Fatigue testing apparatus and method for synchronous examination of cushion hanger joints and housings

Abstract

The application provides a fatigue test device and method for synchronous examination of a buffer strut joint and a frame body, and the device comprises a bottom plate, a support arranged on the bottom plate, the support being used for mounting and supporting a test piece, the test piece comprising a main buffer strut joint and a connected frame body, a cylinder support frame arranged on the bottom plate, a load loading angle adjusting assembly connected with the cylinder support frame, a cylinder and a force sensor, one end of the cylinder and the force sensor being connected with the test piece, and the other end being connected with the load loading angle adjusting assembly, wherein the fatigue load loading of the main buffer strut joint and the connected frame body is realized by applying the load through the cylinder and monitoring by using the force sensor, and the synchronous examination of the main buffer strut joint and the connected frame body is realized through the fatigue test device.

Description

Technical Field

[0001] This application belongs to the field of fatigue testing technology for helicopter main landing buffer strut joints and their connecting frames, specifically relating to a fatigue testing device and method for synchronously testing the buffer strut joint and its frame. Background Technology

[0002] The main landing strut joint and its connecting frame connect to the landing strut, forming a key component of the helicopter landing mechanism. Due to the frequent takeoffs and landings of helicopters, the main landing strut joint and its connecting frame are at risk of fatigue failure. Based on past experience, fatigue failure is the main failure mode, and its fatigue characteristics are crucial to the helicopter's flight safety.

[0003] The device of this invention relates to the main landing buffer strut joint and its connecting frame. This structure is representative and typical in helicopter landing gear. In order to simultaneously assess the fatigue life of the main landing buffer strut joint and its connecting frame in the test to shorten the test cycle, no device design and test method that can be used for reference have been found so far. Summary of the Invention

[0004] Objective: To address the fatigue testing of the main lifting buffer strut joint and its connecting frame, a synchronous testing device is proposed. This device simulates the installation boundary conditions of the main lifting buffer strut joint and its connecting frame, applies the buffer strut load to the strut joint, and transfers the load to the connecting frame through the strut joint. Through a rationally designed structure, it meets the stringent requirements of the fixture design for load escalation during the fatigue test of the strut joint, ultimately achieving simultaneous fatigue testing of the main lifting buffer strut joint and its connecting frame on the same testing device. This device features a simple structure, good economy, stable and reliable performance, ensures loading accuracy, effectively meets testing requirements, and shortens the testing cycle.

[0005] In a first aspect, this application provides a fatigue testing device for simultaneous testing of the buffer support joint and the frame, the device comprising:

[0006] Base plate;

[0007] A support member is provided on the base plate. The support member is used to install and support the test specimen. The test specimen includes a main buffer support joint and its connecting frame.

[0008] An actuator cylinder support frame is mounted on the base plate;

[0009] The load loading angle adjustment component is connected to the actuating cylinder support frame;

[0010] The actuator and force sensor are connected at one end to the test piece and at the other end to the load loading angle adjustment assembly.

[0011] The load is applied by the actuating cylinder and monitored by the force sensor to achieve fatigue load loading on the main lifting buffer support joint and its connecting frame. The fatigue testing device enables the synchronous testing of the main lifting buffer support joint and its connecting frame.

[0012] Preferably, the device further includes:

[0013] A pressure plate assembly is used to press the test specimen.

[0014] Preferably, the pressure plate assembly further includes:

[0015] The pressure plate has its lower surface in contact with the curved surface of the frame. The pressure plate is made into a thin plate near the joint area to achieve real force transmission to the frame. An opening is provided in the middle of the thin plate, and the joint extends out from the opening. The pressure plate is used to initially position the test piece and restrict its planar movement by means of bolts and nuts.

[0016] Preferably, the pressure plate assembly further includes:

[0017] Multi-threaded hole bearing blocks are disposed on both sides of the pressure plate, and the multi-threaded hole bearing blocks further press the pressure plate by clamping screws.

[0018] Preferably, the actuating cylinder support frame includes:

[0019] A column is mounted on the base plate, and the column is used to install the load loading angle adjustment component.

[0020] Preferably, the load loading angle adjustment component includes:

[0021] The adjusting base includes a rectangular plate and a connecting part disposed on the rectangular plate, the connecting part being connected to the bottom of the actuating cylinder;

[0022] The base clamping plate is connected to the rectangular plate by bolts and nuts and is clamped to the column.

[0023] Preferably, the load loading angle adjustment component is capable of moving up and down along the column.

[0024] Secondly, this application also provides a fatigue test method for simultaneous testing of the buffer support joint and the frame, the method comprising:

[0025] Step 1: First, fix the test piece to the left test piece support, and then connect it to the right test piece support;

[0026] Step 2: Place the test piece pressure plate against the curved surface of the test piece, and use bolts and nuts to initially position the test piece and restrict its planar movement;

[0027] Step 3: Use the matching left-side multi-threaded bearing block, clamping bolt and washer to further clamp the left side of the test piece plate, then use a similar method to clamp the right side of the test piece plate, and tighten the nut again;

[0028] Step 4: Connect the main support strut joint and force sensor in the test specimen using the load loading connector, and tighten them with locknuts;

[0029] Step 5: Connect the bottom of the actuator cylinder to the load loading angle adjustment component, and connect the load loading angle adjustment component to the actuator cylinder support frame. With the help of the angle gauge, move the loading angle adjustment component up and down until the loading angle requirement is met.

[0030] Step 6: After the test specimen and test device are assembled, apply fatigue load starting from the first level of load and gradually increase the load by a certain proportion.

[0031] Step 7: During the test, the test pieces need to be checked regularly to see if cracks or failures occur. After verification with multiple test pieces, it was found that the connecting frame was the first to crack or fail. Record the number of fatigue cycles caused by the crack or failure at this time.

[0032] Step 8: After the connecting frame develops cracks or fails, continue the test under the current fatigue load, and then increase the load to continue to assess the fatigue performance of the main lifting buffer support joint until the design requirements are met or the joint develops cracks or fails. Terminate the test and record the number of fatigue cycles.

[0033] This application has the following technical advantages:

[0034] The fatigue testing device for the main landing gear buffer strut joint and its connecting frame designed in this invention can realistically and accurately simulate the installation boundary conditions and load characteristics of the main landing gear buffer strut joint and its connecting frame. It enables simultaneous testing of the main landing gear buffer strut joint and its connecting frame using a single fatigue testing device, thus improving the strength testing level of the helicopter landing gear. Using this testing device, the total test error can be controlled within 3%.

[0035] Field tests have demonstrated that the loading device can accurately simulate the installation boundary conditions and load characteristics of the test piece in fatigue tests, providing a realistic and accurate testing environment. It enables stable loading of the main buffer support joint and its connecting frame under the load of the buffer support, effectively reducing the number of test interruptions caused by unstable or damaged test fixtures, and the test data are good. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the load on the main buffer support joint and its connecting frame provided in the embodiments of this application;

[0037] Figure 2 This is a schematic diagram of the test specimen structure provided in the embodiments of this application (including the main buffer support joint and its connecting frame);

[0038] Figure 3 This is a schematic diagram of the overall structure of the test apparatus provided in the embodiments of this application;

[0039] Figure 4 This is a schematic diagram of the support structure provided in the embodiments of this application;

[0040] Figure 5 This is a schematic diagram of the test specimen pressure plate assembly provided in the embodiments of this application;

[0041] Figure 6 This is a schematic diagram of the load-loading joint structure provided in the embodiments of this application;

[0042] Figure 7 This is a schematic diagram of the load loading angle adjustment component provided in the embodiments of this application. Detailed Implementation

[0043] The device of this invention includes a test specimen support, a test specimen clamping mechanism, a load loading joint, a load loading angle adjustment mechanism, an actuating cylinder support frame, and a test device base plate. It simulates the real boundary conditions and load characteristics of the main lifting buffer support joint and its connecting frame. Among them, the key mechanism, the test specimen clamping mechanism, has a plate thickness in the connection area with the test specimen that is consistent with the actual fuselage skin (the area around the buffer support joint). This mechanism can realize the real force transmission and effective fixation of the test specimen during the test, and at the same time, it can meet the load upgrade requirements of the main lifting buffer support joint.

[0044] The device and testing method of this invention can achieve synchronous loading of the main buffer support joint and its connecting frame for fatigue testing, which can effectively improve testing efficiency, shorten the testing cycle and reduce testing costs.

[0045] Please see Figures 1-7 The technical solution of the present invention is as follows: The fatigue test loading device for the main buffer support column joint and its connecting frame consists of a test piece support 1, a test piece pressure plate assembly 2, a load loading joint 3, a load loading angle adjustment assembly 4, an actuating cylinder support frame 5, a test device base plate 6, an actuating cylinder and a force sensor 7.

[0046] During the test, fatigue loads were applied to the main lifting buffer support joint and its connecting frame by means of an actuating cylinder and a force sensor. This fatigue testing apparatus allows for simultaneous evaluation of the main lifting buffer support joint and its connecting frame, significantly shortening the testing cycle and effectively reducing testing costs.

[0047] Figure 4This is a schematic diagram of the test specimen support structure on the left. First, the test specimen support 1 on the left is installed on the base plate 6 of the test device using the first bolt 1-3. Then, the left side of the test specimen is connected to the left test specimen support plate 1-1 using the second bolt 1-2. Similarly, the right side of the test specimen is connected to the right support using a similar method.

[0048] Among them, 1-1 is the test piece support plate; 1-2 is the second bolt (connecting the base plate); and 1-3 is the first bolt (connecting the test piece).

[0049] Figure 5 This is a schematic diagram of the test specimen clamping mechanism. In this diagram, 2-1 is a multi-threaded hole bearing block; 2-2 is a clamping bolt; 2-3 is a clamping bolt washer; 2-4 is a test specimen pressure plate (the lower surface of the pressure plate fits against the curved surface of the frame, and the pressure plate is made into a thin plate near the joint area to achieve real force transmission to the frame); 2-5 is the third bolt (which restricts the planar movement of the test specimen); and 2-6 is the first nut.

[0050] Place the test plate 2-4 on the upper curved surface of the test piece. The lower surface of the test plate needs to be milled to fit the upper curved surface of the test piece. The upper surface of the test plate near the buffer support joint also needs to be milled to ensure that its plate thickness is consistent with the actual fuselage skin, thereby achieving an effective and realistic force transmission process. The test plate needs to leave assembly space for the buffer support joint. The test piece is initially positioned and its planar movement is restricted by the third bolt 2-5 and the first nut 2-6 (a total of 10 pairs of bolts and nuts). After completing the above operations, the left side of the test plate is further tightened using the matching left-side multi-threaded hole bearing block 2-1 (which is welded to the inner side of the left-side test piece support), the clamping bolt 2-2, and the washer 2-3. Similarly, the right side of the test plate is tightened using a similar method. Since the above tightening operations will cause the gap between the first nut 2-6 and the mating surface to be tightened, the first nut 2-6 needs to be tightened again. Test results have demonstrated that the clamping mechanism can effectively reduce the number of test interruptions caused by instability or damage to the test fixtures, meet the stringent strength and stiffness requirements brought about by the load escalation in the fatigue test of the main lifting buffer strut joint, and thus ensure the continuous and stable operation of the test.

[0051] Figure 6 This is a schematic diagram of the load-loading joint structure, where: 3-1 is the second nut; 3-2 is the spherical plain bearing; 3-3 is the fourth bolt; 3-4 is the load-loading joint connector; and 3-5 is the lock nut.

[0052] The front end of the load loading connector 3 is connected to the main buffer support connector in the test piece via the second nut 3-1, the spherical bearing 3-2 and the fourth bolt 3-3. The rear end of the load loading connector 3 is connected to the actuating cylinder and the force sensor 7 via the load loading connector connector 3-4 and is locked by the locking nut 3-5.

[0053] Figure 7 It is a load loading angle adjustment mechanism, wherein: 4-1 is the third nut; 4-2 is the adjustment base; 4-3 is the fifth bolt; 4-4 is the fourth nut; 4-5 is the washer; and 4-6 is the base clamping plate.

[0054] In addition to serving as the base of the actuating cylinder, the bottom of the actuating cylinder is connected to the adjusting base 4-2 via the fifth bolt 4-3. The fifth bolt 4-3 passes through the adjusting base 4-2 and the base clamping plate 4-6. With the use of the fourth nut 4-4 and the washer 4-5, the load loading angle adjustment mechanism 4 is connected to the actuating cylinder support frame 5. The load loading angle adjustment mechanism 4 can move up and down on the actuating cylinder base frame 5 to adjust the loading angle of the actuating cylinder. The actuating cylinder base frame 5 is fixedly connected to the base plate 6 of the test device via bolts.

[0055] In summary, this fatigue testing device for the main lifting buffer support joint and its connecting frame can accurately simulate load boundary conditions. Its ingenious structural design offers good adjustability and facilitates installation and disassembly. It meets the fatigue testing requirements of the test specimens (including the main lifting buffer support joint and its connecting frame) under synchronous loading. This allows for the simultaneous assessment of fatigue characteristics, replacing the previous requirement of separate testing on two separate machines. This device is used to determine the fatigue life and weak points of the test specimens. It effectively reduces testing costs while shortening the testing cycle, demonstrating good economic efficiency. Furthermore, actual testing has proven that the device operates stably, with the total testing error controlled within 3%.

[0056] In other embodiments of this application, the provided testing method includes the following steps:

[0057] Step 1: First, fix the test piece to the left test piece support 1, and then connect it to the right test piece support;

[0058] Step 2: Place the test piece pressure plate 2-4 against the upper curved surface of the test piece, and use 10 pairs of bolts and nuts to initially position the test piece and restrict its planar movement;

[0059] Step 3: Use the matching left-side multi-threaded bearing block 2-1, clamping bolt 2-2 and washer 2-3 to further clamp the left side of the test piece plate, then use a similar method to clamp the right side of the test piece plate, and tighten the nut 2-6 again;

[0060] Step 4: Connect the main support strut joint and force sensor in the test piece using the load loading connector, and tighten them using lock nuts 3-5;

[0061] Step 5: Connect the bottom of the actuating cylinder to the load loading angle adjustment component 4, and connect the load loading angle adjustment component 4 to the actuating cylinder support frame 5. With the help of the angle gauge, move the loading angle adjustment mechanism up and down until the loading angle requirement is met.

[0062] Step 6: After the test specimen and test device are assembled, apply fatigue load starting from the first level of load and gradually increase the load by a certain proportion.

[0063] Step 7: During the test, the test pieces need to be checked regularly to see if cracks or failures occur. After verification with multiple test pieces, it was found that the connecting frame was the first to crack or fail. Record the number of fatigue cycles caused by the crack or failure at this time.

[0064] Step 8: After the connecting frame develops cracks or fails, continue the test under the current fatigue load, and then increase the load to continue to assess the fatigue performance of the main lifting buffer support joint until the design requirements are met or the joint develops cracks or fails. Terminate the test and record the number of fatigue cycles.

[0065] Through the above test methods, the fatigue test of the main buffer support joint and its connecting frame was finally achieved simultaneously.

Claims

1. A fatigue testing device for simultaneous evaluation of the buffer support joint and the frame, characterized in that, The device includes: Base plate; A support member is provided on the base plate. The support member is used to install and support the test specimen. The test specimen includes a main buffer support joint and its connecting frame. An actuator cylinder support frame is mounted on the base plate; The load loading angle adjustment component is connected to the actuating cylinder support frame; The actuator and force sensor are connected at one end to the test piece and at the other end to the load loading angle adjustment assembly. The load is applied by the actuating cylinder and monitored by the force sensor to achieve fatigue load loading on the main lifting buffer support joint and its connecting frame. The fatigue testing device enables the synchronous assessment of the main lifting buffer support joint and its connecting frame. The device further includes: A pressure plate assembly is used to clamp the test specimen; The pressure plate assembly includes: The pressure plate has its lower surface in contact with the curved surface of the frame. The pressure plate is made into a thin plate near the joint area to achieve real force transmission to the frame. An opening is provided in the middle of the thin plate, and the joint extends out from the opening. The pressure plate is used to initially position the test piece and restrict its planar movement by means of bolts and nuts.

2. The apparatus according to claim 1, characterized in that, The pressure plate assembly also includes: Multi-threaded hole bearing blocks are disposed on both sides of the pressure plate, and the multi-threaded hole bearing blocks further press the pressure plate by clamping screws.

3. The apparatus according to claim 1, characterized in that, The actuator cylinder support frame includes: A column is mounted on the base plate, and the column is used to install the load loading angle adjustment component.

4. The apparatus according to claim 3, characterized in that, The load loading angle adjustment component includes: The adjusting base includes a rectangular plate and a connecting part disposed on the rectangular plate, the connecting part being connected to the bottom of the actuating cylinder; The base clamping plate is connected to the rectangular plate by bolts and nuts and is clamped to the column.

5. The apparatus according to claim 3, characterized in that, The load-loading angle adjustment component can move up and down along the column.

6. A fatigue test method for simultaneously evaluating the joint and frame of a buffer support column, characterized in that, The method is applied to the apparatus as described in any one of claims 1-5, and the method comprises: Step 1: First, fix the test piece to the left test piece support, and then connect it to the right test piece support; Step 2: Place the test piece pressure plate against the curved surface of the test piece, and use bolts and nuts to initially position the test piece and restrict its planar movement; Step 3: Use the matching left-side multi-threaded bearing block, clamping bolt and washer to further clamp the left side of the test piece plate, then use a similar method to clamp the right side of the test piece plate, and tighten the nut again; Step 4: Connect the main support strut joint and force sensor in the test specimen using the load loading connector, and tighten them with locknuts; Step 5: Connect the bottom of the actuator cylinder to the load loading angle adjustment component, and connect the load loading angle adjustment component to the actuator cylinder support frame. With the help of the angle gauge, move the loading angle adjustment component up and down until the loading angle requirement is met. Step 6: After the test specimen and test device are assembled, apply fatigue load starting from the first level of load and gradually increase the load by a certain proportion. Step 7: During the test, the test pieces need to be checked regularly to see if cracks or failures occur. After verification with multiple test pieces, it was found that the connecting frame was the first to crack or fail. Record the number of fatigue cycles caused by the crack or failure at this time. Step 8: After the connecting frame develops cracks or fails, continue the test under the current fatigue load, and then increase the load to continue to assess the fatigue performance of the main lifting buffer support joint until the design requirements are met or the joint develops cracks or fails. Terminate the test and record the number of fatigue cycles.

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