Test system and test method

Abstract

To provide a test system that increases the accuracy of a characteristic value obtained in a test that is conducted in an environment in which the pressure is increased by gas.SOLUTION: A test system has a pressure vessel, clevises installed in the pressure vessel, pins, and a test piece. The clevises and test piece are provided with through holes, and are connected to each other by the pins that are inserted into the through holes. When the diameter of the through holes in the test piece is defined as D1, and the diameter of the pin in the connected state at a contact part with the test piece is defined as D2, the formula of D2 / D1≤0.80 is satisfied.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a test system and a test method. [Background technology]

[0002] Tests have been conducted to obtain various property values ​​in a high-pressure gas environment. For example, a fracture toughness test using a CT test piece in hydrogen gas can obtain a load-displacement curve in hydrogen gas.

[0003] Regarding test equipment used for testing in such high-pressure gas environments, for example, Patent Document 1 discloses a mechanical property test device in which a high-pressure vessel is composed of a cylindrical main body having an opening at least at one end and a lid that closes this opening in an openable and closable manner, the axial force applied to the lid when high-pressure gas is introduced into the high-pressure vessel is supported by a press frame that is capable of being attached and detached from the outside of the high-pressure vessel, the deformation amount of a test piece can be measured by an actuator that applies a load to a test piece fixed to the lid through a rod that passes through the lid, and the test piece can be freely attached and removed by detaching the press frame and opening the lid.

[0004] Patent Document 2 discloses a jig for a materials testing machine, which includes a materials testing jig body for applying a load from an actuator, and a pin for connecting a hole in the jig body with a hole in a specimen, and in which a coating layer of a polymeric material is formed on the outer surface of the pin at the contact portion between the pin and the hole in the specimen and at the contact portion between the pin and the hole in the jig body, in order to reduce generation of high frequency noise from the contact portions between the jig body and the specimen and the pin.

[0005] Patent Document 3 discloses a fracture toughness test jig in which pinholes are formed on both sides of a groove to which the compact test piece of the jig body is connected, through which load pins are inserted to connect the jig body and the compact test piece and apply a load to the compact test piece, and the pinhole surface with which the load pin contacts is made approximately flat so that the load pin can rotate relative to the pinhole during testing, and in which elastic support pieces are provided on the jig body to support the compact test piece approximately horizontally so that it does not tilt under its own weight.

[0006] Patent Document 4 discloses a high-temperature, high-pressure fracture toughness testing machine having a test piece storage section with a heating means, and a measurement section and a load section each extending to either side of the test piece storage section, the test piece storage section and the load section being configured so that a fluid is introduced continuously between them, the load section being made up of a piston and cylinder mechanism, the piston being connected to one end of the test piece and the other end being connected to the measurement section, and the piston being pressed by the atmospheric gas introduced into the test piece storage section to apply a load to the test piece.

[0007] Patent Document 5 discloses an elastic-plastic fracture toughness testing method in which a tensile load is applied to a test piece that has been subjected to fatigue pre-crack processing, the magnitude of the load is measured, the opening displacement or strain of a predetermined location on the test piece other than on the load line is measured, and the load is slightly unloaded at each of a plurality of levels of the opening displacement or strain of the predetermined location, and the compliance at each unloading point and the energy applied up to that point are calculated from the measurement results of the relationship between the load and the opening displacement or strain of the predetermined location, and the opening displacement on the load line of the test piece and the corresponding energy are estimated and calculated by conversion from the calculation results of each compliance and energy, and the relationship between the J-integral value and the crack extension amount, and ultimately the tensile limit J-integral value, are obtained from the relationship between the opening displacement on the load line and the corresponding energy.

[0008] Patent Document 6 discloses a mechanical property testing device that includes a high-pressure vessel into which high-pressure gas containing hydrogen gas is introduced, and a test load detection device that applies a load to a test piece for evaluating mechanical properties and has a load cell equipped with a strain gauge that detects the load applied to the test piece, in which the insulating layer of the strain gauge is made of ceramics. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2004-340920 A [Patent Document 2] Japanese Utility Model Application Publication No. 60-7066 [Patent Document 3] Japanese Utility Model Application Publication No. 61-112252 [Patent Document 4] Japanese Patent Application Publication No. 58-137735 [Patent Document 5] Japanese Patent Application Publication No. 2-40528 [Patent Document 6] JP 2006-349487 A Summary of the Invention [Problem to be solved by the invention]

[0010] Conventionally, in order to obtain various characteristic values ​​in a high-pressure gas environment, a test piece and a clevis are connected by inserting a pin into a through hole, and the connected test piece, clevis, and pin are placed in a pressure vessel, and various tests are performed after the pressure is increased by gas. However, in tests performed in an increased pressure environment, a load is sometimes applied to the test piece by the gas pressure, although the mechanism is not clear. And when a test is performed in a state where the test piece is loaded by the gas pressure, a load other than the actual test load is applied, which can result in poor accuracy of evaluation. Therefore, it is desirable to improve the accuracy of evaluations (i.e., obtained characteristic values) in tests carried out in a pressurized environment using gas.

[0011] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a test system and test method that improves the accuracy of characteristic values ​​obtained in tests performed in a gas-pressurized environment. [Means for solving the problem]

[0012] The present disclosure includes the following aspects. <1> A pressure vessel; a clevis, a pin, and a test piece installed in the pressure vessel; the clevis and the test piece are connected by the pin inserted into a through hole provided in each of the clevis and the test piece, A test system in which, when the diameter of the through hole of the test piece is D1 and the diameter of the contact portion of the pin with the test piece in a connected state is D2, the ratio of D1 to D2 satisfies the following formula 1. D2 / D1≦0.80...Equation 1 <2> When the diameter of the through hole of the clevis is D3 and the diameter of the pin at the contact portion with the clevis in a connected state is D4, the ratio of D3 to D4 satisfies the following formula 2, <1> 2. A test system as described in claim 1. D4 / D3≧0.90...Equation 2 <3> a step of connecting the clevis and the test piece by a pin inserted into a through hole provided in each of the clevis and the test piece; placing the coupled clevis, test specimen, and pin within a pressure vessel; and then conducting a test on the test piece after introducing a gas into the pressure vessel to increase the pressure, A test method in which, when the diameter of the through hole of the test piece is D1 and the diameter of the contact portion of the pin with the test piece in a connected state is D2, the ratio of D1 to D2 satisfies the following formula 1. D2 / D1≦0.80...Equation 1 <4> When the diameter of the through hole of the clevis is D3 and the diameter of the pin at the contact portion with the clevis in a connected state is D4, the ratio of D3 to D4 satisfies the following formula 2, <3> The test method described in. D4 / D3≧0.90...Equation 2 Effect of the Invention

[0013] According to the present disclosure, it is possible to provide a test system and a test method that improve the accuracy of characteristic values ​​obtained in tests performed in an environment pressurized by gas. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1(A) is a side view showing an example of a CT test piece used in a test system and a test method according to an embodiment of the present disclosure, and FIG. 1(B) is a top view of the CT test piece shown in FIG. 1(A). [Diagram 2] FIG. 1 is a cross-sectional view showing a state in which a CT test piece and a clevis are connected by a pin in a test system and a test method according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a side view illustrating an example of a pin used in a test system and a test method according to an embodiment of the present disclosure. [Figure 4] FIG. 13 is a side view showing another example of a pin used in the test system and test method according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 is a side view showing a pin used in Comparative Example 1. [Figure 6] 1 is a graph showing a load-opening displacement curve illustrating the relationship between the load and the opening displacement in a hydrogen gas environment and an air environment. [Figure 7] 1 is a graph showing the relationship between the elapsed time during pressure increase and the load applied to a CT test piece in Example 1 of the present invention. [Figure 8] 11 is a graph showing the relationship between the elapsed time during pressure increase and the load applied to a CT test piece in Example 2 of the present invention. [Figure 9]1 is a graph showing the relationship between the elapsed time during pressure increase and the load applied to a CT test piece in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described in detail.

[0016] In numerical ranges described in stages, the upper limit or lower limit value described in a certain numerical range may be replaced with the upper limit or lower limit value of another numerical range described in stages. In a numerical range, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. The term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0017] <Test system> A test system according to an embodiment of the present disclosure includes a pressure vessel, a clevis, a pin, and a test specimen that are installed in the pressure vessel. The clevis and the test specimen are connected to each other by a pin that is inserted into a through hole provided in each of the clevis and the test specimen. When the diameter of the through hole of the test specimen is D1 and the diameter of the pin at the contact portion with the test specimen in the connected state is D2, the ratio of D1 to D2 satisfies the following formula 1. D2 / D1≦0.80...Equation 1

[0018] The testing system according to the embodiment of the present disclosure is intended for testing steel for hydrogen pressure storage vessels or hydrogen line pipes, and examples of such testing include fracture toughness testing in a high-pressure hydrogen environment using CT (compact tension) test pieces of steel material.

[0019] According to the embodiments of the present disclosure, characteristic values ​​can be determined with high accuracy in tests carried out in an environment pressurized by gas.

[0020] In recent years, hydrogen pressure vessels used at hydrogen stations are required to have higher strength steel materials in order to handle higher pressure and larger capacity. However, there are concerns that the hydrogen embrittlement resistance of steel materials will decrease as the strength increases. In addition, there is a demand to evaluate whether steel materials for hydrogen line pipes are suitable for high-pressure hydrogen transport. In tests to obtain various property values ​​in high pressure gas, in addition to the operations performed in air, the gas introduced into the pressure vessel is pressurized to a specified test pressure. For example, the High Pressure Gas Safety Institute of Japan has established standards for fracture toughness tests performed in hydrogen gas using CT test pieces. In this standard, load is applied with stroke control to achieve a specified stress intensity factor increase rate, load-displacement curves of the CT test piece in air and hydrogen are obtained, and the load at the point where the load-displacement curve in hydrogen deviates from the load-displacement curve in air is used for evaluation.

[0021] However, in the conventional jig with the specified dimensions, a load was applied to the test piece when the gas pressure was increased from atmospheric pressure to the test pressure. Since a load different from the actual test load was applied, it became difficult to determine the linear relationship between the test load and the displacement, and the deviation point from the elastic deformation part in the load-displacement curve could not be accurately found, which resulted in poor accuracy in the evaluation of fracture toughness. Moreover, if the load applied to the test piece was too high, cracks were generated in the test piece, which further reduced the accuracy of the evaluation. The load on the test piece during the increase in gas pressure is not limited to the fracture toughness test in hydrogen gas using the CT test piece. In a test system having a pressure vessel, a clevis installed in the pressure vessel, a pin, and a test piece, in which the clevis and the test piece are connected by a pin inserted into a through hole provided in each, a load may be applied to the test piece in a test performed in an increased pressure environment, although the mechanism is not clear. When a test is performed in a state in which a load is applied to the test piece, a load other than the original test load is applied, and the accuracy of the evaluation may be poor. In addition, if the load applied to the test piece becomes too high, cracks may occur in the test piece, further reducing the accuracy of the evaluation.

[0022] In contrast, in the test system according to the embodiment of the present disclosure, the ratio of the diameter D1 of the through hole of the test piece to the diameter D2 of the pin at the contact portion with the test piece in the connected state satisfies the above formula 1 in the test piece and the pin used. In other words, by making the ratio of D2 / D1 0.80 or less, a gap is provided between the pin used for connecting to the clevis and the through hole of the test piece. This prevents a load from being applied to the test piece when the gas pressure is increased in the test. Therefore, a load other than the original test load is prevented from being applied to the test, and furthermore, the load applied to the test piece is prevented from increasing too much, which causes cracks in the test piece. As a result, the characteristic value can be obtained with high accuracy in the test.

[0023] A test system according to an embodiment of the present disclosure will be described in detail below.

[0024] (Example of test) First, a test using the test system according to the embodiment of the present disclosure will be specifically described with an example. The test system according to the embodiment of the present disclosure can be applied to, for example, a fracture toughness test under a high-pressure hydrogen environment using a CT test piece.

[0025] For fracture toughness testing in a high-pressure hydrogen environment using a CT specimen, a test system is used that includes a pressure vessel, a clevis installed in the pressure vessel, a pin, and a test specimen, with the clevis and the test specimen connected by a pin inserted into a through hole provided in each vessel. For example, the pressure vessel is an autoclave that can increase, hold, and reduce pressure. The clevis is connected to a testing machine that has an actuator and a load cell that can apply and measure loads. The strain of the test specimen is measured with a strain gauge. A clip gauge may be used to measure the strain of the test specimen.

[0026] -Connecting test pieces The test piece may be, for example, a CT test piece 6 shown in Fig. 1. Fig. 1(A) shows a side view of the CT test piece 6, and Fig. 1(B) shows a top view of the CT test piece 6 (i.e., a view seen from the left in Fig. 1(A)). As shown in Fig. 1(A), the CT test piece 6 has a contour close to a square, a notch 62 is formed at one end, and there are two through holes 60A, 60B, one on each side of the notch 62.

[0027] As the clevis, for example, two clevises 8A and 8B having through holes 80A and 80B for passing the pin 2 therethrough as shown in FIG. 2 are used.

[0028] Fig. 2 is a cross-sectional view showing a state in which a CT test piece and a clevis are connected by a pin. Fig. 2 is a cross-sectional view seen from the top side of the CT test piece 6 (i.e., the same side as Fig. 1(B)). Fig. 2 shows an embodiment in which a pin 2A having a shape shown in Fig. 3 described later is used as the pin 2.

[0029] As shown in FIG. 2, the CT specimen 6 and one clevis 8A are installed so that the through holes 80A and 80B of the clevis 8A overlap with one through hole 60A of the CT specimen 6. In addition, another clevis 8B is installed on the opposite side of the side where the clevis 8A of the CT specimen 6 is installed so that the through holes 80A and 80B of the clevis 8B overlap with the other through hole 60B of the CT specimen 6. Next, a pin 2 is inserted into the through hole 60A of the CT specimen 6 and the through holes 80A and 80B of the clevis 8A, and a pin 2 is inserted into the through hole 60B of the CT specimen 6 and the through holes 80A and 80B of the clevis 8B, and the CT specimen 6 and the two clevises 8A and 8B are connected by the two pins 2. A fatigue pre-crack may be introduced into the CT specimen.

[0030] Boosting voltage Next, the CT test specimen and the clevis connected by the pin are placed in a pressure vessel, and the pressure is increased to a predetermined pressure using gas. Note that, although hydrogen gas is used as the gas in this example, the test system according to the embodiment of the present disclosure is not limited to hydrogen gas, and can also be applied to tests in an environment where the pressure is increased using other gases. Gas may be introduced into the pressure vessel, and fatigue pre-cracks may be introduced into the CT test specimen before the pressure is increased.

[0031] Fracture toughness test Next, a fracture toughness test is performed in an environment where the pressure inside the pressure vessel is increased by gas. Two clevises 8A and 8B shown in FIG. 2 apply a tensile load applied by a testing machine (not shown) to a CT test piece 6 connected by a pin 2, and a curve showing the relationship between the load and the opening displacement (load-opening displacement curve) as shown in FIG. 6 is obtained. Then, the load at the point where the load-displacement curve in the pressurized hydrogen gas environment deviates from elastic deformation (fracture toughness evaluation load P in FIG. 6) is compared with the load-opening displacement curve in the atmospheric environment. D ) can be used to determine characteristic values ​​for fracture toughness.

[0032] It should be noted that the above example is an example in which a test system according to an embodiment of the present disclosure is applied to a fracture toughness test in a high-pressure hydrogen environment using a CT test piece, but the present disclosure is not limited to this example. For example, a test system according to an embodiment of the present disclosure can be applied to testing a gas environment containing a corrosive gas such as hydrogen sulfide.

[0033] The test subject, that is, the material of the test piece, may be, for example, steel material, aluminum alloy, copper alloy, etc.

[0034] In addition, the gas pressure (i.e., the maximum pressure after pressure is increased by gas) assumed when conducting a test in the test system according to an embodiment of the present disclosure is not particularly limited, but may be, for example, 10 MPa or more and 130 MPa or less.

[0035] (D2 / D1) In a test system according to an embodiment of the present disclosure, when the diameter of the through hole in the test piece is D1 and the diameter of the contact portion of the pin with the test piece in the connected state is D2, the ratio of D1 to D2 satisfies the following formula 1. D2 / D1≦0.80...Equation 1

[0036] The ratio of D2 / D1 is 0.80 or less, i.e., a gap is provided between the pin and the through hole of the test piece, which prevents the load from being applied to the test piece when the gas pressure is increased during the test, thereby enabling the characteristic values ​​to be obtained with high accuracy during the test.

[0037] The ratio of D1 to D2 (D2 / D1) is preferably 0.79 or less, and more preferably 0.75 or less, while the lower limit of the ratio (D2 / D1) is preferably 0.60 or more, and more preferably 0.70 or more, from the viewpoint of the strength of the pin.

[0038] (D4 / D3) In the test system according to the embodiment of the present disclosure, when the diameter of the through hole of the clevis is D3 and the diameter of the pin at the contact part with the clevis in the connected state is D4, if the ratio of D3 to D4 (D4 / D3) is 0.70 or more, the test can be performed stably, and may be 0.80 or more. It is preferable that the ratio of D3 to D4 is 0.90 or more, that is, the following formula 2 is satisfied. D4 / D3≧0.90...Equation 2

[0039] A ratio of D4 / D3 of 0.90 or more, i.e., a small gap between the pin and the clevis through hole, can provide greater stability when conducting the test.

[0040] From the viewpoint of further enhancing stability, the ratio of D3 to D4 (D4 / D3) is preferably 0.93 or more, and more preferably 0.95 or more. On the other hand, from the viewpoint of ease of insertion of the pin into the through hole of the clevis, the lower limit of the ratio (D4 / D3) is preferably 0.99 or less, and more preferably 0.97 or less.

[0041] In addition, examples of methods for controlling the ratio of D1 to D2 (D2 / D1) and the ratio of D3 to D4 (D4 / D3) within the above-mentioned ranges include the following method (1), the following method (2), or a combination of the following methods (1) and (2). (1) A method in which the size (diameter) of the through hole of the test piece and the through hole of the clevis are made different (2) The diameter of the pin is made different at the point where it contacts the test piece and at the point where it contacts the clevis when connected.

[0042] In the method (1) above, the size (diameter) of the through hole of the test piece and the through hole of the clevis are made different, so that the ratio (D2 / D1) and the ratio (D4 / D3) are controlled to be within the above ranges. Note that in the method (1) above, for example, a pin 2A having a shape in which the diameter D2 (diameter at the contact part with the test piece in a connected state) and the diameter D4 (diameter at the contact part with the clevis in a connected state) are the same as shown in Figure 3 can be used as the pin.

[0043] In the method (2) above, the diameter of the pin is made different between the portion that contacts the test piece when connected and the portion that contacts the clevis, thereby controlling the ratio (D2 / D1) and the ratio (D4 / D3) to be within the above ranges. An example of a pin used in the method (2) above is pin 2B, which has a constriction 20 in the region with diameter D2 (the diameter at the contact portion with the test piece in the connected state) as shown in Fig. 4, and has a shape in which diameter D2 and diameter D4 are different diameters.

[0044] However, when there are regulations such as CT test pieces, the size (diameter) of the through hole of the test piece and the through hole of the clevis may be specified, so in that case it is preferable to adopt the method (1) above. In many cases, D1, D2, D3, and D4 are written on the drawing used to prepare the test piece, clevis, and pin.

[0045] According to the testing system of the embodiment of the present disclosure, load on the test piece is suppressed in a test performed in a pressurized environment by gas, and as a result, characteristic values ​​can be obtained with high accuracy in the test. In addition, the load applied to the test piece as the pressure is increased by the gas is preferably, for example, 0 kN or more and 1.0 kN or less, and more preferably 0 kN or more and 0.5 kN or less, from the viewpoint of further increasing the accuracy of the characteristic values ​​obtained in the test.

[0046] <Test Method> A test method according to an embodiment of the present disclosure includes a step of connecting a clevis and a test piece with a pin inserted into a through hole provided in each of them (connecting step), a step of installing the connected clevis, test piece, and pin in a pressure vessel (installation step), and a step of introducing gas into the pressure vessel to increase the pressure and then performing a test on the test piece (testing step). The introduction of fatigue pre-cracks in the test piece may be performed in the atmosphere before being installed in the pressure vessel, or may be performed in the gas after the test piece is installed in the pressure vessel and gas is introduced therein before increasing the pressure.

[0047] ·Connection process In the connecting step, the clevis and the test piece are connected by a pin inserted into a through hole provided in each of them. An example of the method for connecting the clevis and the test piece by a pin is as described above in the section "Connecting the test piece", and a detailed description thereof will be omitted here.

[0048] ·Installation process In the installation process, the connected clevis, test piece, and pin are installed in a pressure vessel. A conventionally known vessel can be used as the pressure vessel. In addition, in the case of a test method specified in various standards, a pressure vessel conforming to the standards is used.

[0049] Testing process In the test process, a gas is introduced into a pressure vessel to increase the pressure, and then the test is performed on the test piece. The pressure increase by introducing gas into the pressure vessel and the test on the test piece are as described above in the sections "Pressure Increase" and "Fracture Toughness Test", and a detailed description thereof will be omitted here.

[0050] When the diameter of the through hole of the test piece is D1 and the diameter of the contact portion of the pin with the test piece in the connected state is D2, the ratio of D1 to D2 satisfies the following formula 1. D2 / D1≦0.80...Equation 1

[0051] According to the embodiment of the present disclosure, the ratio of D1 to D2 satisfies the following formula 1, so that the characteristic value can be determined with high accuracy in a test performed in an environment pressurized by gas. The more preferable range of the ratio (D2 / D1) is as described above.

[0052] In the test method according to an embodiment of the present disclosure, when the diameter of the through hole of the clevis is D3 and the diameter of the pin at the contact point with the clevis in the connected state is D4, it is preferable that the ratio of D3 to D4 satisfies the following formula 2. D4 / D3≧0.90...Equation 2

[0053] The ratio of D4 / D3 is 0.90 or more, i.e., the gap between the pin and the through hole of the clevis is small, which can improve the stability when conducting the test. The more preferable range of the ratio (D4 / D3) is as described above. The ratio (D4 / D3) may be 0.70 or more or 0.80 or more.

[0054] The test method according to the embodiment of the present disclosure targets tests performed on, for example, steel for hydrogen pressure storage vessels or steel for hydrogen line pipes, and examples of the tests include fracture toughness tests in a high-pressure hydrogen environment using CT (compact tension) test pieces of steel materials. EXAMPLES

[0055] The present disclosure will be described more specifically below with reference to examples, but the present disclosure is not limited to these examples.

[0056] Fracture toughness tests in hydrogen gas using CT test pieces were carried out using the three types of pins shown below.

[0057] <Pin preparation> The pins prepared were Example 1, Example 2, and Comparative Example 1, each of which had the following values ​​for diameter D2 at the contact point with the test piece when connected and diameter D4 at the contact point with the clevis when connected. (Example 1): As shown in FIG. 3, the pin 2A has a shape in which the diameter D2 and the diameter D4 are the same, D2=10 mm, D4=10 mm (Example 2): As shown in FIG. 4, the diameter D2 and the diameter D4 are different, and the pin 2B has a shape having a constriction 20 in the area of ​​the diameter D2, D2=10 mm, D4=12 mm. (Comparative Example 1): As shown in FIG. 5, the pin 2C has a shape in which the diameter D2 and the diameter D4 are the same, D2=12 mm, D4=12 mm In addition, in all of pin 2A of invention example 1, pin 2B of invention example 2, and pin 2C of comparative example 1, a clip insertion hole 4 is provided at the tip of the pin to prevent it from falling off.

[0058] <Preparation of CT Test Specimen and Clevis> As the test specimen, a CT test specimen 6 shown in Fig. 1 was prepared. The CT test specimen 6 has a contour close to a square as shown in Fig. 1(A), a notch 62 is formed at the end, and there are two through holes 60A and 60B, one on each side of the notch 62, for a total of two through holes. The diameters D1 of the through holes 60A and 60B are both 12.7 mm. The material of the CT test specimen 6 is JIS standard steel SNCM439.

[0059] Also, as the clevis, as shown in Fig. 2, two clevises 8A and 8B having through holes 80A and 80B for passing the pin 2 were prepared. The diameters D3 of the through holes 80A and 80B are both 12.5 mm.

[0060] <Connection of CT Test Specimen and Clevis by Pins> As shown in Fig. 2, the CT test specimen 6 and one clevis 8A were installed such that the through holes 80A and 80B of the clevis 8A overlap with one of the through holes 60A in the CT test specimen 6. Also, on the side of the CT test specimen 6 opposite to the side where the clevis 8A is installed, another clevis 8B was installed such that the through holes 80A and 80B of the clevis 8B overlap with the other through hole 60B in the CT test specimen 6. Then, the pin 2 was inserted into the through hole 60A of the CT test specimen 6 and the through holes 80A and 80B of the clevis 8A, and the pin 2 was inserted into the through hole 60B of the CT test specimen 6 and the through holes 80A and 80B of the clevis 8B, and the CT test specimen 6 and the two clevises 8A and 8B were connected by two pins 2. Note that Fig. 2 shows an embodiment in which the pin 2A (Fig. 3) having the shape of Invention Example 1 was used as the pin 2. The ratios of D2 / D1 and D4 / D3 in each invention example and comparative example are shown in Table 1 below.

[0061] <Pressure Increase and Fracture Toughness Test> · Pressure Increase In each of the invention examples and comparative examples, the CT test piece and the clevis connected by the pin were placed in a pressure vessel, and the pressure was increased to 85 MPa using hydrogen gas to confirm the behavior of the load applied to the CT test piece. When the pressure was increased, it was held for 5 minutes at 10 MPa from the viewpoint of leak checking, and then increased to 85 MPa.

[0062] The relationship between the elapsed time (seconds) during pressure increase and the load (kN) applied to the CT test piece in each of the invention examples and comparative examples is shown in the graphs of Figures 7, 8, and 9. The double-headed arrow for 10 MPa hold in the figures represents the hold time at 10 MPa, and the elapsed time up to the start point is the time required for the pressure to increase to 10 MPa. The double-headed arrow for 10M to 85 MPa rise in the figures represents the time required for the pressure to increase from 10 MPa to 85 MPa, and the end point indicates that 85 MPa was reached.

[0063] In Example 1, as shown in the graph of FIG. 7, no load was applied to the CT test piece due to the increase in pressure.

[0064] In Example 2, as shown in the graph of Figure 8, almost no load was applied to the CT test piece due to the pressure increase. It should be noted that at the point in time when about 1900 seconds had elapsed since the start of the pressure increase, that is, when the pressure had increased to 85 MPa, a load of about 0.4 kN was applied to the CT test piece. However, this load is presumably a slight load that occurred due to the way the pin, CT test piece, and clevis were installed, and it is presumably a load that can be eliminated by adjusting the way they were installed. Furthermore, the application of this slight load is not a problematic load when conducting a fracture toughness test.

[0065] In Comparative Example 1, as shown in the graph of Fig. 9, the load applied to the CT specimen increased as the pressure increased, and the load on the CT specimen reached nearly 10 kN during the pressure increase (i.e., before the pressure was increased to 85 MPa), at which point cracks occurred in the CT specimen. The load on the CT specimen suddenly dropped at about 1300 seconds elapsed, and cracks occurred in the CT specimen just before this. Therefore, in Comparative Example 1, the pressure could not be increased to 85 MPa, and the subsequent fracture toughness test could not be performed.

[0066] Fracture toughness test A fracture toughness test was conducted under a hydrogen gas pressure of 85 MPa for Example 1 and Example 2. In Fig. 2, a tensile load from a testing machine (not shown) was applied to a CT test piece 6 connected by a pin 2 through two clevises 8A and 8B, and a curve showing the relationship between the load and the opening displacement (load-opening displacement curve) was obtained. In both of the invention examples 1 and 2, the load on the test pieces due to gas pressure was zero or extremely small, and accurate characteristic values ​​for fracture toughness could be obtained.

[0067] [Table 1]

[0068] However, in Example 1, where D4 / D3 was less than 0.9, there was a difference in the stability of the test compared to Example 2, where D4 / D3 was 0.9 or more. Specifically, in Example 1, at the beginning of the tensile test, the through hole of the clevis and the pin engaged, and there was a slight time lag between the load applied by the testing machine being transmitted to the test piece through the pin. [Explanation of symbols]

[0069] Pins 2A, 2B, 2C 4 Clip insertion hole 6 CT test specimen 8A, 8B, Clevis 20 Waistline 60A, 60B through hole 62 Notch 80A, 80B through hole

Claims

1. A pressure vessel; a clevis, a pin, and a test piece installed in the pressure vessel; the clevis and the test piece are connected by the pin inserted into a through hole provided in each of the clevis and the test piece, The diameter of the through hole of the test piece is D １ and the diameter of the pin at the contact portion with the test piece in the connected state is D ２ When the above D １ and the above D ２ The test system, wherein the ratio of D ２ / D １ ≦0.80 ・・・Formula 1

2. The diameter of the through hole of the clevis is D ３ and the diameter of the pin at the contact portion with the clevis in the connected state is D ４ When the above D ３ and the above D ４ The test system of claim 1 , wherein the ratio of D ４ / D ３ ≧0.90 ・・・Formula 2

3. a step of connecting the clevis and the test piece by a pin inserted into a through hole provided in each of the clevis and the test piece; placing the coupled clevis, test specimen, and pin within a pressure vessel; and then conducting a test on the test piece after introducing a gas into the pressure vessel to increase the pressure, The diameter of the through hole of the test piece is D １ and the diameter of the pin at the contact portion with the test piece in the connected state is D ２ When the above D １ and the above D ２ The ratio of D ２ / D １ ≦0.80 ・・・Formula 1

4. The diameter of the through hole of the clevis is D ３ and the diameter of the pin at the contact portion with the clevis in the connected state is D ４ When the above D ３ and the above D ４ The test method according to claim 3, wherein the ratio satisfies the following formula 2: D ４ / D ３ ≧0.90 ・・・Formula 2

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