A core-pulling rivet fatigue test tool

Abstract

The utility model relates to mechanical part detection technical field, concretely is a kind of core pull rivet fatigue test tool, including the connecting structure for being connected with fatigue testing machine, paddle and interlayer distribution block, connecting structure includes head connecting cylinder and tail connecting cylinder;Interlayer distribution block is set between head connecting cylinder and tail connecting cylinder, and is equipped with central through-hole;Paddle is fixedly arranged in one side of interlayer distribution block, head connecting cylinder includes fixed part and multiple replaceable rivet adaptation part, fixed part is fixedly connected with fatigue testing machine by threaded connecting rod, and the side of rivet adaptation part towards fixed part is equipped with external thread, the side of fixed part towards tail connecting cylinder is equipped with internal thread adapted with external thread, rivet adaptation part is detachably assembled in fixed part by thread cooperation, rivet adaptation detection hole, central through-hole and tail detection hole are sequentially communicated. The present application can adapt to different models of core pull rivet, satisfy the fatigue test demand of multiple core pull rivet.

Description

Technical Field

[0001] This utility model relates to the field of mechanical parts testing technology, specifically a fatigue testing fixture for a core-pulling rivet. Background Technology

[0002] As a critical fastener in aerospace, automotive, and rail transportation industries, the fatigue performance of blind rivets directly determines the safety and reliability of the connection structure. Under complex operating conditions, blind rivets must withstand long-term alternating loads; insufficient fatigue strength can lead to connection failure and serious safety accidents. Currently, the industry mainly relies on tensile fatigue testing fixtures to test the fatigue performance of blind rivets, in order to evaluate their fatigue resistance under cyclic tensile stress. However, traditional tensile fatigue testing fixtures cannot be adapted to blind rivets of different specifications. When dealing with blind rivet products with different head shapes, it is necessary to frequently disassemble and replace the core components of the fixture, which not only increases the complexity of the operation process, but also affects the accuracy of the test data due to assembly errors after component replacement.

[0003] Chinese Patent Publication No. CN221224182U discloses a tooling for fatigue testing of threaded blind rivets, including a connecting rod, which is divided into an upper connecting rod and a lower connecting rod. The upper and lower connecting rods have the same structure. The top surface of the upper connecting rod has a cylindrical inner cavity that does not penetrate the connecting rod. The inner circumference of the inner cavity is provided with a connecting internal thread that can connect to the threaded rod of a fatigue testing machine. The bottom of the inner cavity has a detection hole with the same diameter as the pre-installed hole of the threaded blind rivet. A paddle is provided between the upper and lower connecting rods to simulate the application environment of the threaded blind rivet. This solution only adapts to a single specification of threaded blind rivet by using upper and lower connecting rods with the same structure and a fixed detection hole. Moreover, the distance between the upper and lower connecting rods is fixed, which cannot adapt to different models of blind rivets and cannot meet the fatigue testing requirements of various blind rivets. Utility Model Content

[0004] The present invention aims to provide a fatigue testing fixture for blind rivets, which effectively solves the problem that the existing technology cannot adapt to different models of blind rivets and cannot meet the fatigue testing needs of various blind rivets.

[0005] This application provides the following technical solution: A fatigue testing fixture for blind rivets includes a connecting structure for connection to a fatigue testing machine, a paddle, and a sandwich feeding block. The connecting structure includes a head connecting cylinder and a tail connecting cylinder, which are respectively fixedly connected to corresponding positions on the fatigue testing machine via threaded connecting rods. The sandwich feeding block is a replaceable annular block structure with a central through hole, and is positioned between the head and tail connecting cylinders. The paddle is fixedly disposed on one side of the sandwich feeding block. The head connecting cylinder includes a fixing part and multiple replaceable rivets. The rivet adapter is fixedly connected to the fatigue testing machine via the threaded connecting rod. The rivet adapter has an external thread on the side facing the fixed part, and an internal thread that matches the external thread on the side facing the tail connecting cylinder. The rivet adapter is detachably assembled to the fixed part via threaded engagement. The rivet adapter has a rivet adapter detection hole corresponding to the pull rivet. The tail connecting cylinder has a tail detection hole corresponding to the rivet adapter detection hole on the side facing the head connecting cylinder. The rivet adapter detection hole, the central through hole, and the tail detection hole are connected in sequence.

[0006] The technical principle of this solution is as follows: The fatigue testing fixture for blind rivets includes a head connecting cylinder, a tail connecting cylinder, a sandwich feeding block, and a paddle. The head and tail connecting cylinders are fixed to the upper and lower loading ends of the fatigue testing machine via threaded connecting rods, forming a stable loading frame. The sandwich feeding block is a replaceable annular block structure. The central through hole of the sandwich feeding block is coaxially aligned with the rivet adapter detection hole of the head connecting cylinder and the tail detection hole of the tail connecting cylinder, forming a through rivet installation channel to ensure that the tested blind rivet can pass through and be fixed in a straight line. The head connecting cylinder adopts a split design, including a fixing part and multiple replaceable rivet adapter parts. The fixing part is fixed to the testing machine via the threaded connecting rod of the fatigue testing machine. The rivet adapter parts are screwed into the internal thread of the fixing part via external threads, enabling quick assembly and disassembly to adapt to blind rivets of different specifications. The rivet adapter detection holes in the rivet adapter parts correspond to the tail detection holes to ensure that the force axes at both ends of the blind rivet are consistent after installation. The blades are fixed to one side of the interlayer feeding block and reciprocate under the drive of the fatigue testing machine, transferring the cyclic load to the rivet through the interlayer feeding block. During the test, the rivet passes through each through hole, and the fatigue testing machine applies alternating loads to simulate fatigue conditions under actual working conditions. By recording the number of cycles when the rivet breaks, its fatigue life can be quantitatively evaluated, realizing the fatigue performance test of the blind rivet.

[0007] Compared with the prior art, the beneficial effects of this utility model are as follows: The head connecting cylinder is equipped with a fixing part and multiple replaceable rivet adapter parts. The rivet adapter parts have external threads on the side facing the fixing part, and the fixing part has matching internal threads on the side facing the tail connecting cylinder. The rivet adapter parts are detachably assembled to the fixing part through threaded engagement, and each rivet adapter part has a rivet adapter detection hole corresponding to a specific type of blind rivet. In the prior art, the detection hole of the connecting rod has the same diameter as the pre-installed hole of the specific threaded blind rivet, and the structure is fixed. Changing to a different type of rivet requires replacing the entire connecting rod. However, this application only requires disassembling the rivet adapter part and replacing it with a new adapter part with the corresponding rivet adapter detection hole, which allows the rivet adapter detection hole to match the blind rivet to be tested. It eliminates the need to replace the entire head connecting cylinder, effectively overcoming the problem of the prior art's inability to adapt to different types of blind rivets, significantly improving the tooling versatility, meeting the fatigue testing needs of various blind rivets, achieving rapid adaptation of rivet specifications, precise control of the loading path, and effective transfer of fatigue load, ensuring the accuracy and reliability of the test results.

[0008] Furthermore, the blade is provided with a U-shaped notch corresponding to the rivet fitting part. The opening width of the U-shaped notch is adapted to the diameter of the shank of the pull rivet, and the bottom surface of the U-shaped notch is flush with the end face of the central through hole. The diameter of the central through hole is matched with the diameter of the shank of the pull rivet, and the axis of the central through hole coincides with the axis of the U-shaped notch.

[0009] By providing a U-shaped notch on the paddle corresponding to the rivet fitting part, the opening width of the U-shaped notch is adapted to the diameter of the blind rivet shank, the bottom surface of the U-shaped notch is flush with the end face of the central through hole, and the diameter of the central through hole matches that of the blind rivet shank, and the axis coincides with the axis of the U-shaped notch, the blind rivet can be accurately positioned during installation, ensuring stable force direction and avoiding deviations in test data due to positional offset. At the same time, the U-shaped notch can assist in the rapid assembly of the blind rivet, improving the efficiency of test operation and ensuring the consistency and stability of structural fit during the test.

[0010] Furthermore, the blind rivet includes a first blind rivet and a second blind rivet. The rivet adapter includes a first rivet adapter that adapts to the first blind rivet and a second rivet adapter that adapts to the second blind rivet. The first rivet adapter has a first external thread on the side facing the fixing part and a first rivet adapter detection hole corresponding to the first blind rivet on the side facing the tail connecting cylinder. The second rivet adapter has a second external thread on the side facing the fixing part and a second rivet adapter detection hole corresponding to the second blind rivet on the side facing the tail connecting cylinder. The first rivet adapter detection hole and the second rivet adapter detection hole are sequentially connected to the central through hole and the tail detection hole, respectively.

[0011] By setting a first rivet adapter part for adapting to a first blind rivet and a second rivet adapter part for adapting to a second blind rivet, with the first rivet adapter part having a first external thread and a first rivet adapter detection hole, and the second rivet adapter part having a second external thread and a second rivet adapter detection hole, and by sequentially connecting the first rivet adapter detection hole and the second rivet adapter detection hole to the center through hole and the tail detection hole respectively, accurate adaptation and detection of different types of blind rivets can be achieved, improving the compatibility of various blind rivets, facilitating rapid detection of different blind rivets, ensuring the accuracy and comprehensiveness of detection, and improving the overall convenience and reliability of use.

[0012] Furthermore, the first blind rivet is a round-head blind rivet or a blunt-head blind rivet, and the second blind rivet is a countersunk blind rivet.

[0013] By classifying blind rivets, it is possible to achieve compatibility of different types of blind rivets with fatigue testing fixtures.

[0014] Furthermore, the end face of the first rivet adapter is a planar structure with an annular anti-slip texture on its surface, and the end face of the second rivet adapter is a conical structure that matches the head taper of the countersunk blind rivet, with the conical angle of the conical structure being consistent with the head taper of the countersunk blind rivet.

[0015] By setting the end face of the first rivet adapter to a planar structure with annular anti-slip texture, the friction during operation can be increased, making it easier to grip or position. Setting the end face of the second rivet adapter to a conical structure that matches the taper of the countersunk blind rivet head can ensure a precise fit with the countersunk blind rivet, improving adaptability.

[0016] Furthermore, one end of the head connecting cylinder is provided with a first internal threaded hole, and one end of the threaded connecting rod is provided with a third external thread adapted to the first internal threaded hole. The threaded connecting rod is threadedly connected to the first internal threaded hole of the head connecting cylinder through the third external thread, and the end of the threaded connecting rod is flush with the end face of the head connecting cylinder.

[0017] The head connecting cylinder and the threaded connecting rod are connected by the first internal thread hole and the third external thread, respectively, to achieve a stable assembly between the head connecting cylinder and the threaded connecting rod, avoiding loose connections that could affect test accuracy. Furthermore, the end of the threaded connecting rod is flush with the end face of the head connecting cylinder, which reduces the interference of structural protrusions on the test operation after assembly and ensures more stable force transmission during fatigue testing.

[0018] Furthermore, one end of the tail connecting cylinder is provided with a second internal threaded hole, and the other end of the threaded connecting rod is provided with a fourth external thread adapted to the second internal threaded hole. The threaded connecting rod is threadedly connected to the second internal threaded hole of the tail connecting cylinder through the fourth external thread, and the end of the threaded connecting rod is flush with the end face of the tail connecting cylinder.

[0019] By providing a second internal threaded hole at one end of the tail connecting cylinder and a matching fourth external thread at the other end of the threaded connecting rod, the tail connecting cylinder and the threaded connecting rod are threadedly connected and their ends are flush. This achieves a stable and precise connection between the threaded connecting rod and the tail connecting cylinder, ensuring the coaxiality and stability of the connection and effectively preventing loosening of the connection. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of a fatigue testing fixture for a pull-out rivet according to the present invention. Figure 2 This is a cross-sectional view of the first rivet adapter in a fatigue testing fixture for a blind rivet according to this utility model. Figure 3 This is a cross-sectional view of the second rivet adapter in a fatigue testing fixture for a blind rivet according to this utility model. Figure 4 This is a schematic diagram of the paddle structure in a fatigue testing fixture for a core-pulling rivet according to this utility model; Figure 5 This is a schematic diagram of the interlayer feeding block in a fatigue testing fixture for a blind rivet according to this utility model; Figure 6 This is a schematic diagram of the tail connecting cylinder in a fatigue testing fixture for a pull-out rivet according to this utility model. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: head connecting cylinder 1, fixing part 11, first rivet adapter part 12, second rivet adapter part 13, paddle 2, tail connecting cylinder 3, core-pulling rivet 4, interlayer feeding block 5, U-shaped notch 6, central through hole 7, and tail inspection hole 8.

[0022] like Figures 1 to 6As shown, a fatigue testing fixture for a blind rivet includes a connecting structure for connection to a fatigue testing machine, a paddle 2, and a sandwich feeding block 5. The connecting structure includes a head connecting cylinder 1 and a tail connecting cylinder 3, which are respectively fixedly connected to corresponding positions of the fatigue testing machine via threaded connecting rods. The sandwich feeding block 5 is a replaceable annular block structure with a central through hole 7, and is disposed between the head connecting cylinder 1 and the tail connecting cylinder 3. The paddle 2 is fixedly disposed on one side of the sandwich feeding block 5. The head connecting cylinder 1 includes a fixing part 11 and multiple replaceable... The rivet adapter is provided with a fixed part 11, which is fixedly connected to the fatigue testing machine through the threaded connecting rod. The rivet adapter is provided with an external thread on the side facing the fixed part 11, and the fixed part 11 is provided with an internal thread that matches the external thread on the side facing the tail connecting cylinder 3. The rivet adapter is detachably assembled to the fixed part 11 through threaded engagement. The rivet adapter is provided with a rivet adapter detection hole corresponding to the pull rivet 4. The tail connecting cylinder 3 is provided with a tail detection hole 8 corresponding to the rivet adapter detection hole on the side facing the head connecting cylinder 1. The rivet adapter detection hole, the central through hole 7 and the tail detection hole 8 are connected in sequence.

[0023] Specifically, the paddle 2 is provided with a U-shaped notch 6 corresponding to the rivet adapter. The opening width of the U-shaped notch 6 is adapted to the diameter of the rod of the pull rivet 4, and the bottom surface of the U-shaped notch 6 is flush with the end face of the central through hole 7. The diameter of the central through hole 7 is matched with the diameter of the rod of the pull rivet 4, and the axis of the central through hole 7 coincides with the axis of the U-shaped notch 6.

[0024] In this embodiment, after selecting a suitable blind rivet 4, the opening width of the U-shaped notch on the paddle 2 is designed based on its shank diameter to ensure that the shank diameter of the blind rivet 4 and the opening width of the U-shaped notch are compatible, allowing the shank of the blind rivet 4 to be smoothly inserted. Simultaneously, the bottom surface of the U-shaped notch is machined flush with the end face of the central through hole 7, and this precision requirement is ensured through a precision measurement and positioning device. The diameter of the central through hole 7 must strictly match the shank diameter of the blind rivet 4. Finally, through precise assembly positioning, the axis of the central through hole 7 is ensured to coincide with the axis of the U-shaped notch. The specific model needs to be determined based on the actual application specifications of the blind rivet 4. For example, if a blind rivet 4 with a diameter of 4mm is selected, the opening width of the U-shaped notch and the diameter of the central through hole 7 are both designed and machined around the parameter of 4mm.

[0025] Specifically, the blind rivet 4 includes a first blind rivet and a second blind rivet. The rivet adapter includes a first rivet adapter 12 that adapts to the first blind rivet and a second rivet adapter 13 that adapts to the second blind rivet. The first rivet adapter 12 has a first external thread on the side facing the fixing part 11. The first rivet adapter 12 has a first rivet adapter detection hole corresponding to the first blind rivet on the side facing the tail connecting cylinder 3. The second rivet adapter 13 has a second external thread on the side facing the fixing part 11. The second rivet adapter 13 has a second rivet adapter detection hole corresponding to the second blind rivet on the side facing the tail connecting cylinder 3. The first rivet adapter detection hole and the second rivet adapter detection hole are sequentially connected to the central through hole 7 and the tail detection hole 8, respectively.

[0026] In this embodiment, corresponding first rivet adapter 12 and second rivet adapter 13 are provided for the first and second blind rivets, respectively. The first external thread of the first rivet adapter 12 facing the fixing part 11 engages with the internal thread of the fixing part 11 facing the tail connecting cylinder 3, enabling detachable assembly with the fixing part 11. The first rivet adapter detection hole on the side of the first rivet adapter 12 facing the tail connecting cylinder 3 corresponds to the first blind rivet. Similarly, the second external thread of the second rivet adapter 13 facing the fixing part 11 engages with the internal thread of the fixing part 11, enabling detachable assembly. The second rivet adapter detection hole on the side of the second rivet adapter 13 facing the tail connecting cylinder 3 corresponds to the second blind rivet. Meanwhile, the first rivet adapter detection hole and the second rivet adapter detection hole are connected in sequence to the central through hole 7 of the interlayer feeding block 5 and the tail detection hole 8 of the tail connecting cylinder 3, so that by replacing different rivet adapter parts, the first core-pulling rivet and the second core-pulling rivet can be adapted to meet the fatigue test requirements of both.

[0027] Specifically, the first pop rivet is a round-head pop rivet or a blunt-head pop rivet, and the second pop rivet is a countersunk pop rivet.

[0028] Specifically, the end face of the first rivet adapter 12 is a planar structure with an annular anti-slip texture on the surface of the planar structure, and the end face of the second rivet adapter 13 is a conical structure that matches the head taper of the countersunk blind rivet, with the conical angle of the conical structure being consistent with the head taper of the countersunk blind rivet.

[0029] In this embodiment, for the first blind rivet (round head or blunt head), a first rivet adapter 12 is provided. The first rivet adapter 12 has a first rivet adapter detection hole that matches the shape of the round head / blunt head blind rivet. Simultaneously, the end face of the first rivet adapter 12 facing the interlayer feeding block 5 is designed as a planar structure. The annular anti-slip texture on the planar surface enhances the contact friction with the head of the first blind rivet, preventing rivet displacement during testing. For the second blind rivet (countersunk head), a second rivet adapter 13 is provided. The second rivet adapter 13 has a second rivet adapter detection hole corresponding to the shape of the countersunk head blind rivet. The end face of the second rivet adapter 13 is designed as a conical structure, and the angle of the conical surface is completely consistent with the taper of the countersunk head rivet head, ensuring that the countersunk head rivet head can fit tightly against the conical surface to achieve precise positioning. During the test, according to the type of rivet to be tested (round head / bare head or countersunk head), the corresponding first rivet adapter 12 / second rivet adapter 13 is assembled to the fixing part 11 by threaded engagement, so that the rivet adapter detection hole of the first rivet adapter 12 / second rivet adapter 13 is precisely connected to the center through hole 7 of the interlayer feeding block 5 and the tail detection hole 8 of the tail connecting cylinder 3, thus completing the adaptation and installation of different types of rivets on the fatigue test fixture.

[0030] Specifically, one end of the head connecting cylinder 1 is provided with a first internal threaded hole, and one end of the threaded connecting rod is provided with a third external thread that is adapted to the first internal threaded hole. The threaded connecting rod is threadedly connected to the first internal threaded hole of the head connecting cylinder 1 through the third external thread, and the end of the threaded connecting rod is flush with the end face of the head connecting cylinder 1.

[0031] Specifically, one end of the tail connecting cylinder 3 is provided with a second internal threaded hole, and the other end of the threaded connecting rod is provided with a fourth external thread that is adapted to the second internal threaded hole. The threaded connecting rod is threadedly connected to the second internal threaded hole of the tail connecting cylinder 3 through the fourth external thread, and the end of the threaded connecting rod is flush with the end face of the tail connecting cylinder 3.

[0032] In this embodiment, one end of the head connecting cylinder 1 is provided with a first internal threaded hole, and one end of the threaded connecting rod of the fatigue testing machine is provided with a third external thread that matches the first internal threaded hole. During assembly, the end of the threaded connecting rod with the third external thread is screwed into the first internal threaded hole of the head connecting cylinder 1. The head connecting cylinder 1 and the threaded connecting rod are fixedly connected through the threaded engagement, and after connection, the end of the threaded connecting rod is flush with the corresponding end face of the head connecting cylinder 1. One end of the tail connecting cylinder 3 is provided with a second internal threaded hole, and the other end of the threaded connecting rod is provided with a fourth external thread that matches the second internal threaded hole. During assembly, the end of the threaded connecting rod with the fourth external thread is screwed into the second internal threaded hole of the tail connecting cylinder 3. The tail connecting cylinder 3 and the threaded connecting rod are fixedly connected through the threaded engagement, and after connection, the end of the threaded connecting rod is flush with the corresponding end face of the tail connecting cylinder 3. Finally, the head connecting cylinder 1 and the tail connecting cylinder 3 are fixed to their corresponding positions on the fatigue testing machine through the threaded engagement of the two ends of the threaded connecting rod with the head connecting cylinder 1 and the tail connecting cylinder 3, respectively.

[0033] In this embodiment, the connection between the fixing part 11 and the multiple replaceable rivet adapters can also be achieved in the following ways: A. The rivet adapter is provided with an elastic block on the side facing the fixing part 11, and the fixing part 11 is provided with a slot that matches the elastic block on the side facing the tail connecting cylinder 3. The rivet adapter is detachably assembled to the fixing part 11 through the snap-fit ​​between the elastic block and the slot.

[0034] B. Both the rivet adapter and the fixing part 11 have coaxial pin holes on the side facing each other. The rivet adapter is detachably assembled to the fixing part 11 by a positioning pin that passes through the pin hole.

[0035] C. A permanent magnet is embedded in the side of the rivet adapter facing the fixing part 11. The fixing part 11 is provided with a metal adsorption surface that magnetically engages with the permanent magnet on the side facing the tail connecting cylinder 3. The rivet adapter is detachably assembled to the fixing part 11 through the magnetic engagement between the permanent magnet and the metal adsorption surface.

[0036] The procedure for conducting a fatigue test on the pop rivet 4 is as follows: (1) Rivet installation Tooling component matching and selection: Based on the type of blind rivet to be tested (first blind rivet or second blind rivet), select the corresponding rivet adapter (first rivet adapter 12 for the first blind rivet, or second rivet adapter 13 for the second blind rivet), and at the same time select a replaceable annular block structure sandwich supply block 5 that matches the diameter of the rivet shank (the sandwich supply block 5 must have a central through hole 7, and the diameter of the central through hole 7 must match the diameter of the blind rivet shank); if the blind rivet to be tested is a round-headed blind rivet or a blunt-headed blind rivet, select the first rivet adapter 12 with a flat end face and annular anti-slip texture on the surface; if the blind rivet to be tested is a countersunk blind rivet, select the second rivet adapter 13 with a conical end face (the conical angle of the conical structure is consistent with the head taper of the countersunk blind rivet). At the same time, it is confirmed that the blade 2 (the blade 2 is fixedly set on one side of the interlayer feeding block 5) has a U-shaped notch corresponding to the selected rivet adapter part, and the opening width of the U-shaped notch is adapted to the diameter of the rod of the pull rivet, the bottom surface of the U-shaped notch is flush with the end face of the central through hole 7 of the interlayer feeding block 5, and the axis of the central through hole 7 coincides with the axis of the U-shaped notch. The riveting thickness between the head connecting cylinder 1 and the tail connecting cylinder 3 can be adjusted by replacing the interlayer feeding block 5 with different thicknesses. Installation and riveting inspection of the blind rivet 4: Place the blind rivet to be tested into the rivet adapter detection hole opened on the selected rivet adapter part (the first rivet adapter part 12 corresponds to the first rivet adapter detection hole, and the second rivet adapter part 13 corresponds to the second rivet adapter detection hole), ensuring that the shank of the blind rivet to be tested simultaneously passes through the central through hole 7 of the interlayer supply block 5 (the rivet adapter detection hole and the central through hole 7 must be connected in sequence), and then use a riveting gun to rivet and install the blind rivet to be tested; after riveting, check whether the blind rivet to be tested is properly riveted and formed, and at the same time check whether the end face of the blind rivet to be tested and the rivet adapter part (the planar structure of the first rivet adapter part 12 or the conical structure of the second rivet adapter part 13) fit tightly, ensuring that the blind rivet to be tested has a certain preload. Connection of tooling to fatigue testing machine: The rivet adapter, equipped with the mandrel to be tested, is threadedly fitted to the fixing part 11 of the head connecting cylinder 1 (the rivet adapter has an external thread on the side facing the fixing part 11, and the fixing part 11 has an internal thread that matches the external thread on the side facing the tail connecting cylinder 3); Select a threaded connecting rod, and screw one end of the threaded connecting rod (with a third external thread) into the first internal thread hole of the fixing part 11 of the head connecting cylinder 1 (one end of the head connecting cylinder 1 has a first internal thread hole), until the end of the threaded connecting rod is flush with the end face of the head connecting cylinder 1; then screw the other end of the threaded connecting rod (with a third external thread) into the first internal thread hole of the fixing part 11 of the head connecting cylinder 1, until the end of the threaded connecting rod is flush with the end face of the head connecting cylinder 1; The threaded rod is screwed into the second internal thread hole of the tail connecting cylinder 3 (one end of the tail connecting cylinder 3 is provided with a second internal thread hole), and screwed until the end of the threaded connecting rod is flush with the end face of the tail connecting cylinder 3, ensuring that the head connecting cylinder 1 and the tail connecting cylinder 3 are firmly connected by the threaded connecting rod, and the tail inspection hole 8 opened on the side of the tail connecting cylinder 3 facing the head connecting cylinder 1 is connected to the rivet matching inspection hole and the center through hole 7 in sequence; finally, the assembled core-pulling rivet fatigue test fixture is installed in the corresponding position of the fatigue testing machine (the head connecting cylinder 1 and the tail connecting cylinder 3 are respectively fixedly connected to the corresponding positions of the fatigue testing machine by the threaded connecting rod). (2) System calibration Start the control software of the fatigue testing machine to perform zero-point calibration on the load sensor and displacement gauge equipped with the equipment to ensure the accuracy of load and displacement data during subsequent tests. After calibration, confirm that the system is in normal standby mode. (3) Experimental procedures Test parameter settings: In the control software interface of the fatigue testing machine, input the target load (the load type must be specified, such as tensile and compressive alternating load, etc.), frequency requirements (must conform to the rated frequency range of the equipment), and preset number of cycles according to the test plan. During the input process, the parameter values ​​must be checked repeatedly to avoid affecting the test results due to incorrect parameter settings. Test loading start: After confirming that the parameter settings are correct, start the loading program of the fatigue testing machine. During the loading process, the motor speed needs to be gradually increased so that the equipment operating frequency slowly reaches the set rated frequency. This avoids the test core-pulling rivet being subjected to instantaneous overload due to excessively rapid instantaneous speed increase, ensuring a smooth transition during the loading process. After the equipment operating frequency stabilizes at the rated frequency, the continuous loading stage begins. Real-time monitoring of test data: Throughout the entire test loading process, the changes in the load curve are observed in real time through the control software interface (it is necessary to ensure that the load curve is stable and there are no abnormal fluctuations or sudden changes) and the displacement change data fed back by the displacement gauge. At the same time, every abnormal fluctuation that occurs (including the time of the fluctuation, the magnitude of the load change, the amount of displacement change, etc.) is recorded, and it is promptly determined whether the abnormal fluctuation will affect the continuation of the test. (4) Trial termination conditions Failure Termination: During the test, if the tested mandrel is found to be completely broken through observation or data monitoring (this can be aided by phenomena such as a sudden drop in load curve and a sharp change in displacement), or if the axial displacement of the tested mandrel exceeds the preset safety threshold (this threshold needs to be set in advance according to the test standard or the usage requirements of the tested mandrel), the loading program of the fatigue testing machine will be stopped immediately, the test will be terminated, and the number of cycles, the final load value, and the displacement data at this time will be recorded. Completion and Termination: If the fatigue testing machine runs to the preset number of cycles, and the tested core-pulling rivet does not completely break or the axial displacement does not exceed the safety threshold during the entire test, and the load curve and displacement change remain stable, then the test is completed normally. Stop the equipment loading program, record the final number of cycles, the total load data and displacement data, and the test is terminated.

[0037] The above are merely embodiments of this utility model. This utility model is not limited to the field covered by this embodiment. Commonly known structures and characteristics in the solution are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of this utility model. These should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims. The specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A fatigue testing fixture for a blind rivet, comprising a connecting structure for connection to a fatigue testing machine, a paddle, and a sandwich feeding block, characterized in that: The connecting structure includes a head connecting cylinder and a tail connecting cylinder, which are respectively fixedly connected to corresponding positions of the fatigue testing machine via a threaded connecting rod. The interlayer feeding block is a replaceable annular block structure with a central through hole, and is positioned between the head connecting cylinder and the tail connecting cylinder. The paddle is fixedly positioned on one side of the interlayer feeding block. The head connecting cylinder includes a fixing part and multiple replaceable rivet adapter parts. The fixing part is fixedly connected to the fatigue testing machine via the threaded connecting rod. The rivet adapter part has an external thread on the side facing the fixing part, and an internal thread that matches the external thread on the side facing the tail connecting cylinder. The rivet adapter part is detachably assembled to the fixing part via threaded engagement. The rivet adapter part has a rivet adapter detection hole corresponding to the pull rivet. The tail connecting cylinder has a tail detection hole corresponding to the rivet adapter detection hole on the side facing the head connecting cylinder. The rivet adapter detection hole, the central through hole, and the tail detection hole are sequentially connected.

2. The fatigue testing fixture for a blind rivet according to claim 1, characterized in that: The blade is provided with a U-shaped notch corresponding to the rivet fitting part. The opening width of the U-shaped notch is adapted to the diameter of the shank of the pull rivet, and the bottom surface of the U-shaped notch is flush with the end face of the central through hole. The diameter of the central through hole is matched with the diameter of the shank of the pull rivet, and the axis of the central through hole coincides with the axis of the U-shaped notch.

3. The fatigue testing fixture for a blind rivet according to claim 1, characterized in that: The blind rivet includes a first blind rivet and a second blind rivet. The rivet adapter includes a first rivet adapter that adapts to the first blind rivet and a second rivet adapter that adapts to the second blind rivet. The first rivet adapter has a first external thread on the side facing the fixing part and a first rivet adapter detection hole corresponding to the first blind rivet on the side facing the tail connecting cylinder. The second rivet adapter has a second external thread on the side facing the fixing part and a second rivet adapter detection hole corresponding to the second blind rivet on the side facing the tail connecting cylinder. The first rivet adapter detection hole and the second rivet adapter detection hole are sequentially connected to the central through hole and the tail detection hole, respectively.

4. The fatigue testing fixture for a core-pulling rivet according to claim 3, characterized in that: The first pop rivet is a round-head pop rivet or a blunt-head pop rivet, and the second pop rivet is a countersunk pop rivet.

5. The fatigue testing fixture for a blind rivet according to claim 4, characterized in that: The end face of the first rivet adapter is a planar structure with annular anti-slip texture on its surface. The end face of the second rivet adapter is a conical structure that matches the head taper of the countersunk blind rivet, and the taper angle of the conical structure is consistent with the head taper of the countersunk blind rivet.

6. The fatigue testing fixture for a blind rivet according to claim 1, characterized in that: One end of the head connecting cylinder is provided with a first internal threaded hole, and one end of the threaded connecting rod is provided with a third external thread that is adapted to the first internal threaded hole. The threaded connecting rod is threadedly connected to the first internal threaded hole of the head connecting cylinder through the third external thread, and the end of the threaded connecting rod is flush with the end face of the head connecting cylinder.

7. The fatigue testing fixture for a blind rivet according to claim 6, characterized in that: One end of the tail connecting cylinder is provided with a second internal threaded hole, and the other end of the threaded connecting rod is provided with a fourth external thread that is adapted to the second internal threaded hole. The threaded connecting rod is threadedly connected to the second internal threaded hole of the tail connecting cylinder through the fourth external thread, and the end of the threaded connecting rod is flush with the end face of the tail connecting cylinder.

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