Actuator and pressure loading method

Abstract

The invention discloses an actuator and a pressure loading method, and belongs to the technical field of geotechnical engineering test equipment.The actuator comprises a fixed plate, a movable plate and an air bag, the fixed plate is used for being connected to a test device, and the fixed plate is provided with a first groove; the movable plate is used for abutting against a test sample, a second groove is formed in the movable plate, an opening of the first groove is opposite to an opening of the second groove to form a containing cavity, and a distance is formed between the top end of the first groove and the top end of the second groove; the air bag is installed in the containing cavity, and the air bag is inflated to push the movable plate to move relative to the fixed plate. According to the invention, the air bag is adopted for loading the test sample, and due to the flexible characteristic and very small natural vibration frequency of the air bag, the frequency adaptability of the actuator and the test sample in the vibration test process is ensured, and the influence on test data caused by mismatching of frequency characteristics is avoided.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing equipment technology, and in particular to an actuator and a pressure loading method. Background Technology

[0002] In the field of geotechnical engineering testing, actuators, as core devices that convert energy into mechanical motion, are mainly used to apply control forces to test samples or to test their dynamic characteristics. Traditional shaking table tests typically use jacks as actuators to simulate ground stress and external loads, but this approach has significant technical limitations:

[0003] First, there are inherent defects in dynamic characteristic matching. Traditional jacks are made of rigid metal materials, and their inherent frequency characteristics differ significantly from those of the test samples (mostly rock-like or rock-like materials). During vibration testing, this frequency mismatch causes the actuator's own vibration characteristics to interfere with the test data in a significant way, seriously affecting the accuracy of the test results.

[0004] Secondly, there are technical bottlenecks in terms of structural load-bearing capacity. Since the jacks are mainly made of high-density steel, their own weight is too large. This not only increases the overall mass of the loading system, but also exceeds the design load-bearing capacity of most existing shaking table test devices, which seriously restricts the applicability of the test system.

[0005] Secondly, there are significant shortcomings in terms of economic efficiency. The high manufacturing cost of traditional jacks leads to a high cost for the entire loading device, which to some extent limits the widespread application of this technology in scientific research and engineering practice.

[0006] Therefore, there is an urgent need to develop a new type of actuator to solve the technical problems of dynamic characteristic interference, structural load-bearing limitations, and insufficient economy of traditional jacks in shaking table tests. Summary of the Invention

[0007] The purpose of this invention is to provide an actuator and a pressure loading method to solve the problems existing in the prior art. An airbag is used for loading the test sample. Due to the flexibility of the airbag, its natural frequency is very small, which ensures the frequency adaptability between the actuator and the test sample during the vibration test and avoids the influence of frequency mismatch on the test data.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] This invention provides an actuator, including a fixed plate, a movable plate, and an airbag. The fixed plate is used to connect to a testing device and has a first groove. The movable plate is used to abut against a test sample and has a second groove. The openings of the first groove and the second groove are opposite to each other to form a receiving cavity. The top ends of the first groove and the top ends of the second groove are spaced apart. The airbag is installed in the receiving cavity, and inflation of the airbag is used to push the movable plate to move relative to the fixed plate.

[0010] In one embodiment, the first groove is formed by a first circumferential wall, the cross-section of the first circumferential wall along the loading direction is triangular, and the cross-section of the first groove gradually increases from the inner bottom of the first groove towards the opening direction of the first groove; the second groove is formed by a second circumferential wall, the cross-section of the second circumferential wall along the loading direction is triangular, and the cross-section of the second groove gradually increases from the inner bottom of the second groove towards the opening direction of the second groove.

[0011] In one embodiment, the airbag includes an inner rubber bladder and an outer polyurethane cover. The polyurethane cover has a rectangular design, and there is a gap between the sidewall of the polyurethane cover and the apex of the triangle. The gap is used to accommodate the lateral deformation of the airbag during the loading of the airbag.

[0012] In one embodiment, a return spring is also included. The first end of the return spring is connected to the inner wall of the rubber bladder near the fixed plate, and the second end of the return spring is connected to the inner wall of the rubber bladder near the movable plate. The two ends of the return spring are connected to the rubber bladder via rubber pads. When the air bladder is not inflated, the return spring is in a natural state. When the air bladder is inflated, the return spring is stretched.

[0013] In one embodiment, a guide rod is further included, which is used to guide the loading direction of the movable plate. At least two guide rods are evenly distributed along the outer periphery of the receiving cavity, and the two ends of the guide rods are respectively connected to the fixed plate and the movable plate.

[0014] In one embodiment, the guide rod includes a sleeve and a slide rod, the slide rod being slidably disposed within the sleeve; the sleeve is connected to the fixed plate and the slide rod is connected to the movable plate, or the sleeve is connected to the movable plate and the slide rod is connected to the fixed plate.

[0015] In one embodiment, the system further includes a strain gauge and a pressure gauge, the strain gauge being disposed on the inner wall of the airbag and the pressure gauge being connected to the inner cavity of the airbag.

[0016] In one embodiment, a displacement sensor is also included, which is mounted on the fixed plate and has its probe abutting against the movable plate.

[0017] In one embodiment, the airbag is provided with a vent hole, and the vent hole is provided with a one-way air intake valve.

[0018] The present invention also provides a pressure loading method, using an actuator as described above, comprising the following:

[0019] S1. Install the fixed plate on the test device, with the movable plate facing the test sample;

[0020] S2. Inflate the airbag, and the airbag expands after inflation, pushing the movable plate to squeeze the test sample;

[0021] S3. Utilize the flexibility of the airbag to improve its adaptability to the vibration frequency of the test sample;

[0022] S4. After the pressure loading is completed, the gas inside the airbag is released to relieve the pressure of the movable plate on the test sample.

[0023] The present invention achieves the following technical effects compared to the prior art:

[0024] This invention confines the airbag between a fixed plate and a movable plate, and uses a first groove and a second groove to form a cavity for receiving the airbag. After the airbag is inflated, the movable plate can be used to apply pressure to the test sample. Due to the flexibility of the airbag, the natural frequency of the airbag is very small during the vibration test, which can improve the frequency adaptability between the actuator and the test sample, avoid the influence of frequency mismatch on the test data, and expand the applicability of the actuator.

[0025] This invention uses an airbag loading method, which makes the loading more durable and stable. Compared with the traditional jack airbag, it has a smaller mass, which can minimize the weight of the actuator and reduce the space and weight occupied by the actuator, especially in situations where weight requirements are strict, such as vibration table tests.

[0026] Other technical solutions included in this invention can also achieve the following technical effects:

[0027] This invention not only includes a pressure gauge to monitor the inflation pressure of the airbag in real time and ensure the accuracy of loading, but also a strain gauge to monitor the stress changes of the airbag in real time. This allows for early warning of the airbag's extreme state, preventing airbag bursting accidents, and also provides the strain force change pattern during the airbag inflation and deflation process, providing calibration and reference for the pressure gauge readings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the overall structure of the actuator in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the device after removing the movable plate in an embodiment of the present invention;

[0031] Figure 3 This is a top view of the actuator in an embodiment of the present invention;

[0032] Figure 4 This is a side view of the actuator in an embodiment of the present invention;

[0033] Figure 5 This is a three-dimensional vertical sectional view in an embodiment of the present invention;

[0034] Figure 6 This is a three-dimensional horizontal cross-sectional view in an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of the fixing plate in an embodiment of the present invention;

[0036] Figure 8 This is a stress analysis diagram of the airbag under maximum load in an embodiment of the present invention;

[0037] Among them, 1. Polyurethane cover; 2. Rubber bladder; 3. Strain gauge; 4. Reset spring; 5. Movable plate; 6. Displacement sensor; 7. Guide rod; 8. Fixing plate; 9. Vent hole; 10. Wire hole; 11. Pressure gauge; 12. Rubber pad; 13. High-strength bolt; 14. First circumferential wall. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The purpose of this invention is to provide an actuator and a pressure loading method to solve the problems existing in the prior art. An airbag is used for loading the test sample. Due to the flexibility of the airbag, its natural frequency is very small, which ensures the frequency adaptability between the actuator and the test sample during the vibration test and avoids the influence of frequency mismatch on the test data.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figures 1 to 7 As shown, the present invention provides an actuator including a fixed plate 8, a movable plate 5, and an airbag. The fixed plate 8 is connected to a testing device to provide support. The fixed plate 8 has a first groove extending toward the movable plate 5. The movable plate 5 is used to directly abut against the test sample or abut against the test sample via a loading plate to provide test pressure to the test sample. The movable plate 5 has a second groove extending toward the fixed plate 8. The openings of the first and second grooves are opposite each other to form a receiving cavity. The top ends of the first and second grooves are spaced apart. Before and after the airbag is inflated, the first and second grooves do not contact each other, so as to form a through space for air supply paths, wiring, etc., between the first and second grooves. The airbag is installed in the receiving cavity. By inflating the airbag, the movable plate 5 can be pushed relative to the fixed plate 8 to produce a displacement away from the fixed plate 8, thereby allowing the movable plate 5 to compress the test sample.

[0042] This invention confines the airbag between the fixed plate 8 and the movable plate 5, and utilizes the first and second grooves to form a cavity for receiving the airbag. After the airbag is inflated, the movable plate 5 can apply pressure to the test sample. Due to the flexibility of the airbag, its natural frequency is very small during vibration testing, which improves the frequency adaptability between the actuator and the test sample, avoids the influence of frequency mismatch on the test data, and expands the applicability range of the actuator. In addition, the airbag loading method of this invention makes the loading more durable and stable, and its mass is smaller than that of traditional jack airbags, which can minimize the weight of the actuator and reduce the space and weight occupied by the actuator, especially in applications with strict weight requirements such as vibration table tests.

[0043] In one embodiment, the dimensions of the fixed plate 8 and the movable plate 5 are 800mm×800mm×10mm (length×width×thickness), and 11 bolt holes are reserved (the number of bolt holes distributed on the four sides are 3, 3, 3 and 2 respectively). During the loading process, the high-strength bolts 13 are used to fix the fixed plate 8 and the loading frame of the test device together through the reserved bolt holes.

[0044] In one implementation, such as Figure 5 and Figure 7 As shown, the first groove is formed by the first circumferential wall 14. The cross-section of the first circumferential wall 14 along the loading direction is triangular. Therefore, the cross-sectional area of ​​the first groove varies from bottom to top. Specifically, the cross-section of the first groove gradually increases from the inner bottom surface of the first groove to the opening direction of the first groove. After the airbag is installed, the bottom surface of the airbag contacts the inner bottom surface of the first groove. There is a V-shaped gap between the side wall of the airbag and the inner wall of the first groove. That is, the gap is larger closer to the top of the first circumferential wall 14. When the airbag inflates, the first groove can constrain the radial expansion of the airbag. In the area near the top of the first groove, there is also an appropriate area to accommodate the possible deformation of the airbag. Therefore, when the airbag is used to push the movable plate 5 to move, the friction between the inner wall of the first groove and the outer wall of the airbag can be reduced, the stability of the airbag operation can be improved, and the service life can be guaranteed.

[0045] The second groove is formed by a second annular wall, which is set with reference to the first annular wall 14. The cross-section of the second annular wall along the loading direction is triangular. The cross-sectional area of ​​the second groove varies from bottom to top. Specifically, the cross-section of the second groove gradually increases from the inner bottom surface of the second groove to the opening direction of the second groove. After the airbag is installed, the bottom surface of the airbag contacts the inner bottom surface of the second groove. There is a V-shaped gap between the side wall of the airbag and the inner wall of the second groove. That is, the gap is larger closer to the top of the second annular wall. When the airbag inflates, the second groove can constrain the radial expansion of the airbag. In the area near the top of the second groove, there is also an appropriate area to accommodate the possible deformation of the airbag. Therefore, when the airbag is used to push the movable plate 5 to move, the friction between the inner wall of the second groove and the outer wall of the airbag can be reduced, the stability of the airbag operation can be improved, and the service life can be guaranteed.

[0046] In addition, lubricant can be applied between the airbag and the first annular wall 14, and between the airbag and the second annular wall, to further reduce the friction between the airbag and the first annular wall 14, and between the airbag and the second annular wall.

[0047] In one implementation, such as Figure 5 and Figure 6As shown, the airbag comprises an inner rubber bladder 2 and an outer polyurethane cover 1. The rubber bladder 2 has good sealing and flexibility, and can expand after inflation. The rubber bladder 2 combines the characteristics of absorbing high-frequency vibrations and being soft and easy to process. The airbag formed by the rubber bladder 2 has the characteristics of high strength, high elastic modulus, and low density. It should be noted that the rubber bladder 2 itself should not undergo significant deformation after inflation, but only return to its initial designed shape. The polyurethane cover 1 adopts a rectangular design, and there is a gap between the side wall of the polyurethane cover 1 and the apex of the triangle. The polyurethane cover 1 can restrain the deformation of the inner rubber bladder 2, reduce the contact friction between the airbag and the first circumferential wall 14 (or the second circumferential wall), and the polyurethane material used in the polyurethane cover 1 has the characteristics of good wear resistance, easy processing, simple operation, and diverse applicable working conditions. Using the polyurethane cover 1 to protect the rubber bladder 2 can further enhance the toughness, durability, and strength of the airbag.

[0048] In this example, the airbag, made of polyurethane cover 1 and rubber bladder 2, measures 500mm × 500mm × 100mm (length × width × thickness) and has a stroke of 50mm. During loading, the internal pressure of the airbag can be kept constant above 1MPa; if it reaches 1.5MPa to 2MPa, it falls into the high-pressure category.

[0049] In one implementation, such as Figure 5 and Figure 6 As shown, it also includes a return spring 4, located inside the rubber bladder 2. The first end of the return spring 4 is connected to the inner wall of the rubber bladder 2 near the fixed plate 8, and the second end is connected to the inner wall of the rubber bladder 2 near the movable plate 5. To prevent the return spring 4 from damaging the inner wall of the rubber bladder 2, a rubber pad 12 is provided between the first end of the return spring 4 and the rubber bladder 2, and another rubber pad 12 is also provided between the second end of the return spring 4 and the rubber bladder 2. The rubber pads 12 can connect both the return spring 4 and the rubber bladder 2, thus fixing the return spring 4 and effectively increasing the wall thickness of the rubber bladder 2, thereby improving its strength. When the airbag is not inflated, the return spring 4 is in its natural state. When the airbag inflates, the return spring 4 is stretched. When the airbag deflates, the return spring 4 pulls the rubber bladder 2 back to its initial size.

[0050] In one implementation, such as Figures 1-6 As shown, it also includes guide rods 7, which are used to guide the loading direction of the movable plate 5. At least two guide rods 7 are evenly distributed along the outer periphery of the receiving cavity, and three, four, or even more can be provided. The two ends of the guide rods 7 are respectively connected to the fixed plate 8 and the movable plate 5. When the airbag is inflated, the guide rods 7 can guide the movement direction of the movable plate 5, preventing the movable plate 5 from shifting its position and causing changes in the loading direction or area.

[0051] In one implementation, such as Figures 1-6 As shown, the guide rod 7 includes a sleeve and a sliding rod. The sliding rod is slidably disposed within the sleeve, meaning the sleeve can guide the axial movement of the sliding rod. The sleeve is connected to the fixed plate 8 and the sliding rod is connected to the movable plate 5, or the sleeve is connected to the movable plate 5 and the sliding rod is connected to the fixed plate 8. In short, this allows the sleeve and the sliding rod to move relative to each other when the movable plate 5 moves relative to the fixed plate 8, thereby constraining and limiting the movement state of the movable plate 5.

[0052] In one implementation, such as Figure 5 and Figure 6 As shown, the system also includes a strain gauge 3 and a pressure gauge 11. The strain gauge 3 is installed on the inner wall of the airbag, for example, by attaching it to the inner wall with industrial adhesive. After calibration, the data cable is connected to the matching data acquisition system through the wiring hole 10 to monitor the strain of the inner wall of the airbag during the test. The pressure gauge 11 is connected to the inner cavity of the airbag to monitor the inflation pressure of the airbag in real time. During the test, when the airbag is inflated, the expansion of the airbag causes the movable plate 5 to compress the test sample. At this time, the inner wall of the airbag, such as the inner wall of the rubber bladder 2, will have a certain deformation. The strain gauge 3 can monitor the magnitude of this deformation and provide corresponding data. At the same time, the pressure gauge 11 can obtain the pressure inside the rubber bladder 2. Through the test, the relationship between the pressure value of the pressure gauge 11 and the strain value of the strain gauge 3 can be obtained, and then the correlation data or table between the two can be obtained. Furthermore, the data from the strain gauge 3 can be used to provide calibration and reference for the data monitored by the pressure gauge 11, ensuring the accuracy of the test. In addition, the installation of the strain gauge 3 can also provide early warning of the ultimate state of the airbag, avoiding the safety accident of airbag bursting.

[0053] In one embodiment, the airbag is provided with a wire hole 10, which passes through the polyurethane cover 1 and the rubber bladder 2 of the airbag and serves as the wiring channel for connecting the strain gauge 3 to the data acquisition instrument. A rubber sealing ring is provided inside the wire hole 10. When the data line of the strain gauge 3 passes through the wire hole 10, the data line will squeeze the rubber sealing ring, and the high-pressure gas will also force the rubber sealing ring to fit and seal. The wire hole 10 has a self-sealing effect, which can ensure the airtightness of the airbag.

[0054] In one implementation, such as Figure 1 , Figure 2 , Figure 4 and Figure 6 As shown, it also includes a displacement sensor 6, which is mounted on a fixed plate 8. The probe of the displacement sensor 6 abuts against a movable plate 5. When the movable plate 5 moves away from the fixed plate 8 relative to the fixed plate 8, the probe of the displacement sensor 6 remains in contact with the movable plate 5 as the movable plate 5 moves. The movement of the probe can obtain the corresponding displacement data, thereby obtaining the displacement data of the movable plate 5.

[0055] In this example, displacement sensor 6 can be an LVDT sensor. LVDT (Linear Variable Differential Transformer) is a high-precision displacement sensor widely used in industrial, scientific research, and military fields. The LVDT displacement sensor consists of a lightweight iron core and a carbon fiber composite shell, with a measurement range of 0.5mm to 50mm. After calibration, one end of the carbon fiber composite shell is fixed to the designed position on the fixed plate 8 using industrial adhesive. The lightweight iron core extends naturally at one end, contacting the surface of the movable plate 5. During the test, the elongation of the lightweight iron core is monitored, thereby measuring the relative surface displacement of the test sample. Furthermore, the carbon fiber composite shell is lightweight and high-strength.

[0056] In one implementation, such as Figures 1-3 , Figure 5 and Figure 6 As shown, the airbag is provided with a vent 9. There can be one vent 9, which is used for air intake and exhaust, or there can be two vent 9, one for air intake and the other for exhaust.

[0057] This example uses a single vent 9, which is equipped with a one-way air intake valve. The one-way air intake valve allows for one-way inflation of the airbag, preventing gas leakage after inflation. When it is necessary to vent, the one-way air intake valve can be pressed to make it a two-way passage, allowing for venting. The specific structure can be referenced from the one-way air intake valve of a bicycle valve.

[0058] Combination Figures 1 to 7 As shown, the present invention also provides a pressure loading method, using an actuator as described above, including the following:

[0059] S1. Install the fixed plate 8 on the test device, with the movable plate 5 facing the test sample;

[0060] S2. Inflate the airbag. After the airbag is inflated, it expands and pushes the movable plate 5 to squeeze the test sample. By controlling the inflation size, the squeezing force of the movable plate 5 on the test sample can be controlled.

[0061] S3. By utilizing the flexibility of the airbag, the adaptability to the vibration frequency of the test sample is improved. In this process, the vibration can be recorded using the test device to conduct corresponding vibration tests.

[0062] S4. After the pressure loading is completed, release the gas in the airbag to relieve the pressure of the movable plate 5 on the test sample.

[0063] In one embodiment, applying a load to a test specimen during a shaking table test to simulate high stress includes the following steps:

[0064] (1) In the test preparation stage, the elastic modulus E and Poisson's ratio ν of the test sample are obtained through mechanical testing, and the initial wall thickness t and the initial planar radius R1 of the airbag are measured, such as... Figure 8 The image shows a partial cross-section of the airbag. It should be noted that the airbag can be a single-layer structure or a double-layer structure.

[0065] (2) Before the test, use high-strength bolts 13 to fix the actuator fixing plate 8 on the test device, and apply Vaseline to the surface of the airbag and the surface of the fixing plate to reduce the friction between the airbag volume expansion and the tip during the loading process. Connect the strain gauge 3 and make adjustments. Calibrate the pressure gauge 11 to zero, perform inflation preloading, check the working performance of the airbag, displacement sensor 6 and guide rod 7, and obtain the elastic modulus E and Poisson's ratio ν of the test sample through mechanical testing.

[0066] (3) During the test loading, the output air pressure P0 of the air pump is precisely adjusted to provide air source for the airbag. After the airbag is inflated, its volume expands and pushes the movable plate 5 to produce translation along the axial direction parallel to the guide rod 7. The movable plate 5 drives the loading plate to squeeze the test sample together, simulating the loading condition of the test sample bearing high stress load.

[0067] (4) During the test, the displacement data u0 of the test sample is monitored by displacement sensor 6, the strain data ε of the airbag during the loading process is collected by strain gauge 3, the air pressure of the inflation pump is precisely adjusted to the test design air pressure P1, and the pressure is checked by pressure gauge 11. The radius R2 of the airbag inflation part is measured, and the angle α between the outer normal direction OB of the airbag inflation part and the horizontal axis direction is measured.

[0068] (5) Based on the strain data ε during the loading process, the test design air pressure P1, the radius R2 of the inflated part of the airbag, and the included angle α, the loading displacement u1 of the actuator can be calculated using the following formula:

[0069]

[0070] In the formula, K is the interaction coefficient between the first groove, the second groove and the airbag during loading; W is the initial width of the airbag when it is not loaded; t is the wall thickness of the airbag. When a double-layer structure is adopted, t = t1 + t2, where t1 is the wall thickness of the polyurethane cover 1 and t2 is the wall thickness of the rubber bladder 2; E and ν are the elastic modulus and Poisson's ratio of the test sample, respectively; P1 is the design air pressure; f1 is the load-bearing capacity of the airbag at the design air pressure P1; ε is the strain data of the airbag collected by strain gauge 3 during loading; C is the wall thickness correction coefficient of the airbag bulging part during loading; N1 and N2 are the membrane stress in the meridian direction of the airbag bulging part during loading, respectively.

[0071] (6) Based on the data ε monitored by the strain gauge during the loading process, combined with the physical and mechanical parameters of the airbag and the elastic modulus E and Poisson's ratio ν of the test sample, the change process of the load displacement of the test sample by the actuator during the loading process can be reflected. The reliability of this method is verified by comparing it with the displacement data u0 of the test sample monitored by the displacement sensor 6.

[0072] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An actuator, characterized in that, include: A fixing plate, which is used to connect to the test device, is provided with a first groove; A movable plate is used to abut against a test sample. The movable plate is provided with a second groove. The openings of the first groove and the second groove are arranged opposite to each other to form a receiving cavity. The top end of the first groove and the top end of the second groove are spaced apart. And an airbag, which is installed in the receiving cavity, and is used to push the movable plate relative to the fixed plate by inflating the airbag.

2. The actuator according to claim 1, characterized in that: The first groove is formed by a first circumferential wall, the cross-section of the first circumferential wall along the loading direction is triangular, and the cross-section of the first groove gradually increases from the inner bottom of the first groove towards the opening direction of the first groove; the second groove is formed by a second circumferential wall, the cross-section of the second circumferential wall along the loading direction is triangular, and the cross-section of the second groove gradually increases from the inner bottom of the second groove towards the opening direction of the second groove.

3. The actuator according to claim 2, characterized in that: The airbag includes an inner rubber bladder and an outer polyurethane cover. The polyurethane cover has a rectangular design, and there is a gap between the sidewall of the polyurethane cover and the apex of the triangle. The gap is used to accommodate the lateral deformation of the airbag during the loading process.

4. The actuator according to claim 3, characterized in that: It also includes a return spring, the first end of which is connected to the inner wall of the rubber bladder near the fixed plate, and the second end of which is connected to the inner wall of the rubber bladder near the movable plate. The two ends of the return spring are connected to the rubber bladder via rubber pads. When the air bladder is not inflated, the return spring is in a natural state. When the air bladder is inflated, the return spring is stretched.

5. The actuator according to claim 1, characterized in that: It also includes guide rods, which are used to guide the loading direction of the movable plate. At least two guide rods are evenly distributed along the outer periphery of the receiving cavity, and the two ends of the guide rods are respectively connected to the fixed plate and the movable plate.

6. The actuator according to claim 5, characterized in that: The guide rod includes a sleeve and a slide rod, with the slide rod slidably disposed within the sleeve; the sleeve is connected to the fixed plate and the slide rod is connected to the movable plate, or the sleeve is connected to the movable plate and the slide rod is connected to the fixed plate.

7. The actuator according to claim 1, characterized in that: It also includes a strain gauge and a pressure gauge, wherein the strain gauge is disposed on the inner wall of the airbag and the pressure gauge is connected to the inner cavity of the airbag.

8. The actuator according to claim 1, characterized in that: It also includes a displacement sensor, which is mounted on the fixed plate and the probe of the displacement sensor abuts against the movable plate.

9. The actuator according to claim 1, characterized in that: The airbag is provided with a vent, and the vent is provided with a one-way air intake valve.

10. A pressure loading method, characterized in that, The actuator as described in any one of claims 1-9 includes the following: S1. Install the fixed plate on the test device, with the movable plate facing the test sample; S2. Inflate the airbag, and the airbag expands after inflation, pushing the movable plate to squeeze the test sample; S3. Initiate the vibration test, utilizing the flexibility of the airbag to improve the adaptability of the actuator to the vibration frequency of the test sample; S4. After the pressure loading is completed, the gas inside the airbag is released to relieve the pressure of the movable plate on the test sample.

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