Bolt anti-loosening assembly and bolt bending fatigue test device provided with same

Abstract

The invention discloses a bolt anti-loosening assembly and a bolt bending fatigue test device provided with the bolt anti-loosening assembly. The anti-loosening assembly comprises a double-lug bolt clamp, a bolt stop piece, a nut stop piece, a plug pin and an auxiliary bolt. A hexagonal through hole and a plurality of bolt mounting holes with different angles are formed in the stop plate, the hexagonal through hole is used for limiting rotation of the bolt head or the nut, the bolt is inserted into the mounting holes and then makes contact with the double-lug piece to limit rotation of the stop plate, and the auxiliary bolt is used for locking the bolt and preventing the stop plate from axially moving; the bolt bending fatigue test device comprises the double-lug bolt clamp, a rod end joint bearing and an anti-loosening assembly, and the clamp and the bearing can be respectively arranged on a tensile testing machine for multi-angle bending fatigue test. According to the anti-loosening assembly, after the bolt is tightened at any angle, reliable anti-loosening can be achieved by selecting the corresponding bolt hole, the bolt structure is not damaged, the bolt can be effectively prevented from loosening and rotating in a test, and it is guaranteed that test data are accurate.

Description

Technical Field

[0001] This invention belongs to the field of bolt anti-loosening and structural component testing technology, specifically relating to a bolt anti-loosening component and a bolt bending fatigue testing device for installing the component. Background Technology

[0002] Bolts are a common type of fastener, widely used in automotive parts, rail transportation, shipbuilding, aerospace, and other fields. In actual working conditions, bolt fastener systems are often subjected to frequent lateral loads and lateral vibrations, inevitably leading to bolt loosening and rotation.

[0003] The essence of bolt loosening is that "the relative rotational driving force on the threaded pair is greater than the resistance constraint force." Under vibration conditions, periodic impact loads generate an alternating driving force F along the thread tangent, and the preload of the bolt and nut generates a frictional resistance f along the thread tangent. When the alternating driving force F is greater than the frictional resistance f, the thread will gradually loosen in a "step-by-step" manner. Under lateral loads, bolts are prone to thread eccentricity, simultaneously bearing bending and tensile stresses, leading to local driving force concentration and causing local thread slippage. Under long-term use, material wear between the bolt and the connected parts, and stiffness degradation of the bolt shank due to bending fatigue, lead to a decrease in bolt axial force, which in turn causes the frictional resistance f to gradually decrease, becoming unable to resist the continuous alternating driving force F, causing the bolt and nut to loosen.

[0004] Existing bolt anti-loosening technologies primarily rely on friction to resist driving forces. When the driving force increases or the resistance decreases, the risk of anti-loosening failure still increases significantly. Furthermore, while existing bolt anti-loosening technologies can prevent nut loosening to some extent, they cannot prevent bolt rotation. Mechanical locking anti-loosening, on the other hand, can directly restrict rotation through physical structures. After tightening the bolt and nut to a pre-selected torque, the hexagonal structure of the bolt head and nut can be fixed at any angle, making the installation of ordinary mechanical anti-loosening structures inconvenient. During bolt fatigue testing, without anti-loosening devices, bolts are highly susceptible to nut loosening and bolt rotation on the test platform, leading to cumulative fatigue damage distortion and a significant deviation between test data and the actual service life of the bolt. To overcome these shortcomings, we propose a multi-angle detachable component to prevent bolt and nut loosening and rotation. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a bolt anti-loosening component and a bolt bending fatigue testing device for installing the component, which is used to solve the problem of bolts being prone to loosening and rotation under transverse loads and to perform fatigue tests on bolts.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention first provides a bolt anti-loosening component, including a double-ear bolt clamp, a bolt stop plate, a nut stop plate, a fastening bolt, and an auxiliary bolt. The double-ear bolt clamp is provided with a pair of opposing ears, each ear having a bolt mounting hole. A bolt stop plate and a nut stop plate are respectively provided on the outer sides of the two ears. The fastening bolt passes sequentially through the bolt stop plate, the bolt mounting holes of the two ears, and the nut stop plate, and is then secured by a fastening nut. Both the bolt stop plate and the nut stop plate have features for engaging with the head of the fastening bolt or the fastening nut to restrict its axial rotation. The bolt stop and nut stop have hexagonal through holes, and multiple corresponding pin mounting holes are also provided on both sides of the hexagonal through holes. Pin assemblies are installed in the pin mounting holes on both sides of the bolt stop and nut stop. The pin assembly includes a threaded pin and a through pin. The tail end of the threaded pin passes through the pin mounting hole on one stop and is inserted into the pin mounting hole on the other stop. The through pin is inserted into the pin mounting hole where the tail end of the threaded pin is located and abuts against the tail end of the threaded pin, and is then connected and fixed by an auxiliary bolt.

[0008] Specifically, the bolt stop plate and the nut stop plate are also provided with circular blind holes. A bolt washer is placed in the circular blind hole of the bolt stop plate, and a nut washer is placed in the circular blind hole of the nut stop plate. The stop plates are CNC milled from aluminum alloy for easy modification and can be adapted to various bolt and lug sizes.

[0009] Specifically, the opposite side dimension of the hexagonal through hole of the bolt stop plate is slightly larger than the opposite side dimension of the bolt head, the opposite side dimension of the hexagonal through hole of the nut stop plate is slightly larger than the opposite side dimension of the nut, and the depth of the circular blind hole is slightly larger than the thickness of the bolt washer and the nut washer.

[0010] Preferably, the hexagonal through hole and the stop piece have two angle settings. The first angle setting is that the straight line containing at least one opposite side of the hexagonal through hole forms a 7.5° angle with the straight line containing the straight side of the stop piece. The second angle setting is that at least one opposite side of the hexagonal through hole is parallel to the straight side of the stop piece. A code mark is provided in the circular blind hole. The code mark indicates the angle setting of the hexagonal through hole. According to the two angle settings, the code mark can be designed as "I" and "II" respectively.

[0011] Specifically, the pin mounting holes are arranged in an arc shape on both sides of the hexagonal through hole, with the geometric center of the hexagonal through hole as the center. Multiple pin mounting holes are provided on each side. The axis of symmetry between multiple pin mounting holes on one side is parallel to the straight edge of the corresponding stop piece. The angle between the line connecting the geometric centers of two adjacent pin mounting holes on the same side and the geometric center of the hexagonal through hole is 15°. Two pin mounting holes on opposite sides whose geometric centers are collinear with the center of the inscribed circle of the hexagonal through hole form a corresponding pair. The pair of pin mounting holes whose distance is equal to the width of the double-ear bolt clamp and which is parallel to the double-ear bolt clamp is in the working state; the remaining pin mounting holes are idle.

[0012] Specifically, the minimum distance between the geometric center of the pin mounting hole and the hexagonal through hole is slightly greater than the distance from the center of the bolt mounting hole on the lug of the double lug bolt clamp to the free surface of the outer side of the lug, so that the inserted pin assembly can form a small gap with the outer surface of the lug for contact or limiting.

[0013] Specifically, the threaded pin has a threaded hole at its tail end, and the through pin has a through hole; the auxiliary bolt passes through the through hole and is screwed into the threaded hole to lock the threaded pin and the through pin; the depth of the threaded hole is longer than the length of the auxiliary bolt, and the diameter of the through pin is larger than the diameter of the auxiliary bolt.

[0014] This invention also provides a bolt bending fatigue testing device. This device uses the bolt anti-loosening component described in the above-mentioned technical solution to fix the test bolt. It includes a shoulder, a rod end spherical bearing, a bushing, and a tensile testing machine fixture. The bottom of the double-ear bolt fixture is fixedly connected to a shoulder, the bottom of which is an arc-shaped curved surface and is fixedly connected to a cylindrical long rod. The rod end spherical bearing includes a ball bearing and a rod end slidably connected to the ball bearing. The bushing is installed in the bolt mounting hole. A ball bearing is fitted onto the fastening bolt between the two bushings on the inner side of the lugs. The tensile testing machine fixture includes an upper fixture and a lower fixture. During the test, the cylindrical long rod is held by either the upper or lower fixture, and the rod end of the rod end spherical bearing is held by another fixture, thereby applying an alternating load along the Z-direction to the test bolt. , t For the load loading period, b , c is the load constant.

[0015] Specifically, the axial direction of the cylindrical long rod of the double-ear bolt clamp is set to be perpendicular to or at a specific angle to the plane where the root of its ear is located. When it is perpendicular to the plane, the test bolt is subjected to a lateral load. When it is at a specific angle, the test bolt is subjected to a lateral load with a certain deflection angle, so that the clamp meets the fatigue test requirements of multi-axis loading and complex working conditions.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The multi-angle detachable stop assembly for preventing bolt and nut loosening and rotation in this invention restricts the six degrees of freedom of the stop plate through the contact between the threaded hole pin, through hole pin, and auxiliary bolt combination plug installed on the stop plate and the double-ear bolt clamp. After the bolt is installed at any angle and tightened with any predefined tightening torque, the stop plate type and corresponding pin hole corresponding to the bolt and nut can be easily found through the eight pairs of pin mounting holes with different distributions on the two types of bolt stop plates and the two types of nut stop plates. The pin assembly achieves the fixation of the bolt and nut at forty-eight equally spaced angles on a circumference. Ultimately, it can prevent bolt loosening and rotation under different bolt installation angles, different nut tightening angles (i.e., different tightening torques and different preloads). During the bolt tightening process, the stop plate can be locked onto the double-ear bolt clamp by the pin assembly alone, simplifying the structure of the anti-loosening component, reducing manufacturing costs, facilitating disassembly and assembly, and improving efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a typical installation method of the bolt anti-loosening component of the present invention and a schematic diagram of the bolt bending fatigue testing device with the component installed. Figure 2 yes Figure 1 A cross-sectional view showing the installation method; Figure 3 This is a schematic diagram of the bolt bending fatigue testing device of the present invention installed on a tensile testing machine; Figure 4 This is a schematic diagram of the structure of the cylindrical rod of the double-ear bolt clamp in an embodiment of the present invention, where the axial direction of the rod is perpendicular to or at a specific angle to the plane containing the root of the ear piece. Figure 5 This is a schematic diagram of the hexagonal through hole and the stop piece being set at a first angle in an embodiment of the present invention; Figure 6 This is a schematic diagram of the second angle arrangement between the hexagonal through hole and the stop piece in an embodiment of the present invention; Figure 7 This is a schematic diagram of the latch assembly in an embodiment of the present invention; Figure 8 This is a schematic diagram illustrating various combinations of stop plates with two different angle settings in embodiments of the present invention.

[0019] In the diagram, 1. Double-ear bolt clamp; 2. Rod end spherical bearing; 3. Bolt stop plate; 4. Nut stop plate; 5. Fastening bolt; 6. Threaded hole pin; 7. Through hole pin; 8. Auxiliary bolt; 9. Bolt washer; 10. Nut washer; 11. Fastening nut; 12. Bushing; 13. Ball bearing; 14. Hexagonal through hole; 15. Pin mounting hole; 16. Circular blind hole; 17. Code marking; 18. Threaded hole; 19. Through hole; 20. Shoulder; 21. Circular curved surface; 22. Cylindrical long rod; 23. Upper clamp of tensile testing machine; 24. Lower clamp of tensile testing machine. Detailed Implementation

[0020] To facilitate understanding and implementation of the present invention by those skilled in the art, the various steps of the method proposed in this invention are described in detail below. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various modifications or alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0021] Example 1 like Figure 1 and Figure 2As shown, this embodiment discloses a bolt anti-loosening component and a bolt bending fatigue testing device equipped with the component, including a double-ear bolt clamp 1, a rod end spherical bearing 2, a bolt stop plate 3, a nut stop plate 4, a fastening bolt 5, an auxiliary bolt 8, a shoulder 20, and a tensile testing machine clamp; the double-ear bolt clamp 1 is provided with a pair of opposing ears, and bolt mounting holes are opened on the ears. The bushing 12 is installed in the bolt mounting holes. The fastening bolt 5 between the two bushings 12 on the inner side of the ears is fitted with a ball bearing 2. Bolt stop plates 3 and nut stop plates 4 are respectively provided on the outer sides of the two ears. The fastening bolt 5 passes through the bolt stop plate 3, the bolt mounting holes of the two ears, and the nut stop plate 4 in sequence and is fixed by the fastening nut 11. The bolt stop plate Both bolt stop 3 and nut stop 4 are provided with hexagonal through holes 14 for engaging with the head of fastening bolt 5 or fastening nut 11 to limit its axial rotation. On both sides of the hexagonal through holes 14, bolt stop 3 and nut stop 4 are also provided with multiple corresponding pin mounting holes 15. Pin assemblies are installed in the pin mounting holes 15 on both sides of bolt stop 3 and nut stop 4. The pin assembly includes a threaded pin 6 and a through pin 7. The tail end of the threaded pin 6 passes through the pin mounting hole 15 on one stop and is inserted into the pin mounting hole 15 on the other stop. The through pin 7 is inserted into the pin mounting hole 15 where the tail end of the threaded pin 6 is located and abuts against the tail end of the threaded pin 6 and is then connected and fixed by an auxiliary bolt. like Figure 3 As shown, the bottom of the double-ear bolt clamp 1 is fixedly connected to a shoulder 20. The bottom of the shoulder 20 is an arc-shaped curved surface 21 and a cylindrical long rod 22 is fixedly connected to it. The rod end spherical bearing 2 includes a ball bearing 13 and a rod end slidably connected to the ball bearing 13. The bushing 12 is installed in the bolt mounting hole. The ball bearing 2 is fitted on the fastening bolt 5 between the two bushings 12 on the inner side of the ear. The tensile testing machine clamp includes an upper clamp 23 and a lower clamp 24. During the test, the cylindrical long rod 22 is clamped by the upper clamp 23 or the lower clamp 24 of the tensile testing machine, and the rod end of the rod end spherical bearing 2 is clamped by another clamp, thereby applying an alternating load to the test bolt along the Z direction. , t For the load loading period, b , c is the load constant.

[0022] like Figure 4 As shown, the axial direction of the cylindrical long rod 22 of the double-ear bolt clamp 1 is set to be perpendicular to the plane where the root of its ear is located or at a specific angle such as 95° or 100°.

[0023] In this embodiment, the bolt stop plate 3 and the nut stop plate 4 are also provided with circular blind holes 16. A bolt washer 9 is placed in the circular blind hole 16 of the bolt stop plate 3, and a nut washer 10 is placed in the circular blind hole 16 of the nut stop plate 4.

[0024] When the test bolt is subjected to lateral load and lateral vibration, i.e., the axial load of the double-ear bolt clamp and the rod end of the rod end spherical bearing, and the magnitude of this load is greater than a certain limit, i.e. the frictional force generated by the preload cannot resist this load, this load will overcome the static friction between the connected parts and the ears, and the test bolt will inevitably rotate slightly. The pin assembly locks the bolt stop plate and the nut stop plate on the double-ear bolt clamp, thus basically restricting the degree of freedom of the stop plate. The hexagonal through hole of the bolt stop plate can restrict the relative rotation between the test bolt and the bolt stop plate, thereby preventing the test bolt from rotating relative to the double-ear bolt clamp. When the test bolt is subjected to lateral load, the nut will also loosen. The hexagonal through hole of the nut stop plate can prevent the nut from rotating, thereby preventing the nut from loosening.

[0025] Preferably, the opposite side dimension of the hexagonal through hole 14 of the bolt stop plate 3 is slightly larger than the opposite side dimension of the bolt head, and the opposite side dimension of the hexagonal through hole 14 of the nut stop plate 4 is slightly larger than the opposite side dimension of the nut; the depth of the circular blind hole 16 is slightly larger than the thickness of the bolt washer 9 and the nut washer 10; the minimum distance between the geometric center of the pin mounting hole 15 and the hexagonal through hole 14 is slightly larger than the distance from the center of the bolt mounting hole on the lug of the double lug bolt clamp 1 to the free surface of the outer side of the lug, so that the inserted pin assembly can form a small gap to fit or contact and limit with the outer surface of the lug.

[0026] In this embodiment, to prevent the stop plate from causing further structural damage to the test bolt when it is subjected to lateral load and lateral vibration, all components of the anti-loosening assembly are fitted with a small clearance, i.e., a certain buffer gap is reserved to prevent the bolt head and bolt stop plate from being damaged by the small amplitude sway of the bolt head and nut in the load direction Z when the test bolt is subjected to lateral load and lateral vibration, and the nut and nut stop plate from being damaged by the small amplitude sway. When the pin assembly is in close contact with the lug with a small gap, its movement in the Z direction can also ensure that when the bolt head and nut experience a small amplitude sway in the load direction Z, the stop plate can be displaced in the Z direction with the small amplitude sway of the bolt head and nut, further improving the buffering performance.

[0027] The hexagonal through hole 14 and the stop plate have two angle settings, such as... Figure 5 As shown, in the first angle setting configuration, at least one opposite side of the hexagonal through hole 14 forms a 7.5° angle with the straight side of the stop piece; as... Figure 6As shown, in the second angle setting configuration, at least one opposite side of the hexagonal through hole 14 is parallel to the straight edge of the stop plate; a code mark 17 is provided inside the circular blind hole 16, and the code mark 17 indicates the angle setting of the hexagonal through hole 14; as shown Figure 8 The diagram shows various combinations of stop plates with two different angle settings. Figure 8 Figure a is a structural diagram of a bolt stop and a nut stop that both use the first type of angle setting. Figure 8 Figure b shows a schematic diagram of a bolt stop plate using the first angle setting and a nut stop plate using the second angle setting. Figure 8 Figure c is a structural diagram of bolt stop plates and nut stop plates that both use the second angle setting form.

[0028] In this embodiment, as Figure 5 As shown, the pin mounting holes 15 are distributed in an arc shape on both sides of the hexagonal through hole 14 with the geometric center of the hexagonal through hole 14 as the center. There are multiple holes on each side. The axis of symmetry between the multiple pin mounting holes 15 on a single side is parallel to the straight edge of the stop piece. The angle between the line connecting the geometric center of two adjacent pin mounting holes 15 on the same side and the geometric center of the hexagonal through hole 14 is 15°.

[0029] like Figure 7 As shown, the threaded pin 6 has a threaded hole 18 at its tail end, and the through pin 7 has a through hole 19; the auxiliary bolt 8 passes through the through hole 19 and is screwed into the threaded hole 18 to lock the threaded pin 6 and the through pin 7; the depth of the threaded hole 18 is longer than the length of the auxiliary bolt 8, and the diameter of the through pin 7 is larger than the diameter of the auxiliary bolt 8.

[0030] To verify the anti-loosening effect of the locking component of the present invention for preventing bolts and nuts from loosening and rotating, a set of comparative experiments were conducted: The anti-loosening component of the present invention was installed on a bolt bending fatigue testing device equipped with an M8 bolt. The bolt was preloaded with 8000N and fixed with a double-ear bolt clamp. An alternating load with a zero point of 3000N, an amplitude of 12000N, and a frequency of 2Hz was applied to the rod end of the rod end spherical bearing. After 5 hours of testing, the nut loosening angle of the bolt without the anti-loosening component reached 30° and the bolt rotation angle reached 90°. In contrast, the loosening angle and bolt rotation angle of the anti-loosening component of the present invention were less than 1°, proving that the anti-loosening component of the present invention can completely resist the alternating driving force and effectively prevent the nut from loosening and the bolt from rotating. After the experiment, the auxiliary nut connecting the two pins was loosened, and the pins and the stop plate could be easily disassembled, proving the disassembly and maintainability of the stop component of the present invention.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A bolt anti-loosening component, characterized in that, The device includes a double-ear bolt clamp (1), a bolt stop plate (3), a nut stop plate (4), a fastening bolt (5), and an auxiliary bolt (8). The double-ear bolt clamp (1) is provided with a pair of opposing ears, each ear having a bolt mounting hole. A bolt stop plate (3) and a nut stop plate (4) are respectively provided on the outer sides of the two ears. The fastening bolt (5) passes sequentially through the bolt stop plate (3), the bolt mounting holes of the two ears, and the nut stop plate (4) before being fixed by a fastening nut (11). Both the bolt stop plate (3) and the nut stop plate (4) have hexagonal through holes (14) for engaging with the head of the fastening bolt (5) or the fastening nut (11) to restrict its axial rotation. The bolt stop plate (3) and nut stop plate (4) are provided with multiple corresponding pin mounting holes (15) on both sides of the hexagonal through hole (14); a pin assembly is installed in the pin mounting holes (15) on both sides of the bolt stop plate (3) and nut stop plate (4). The pin assembly includes a threaded pin (6) and a through pin (7). The tail end of the threaded pin (6) passes through the pin mounting hole (15) on one stop plate and is inserted into the pin mounting hole (15) on the other stop plate. The through pin (7) is inserted into the pin mounting hole (15) where the tail end of the threaded pin (6) is located and abuts against the tail end of the threaded pin (6) and is then connected and fixed by an auxiliary bolt.

2. The bolt anti-loosening assembly according to claim 1, characterized in that: The bolt stop plate (3) and the nut stop plate (4) are also provided with circular blind holes (16). A bolt washer (9) is placed in the circular blind hole (16) of the bolt stop plate (3), and a nut washer (10) is placed in the circular blind hole (16) of the nut stop plate (4).

3. The bolt anti-loosening assembly according to claim 2, characterized in that: The opposite side dimension of the hexagonal through hole (14) of the bolt stop plate (3) is slightly larger than the opposite side dimension of the bolt head; the opposite side dimension of the hexagonal through hole (14) of the nut stop plate (4) is slightly larger than the opposite side dimension of the nut; the depth of the circular blind hole (16) is slightly larger than the thickness of the bolt washer (9) and the nut washer (10).

4. The bolt anti-loosening assembly according to claim 3, characterized in that: The hexagonal through hole (14) and the stop plate have two angle settings. The first angle setting is that the straight line containing at least one opposite side of the hexagonal through hole (14) forms a 7.5° angle with the straight line containing the straight side of the stop plate. The second angle setting is that at least one opposite side of the hexagonal through hole (14) is parallel to the straight side of the stop plate. The circular blind hole (16) is provided with a code mark (17), which indicates the angle setting of the hexagonal through hole (14).

5. The bolt anti-loosening assembly according to claim 1 or 4, characterized in that: The pin mounting holes (15) are distributed in an arc shape on both sides of the hexagonal through hole (14) with the geometric center of the hexagonal through hole (14) as the center. There are multiple holes on each side. The axis of symmetry between the multiple pin mounting holes (15) on one side is parallel to the straight edge of the stop plate. The angle between the line connecting the geometric center of two adjacent pin mounting holes (15) on the same side and the geometric center of the hexagonal through hole (14) is 15°.

6. The bolt anti-loosening assembly according to claim 5, characterized in that: The minimum distance between the geometric center of the pin mounting hole (15) and the hexagonal through hole (14) is slightly greater than the distance from the center of the bolt mounting hole on the ear of the double ear bolt clamp (1) to the free surface of the outer ear, so that the inserted pin assembly can form a small gap with the outer surface of the ear to fit or contact and limit.

7. The bolt anti-loosening assembly according to claim 1, characterized in that: The threaded hole pin (6) has a threaded hole (18) at its tail end, and the through hole pin (7) has a through hole (19); the auxiliary bolt (8) passes through the through hole (19) and is screwed into the threaded hole (18) to lock the threaded hole pin (6) and the through hole pin (7); the depth of the threaded hole (18) is longer than the length of the auxiliary bolt (8), and the diameter of the through hole pin (7) is larger than the diameter of the auxiliary bolt (8).

8. A bolt bending fatigue testing device, comprising using a bolt anti-loosening assembly as described in any one of claims 1-7 to fix the bolt under test for bending fatigue testing, characterized in that, The test includes a shoulder (20), a rod end spherical bearing (2), a bushing (12), and a tensile testing machine fixture. The bottom of the double-ear bolt fixture (1) is fixedly connected to the shoulder (20). The bottom of the shoulder (20) is an arc surface (21) and a cylindrical long rod (22) is fixedly connected to it. The rod end spherical bearing (2) includes a ball bearing (13) and a rod end that is slidably connected to the ball bearing (13). The bushing (12) is installed in the bolt mounting hole. The ball bearing (2) is fitted on the fastening bolt (5) between the two bushings (12) on the inner side of the ear. The tensile testing machine fixture includes an upper tensile testing machine fixture (23) and a lower tensile testing machine fixture (24). During the test, the cylindrical long rod (22) is held by the upper tensile testing machine fixture (23) or the lower tensile testing machine fixture (24). The rod end of the rod end spherical bearing (2) is held by another fixture, thereby applying an alternating load to the test bolt along the Z direction.

9. The bolt bending fatigue testing apparatus according to claim 8, characterized in that: The axial direction of the cylindrical rod (22) of the double-ear bolt clamp (1) is set to be perpendicular to or at a specific angle relative to the plane where the root of its ear is located.

10. The bolt bending fatigue testing apparatus according to claim 8 or 9, characterized in that: An alternating load is applied to the test bolt along the Z-direction. , t For the load loading period, b , c is the load constant.

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