Method for testing rivet peel performance of low elongation aluminum alloy to steel sheet

Abstract

The application relates to a riveting peeling performance test method for a low-elongation aluminum alloy and a steel plate, which comprises the following steps: a riveting joint mechanical peeling test sample and a riveting joint mechanical peeling test device are prepared and assembled to form a test assembly; the holding end of the test assembly is clamped on a tensile testing machine, and test program parameters are set; the test program is started until peeling damage occurs at the riveting point to be tested, and the maximum peeling force of a single riveting joint is recorded; the peeling strength of the riveting joint is calculated according to a formula; the peeling strength test result is judged for qualification, the maximum peeling force of several riveting joint mechanical peeling test samples is randomly evaluated under the process, and if the test results are all greater than the peeling strength of the riveting joint, the result is determined to be qualified; otherwise, the result is determined to be unqualified; the application avoids the problems of great difficulty, high cost and long cycle caused by the preparation of aluminum profiles, die-casting aluminum mechanical peeling samples and special molds.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of riveting test, in particular to a riveting peeling performance test method for low-elongation aluminum alloy and steel plate. BACKGROUND

[0002] With the increasing development of lightweight of automobile, more and more structural parts of automobile body are made of aluminum profiles, die-cast aluminum and other materials. When these structural parts are connected with the surrounding steel parts, the connection between steel and aluminum and other dissimilar materials is inevitable. For the connection between steel and aluminum dissimilar materials, due to the problems of interface brittle phase, electrochemical corrosion, easy to produce deformation and internal stress at the joint, the connection strength is generally low, which limits its application to some extent. Riveting, especially self-piercing riveting (SPR) and hot melt self-tapping riveting (FDS), combined with appropriate structural adhesive materials, can effectively solve the above technical difficulties, but also bring new technical problems. As we all know, the strength evaluation of automobile body connection joint generally needs to carry out tensile shear, L-type mechanical peeling and other strength tests to master the comprehensive bearing and stress conditions. For tensile shear strength test, there are perfect process, standard and test means. But for the riveted joint formed by aluminum profiles, die-cast aluminum and automobile body steel plate, due to the low elongation of aluminum profiles, die-cast aluminum, it cannot be bent at 90 degrees, so the L-type mechanical peeling strength test cannot be carried out. Although the corresponding mechanical peeling connection aluminum profile, die-cast aluminum L-type 90-degree bending piece can be prepared by opening the mold and using extrusion, casting and other methods, and then connected with the corresponding bent steel plate sample, and then the subsequent mechanical peeling strength test is completed. But this will also lead to a substantial increase in manufacturing cost and processing cycle. In order to solve the above problems, a new kind of general test sample, device and detection evaluation method for mechanical peeling of riveted joint between low elongation aluminum alloy and steel plate is needed to be developed to replace the L-type mechanical peeling test, so as to solve the problems of difficult preparation, long cycle and high processing cost of aluminum profile and die-cast aluminum bending parts. First of all, a mechanical peeling strength test sample with good generality, easy to prepare and symmetry characteristics needs to be designed and developed, and the aluminum profile and die-cast aluminum material does not need to be bent before connection, only the steel plate needs to be bent into a corresponding U shape. The purpose of this is to effectively eliminate the eccentricity problem caused by the deformation of the test sample and the inconsistency of the thickness of the double-sided connecting plate during tensile clamping in the traditional L-type mechanical peeling test. Secondly, a test device matched with it needs to be developed, which can meet the test requirements of the connection joint between aluminum profile and steel plate, die-cast aluminum and steel plate, and is compatible with the existing mechanical property testing machine. Finally, the test process is specified to complete the test and obtain the riveted joint peeling connection strength. In addition, considering that the riveted peeling strength is affected by various factors such as the type, specification, production manufacturer, heat treatment state, sample size, structural adhesive type and riveting quality of the connected materials, it is difficult to develop a general reference riveted peeling strength as a reference value for judging the qualification of riveted joint peeling strength. SUMMARY

[0003] Another technical problem to be solved by the present application is to overcome the defects of difficult preparation, long cycle and high processing cost of the L-shaped mechanical peeling test of the pressure cast aluminum bending piece in the prior art, so as to provide a riveting peeling performance test method for a low-elongation aluminum alloy and a steel plate.

[0004] A riveting peeling performance test method for a low-elongation aluminum alloy and a steel plate, comprising the following steps:

[0005] S1: manufacturing a riveting joint mechanical peeling test sample and a riveting joint mechanical peeling test device, assembling the riveting joint mechanical peeling test sample and the riveting joint mechanical peeling test device to form a test assembly;

[0006] S2: installing the upper clamping end of the test assembly on the upper part of the tensile testing machine and clamping, installing the lower clamping end on the lower part of the tensile testing machine and clamping, and setting the test program parameters;

[0007] S3: starting the test program until the riveting point is peeled off and damaged, and recording the maximum peeling force F of a single riveting joint;

[0008] S4: calculating the riveting joint peeling strength Fs according to the formula, Fs=Fp-2S, wherein Fp is the average value of the maximum peeling force F of n riveting joint samples, wherein 5≤n≤10, and S is the standard deviation of the sample;

[0009] S5: judging the qualification of the peeling strength test result, randomly evaluating the maximum peeling force of a plurality of riveting joint mechanical peeling test samples under the process, if the test result is greater than Fs, it is determined to be qualified, otherwise it is determined to be unqualified.

[0010] Further, the riveting joint mechanical peeling test sample comprises a U-shaped plate, a bottom plate and a riveting connecting element, the U-shaped plate is fixedly connected to the middle region position of the length direction of the bottom plate through the riveting connecting element, the riveting point to be tested is located at the center of the bottom plate, two first through holes are further provided on the bottom plate, the two first through holes are symmetrically distributed on the two sides of the length direction bisector of the upper surface of the bottom plate, and two second through holes are provided on the two vertical surfaces of the U-shaped plate.

[0011] Further, the riveting joint mechanical peeling test device comprises a lower clamping unit and an upper clamping unit, the lower clamping unit clamps the bottom plate, and the upper clamping unit clamps the U-shaped plate;

[0012] The lower clamping unit comprises two fastening plates and a T-shaped loading block, two fourth through holes are symmetrically arranged on the T-shaped loading block, a third through hole is arranged on each of the two fastening plates, the diameters of the fourth through holes are the same as those of the third through holes, a blind hole is arranged at the center of the upper surface of the T-shaped loading block, the bottom plate is fixed between the T-shaped loading block and the two fastening plates through two first fastening bolts and two first fastening nuts, the third through holes are in clearance fit with the first fastening bolts, the lower surface of the bottom plate is attached to the upper surface of the T-shaped loading block, and the upper surface of the bottom plate is attached to the fastening plate; and the protrusion at the back of the rivet joint to be tested is connected with the blind hole in a matched mode.

[0013] The upper clamping unit comprises an upper bearing block, two fourth through holes are arranged in the lower U-shaped area of the upper bearing block, the U-shaped plate is fixed with the upper bearing block through two second fastening nuts and two second fastening bolts, the fourth through holes are in clearance fit with the second fastening bolts, and the lower U-shaped area of the upper bearing block is not in contact with the inner surface of the U-shaped plate.

[0014] Further, the width of the U-shaped plate is denoted as W1, the width of the bottom plate is denoted as W2, the width W1 of the U-shaped plate satisfies 30mm≤W1≤45mm, and the width W2 of the bottom plate satisfies W2=W1.

[0015] Further, the width of the fastening plate is denoted as W3, the width of the T-shaped loading block is denoted as W4, the width W3 of the fastening plate satisfies W3=W2, and the width W4 of the T-shaped loading block satisfies W3≤W4≤W3+15mm.

[0016] Further, the width of the lower U-shaped area of the upper bearing block is denoted as L2, and the gap between the two side vertical surfaces of the U-shaped plate is denoted as L1, the width L2 of the lower U-shaped area of the upper bearing block satisfies L2=W1, and the distance L1 between the two side vertical surfaces of the U-shaped plate satisfies L2+0.1mm≤L1≤L2+0.5mm.

[0017] Further, the diameter of the blind hole is greater than the diameter of the protrusion at the back of the rivet joint to be tested, and the depth of the diameter of the blind hole is greater than the depth of the protrusion at the back of the rivet joint to be tested.

[0018] Further, structural glue is coated between the U-shaped plate and the bottom plate.

[0019] Further, the test program parameters set in the step S2 are specifically that the displacement loading speed is set to 0.1mm / min-10.0mm / min.

[0020] Further, the rivet connecting element is an SPR self-punching rivet, a hot-melt self-tapping rivet or a core-pulling rivet.

[0021] The technical scheme of the present application solves the problem that aluminum profiles and die-cast aluminum cannot be bent to prepare L-shaped mechanical peeling samples, avoids the problems of great difficulty, high cost, long cycle and the like caused by preparing aluminum profile and die-cast aluminum mechanical peeling samples with special molds; the technical scheme of the present application eliminates the problem of tensile clamping eccentricity caused by sample deformation and inconsistent thickness of double-sided plates during the test of traditional L-shaped mechanical peeling samples, improves the consistency and accuracy of test results; the sample and device used by the present application are simple and easy to use; the present application provides a riveted joint peeling strength acquisition method and qualification criterion for aluminum profiles, die-cast aluminum and steel plates, which has high accuracy, is simple to use and has good popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical scheme in the specific embodiments of the present application or the prior art, the drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0023] Fig. 1 Schematic diagram of a riveted joint mechanical peeling test sample;

[0024] Fig. 2 Schematic diagram of a lower clamping unit;

[0025] Fig. 3 Schematic diagram of an upper clamping unit;

[0026] Fig. 4 Schematic diagram of a riveted joint mechanical peeling test assembly;

[0027] Explanation of reference signs:

[0028] 1 - riveted joint mechanical peeling test sample; 11 - U-shaped plate;

[0029] 12 - bottom plate; 13 - structural adhesive; 14 - riveted connecting element;

[0030] 15 - first through hole; 16 - second through hole;

[0031] 2 - lower clamping unit; 21 - first fastening bolt; 22 - fastening pressure plate;

[0032] 23 - T-shaped loading block; 24 - first fastening nut; 25 - third through hole;

[0033] 26 - fourth through hole; 27 - blind hole; 28 - first friction surface;

[0034] 3 - upper clamping unit; 31 - second fastening nut; 32 - upper bearing block;

[0035] 33 - second fastening bolt; 34 - fourth through hole; 35 - second friction surface; DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0037] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] Example 1:

[0041] The peel strength of the hot melt self-tapping riveting (FDS) joint formed by the 1.0mm thick St280 steel plate and the 2.5mm thick 6082-T6 aluminum profile was tested, and the peel strength of the hot melt self-tapping riveting (FDS) joint formed under the process was judged for its eligibility, which was achieved by the following steps:

[0042] S1: make riveting joint mechanical peel test sample 1 and riveting joint mechanical peel test device, assemble the riveting joint mechanical peel test sample and the riveting joint mechanical peel test device to form a test assembly;

[0043] Please refer to Figs. 1 to 4 , the FDS rivet joint mechanical peeling test sample 1 is composed of a U-shaped plate 11, a bottom plate 12, a structural adhesive 13 and a rivet connecting element 14. The manufacturing material of the U-shaped plate 11 is a St280 steel plate with a thickness of 1.0 mm, the manufacturing material of the bottom plate 12 is an 6082-T6 aluminum profile with a thickness of 2.5 mm, the structural adhesive 13 selected is a 1840C structural adhesive used in the current production, and the rivet connecting element 14 selected is an M5X22 type FDS rivet used in the current production. Among them, the U-shaped plate 11 and the bottom plate 12 are connected in the form of a glue-rivet composite joint through the structural adhesive 13 and the rivet connecting element 14, and before connection, a proper amount of structural adhesive 13 is required to be applied on the bonding surface of the U-shaped plate 11 according to the requirements, and after the connection is completed, the joint is baked at 180℃ for half an hour according to the baking requirements to ensure that the structural adhesive 13 is cured. The bottom surface of the U-shaped plate 11 is connected to the upper surface of the bottom plate 12 in the length direction and is located at the middle region position of the bottom plate 12 in the length direction, the rivet joint to be tested is located at the center of the bottom plate 12, and two first through holes 15 for fixing are provided on the bottom plate 12. Among them, the width of the U-shaped plate 11 is denoted as W1, the width of the bottom plate 12 is denoted as W2, the width W1 of the U-shaped plate 11 satisfies: 30mm≤W1≤45mm, the width W2 of the bottom plate 12 satisfies: W2=W1, and in this embodiment, the width W1 of the U-shaped plate 11 is selected as 40mm, and the width W2 of the bottom plate 12 is selected as 40mm. The two first through holes 15 are symmetrically distributed on both sides of the length direction bisector of the upper surface of the bottom plate 12, and the distance between the first through hole 15 and the vertical surface of the U-shaped plate 11 is as small as possible under the condition that the assembly can be interference-free. The second through holes 16 on the two vertical surfaces of the U-shaped plate 11 are symmetrically distributed on both sides of the central vertical surface of the upper surface of the bottom plate 12 in the length direction. The manufacturing material of the U-shaped plate 11 is a vehicle body steel plate material, the manufacturing material of the bottom plate 12 is an aluminum profile or a die-cast aluminum, and the material type, size specification and heat treatment state of the bottom plate 12 are consistent with the actual vehicle body product. The structural adhesive 13 and the rivet connecting element 14 adopt the structural adhesive type and the rivet connecting element type used in the actual vehicle body product structure.

[0044] The FDS rivet joint is prepared by using the actual connection process and the corresponding parameters for forming the rivet joint in the actual component, and the rivet quality requirement is consistent with the rivet quality requirement in the actual vehicle body product.

[0045] The rivet joint mechanical peeling test device comprises a lower clamping unit 2 and an upper clamping unit 3; the lower clamping unit 2 clamps the bottom plate 12, and the upper clamping unit 3 clamps the U-shaped plate 11;

[0046] The lower clamping unit 2 comprises two fastening plates 22 and a T-shaped loading block 23, two fourth through holes 26 are symmetrically arranged on the T-shaped loading block 23, two third through holes 25 are arranged on the two fastening plates 22, the fourth through holes 26 have the same diameter as the third through holes 25, a blind hole 27 is arranged at the center of the upper surface of the T-shaped loading block 23, the bottom plate 12 is fixed between the T-shaped loading block 23 and the two fastening plates 22 through two first fastening bolts 21 and two first fastening nuts 24, the third through holes 25 are in clearance fit with the first fastening bolts 21, the clearance is generally selected to be 0.1-0.5mm, and in the embodiment, the clearance is selected to be 0.25mm, the lower surface of the bottom plate 12 is attached to the upper surface of the T-shaped loading block 23, the upper surface of the bottom plate 12 is attached to the fastening plate 22, and the protrusion at the back of the riveting point to be measured is connected with the blind hole 27 in fit; the width of the fastening plate 22 is denoted as W3, the width of the T-shaped loading block 23 is denoted as W4, the width W3 of the fastening plate 22 satisfies W3=W2, the width W4 of the T-shaped loading block 23 satisfies W3≤W4≤W3+15mm, in the embodiment, W3=40mm and W4=45mm. The T-shaped loading block 23 is made of 40Cr medium carbon quenched and tempered steel and is manufactured by a numerical control machining center, and a first friction surface 28 for anti-skid is processed on the bilateral surface of the clamping end of the T-shaped loading block 23.

[0047] The upper clamping unit 3 comprises an upper bearing block 32, two fourth through holes 34 are processed in the lower U-shaped area of the upper bearing block 32, the U-shaped plate 11 is fixed with the upper bearing block 32 through two second fastening nuts 31 and two second fastening bolts 33, the bilateral surface of the clamping end of the upper bearing block 32 is processed with a second friction surface 35 for anti-skid, the fourth through holes 34 are in clearance fit with the second fastening bolts 33, and the general clearance is 0.1-0.5mm, and in the embodiment, the clearance is selected to be 0.25mm, the lower U-shaped area of the upper bearing block 32 is not in contact with the inner surface of the U-shaped plate 11, the width of the lower U-shaped area of the upper bearing block 32 is denoted as L2, the gap between the bilateral vertical surfaces of the U-shaped plate 11 is denoted as L1, the width L2 of the lower U-shaped area of the upper bearing block 32 satisfies L2=W1, and the distance L1 between the bilateral vertical surfaces of the U-shaped plate 11 satisfies L2+0.1mm≤L1≤L2+0.5mm, in the embodiment, L2=40mm and L1=40.5mm, and the manufacturing material of the upper bearing block 32 is 40Cr medium carbon quenched and tempered steel.

[0048] When the riveted joint mechanical peeling test sample 1 is assembled with the riveted joint mechanical peeling test device, first, the riveted joint mechanical peeling test sample 1 is fixed on the T-shaped loading block 23, the first fastening bolt 21 is sequentially threaded through the third through hole 25 of the fastening pressure plate 22, the first through hole 15 of the riveted joint mechanical peeling test sample 1 and the fourth through hole 26 of the T-shaped loading block 23, and is fastened on the upper surface of the T-shaped loading block 23 by means of the fastening nut 24, and then the lower U-shaped area of the upper bearing block 32 is placed into the U-shaped plate 11, the fastening bolt 33 is sequentially threaded through the second through hole 16 and the fourth through hole 34, and is fastened on both sides of the U-shaped area of the upper bearing block 32 by means of the second fastening nut 31, forming a test assembly, and ensuring that the neutral planes of the upper clamping end and the lower clamping end are in the same plane, ensuring the accuracy of the test results.

[0049] S2: The upper clamping end of the test assembly is installed on the upper part of the tensile testing machine and clamped, the lower clamping end is installed on the lower part of the tensile testing machine and clamped, and the test program parameters are set; the displacement loading speed is set to 0.1 mm / min-10.0 mm / min, and in this embodiment, the displacement loading speed is set to 5.0 mm / min.

[0050] S3: Start the test program until the riveted joint to be tested is peeled off, record the maximum peeling force F of a single riveted joint; complete the test according to the set program, and read the maximum peeling force F of a single riveted joint from the computer, and the maximum peeling forces of the 5 groups of riveted joints after the test are 5673 N, 5869 N, 6053 N, 5829 N and 6102 N respectively.

[0051] S4: Considering the fluctuation of the measurement results, the riveted joint peeling strength Fs is calculated according to the formula Fs=Fp-2S, where Fp is the average value of the maximum peeling force F of n riveted joint samples, 5≤n≤10, and obvious abnormal points should be timely eliminated during data processing, and S is the standard deviation of the sample; in this embodiment, Fs=Fp-2S=5556.48, n=5, the average value Fp of the maximum peeling force F of the 5 riveted joint samples is 5905.2, and the standard deviation S of the sample is 174.36.

[0052] S5: Determine the qualification of the peeling strength test results, randomly evaluate the maximum peeling force of 3 riveted joint mechanical peeling test samples under the process, if the test results are all greater than Fs, it is determined to be qualified; otherwise, it is determined to be unqualified, in this embodiment, the maximum peeling forces of 3 riveted joint mechanical peeling test samples randomly evaluated are 5555 N, 5548 N and 5530 N, and the test results are all less than Fs, so it can be determined that the riveted joint peeling connection strength under the process condition is unqualified.

[0053] Example 2:

[0054] In this embodiment, the peel strength of self-piercing rivet joint (SPR) formed by 0.7mm thick St12 steel plate and 2.5mm thick AlSi10MnMg-T7 die-cast aluminum plate is tested, and the peel strength of the self-piercing rivet joint (SPR) formed under this process is judged. The method steps of this embodiment are the same as those of Embodiment 1. The rivet joint mechanical peel test sample and the rivet joint mechanical peel test device in this embodiment are the same as those in Embodiment 1 and the installation process is the same. In this embodiment, the width W1 of the U-shaped plate 11 is 35mm, the width W2 of the base plate 12 is 35mm, the width W3 of the clamping plate 22 is 35mm, the width W4 of the T-shaped loading block 23 is 35mm, the material of the T-shaped loading block 23 is 42CrMo medium carbon quenched and tempered steel, the gap between the third through hole 25 and the first fastening bolt 21 is 0.25mm, the gap between the fourth through hole 34 and the second fastening bolt 33 is 0.25mm, the width L2 of the lower U-shaped area of the upper bearing block 32 is 35mm, the distance L1 between the two sides of the U-shaped plate 11 is 35.2mm, and the displacement loading speed in this embodiment is set to 2.5mm / min. The test is completed according to the set program. The maximum peel forces of the 8 rivet joints after the test are 6926N, 7269N, 7553N, 7438N, 7502N, 4121N, 7329N and 7626N respectively. The abnormal test point 4121N is rejected. Considering the fluctuation of the measurement results, the peel strength of the rivet joint is characterized by the formula: Fs=Fp-2S=6908.75. The average value Fp of the maximum peel force F of the 7 rivet joint samples is 7377.57, and the standard deviation S is 234.41. The maximum peel forces of 3 rivet joint mechanical peel test samples randomly evaluated under this process are 7425N, 7123N and 7732N respectively. The test results are all greater than Fs, so it can be determined that the peel joint strength of the SPR joint under this process is qualified.

[0055] Obviously, the above embodiments are only examples for clarity and do not limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all embodiments cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method of testing the rivet peel performance of a low elongation aluminum alloy to a steel panel, characterized by, The method comprises the following steps: S1: a riveted joint mechanical peeling test sample and a riveted joint mechanical peeling test device are prepared, the riveted joint mechanical peeling test sample is assembled with the riveted joint mechanical peeling test device to form a test assembly; S2: the upper clamping end of the test assembly is installed on the upper part of a tensile testing machine and clamped, the lower clamping end is installed on the lower part of the tensile testing machine and clamped, and test program parameters are set; S3: the test program is started until the riveted joint to be tested is peeled off, and the maximum peeling force F of a single riveted joint is recorded; S4: the peeling strength Fs of the riveted joint is calculated according to the formula Fs=Fp-2S, wherein Fp is the average value of the maximum peeling force F of n riveted joint samples, 5≤n≤10, and S is the standard deviation of the samples; S5: the qualification of the peeling strength test result is judged, the maximum peeling force of a plurality of riveted joint mechanical peeling test samples is randomly evaluated under the process, and if the test result is greater than Fs, it is determined to be qualified; otherwise, it is determined to be unqualified; The riveted joint mechanical peeling test sample comprises a U-shaped plate (11), a bottom plate (12) and a riveted connecting element (14), the U-shaped plate (11) is fixedly connected to the middle region of the length direction of the bottom plate (12) through the riveted connecting element (14), the riveted joint to be tested is located at the center of the bottom plate (12), two first through holes (15) are further arranged on the bottom plate (12), the two first through holes (15) are symmetrically arranged on the two sides of the length direction bisector of the upper surface of the bottom plate (12), and two second through holes (16) are arranged on the two vertical surfaces of the U-shaped plate (11); The riveted joint mechanical peeling test device comprises a lower clamping unit (2) and an upper clamping unit (3), the lower clamping unit (2) clamps the bottom plate (12), and the upper clamping unit (3) clamps the U-shaped plate (11); The lower clamping unit (2) comprises two fastening pressure plates (22) and a T-shaped loading block (23), two fourth through holes (26) are symmetrically arranged on the T-shaped loading block (23), a third through hole (25) is arranged on each of the two fastening pressure plates (22), the diameters of the fourth through holes (26) and the third through holes (25) are the same, a blind hole (27) is arranged at the center of the upper surface of the T-shaped loading block (23), the bottom plate (12) is fixedly connected between the T-shaped loading block (23) and the two fastening pressure plates (22) through two first fastening bolts (21) and two first fastening nuts (24), the third through holes (25) are in clearance fit with the first fastening bolts (21), the lower surface of the bottom plate (12) is attached to the upper surface of the T-shaped loading block (23), the upper surface of the bottom plate (12) is attached to the fastening pressure plates (22), and the protrusion at the back of the riveted joint to be tested is connected to the blind hole (27). The upper clamping unit (3) comprises an upper bearing block (32), two fourth through holes (34) are processed in the lower U-shaped area of the upper bearing block (32), the U-shaped plate (11) is fixedly connected with the upper bearing block (32) through two second fastening nuts (31) and two second fastening bolts (33), the fourth through holes (34) are in clearance fit with the second fastening bolts (33), and the lower U-shaped area of the upper bearing block (32) is not in contact with the inner surface of the U-shaped plate (11).

2. The method of claim 1, wherein, The width of the U-shaped plate (11) is denoted as W1, the width of the bottom plate (12) is denoted as W2, the width W1 of the U-shaped plate (11) satisfies 30mm≤W1≤45mm, and the width W2 of the bottom plate (12) satisfies W2=W1.

3. The method of claim 2, wherein, The width of the fastening pressing plate (22) is denoted as W3, the width of the T-shaped loading block (23) is denoted as W4, the width W3 of the fastening pressing plate (22) satisfies W3=W2, and the width W4 of the T-shaped loading block (23) satisfies W3≤W4≤W3+15mm.

4. The method of claim 2, wherein, The width of the lower U-shaped area of the upper bearing block (32) is denoted as L2, the gap between the two side vertical surfaces of the U-shaped plate (11) is denoted as L1, the width L2 of the lower U-shaped area of the upper bearing block (32) satisfies L2=W1, and the distance L1 between the two side vertical surfaces of the U-shaped plate (11) satisfies L2+0.1mm≤L1≤L2+0.5mm.

5. The method of claim 1, wherein, The diameter of the blind hole (27) is greater than the diameter of the back protrusion of the riveting point to be tested, and the depth of the diameter of the blind hole (27) is greater than the depth of the back protrusion of the riveting point to be tested.

6. The method of claim 1, wherein, The U-shaped plate (11) and the bottom plate (12) are coated with structural glue (13).

7. The method of claim 1, wherein, The test program parameters set in the step S2 are specifically that the displacement loading speed is set to 0.1mm / min-10.0mm / min.

8. The method of claim 1, wherein, The riveting connecting element (14) is an SPR self-punching rivet, a hot-melt self-tapping rivet or a core-pulling rivet.

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