A low cycle fatigue test device for metal sheet of LNG film tank and a method of using the same

Abstract

The application discloses a metal sheet low-cycle fatigue test device for LNG film tanks and a use method thereof. The device comprises an upper clamp, a lower clamp and a buckling-restraining plate in sliding cooperation with the upper clamp and the lower clamp respectively. In the application, the upper clamp and the lower clamp are in sliding cooperation with the buckling-restraining plate respectively, so that the upper clamp and the lower clamp are in sliding contact with the buckling-restraining plate respectively, zero gap is ensured between the contact surfaces of the upper clamp, the lower clamp and the buckling-restraining plate, and the test sample is prevented from being bent at the contact surface positions of the upper clamp and the buckling-restraining plate and the lower clamp and the buckling-restraining plate, so that the invalid test is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material and industrial product fatigue performance testing, and particularly relates to a low-cycle fatigue test device for metal sheet of LNG membrane tank and a use method thereof. BACKGROUND

[0002] As an important material in the structure of LNG membrane tank, the performance of the metal sheet attracts extensive attention. Under actual working conditions, the metal sheet is subjected to continuous cyclic loading, and therefore, investigating the fatigue performance index, especially the low-cycle fatigue performance index, of the metal sheet has important guiding significance for the design of the LNG membrane tank structure. However, the thickness direction size of the metal sheet is small, has a large slenderness ratio, and has small stiffness, and when subjected to tensile-compressive cyclic loading, the metal sheet is prone to lateral buckling instability in the thickness direction. Therefore, in the strain-controlled low-cycle fatigue test of the metal sheet, preventing buckling instability to obtain reliable test data becomes a technical problem to be solved urgently.

[0003] In the prior art, the authorized announcement CN102735557B discloses a vehicle body sheet fatigue test device and test method, and the application number CN200620012080.3 discloses a metal sheet axial tensile-compressive fatigue test anti-buckling clamp. When the above prior art is used to install the sample, a gap exists between the anti-buckling device and the test machine clamp, that is, the clamped end of the sample has a part that is not constrained in any way. The unconstrained part of the sample is also in a plane stress state during the fatigue test, and therefore, the sample is prone to bending at this part, which leads to invalid test. The authorized announcement CN111766162B discloses an automobile sheet strain fatigue test device and method, and the publication CN115753382A discloses a method for fatigue test of plate-shaped material. When the above prior art is used to install the sample, the sample and the split anti-buckling device need to be fixed by screwing the bolts. If the torque of the bolts is not balanced when the bolts are tightened, a slight misalignment will occur between the anti-buckling device and the sample, which leads to a deviation in the coaxiality between the two, and thus affects the accuracy of the subsequent fatigue test results. SUMMARY

[0004] In view of this, the purpose of the present application is to provide a kind of metal sheet low-cycle fatigue test device for LNG membrane tank, which can solve the technical problems that there is gap between buckling prevention device and testing machine clamp in prior art, so that the sample part located at the gap is prone to bending phenomenon, resulting in invalid test, it can also solve the technical problems that torque imbalance between each connecting component occurs when using split buckling prevention device in prior art, resulting in deviation of coaxiality between buckling prevention device and sample, thereby affecting the accuracy of subsequent fatigue test results, and the present application also provides a kind of use method of metal sheet low-cycle fatigue test device, which is applied to a kind of metal sheet low-cycle fatigue test device for LNG membrane tank.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A kind of metal sheet low-cycle fatigue test device for LNG membrane tank, it includes upper clamp, lower clamp and the buckling prevention plate that is slidably connected with upper clamp and lower clamp respectively;

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

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

[0009] The shape of the buckling prevention plate is set as a wedge structure, and a sample position gap is provided in the interior of the buckling prevention plate, a buckling sliding groove I is provided on the upper side surface of the buckling prevention plate, which can be slidably connected with the upper sliding block provided on the bottom surface of the upper clamp, a buckling sliding groove II is provided on the bottom surface of the buckling prevention plate, which can be slidably connected with the lower sliding groove provided on the top surface of the lower clamp through a rolling element, and a connecting column II connected with the connecting column I through a tension spring is provided on the outer side surface of the buckling prevention plate.

[0010] Further, the positioning anti-reverse structure I includes an A-type positioning anti-reverse structure and a B-type positioning anti-reverse structure, the A-type positioning anti-reverse structure is located at the inner surface of one of the tip positions of the right upper clamp, the B-type positioning anti-reverse structure is located at the inner surface of one of the edge positions of the left upper clamp, the A-type positioning anti-reverse structure and the B-type positioning anti-reverse structure are arranged so that the left upper clamp and the right upper clamp 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 the threaded holes I is penetrated from the outer surface of the left upper clamp to the outer surface of the right upper clamp through the A-type positioning anti-reverse structure of the right upper clamp, and the remaining two threaded holes I are penetrated from the outer surface of the left upper clamp to the outer surface of the right upper clamp through the B-type positioning anti-reverse structure of the left upper clamp, and the relative positions of the left upper clamp and the right upper clamp are fixed by the cooperation of the bolts I and the threaded holes I.

[0011] Further, the number of the upper sliding blocks is two, which are arranged in a symmetrical manner at the bottom end bevels of the left upper clamp and the right upper clamp.

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

[0013] Further, the number of the lower sliding grooves is two, which are arranged in a symmetrical manner at the top end surfaces of the left lower clamp and the right lower clamp.

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

[0015] Further, the sample position gap is opened from the tip position on the right side of the anti-buckling plate to 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] Further, the surface of the sample position gap is provided with a polytetrafluoroethylene sheet.

[0017] Further, the number of the buckling sliding grooves I and the buckling sliding grooves II is two, which are arranged on the left and right sides of the sample position gap, respectively, the buckling sliding 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 opening direction of the buckling sliding groove II on the bottom end surface of the anti-buckling plate is the same as that of the lower sliding groove.

[0018] Further, the connecting column I is arranged on the outer surface of the right upper 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 application further provides a use method of the metal sheet low-cycle fatigue test device.

[0020] Step S1: first, unscrew the bolt I from the threaded hole I, so that the left upper clamp and the right upper clamp of the upper clamp are separated, then place one end surface of the sample in the inner surface of the left upper clamp, so that the end surface of the sample contacts the side surface of the B-shaped positioning anti-reverse structure of the left upper clamp, and 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, then connect the upper sliding block of the left upper clamp and the right upper clamp with the buckling sliding groove I arranged on the upper end surface of the anti-buckling plate, so that the anti-buckling plate can slide relative to the upper clamp under the action of the upper sliding block and the buckling sliding groove I, finally, align the inner surface of the right upper clamp with the inner surface of the left upper clamp, so that the other end surface of the sample contacts the side surface of the A-shaped positioning anti-reverse structure of the right upper clamp, and screw the bolt I into the threaded hole I to fasten the end of the sample in the clamping channel I, at this time, the tension spring connected with the connecting column I and the connecting column II can ensure that the upper clamp and the anti-buckling plate still maintain close contact when sliding relative to each other under the action of the elastic force of the tension spring;

[0021] Step S2: in step S1, unscrew the bolt II from the threaded hole II of the lower clamp, so that the left lower clamp and the right lower clamp of the lower clamp are separated, then place the side surface of the other end of the sample in the inner surface of the left lower clamp, so that the end surface of the sample contacts the side surface of the positioning anti-reverse structure II of the left lower clamp, then under the sliding cooperation of the rolling element and the lower sliding groove and the buckling sliding groove II, the top end surface of the left lower clamp and the right lower clamp can slide in contact with the plane of the anti-buckling plate provided with the buckling sliding groove II, so that the anti-buckling plate can slide relative to the lower clamp, finally, align the inner surface of the right lower clamp with the inner surface of the left lower clamp, so that the other end surface of the sample contacts the side surface of the positioning anti-reverse structure II of the right lower clamp, and screw the bolt II 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 part 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 test machine applies displacement load to the upper clamp and the lower clamp respectively for compression, the upper clamp and the lower clamp displace in the form of gradually approaching, and under the condition that the distance between the upper clamp and the lower clamp gradually decreases, the anti-buckling plate acts away from the connecting column I under the sliding action of the upper sliding block and the buckling sliding groove I, the rolling piece and the lower sliding groove and the buckling sliding groove II, in this process, the anti-buckling plate only has lateral displacement, which can prevent the sample from producing deviation of coaxiality in the test process; when the test machine applies displacement load to the upper clamp and the lower clamp respectively for stretching, the upper clamp and the lower clamp displace in the form of gradually moving away, and under the condition that the distance between the upper clamp and the lower clamp gradually increases, the tension spring drives the anti-buckling plate and acts towards the connecting column I under the sliding action of the upper sliding block and the buckling sliding groove I, the rolling piece and the lower sliding groove and the buckling sliding groove II, in this process, the anti-buckling plate also only has lateral displacement, which ensures that the sample will not produce deviation of coaxiality in the test process, so that the test failure does not occur.

[0023] Compared with the prior art, the technical scheme disclosed by the application has the following beneficial effects:

[0024] 1、The application has the characteristics of reasonable structure design, strong practicability, convenient use and the like, and the sliding cooperation between the upper clamp, the lower clamp and the anti-buckling plate in the application enables the upper clamp, the lower clamp and the anti-buckling plate to realize sliding contact, ensures zero gap between the contact surfaces of the upper clamp, the lower clamp and the anti-buckling plate, and prevents the sample from being bent at the contact surface positions of the upper clamp and the anti-buckling plate and the lower clamp and the anti-buckling plate, so that the test invalidation does not occur.

[0025] 2、The integral design of the anti-buckling plate in the application not only omits the step of alignment and installation in the test process, but also increases the rigidity of the anti-buckling plate, avoids the deformation of the middle part of the anti-buckling plate in the test process, guarantees the accuracy of the test, effectively prevents the induction of the fatigue crack source of the sample, increases the service life of the sample, and reduces the error of the test.

[0026] 3、The buckling sliding groove I and the buckling sliding groove II symmetrically arranged at the sample position gap in the application enable the anti-buckling plate to align and slide with the upper clamp and the lower clamp, guarantee the coaxiality of the anti-buckling plate and the sample, and prevent the anti-buckling plate from being misaligned with the sample, which affects the accuracy of the subsequent fatigue test result.

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

[0028] The application will be further described below in conjunction with the drawings and specific embodiments,

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

[0030] Figure 2 It is a schematic diagram of the structure of the upper clamp of the application;

[0031] Figure 3 It is a schematic diagram of the structure of the left upper clamp of the upper clamp of the application;

[0032] Figure 4 It is a schematic diagram of the structure of the right upper clamp of the upper clamp of the application A;

[0033] Figure 5 It is a schematic diagram of the structure of the right upper clamp of the upper clamp of the application B;

[0034] Figure 6 It is a schematic diagram of the structure of the lower clamp of the application;

[0035] Figure 7 It is a schematic diagram of the structure of the left lower clamp of the lower clamp of the application;

[0036] Figure 8 It is a schematic diagram of the structure of the right lower clamp of the lower clamp of the application;

[0037] Figure 9 It is a schematic diagram of the structure of the buckling-restrained plate of the application;

[0038] 1, upper clamp; 101, left upper clamp, 102, right upper clamp; 103, A type positioning anti-reverse structure; 104, B type positioning anti-reverse structure; 105, threaded hole I; 106, upper sliding block; 107, connecting column I; 2, lower clamp; 201, left lower clamp; 202, right lower clamp; 203, positioning anti-reverse structure II; 204, threaded hole II; 205, lower sliding groove; 3, buckling-restrained plate; 301, sample position gap; 302, buckling sliding groove I; 303, buckling sliding groove II; 304, tension spring; 305, connecting column II. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0040] As Figures 1 to 9 shown, the application provides a metal sheet low-cycle fatigue test device for an LNG film tank,

[0041] It includes upper clamp 1, lower clamp 2 and anti-buckling plate 3 respectively with upper clamp 1, lower clamp 2 sliding fit;

[0042] The upper clamp 1 has the effect of clamping one end of the sample, the upper clamp 1 includes left upper clamp 101 and right upper clamp 102 arranged in close contact with it, the mutually close surfaces between the left upper clamp 101 and the right upper clamp 102 are provided with positioning anti-reverse structure I, a plurality of threaded holes I 105 are provided on the surface of the upper clamp 1, and the left upper clamp 101 and the right upper clamp 102 are fastened together through the cooperation of the bolts I and the threaded holes I 105, the bottom end surface of the upper clamp 1 is provided with an upper sliding block 106, and the outer side end surface of the upper clamp 1 is provided with a connecting column I 107;

[0043] The lower clamp 2 has the effect of clamping the other end of the sample, the lower clamp 2 includes left lower clamp 201 and right lower clamp 202 arranged in close contact with it, the mutually close surfaces between the left lower clamp 201 and the right lower clamp 202 are provided with positioning anti-reverse structure II 203, a plurality of threaded holes II 204 are provided on the surface of the lower clamp 2, and the left lower clamp 201 and the right lower clamp 202 are fastened together through the cooperation of the bolts II and the threaded holes II 204, and the top end surface of the lower clamp 2 is provided with a lower sliding groove 205;

[0044] The shape of the anti-buckling plate 3 is set as a wedge structure, the inside of which is provided with a sample position gap 301, the upper side end surface of the anti-buckling plate 3 is provided with a buckling sliding groove I 302, which can be in sliding fit with the upper sliding block 106 arranged on the bottom end surface of the upper clamp 1, the bottom end surface of the anti-buckling plate 3 is provided with a buckling sliding groove II 303, which can be in sliding fit with the lower sliding groove 205 provided on the top end surface of the lower clamp 2 through a rolling piece, and the outer side end surface of the anti-buckling plate 3 is provided with a connecting column II 305 connected with the connecting column I 107 through a tension spring 304;

[0045] In the embodiment of the present application, the positioning anti-reverse structure I has a function of determining the relative position between the left upper clamp 101 and the right upper clamp 102, avoiding the installation error of the left upper clamp 101 and the right upper clamp 102, and the positioning anti-reverse structure I comprises an A-type positioning anti-reverse structure 103 and a B-type positioning anti-reverse structure 104, the A-type positioning anti-reverse structure 103 is located on the inner surface of one of the tip positions of the right upper clamp 102, and the B-type positioning anti-reverse structure 104 is located on the inner surface of one of the edge positions of the left upper clamp 101, the arrangement of the A-type positioning anti-reverse structure 103 and the B-type positioning anti-reverse structure 104 makes the left upper clamp 101 and the right upper clamp 102 form a clamping channel I for clamping one end of the sample when they are fitted together, and the end of the sample in the clamping channel I can avoid displacement relative to the upper clamp 1 during the test, thereby ensuring the height coaxiality between the clamped position of the sample and the upper clamp 1 during the test; the number of the threaded holes I 105 is three, one of the threaded holes I 105 is formed by penetrating the outer surface of the left upper clamp 101 through the A-type positioning anti-reverse structure 103 of the right upper clamp 102 to the outer surface of the right upper clamp 102, and the remaining two threaded holes I 105 are formed by penetrating the outer surface of the left upper clamp 101 through the B-type positioning anti-reverse structure 104 of the left upper clamp 101 to the outer surface of the right upper clamp 102, and the relative position of the left upper clamp 101 and the right upper clamp 102 is fixed by cooperating the threaded holes I 105 with the bolts I;

[0046] In the embodiment of the present application, the number of the upper sliding blocks 106 is two, which are arranged in a symmetrical manner at the bottom end bevels of the left upper clamp 101 and the right upper clamp 102, and under the sliding cooperation of the flexion sliding grooves I 302 and the upper sliding blocks 106, the bottom end surfaces of the left upper clamp 101 and the right upper clamp 102 can slide with the plane of the flexion sliding grooves I 302 of the anti-flexion plate 3, so as to ensure the zero gap between the contact surfaces of the upper clamp 1 and the anti-flexion plate 3, and prevent the sample from being bent at the contact surface position of the upper clamp 1 and the anti-flexion plate 3, thereby avoiding the invalid test;

[0047] In the embodiment of the present application, the same end side of the left lower clamp 201 and the right lower clamp 202 is provided with a positioning anti-reverse structure II 203, when the planes provided with the positioning anti-reverse structure II 203 of the left lower clamp 201 and the right lower clamp 202 are opposite and adhere to each other, a clamping channel II for clamping the other end of the sample is formed, the other end of the sample in the clamping channel II can avoid displacement of the end of the sample relative to the lower clamp 2 during the test, and the height coaxiality between the clamped part of the sample and the lower clamp 2 during the test is ensured; the number of the threaded holes II 204 is two, one threaded hole II 204 is penetrated from the outer surface of the left lower clamp 201 to the outer surface of the right lower clamp 202 through the positioning anti-reverse structure II 203 of the right lower clamp 202, and the remaining threaded hole II 204 is penetrated from the outer surface of the left lower clamp 201 to the outer surface of the right lower clamp 202 through the positioning anti-reverse structure II 203 of the left lower clamp 201, and the relative position of the left lower clamp 201 and the right lower clamp 202 is fixed by cooperation of the bolt II and the threaded hole II 204;

[0048] In the embodiment of the present application, the lower chute 205 is provided in a symmetrical form at the top end surface of the left lower clamp 201 and the right lower clamp 202, and under the sliding cooperation of the rolling members and the lower chute 205 and the bending sliding groove II 303, the top end surface of the left lower clamp 201 and the right lower clamp 202 can be in sliding contact with the plane provided with the bending sliding groove II 303 of the anti-buckling plate 3, 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 sample from being bent at the contact surface position of the lower clamp 2 and the anti-buckling plate 3, so as to cause invalid test;

[0049] Preferably, the rolling member is a ball, so as 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 application, the inclination degree of the bottom end surface of the upper clamp 1 is not further limited, and correspondingly, the inclination degree of the plane of the anti-buckling plate 3 in sliding contact with the bottom end surface of the upper clamp 1 is also 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, which is within the protection scope of the present application; in the present application, 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), and correspondingly, 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, so as to ensure zero gap between the contact surfaces of the upper clamp 1 and the anti-buckling plate 3, and also ensure zero gap between the contact surfaces of the lower clamp 2 and the anti-buckling plate 3;

[0051] In the embodiment of the present application, the sample position gap 301 is opened from the right tip of the anti-buckling plate 3 to the left end, 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 in close contact with the upper clamp 1 and the lower clamp 2 at all times, to ensure the accuracy and precision of the test, and the anti-buckling plate 3 is designed in one piece, which not only omits the step of aligning and installing during the test, but also increases the rigidity of the anti-buckling plate 3, avoiding the deformation of the middle part of the anti-buckling plate 3 during the test, ensuring the accuracy of the test, effectively preventing the induction of fatigue crack sources of the sample, increasing the service life of the sample, and reducing 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 application, the surface of the sample position gap 301 is provided with a polytetrafluoroethylene sheet, the friction coefficient of the polytetrafluoroethylene sheet is extremely low, and the arrangement of the polytetrafluoroethylene sheet can reduce the friction between the surface of the sample position gap 301 and the sample, to ensure smooth sliding between the anti-buckling plate 3 and the sample;

[0053] In the embodiment of the present application, the number of the buckling sliding grooves I 302 and the buckling sliding grooves II 303 is two, which are respectively arranged on the left and right sides of the sample position gap 301, the buckling sliding grooves I 302 are arranged on the upper end surface of the anti-buckling plate 3 in a direction parallel to the sample position gap 301, and the buckling sliding grooves II 303 are arranged on the bottom end surface of the anti-buckling plate 3 in the same direction as the lower sliding groove 205; the buckling sliding grooves I 302 and the buckling sliding grooves II 303 arranged symmetrically relative to the sample position gap 301 in the present application can make the anti-buckling plate 3 slide in alignment with the upper clamp 1 and the lower clamp 2, to ensure the coaxiality of the anti-buckling plate 3 and the sample, and prevent misalignment between the anti-buckling plate 3 and the sample, which affects the accuracy of the subsequent fatigue test results;

[0054] In the embodiment of the present application, the connecting column I 107 is arranged on the outer surface of the upper right 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, which can ensure that the upper clamp 1 and the anti-buckling plate 3 are in close contact when they slide relative to each other under the elastic force of the tension spring 304;

[0055] The present application also provides a use method of the metal sheet low-cycle fatigue test device, which is applied to the above-mentioned LNG thin film tank metal sheet low-cycle fatigue test device, and the specific steps include:

[0056] Step S1: First, the bolt I at the threaded hole I 105 of the upper clamp 1 is unscrewed from the threaded hole I 105, so that the left upper clamp 101 and the right upper clamp 102 of the upper clamp 1 are separated, then the side surface of one end of the sample is placed on the inner side surface of the left upper clamp 101, so that the side surface of the end of the sample is in contact with the side surface of the B-shaped positioning anti-reverse structure 104 of the left upper clamp 101, and the anti-buckling plate 3 is moved 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, then the upper sliding block 106 of the left upper clamp 101 and the right upper clamp 102 is respectively connected with the buckling sliding groove I 302 arranged on the upper end surface of the anti-buckling plate 3, so that the anti-buckling plate 3 can slide relative to the upper clamp 1 under the action of the upper sliding block 106 and the buckling sliding groove I 302, and finally, the inner side surface of the right upper clamp 102 is aligned and attached to the inner side surface of the left upper clamp 101, so that the other side surface of the end of the sample is in contact with the side surface of the A-shaped positioning anti-reverse structure 103 of the right upper clamp 102, and the bolt I is screwed into the threaded hole I 105 to fasten the end of the sample in the clamping channel I. At this time, the tension spring 304 connected with the connecting column I 107 and the connecting column II 305 can ensure that the upper clamp 1 and the anti-buckling plate 3 still maintain close contact when they slide relative to each other under the action of the elastic force of the tension spring 304;

[0057] Step S2: In step S1, the bolt II at the threaded hole II 204 of the lower clamp 2 is unscrewed from the threaded hole II 204, so that the left lower clamp 201 and the right lower 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 side surface of the left lower clamp 201, so that the 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 left lower clamp 201, then under the sliding cooperation of the rolling members with the lower sliding groove 205 and the buckling sliding groove II 303, the top end surface of the left lower clamp 201 and the right lower clamp 202 can slide in contact with the plane of the buckling sliding groove II 303 arranged on the anti-buckling plate 3, so that the anti-buckling plate 3 can slide relative to the lower clamp 2, and finally, the inner side surface of the right lower clamp 202 is aligned and attached to the inner side surface of the left lower 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 clamp 202, and 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 after the middle part of the sample is located in the sample position gap 301 of the anti-buckling plate 3, the low cycle fatigue test of the sample is started; when the test machine is used to apply displacement load 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, and under the condition that the distance between the upper clamp 1 and the lower clamp 2 gradually decreases, the anti-buckling plate 3 will act in the direction away from the connecting column 107 under the sliding action of the upper sliding block 106 and the buckling sliding groove 302, the rolling member and the lower sliding groove 205 and the buckling sliding groove 303, in this process, the anti-buckling plate 3 only has transverse displacement, which can prevent the sample from producing deviation of coaxiality in the test process; when the test machine is used to apply displacement load to the upper clamp 1 and the lower clamp 2 for stretching, the upper clamp 1 and the lower clamp 2 are displaced in the form of gradually moving away, under the condition that 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 acts in the direction close to the connecting column 107 under the sliding action of the upper sliding block 106 and the buckling sliding groove 302, the rolling member and the lower sliding groove 205 and the buckling sliding groove 303, in this process, the anti-buckling plate 3 also only has transverse displacement, which ensures that the sample will not produce deviation of coaxiality in the test process, so that the test failure occurs.

[0059] Finally, it should be pointed out that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the present application is described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

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

2. The 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 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; there are three threaded holes I, 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 bolts I and threaded holes 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 respectively.

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 side of the lower left side clamp and the lower right side clamp are both provided with a positioning and anti-rebound structure II. When the planes of the lower left side clamp and the lower right side clamp provided with the positioning and anti-rebound structure II are relative and fitted together, a clamping channel II for clamping the other end of the sample will be formed; there are two threaded holes II, one of which is provided from the outer surface of the lower left side clamp through the positioning and anti-rebound 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 provided from the outer surface of the lower left side clamp through the positioning and anti-rebound 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: There are two lower sliding grooves, 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. A polytetrafluoroethylene sheet is provided 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 chutes I and buckling chutes II, which are respectively opened on the left and right sides of the sample position gap. Buckling chute I is opened on the upper end surface of the anti-buckling plate in a direction parallel to the sample position gap, and the opening direction of buckling chute II on the bottom end surface of the anti-buckling plate is the same as the opening direction of the lower chute.

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 testing device, the method being applied to a metal sheet low cycle fatigue testing device for LNG membrane tanks according to 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. 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. Subsequently, the upper sliders of the upper left side clamp and the upper right side clamp are respectively engaged with the buckling groove I provided on the upper end surface of the anti-buckling plate. The connection is made so that the anti-buckling plate can slide relative to the upper clamp under the action of the upper slider and the buckling slide 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 this end of the specimen contacts the side surface of the A-type positioning and anti-reverse structure of the upper right clamp. At the same time, bolt I is screwed into threaded hole I to fasten this end of the specimen in clamping channel I. At this time, the tension spring connected to connecting column I and connecting column II can ensure that the upper clamp and the anti-buckling plate maintain 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 left lower side clamp and the right lower side clamp of the lower clamp are separated. Then, the side surface of the other end of the specimen is placed on the inner surface of the left lower side clamp, so that the side surface of the end of the specimen contacts the side surface of the positioning and anti-reverse structure II of the left lower side clamp. Subsequently, under the sliding cooperation of the rolling element with the lower slide groove and the buckling slide groove II respectively, the top end surfaces 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. 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 specimen contacts the side surface of the positioning and anti-reverse structure II of the right lower side clamp. At the same time, the bolt II is screwed into the threaded hole II to fasten the end of the specimen 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 the middle part of the sample is located in the sample position gap of the anti-buckling plate, 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 and the lower clamp respectively for compression, the upper clamp and the lower clamp are displaced in the form of gradually approaching each other. When the distance between the upper clamp and the lower clamp gradually decreases, the anti-buckling plate will move in the 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. During this process, the anti-buckling plate only undergoes lateral displacement. , which can prevent the specimen from producing coaxial deviation during the test; when the testing machine is used to apply displacement loads to the upper clamp and the lower clamp for stretching, the upper clamp and the lower clamp are displaced in the form of gradually moving away from each other. When the distance between the upper clamp and the lower clamp 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 chute I, the rolling element and the lower chute and the buckling chute II. During this process, the anti-buckling plate also only undergoes lateral displacement, ensuring that the specimen will not produce coaxial deviation during the test, which will lead to test failure.

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