Low-cycle fatigue test device for metal sheet for LNG (Liquefied Natural Gas) film tank and use method of low-cycle fatigue test device

Abstract

The invention discloses a low-cycle fatigue test device for a metal sheet for an LNG (Liquefied Natural Gas) film tank and a use method of the low-cycle fatigue test device. The device comprises an upper clamp, a lower clamp and an anti-buckling plate which is in sliding fit with the upper clamp and the lower clamp respectively. The upper clamp and the lower clamp are respectively in sliding fit with the buckling-restrained plate, so that the upper clamp and the lower clamp are respectively in sliding contact with the buckling-restrained plate, and zero clearance between the contact surfaces of the upper clamp and the buckling-restrained plate and between the contact surfaces of the lower clamp and the buckling-restrained plate is ensured; the situation that the test sample is bent at the contact surface positions of the upper clamp and the buckling-restrained plate and the contact surface positions of the lower clamp and the buckling-restrained plate, so that the test is invalid is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue performance testing of materials and industrial products, and in particular to a metal sheet low-cycle fatigue testing device for LNG membrane tanks and a use method thereof. Background Art

[0002] As an important material in the structure of LNG membrane tanks, the performance of metal sheets has attracted extensive attention. Under actual working conditions, metal sheets will be subjected to continuous cyclic loads, so the investigation of their fatigue performance indicators, especially low-cycle fatigue performance indicators, has important guiding significance for the design of LNG membrane tank structures. However, metal sheets have small dimensions in the thickness direction, a large slenderness ratio, and low stiffness. When subjected to tension and compression cyclic loads, lateral buckling instability in the thickness direction is prone to occur. Therefore, in the strain-controlled low-cycle fatigue test of metal sheets, preventing buckling instability in order to obtain reliable test data has become a technical problem that needs to be solved urgently.

[0003] In the prior art, the authorization announcement number CN102735557B discloses a vehicle body sheet fatigue test device and test method, and the application number CN200620012080.3 discloses an anti-bending fixture for axial tension and compression fatigue test of metal sheets. When the above prior art is used to install the sample, there will be a gap between the anti-buckling device and the test machine fixture, that is, there is a part of the clamped end of the sample that is not subject to any constraints. The part of the sample that is not subject to any constraints is also in a plane stress state during the fatigue test. Therefore, this part of the sample is prone to bending, thereby Resulting in the test being invalid; Authorization announcement number CN111766162B discloses an automotive thin plate strain fatigue test device and method, and publication number CN115753382A discloses a method for fatigue testing of plate materials. When the above-mentioned prior art is used to install the specimen, it is necessary to fix the specimen and the split anti-buckling device by tightening the bolts. If an unbalanced torque occurs between the bolts when tightening the bolts, a slight misalignment will occur between the anti-buckling device and the specimen, resulting in a deviation in the coaxiality between the two, thereby affecting the accuracy of the subsequent fatigue test results. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a metal sheet low-cycle fatigue testing device for LNG membrane tanks, which can solve the technical problem in the prior art that there is a gap between the anti-buckling device and the testing machine fixture, which makes the sample located at the gap prone to bending, thereby resulting in invalid test. It can also solve the technical problem in the prior art that a split anti-buckling device will cause torque imbalance between the connecting parts, resulting in deviation in the coaxiality between the anti-buckling device and the sample, thereby affecting the accuracy of subsequent fatigue test results. At the same time, the present invention also provides a method for using the metal sheet low-cycle fatigue testing device, which is applied to a metal sheet low-cycle fatigue testing device for LNG membrane tanks.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A low-cycle fatigue testing device for metal sheets used in LNG membrane tanks, comprising an upper fixture, a lower fixture, and an anti-buckling plate respectively slidably matched with the upper fixture and the lower fixture;

[0007] The upper clamp has the function of clamping one end of the sample. The upper clamp includes a left upper side clamp and a right upper side clamp arranged in contact with the left upper side clamp. The surfaces of the left upper side clamp and the right upper side clamp that are in contact with each other are provided with a positioning anti-reverse structure I. A plurality of threaded holes I are provided through the surface of the upper clamp. The left upper side clamp and the right upper side clamp are fastened together by the cooperation of bolts I and threaded holes I. An upper slider is provided on the bottom end surface of the upper clamp, and a connecting column I is provided on the outer end surface of the upper clamp.

[0008] The lower clamp has the function of clamping the other end of the sample. The lower clamp includes a left lower side clamp and a right lower side clamp arranged in contact with the lower side clamp. The surfaces of the left lower side clamp and the right lower side clamp that are in contact with each other are provided with a positioning anti-reverse structure II. A plurality of threaded holes II are provided through the surface of the lower clamp. The left lower side clamp and the right lower side clamp are fastened together by the cooperation of bolts II and threaded holes II. A sliding groove is provided on the top surface of the lower clamp.

[0009] The shape of the anti-buckling plate is set to be a wedge-shaped structure, a specimen position gap is opened inside it, a buckling groove I is opened on the upper side end face of the anti-buckling plate, which can slide with the upper slider set on the bottom end face of the upper clamp, a buckling groove II is opened on the bottom end face of the anti-buckling plate, which can slide with the lower sliding groove opened on the top end face of the lower clamp through a rolling member, and a connecting column II is set on the outer side end face of the anti-buckling plate, which is connected to the connecting column I through a tension spring.

[0010] Furthermore, the positioning and anti-rebound structure I includes an A-type positioning and anti-rebound structure and a B-type positioning and anti-rebound structure. The A-type positioning and anti-rebound structure is located on the inner surface of one of the tip parts of the upper right side clamp, and the B-type positioning and anti-rebound structure is located on the inner surface of one of the edge parts of the upper left side clamp. The arrangement of the A-type positioning and anti-rebound structure and the B-type positioning and anti-rebound structure enables the upper left side clamp and the upper right side clamp to form a clamping channel I for clamping one end of the sample when they are fitted together; the number of the threaded holes I is three, one of which is penetrated from the outer surface of the upper left side clamp through the A-type positioning and anti-rebound structure located on the upper right side clamp to the outer surface of the upper right side clamp, and the remaining two threaded holes I are penetrated from the outer surface of the upper left side clamp through the B-type positioning and anti-rebound structure located on the upper left side clamp to the outer surface of the upper right side clamp, and the relative positions of the upper left side clamp and the upper right side clamp are fixed by the cooperation of the bolt I and the threaded hole I.

[0011] Furthermore, there are two upper sliding blocks, which are symmetrically arranged on the bottom inclined surfaces of the left upper side clamp and the right upper side clamp respectively.

[0012] Furthermore, a positioning and anti-reverse structure II is provided on the same end side of the lower left side clamp and the lower right side clamp. When the planes of the lower left side clamp and the lower right side clamp provided with the positioning and anti-reverse structure II are relative and fitted together, a clamping channel II for clamping the other end of the sample will be formed; the number of the threaded holes II is two, one of which is penetrated from the outer surface of the lower left side clamp through the positioning and anti-reverse structure II located on the lower right side clamp to the outer surface of the lower right side clamp, and the remaining threaded hole II is penetrated from the outer surface of the lower left side clamp through the positioning and anti-reverse structure II located on the lower left side clamp to the outer surface of the lower right side clamp.

[0013] Furthermore, there are two lower sliding grooves, which are symmetrically provided on the top surfaces of the left lower side clamp and the right lower side clamp respectively.

[0014] Preferably, the rolling element is a ball bearing to ensure smooth relative sliding between the lower clamp and the anti-buckling plate.

[0015] Furthermore, the sample position gap is opened from the tip of the anti-buckling plate on the right side toward the end on the left side thereof, and the width of the sample position gap is not less than the thickness of the sample.

[0016] Furthermore, a polytetrafluoroethylene sheet is provided on the surface of the sample position gap.

[0017] Furthermore, the number of the buckling grooves I and II is two, which are respectively opened on the left and right sides of the sample position gap. The buckling groove I is opened on the upper end surface of the anti-buckling plate in a direction parallel to the sample position gap, and the buckling groove II is opened on the bottom end surface of the anti-buckling plate in the same direction as the lower groove.

[0018] Furthermore, the connecting column I is arranged on the outer surface of the right upper side clamp, and the connecting column II is arranged on the outer surface of the anti-buckling plate on the same side as the connecting column I.

[0019] The present invention also provides a method for using a metal sheet low cycle fatigue test device, which is applied to the above-mentioned metal sheet low cycle fatigue test device for LNG membrane tanks, and the specific steps include:

[0020] Step S1: First, screw out the bolt I at the threaded hole I of the upper clamp from the threaded hole I, so that the upper left side clamp of the upper clamp is separated from the upper right side clamp, then place the side surface of one end of the sample on the inner surface of the upper left side clamp, so that the side surface of the end of the sample contacts the side surface of the B-type positioning anti-reverse structure of the upper left side clamp, and at the same time, move the anti-buckling plate at an angle parallel to the sample, so that the middle part of the sample enters the sample position gap of the anti-buckling plate, and then, the upper sliders of the upper left side clamp and the upper right side clamp are respectively engaged with the buckling groove I set on the upper end surface of the anti-buckling plate. The upper clamp is connected to the specimen by the upper slider and the buckling groove I, so that the anti-buckling plate can slide relative to the upper clamp under the action of the upper slider and the buckling groove I. Finally, the inner surface of the upper right clamp is aligned with the inner surface of the upper left clamp, so that the other side surface of the end of the specimen is in contact with the side surface of the A-type positioning anti-reverse structure of the upper right clamp. At the same time, the bolt I is screwed into the threaded hole I to fasten the end of the specimen in the clamping channel I. At this time, the tension spring connected to the connecting column I and the connecting column II can ensure that the upper clamp and the anti-buckling plate are in close contact when sliding relative to each other under the action of its elastic force.

[0021] Step S2: In step S1, the bolt II at the threaded hole II of the lower clamp is screwed out from the threaded hole II, so that the lower left side clamp and the lower right side clamp of the lower clamp are separated, and then, the side surface of the other end of the sample is placed on the inner surface of the left lower side clamp, so that the side surface of the end of the sample contacts the side surface of the positioning anti-reverse structure II of the left lower side clamp, and then, under the sliding cooperation of the rolling element with the lower slide groove and the buckling slide groove II respectively, the top end surface of the left lower side clamp and the right lower side clamp can slide in contact with the plane of the anti-buckling plate provided with the buckling slide groove II, so that the anti-buckling plate can slide relative to the lower clamp, and finally, the inner surface of the right lower side clamp is aligned and fitted with the inner surface of the left lower side clamp, so that the other side surface of the end of the sample contacts the side surface of the positioning anti-reverse structure II of the right lower side clamp, and at the same time, the bolt II is screwed into the threaded hole II to fasten the end of the sample in the clamping channel II;

[0022] Step S3: In step S2, the two ends of the sample are clamped by the upper clamp and the lower clamp respectively, and after the middle of the sample is located in the sample position gap of the anti-buckling plate, the low-cycle fatigue test of the sample is started; when the testing machine is used to apply displacement loads to the upper clamp and the lower clamp for compression, the upper clamp and the lower clamp are displaced in a gradually approaching form, and when the distance between the upper clamp and the lower clamp is gradually reduced, the anti-buckling plate will move in a direction away from the connecting column I under the sliding action of the upper slider and the buckling chute I, the rolling element and the lower chute and the buckling chute II, and in this process, the anti-buckling plate only undergoes lateral displacement. , which can prevent the specimen from having coaxial deviation during the test; when the testing machine is used to apply displacement loads to the upper fixture and the lower fixture for stretching, the upper fixture and the lower fixture are displaced in the form of gradually moving away from each other. When the distance between the upper fixture and the lower fixture gradually increases, the tension spring drives the anti-buckling plate and moves towards the direction close to the connecting column Ⅰ under the sliding action of the upper slider and the buckling groove Ⅰ, the rolling element and the lower groove and the buckling groove Ⅱ. In this process, the anti-buckling plate also only undergoes lateral displacement, which ensures that the specimen will not have coaxial deviation during the test, resulting in test failure.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] 1. The present invention has the characteristics of reasonable structural design, strong practicality, and convenient use. In the present invention, the upper clamp and the lower clamp respectively cooperate with the anti-buckling plate, so that the upper clamp and the lower clamp respectively achieve sliding contact with the anti-buckling plate, ensuring zero gap between the contact surfaces of the upper clamp and the lower clamp and the anti-buckling plate, preventing the specimen from bending at the contact surface position between the upper clamp and the anti-buckling plate, and the lower clamp and the anti-buckling plate, thereby causing the test to be invalid;

[0025] 2. The integrated design of the anti-buckling plate in the present invention not only omits the step of aligning and installing during the test, but also increases the rigidity of the anti-buckling plate, avoids deformation of the middle part of the anti-buckling plate during the test, ensures the accuracy of the test, effectively prevents the induction of fatigue crack sources of the sample, increases the life of the sample, and reduces the error of the test;

[0026] 3. The buckling chute I and buckling chute II, which are arranged symmetrically to the gap between the specimen positions, can make the anti-buckling plate and the upper fixture and the lower fixture slide in an aligned manner, thereby ensuring the coaxiality between the anti-buckling plate and the specimen and preventing the anti-buckling plate and the specimen from being misaligned, thereby affecting the accuracy of the subsequent fatigue test results;

[0027] Other beneficial effects of the present invention will be further described in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] Figure 1 It is a schematic diagram of the assembly structure of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the upper clamp of the present invention;

[0031] Figure 3 It is a structural schematic diagram of the upper left side clamp of the upper clamp of the present invention;

[0032] Figure 4 A is a structural schematic diagram of the upper right side clamp of the upper clamp of the present invention;

[0033] Figure 5 FIG. B is a structural schematic diagram of the upper right side clamp of the upper clamp of the present invention;

[0034] Figure 6 It is a structural schematic diagram of the lower clamp of the present invention;

[0035] Figure 7 It is a structural schematic diagram of the lower left side clamp of the lower clamp of the present invention;

[0036] Figure 8 It is a structural schematic diagram of the lower right side clamp of the lower clamp of the present invention;

[0037] Fig. 9 is a schematic structural diagram of the anti-buckling plate of the present invention;

[0038] Wherein: 1. Upper fixture; 101. Upper left side clamp; 102. Upper right side clamp; 103. Type A positioning and anti-reverse structure; 104. Type B positioning and anti-reverse structure; 105. Threaded hole Ⅰ; 106. Upper slider; 107. Connecting column Ⅰ; 2. Lower fixture; 201. Lower left side clamp; 202. Lower right side clamp; 203. Positioning and anti-reverse structure Ⅱ; 204. Threaded hole Ⅱ; 205. Lower slide; 3. Anti-buckling plate; 301. Specimen position gap; 302. Buckling slide Ⅰ; 303. Buckling slide Ⅱ; 304. Tension spring; 305. Connecting column Ⅱ. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] like Figures 1 to 9 As shown, the present invention provides a low cycle fatigue testing device for metal sheets used in LNG membrane tanks.

[0041] It includes an upper clamp 1, a lower clamp 2 and an anti-buckling plate 3 which is slidably matched with the upper clamp 1 and the lower clamp 2 respectively;

[0042] The upper clamp 1 has the function of clamping one end of the sample. The upper clamp 1 includes a left upper side clamp 101 and a right upper side clamp 102 arranged in contact with the left upper side clamp 101. The surfaces of the left upper side clamp 101 and the right upper side clamp 102 that are in contact with each other are provided with a positioning anti-reverse structure I. A plurality of threaded holes I105 are provided through the surface of the upper clamp 1. The left upper side clamp 101 and the right upper side clamp 102 are fastened together by the cooperation of the bolts I and the threaded holes I105. The bottom end surface of the upper clamp 1 is provided with an upper slider 106, and the outer end surface of the upper clamp 1 is provided with a connecting column I107.

[0043] The lower clamp 2 has the function of clamping the other end of the sample. The lower clamp 2 includes a left lower side clamp 201 and a right lower side clamp 202 arranged in contact with the lower side clamp 201. The surfaces of the lower left side clamp 201 and the lower right side clamp 202 that are in contact with each other are provided with a positioning anti-reverse structure II 203. A plurality of threaded holes II 204 are provided through the surface of the lower clamp 2. The left lower side clamp 201 and the right lower side clamp 202 are fastened together by the cooperation of the bolts II and the threaded holes II 204. A sliding groove 205 is provided on the top surface of the lower clamp 2.

[0044] The shape of the anti-buckling plate 3 is set to a wedge structure, and a sample position gap 301 is opened inside the anti-buckling plate 3. A buckling groove I 302 is opened on the upper side end surface of the anti-buckling plate 3, which can slide with the upper slider 106 set on the bottom end surface of the upper fixture 1. A buckling groove II 303 is opened on the bottom end surface of the anti-buckling plate 3, which can slide with the lower slide groove 205 opened on the top end surface of the lower fixture 2 through a rolling member. The outer end surface of the anti-buckling plate 3 is provided with a connecting column II 305 connected to the connecting column I 107 through a tension spring 304;

[0045] In the embodiment of the present invention, the positioning and anti-reverse structure I has the function of determining the relative position between the upper left side clamp 101 and the upper right side clamp 102 to avoid incorrect installation of the upper left side clamp 101 and the upper right side clamp 102. The positioning and anti-reverse structure I includes an A-type positioning and anti-reverse structure 103 and a B-type positioning and anti-reverse structure 104. The A-type positioning and anti-reverse structure 103 is located on the inner surface of one of the tip parts of the upper right side clamp 102, and the B-type positioning and anti-reverse structure 104 is located on the inner surface of one of the edge parts of the upper left side clamp 101. The arrangement of the A-type positioning and anti-reverse structure 103 and the B-type positioning and anti-reverse structure 104 enables the upper left side clamp 101 and the upper right side clamp 102 to form a clamping channel I for clamping one end of the sample when they are fitted together, and the sample One end of the sample is in the clamping channel I, which can prevent the end of the sample from shifting relative to the upper clamp 1 during the test, thereby ensuring the high coaxiality between the clamped part of the sample and the upper clamp 1 during the test; the number of the threaded holes I105 is three, one of which is from the outer surface of the upper left side clamp 101 through the A-type positioning and anti-reverse structure 103 located on the upper right side clamp 102 to the outer surface of the upper right side clamp 102, and the remaining two threaded holes I105 are from the outer surface of the upper left side clamp 101 through the B-type positioning and anti-reverse structure 104 located on the upper left side clamp 101 to the outer surface of the upper right side clamp 102, and the relative positions of the upper left side clamp 101 and the upper right side clamp 102 are fixed by the cooperation of the bolt I and the threaded hole I105;

[0046] In the embodiment of the present invention, two upper sliders 106 are provided, which are symmetrically arranged on the bottom end inclined surfaces of the left upper side clamp 101 and the right upper side clamp 102. Under the sliding cooperation of the buckling groove Ⅰ302 and the upper slider 106, the bottom end surfaces of the left upper side clamp 101 and the right upper side clamp 102 can be in sliding contact with the plane of the anti-buckling plate 3 provided with the buckling groove Ⅰ302, so as to ensure zero gap between the contact surfaces of the upper clamp 1 and the anti-buckling plate 3, thereby preventing the specimen from bending at the contact surface position of the upper clamp 1 and the anti-buckling plate 3, thereby causing the test to be invalid.

[0047] In the embodiment of the present invention, the same end side of the left lower side clamp 201 and the right lower side clamp 202 are both provided with a positioning anti-reverse structure II 203. When the planes of the left lower side clamp 201 and the right lower side clamp 202 provided with the positioning anti-reverse structure II 203 are opposite and attached together, a clamping channel II for clamping the other end of the sample is formed. The other end of the sample can be prevented from shifting relative to the lower clamp 2 during the test in the clamping channel II, thereby ensuring that the clamped part of the sample and the lower clamp 2 are in contact with each other during the test. High coaxiality; the number of the threaded holes II 204 is two, one of which is from the outer surface of the left lower side clamp 201 through the positioning anti-reverse structure II 203 located on the right lower side clamp 202 to the outer surface of the right lower side clamp 202, and the remaining threaded hole II 204 is from the outer surface of the left lower side clamp 201 through the positioning anti-reverse structure II 203 located on the left lower side clamp 201 to the outer surface of the right lower side clamp 202, and the relative positions of the left lower side clamp 201 and the right lower side clamp 202 are fixed by the cooperation of the bolt II and the threaded hole II 204;

[0048] In the embodiment of the present invention, the number of the lower slide grooves 205 is two, which are symmetrically provided on the top surfaces of the left lower side clamp 201 and the right lower side clamp 202. Under the sliding cooperation of the rolling element with the lower slide groove 205 and the buckling slide groove II 303, the top surfaces of the left lower side clamp 201 and the right lower side clamp 202 can slide in contact with the plane of the anti-buckling plate 3 provided with the buckling slide groove II 303, so as to ensure zero gap between the contact surfaces of the lower clamp 2 and the anti-buckling plate 3, and also prevent the specimen from bending at the contact surface of the lower clamp 2 and the anti-buckling plate 3, thereby causing the test to be invalid.

[0049] Preferably, the rolling element is a ball bearing to ensure smooth relative sliding between the lower clamp 2 and the anti-buckling plate 3;

[0050] It should be noted that, in the present invention, the degree of inclination of the bottom end surface of the upper clamp 1 is not further limited, and accordingly, the degree of inclination of the plane of the anti-buckling plate 3 in sliding contact with the bottom end surface of the upper clamp 1 is not further limited. As long as zero gap between the contact surfaces of the upper clamp 1 and the anti-buckling plate 3 can be achieved, it is within the protection scope of the present invention; in the present invention, the top end surface of the lower clamp 2 can be defined as an inclined surface with a certain inclination angle (not shown in the drawings of the specification), and accordingly, the plane of the anti-buckling plate 3 in sliding contact with the top end surface of the lower clamp 2 needs to be adaptively adjusted to ensure zero gap between the contact surfaces of the upper clamp 1 and the anti-buckling plate 3, while ensuring zero gap between the contact surfaces of the lower clamp 2 and the anti-buckling plate 3;

[0051] In the embodiment of the present invention, the sample position gap 301 is opened from the tip of the anti-buckling plate 3 on the right side toward the end on the left side thereof, and the width of the sample position gap 301 is not less than the thickness of the sample, so that the anti-buckling plate 3 can slide smoothly relative to the sample during the test to ensure that the anti-buckling plate 3 is always in close contact with the upper fixture 1 and the lower fixture 2 to ensure the precision and accuracy of the test, and the anti-buckling plate 3 adopts an integrated design, which not only omits the step of aligning and installing during the test, but also the integrated structure increases the rigidity of the anti-buckling plate 3, avoids deformation of the middle part of the anti-buckling plate 3 during the test, ensures the accuracy of the test, effectively prevents the induction of fatigue crack sources of the sample, increases the life of the sample, and reduces the error of the test; the width of the sample position gap 301 can be adjusted to adapt to samples of different thicknesses;

[0052] In the embodiment of the present invention, a polytetrafluoroethylene sheet is provided on the surface of the sample position gap 301. The friction coefficient of the polytetrafluoroethylene sheet is extremely low. The provision of the polytetrafluoroethylene sheet can reduce the friction between the surface of the sample position gap 301 and the sample, thereby ensuring smooth sliding between the anti-buckling plate 3 and the sample.

[0053] In the embodiment described in the present invention, the number of the buckling chute I 302 and the buckling chute II 303 is two, which are respectively opened on the left and right sides of the sample position gap 301. The buckling chute I 302 is opened on the upper end surface of the anti-buckling plate 3 in a direction parallel to the sample position gap 301, and the buckling chute II 303 is opened on the bottom end surface of the anti-buckling plate 3 in the same direction as the opening direction of the lower slide 205; the buckling chute I 302 and the buckling chute II 303 respectively arranged symmetrically with the sample position gap 301 in the present invention can make the anti-buckling plate 3 and the upper fixture 1 and the lower fixture 2 slide in an aligned manner, thereby ensuring the coaxiality of the anti-buckling plate 3 and the sample, and preventing the anti-buckling plate 3 from being misaligned with the sample, thereby affecting the accuracy of the subsequent fatigue test results;

[0054] In the embodiment of the present invention, the connecting column I 107 is arranged on the outer surface of the right upper side clamp 102, and the connecting column II 305 is arranged on the outer surface of the anti-buckling plate 3 on the same side as the connecting column I 107, so that under the elastic force of the tension spring 304, it can be ensured that the upper clamp 1 and the anti-buckling plate 3 are still in close contact when sliding relative to each other;

[0055] The present invention also provides a method for using a metal sheet low cycle fatigue test device, which is applied to the above-mentioned metal sheet low cycle fatigue test device for LNG membrane tanks, and the specific steps include:

[0056] Step S1: First, screw out the bolt I at the threaded hole I105 of the upper fixture 1 from the threaded hole I105, so that the upper left side clamp 101 of the upper fixture 1 is separated from the upper right side clamp 102. Then, place the side surface of one end of the sample on the inner surface of the upper left side clamp 101, so that the side surface of the end of the sample contacts the side surface of the B-type positioning anti-reverse structure 104 of the upper left side clamp 101. At the same time, move the anti-buckling plate 3 at an angle parallel to the sample, so that the middle part of the sample enters the sample position gap 301 of the anti-buckling plate 3. Subsequently, the upper sliders 106 of the upper left side clamp 101 and the upper right side clamp 102 are respectively aligned with the buckling slide groove I302 set on the upper end surface of the anti-buckling plate 3. A fitting connection is made so that the anti-buckling plate 3 can slide relative to the upper clamp 1 under the action of the upper slider 106 and the buckling slide groove Ⅰ302. Finally, the inner surface of the upper right side clamp 102 is aligned with the inner surface of the upper left side clamp 101, so that the other side surface of the end of the sample contacts the side surface of the A-type positioning anti-reverse structure 103 of the upper right side clamp 102. At the same time, the bolt Ⅰ is screwed into the threaded hole Ⅰ105 to fasten the end of the sample in the clamping channel Ⅰ. At this time, the tension spring 304 connected to the connecting column Ⅰ107 and the connecting column Ⅱ305 can ensure that the upper clamp 1 and the anti-buckling plate 3 are still in close contact when sliding relative to each other under the action of its elastic force;

[0057] Step S2: In step S1, the bolt II at the threaded hole II 204 of the lower clamp 2 is screwed out from the threaded hole II 204, so that the left lower side clamp 201 and the right lower side clamp 202 of the lower clamp 2 are separated. Then, the side surface of the other end of the sample is placed on the inner surface of the left lower side clamp 201, so that the side surface of the end of the sample contacts the side surface of the positioning anti-reverse structure II 203 of the left lower side clamp 201. Subsequently, under the sliding cooperation of the rolling element with the lower groove 205 and the buckling groove II 303 respectively, the left lower side clamp 2 01 and the top end surface of the right lower side clamp 202 can be in sliding contact with the plane of the anti-buckling plate 3 provided with the buckling slide groove II 303, so that the anti-buckling plate 3 can slide relative to the lower clamp 2. Finally, the inner surface of the right lower side clamp 202 is aligned and fitted with the inner surface of the left lower side clamp 201, so that the other side surface of the end of the sample is in contact with the side surface of the positioning anti-reverse structure II 203 of the right lower side clamp 202. At the same time, the bolt II is screwed into the threaded hole II 204 to fasten the end of the sample in the clamping channel II.

[0058] Step S3: In step S2, the two ends of the sample are clamped by the upper clamp 1 and the lower clamp 2 respectively, and the middle part of the sample is located in the sample position gap 301 of the anti-buckling plate 3, and then the low-cycle fatigue test of the sample is started; when the testing machine is used to apply displacement loads to the upper clamp 1 and the lower clamp 2 for compression, the upper clamp 1 and the lower clamp 2 are displaced in the form of gradually approaching each other. When the distance between the upper clamp 1 and the lower clamp 2 is gradually reduced, the anti-buckling plate 3 will move in the direction away from the connecting column Ⅰ107 under the sliding action of the upper slider 106 and the buckling groove Ⅰ302, the rolling element and the lower groove 205 and the buckling groove Ⅱ303. In this process, the anti-buckling plate 3 only undergoes lateral displacement. When the upper clamp 1 and the lower clamp 2 are respectively applied with displacement loads by the testing machine for stretching, the upper clamp 1 and the lower clamp 2 are displaced in the form of gradually moving away from each other. When the distance between the upper clamp 1 and the lower clamp 2 gradually increases, the tension spring 304 drives the anti-buckling plate 3 and moves toward the direction close to the connecting column Ⅰ107 under the sliding action of the upper slider 106 and the buckling groove Ⅰ302, the rolling element and the lower slide groove 205 and the buckling groove Ⅱ303. During this process, the anti-buckling plate 3 also only undergoes lateral displacement, which ensures that the coaxiality of the sample will not deviate during the test, resulting in test failure.

[0059] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low cycle fatigue test device for metal sheets used in LNG membrane tanks, characterized in that: It includes an upper clamp, a lower clamp and an anti-buckling plate which is slidably matched with the upper clamp and the lower clamp respectively; The upper clamp has the function of clamping one end of the sample. The upper clamp includes a left upper side clamp and a right upper side clamp arranged in contact with the left upper side clamp. The surfaces of the left upper side clamp and the right upper side clamp that are in contact with each other are provided with a positioning anti-reverse structure I. A plurality of threaded holes I are provided through the surface of the upper clamp. The left upper side clamp and the right upper side clamp are fastened together by the cooperation of bolts I and threaded holes I. An upper slider is provided on the bottom end surface of the upper clamp, and a connecting column I is provided on the outer end surface of the upper clamp. The lower clamp has the function of clamping the other end of the sample. The lower clamp includes a left lower side clamp and a right lower side clamp arranged in contact with the lower side clamp. The surfaces of the left lower side clamp and the right lower side clamp that are in contact with each other are provided with a positioning anti-reverse structure II. A plurality of threaded holes II are provided through the surface of the lower clamp. The left lower side clamp and the right lower side clamp are fastened together by the cooperation of bolts II and threaded holes II. A sliding groove is provided on the top surface of the lower clamp. The shape of the anti-buckling plate is set to be a wedge-shaped structure, a specimen position gap is opened inside it, a buckling groove I is opened on the upper side end face of the anti-buckling plate, which can slide with the upper slider set on the bottom end face of the upper clamp, a buckling groove II is opened on the bottom end face of the anti-buckling plate, which can slide with the lower sliding groove opened on the top end face of the lower clamp through a rolling member, and a connecting column II is set on the outer side end face of the anti-buckling plate, which is connected to the connecting column I through a tension spring.

2. A low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: The positioning and anti-rebound structure I includes an A-type positioning and anti-rebound structure and a B-type positioning and anti-rebound structure. The A-type positioning and anti-rebound structure is located on the inner surface of one of the tip parts of the upper right side clamp, and the B-type positioning and anti-rebound structure is located on the inner surface of one of the edge parts of the upper left side clamp. The arrangement of the A-type positioning and anti-rebound structure and the B-type positioning and anti-rebound structure enables the upper left side clamp and the upper right side clamp to form a clamping channel I for clamping one end of the sample when they are fitted together; the number of the threaded holes I is three, one of which is penetrated from the outer surface of the upper left side clamp through the A-type positioning and anti-rebound structure located on the upper right side clamp to the outer surface of the upper right side clamp, and the remaining two threaded holes I are penetrated from the outer surface of the upper left side clamp through the B-type positioning and anti-rebound structure located on the upper left side clamp to the outer surface of the upper right side clamp, and the relative positions of the upper left side clamp and the upper right side clamp are fixed by the cooperation of the bolt I and the threaded hole I.

3. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: There are two upper sliding blocks, which are symmetrically arranged on the bottom inclined surfaces of the left upper side clamp and the right upper side clamp.

4. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: The same end sides of the lower left side clamp and the lower right side clamp are both provided with a positioning and anti-reverse structure II. When the planes of the lower left side clamp and the lower right side clamp provided with the positioning and anti-reverse structure II are relative and fitted together, a clamping channel II for clamping the other end of the sample will be formed; the number of the threaded holes II is two, one of which is penetrated from the outer surface of the lower left side clamp through the positioning and anti-reverse structure II located on the lower right side clamp to the outer surface of the lower right side clamp, and the remaining threaded hole II is penetrated from the outer surface of the lower left side clamp through the positioning and anti-reverse structure II located on the lower left side clamp to the outer surface of the lower right side clamp.

5. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: The number of the sliding grooves is two, which are symmetrically arranged on the top surfaces of the left lower side clamp and the right lower side clamp respectively.

6. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: The sample position gap is opened from the tip of the anti-buckling plate on the right side toward the end on the left side thereof, the width of the sample position gap is not less than the thickness of the sample, and a polytetrafluoroethylene sheet is arranged on the surface of the sample position gap.

7. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: There are two buckling grooves I and II, which are respectively opened on the left and right sides of the specimen position gap. Buckling groove I is opened on the upper end surface of the anti-buckling plate in a direction parallel to the specimen position gap, and the opening direction of buckling groove II on the bottom end surface of the anti-buckling plate is the same as the opening direction of the lower groove.

8. The low cycle fatigue testing device for metal sheets used in LNG membrane tanks according to claim 1, characterized in that: The connecting column I is arranged on the outer surface of the right upper side clamp, and the connecting column II is arranged on the outer surface of the anti-buckling plate on the same side as the connecting column I.

9. A method for using a metal sheet low cycle fatigue test device, the method being applied to a metal sheet low cycle fatigue test device for LNG membrane tanks as claimed in any one of claims 1 to 8, characterized in that: The specific steps include: Step S1: First, screw out the bolt I at the threaded hole I of the upper clamp from the threaded hole I, so that the upper left side clamp of the upper clamp is separated from the upper right side clamp, then place the side surface of one end of the sample on the inner surface of the upper left side clamp, so that the side surface of the end of the sample contacts the side surface of the B-type positioning anti-reverse structure of the upper left side clamp, and at the same time, move the anti-buckling plate at an angle parallel to the sample, so that the middle part of the sample enters the sample position gap of the anti-buckling plate, and then, the upper sliders of the upper left side clamp and the upper right side clamp are respectively engaged with the buckling groove I set on the upper end surface of the anti-buckling plate. The upper clamp is connected to the specimen by the upper slider and the buckling groove I, so that the anti-buckling plate can slide relative to the upper clamp under the action of the upper slider and the buckling groove I. Finally, the inner surface of the upper right clamp is aligned with the inner surface of the upper left clamp, so that the other side surface of the end of the specimen is in contact with the side surface of the A-type positioning anti-reverse structure of the upper right clamp. At the same time, the bolt I is screwed into the threaded hole I to fasten the end of the specimen in the clamping channel I. At this time, the tension spring connected to the connecting column I and the connecting column II can ensure that the upper clamp and the anti-buckling plate are in close contact when sliding relative to each other under the action of its elastic force. Step S2: In step S1, the bolt II at the threaded hole II of the lower clamp is screwed out from the threaded hole II, so that the lower left side clamp and the lower right side clamp of the lower clamp are separated, and then, the side surface of the other end of the sample is placed on the inner surface of the left lower side clamp, so that the side surface of the end of the sample contacts the side surface of the positioning anti-reverse structure II of the left lower side clamp, and then, under the sliding cooperation of the rolling element with the lower slide groove and the buckling slide groove II respectively, the top end surface of the left lower side clamp and the right lower side clamp can slide in contact with the plane of the anti-buckling plate provided with the buckling slide groove II, so that the anti-buckling plate can slide relative to the lower clamp, and finally, the inner surface of the right lower side clamp is aligned and fitted with the inner surface of the left lower side clamp, so that the other side surface of the end of the sample contacts the side surface of the positioning anti-reverse structure II of the right lower side clamp, and at the same time, the bolt II is screwed into the threaded hole II to fasten the end of the sample in the clamping channel II; Step S3: In step S2, the two ends of the sample are clamped by the upper clamp and the lower clamp respectively, and after the middle of the sample is located in the sample position gap of the anti-buckling plate, the low-cycle fatigue test of the sample is started; when the testing machine is used to apply displacement loads to the upper clamp and the lower clamp for compression, the upper clamp and the lower clamp are displaced in a gradually approaching form, and when the distance between the upper clamp and the lower clamp is gradually reduced, the anti-buckling plate will move in a direction away from the connecting column I under the sliding action of the upper slider and the buckling chute I, the rolling element and the lower chute and the buckling chute II, and in this process, the anti-buckling plate only undergoes lateral displacement. , which can prevent the specimen from having coaxial deviation during the test; when the testing machine is used to apply displacement loads to the upper fixture and the lower fixture for stretching, the upper fixture and the lower fixture are displaced in the form of gradually moving away from each other. When the distance between the upper fixture and the lower fixture gradually increases, the tension spring drives the anti-buckling plate and moves towards the direction close to the connecting column Ⅰ under the sliding action of the upper slider and the buckling groove Ⅰ, the rolling element and the lower groove and the buckling groove Ⅱ. In this process, the anti-buckling plate also only undergoes lateral displacement, which ensures that the specimen will not have coaxial deviation during the test, resulting in test failure.

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