A SEM in-situ single-lap interface push-shear fatigue testing device and method

Abstract

The application provides a SEM in-situ single-lap interface push-shear fatigue test device and method, and belongs to the technical field of mechanical testing. The device comprises a base, a loading mechanism installed on the base, an outer clamping mechanism for fixing one end of a second material in a single-lap sample, an inner clamping mechanism connected with an output end of the loading mechanism and used for clamping one end of a first material in the single-lap sample, wherein the end of the first material is lap-jointed with the other end of the second material, and a force sensor arranged between the outer clamping mechanism and the base. The loading mechanism, the inner clamping mechanism, the lap-jointed interface of the single-lap sample and the clamping point of the outer clamping mechanism are arranged in line in sequence. The application geometrically eliminates the secondary bending moment of the single-lap sample through a unique push-shear guide structure, and realizes high-stability in-situ fatigue loading by using a motor-piezoelectric series hybrid driving strategy.

Description

Technical Field

[0001] This invention belongs to the field of mechanical testing technology, specifically a SEM in-situ single-overlap interface push-shear fatigue testing device and method. Background Technology

[0002] With the widespread application of high-performance composite materials in aerospace, new energy vehicles, and precision electronics, the design and fabrication of polymer-metal hybrid structures have become crucial for lightweight engineering. In such structures, heterogeneous materials are typically bonded together through adhesive bonding, injection molding, or mechanical interlocking to form an interface. The shear mechanical properties of this interface (such as shear strength and fatigue life) are often the weakest link determining the overall structural safety. To reveal the damage evolution of the interface under load, researchers often use SEM combined with an in-situ mechanical loading stage to observe the initiation and propagation of microcracks at the interface in real time.

[0003] However, existing technologies for in-situ shear fatigue testing of single-lap joint specimens face significant technical bottlenecks in terms of specimen stress state and load application, primarily due to the interference of eccentric bending moment in single-lap tensile testing. Single-lap joint specimens are the most commonly used specimen form for testing interfacial shear performance due to their simple preparation and typical structure (e.g., standard 1STM41002). However, traditional tensile shear loading methods suffer from inherent geometric defects such as non-collinear force lines, secondary bending moments generated at the interface during loading, and stress state distortion. Because the two adhered materials are misaligned in the thickness direction, the line of action of the tensile load cannot pass through the geometric center of the interface. Under tensile load, this eccentricity generates an additional bending moment, causing the specimen to warp. This bending moment introduces significant peel stress at the interface ends. This peel effect is particularly severe for polymer-metal interfaces with significant stiffness differences, often leading to tearing failure due to peel stress before reaching the true shear limit. Existing tensile methods measure failure data in a mixed tension-shear mode, which cannot accurately characterize the pure shear fatigue performance of the interface. Summary of the Invention

[0004] To address the shortcomings of the prior art, the technical problem to be solved by the embodiments of the present invention is to provide a SEM in-situ single-overlap interface push-shear fatigue testing device and method.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A SEM in-situ single-overlap interface push-shear fatigue testing device includes:

[0007] Base;

[0008] A loading mechanism for providing driving force along a single axis, the loading mechanism being mounted on the base;

[0009] An external clamping mechanism is used to fix one end of the second material in a single-lapped specimen.

[0010] The inner clamping mechanism is connected to the output end of the loading mechanism and is used to clamp one end of the first material in the single-overlap sample. This end of the first material overlaps with the other end of the second material. The clamping forces of the outer clamping mechanism and the inner clamping mechanism are perpendicular to the sides of the second material and the first material, respectively.

[0011] A force sensor is disposed between the external clamping mechanism and the base to detect the shear force on the lap joint interface of the single lap joint sample.

[0012] The loading mechanism, the inner clamping mechanism, the lap joint interface of the single lap joint sample, and the clamping points of the outer clamping mechanism are arranged collinearly in sequence.

[0013] As a further improvement: the loading mechanism includes a drive component mounted on the base for generating axial driving force;

[0014] It also includes a flexible hinge and a piezoelectric stack disposed within the flexible hinge, one end of which is connected to the output end of the drive component and the other end of which is connected to the inner clamping mechanism.

[0015] As a further improvement: the axis of the piezoelectric stack is arranged parallel to the axis of the drive component.

[0016] As a further improvement: The external clamping mechanism includes an external fixed base, an inner sliding block, and a fixed block. The end of the external fixed base away from the force sensor has a slot. The inner sliding block is slidably disposed in the slot. The fixed block is fixed in the slot and disposed opposite to the inner sliding block. One end of the second material is clamped between the inner sliding block and the fixed block. The end of the inner sliding block away from the fixed block is provided with a first fastener.

[0017] As a further improvement: The first fastener includes an adjusting bolt, which passes through the outer fixing seat and is threadedly connected to the outer fixing seat, and the end of the adjusting bolt abuts against the abutting surface of the inner sliding block.

[0018] As a further improvement: the inner clamping mechanism includes a clamping seat and a movable clamping block, the movable clamping block being connected to the clamping seat via a second fastener, and the first material being located between the clamping seat and the movable clamping block.

[0019] As a further improvement: the overlap interface of the single-lapped specimen has no obstruction structure directly above it.

[0020] This invention also provides a method for in-situ SEM single-overlap interface push-shear fatigue testing, the method comprising the following steps:

[0021] The first material of the single-lapped specimen is clamped and fixed by an inner clamping mechanism, and the second material of the single-lapped specimen is clamped and fixed by an outer clamping mechanism, so that the lap interface of the single-lapped specimen is exposed and unobstructed from above; the entire testing device is placed in the sample chamber of a scanning electron microscope; the inner clamping mechanism is driven to move along the lap interface direction by a loading mechanism to apply a push-shear load to the lap interface of the single-lapped specimen; under the action of the push-shear load, the shear force on the lap interface is monitored by the force sensor, and the microscopic morphology damage evolution process of the lap interface is observed in situ using a scanning electron microscope.

[0022] As a further improvement: The step of driving the inner clamping mechanism through the loading mechanism includes: applying a quasi-static pre-shear load to the single lapped specimen through the driving component of the loading mechanism; and, while maintaining the pre-shear load, performing fatigue testing by superimposing a high-frequency alternating shear load on the single lapped specimen through a piezoelectric stack.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention eliminates the secondary bending moment of the single-lapped specimen geometrically through a unique push-shear guiding structure, constructs an approximately pure shear stress field, and realizes highly stable in-situ fatigue loading by using a motor-piezoelectric series hybrid drive strategy, thereby realizing real-time in-situ observation of the pure shear fatigue performance test and micro-damage evolution mode of the single-lapped interface in a SEM vacuum environment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0025] Figure 2 A three-dimensional view of the loading mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0026] Figure 3 A top view of the loading mechanism of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0027] Figure 4 A schematic diagram of the base structure of a SEM in-situ single-overlap interface push-shear fatigue testing device.

[0028] Figure 5 A schematic diagram of the slide rail structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0029] Figure 6This is a schematic diagram of the screw fixing seat structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0030] Figure 7 A schematic diagram of the motor mounting base structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0031] Figure 8 This is a schematic diagram of the sliding seat, lead screw nut and lead screw connection of a SEM in-situ single lap joint interface push-shear fatigue testing device.

[0032] Figure 9 A schematic diagram of the sliding seat structure of an in-situ SEM single-overlap interface push-shear fatigue testing device.

[0033] Figure 10 A schematic diagram of the lead screw structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0034] Figure 11 A schematic diagram of the screw and nut structure of an in-situ SEM single-lap joint interface push-shear fatigue testing device.

[0035] Figure 12 A schematic diagram of the motor structure of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0036] Figure 13 A schematic diagram of a flexible hinge structure for an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0037] Figure 14 A perspective view of the external clamping mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0038] Figure 15 A side view of the external clamping mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0039] Figure 16 This is a schematic diagram of the external fixing base structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0040] Figure 17 This is a schematic diagram of the external sliding block structure of an in-situ SEM single-overlap interface push-shear fatigue testing device.

[0041] Figure 18 This is a schematic diagram of the inner sliding block structure of an in-situ SEM single-overlap interface push-shear fatigue testing device.

[0042] Figure 19 This is a schematic diagram of a single-lapped specimen structure of an in-situ SEM single-lapped interface push-shear fatigue testing device.

[0043] Figure 20A top view of the external clamping mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0044] Figure 21 A schematic diagram of the mounting frame structure of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0045] Figure 22 This is a schematic diagram of the force sensor structure of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0046] Figure 23 A three-dimensional view of the connection between the internal clamping mechanism and the flexible hinge of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0047] Figure 24 A top view of the internal clamping mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0048] Figure 25 This is a schematic diagram of the internal clamping mechanism and flexible hinge structure of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0049] Figure 26 A top view of a flexible hinge in an in-situ SEM single-overlap interface push-shear fatigue testing device.

[0050] Figure 27 A three-dimensional view of the internal clamping mechanism of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0051] Figure 28 This is a schematic diagram of the movable clamping block structure of an in-situ SEM single-overlap interface push-shear fatigue testing device.

[0052] Figure 29 A three-dimensional view of the clamping seat of an in-situ single-overlap interface push-shear fatigue testing device for SEM.

[0053] Figure 30 A top view of the clamping seat of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0054] Figure 31 A bottom view of the clamping seat of an in-situ single-lap joint interface push-shear fatigue testing device for SEM.

[0055] In the diagram: 1. Loading mechanism; 11. Fifth bolt; 12. Slide rail; 121. Countersunk cylindrical hole; 13. Lead screw; 14. First bolt; 15. Second bolt; 16. Sliding seat; 161. First through hole; 162. Second through hole; 163. Sixth threaded hole; 17. Lead screw fixing seat; 171. Third through hole; 172. Fourth through hole; 173. Through hole; 18. Third bolt; 19. Motor fixing seat; 191. Fifth through hole; 192. 193. Six-way hole; 110. Seventh threaded hole; 111. Fourth bolt; 111. Motor; 1111. Seventh through hole; 112. Screw nut; 1121. Eighth through hole; 1122. Eighth threaded hole; 113. Coupling; 114. Seventh bolt; 115. Flexible hinge; 1151. Ninth through hole; 1152. Tenth through hole; 116. Piezoelectric stack; 2. External clamping mechanism; 21. External fixed base; 211. Ninth threaded hole; 212. Plain hole; 213. Slide rail; 214. Groove; 22. Sixth bolt; 23. Outer sliding block; 231. Eleventh through hole; 24. Inner sliding block; 241. Tenth threaded hole; 242. Abutment surface; 25. Fixing block; 26. Adjusting bolt; 27. Anti-loosening nut; 28. Ninth bolt; 29. ​​Mounting bracket; 291. Eleventh threaded hole; 292. Twelfth through hole; 3. Inner clamping mechanism; 31. Clamping seat; 311. Twelfth threaded hole; 312. Thirteenth... Threaded hole; 313, clamping surface; 32, movable clamping block; 321, thirteenth through hole; 33, tenth bolt; 34, eighth bolt; 4, force sensor; 41, first stud; 42, second stud; 5, single lap joint sample; 51, first material; 52, second material; 10, base; 101, base plate; 1011, first threaded hole; 1012, second threaded hole; 1013, third threaded hole; 102, side plate; 1020, fifth threaded hole. Detailed Implementation

[0056] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0057] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0058] Please see Figures 1 to 31 In one embodiment, a SEM in-situ single-overlap interface push-shear fatigue testing device includes:

[0059] Base 10;

[0060] A loading mechanism 1 is used to provide a driving force along a single axis, and the loading mechanism 1 is mounted on the base 10;

[0061] External clamping mechanism 2 is used to fix one end of the second material 52 in the single lap joint sample 5;

[0062] The inner clamping mechanism 3 is connected to the output end of the loading mechanism 1 and is used to clamp one end of the first material 51 in the single overlapping sample 5. This end of the first material 51 overlaps with the other end of the second material 52. The clamping forces of the outer clamping mechanism 2 and the inner clamping mechanism 3 are perpendicular to the sides of the second material 52 and the first material 51, respectively.

[0063] Force sensor 4 is disposed between the outer clamping mechanism 2 and the base 10 to detect the shear force on the lap interface of the single lapped sample 5.

[0064] The loading mechanism 1, the inner clamping mechanism 3, the overlapping interface of the single overlapping sample 5, and the clamping point of the outer clamping mechanism 2 are arranged collinearly in sequence.

[0065] In this embodiment, the overlapping interface is a heterogeneous interface. The loading mechanism 1 drives the inner clamping mechanism 3 to move away from the outer clamping mechanism 2, thereby moving axially in the direction of the force sensor 4. Since the first material 51 is limited by the inner clamping mechanism 3, it is ultimately pushed to move in the direction of the force sensor 4. Since the outer end of the second material 52 is clamped and fixed by the outer clamping mechanism 2, the first material 51 and the second material 52 generate axial shear force at the overlapping interface, but cannot generate eccentric bending moment. At this time, the shear force generated at the overlapping interface of the first material 51 and the second material 52 in the push-shear state is a quasi-static load. The force measured by the force sensor 4 at this time is the shear force on the overlapping interface of the second material 52 and the first material 51 in the push-shear state.

[0066] Please see Figures 1 to 13 In a preferred embodiment of the present invention, the loading mechanism 1 includes a driving component, which is mounted on the base 10 and is used to generate axial driving force.

[0067] It also includes a flexible hinge 115 and a piezoelectric stack 116 disposed within the flexible hinge 115. One end of the flexible hinge 115 is connected to the output end of the drive assembly, and the other end is connected to the inner clamping mechanism 3.

[0068] In this embodiment, the drive assembly consists of a slide rail 12, a lead screw 13, a sliding seat 16, a lead screw fixing seat 17, a motor fixing seat 19, a motor 111, a lead screw nut 112, and a coupling 113.

[0069] The base 10 includes a base plate 101 and a side plate 102. The base plate 101 of the base 10 has a first threaded hole 1011, a second threaded hole 1012, and a third threaded hole 1013. The slide rail 12 has a cylindrical countersunk hole 121. A first bolt 14 passes through the cylindrical countersunk hole 121 and connects to the first threaded hole 1011. The slide rail 12 is connected and fixed to the base plate 101 of the base 10 by the first bolt 14. The lead screw fixing seat 17 has a third through hole 171 and a fourth through hole 172. A third bolt 18 passes through the third through hole 171 and connects to the second threaded hole 1012. The lead screw fixing seat 17 is connected and fixed to the base plate 101 of the base 10 by the third bolt 18. The through hole 173 of the seat 17 contacts the lead screw 13 to fix the lead screw 13. The motor mounting seat 19 is provided with a fifth through hole 191, a sixth through hole 192 and a seventh threaded hole 193. The fourth bolt 110 passes through the fifth through hole 191 and is connected to the third threaded hole 1013. The motor mounting seat 19 is connected and fixed to the base plate 101 of the base 10 by the fourth bolt 110. The sixth through hole 192 is used to pass through the lead screw 13. The diameter of the sixth through hole 192 is larger than the major diameter of the lead screw 13. The motor 111 is provided with a seventh through hole 1111. The seventh bolt 114 passes through the seventh through hole 1111 and is connected to the seventh threaded hole 193. The motor 111 is connected and fixed to the motor mounting seat 19 by the seventh bolt 114.

[0070] The sliding seat 16 has a first through hole 161, a second through hole 162, and a sixth threaded hole 163. The lead screw nut 112 has an eighth through hole 1121 and an eighth threaded hole 1122. The second bolt 15 passes through the first through hole 161 and is connected to the eighth through hole 1121. The sliding seat 16 is connected and fixed to the lead screw nut 112 by the second bolt 15. The second through hole 162 is used for the lead screw 13 to pass through, and the diameter of the second through hole 162 is larger than the major diameter of the lead screw 13. The lead screw 13 is connected to the eighth threaded hole 1122 of the lead screw nut 112. The lead screw 13 is connected to one end of the coupling 113, and the motor 111 outputs power to the coupling 113. The output shaft is connected to the other end of the coupling 113. The flexible hinge 115 is provided with a ninth through hole 1151 and a tenth through hole 1152. The fifth bolt 11 passes through the ninth through hole 1151 and is connected to the sixth threaded hole 163. The flexible hinge 115 is connected and fixed to the sliding seat 16 by the fifth bolt 11. The piezoelectric stack 116 is placed in the slot of the flexible hinge 115. The slot of the flexible hinge 115 and the two end faces of the piezoelectric stack 116 form a tight fit. The flexible hinge 115 applies a preload to the piezoelectric stack 116. The axis of the piezoelectric stack 116 is parallel to the axis of the lead screw 13.

[0071] Please see Figures 14 to 22In a preferred embodiment of the present invention, the external clamping mechanism 2 includes an external fixing base 21, an inner sliding block 24, and a fixing block 25. The outer fixing base 21 has a slot 214 at one end away from the force sensor 4. The inner sliding block 24 is slidably disposed in the slot 214. The fixing block 25 is fixed in the slot 214 and disposed opposite to the inner sliding block 24. One end of the second material 52 is clamped between the inner sliding block 24 and the fixing block 25. A first fastener is provided at one end of the inner sliding block 24 away from the fixing block 25.

[0072] In this embodiment, the outer fixing base 21 is provided with a light hole 212. The force sensor 4 is provided with a first stud 41 and a second stud 42 at both ends. The first stud 41 passes through the light hole 212 and is connected to the anti-loosening nut 27. The outer fixing base 21 is connected and fixed to the force sensor 4 through the anti-loosening nut 27. The side plate 102 of the base 10 is provided with a fifth threaded hole 1020. The mounting bracket 29 is provided with an eleventh threaded hole 291 and a twelfth through hole 292. The ninth bolt 28 passes through the twelfth through hole 292 and is connected to the fifth threaded hole 1020. The mounting bracket 29 is connected and fixed to the side plate 102 through the ninth bolt 28. The second stud 42 is connected to the eleventh threaded hole 291 of the mounting bracket 29, thereby connecting and fixing the force sensor 4 to the mounting bracket 29. The fixing block 25 is placed at the slot 214 of the outer fixing base 21. The second material 52 is placed between the inner sliding block 24 and the fixing block 25.

[0073] The inner sliding block 24 is pushed closer to the fixed block 25 by the first fastener, so that the second material 52 is clamped between the inner sliding block 24 and the fixed block 25.

[0074] Please see Figures 14 to 22 In a preferred embodiment of the present invention, the first fastener includes an adjusting bolt 26, which passes through the outer fixing seat 21 and is threadedly connected to the outer fixing seat 21, and the end of the adjusting bolt 26 abuts against the abutment surface 242 of the inner sliding block 24.

[0075] In this embodiment, the outer fixed base 21 is provided with a ninth threaded hole 211, the outer sliding block 23 is provided with an eleventh through hole 231, and the inner sliding block 24 is provided with a tenth threaded hole 241. The inner sliding block 24 and the outer sliding block 23 are respectively placed on the inner and outer sides of the slide 213 of the outer fixed base 21. The sixth bolt 22 passes through the eleventh through hole 231 and is connected to the tenth threaded hole 241. The inner sliding block 24 is connected to the outer sliding block 23 through the sixth bolt 22 and can slide along the slide 213. The adjusting bolt 26 is connected to the ninth threaded hole 211 of the outer fixed base 21. The bottom of the adjusting bolt 26 rests on the abutment surface 242 of the inner sliding block 24. The abutment surface 242 of the inner sliding block 24 is knurled to prevent the bottom of the adjusting bolt 26 from slipping on the abutment surface 242. By tightening the adjusting bolt 26, the inner sliding block 24 can be moved towards the fixed block 25, thereby clamping and fixing the outer end of the second material 52 by the inner sliding block 24 and the fixed block 25.

[0076] Please see Figures 23 to 31 In a preferred embodiment of the present invention, the inner clamping mechanism 3 includes a clamping seat 31 and a movable clamping block 32. The movable clamping block 32 is connected to the clamping seat 31 by a second fastener, and the first material 51 is located between the clamping seat 31 and the movable clamping block 32.

[0077] In this embodiment, the second fastener includes a tenth bolt 33, a clamping seat 31 is provided with a twelfth threaded hole 311 and a thirteenth threaded hole 312, and a movable clamping block 32 is provided with a thirteenth through hole 321. The tenth bolt 33 passes through the thirteenth through hole 321 and is connected to the twelfth threaded hole 311. The first material 51 is placed on the clamping surface 313 of the clamping seat 31. By tightening the tenth bolt 33, the inner end of the first material 51 can be clamped by the clamping seat 31 and the movable clamping block 32. At the same time, the first material 51 can also be fixed at the clamping surface 313 of the clamping seat 31. The tenth bolt 33, the clamping seat 31 and the movable clamping block 32 should not be directly above the lap interface of the single lapped sample 5. The eighth bolt 34 is connected to the thirteenth threaded hole 312 through the tenth through hole 1152 of the flexible hinge 115. The clamping seat 31 is connected and fixed to the flexible hinge 115 through the eighth bolt 34.

[0078] Please see Figures 1 to 31 In a preferred embodiment of the present invention, there is no obstruction structure directly above the lap joint interface of the single lap joint sample 5.

[0079] In this embodiment, the single-lapped sample 5 is clamped by the inner clamping mechanism 3 and the outer clamping mechanism 2. At this time, the lapped interface of the single-lapped sample 5 is exposed and unobstructed, which facilitates in-situ observation by the SEM observation lens.

[0080] The working process of the SEM in-situ single-overlap interface push-shear fatigue testing device is as follows:

[0081] The output shaft of motor 111 begins to rotate, outputting torque and speed. Coupling 113 transmits the torque output from the motor 111 to lead screw 13, causing lead screw 13 to rotate. Lead screw nut 112 is connected and fixed to sliding seat 16 by second bolt 15. Sliding seat 16 is restricted by slide rail 12, preventing it from rotating. Under the axial thrust generated by lead screw 13, and because its rotational freedom is restricted, lead screw nut 112 moves linearly along the axial direction of lead screw 13, thereby causing sliding seat 16 to move along the axial direction of lead screw 13 in the direction of force sensor 4. Since the sliding seat 16 is fixedly connected to the flexible hinge 115 by the fifth bolt 11, and the clamping seat 31 is also fixedly connected to the flexible hinge 115 by the eighth bolt 34, the clamping seat 31 moves axially along the lead screw 13 in the direction of the force sensor 4. Since the first material 51 is fixed at the clamping surface 313 of the clamping seat 31, the first material 51 is limited by the clamping seat 31, thereby ultimately pushing the clamped first material 51 to move axially along the lead screw 13 in the direction of the force sensor 4. Since the outer end of the second material 52 is blocked by the inner sliding block... 24 and the fixing block 25 clamp and fix. The inner end of the first material 51 is limited by the clamping seat 31 and the movable clamping block 32. The first material 51 is limited by the clamping seat 31, so that the first material 51 and the second material 52 generate axial shear force at the overlapping interface, and cannot generate eccentric bending moment. At this time, the shear force generated at the overlapping interface of the first material 51 and the second material 52 in the push-shear state is a quasi-static load. The force measured by the force sensor 4 at this time is the shear force on the overlapping interface of the second material 52 and the first material 51 in the push-shear state.

[0082] This invention also provides a method for in-situ SEM single-overlap interface push-shear fatigue testing, the method comprising the following steps:

[0083] The first material 51 of the single lapped sample 5 is clamped and fixed by the inner clamping mechanism 3, and the second material 52 of the single lapped sample 5 is clamped and fixed by the outer clamping mechanism 2, so that the lapped interface of the single lapped sample 5 is exposed and unobstructed from above.

[0084] The entire testing device was placed inside the sample chamber of a scanning electron microscope (SEM) to observe the damage evolution process of the lap joint interface of the single lap joint sample 5.

[0085] The loading mechanism 1 drives the inner clamping mechanism 3 to move along the lap joint direction, thereby applying a push-shear load to the lap joint interface of the single lap joint sample 5.

[0086] Under the action of shear load, the force sensor 4 is used to monitor the shear force on the overlapping interface, and at the same time, the microscopic morphology damage evolution process of the overlapping interface is observed in situ using a scanning electron microscope.

[0087] As a preferred embodiment of the present invention, the step of driving the inner clamping mechanism 3 by the loading mechanism 1 includes: applying a quasi-static pre-shear load to the single lap joint specimen 5 by the driving component of the loading mechanism 1.

[0088] While maintaining the pre-shear load, fatigue testing is performed on the single-lapped specimen 5 by superimposing a high-frequency alternating shear load through the piezoelectric stack 116.

[0089] In this embodiment, after the quasi-static load on the single-lapped sample is applied and held, a voltage is then applied to both ends of the piezoelectric stack 116. Utilizing its inverse piezoelectric effect, the piezoelectric stack 116 generates displacement. This displacement exists only in the axial direction of the piezoelectric stack 116, which drives the clamping seat 31 to move through the flexible hinge 115. This causes the first material 51 to be pushed axially in the direction of the force sensor 4. The piezoelectric stack 116 is parallel to the axis of the lead screw 13, causing the shear force generated at the lap interface between the first material 51 and the second material 52 to become an alternating load. At this time, the shear force generated at the lap interface between the first material 51 and the second material 52 under the push-shear state is still axial and does not generate an eccentric bending moment. The force measured by the force sensor 4 at this time is the shear force on the lap interface between the second material 52 and the first material 51.

[0090] This invention designs a push-shear type guiding and limiting structure to force the loading force line through the geometric center of the interface, physically eliminating secondary bending moments and peeling stress at the interface ends, thereby achieving pure shear loading on a single lap joint interface. This ensures the acquisition of accurate and reliable interface shear fatigue performance data, and enables real-time in-situ observation of the pure shear fatigue performance test and micro-damage evolution mode of a single lap joint interface in a SEM vacuum environment.

[0091] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0092] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A SEM in-situ single-overlap interface push-shear fatigue testing device, characterized in that, include: Base; A loading mechanism for providing driving force along a single axis, the loading mechanism being mounted on the base; An external clamping mechanism is used to fix one end of the second material in a single-lapped specimen. The inner clamping mechanism is connected to the output end of the loading mechanism and is used to clamp one end of the first material in the single-overlap sample. This end of the first material overlaps with the other end of the second material. The clamping forces of the outer clamping mechanism and the inner clamping mechanism are perpendicular to the sides of the second material and the first material, respectively. A force sensor is disposed between the external clamping mechanism and the base to detect the shear force on the lap joint interface of the single lap joint sample. The loading mechanism, the inner clamping mechanism, the overlap interface of the single overlap sample, and the clamping points of the outer clamping mechanism are arranged collinearly in sequence. The loading mechanism includes a drive component mounted on the base for generating axial driving force; It also includes a flexible hinge and a piezoelectric stack disposed within the flexible hinge, one end of the flexible hinge being connected to the output end of the drive component and the other end being connected to the inner clamping mechanism; The external clamping mechanism includes an external fixed base, an inner sliding block, and a fixed block. The external fixed base has a slot at the end away from the force sensor. The inner sliding block is slidably disposed in the slot. The fixed block is fixed in the slot and disposed opposite to the inner sliding block. One end of the second material is clamped between the inner sliding block and the fixed block. A first fastener is provided at the end of the inner sliding block away from the fixed block. The internal clamping mechanism includes a clamping seat and a movable clamping block. The movable clamping block is connected to the clamping seat via a second fastener. The first material is located between the clamping seat and the movable clamping block, and the first material is limited by the clamping seat. The single-lapped specimen has no obstruction structure directly above the lap joint interface.

2. The SEM in-situ single-overlap interface push-shear fatigue testing device according to claim 1, characterized in that, The axis of the piezoelectric stack is arranged parallel to the axis of the drive assembly.

3. The SEM in-situ single-overlap interface push-shear fatigue testing device according to claim 1, characterized in that, The first fastener includes an adjusting bolt, which passes through the outer fixing seat and is threadedly connected to the outer fixing seat, and the end of the adjusting bolt abuts against the abutting surface of the inner sliding block.

4. A method for in-situ SEM single-overlap interface push-shear fatigue testing, said method being implemented based on the SEM in-situ single-overlap interface push-shear fatigue testing device according to any one of claims 1-3, characterized in that, The method includes the following steps: The first material of the single lapped specimen is clamped and fixed by the inner clamping mechanism, and the second material of the single lapped specimen is clamped and fixed by the outer clamping mechanism, so that the lap interface of the single lapped specimen is exposed and unobstructed from above. The entire testing setup was placed inside the sample chamber of the scanning electron microscope; The loading mechanism drives the inner clamping mechanism to move along the lap joint direction, applying a push-shear load to the lap joint interface of the single lap joint specimen. Under the action of shear load, the force sensor is used to monitor the shear force on the overlapping interface, and at the same time, the microscopic morphology damage evolution process of the overlapping interface is observed in situ using a scanning electron microscope.

5. The SEM in-situ single-overlap interface push-shear fatigue test method according to claim 4, characterized in that, The step of driving the inner clamping mechanism through the loading mechanism includes: A quasi-static pre-shear load is applied to the single lap joint specimen by the drive component of the loading mechanism. While maintaining the pre-shear load, fatigue testing is performed on the single-lapped specimen by superimposing a high-frequency alternating shear load through piezoelectric stacking.

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