Biaxial Tension Fatigue Test Method for Storage Tank Films

Abstract

The present invention provides a biaxial tensile fatigue test method for a storage tank film, comprising: providing a first film unit; providing a second film unit; installing the second film unit on the second side of the first film unit, wherein in the installed state, the orientation of the second film unit is horizontally deflected by 90° relative to the orientation of the first film unit; installing four first front pressure plates on the first film unit and installing four second front pressure plates on the second film unit; using a clamp of a biaxial tensile fatigue tester to clamp the first tensile clamping areas of the four first front pressure plates and the second tensile clamping areas of the four second front pressure plates, wherein the first tensile clamping areas and the second tensile clamping areas are positioned so that when they are clamped and stretched, the stretching direction is at an angle of 45° to the edge of the first film unit. The above test scheme can simulate the mechanical properties of the film under complex stress states in actual engineering, and can avoid damage to the test equipment caused by lateral forces in non-stretching directions.

Description

Technical Field

[0001] The present application relates to the technical field of storage tank containers, and in particular to a biaxial tensile fatigue test method for storage tank films. Background Art

[0002] The membrane type cryogenic storage tank has the unique advantages of large storage capacity, simple construction process, and low construction cost. With the advancement of low-carbon and environmental protection concepts, membrane type storage tanks have become the mainstream form of storage tanks in the tank industry. The interior of the membrane type storage tank is mainly formed by welding multiple pieces of metal sheets to form a sealed environment. The thickness of the tank film is usually between 0.7 and 2 mm. It will be subjected to pressure and low-temperature shrinkage stress and other working conditions in the tank. In order to test the mechanical properties of the membrane structure and simulate the life results under actual working conditions, the biaxial tensile fatigue test method is usually used to test its mechanical properties. Existing test methods and technologies are usually unable to perform normal tests on structural components that will produce large deformations in the local stretching, or the local deformations produced during the test are inconsistent with the actual project, resulting in large deviations in the test results, and the deformation during the biaxial stretching process is nonlinear deformation, which is difficult to compensate.

[0003] Therefore, it is necessary to provide a biaxial tension fatigue test method for a storage tank film to at least partially solve the above problems. Summary of the invention

[0004] In order to solve the above problems, the present application provides a biaxial tensile fatigue test method for a storage tank film, the biaxial tensile fatigue test method is performed using a biaxial tensile fatigue test fixture, the biaxial tensile fatigue test fixture includes four first front pressing plates and four second front pressing plates, the four first front pressing plates are respectively formed with a first tensile clamping area, the four second front pressing plates are respectively formed with a second tensile clamping area, the biaxial tensile fatigue test method includes:

[0005] A first film unit is provided, the first film unit is formed substantially in a square shape, and comprises a film body and a first corrugation and a second corrugation formed on the film body, the first corrugation and the second corrugation are arranged crosswise to form a cross structure area, the film body forms four plane areas divided by the first corrugation and the second corrugation, the height of the first corrugation is smaller than the height of the second corrugation, and the maximum lateral dimension of the first corrugation is smaller than the maximum lateral dimension of the second corrugation, the first film unit has a first side surface and a second side surface opposite to the first side surface, the first side surface faces the direction in which the first corrugation and the second corrugation are convex;

[0006] Providing a second film unit, the second film unit having the same structure and size as the first film unit, the second film unit having a third side surface and a fourth side surface opposite to the third side surface, the second film unit having third corrugations and fourth corrugations whose sizes correspond to the first corrugations and the second corrugations respectively, and the third side surface faces the direction in which the third corrugations and the fourth corrugations are convex;

[0007] The second film unit is installed on the second side of the first film unit, and in the installed state, the fourth side of the second film unit faces the second side of the first film unit, and the orientation of the second film unit is horizontally deflected by 90° relative to the orientation of the first film unit, so that the position of the third corrugation of the second film unit corresponds to the position of the second corrugation of the first film unit, and the position of the fourth corrugation of the second film unit corresponds to the position of the first corrugation of the first film unit;

[0008] The four first front pressing plates are respectively installed on the four plane areas of the first side surface of the first film unit, wherein the four first front pressing plates are respectively formed with first stretching clamping areas, and the first stretching clamping areas on the four first front pressing plates are respectively located at the four corners of the first film unit;

[0009] The four second front pressing plates are respectively installed on the four plane areas of the third side surface of the second film unit, wherein the four second front pressing plates are respectively formed with second stretching clamping areas, and the second stretching clamping areas on the four second front pressing plates are respectively located at the four corners of the second film unit;

[0010] Use the clamp of a biaxial tension fatigue testing machine to clamp the first stretching clamping areas of the four first front pressure plates located at the four corners of the first film unit and the second stretching clamping areas of the four second front pressure plates located at the four corners of the second film unit to perform biaxial stretching on the first film unit and the second film unit, wherein the first stretching clamping area and the second stretching clamping area are positioned so that when the first stretching clamping area and the second stretching clamping area are clamped and stretched, the stretching direction forms an angle of 45° with the edge of the first film unit.

[0011] Preferably, the biaxial tension fatigue test tooling also includes four support plates, and the biaxial tension fatigue test method also includes: before biaxially stretching the first film unit and the second film unit, installing the four support plates between the first film unit and the second film unit, and the four support plates correspond to the four planar areas of the first film unit and the four planar areas of the second film unit, respectively.

[0012] Preferably, the steps of installing the first membrane unit and the second membrane unit, installing the first front pressing plate and the second front pressing plate, and installing the support plate are performed in the same process.

[0013] Preferably, the first front pressing plate, the first membrane unit, the support plate, the second membrane unit and the second front pressing plate are fastened together by bolt fasteners.

[0014] Preferably, a projection area of ​​each of the four support plates on a horizontal plane parallel to the film body is larger than a projection area of ​​the corresponding first front pressing plate and the second front pressing plate on the horizontal plane.

[0015] Preferably, a projection of each of the four support plates on the horizontal plane covers a projection of the corresponding first front pressing plate and the second front pressing plate on the horizontal plane.

[0016] Preferably, a projection of each of the four support plates on the horizontal plane covers a projection of a corresponding plane area of ​​the first membrane unit on the horizontal plane.

[0017] Preferably, each of the four support plates has a first edge and a second edge respectively adjacent to the first corrugation and the second corrugation, and the first edge and the second edge extend beyond the corresponding plane area and into the cross structure area.

[0018] The biaxial tensile fatigue test method according to the above scheme can simulate the mechanical properties of the film under complex stress states in actual engineering, and can perform tensile fatigue tests on two film units at the same time. In addition, the above test scheme enables both sides of each corner of the first film unit and the second film unit to obtain the same tensile force, thereby preventing the lateral force in the non-tensile direction generated by the inconsistent stiffness coefficients of the four sides of the tank film during the tensile test, thereby avoiding damage to the test equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to better understand the above and other purposes, features, advantages and functions of the present application, reference may be made to the preferred embodiments shown in the accompanying drawings. It should be understood by those skilled in the art that the accompanying drawings are intended to schematically illustrate the preferred embodiments of the present application and have no limiting effect on the scope of the present application.

[0020] Figure 1 It is a three-dimensional schematic diagram of a storage tank film installed with a biaxial tension fatigue test fixture according to a preferred embodiment of the present invention, wherein the storage tank film includes a first film unit;

[0021] Figure 2 for Figure 1A front view of a tank film installed with a biaxial tensile fatigue test fixture according to a preferred embodiment of the present invention as shown in ;

[0022] Figure 3 for Figure 1 A right side view of a tank film installed with a biaxial tensile fatigue test fixture according to a preferred embodiment of the present invention as shown in FIG.

[0023] Figure 4 The figure shows the deformation trend of the tank film according to a preferred embodiment of the present invention in actual engineering;

[0024] Figure 5 It is a three-dimensional schematic diagram of a storage tank film installed with a biaxial tension fatigue test fixture according to a preferred embodiment of the present invention, wherein the storage tank film includes a first film unit and a second film unit;

[0025] Figure 6 for Figure 5 A top view of a tank film installed with a biaxial tensile fatigue test fixture according to a preferred embodiment of the present invention as shown in FIG.

[0026] Figure 7 for Figure 5 A side view of a tank film installed with a biaxial tensile fatigue test fixture according to a preferred embodiment of the present invention as shown in FIG.

[0027] Figure 8 for Figure 5 An exploded schematic diagram of a tank film equipped with a biaxial tensile fatigue test fixture according to a preferred embodiment of the present invention is shown in FIG.

[0028] Fig. 9 The figure is a flow chart of a biaxial tension fatigue test method according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0029] Now, with reference to the accompanying drawings, the specific embodiments of the present application are described in detail. What is described here is only the preferred embodiment of the present application. Those skilled in the art can think of other ways to implement the present application based on the preferred embodiment, and the other ways also fall within the scope of the present application.

[0030] First of all, it should be noted that the directional terms and positional terms mentioned in the present invention are only exemplary descriptions rather than restrictive descriptions. The description of the position of a component should be understood as a relative position rather than an absolute position, and the description of the extension direction of a component should be understood as a relative direction rather than an absolute direction.

[0031] According to one aspect of the present invention, a biaxial tensile fatigue test fixture 130 (hereinafter referred to as "test fixture") for a storage tank film is provided. The storage tank mentioned in the present invention can be used for marine engineering equipment or land engineering equipment. The storage tank film is constructed as a corrugated plate made of a metal material, which is usually arranged on the innermost side of the tank wall for contacting the contents (such as LNG) in the storage tank. In practical applications, multiple film units can be welded to each other to form a complete sealed tank film. Figure 1 FIG. 1 is a perspective view of a tank membrane installed with a test fixture 130 according to a preferred embodiment of the present invention, and the structure of the test fixture 130 will be described in detail below. Figure 1 In the preferred embodiment shown, the tank film includes a first film unit 110. The first film unit 110 is configured to have a substantially square profile as shown in the figure, so as to facilitate a biaxial tension fatigue test thereon.

[0032] The following first refers to Figures 1 to 3 The structure of the first membrane unit 110 according to the preferred embodiment of the present invention will be described.

[0033] The first film unit 110 is roughly formed in a square shape. In order to facilitate the clamping of the biaxial tensile fatigue testing machine, the four corners of the first film unit 110 are cut off to form four cut corners. The first film unit 110 includes a flat film body 111 and a first corrugation 112 and a second corrugation 113 formed on the film body 111. The first corrugation 112 and the second corrugation 113 are arranged perpendicular to each other to form a cross structure area 114, and the film body 111 forms four plane areas 115 divided by the first corrugation 112 and the second corrugation 113. Figure 1 In the illustrated embodiment, the height of the first corrugation 112 is less than the height of the second corrugation 113, and the maximum lateral dimension of the first corrugation 112 is less than the maximum lateral dimension of the second corrugation 113. It should be noted that the "lateral" mentioned here refers to the direction perpendicular to the extension direction of the corrugation, and the "height" refers to the distance in the height direction between the top of the corrugation and the film body 111. The first film unit 110 has a first side surface and a second side surface opposite to the first side surface, and the first side surface faces the direction in which the first corrugation 112 and the second corrugation 113 protrude.

[0034] It is understood that in other embodiments not shown, the profile of the first film unit 110 is not limited to Figure 1 The outline shown in the figure can be set by those skilled in the art according to actual needs, and those skilled in the art can also set the size of the first film unit 110 according to actual needs.

[0035] Combined with the following Figures 1 to 8The structure of the test jig 130 according to the preferred embodiment of the present invention is described in detail. The test jig 130 according to the preferred embodiment of the present invention can be used as an auxiliary tool of a biaxial tensile fatigue testing machine. In the actual tensile test process, the test jig 130 can be fixed on the tank film to be subjected to the tensile test, and then the clamping tool of the biaxial tensile fatigue testing machine is used to clamp on the clamping surface of the test jig 130 to achieve clamping and stretching of the tank film.

[0036] like Figure 1 As shown, the test fixture 130 includes four first front pressing plates 131, and the structures of the four first front pressing plates 131 are substantially the same. The four first front pressing plates 131 can be fixed to the four plane areas 115 on the first side of the first membrane unit 110, respectively. Figure 1 As shown, the contour of each first front pressing plate 131 is substantially consistent with the contour of the corresponding plane area 115. The four first front pressing plates 131 are respectively formed with a first stretching clamping area 132 (such as Figure 6 As shown in FIG. 1 ), a total of four first stretching clamping areas 132 are formed corresponding to the first side surface of the first film unit 110. The shape of the stretching clamping area can be configured according to the shape of the clamp of the biaxial tensile fatigue testing machine. In the illustrated embodiment, the stretching clamping area is approximately square. Figure 6 As shown, the position of the stretching clamping area can be defined by setting a corresponding boundary line on the first front pressing plate 131. Alternatively, those skilled in the art can also set a concave-convex structure on the stretching clamping area as needed to increase the friction between the clamp and the stretching clamp.

[0037] In actual engineering, due to the pressure from the contents in the tank and the low-temperature shrinkage stress, the cross-structure area 114 of the tank film will tend to expand outward, so that the four sides of the tank film will expand to both sides along their own side length directions. Figure 4 As shown in FIG. 1 , the direction indicated by the black solid arrow is the deformation direction of the first corrugation 112 and the second corrugation 113 in actual working conditions. That is, the first corrugation 112 and the second corrugation 113 tend to deform in the direction indicated by the arrow in actual working conditions. According to the principle of force composition and decomposition, the force diffused toward the periphery of the first membrane unit 110 (as shown by the black solid arrow) can be synthesized into a force along Figure 4 In other words, the resultant force along the direction of the four black dotted arrows in the figure can be equivalently decomposed into the forces diffused around. Therefore, in order to restore the mechanical properties of the tank membrane under the complex stress state in actual engineering as much as possible, such as Figure 6As shown, the first stretching clamping areas 132 on the four first front pressing plates 131 are respectively located at the four corners of the first film unit 110 , so that when the first stretching clamping areas 132 are clamped and stretched, the stretching direction forms an angle of 45° with the edge of the first film unit 110 .

[0038] By arranging the first stretching clamping area 132 at the four corners of the first film unit 110, the first film unit 110 can be stretched toward the Figure 4 By this arrangement, the stretching clamping area can be located in the non-stretching area such as the plane area 115 of the first film unit 110 instead of the cross structure area 114, which is convenient for clamping on the one hand, and on the other hand, the clamping position is also suitable for biaxial fatigue stretching without providing nonlinear compensation.

[0039] As mentioned above, in actual engineering, the surface of the tank film will be subjected to pressure from the contents of the tank and low-temperature shrinkage stress, and the back of the film is usually provided with an insulating plate for insulating and supporting the film. Therefore, the film will deform under the action of pressure and cling to the insulating plate. In order to support the back of the tank film during the tensile fatigue test and prevent the tank film from being eccentric or warping during stretching, it is preferred that Figures 1 to 3 and Figures 5 to 8 As shown, the biaxial tensile fatigue test fixture 130 further includes four support plates 134, which can be used to connect to the second side of the first film unit 110 during the tensile fatigue test. Specifically, the four support plates 134 can be fixed to the four planar areas 115 of the first film unit 110, respectively.

[0040] like Figure 8 As shown, the shape of each of the four support plates 134 is substantially consistent with the shape of the plane area 115 of the corresponding first membrane unit 110. Figure 1 As shown, the projection area of ​​each of the four support plates 134 on the horizontal plane parallel to the film body 111 may be smaller than the projection area of ​​the corresponding plane area 115 on the horizontal plane, or, as shown in FIG. Figure 5 As shown, the projection area of ​​each of the four support plates 134 on the horizontal plane parallel to the film body 111 may also be larger than the projection area of ​​the corresponding plane area 115 on the horizontal plane. Figures 1 to 3As shown, each of the four support plates 134 has a first edge 134a and a second edge 134b adjacent to the first corrugation 112 and the second corrugation 113 respectively, and the first edge 134a and the second edge 134b both extend beyond the corresponding plane area 115 and enter into the cross structure area 114. This solution enables the support plate 134 to better support the first film unit 110 during the tensile test and prevent the center of gravity of the tank film and the test tooling as a whole from shifting and causing damage to the test equipment.

[0041] like Figures 1 to 3 As shown, preferably, the projection of each of the four support plates 134 on a horizontal plane parallel to the film body 111 covers the projection of the corresponding first front pressing plate 131 on the horizontal plane, and the projection area of ​​each of the four support plates 134 on the horizontal plane is larger than the projection area of ​​the corresponding first front pressing plate 131 on the horizontal plane. Figures 1 to 3 , the first edge and the second edge of the first front pressing plate 131 corresponding to the support plate 134 do not extend beyond the corresponding plane area 115, but remain within the plane area 115, so that when viewed from the side direction, as shown in FIG. Figure 2 and Figure 3 As shown, the support plate 134 and the first front pressing plate 131 form a stepped design.

[0042] In actual engineering, when a biaxial tensile fatigue test is intended to be performed on the tank membrane, the first front pressure plate 131 , the first membrane unit 110 and the support plate 134 may be fastened together by bolt fasteners 140 .

[0043] Since the first corrugations 112 and the second corrugations 113 of the first membrane unit 110 have different heights and lateral dimensions, the stiffness coefficients K of the first membrane unit 110 at the ends of the first corrugations 112 and the second corrugations 113 are also different. Figure 4 As shown, the end A and the end D of the first corrugation 112 have the same structural features, and the end B and the end C of the second corrugation 113 have the same structural features. Therefore, from the perspective of mechanical properties: KA=KD>KB=KC.

[0044] When the first film unit 110 is stretched at 45° as described above, in order to ensure that both sides of each corner of the first film unit 110 have the same stretching force, as shown in FIG. Figure 5 , Figure 7 and Figure 8As shown, preferably, during the test, a second film unit 120 is also connected to the first film unit 110. The second film unit 120 has the same structure and size as the first film unit 110. Specifically, the second film unit 120 has a third side surface and a fourth side surface corresponding to the first side surface and the second side surface of the first film unit 110, and the second film unit 120 has a third corrugation 121 and a fourth corrugation 122, and the sizes of the third corrugation 121 and the fourth corrugation 122 correspond to the first corrugation 112 and the second corrugation 113, respectively, that is, the height of the third corrugation 121 is smaller than the height of the fourth corrugation 122, and the maximum lateral dimension of the third corrugation 121 is smaller than the maximum lateral dimension of the fourth corrugation 122. The third side surface of the second film unit 120 faces the direction where the third corrugation 121 and the fourth corrugation 122 protrude.

[0045] In the actual test process, the second film unit 120 can be connected to the second side of the first film unit 110. In the connected state, the fourth side of the second film unit 120 faces the second side of the first film unit 110, and the orientation of the second film unit 120 is horizontally deflected by 90° relative to the orientation of the first film unit 110. That is, the position of the third corrugation 121 of the second film unit 120 corresponds to the position of the second corrugation 113 of the first film unit 110, and the position of the fourth corrugation 122 of the second film unit 120 corresponds to the position of the first corrugation 112 of the first film unit 110. Through the rotational superposition of the first film unit 110 and the second film unit 120, the tank film can have the same stiffness coefficient at the four ends of the first corrugation 112 and the second corrugation 113, thereby, the first film unit 110 and the second film unit 120 can be subjected to tensile fatigue tests at the same time, and the two sides of each corner of the first film unit 110 can also obtain the same tensile force, and the two sides of each corner of the second film unit 120 can also obtain the same tensile force. The above scheme can prevent the workpiece from rotating due to the inconsistent stiffness coefficients of the four sides of the tank film during the tensile test, thereby avoiding the film workpiece from damaging the test equipment.

[0046] like Figure 5 , Figure 7 and Figure 8As shown, the test fixture 130 also includes four second front pressing plates 133 connected to the second film unit 120. Similar to the first front pressing plate 131, the four second front pressing plates 133 can be fixed to the four plane areas 115 of the second film unit 120 at the third side of the second film unit 120, wherein the four second front pressing plates 133 are respectively formed with second stretching clamping areas (not shown), and the second stretching clamping areas on the four second front pressing plates 133 are respectively located at the four corners of the second film unit 120. The second stretching clamping areas are arranged in the same manner as the first stretching clamping areas, for example, the positions of the stretching clamping areas can be defined by setting corresponding boundary lines on the second front pressing plates 133.

[0047] In the connected state of the first membrane unit 110 and the second membrane unit 120, the four support plates 134 are disposed between the first membrane unit 110 and the second membrane unit 120. Preferably, the first front pressing plate 131, the first membrane unit 110, the support plates 134, the second membrane unit 120 and the second front pressing plate 133 are fastened together by bolt fasteners 140.

[0048] like Fig. 9 As shown, the present invention also provides a biaxial tension fatigue test method for a storage tank film on the other hand, the biaxial tension fatigue test method comprising:

[0049] Providing a first membrane unit 110;

[0050] providing a second membrane unit 120;

[0051] Installing the second membrane unit 120 on the second side of the first membrane unit 110;

[0052] Four first front pressing plates 131 are respectively installed on the four plane areas 115 of the first side surface of the first membrane unit 110;

[0053] Four second front pressing plates 133 are respectively installed on the four plane areas 115 of the third side surface of the second membrane unit 120;

[0054] Four support plates 134 are installed between the first membrane unit 110 and the second membrane unit 120, and the four support plates 134 correspond to the four plane areas 115 of the first membrane unit 110 respectively;

[0055] The first and second stretching clamping areas 132 and 133 of the first and second front pressure plates 131 and 133 located at the four corners of the first and second film units 110 and 120 are clamped using a fixture of a biaxial tension fatigue testing machine to perform biaxial stretching on the first and second film units 110 and 120 .

[0056] Preferably, the steps of installing the first membrane unit 110 and the second membrane unit 120 , installing the first front pressing plate 131 and the second front pressing plate 133 , and installing the supporting plate 134 are performed in the same process.

[0057] Further preferably, the first front pressing plate 131, the first film unit 110, the support plate 134, the second film unit 120 and the second front pressing plate 133 are fastened together by bolt fasteners. The specific structures and connection relationships of the first front pressing plate 131, the first film unit 110, the support plate 134, the second film unit 120 and the second front pressing plate 133 have been described in detail above, and will not be repeated here for the sake of brevity.

[0058] According to the biaxial tensile fatigue test fixture 130 and the biaxial tensile fatigue test method of the above scheme, the mechanical properties of the film under the complex stress state in the actual working condition can be simulated, and the tensile fatigue test can be performed on two film units at the same time. In addition, the above scheme enables both sides of each corner of the first film unit 110 and the second film unit 120 to obtain the same tensile force, thereby preventing the workpiece from rotating due to the inconsistent stiffness coefficients of the four sides of the tank film during the tensile test, thereby avoiding damage to the test equipment.

[0059] The above description of the various embodiments of the present application is provided to a person of ordinary skill in the relevant field for the purpose of description. It is not intended that the present application be exclusive or limited to a single disclosed embodiment. As above, a person of ordinary skill in the field of the above teaching will understand the various substitutions and modifications of the present application. Therefore, although some alternative embodiments are specifically described, a person of ordinary skill in the art will understand or relatively easily develop other embodiments. The present application is intended to include all substitutions, modifications and variations of the present application described herein, as well as other embodiments falling within the spirit and scope of the present application described above.

Claims

1. A biaxial tensile fatigue test method for a storage tank film, characterized in that: The biaxial tension fatigue test method is performed using a biaxial tension fatigue test fixture (130), the biaxial tension fatigue test fixture (130) comprising four first front pressing plates (131) and four second front pressing plates (133), the four first front pressing plates (131) respectively having first tension clamping areas (132), and the four second front pressing plates (133) respectively having second tension clamping areas, the biaxial tension fatigue test method comprising: A first film unit (110) is provided. The first film unit (110) is substantially formed in a square shape and comprises a film body (111) and a first corrugation (112) and a second corrugation (113) formed on the film body (111). The first corrugation (112) and the second corrugation (113) are arranged crosswise to form a cross structure area (114). The film body (111) forms four plane areas (115) divided by the first corrugation (112) and the second corrugation (113). The height of the first corrugation (112) is smaller than the height of the second corrugation (113), and the maximum lateral dimension of the first corrugation (112) is smaller than the maximum lateral dimension of the second corrugation (113). The first film unit (110) has a first side surface and a second side surface opposite to the first side surface. The first side surface is convex toward the direction in which the first corrugation (112) and the second corrugation (113) are convex. A second film unit (120) is provided, wherein the second film unit (120) has the same structure and size as the first film unit (110), the second film unit (120) has a third side surface and a fourth side surface opposite to the third side surface, the second film unit (120) has a third corrugation (121) and a fourth corrugation (122) whose sizes correspond to the first corrugation (112) and the second corrugation (113), respectively, and the third side surface is convex toward the direction of the third corrugation (121) and the fourth corrugation (122); The second film unit (120) is installed on the second side of the first film unit (110), wherein in the installed state, the fourth side of the second film unit (120) faces the second side of the first film unit (110), and the orientation of the second film unit (120) is horizontally deflected by 90° relative to the orientation of the first film unit (110), so that the position of the third corrugation (121) of the second film unit (120) corresponds to the position of the second corrugation (113) of the first film unit (110), and the position of the fourth corrugation (122) of the second film unit (120) corresponds to the position of the first corrugation (112) of the first film unit (110); The four first front pressing plates (131) are respectively installed on the four plane areas (115) of the first side surface of the first film unit (110), wherein the four first front pressing plates (131) are respectively formed with first stretching clamping areas (132), and the first stretching clamping areas (132) on the four first front pressing plates (131) are respectively located at the four corners of the first film unit (110); The four second front pressing plates (133) are respectively installed on the four plane areas (115) of the third side surface of the second film unit (120), wherein the four second front pressing plates (133) are respectively formed with second stretching clamping areas, and the second stretching clamping areas on the four second front pressing plates (133) are respectively located at the four corners of the second film unit (120); The first stretching clamping areas (132) of the four first front pressure plates (131) located at the four corners of the first film unit (110) and the second stretching clamping areas of the four second front pressure plates (133) located at the four corners of the second film unit (120) are clamped using a clamp of a biaxial tension fatigue testing machine to perform biaxial stretching on the first film unit (110) and the second film unit (120), wherein the first stretching clamping areas (132) and the second stretching clamping areas are positioned so that when the first stretching clamping areas (132) and the second stretching clamping areas are clamped and stretched, the stretching direction forms an angle of 45° with the edge of the first film unit (110).

2. The biaxial tension fatigue test method according to claim 1, characterized in that: The biaxial tension fatigue test fixture (130) further includes four support plates (134), and the biaxial tension fatigue test method further includes: before biaxially stretching the first film unit (110) and the second film unit (120), installing the four support plates (134) between the first film unit (110) and the second film unit (120), and the four support plates (134) respectively correspond to the four planar areas (115) of the first film unit (110) and the four planar areas (115) of the second film unit (120).

3. The biaxial tension fatigue test method according to claim 2, characterized in that: The steps of installing the first film unit (110) and the second film unit (120), the steps of installing the first front pressing plate (131) and the second front pressing plate (133), and the step of installing the support plate (134) are performed in the same process.

4. The biaxial tension fatigue test method according to claim 3, characterized in that: The first front pressure plate (131), the first membrane unit (110), the support plate (134), the second membrane unit (120), and the second front pressure plate (133) are fastened together by bolt fasteners (140).

5. The biaxial tension fatigue test method according to claim 2, characterized in that: The projection area of ​​each of the four support plates (134) on a horizontal plane parallel to the film body (111) is larger than the projection areas of the corresponding first front pressing plate (131) and the second front pressing plate (133) on the horizontal plane.

6. The biaxial tension fatigue test method according to claim 5, characterized in that: The projection of each of the four support plates (134) on the horizontal plane covers the projection of the corresponding first front pressing plate (131) and the second front pressing plate (133) on the horizontal plane.

7. The biaxial tension fatigue test method according to claim 5, characterized in that: The projection of each of the four support plates (134) on the horizontal plane covers the projection of the corresponding plane area (115) of the first film unit (110) on the horizontal plane.

8. The biaxial tension fatigue test method according to claim 7, characterized in that: Each of the four support plates (134) has a first edge (134a) and a second edge (134b) respectively adjacent to the first corrugation (112) and the second corrugation (113), and the first edge and the second edge extend beyond the corresponding plane area (115) and into the cross structure area (114).

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