述仅是本申请的部分实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本申请的保护范围。

Claims (10)

  1. 一种管材剩余使用寿命的测试方法，其特征在于，包括：
    获取已知设计使用寿命T的至少三种聚乙烯材料各自对应的应变硬化模量值＜G P＞；
    根据所述应变硬化模量值＜G P＞与所述设计使用寿命T，构建函数：
    T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n，
    其中，a 0、a 1、a 2……a n为预设系数，n为预设的所述函数最高次数，取正整数；
    从在役聚乙烯管材中获取测试试样；
    测量所述测试试样的应变硬化模量值＜G P'＞；
    将所述测试试样的应变硬化模量值＜G P'＞代入所述函数替换应变硬化模量值＜G P＞，算出使用寿命，所述使用寿命为所述测试试样的剩余使用寿命。
  2. 根据权利要求1所述的测试方法，其特征在于，所述推算所述测试试样的剩余使用寿命之后，还包括：
    根据所述剩余使用寿命，判断是否更换所述在役聚乙烯管材。
  3. 根据权利要求2所述的测试方法，其特征在于，所述判断是否更换在役聚乙烯管材，包括：
    当所述剩余使用寿命不大于第一预设值，则更换所述在役聚乙烯管材；
    当所述剩余使用寿命大于所述第一预设值、小于第二预设值，则定期检测所述在役聚乙烯管材。
  4. 根据权利要求1所述的测试方法，其特征在于，所述获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，包括：
    制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样；
    通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞，其中，i为所述标准试样的编号；
    根据所述每片标准试样的应变硬化模量值＜G Pi＞，计算每种聚乙烯材料的应变硬化模量值的均方根平均值，将所述均方根平均值作为所述应变硬化模量值＜G P＞。
  5. 根据权利要求4所述的测试方法，其特征在于，所述制作所述至少三种聚乙烯材料的标准试样，每种聚乙烯材料至少制作五片标准试样,包括：
    在压模设备中制备出每种聚乙烯材料的所述至少五片标准试样，所述标准试样为哑铃状薄片，所述哑铃状薄片包括中部测试部分和两端夹持部分，所述哑铃状薄片的 厚度为0.3mm-1mm；
    将所述至少五片标准试样置于115℃-125℃的环境下退火一小时后，以小于2℃/min的冷却速度使试样冷却至室温。
  6. 根据权利要求5所述的测试方法，其特征在于，所述通过高温拉伸试验，得到每片所述标准试样的应变硬化模量值＜G Pi＞,包括：
    将所述哑铃状薄片置于80℃的恒温箱中放置30min-60min；
    将所述两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；
    以20mm/min的恒定移动速度拉伸所述哑铃状薄片，收集所述中部测试部分的拉伸比λ在8-12之间的数据值，所述拉伸比
    Figure PCTCN2018101826-appb-100001
    其中L 0为所述中部测试部分的初始长度，L为所述中部测试部分拉伸后的长度；
    记录所述拉伸比λ和所述拉伸过程中真应力σ true的对应关系：
    Figure PCTCN2018101826-appb-100002
    其中,F为与所述拉伸比的数据值对应的拉伸力，A 0为所述哑铃状薄片中部测试部分的初始横截面积；
    根据Neo-Hookean本构模型，以及λ＝12与λ＝8时，所述对应关系的斜率K，确定每片所述标准试样的应变硬化模量值＜G Pi＞为：
    ＜G Pi＞＝20K。
  7. 根据权利要求5所述的测试方法，其特征在于，所述从在役聚乙烯管材中获取测试试样，包括：
    从所述在役聚乙烯管材中获取测试材料，将所述测试材料在制样机中加工为所述测试试样；
    所述测试试样为哑铃状薄片，所述哑铃状薄片包括中部测试部分和两端夹持部分的，所述哑铃状薄片的厚度为0.3mm-1mm。
  8. 根据权利要求7所述的测试方法，其特征在于，所述测量所述测试试样的应变硬化模量值＜G P'＞，包括：
    将所述测试试样置于80℃的恒温箱中放置30min-60min；
    将所述测试试样的两端夹持部分夹持于高温拉伸试验机上，以5mm/min的应变率施加0.4Mpa的预应力；
    以20mm/min的恒定移动速度拉伸所述测试试样，收集所述测试试样中部测试部分 的拉伸比λ’在8-12之间的数据值，所述拉伸比
    Figure PCTCN2018101826-appb-100003
    其中L 0’为所述测试试样中部测试部分的初始长度，L’为所述测试试样中部测试部分拉伸后的长度；
    记录所述拉伸比λ’和所述拉伸过程中真应力σ true’的对应关系：
    Figure PCTCN2018101826-appb-100004
    其中,F’为与所述拉伸比λ’的数据值对应的拉伸力，A 0’为所述测试试样中部测试部分的初始横截面积；
    根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值＜G P'＞为
    ＜G P'＞＝20K’。
  9. 根据权利要求8所述的测试方法，其特征在于，所述测试试样至少为两片；所述根据Neo-Hookean本构模型，以及λ’＝12与λ’＝8时，所述对应关系的斜率K’，确定所述测试试样的应变硬化模量值＜G P'＞，包括：
    确定每一片所述测试试样的应变硬化模量值＜G Pi'＞；
    计算所述应变硬化模量值＜G Pi'＞的均方根平均值，将所述均方根平均值作为所述测试试样的应变硬化模量值＜G P'＞。
  10. 一种管材剩余使用寿命的测试系统，其特征在于，包括：
    制样装置：用于从在役聚乙烯管材中获取测试试样；
    拉伸测试装置：用于测量所述测试试样的应变硬化模量值＜G P'＞；
    中央处理器：用于获取已知设计使用寿命T的至少三种聚乙烯材料的应变硬化模量值＜G P＞，所述至少三种聚乙烯材料为不同型号的聚乙烯材料；根据所述应变硬化模量值＜G P＞与所述设计使用寿命T，构建函数：
    T＝a 0+a 1×＜G p＞+a 2×＜G p＞ 2+......+a n×＜G p＞ n,其中，a 0、a 1、a 2……a n为预设系数，n为预设的函数最高次数，取正整数；将所述测试试样的应变硬化模量值＜G P'＞代入所述函数替换应变硬化模量值＜G P＞，算出使用寿命，所述使用寿命为所述测试试样的剩余使用寿命。
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