A bending fatigue test fixture

Abstract

This invention provides a bending fatigue testing fixture, belonging to the field of testing fixture technology. It includes a supporting beam, a sample holder, a locking plate, a fixing member, and an upper pressure head. Two sample holders are provided and mounted on the supporting beam. The locking plate is slidably mounted on the sample holder, and the fixing member is mounted on the sample holder. The fixing member is used to lock the plate, pressing the sample against the sample holder and fixing the locking plate to the sample holder. The upper pressure head slides towards the supporting beam to press down on the sample. The sample holder includes a reference holder and a reference sliding holder. The reference holder is slidably mounted on the supporting beam, and the reference sliding holder is located within and slidably mounted on the reference holder. The locking plate is mounted on the reference sliding holder. This invention has the advantage of improving the accuracy of test results.

Description

Technical Field

[0001] This invention relates to the field of testing fixture technology, and more specifically, to a bending fatigue testing fixture. Background Technology

[0002] Bending fatigue testing is an important method for evaluating a material's resistance to fracture under alternating loads, and it is widely used in the performance testing of composite materials, metallic materials, and polymer materials. Currently, bending fatigue testing mainly relies on static bending testing fixtures. These fixtures typically employ a fixed indenter and a fixed bottom support structure, and are suitable for determining static mechanical properties such as the bending modulus and bending strength of materials.

[0003] However, the bottom support indenter of the static bending fatigue fixture is fixed. During the test, due to the different bending deformation of the specimen, the fixed support indenter at the bottom cannot change with the bending deformation of the specimen. The support indenter span set before the test will slide outward and become larger, resulting in deviation of the test results. Summary of the Invention

[0004] The purpose of this invention is to provide a bending fatigue testing fixture that can improve the accuracy of test results.

[0005] This invention is achieved through the following technical solution: A bending fatigue testing fixture includes a support beam, a specimen fixing seat, a locking plate, a fixing component, and an upper pressure head; two specimen fixing seats are provided and are disposed on the support beam, the specimen fixing seats are slidably disposed on the support beam, and the specimen fixing seats slide along the length direction of the support beam. The locking plate is slidably mounted on the sample fixing seat, and the sample to be tested is placed between the locking plate and the sample fixing seat; the fixing member is mounted on the sample fixing seat, and the fixing member is used to fix the locking plate on the sample fixing seat after the locking plate presses the sample on the sample fixing seat. The upper pressure head is located above the support beam and in the middle of the sample. The upper pressure head slides toward the support beam and presses down on the sample. The sample fixing seat includes a reference fixing seat and a reference sliding seat. The reference fixing seat is slidably mounted on the support beam, and the reference sliding seat is mounted inside the reference fixing seat and slidably mounted inside the reference fixing seat. The locking pressure plate is mounted on the reference sliding seat. When the upper pressure head presses down to bend the sample, the bending of the sample causes the reference sliding seat to slide within the reference fixed seat, thereby adaptively adjusting the position of the reference sliding seat as the sample bends.

[0006] Optionally, the reference fixing seat includes two first sliding seats and a connecting plate. The two first sliding seats are located on both sides of the supporting crossbeam. The connecting plate is located between the two first sliding seats and is used to connect the two first sliding seats. The reference sliding seat is located between the first sliding seat and the connecting plate and is supported on the supporting crossbeam. The first sliding seat has a first guide wheel rotatably arranged on the surface of the first sliding seat facing the reference sliding seat. The reference sliding seat has a first groove for the first guide wheel to roll. The two ends of the first groove are closed to limit the movement range of the reference sliding seat within the first sliding seat.

[0007] Optionally, T-slots are provided on both sides of the supporting crossbeam. A fixing plate is provided on the side of the first sliding seat facing the supporting crossbeam. The fixing plate is located in the T-slot. A fixing screw is threaded onto the first sliding seat. The fixing plate is rotatably disposed at the end of the fixing screw. The fixing screw drives the fixing plate to abut against the inner wall of the T-slot, thereby fixing the first sliding seat onto the supporting crossbeam.

[0008] Optionally, the top of the supporting beam is provided with a second sliding groove, and the bottom of the reference sliding seat is rotatably provided with a second guide wheel, which is supported by the bottom wall of the second sliding groove; the bottom of the connecting plate is provided with a third guide wheel, which is pressed against the top of the reference sliding seat.

[0009] Optionally, the top of the reference sliding seat is recessed and formed with an installation groove. A receiving roller is rotatably mounted on the reference sliding seat through the installation groove. The sample is received on the receiving roller. Both ends of the receiving roller are located outside the installation groove. A first mounting plate is fixedly mounted on both sides of the receiving roller. The first mounting plate is located outside the installation groove. The locking pressure plate is located between the two first mounting plates. A strip groove is opened on the first mounting plate. The fixing member includes a fixing bolt. The fixing bolt passes through the strip groove and is threaded to the locking pressure plate.

[0010] Optionally, the fixing component further includes a pressing screw and a sleeve ring. The sleeve ring is located in the strip groove and the fixing bolt passes through the sleeve ring. The pressing screw is threadedly connected to the first mounting plate and the sleeve ring is rotatably disposed at the end of the pressing screw. The pressing screw drives the sleeve ring to move, which in turn drives the fixing bolt to move, which in turn drives the locking plate to press down the sample.

[0011] Optionally, a second mounting plate is provided between the two first mounting plates. The second mounting plate is located above the locking pressure plate and there is an installation gap between the second mounting plate and the locking pressure plate. A pressing screw is threadedly connected to the middle of the second mounting plate. A lower pressure plate is rotatably provided at the end of the pressing screw. The lower pressure plate is used to press the middle of the locking pressure plate so that the locking pressure plate is attached to the sample.

[0012] Optionally, both the reference sliding seat and the support beam are equipped with a scale, with the zero position of the scale located in the middle and the readings marked towards both sides.

[0013] Optionally, the receiving roller is provided with two adjusting plates. The adjusting plates are arc-shaped and their inner rings are attached to the receiving roller. The thickness of the adjusting plates is less than the thickness of the sample. The adjusting plates are slidably disposed on the receiving roller and slide along a direction parallel to the length of the receiving roller. The receiving roller is provided with a driving member, which is used to drive the adjusting plates on both sides to slide and move the sample to the middle of the receiving roller and to laterally clamp the sample.

[0014] Optionally, the driving component includes a bidirectional lead screw rotatably mounted on a reference sliding seat, and the outer ring of the adjusting plate is integrally formed with a connecting block, which is threadedly connected to the bidirectional lead screw.

[0015] The technical solution of the present invention has at least the following advantages and beneficial effects: During fatigue testing, the specimen is placed between the reference sliding seat and the locking plate. A fixing element acts on the locking plate, securing the specimen to the reference sliding seat. The upper pressure head then moves towards the specimen and contacts it, causing the specimen to bend towards the supporting beam. The upper pressure head then moves upward, allowing the specimen to recover its deformation. This process is repeated to complete the fatigue test. When the upper pressure head contacts the specimen and causes it to bend, the bending motion causes the reference sliding seats on both sides to move inward. When the upper pressure head moves upward and separates from the specimen, the specimen recovers its deformation, pushing the reference sliding seats on both sides to move outward. This allows the reference sliding seats to adapt to the bending process of the specimen, solving the technical problem of mismatch between the specimen deformation and the span change of the reference sliding seats during the test, thus improving the accuracy of the test results. During the deformation process, the part of the sample pressed under the locking plate is bent by the receiving roller, causing the middle part of the sample to rotate. This makes the end of the sample adapt to the bending state of the middle part of the sample, thereby reducing the possibility of repeated bending at the junction of the clamped and unclamped parts of the sample, reducing the possibility of sample ablation and blackening leading to damage, and improving the accuracy of the test results. Attached Figure Description

[0016] Figure 1 This is a planar schematic diagram of a bending fatigue testing fixture according to the present invention; Figure 2 This is a schematic diagram of the overall structure of a bending fatigue testing fixture according to the present invention; Figure 3 This is a partially enlarged schematic diagram of a bending fatigue testing fixture according to the present invention; Figure 4 This is a schematic diagram of the result of the first slide in a bending fatigue testing fixture of the present invention; Figure 5 This is a schematic diagram of the results of the reference sliding seat in the bending fatigue testing fixture of the present invention; Figure 6 This is a schematic diagram of the lower pressure plate in a bending fatigue testing fixture of the present invention; Figure 7 This is an enlarged schematic diagram of the lower pressure plate in a bending fatigue testing fixture of the present invention.

[0017] Figure label: 1. Support beam; 2. Sample holder; 21. Reference holder; 211. First sliding seat; 212. Connecting plate; 22. Reference sliding seat; 221. First mounting seat; 222. Second mounting seat; 3. Lock the pressure plate; 4. Fasteners; 41. Fixing bolts; 42. Pressing screws; 43. Connecting rings; 5. Upper pressure head; 6. Connector; 7. Sample; 8. First guide wheel; 9. First slide groove; 10. T-slot; 11. Second slide groove; 12. Second guide wheel; 13. Third guide wheel; 14. Mounting groove; 15. Receiving roller; 16. First mounting plate; 17. Strip groove; 18. Second mounting plate; 19. Pressing screw; 20. Lower pressure plate; 23. Scale; 24. Adjusting plate; 25. Bidirectional lead screw. Detailed Implementation

[0018] The following is for reference Figures 1-7 As shown in the illustration, and further explained with reference to specific embodiments, this embodiment provides a bending fatigue testing fixture, referring to... Figure 1 and Figure 2 It includes a support beam 1, a sample fixing seat 2, a locking pressure plate 3, a fixing component 4, and an upper pressure head 5; the bottom of the support beam 1 is provided with a connector 6, and the support beam 1 is connected to the testing equipment through the connector 6; there are two sample fixing seats 2 and they are set on the support beam 1; the sample fixing seats 2 are slidably set on the support beam 1 and slide along the length direction of the support beam 1. Reference Figure 1 and Figure 2 The locking plate 3 is slidably set on the sample fixing seat 2, and the sample 7 to be tested is placed between the locking plate 3 and the sample fixing seat 2; the fixing member 4 is set on the sample fixing seat 2, and the fixing member 4 is used to fix the locking plate 3 on the sample fixing seat 2 after the locking plate 3 presses the sample 7 on the sample fixing seat 2. Reference Figure 1 and Figure 2The upper pressure head 5 is located above the support beam 1 and in the middle of the sample 7. Furthermore, the top of the upper pressure head 5 is provided with a connector 6. The upper pressure head 5 is connected to the testing equipment through the connector 6. The upper pressure head 5 slides towards the support beam 1 and presses down on the sample 7. Reference Figure 1 and Figure 2 The sample fixing seat 2 includes a reference fixing seat 21 and a reference sliding seat 22. The reference fixing seat 21 is slidably mounted on the support beam 1, and the reference sliding seat 22 is mounted inside the reference fixing seat 21 and is slidably mounted inside the reference fixing seat 21. The locking pressure plate 3 is mounted on the reference sliding seat 22. When the upper pressure head 5 presses down to bend the sample 7, the bending of the sample 7 causes the reference sliding seat 22 to slide within the reference fixed seat 21, thereby adaptively adjusting the position of the reference sliding seat 22 as the sample 7 bends.

[0019] During the fatigue test of specimen 7, specimen 7 is placed between the reference sliding seat 22 and the locking plate 3. The locking plate 3 is then fixed by the fixing member 4, which fixes specimen 7 on the reference sliding seat 22. Subsequently, the upper pressure head 5 moves towards specimen 7 and abuts against specimen 7, causing specimen 7 to bend towards the support beam 1. Then, the upper pressure head 5 moves upward, at which point specimen 7 recovers its deformation. The above process is repeated to complete the fatigue test of specimen 7. When the upper pressure head 5 abuts against specimen 7 and causes specimen 7 to bend, the bending of specimen 7 causes the reference sliding seats 22 on both sides to move inward. When the upper pressure head 5 moves upward and separates from specimen 7, specimen 7 recovers its deformation and pushes the reference sliding seats 22 on both sides to move outward. This allows the reference sliding seats 22 on both sides to adapt to the bending process of specimen 7, thus solving the technical problem of mismatch between the deformation of specimen 7 and the span change of the reference sliding seats 22 on both sides during the test, and improving the accuracy of the test results.

[0020] Reference Figure 2 , Figure 3 and Figure 4In this embodiment, the reference fixing base 21 includes two first sliding seats 211 and a connecting plate 212. The two first sliding seats 211 are located on both sides of the supporting beam 1 and are slidably disposed on the supporting beam 1. The connecting plate 212 is located between the two first sliding seats 211 and is used to connect the two first sliding seats 211. The reference sliding seat 22 is located between the first sliding seats 211 and the connecting plate 212 and is supported on the supporting beam 1. The first sliding seat 211 has a first guide wheel 8 rotatably disposed on the surface facing the reference sliding seat 22. The reference sliding seat 22 has a first groove 9 for the first guide wheel 8 to roll. The two ends of the first groove 9 are closed. The movement range of the reference sliding seat 22 within the first sliding seat 211 is limited. When the sample 7 drives the reference sliding seat 22 to move back and forth within the reference fixed seat 21, the first guide wheel 8 rolls back and forth within the first sliding groove 9. Since the two ends of the first sliding groove 9 are closed, the first guide wheel 8 only moves within the first sliding groove 9, thus limiting the movement range of the reference sliding seat 22. This allows the reference sliding seats 22 on both sides to move at the same speed and along the same path, making it easier for the reference sliding seats 22 on both sides to return to their initial positions during the deformation recovery process of the sample 7. This ensures that the pressure head always acts on the middle of the sample 7, thereby improving the accuracy of the fatigue test results of the sample 7.

[0021] Reference Figure 2 and Figure 3 In this embodiment, T-slots 10 are provided on both sides of the supporting beam 1. A fixing plate is provided on the side of the first sliding seat 211 facing the supporting beam 1. The fixing plate is located in the T-slot 10. A fixing screw is threaded onto the first sliding seat 211. The fixing plate is rotatably mounted at the end of the fixing screw. The fixing screw drives the fixing plate to abut against the inner wall of the T-slot 10, thereby fixing the first sliding seat 211 onto the supporting beam 1. The length between the two reference fixing seats 21 is adjusted according to the length of the test specimen 7. When the reference fixing seat 21 moves to the required position, the fixing screw is rotated. The fixing screw drives the fixing plate to move in the T-slot and abut against the inner wall of the T-slot, thereby fixing the reference fixing seat 21 onto the supporting beam 1, which facilitates the fatigue test of the specimen 7.

[0022] Reference Figure 3 In this embodiment, a second groove 11 is provided at the top of the supporting beam 1, and a second guide wheel 12 is rotatably provided at the bottom of the reference sliding seat 22, which is supported by the bottom wall of the second groove 11. A third guide wheel 13 is provided at the bottom of the connecting plate 212, which is pressed against the top of the reference sliding seat 22. Under the action of the second guide wheel 12 and the second groove 11, the friction between the reference sliding seat 22 and the supporting beam 1 is reduced, which facilitates the bending of the sample 7 to drive the reference to slide back and forth on the supporting beam 1, so that the span between the locking plates 3 and the sample 7 is always kept consistent, thereby improving the accuracy of fatigue testing.

[0023] Reference Figure 4 , Figure 5 and Figure 6 In this embodiment, the top of the reference sliding seat 22 is recessed with an installation groove 14. A receiving roller 15 is rotatably mounted on the reference sliding seat 22 through the installation groove 14. The sample 7 is received on the receiving roller 15. Both ends of the receiving roller 15 are located outside the installation groove 14. A first mounting plate 16 is fixedly mounted on both sides of the receiving roller 15. The first mounting plate 16 is located outside the installation groove 14. The locking pressure plate 3 is located between the two first mounting plates 16. A strip groove 17 is opened on the first mounting plate 16. The fixing member 4 includes a fixing bolt 41. The fixing bolt 41 passes through the strip groove 17 and is threadedly connected to the locking pressure plate 3. After the sample 7 is placed between the receiving roller 15 and the locking plate 3, the locking plate 3 is pressed down to make it tightly press against the sample 7. Then, the fixing bolt 41 is rotated, and the fixing bolt 41 enters the locking plate 3 until the head of the fixing bolt 41 presses against the first mounting plate 16, thus fixing the locking plate 3 on the first mounting plate 16. This fixes the sample 7 between the receiving roller 15 and the locking plate 3, making the operation simple and convenient. On the other hand, under the action of the receiving roller 15, the locking plate 3 adapts to the bending process of the sample 7 during the bending process, thereby reducing the possibility of the sample 7 bending repeatedly during the bending process, reducing the possibility of the sample 7 breaking, and improving the accuracy of the test results of the sample 7.

[0024] In the embodiments of this application, reference is made to Figure 4 and Figure 5 The reference sliding seat 22 includes a first mounting seat 221 and a second mounting seat 222. The first mounting seat 221 is slidably disposed within the reference fixed seat 21. The locking pressure plate 3 and the receiving roller 15 are both disposed on the second mounting seat 222. Furthermore, the second mounting seat 222 is rotatably disposed on the first mounting seat 221. The rotation axis of the second mounting seat 222 is perpendicular to the first mounting seat 221. Two receiving rollers 15 are disposed on the second mounting seat 222. The two receiving rollers 15 are parallel to each other. The diameters of the two receiving rollers 15 are 22 mm, 25 mm or other diameters, respectively, to accommodate samples 7 of different thicknesses.

[0025] Reference Figure 4 , Figure 6 and Figure 7In this embodiment, to improve the fixing effect of the locking plate 3 on the sample 7, the fixing member 4 further includes a pressing screw 42 and a sleeve ring 43. The sleeve ring 43 is located in the strip groove 17 and the fixing bolt 41 passes through the sleeve ring 43. The pressing screw 42 is threadedly connected to the first mounting plate 16 and the sleeve ring 43 is rotatably disposed at the end of the pressing screw 42. The pressing screw 42 drives the sleeve ring 43 to move, which in turn drives the fixing bolt 41 to move, which in turn drives the locking plate 3 to press down on the sample 7. When the sample 7 is placed on the receiving roller 15 and the locking plate 3, the fixing plate 43 can be used to fix the sample 7. After plate 3 is applied, the pressing screw 42 is rotated, which drives the sleeve ring 43 to move vertically within the strip groove 17. This causes the fixing bolt 41 and the locking plate 3 to move toward the sample 7, thus pressing the locking plate 3 onto the sample 7. Then, the fixing bolt 41 is rotated, locking the locking plate 3 onto the first mounting plate 16, thus completing the fixing of the sample 7. In the above process, the sample 7 is fixed under the combined action of the fixing bolt 41 and the pressing screw 42, thereby improving the fixing effect of the sample 7.

[0026] Reference Figure 4 , Figure 6 and Figure 7 In this embodiment, because the width of the locking plate 3 is greater than the width of the sample 7, and force is applied to both sides of the locking plate 3 while the middle part of the locking plate 3 is supported by the sample 7, when the locking plate 3 presses against the sample 7, the middle part of the locking plate 3 will bulge outward in the direction away from the sample 7, resulting in a reduction in the contact area between the locking plate 3 and the sample 7. This reduces the frictional force that the locking plate 3 can apply to the sample 7. When the sample 7 is bent due to the upper pressure head 5, it is easy for the sample 7 and the locking plate 3 to have relative... Slippage can significantly reduce the accuracy of test results. Therefore, in this embodiment, a second mounting plate 18 is provided between the two first mounting plates 16. The second mounting plate 18 is located above the locking plate 3, and an installation gap is left between the second mounting plate 18 and the locking plate 3. A pressing screw 19 is threadedly connected to the middle of the second mounting plate 18, and a lower pressing plate 20 is rotatably provided at the end of the pressing screw 19. The lower pressing plate 20 is used to press against the middle of the locking plate 3, so that the locking plate 3 is attached to the sample 7. After the locking plate 3 has fixed the sample 7, the pressing screw 19 is rotated. The pressing screw 19 drives the lower pressing plate 20 to move towards the locking plate 3 and press against the middle of the locking plate 3, so that the middle of the locking plate 3 is in close contact with the sample 7, thereby increasing the contact area between the locking plate 3 and the sample 7, and thus improving the fixing effect of the locking plate 3 on the sample 7.

[0027] Reference Figure 4 , Figure 6 and Figure 7During the test, in order to improve the accuracy of the test results, the sample 7 needs to be located in the middle of the two reference sliding seats 22 and the receiving roller 15, so that the pressure head can act on the middle of the sample 7 and improve the accuracy of the test results. Therefore, in this embodiment, a scale 23 is provided on both the reference sliding seat 22 and the support beam 1. The zero position of the scale 23 is located in the middle and the reading is marked towards both sides.

[0028] Reference Figure 6 and Figure 7 When the sample 7 is placed on the receiving roller 15, the position of the sample 7 on the receiving roller 15 is adjusted by the scale 23. However, in the above process, it is difficult for the length direction of the sample 7 to be perpendicular to the length direction of the receiving roller 15, which causes the sample 7 to easily deviate on the receiving roller 15 when the pressure head presses down on the sample 7. Therefore, in this embodiment, two adjusting plates 24 are provided on the receiving roller 15. The adjusting plates 24 are arc-shaped and the inner ring is attached to the receiving roller 15. Furthermore, the adjusting plates 24 are perpendicular to the receiving roller 15. The thickness of the adjusting plates 24 is less than the thickness of the sample 7. The adjusting plates 24 are slidably disposed on the receiving roller 15. The adjusting plates 24 slide along the length direction parallel to the receiving roller 15. A driving member is provided on the receiving roller 15. The driving member is used to drive the adjusting plates 24 on both sides to slide and move the sample 7 to the middle of the receiving roller 15 and to clamp the sample 7 laterally. Reference Figure 6 and Figure 7 The driving component includes a bidirectional lead screw 25 rotatably mounted on a reference sliding seat 22, and an integrally formed connecting block on the outer ring of the adjusting plate 24, which is threadedly connected to the bidirectional lead screw 25.

[0029] After the sample 7 is placed on the receiving roller 15, the double-acting screw 25 is rotated. The double-acting screw 25 drives the connecting blocks on both sides to move on the receiving roller 15. The movement of the connecting blocks drives the adjusting plate 24 to move towards each other on the receiving roller 15 to adjust the position of the sample 7 on the receiving roller 15. On the one hand, the sample 7 is located in the middle of the receiving roller 15, and on the other hand, the length direction of the sample 7 is perpendicular to the length direction of the receiving roller 15, which facilitates the subsequent fatigue test process of the sample 7.

[0030] The implementation principle of a bending fatigue testing fixture according to an embodiment of the present invention is as follows: During the fatigue test of specimen 7, specimen 7 is placed between the reference sliding seat 22 and the locking plate 3. The locking plate 3 is then fixed by the fixing member 4, which fixes specimen 7 on the reference sliding seat 22. Subsequently, the upper pressure head 5 moves towards specimen 7 and abuts against specimen 7, causing specimen 7 to bend towards the support beam 1. Then, the upper pressure head 5 moves upward, at which point specimen 7 recovers its deformation. The above process is repeated to complete the fatigue test of specimen 7. When the upper pressure head 5 abuts against specimen 7 and causes specimen 7 to bend, the bending of specimen 7 causes the reference sliding seats 22 on both sides to move inward. When the upper pressure head 5 moves upward and separates from specimen 7, specimen 7 recovers its deformation and pushes the reference sliding seats 22 on both sides to move outward. This allows the reference sliding seats 22 on both sides to adapt to the bending process of specimen 7, thus solving the technical problem of mismatch between the deformation of specimen 7 and the span change of the reference sliding seats 22 on both sides during the test, and improving the accuracy of the test results.

Claims

1. A bending fatigue testing fixture, characterized in that, It includes a support beam (1), a sample holder (2), a locking plate (3), a fastener (4), and an upper pressure head (5); there are two sample holders (2) and they are set on the support beam (1). The sample holders (2) are slidably set on the support beam (1) and slide along the length of the support beam (1). The locking plate (3) is slidably set on the sample fixing seat (2), and the sample (7) to be tested is placed between the locking plate (3) and the sample fixing seat (2); the fixing member (4) is set on the sample fixing seat (2), and the fixing member (4) is used to lock the plate (3) to press the sample (7) on the sample fixing seat (2) and then fix the locking plate (3) on the sample fixing seat (2); The upper pressure head (5) is located above the support beam (1) and in the middle of the sample (7). The upper pressure head (5) slides toward the support beam (1) and presses down on the sample (7). The sample fixing seat (2) includes a reference fixing seat (21) and a reference sliding seat (22). The reference fixing seat (21) is slidably mounted on the support beam (1). The reference sliding seat (22) is mounted inside the reference fixing seat (21) and is slidably mounted inside the reference fixing seat (21). The locking pressure plate (3) is mounted on the reference sliding seat (22). When the upper pressure head (5) presses down to bend the sample (7), the bending of the sample (7) causes the reference sliding seat (22) to slide within the reference fixed seat (21), so that the position of the reference sliding seat (22) is adaptively adjusted as the sample (7) bends.

2. The bending fatigue testing fixture according to claim 1, characterized in that, The reference fixing seat (21) includes two first sliding seats (211) and a connecting plate (212). The two first sliding seats (211) are located on both sides of the supporting beam (1). The connecting plate (212) is located between the two first sliding seats (211) and is used to connect the two first sliding seats (211). The reference sliding seat (22) is located between the first sliding seat (211) and the connecting plate (212) and is supported on the supporting beam (1). The first sliding seat (211) is rotatably provided with a first guide wheel (8) facing the reference sliding seat (22). The reference sliding seat (22) is provided with a first groove (9) for the first guide wheel (8) to roll. The first groove (9) is closed at both ends to limit the range of movement of the reference sliding seat (22) within the first sliding seat (211).

3. The bending fatigue testing fixture according to claim 2, characterized in that, Both sides of the supporting crossbeam (1) are provided with T-slots (10). The first sliding seat (211) is provided with a fixing plate facing the supporting crossbeam (1). The fixing plate is located in the T-slot (10). The first sliding seat (211) is threaded with a fixing screw. The fixing plate is rotatably disposed at the end of the fixing screw. The fixing screw drives the fixing plate to abut against the inner wall of the T-slot (10) to fix the first sliding seat (211) on the supporting crossbeam (1).

4. The bending fatigue testing fixture according to claim 3, characterized in that, The top of the supporting beam (1) is provided with a second groove (11), and the bottom of the reference sliding seat (22) is provided with a second guide wheel (12), which is supported by the bottom wall of the second groove (11); the bottom of the connecting plate (212) is provided with a third guide wheel (13), which is pressed against the top of the reference sliding seat (22).

5. The bending fatigue testing fixture according to claim 1, characterized in that, The top of the reference sliding seat (22) is recessed and has an installation groove (14). A receiving roller (15) is rotatably mounted on the reference sliding seat (22) through the installation groove (14). The sample (7) is supported on the receiving roller (15). Both ends of the receiving roller (15) are located outside the installation groove (14). A first mounting plate (16) is fixedly mounted on both sides of the receiving roller (15). The first mounting plate (16) is located outside the installation groove (14). The locking pressure plate (3) is located between the two first mounting plates (16). A strip groove (17) is opened on the first mounting plate (16). The fixing member (4) includes a fixing bolt (41). The fixing bolt (41) passes through the strip groove (17) and is threaded onto the locking pressure plate (3).

6. The bending fatigue testing fixture according to claim 5, characterized in that, The fixing member (4) also includes a pressing screw (42) and a sleeve ring (43). The sleeve ring (43) is located in the strip groove (17) and the fixing bolt (41) passes through the sleeve ring (43). The pressing screw (42) is threaded on the first mounting plate (16) and the sleeve ring (43) is rotatably disposed at the end of the pressing screw (42). The pressing screw (42) drives the sleeve ring (43) to move, which in turn drives the fixing bolt (41) to move, which in turn drives the locking plate (3) to press down the sample (7).

7. A bending fatigue testing fixture according to claim 6, characterized in that, A second mounting plate (18) is provided between the two first mounting plates (16). The second mounting plate (18) is located above the locking plate (3) and there is an installation gap between the second mounting plate (18) and the locking plate (3). A pressing screw (19) is threadedly connected to the middle of the second mounting plate (18). A lower pressure plate (20) is rotatably provided at the end of the pressing screw (19). The lower pressure plate (20) is used to press the middle of the locking plate (3) so that the locking plate (3) is attached to the sample (7).

8. A bending fatigue testing fixture according to claim 5, characterized in that, Both the reference sliding seat (22) and the support beam (1) are equipped with a scale (23), with the zero position of the scale (23) located in the middle and the readings marked on both sides.

9. A bending fatigue testing fixture according to claim 8, characterized in that, Two adjusting plates (24) are provided on the receiving roller (15). The adjusting plates (24) are arc-shaped and their inner rings are attached to the receiving roller (15). The thickness of the adjusting plates (24) is less than the thickness of the sample (7). The adjusting plates (24) are slidably disposed on the receiving roller (15). The adjusting plates (24) slide along the length direction parallel to the receiving roller (15). A driving member is provided on the receiving roller (15). The driving member is used to drive the adjusting plates (24) on both sides to slide and move the sample (7) to the middle of the receiving roller (15) and to clamp the sample (7) laterally.

10. A bending fatigue testing fixture according to claim 9, characterized in that, The driving component includes a bidirectional lead screw (25) rotatably mounted on a reference sliding seat (22), and the outer ring of the adjusting plate (24) is integrally formed with a connecting block, which is threadedly connected to the bidirectional lead screw (25).

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