JP2008064569A - Mechanical characteristic testing device, and strain gage for hydrogen atmosphere used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanical characteristic testing device capable of detecting a stable measured value by preventing a strain gage from being influenced by hydrogen gas, concerning the mechanical characteristic testing device wherein a test piece is arranged under a high-pressure gas atmosphere including hydrogen gas, and a load is applied to the test piece, and the load applied to the test piece and/or displacement are detected by using the strain gage attached to a load cell. <P>SOLUTION: In this mechanical characteristic testing device 1 wherein a high-pressure container into which high-pressure gas including hydrogen gas is introduced is provided, and a test load loading detection device 18 to which the strain gage 10 for loading the load to the test piece 11 for evaluating a mechanical characteristic and detecting the load applied to the test piece 11 and/or the displacement is attached is disposed in the high-pressure container, the strain gage 10 comprises a Cu-Ni metal foil gage having the thickness of 10-25 μm or a Fe-Cr-Al metal foil gage having the thickness of 10-25 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mechanical property test apparatus for performing a mechanical property test of a test piece in a high-pressure gas atmosphere and a strain gauge used therefor, and more specifically, a test load load disposed in a high-pressure vessel containing hydrogen gas. The present invention relates to a mechanical property test apparatus with improved detection accuracy of a strain gauge attached to a load cell of the detection apparatus, and a hydrogen atmosphere strain gauge used therefor.

  To understand the mechanical properties such as tensile strength, compressive strength, bending strength, and tensile fatigue strength of materials such as metals, resins, and ceramics used in a high-pressure gas atmosphere are equipment that uses these materials in a high-pressure gas atmosphere. This is important in design. Under such a special environment, a peculiar phenomenon of the material is expressed.

  Generally, the strength characteristics of materials such as metals, resins, and ceramics change under a high-pressure gas atmosphere. For example, it is known that the ductility of a metal increases under a high pressure of several hundred MPa, and in a specific gas atmosphere, for example, a high-pressure hydrogen gas atmosphere, a steel material absorbs hydrogen and becomes brittle. It is known.

  In recent years, research and development of fuel cells using hydrogen as fuel has been activated, and rapid progress from the prototype stage to the practical stage has been recognized for its application, mainly in automobiles and household use. In particular, in automotive applications, application to commercial vehicles is rapidly being developed in the form of a global warming problem and rising fossil fuels. In such automobile applications, a compressed hydrogen type in which hydrogen compressed to a high pressure of 35 MPa or 70 MPa is used as a fuel is preceded, and characteristics of pressure reducing valves and piping materials used in a high-pressure hydrogen gas atmosphere are preceded. Is an urgent need.

  On the other hand, in a high-pressure hydrogen gas atmosphere of several tens to several hundred MPa, a test apparatus for measuring mechanical properties such as tensile strength is also exposed to such an atmosphere. However, the fact is that there are not enough measuring devices.

  In order to measure mechanical properties such as tensile strength and compressive strength of a material, a load is applied to a test piece of a specific size and shape, and at the same time, both the load applied to the test piece and the amount of deformation are measured. There is a need. When such a measurement is performed in a high-pressure gas atmosphere, the test piece is stored in a test load load detection device provided inside the high-pressure vessel that forms the high-pressure gas atmosphere, and the test piece is loaded from the outside of the high-pressure vessel. A load will be applied separately. The load applied to the test piece is detected by a load cell that is arranged in the test load load detection device and is provided with a strain gauge.

  Regarding the apparatus for measuring such mechanical characteristics, the inventors suppressed the frictional force when applying a load to the test piece in the high-pressure vessel from the outside via the member (pull rod) as described above, In addition, a mechanical property test apparatus has already been proposed for the purpose of reducing the influence of load value errors due to the action force of the high-pressure gas acting on the pull rod and the friction force of the seal ring while preventing gas leakage ( Patent Document 1).

The mechanical property testing apparatus according to the above conventional example will be described with reference to the accompanying drawings. FIG. 6 is a longitudinal sectional view thereof.
According to the mechanical property test apparatus according to this conventional example, after the test piece 48 is mounted in the high-pressure vessel 42, high-pressure gas is introduced, and a load is applied to the test piece 48 based on a high-pressure gas atmosphere of a specific condition. Then, in the mechanical property test apparatus 41 for measuring the deformation amount of the test piece, the high-pressure vessel 42 includes a cylindrical main body 44 having an opening at at least one end, and a lid that closes the opening so as to be freely opened and closed. 46.

  At the same time, this mechanical property test apparatus is capable of engaging and disengaging the axial force applied to the lid 46 from the outside when the high pressure gas is introduced into the high pressure vessel 42 from the gas inlet A. The amount of deformation of the test piece 48 by the actuator portion 40 that applies a load to the test piece 48 supported by the pressed press frame 47 and fixed to the cover portion 46 through the rod 49 penetrating the cover portion 46. The configuration is measurable.

  At the same time, this mechanical property test apparatus has a structure in which the test piece 48 can be mounted and taken out by detaching the press frame 47 and opening the lid 46. Further, the rod 49 is provided with a fluid balance mechanism 43 that reduces or eliminates the acting force applied to the rod 49 by the high-pressure gas.

  Incidentally, the test load of the test piece 48 is measured by using a strain gauge (not shown) attached to the outer peripheral surface of the pull rod 49 in the high-pressure vessel 42. In general, there are two types of strain gauges: a wire gauge using a metal resistance wire and a foil gauge using a metal resistance foil. FIG. 7 shows a plan view of a line gauge type strain gauge with the cover film removed, and FIG. 8 shows a plan view of a foil gauge type strain gauge with the cover film removed. Further, FIG. 9 shows a longitudinal sectional view including the cover film of the strain gauge shown in FIGS.

  That is, the wire gauge type and foil gauge type strain gauges indicated by reference numerals 50 and 54 are respectively made of a metal base wire 51 or a metal resistance foil 55 made of Cu—Ni alloy or Ni—Cr alloy, and a gauge base which is an insulating layer. 53 and the cover film 56 are sandwiched up and down in a sandwich structure and bonded with an adhesive. Generally, the metal resistance wire 51 has a diameter of about 25 to 60 μm, and the metal resistance foil 55 has a thickness of 3 to 6 μm.

  The gauge base 53 as the insulating layer is formed of a resin such as polyimide or epoxy. Such strain gauges 50 and 54 are sensors that detect a minute dimensional change of a measurement object attached thereto as an electrical signal from the gauge lead 52, and are often used in general characteristic evaluation tests of materials. .

  However, in a high-pressure gas atmosphere containing hydrogen gas as described above, this hydrogen gas penetrates into the strain gauge material Cu-Ni alloy or Ni-Cr alloy, causing a change in resistance value, and as a result. It has been found that the detected distortion value acts to generate an error. Therefore, when the strain gauge is attached to the outer peripheral surface of the pull rod 49 as in the conventional example, the output changes due to the influence of hydrogen gas even if no external load is applied. .

Next, a material testing apparatus according to a conventional example capable of avoiding the influence of such hydrogen gas will be described below with reference to FIGS. FIG. 10 is a view showing the entire material testing apparatus according to the conventional example, and FIG. 11 is an enlarged view showing a CT test piece and a crack opening displacement measuring instrument portion of the material testing apparatus shown in FIG. is there. According to the crack opening displacement measuring instrument and the material testing apparatus thereof according to this conventional example, as shown in FIG. 11, the dimensional change amount of the test piece 60 in the high-pressure vessel 62 is measured via the displacement detection rod 82. As a signal, the crack opening displacement measuring instrument 64 is used to take it out of the high-pressure vessel 62.

  That is, according to the crack opening displacement measuring instrument 64 and the material testing apparatus 61 thereof according to this conventional example, the test piece 60 having a notch in which the opening width is defined by the distance between the first edge 77 and the second edge 78. In addition, a crack opening displacement measuring instrument 64 for measuring the opening width when a tensile force is applied to the first edge 77 at one end 71a in order to transmit the displacement of the opening width as an electrical signal to be described later. A first detection lever 71 that contacts the second edge 78 and a second detection lever 72 that contacts the second edge 78 at one end 72a.

  At the same time, a first fulcrum member 73 is disposed between the first detection lever 71 and the second detection lever 72, and the first fulcrum member 73 is in contact with the first detection lever 71. A first fulcrum member 73 capable of inclining the first detection lever 71 and the second detection lever 72 with a contact portion and a contact portion between the first fulcrum member 73 and the second detection lever 72 as a fulcrum, respectively; ing.

At the same time, biasing means 76 for biasing the first detection lever 71 and the second detection lever 72 so that the one end 71a of the first detection lever 71 and the one end 72a of the second detection lever 72 are separated from each other. And signal generating means 65 for generating an electrical signal corresponding to a change in distance between the other end 71b of the first detection lever 71 and the other end 72b of the second detection lever 72 (Patent Document). 2).
As described above, the influence of hydrogen gas can be eliminated by adopting a configuration in which the displacement is extracted as an electric signal without using a strain gauge.
JP 2004-340920 A JP 2003-329557 A

  However, the crack opening displacement measuring instrument 64 and its material testing apparatus 61 according to the conventional example have a complicated structure and the dimensional change of the test piece 60 is extremely small. Production is required. In addition, every time the test piece 60 is replaced, a large amount of dismantling / assembling adjustment work is required, which has the disadvantage that it takes too much cost and time. Furthermore, from such a situation, the measurement accuracy was not satisfactory.

  Accordingly, an object of the present invention is to place a test piece in a high-pressure gas atmosphere containing hydrogen gas, apply a load to the test piece, and attach the load and / or displacement applied to the test piece to the load cell. In a mechanical property test apparatus for detecting using a strain gauge, a mechanical property test apparatus for enabling the strain gauge to detect a stable measurement value without being affected by hydrogen gas, and a hydrogen atmosphere used therefor It is to provide a strain gauge for use.

  In view of the circumstances as described above, the inventors have conducted various investigations and studies on the influence of hydrogen gas on the strain gauge. As a result, the inventors have found that the degree of the influence varies greatly depending on the type and thickness of the metal resistance foil. This has led to the invention.

  In order to achieve the above-mentioned object, the means adopted by the mechanical property test apparatus according to claim 1 of the present invention is provided with a high-pressure vessel into which a high-pressure gas containing hydrogen gas is introduced. And a mechanical load testing device provided with a test load detecting device provided with a strain gauge for detecting the load and / or displacement applied to the test piece. The strain gauge is composed of a Cu—Ni metal foil gauge having a thickness of 10 to 25 μm or an Fe—Cr—Al metal foil gauge having a thickness of 10 to 25 μm.

  The means employed by the mechanical property test apparatus according to claim 2 of the present invention is the mechanical property test apparatus according to claim 1, wherein the strain gauge is made of at least one material selected from aluminum, gold and zinc. It is characterized by being coated with a thin film.

  The means adopted by the strain gauge for hydrogen atmosphere according to claim 3 of the present invention is a strain gauge for detecting a load and / or displacement applied to a test piece in a high-pressure gas atmosphere containing hydrogen gas. Is made of a Cu-Ni metal foil gauge having a thickness of 10 to 25 µm or an Fe-Cr-Al metal foil gauge having a thickness of 10 to 25 µm.

  The hydrogen atmosphere strain gauge according to claim 4 of the present invention employs the hydrogen atmosphere strain gauge according to claim 3, wherein the strain gauge is made of at least one selected from aluminum, gold and zinc. It is characterized in that it is coated with a thin film depending on the material.

  The mechanical property testing apparatus according to claim 1 of the present invention is provided with a high-pressure vessel into which high-pressure gas containing hydrogen gas is introduced, and loads a test piece for evaluating mechanical properties into the high-pressure vessel. In addition, the present invention relates to a mechanical property test apparatus provided with a test load load detection device provided with a strain gauge for detecting a load and / or displacement applied to the test piece.

  In this mechanical property test apparatus, since the strain gauge is made of a Cu-Ni metal foil gauge having a thickness of 10 to 25 µm or an Fe-Cr-Al metal foil gauge having a thickness of 10 to 25 µm, an atmosphere containing hydrogen gas is used. However, the former does not cause a change in the resistance value of the strain gauge, and the latter does not easily allow hydrogen gas to enter the metal foil. As a result, the strain gauge output is not disturbed, and the load is highly accurate and stable. And displacement can be measured.

  In the mechanical property test apparatus according to claim 2 of the present invention, since the strain gauge is thin-film coated with a material made of at least one selected from aluminum, gold and zinc, these materials transmit hydrogen. However, it is possible to eliminate the disturbance of the hydrogen gas to the strain gauge itself, and to measure the load and displacement more stably.

  On the other hand, the strain gauge for hydrogen atmosphere according to claim 3 of the present invention is a strain gauge for detecting a load and / or displacement applied to a test piece in a high-pressure gas atmosphere containing hydrogen gas. Since it consists of a Cu-Ni metal foil gauge having a thickness of 10 to 25 μm or an Fe—Cr—Al metal foil gauge having a thickness of 10 to 25 μm, the former causes a change in the resistance value of the strain gauge even in an atmosphere containing hydrogen gas. In the latter case, hydrogen gas hardly penetrates into the metal foil, and as a result, it is possible to detect a load and displacement with high accuracy without giving disturbance to the output of the strain gauge.

  In the hydrogen atmosphere strain gauge according to claim 4 of the present invention, since the strain gauge is thin-film coated with at least one material selected from aluminum, gold, and zinc, these materials transmit hydrogen. Therefore, it is possible to eliminate the disturbance of the hydrogen gas to the strain gauge itself, and to detect a load and displacement more stably.

First, a mechanical property test apparatus according to Embodiment 1 of the present invention will be described below with reference to FIG.
In FIG. 1, a mechanical property test apparatus 1 according to Embodiment 1 of the present invention includes a pressure vessel 2, a lower lid 3, and a test load load detection device 18. The pressure vessel 2 and the lower lid 3 are fitted so as to be slidable in the axial direction via the seal ring 16, and both constitute a high-pressure vessel to maintain a high-pressure gas atmosphere.

  The test load detection device 18 includes a pull rod 4 for applying a test load to the test piece 11, a mounting jig 14 for transmitting the load received from the pull rod 4 to the test piece 11, and a strain for detecting the test load. A load cell 7 to which a gauge 10 is attached, a stay 9 and an upper plate 8 that are sandwiched between the load cell 7 and fixed to a column 5 to be described later, and the stay 9 and the upper plate 8 are supported and fixed to the lower lid 3. It is comprised from the support | pillar 5.

  Here, reference numeral 12 denotes a nut for fixing the test piece 11 and the load cell 7, and reference numeral 13 denotes a nut for fixing the test piece 11 and the mounting jig 14. The method of attaching the strain gauge to the load cell 7 is not limited to sticking, and other fixing methods may be used.

  The test load load detection device 18 is housed in a high pressure vessel composed of the pressure vessel 2 and the lower lid 3, and a pull rod 4 for applying a test load to the test piece 11 is provided with a seal ring 17. The test load in the high-pressure gas atmosphere is transmitted to the test piece 11 through the lower lid 3 via the.

  The test load is applied to the test piece 11 via the pull rod 4 by an actuator (not shown), and at the same time, the displacement of the test piece 11 can be measured. The actuator includes a piston and a cylinder, and is driven by hydraulic pressure supplied from a hydraulic source. Moreover, the gas pressure at the time of a test is supplied from gas pressure sources, such as a compressor, through a gas introduction hole (not shown).

  The load cell 7 is provided with a strain gauge 10 on its outer surface as will be described later, and is a part for detecting a test load applied to the test piece 11. Also serves as a jig. As the shape of the load cell 7, a cylindrical shape is preferable because it is necessary to apply a uniform test load in the axial direction to the test piece 11. However, the shape of the load cell 7 is not necessarily limited to the cylindrical shape, and the response of the load cell 7 to the load is not necessarily limited. In order to improve the accuracy, it is also included to form a cylindrical shape so as to reduce the cross-sectional area.

  The resistance element of the strain gauge 10 for hydrogen atmosphere according to the present invention attached to the load cell 7 uses a Cu-Ni metal foil having a thickness of 12.7 μm. The Cu—Ni metal foil has a relatively small change in output as a strain gauge even when hydrogen molecules enter. This is because the Cu—Ni alloy is a material crystallographically having a large amount of hydrogen solid solution, and has a material composition that is insensitive to changes in strain gauge output due to the penetration of hydrogen molecules. The resistance element of the strain gauge 10 for hydrogen atmosphere according to the present invention may be formed of an Fe—Cr—Al metal foil. The Fe—Cr—Al metal foil is a material in which an aluminum oxide film is formed on the surface, so that hydrogen molecules are relatively difficult to penetrate.

  Furthermore, the strain gauge 10 for hydrogen atmosphere according to the present invention made of such a Cu—Ni metal foil or Fe—Cr—Al metal foil is preferably made of a metal foil having a thickness of 10 to 25 μm. If the thickness of the metal foil is less than 10 μm, the output change of the gauge is relatively large due to the influence of invaded hydrogen. If the thickness of the metal foil exceeds 25 μm, the thickness of the metal foil is too thick to follow the strain change. Because it becomes impossible.

  The reason why the hydrogen atmosphere strain gauge 10 according to the present invention is limited to the foil gauge type strain gauge is that the base length L1 (see FIG. 8) of the foil gauge type strain gauge is about 2 to 5 mm. On the other hand, the base length L2 (see FIG. 7) of the wire gauge type strain gauge is as short as 74 mm, which is unsuitable for application in a narrow high-pressure vessel such as the mechanical property testing apparatus according to the present invention. Because.

  Next, a configuration for measuring a test load applied to the test piece 11 using the hydrogen atmosphere strain gauge 10 according to the present invention will be described below with reference to FIG. FIG. 2 is a circuit diagram showing a circuit configuration of a strain gauge for measuring a test load applied to the test piece 11 by the hydrogen atmosphere strain gauge according to the first embodiment of the present invention.

  Reference numerals 21 to 24 in the figure denote hydrogen atmosphere strain gauges, and the Wheatstone bridge circuit 20 is formed by these hydrogen atmosphere strain gauges 21 to 24. Of these strain gauges, two active gauges 21 and 22 are attached in the direction of load application at positions opposite to the outer periphery of the load cell 7 as shown by 10 (21 and 22) in FIG. The two dummy gauges 10 (23, 24) are attached in the circumferential direction of the outer periphery of the load cell 7, which is perpendicular to the active gauge.

  In FIG. 2, a voltage is applied to the Wheatstone bridge circuit 20 by the voltage application power source 26, the voltage measured by the voltmeter 26 is read, and the test load acting on the test piece 11 is detected. ing. By adopting such a circuit configuration, the influence of disturbance uniformly applied to the four strain gauges 21 to 24, for example, the influence of disturbance due to temperature change or hydrostatic pressure is eliminated, and the distortion component at the time of attachment Can be eliminated.

  As described above, the resistance foil material of the hydrogen atmosphere strain gauges 21 to 24 according to the present invention is made of Cu—Ni alloy or Fe—Cr—Al alloy as described above. The amount of hydrogen penetration under the atmosphere is only a few ppm level and is stable. However, when the test temperature is high, the amount of hydrogen intrusion increases. Therefore, when long-term stability is required, the strain gauge is selected from metals that are difficult for hydrogen to permeate, such as gold, aluminum, and zinc. The thin film is preferably coated with at least one material.

  The thin film coating is a plating treatment or sputtering treatment of a material made of at least one selected from aluminum, gold and zinc, and may be coated on the metal resistance foil alone, or the strain gauge is measured with a load cell or the like. It may be coated after being attached to the object. The metal resistance foil is not completely unlikely to be affected by hydrogen under high pressure, and by coating a strain gauge with the above metal that is difficult to permeate hydrogen, more stable measurement is possible. .

Next, a mechanical property test apparatus according to Embodiment 2 of the present invention will be described below with reference to FIG.
However, the difference between the second embodiment of the present invention and the first embodiment is that there is a difference in the configuration of the test piece and the measurement items, and the other configuration is exactly the same as in the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and different points will be described below.

  That is, the test piece of the first embodiment is a test piece for measuring tensile strength and compressive strength, whereas the test piece of the second embodiment is called a CT (compact tension) test piece. It is used to evaluate the fracture toughness value.

  This fracture toughness value is a so-called instability in which a material cracks from its internal defects while being subjected to repeated stress, and the fracture proceeds rapidly without increasing the load starting from it. It refers to the resistance value that a material exhibits when it breaks down. For the evaluation of the fracture toughness value, the test condition of the mechanical property test apparatus of the present invention is set to be equal to the environment in which the material is actually used, and a CT test piece is mounted, and the crack of the test piece is checked. In order to grasp the elongation propagation behavior, it is necessary to measure the crack opening displacement.

  In such a test apparatus, the configuration in which the test load is measured by the load cell 7 and the displacement of the opening dimension of the CT test piece 15 is measured by the clip gauge 30 is different from that of the first embodiment, and the others are completely different. Since it is the same structure, it shall stop at description about this CT test piece 15 and the clip gauge 30. FIG.

  FIG. 4 is an enlarged view of the CT test piece 15 and the clip gauge 30 as viewed from the front. Similar to the load cell 7, four strain gauges 31 to 34 are attached to the upper and lower surfaces of the lead 35 of the clip gauge 30. These four strain gauges 31 to 34 form the Wheatstone bridge circuit 20 shown in FIG. 2 as in the first embodiment of the present invention.

  The Wheatstone bridge circuit 20 compensates the strain gauges 31 and 34 on the outer surface side of the clip gauge 30 and the strain gauges 32 and 33 on the inner surface side. The strain gauges 10 and 31 to 34 formed on the load cell 7 and the clip gauge 30 are composed of a hydrogen atmosphere strain gauge made of a 15 μm thick Fe—Cr—Al metal foil.

  Therefore, in the mechanical property test apparatus 1 according to the second embodiment of the present invention, the strain gauges 10 and 31 to 34 formed on the load cell 7 and the clip gauge 30 are in a hydrogen atmosphere as in the first embodiment according to the present invention as described above. By using the strain gauge for operation, the effect of the hydrogen gas contained in the high-pressure atmospheric gas can be eliminated, and this is the same effect as the mechanical property test apparatus according to Embodiment 1 of the present invention.

Next, an embodiment in which a mechanical property test apparatus according to the present invention and a mechanical property test apparatus according to a conventional example are compared and tested will be described below with reference to FIG.
First, an embodiment of a mechanical property test apparatus according to the present invention provided with a load cell in which the strain gauge is formed of the strain gauge for hydrogen atmosphere according to the present invention will be described.

  In this load cell 7, four strain gauges for hydrogen atmosphere according to the present invention shown in Examples 1 and 2 in Table 1 are attached to the outer surface of the load cell as described above to form a Wheatstone bridge circuit. And configured. Then, together with the test piece 11, this load cell 7 was mounted on the test load load detecting device 18 shown in FIG.

  Thereafter, high-pressure hydrogen gas was introduced into the high-pressure vessel constituted by the pressure vessel 2 and the lower lid 3 while heating to form a high-pressure hydrogen gas atmosphere having a temperature of 90 ° C. and a pressure of 22 MPa. And the change of the drift amount (initial strain) detected with the said strain gauge with respect to hydrogen exposure time was measured, without applying the load by the pull rod 4. FIG. The results are as shown in FIG.

According to FIG. 5, in the present embodiment in which the strain gauge 10 is constituted by the strain gauge for hydrogen atmosphere according to the present invention, the change in the detected initial strain, that is, the zero point drift, regardless of the elapse of the hydrogen exposure time. It can be seen that ± 200 × 10 ⁻⁶ is within the range. That is, by forming the hydrogen atmosphere strain gauge 10 by using a Cu—Ni metal foil gauge having a thickness of 10 to 25 μm or an Fe—Cr—Al metal foil gauge having a thickness of 10 to 25 μm, a high-pressure gas containing hydrogen gas is formed. It can be seen that even under an atmosphere, accurate distortion detection is possible without almost any change in resistance value due to hydrogen gas penetrating into the metal foil.

  Next, a comparative example using the mechanical property test apparatus according to the conventional example provided with a load cell in which the strain gauge 10 is constituted by the strain gauge according to the conventional example will be described.

  Four strain gauges according to the conventional examples shown in Comparative Example-1 and Comparative Example-2 in Table 1 are attached to the outer surface of the load cell having the same outer dimensions as those of the above-mentioned examples with an adhesive on the outer surface. A bridge circuit was constructed. And this load cell with the test piece 11 was mounted | worn with the test load load detection apparatus 18 used in the said Example, and the conventional mechanical characteristic test apparatus was comprised.

  Thereafter, in the same manner as in the above example, hydrogen gas was introduced into a high-pressure vessel constituted by the pressure vessel 2 and the lower lid 3 to form a high-pressure hydrogen gas atmosphere having a temperature of 90 ° C. and a pressure of 45 MPa. Under this high-pressure gas atmosphere, a change in the load detected by the strain gauge with respect to the hydrogen exposure time was measured without applying a test load by the pull rod 4. The results are as shown in FIG.

  According to FIG. 5, it can be seen that the drift of the zero point greatly occurs as the hydrogen exposure time elapses. Hydrogen gas has infiltrated into the metal foil forming the strain gauge, causing a change in resistance value, and when using a strain gauge according to such a conventional example, accurate load and displacement measurement is possible. Indicates that it is impossible.

  As described above, according to the mechanical property test apparatus according to the present invention, the strain gauge is a Cu-Ni metal foil gauge having a thickness of 10 to 25 µm or an Fe-Cr-Al metal foil gauge having a thickness of 10 to 25 µm. Therefore, even in a high-pressure atmosphere containing hydrogen gas, the resistance value of the strain gauge does not change, and as a result, a highly accurate and stable load and displacement measurement can be performed without causing disturbance to the output of the strain gauge. It has become possible.

  On the other hand, according to the strain gauge for hydrogen atmosphere according to the present invention, in the strain gauge for detecting the load and / or displacement applied to the test piece in the high-pressure gas atmosphere containing hydrogen gas, the strain gauge has a thickness. Since it consists of a 10-25 μm Cu—Ni metal foil gauge or a 10-25 μm thick Fe—Cr—Al metal foil gauge, the former does not cause a change in the resistance value of the strain gauge even in an atmosphere containing hydrogen gas. In the latter, hydrogen gas hardly penetrates into the metal foil, and as a result, it is possible to detect a load and displacement with high accuracy without causing disturbance to the output of the strain gauge.

It is a longitudinal cross-sectional view which shows the mechanical characteristic test apparatus which concerns on Embodiment 1 of this invention. It is a Wheatstone bridge circuit diagram which shows the measuring circuit of the strain gauge which concerns on Embodiment 1 of this invention. It is a longitudinal cross-sectional view which shows the mechanical property test apparatus which concerns on Embodiment 2 of this invention. It is the figure which expanded and showed the part of a CT test piece and a clip gauge among the mechanical characteristic test apparatuses shown in FIG. It is the drift amount measurement result of the strain gauge shown by comparing the mechanical property test device concerning the present invention, and the mechanical property test device concerning a conventional example. It is a longitudinal cross-sectional view which shows the mechanical characteristic test apparatus which concerns on a prior art example. It is the top view which removed the cover film and showed the wire gauge type strain gauge which concerns on a prior art example. It is the top view which removed the cover film and showed the foil gauge type strain gauge which concerns on a prior art example. It is the longitudinal cross-sectional view which showed the strain gauge of FIG. 7, 8 including the cover film. It is the whole figure showing the whole material testing apparatus concerning a conventional example. It is the figure which expanded and showed the part of a CT test piece and a crack opening displacement measuring instrument among the material test apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mechanical property test apparatus, 2 ... Pressure vessel, 3 ... Lower lid, 4 ... Pull rod,
5 ... post, 6, 12, 13 ... nut, 7 ... load cell, 8 ... top plate,
9 ... Stay, 10 ... Strain gauge (hydrogen gauge strain gauge), 11 ... Test specimen,
14 ... Mounting jig, 15 ... CT test piece, 16, 17 ... Seal ring,
18 ... Test load detection device, 20 ... Wheatstone bridge circuit,
21 to 24, 31 to 34 ... strain gauge (hydrogen gauge strain gauge),
25 ... Applied power supply, 26 ... Voltmeter, 30 ... Clip gauge, 35 ... Lead

Claims (4)

  A high-pressure vessel into which a high-pressure gas containing hydrogen gas is introduced is provided, and a load is applied to a test piece for evaluating mechanical characteristics in the high-pressure vessel, and the load and / or displacement applied to the test piece In a mechanical property test apparatus provided with a test load load detection apparatus provided with a strain gauge for detecting the strain gauge, the strain gauge is a Cu-Ni metal foil gauge having a thickness of 10 to 25 μm or a thickness of 10 to 25 μm. A mechanical property testing apparatus comprising an Fe-Cr-Al metal foil gauge.   2. The mechanical property testing apparatus according to claim 1, wherein the strain gauge is thin-film coated with a material made of at least one selected from aluminum, gold and zinc.   In a strain gauge for detecting a load and / or displacement applied to a test piece in a high-pressure gas atmosphere containing hydrogen gas, the strain gauge is a Cu-Ni metal foil gauge having a thickness of 10 to 25 μm or a thickness of 10 to 10 μm. A strain gauge for a hydrogen atmosphere, comprising a 25-μm Fe—Cr—Al metal foil gauge. The strain gauge for hydrogen atmosphere according to claim 3, wherein the strain gauge is thin-film coated with a material made of at least one selected from aluminum, gold and zinc.

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