CN110082201B - Material delayed fracture test method under high-pressure hydrogen-doped natural gas environment - Google Patents

Material delayed fracture test method under high-pressure hydrogen-doped natural gas environment Download PDF

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CN110082201B
CN110082201B CN201910302864.1A CN201910302864A CN110082201B CN 110082201 B CN110082201 B CN 110082201B CN 201910302864 A CN201910302864 A CN 201910302864A CN 110082201 B CN110082201 B CN 110082201B
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pressure
test
hydrogen
environment box
buffer tank
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CN110082201A (en
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郑津洋
尚娟
花争立
顾超华
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02Details
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02Column chromatography
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014Type of force applied
    • G01N2203/0016Tensile or compressive
    • G01N2203/0019Compressive
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058Kind of property studied
    • G01N2203/006Crack, flaws, fracture or rupture
    • G01N2203/0067Fracture or rupture
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02Details not specific for a particular testing method
    • G01N2203/022Environment of the test
    • G01N2203/023Pressure
    • G01N2203/0232High pressure
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02Details not specific for a particular testing method
    • G01N2203/022Environment of the test
    • G01N2203/0236Other environments

Abstract

The invention relates to a material mechanical property testing technology, and aims to provide a material delayed fracture testing method in a high-pressure hydrogen-doped natural gas environment. The loading shaft pushes the steel ball to apply load to the disc sheet sample, and the other side of the disc sheet sample is in contact with the high-pressure hydrogen-doped natural gas, so that the disc sheet sample is under the action of the load while in contact with the high-pressure hydrogen-doped natural gas, and data obtained by developing a delayed fracture test can be used for evaluating the performance damage of the material in the high-pressure hydrogen-doped natural gas environment. The invention avoids a complex servo test mechanism, reduces the volume of the equipment and reduces the cost; the probability of hydrogen leakage is reduced, and the reliability and safety of the device are improved; the test time is shortened, and the test efficiency is improved; the requirement of test temperature is met, and the influence of temperature on hydrogen embrittlement is tested; the accurate proportion of the hydrogen/natural gas mixed gas is realized; and the hydrogen leakage detection is carried out by using the hydrogen concentration detection device, so that whether the disc sheet sample is broken or not is conveniently judged.

Description

Material delayed fracture test method under high-pressure hydrogen-doped natural gas environment
Technical Field
The invention belongs to a material mechanical property testing technology, and particularly relates to a material delayed fracture testing method in a high-pressure hydrogen-doped natural gas environment.
Background
With the continuous optimization of energy structures in China, renewable energy is developed rapidly. Although renewable energy represented by wind energy and solar energy is rapidly developed, the time intermittency and unpredictability of wind/light power generation limit the large-scale integration of wind/light power generation into a main power grid, and particularly, the imbalance of the distribution of wind/light geographic resources in China causes the separation of a power generation center and a load center, so that serious 'wind abandon and electricity limitation' is caused to the large-scale application of the wind/light power generation. According to statistics of the national energy agency, in 2017 years, the wind and the photoelectric energy abandoned in China are up to 419 hundred million kW.h, and the wind abandoning rate exceeds 12%. The method is characterized in that redundant wind power or photoelectricity is electrolyzed to produce hydrogen, the produced hydrogen is doped into natural gas to form hydrogen-doped natural gas (HCNG), then the HCNG is conveyed by utilizing the existing natural gas pipe network and finally used as traffic fuel, power generation fuel and clean fuel gas, the method is considered to be an effective way for solving the problem of large-scale wind/photoelectricity absorption, can bring good environmental benefit while improving the utilization rate of renewable energy, and has wide application prospect. However, unlike the physical and chemical properties of natural gas, high-pressure hydrogen gas deteriorates the mechanical properties of metal materials, causing hydrogen damage to the materials. In order to ensure the safety of pipeline transportation of the hydrogen-doped natural gas, the material for the high-pressure hydrogen-doped natural gas environment must be subjected to experimental study on performance damage.
For the research on the material performance damage of the high-pressure hydrogen-doped natural gas environment, the performance test of the material should be carried out in the real high-pressure hydrogen-doped natural gas environment. This places high demands on the corresponding test apparatus. At present, corresponding test devices are lacked at home and abroad. Only a few research institutions developed devices for testing the mechanical properties of pure hydrogen environment materials in the early period, but all the devices have the following key problems:
(1) the equipment structure is complex, and potential safety hazard exists
Present pure hydrogen environment material mechanical properties testing arrangement is mostly reformed transform by traditional material testing machine and comes, installs the environment case that can provide experimental required pure hydrogen environment promptly on traditional material testing machine, for holding sample and anchor clamps thereof, the volume of environment incasement portion is designed great usually, and then leads to environment box volume and wall thickness great, and equipment overall structure is more complicated, and the cost is expensive. It is many to store inflammable and explosive medium in the environment case to current device is all by the loading axle that runs through testing machine environment case to come to exert load to the sample of clamping, and the pressure of seal structure in order to maintain the proof box inside is moved to the design often between loading axle and the environment case contact surface, nevertheless, moves seal structure life and is limited, easily causes the medium to leak, has great potential safety hazard.
(2) Low testing efficiency and high time cost
The existing high-pressure hydrogen-doped natural gas environmental material performance damage device is slow in applying pressure load to a clamped sample, and the force application frequency of a loading shaft is low, so that the test time cost is high, multiple operators are needed in each test, and the test labor cost is high.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a material delayed fracture test method in a high-pressure hydrogen-doped natural gas environment.
In order to solve the key problem, the solution of the invention is as follows:
the method for testing the delayed fracture of the material in the high-pressure hydrogen-doped natural gas environment comprises the following steps:
(1) device for evaluating material performance damage of high-pressure hydrogen-doped natural gas environment
Respectively connecting a natural gas cylinder group, a hydrogen cylinder group and an argon cylinder group to a low-pressure buffer tank and a test environment box through pipelines, respectively connecting the outlet of the low-pressure buffer tank to a chromatographic analyzer and a pneumatic booster pump through pipelines, connecting the outlet of the pneumatic booster pump to a high-pressure buffer tank, and connecting the outlet of the high-pressure buffer tank to the test environment box through a pipeline; the outlets of the high-pressure buffer tank, the test environment box and the chromatographic analyzer are also connected to a vacuum pump and an emptying pipeline through pipelines;
a test environment box and a vertical loading shaft are arranged on the rack; the test environment box consists of an upper environment box body and a lower environment box body, and the upper environment box body and the lower environment box body are positioned through a concave-convex groove and are connected through a bolt; a vertical cavity channel is arranged in the center of the upper environment box body, the lower end of the vertical loading shaft is inserted into the vertical cavity channel, and the vertical loading shaft are in clearance fit; a counter bore with similar radial dimension is arranged at the center of the lower environmental box body and corresponds to the cavity channel, and a recessed part for placing a sheet sample is arranged at the upper edge of the counter bore; the side wall of the lower environment box body is provided with an air inlet and outlet port and a stress sheet lead interface which are respectively connected to the bottom of the counter bore through an air inlet and outlet channel and a lead channel; one end of the stress sheet lead is connected with the bidirectional strain sheet, and the other end of the stress sheet lead is led out by a lead sealing device arranged in the lead channel; the test environment box is connected with the gas path system through the gas inlet and outlet;
(2) separating an upper environment box body and a lower environment box body, arranging a bidirectional strain gauge in the center of the lower surface of a disc sheet-shaped sample, putting the sample into a sunken part at the upper edge of a counter bore of the lower environment box body, and arranging a lead sealing device; aligning the concave-convex grooves of the upper environment box body and the lower environment box body, jointing the upper environment box body and the lower environment box body, and connecting by using bolts;
(3) placing a steel ball in the center of the upper surface of the sample, wherein the steel ball is positioned in a cavity channel of the upper environment box body; the loading shaft is lowered to a place slightly higher than the steel ball;
the heat medium is made to flow into the heat exchange jacket from the heat medium inflow pipeline by the refrigerating and heating machine, and then returns to the refrigerating and heating machine from the heat medium return pipeline and keeps circulating flow, so that the temperature of the test environment box is ensured to be constant in the test process and the test temperature requirement is met;
(4) partial pressure formula in dalton's partial pressure law: pB=PGeneral assemblyVB/VGeneral assemblyThe partial pressure of component gas B is equal to the product of the total gas pressure and the volume fraction of component gas B; calculating the pressure required by the hydrogen by using a Dalton partial pressure formula and the ratio of the total pressure of the hydrogen in the test condition, then pumping out residual air in the test device and an auxiliary pipeline by using a vacuum pump until the vacuum degree in the system reaches a set value, filling the hydrogen into the low-pressure buffer tank, filling natural gas into the low-pressure buffer tank after the pressure of the hydrogen in the low-pressure buffer tank reaches the set value, and ending the gas filling until the pressure of the natural gas/hydrogen mixed gas in the low-pressure buffer tank reaches the set value; opening a pressure reducing valve connected with the low-pressure buffer tank, measuring the content of each component of the mixed gas in the low-pressure buffer tank by using a chromatographic analyzer, and performing the next step if the content of the hydrogen and the natural gas obtained by measurement meets the test conditions; if the test conditions are not met, correspondingly adjusting according to the measurement result until the measured contents of the hydrogen and the natural gas meet the test conditions;
(5) filling high-pressure hydrogen/natural gas mixture into the high-pressure buffer tank by using a pneumatic booster pump until the pressure in the high-pressure buffer tank reaches a set value; the mixed gas in the high-pressure buffer tank enters the test environment box under the control of a valve until the air pressure in the test environment box reaches a set value P1Lowering the loading shaft, and applying a load to the disc sheet sample by applying force to the steel ball until the reading of the bidirectional strain gauge is the yield strength Q of the material for manufacturing the disc sheet sample in the air;
(6) maintaining the pressure for 10 hours, and recording the reading of the bidirectional strain gauge in the test process; vacuumizing the test environment box and the accessory pipeline to a set vacuum degree by using a vacuum pump, and closing the vacuum pump; after the test environment box and the pipeline are replaced for a plurality of times by using argon, separating the upper environment box body and the lower environment box body, and taking out a sample; observing whether the sample has cracks or not, if so, finishing the test, and if not, performing the next step;
(7) repeating the steps (2) to (6) until the sample is cracked; wherein the set value of the air pressure in the test environment box is changed to be nP when the step (5) is repeated1And the magnitude of the load applied to the disc thin slice sample by the loading shaft is Q + (n-1) multiplied by 50; and (4) obtaining the test repetition number n when the final sample has cracks by means of repeated tests.
In the invention, an annular groove is arranged at the opposite joint of the upper environmental box body and the lower environmental box body, and an O-shaped ring is arranged in the annular groove to be used as a sealing element.
In the invention, O-shaped ring sealing elements are respectively arranged between the loading shaft and the contact surface of the cavity channel of the upper environment box body, between the sample and the contact surface of the upper environment box body and between the sample and the contact surface of the lower environment box body.
In the invention, the lower end part of the loading shaft is in an inverted V shape.
In the present invention, the sample is a disk-shaped sheet, and the recessed portion for placing the sample has a shape corresponding to the recessed portion.
In the invention, a valve is arranged on a pipeline between an outlet of the gas cylinder group and each device of the gas circuit system, and a pressure reducing valve is arranged on a pipeline between the low-pressure buffer tank and the chromatographic analyzer.
In the invention, a vertical channel is arranged at the center of the bottom of the counter bore, and the air inlet and outlet channel and the lead channel transversely penetrate through the lower environment box body and are connected to the bottom end of the vertical channel.
In the invention, the hydrogen concentration detector is arranged in a cavity channel of the upper environment box body, and the control system is respectively connected to the low-pressure buffer tank, the pneumatic booster pump, the high-pressure buffer tank, the refrigerating and heating machine and the hydrogen concentration detection device through signal wires.
Description of the inventive principles:
the disc-shaped sheet is used as a sample, a steel ball is placed on one side of the disc-shaped sheet sample, the steel ball is pushed by a loading shaft to apply a load to the disc-shaped sheet sample, and the other side of the disc-shaped sheet sample is in contact with high-pressure hydrogen-doped natural gas, so that the disc-shaped sheet sample is under the load effect while being in contact with the high-pressure hydrogen-doped natural gas. The device can be used for developing a delayed fracture test, a certain load is applied to the disc sheet sample, the pressure of the hydrogen-doped natural gas in contact with the disc sheet sample is kept unchanged and is kept for a period of time, if no crack occurs in the disc sheet sample, the test is carried out again, the load borne by the disc sheet sample and the pressure of the hydrogen-doped natural gas in contact with the disc sheet sample are increased, and the process is repeated until the disc sheet sample cracks. The obtained data can be used for evaluating the performance damage of the material in the high-pressure hydrogen-doped natural gas environment.
Compared with the prior art, the invention has the beneficial effects that:
1. the method of applying load to the disc sheet sample by pushing the steel ball by the loading shaft avoids a complex servo test mechanism, the equipment body is actively and greatly reduced, and the equipment cost is reduced;
2. the device avoids using a high-pressure dynamic sealing element, so that the probability of hydrogen leakage can be reduced, and the reliability and safety of the device are improved;
3. the failure and the breakage of the disc sheet sample can be accelerated by improving the constant strain rate of the loading shaft during single loading, and the fatigue and the failure of the disc sheet sample can be accelerated by increasing the force application frequency of the loading shaft, so that the test time can be shortened, and the test efficiency can be greatly improved;
4. the temperature of the heating medium is controlled by the refrigerating and heating machine, so that the temperature in the test process is kept constant, the test temperature requirement is met, and meanwhile, the influence of the temperature on hydrogen embrittlement can be tested;
5. the measurement of the content of each component in the hydrogen/natural gas mixed gas can be analyzed by using a chromatographic analyzer, so that the content of each component in the mixed gas is adjusted, and the accurate proportion of the hydrogen/natural gas mixed gas can be realized;
6. the hydrogen concentration detection device can be used for detecting hydrogen leakage in a closed space formed by the upper environment box body, the disc sheet sample and the loading shaft, and whether the disc sheet sample is broken or not can be conveniently judged.
Drawings
FIG. 1 is a schematic view of the overall apparatus of the present invention;
FIG. 2 is a view showing the construction of the test environment chamber and the internal structure thereof according to the present invention.
In the figure: the device comprises a natural gas cylinder group 1, a hydrogen cylinder group 2, a low-pressure buffer tank 3, a pressure reducing valve 4, a chromatographic analyzer 5, a pneumatic booster pump 6, a high-pressure buffer tank 7, an air release valve 8, an air release pipeline 9, a vacuum pump valve 10, a vacuum pump 11, a loading shaft 12, an upper environment box 13, a lower environment box 14, a refrigerating and heating machine 15, a branch air release valve 16, a flow control valve 17, a high-pressure buffer tank outlet valve 18, a control system 19, a replacement pipeline 20, an argon cylinder group 21, a heat medium inflow pipeline 22, a heat medium 23, an O-shaped ring sealing element 24, an upper heat exchange jacket 25, a lower heat exchange jacket 26, a heat medium return pipeline 27, a steel ball 28, a bidirectional strain gauge 29, a lead sealing device 30, a bolt 31, an air inlet and outlet 32, a hydrogen concentration detection device 33 and a.
Detailed Description
Fig. 1 and 2 show the apparatus for evaluating the environmental material performance damage of the natural gas loaded with hydrogen used in this embodiment, which includes a natural gas cylinder group 1 for supplying natural gas for test, a hydrogen cylinder group 2 for supplying hydrogen for test, and an argon cylinder group 21 for replacement, wherein the exhaust ports of the natural gas cylinder group 1 and the hydrogen cylinder group 2 are connected to a low-pressure buffer tank 3, and the exhaust port of the low-pressure buffer tank 3 is divided into two paths: one path is connected to a pneumatic booster pump 6, and then a high-pressure buffer tank 7, and an exhaust port of the high-pressure buffer tank 7 is communicated to an air inlet (exhaust) port 32 of the lower environment tank body on the lower environment tank body 14; one path is connected to a pressure reducing valve 4 followed by a chromatograph 5. The content of each component in the hydrogen/natural gas mixed gas can be measured by using the chromatographic analyzer 5, and then the content ratio of each component in the mixed gas is adjusted, so that the accurate ratio of the hydrogen/natural gas mixed gas is realized. The pipeline is provided with a flow control valve 17, a replacement pipeline 20, a refrigerating and heating machine 15, a vacuum pump 11 and the like, wherein the flow control valve 17 is used for controlling the charging and discharging rate of the hydrogen/natural gas mixture; the replacement pipeline 20 specially used for gas replacement is connected with the argon bottle group 21 and the gas inlet (outlet) port 32 of the lower environmental box body, so that the lower environmental box body 14 can be directly purged by argon gas, and the purpose of gas replacement is achieved; the air inlet (outlet) 32 of the lower environment box body is provided with an emptying pipeline 9 which is directly connected to the low-pressure buffer tank 3, the high-pressure buffer tank 7 and the vacuum pump 11, the vacuum pump 11 is started, valves on connecting pipelines of the low-pressure buffer tank 3, the high-pressure buffer tank 7, the air inlet (outlet) 32 of the lower environment box body and the vacuum pump 11 are opened, and air in the low-pressure buffer tank 3, the high-pressure buffer tank 7 and the lower environment box body 14 can be emptied. The entire system is controlled by a control system 19.
As an application example: the upper environment casing 13 and the lower environment casing 14 are made of precipitation hardening stainless steel having good hydrogen embrittlement resistance, and the steel ball 28 is made of high-strength steel. Diameter D of the loading shaftJDiameter D of cavity channel with upper environment box 13kThe diameter of the steel ball 28 is 50-80 mm, the steel ball and the loading shaft are in clearance fit, the end part of the loading shaft is in an inverted V shape, the angle of two inclined edges is 60-80 degrees, and correspondingly, the diameter of the steel ball is 30-60 mm. The thickness of the disc sheet sample 34 is 0.5-2 mm, and the diameter D of the disc sheet sample 34Y=DK+30mm, and the adjustable temperature range of the heat medium in the refrigerating and heating machine 15 is-80-150 ℃. The loading shaft of the tester has a slow strain rate single-loading function, and the lowest strain loading rate is 10-7And/s, the loading shaft also has a reciprocating fatigue function, and the maximum fatigue frequency is 10 Hz. The inflation pressure range in the low-pressure buffer tank 3 is 0-60 MPa, and the inflation pressure range in the high-pressure buffer tank 7 is 50-120 MPa.
As shown in fig. 2, the test environment box of the testing machine is composed of an upper environment box body 13 and a lower environment box body 14, wherein the upper environment box body 13 and the lower environment box body 14 are made of precipitation hardening type stainless steel with good hydrogen embrittlement resistance, so as to ensure the service life and reliability of the test environment box; the upper environment box body 13 and the lower environment box body 14 are positioned through a concave-convex groove and connected through bolts 31, and the connection position is sealed through an O-shaped ring sealing element 24; loadingDiameter D of shaft 12JDiameter D of cavity channel with upper environment box 13kThe thickness of the loading shaft 12 is 50-80 mm, the loading shaft and the loading shaft are in clearance fit, the end part of the loading shaft is inverted V-shaped, and the angle of two inclined edges is 60-80 degrees; the disc sheet sample 34 has a thickness of 0.5 to 2mm and a diameter DY=DK+30 mm; before the test is started, the bidirectional strain gauge 29 can be installed at the center of the lower surface of the disc thin sheet sample 34, after the lead sealing device 30 is arranged, the disc thin sheet sample 34 is installed in a groove of the lower environment box 14 to measure the corresponding strain parameter change of the disc thin sheet sample 34 in the test process, and the corresponding displacement parameter change data of the disc thin sheet sample 34 in the test process can be obtained by monitoring the loading shaft 12 through the control system 19; the steel ball 28 is arranged on the upper surface of the disc sheet sample 34, the steel ball 28 is made of high-strength steel in a cavity channel of the upper environment box body 13, so that the steel ball can bear the load applied by the loading shaft 12 and further can apply enough pressure on the disc sheet sample 34, the diameter range of the steel ball 28 is 30-60 mm, and convenience in replacement is guaranteed; o-ring sealing elements 24 are arranged between the loading shaft 12 and the upper environment box body 13, between the disc sheet sample 34 and the upper environment box body 13 and between the disc sheet sample 34 and the lower environment box body 14 for sealing; the refrigeration and heating machine 15 is connected with the heat medium inflow pipeline 22 and the heat medium return pipeline 27, and the temperature of the heat medium 23 is controlled to control the test gas within the temperature range required by the test; a hydrogen concentration detection device 33 for performing hydrogen leakage detection to determine whether the disc sheet sample 34 is broken is disposed in the closed space formed by the upper environment casing 13, the disc sheet sample 34 and the loading shaft 12.
The delayed fracture test method by using the device for evaluating the material performance damage of the hydrogen-doped natural gas environment comprises the following steps:
firstly, the loading shaft 12 is lowered to a position higher than the upper environment box 13, the upper environment box 13 and the lower environment box 14 are separated, after the bidirectional strain gauge 29 is arranged at the center of the lower surface of the disc sheet sample 34, the disc sheet sample 34 provided with the bidirectional strain gauge 29 is placed in a groove of the lower environment box 14, after the lead sealing device 30 is arranged, the groove and the groove of the upper environment box 13 and the groove of the lower environment box 14 are respectively aligned, and the upper ring is arrangedThe environment box body 13 and the lower environment box body 14 are jointed and connected by a bolt 31; the loading shaft 12 is lowered to a position slightly higher than the steel ball 28, a closed test cavity is constructed, a heating medium 23 with a certain temperature flows into the upper heat exchange jacket 25 and the lower heat exchange jacket 26 from the heating medium inflow pipeline 22 by using the refrigeration and heating machine 15 and is filled, then the heating medium returns to the refrigeration and heating machine 15 from the heating medium return pipeline 27, and the operation is repeated in a circulating mode until the test is finished so as to ensure that the temperature in the test process is kept constant and meet the test temperature requirement; then, the partial pressure formula in the dalton partial pressure law is used: pB=PGeneral assemblyVB/VGeneral assemblyAnd calculating the pressure required by the hydrogen according to the proportion of the total pressure of the hydrogen in the test condition, pumping out residual air in the test device and an auxiliary pipeline by using a vacuum pump 11 until the vacuum degree in the system reaches a set value, filling the hydrogen into the low-pressure buffer tank 3, filling natural gas into the low-pressure buffer tank 3 after the pressure of the hydrogen in the low-pressure buffer tank 3 reaches the set value, ending the gas filling until the pressure of the natural gas/hydrogen mixed gas in the low-pressure buffer tank 3 reaches the set value, opening a pressure reducing valve 4 connected with the low-pressure buffer tank 3, measuring the content of each component of the mixed gas in the low-pressure buffer tank 3 by using a chromatographic analyzer 5, if the measured content of the hydrogen and the measured natural gas meets the test condition, performing the next step, and if the test condition is not met, performing corresponding adjustment according to the measurement result until the measured content of the hydrogen is, The natural gas content meets the test conditions; filling high-pressure hydrogen/natural gas mixture into the high-pressure buffer tank 7 by using the pneumatic booster pump 6 until the pressure of the hydrogen/natural gas mixture in the high-pressure buffer tank 7 reaches a set value, opening the flow control valve 17 and the outlet valve 18 of the high-pressure buffer tank, ensuring that the branch vent valve 16 is closed, and enabling the hydrogen/natural gas mixture in the high-pressure buffer tank 3 to enter the lower environment box body 14 at a specific speed until the pressure in the test environment box body reaches a test set value P1Lowering the loading shaft 12 to apply a load to the disc sheet sample 34 by applying a force to the steel ball 28 until the bi-directional strain gage 29 reads the yield strength Q of the material from which the disc sheet sample 34 is made in air; the pressure was maintained for 10h and testedRecording the reading of the bidirectional strain gauge 29 in the process, vacuumizing the lower environmental box 14 and the attached pipelines thereof to a set vacuum degree by using the vacuum pump 11, and then closing the vacuum pump 11; after the hydrogen/natural gas mixture in the test environment box and the pipeline is replaced for a plurality of times through the replacement pipeline 20 by using argon, the upper environment box body 13 and the lower environment box body 14 are separated, the disc sheet sample 34 is taken out, whether cracks appear in the disc sheet sample 34 is observed, if the cracks appear, the test is finished, and if the cracks do not appear, the pressure setting value in the test environment box is adjusted to be nP1The loading shaft 12 applies a load to the disc sheet specimen 34 of Q + (n-1) × 50, where n is the number of test repetitions, e.g., if a second test is required, the set pressure in the test environment chamber is 2P1The loading shaft 12 applies a load Q +50 to the disc thin sheet sample 34; the test was repeated until the disc sheet specimen 34 cracked. And (4) obtaining the test repetition number n when the final sample has cracks by means of repeated tests.
As described above, the loading shaft 12 is used to apply force to the steel ball 28 at a set frequency so as to apply a load with a certain frequency to the disc sheet sample 34, thereby avoiding a complicated servo test mechanism, greatly reducing the weight and volume of the equipment, reducing the cost, improving the test efficiency, and reducing the consumption of hydrogen/natural gas in the test; all sealing elements in the device are static sealing O-shaped ring sealing elements 24, so that the use of high-pressure dynamic sealing elements is avoided, the probability of hydrogen leakage can be reduced, and the reliability and safety of the device are improved; the hydrogen concentration detection device 33, the strain test device 29 and the displacement monitoring device, namely the control system 19 in the device are not influenced by high-pressure hydrogen/natural gas, and signals are stable; the temperature of the heating medium 23 is controlled by the refrigerating and heating machine 15, so that the temperature in the test process is kept constant, the test temperature requirement is met, and meanwhile, the influence of the temperature on hydrogen embrittlement can be tested; the chromatographic analyzer 5 can be used for analyzing the measurement of the content of each component in the hydrogen/natural gas mixed gas, so that the content of each component in the mixed gas can be adjusted, and the accurate proportion of the hydrogen/natural gas mixed gas can be realized; the hydrogen concentration detection device 33 can detect hydrogen leakage in a closed space formed by the upper environment box 13, the disc sheet sample 34 and the loading shaft 12, and can conveniently judge whether the disc sheet sample 34 is broken.
Although the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention are still within the technical scope of the present invention, unless the content of the technical solution of the present invention is departed from.

Claims (8)

1. A material delayed fracture test method under a high-pressure hydrogen-doped natural gas environment is characterized by comprising the following steps:
(1) device for evaluating material performance damage of high-pressure hydrogen-doped natural gas environment
Respectively connecting a natural gas cylinder group, a hydrogen cylinder group and an argon cylinder group to a low-pressure buffer tank and a test environment box through pipelines, respectively connecting the outlet of the low-pressure buffer tank to a chromatographic analyzer and a pneumatic booster pump through pipelines, connecting the outlet of the pneumatic booster pump to a high-pressure buffer tank, and connecting the outlet of the high-pressure buffer tank to the test environment box through a pipeline; the outlets of the high-pressure buffer tank, the test environment box and the chromatographic analyzer are also connected to a vacuum pump and an emptying pipeline through pipelines;
a test environment box and a vertical loading shaft are arranged on the rack; the test environment box consists of an upper environment box body and a lower environment box body, and the upper environment box body and the lower environment box body are positioned through a concave-convex groove and are connected through a bolt; a vertical cavity channel is arranged in the center of the upper environment box body, the lower end of the vertical loading shaft is inserted into the vertical cavity channel, and the vertical loading shaft are in clearance fit; a counter bore with similar radial dimension is arranged at the center of the lower environmental box body and corresponds to the cavity channel, and a recessed part for placing a sheet sample is arranged at the upper edge of the counter bore; the side wall of the lower environment box body is provided with an air inlet and outlet port and a stress sheet lead interface which are respectively connected to the bottom of the counter bore through an air inlet and outlet channel and a lead channel; one end of the stress sheet lead is connected with the bidirectional strain sheet, and the other end of the stress sheet lead is led out by a lead sealing device arranged in the lead channel; the test environment box is connected with the gas path system through the gas inlet and outlet;
(2) separating an upper environment box body and a lower environment box body, arranging a bidirectional strain gauge in the center of the lower surface of a disc sheet-shaped sample, putting the sample into a sunken part at the upper edge of a counter bore of the lower environment box body, and arranging a lead sealing device; aligning the concave-convex grooves of the upper environment box body and the lower environment box body, jointing the upper environment box body and the lower environment box body, and connecting by using bolts;
(3) placing a steel ball in the center of the upper surface of the sample, wherein the steel ball is positioned in a cavity channel of the upper environment box body; the loading shaft is lowered to a place slightly higher than the steel ball;
the heat medium is made to flow into the heat exchange jacket from the heat medium inflow pipeline by the refrigerating and heating machine, and then returns to the refrigerating and heating machine from the heat medium return pipeline and keeps circulating flow, so that the temperature of the test environment box is ensured to be constant in the test process and the test temperature requirement is met;
(4) partial pressure formula in dalton's partial pressure law: pB=PGeneral assemblyVB/VGeneral assemblyThe partial pressure of component gas B is equal to the product of the total gas pressure and the volume fraction of component gas B; calculating the pressure required by the hydrogen by using a Dalton partial pressure formula and the ratio of the total pressure of the hydrogen in the test condition, then pumping out residual air in the test device and an auxiliary pipeline by using a vacuum pump until the vacuum degree in the system reaches a set value, filling the hydrogen into the low-pressure buffer tank, filling natural gas into the low-pressure buffer tank after the pressure of the hydrogen in the low-pressure buffer tank reaches the set value, and ending the gas filling until the pressure of the natural gas/hydrogen mixed gas in the low-pressure buffer tank reaches the set value; opening a pressure reducing valve connected with the low-pressure buffer tank, measuring the content of each component of the mixed gas in the low-pressure buffer tank by using a chromatographic analyzer, and performing the next step if the content of the hydrogen and the natural gas obtained by measurement meets the test conditions; if the test conditions are not satisfied,correspondingly adjusting according to the measurement result until the measured contents of the hydrogen and the natural gas meet the test conditions;
(5) filling high-pressure hydrogen/natural gas mixture into the high-pressure buffer tank by using a pneumatic booster pump until the pressure in the high-pressure buffer tank reaches a set value; the mixed gas in the high-pressure buffer tank enters the test environment box under the control of a valve until the air pressure in the test environment box reaches a set value P1Lowering the loading shaft, and applying a load to the disc sheet sample by applying force to the steel ball until the reading of the bidirectional strain gauge is the yield strength Q of the material for manufacturing the disc sheet sample in the air;
(6) maintaining the pressure for 10 hours, and recording the reading of the bidirectional strain gauge in the test process; vacuumizing the test environment box and the accessory pipeline to a set vacuum degree by using a vacuum pump, and closing the vacuum pump; after the test environment box and the pipeline are replaced for a plurality of times by using argon, separating the upper environment box body and the lower environment box body, and taking out a sample; observing whether the sample has cracks or not, if so, finishing the test, and if not, performing the next step;
(7) repeating the steps (2) to (6) until the sample is cracked; wherein the set value of the air pressure in the test environment box is changed to be nP when the step (5) is repeated1And the magnitude of the load applied to the disc thin slice sample by the loading shaft is Q + (n-1) multiplied by 50; and (4) obtaining the test repetition number n when the final sample has cracks by means of repeated tests.
2. A method according to claim 1, wherein an annular groove is provided at the opposing junction of the upper and lower environmental tanks, with an O-ring built in as a sealing element.
3. The method of claim 1, wherein O-ring sealing elements are disposed between the loading shaft and the upper environmental chamber cavity channel interface, between the test sample and the upper environmental chamber interface, and between the test sample and the lower environmental chamber interface, respectively.
4. The method of claim 1, wherein the lower end of the loading shaft is inverted V-shaped.
5. The method of claim 1, wherein the sample is a disk-shaped sheet, and the recessed portion for placing the sample has a shape corresponding to the recessed portion.
6. The method of claim 1, wherein a valve is provided in the line between the outlet of the gas cylinder group and the equipment in the gas circuit system, and a pressure reducing valve is provided in the line between the low pressure buffer tank and the chromatograph.
7. The method of claim 1, wherein a vertical channel is provided centrally in the bottom of the counterbore, and the air intake and exhaust channels and the lead channel pass laterally through the lower environmental chamber and are connected to the bottom end of the vertical channel.
8. The method as claimed in claim 1, wherein the hydrogen concentration detector is disposed in the cavity passage of the upper environmental chamber, and the control system is connected to the low pressure buffer tank, the pneumatic booster pump, the high pressure buffer tank, the refrigerating and heating machine, and the hydrogen concentration detecting device through signal lines, respectively.
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