Fatigue test device and method for synchronous assessment of buffer strut joint and frame body

Abstract

The invention provides a fatigue test device and method for synchronous assessment of a buffer strut joint and a frame body. The device comprises a bottom plate; the supporting piece is arranged on the bottom plate, the supporting piece is used for installing and supporting a test piece, and the test piece comprises a main buffering supporting column connector and a connecting frame body of the main buffering supporting column connector; the actuating cylinder supporting frame is arranged on the bottom plate; the load loading angle adjusting assembly is connected with the actuating cylinder supporting frame; one end of the actuating cylinder and force sensor is connected with the test piece, and the other end of the actuating cylinder and force sensor is connected with the load loading angle adjusting assembly; wherein the actuating cylinder is used for applying load, the force sensor is used for monitoring, fatigue load loading of the main buffer strut joint and the connecting frame of the main buffer strut joint is achieved, and synchronous examination of the main buffer strut joint and the connecting frame of the main buffer strut joint is achieved through the fatigue test device.

Description

Technical Field

[0001] This application belongs to the technical field of fatigue test of the main landing buffer strut joint of a helicopter and its connecting frame, and specifically relates to a fatigue test device and method for synchronously evaluating the buffer strut joint and the frame. Background Art

[0002] The main landing buffer strut joint of a helicopter and its connecting frame are connected to the buffer strut, constituting a key component of the helicopter's landing mechanism. Due to the frequent takeoff and landing characteristics of the helicopter, the main landing buffer strut joint and its connecting frame are at risk of fatigue damage. According to past experience, fatigue damage is the main failure mode, and its fatigue characteristics are related to the flight safety of the helicopter.

[0003] The device of the present invention relates to the main landing buffer strut joint and its connecting frame. This structure is representative and typical in the helicopter landing gear. In order to synchronously evaluate 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 has been found yet. Summary of the Invention

[0004] Object of the Invention: For the main landing buffer strut joint and its connecting frame, a synchronous evaluation device is proposed for its fatigue test. This device simulates the installed boundary conditions of the main landing 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. By reasonably designing the structure, the severe requirements for fixture design in the load upgrade during the fatigue test of the strut joint are realized. Finally, the fatigue tests of the main landing buffer strut joint and its connecting frame are synchronously completed on the same set of test devices. This device has a simple structure, good economy, stable and reliable working performance, can ensure the loading accuracy, can effectively meet the test requirements and shorten the test cycle.

[0005] In a first aspect, the present application provides a fatigue test device for synchronously evaluating a buffer strut joint and a frame, the device comprising:

[0006] A base plate;

[0007] A support member, arranged on the base plate, the support member being used for installing and supporting a test piece, the test piece including a main landing buffer strut joint and its connecting frame;

[0008] An actuator support frame, arranged on the base plate;

[0009] A load loading angle adjustment assembly, connected to the actuator support frame;

[0010] An actuator and a force sensor, one end connected to the test piece and the other end connected to the load loading angle adjustment assembly;

[0011] Among them, the load is applied by the actuator and monitored by the force sensor to achieve fatigue load loading on the main starting buffer support joint and its connecting frame. Through this fatigue testing device, the main starting buffer support joint and its connecting frame can be synchronously assessed.

[0012] Preferably, the device further comprises:

[0013] A pressing plate assembly is used to press the test piece.

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

[0015] The lower surface of the pressure plate is fitted 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 from the opening. The pressure plate uses bolts and nuts to preliminarily position the test piece and limit its planar movement.

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

[0017] The multi-threaded hole bearing blocks are arranged on both sides of the pressure plate, and the multi-threaded hole bearing blocks further press the pressure plate through the pressing screws.

[0018] Preferably, the actuator support frame comprises:

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

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

[0021] An adjusting base, comprising a rectangular plate and a connecting portion provided on the rectangular plate, wherein the connecting portion is connected to the bottom of the actuating cylinder;

[0022] The base pressing plate is connected to the rectangular plate through bolts and nuts and is clamped on the column.

[0023] Preferably, the load-applying angle adjustment assembly is capable of moving up and down along the column.

[0024] In a second aspect, the present application further provides a fatigue test method for synchronously assessing a buffer support joint and a frame, the method comprising:

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

[0026] Step 2: Place the test piece pressure plate on the upper curved surface of the test piece, and use bolts and nuts to achieve preliminary positioning of the test piece and restrict its planar movement;

[0027] Step 3: Use the matching left multi-threaded hole bearing block, clamping bolts and washers to further tighten the left side of the test piece pressure plate. Then use a similar method to tighten the right side of the test piece pressure plate and tighten the nuts again.

[0028] Step 4: Use the load-applying connector to connect the main lifting and buffering support connector and the force sensor in the test piece, and lock them with the lock nut.

[0029] Step 5: Connect the bottom of the actuator to the load angle adjustment assembly, and connect the load angle adjustment assembly to the actuator support frame. Using an inclinometer, move the load angle adjustment assembly up and down until the required loading angle is reached.

[0030] Step 6: After the above test piece and test device are assembled, fatigue load is applied starting from the first level load, and the load is increased step by step according to a certain proportion;

[0031] Step 7: During the test, the test piece must be regularly checked for cracks or damage. Multiple test pieces have been used to verify that the connection frame is the first to crack or damage. The number of fatigue cycles resulting from the crack or damage is recorded.

[0032] Step 8: After cracks or damage occur in the connection frame, continue to complete the test under the fatigue load of the current level, and then upgrade the load to continue to assess the fatigue performance of the main buffer support joint until the design requirements are met or the joint cracks or damage occurs, terminate the test and record the number of fatigue cycles.

[0033] This application has the following technical effects:

[0034] The fatigue testing apparatus designed by this invention for the main lift buffer strut joint and its connecting frame accurately simulates the installation boundary conditions and loading characteristics of the main lift buffer strut joint and its connecting frame. This allows for simultaneous assessment of the main lift buffer strut joint and its connecting frame using a single fatigue testing apparatus, improving the strength testing capabilities of helicopter landing gear. The total test error can be controlled within 3% using this testing apparatus.

[0035] Field tests have proved that the loading device can accurately simulate the installation boundary conditions and loading characteristics of the test piece in fatigue tests, provide a real and accurate assessment environment, and achieve stable loading of the main buffer support joint and its connecting frame under the action of the buffer support load, effectively reducing the number of test interruptions caused by instability or damage of the test fixture, and the test data is good. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 2 It is a schematic structural diagram of the test piece provided by an embodiment of the present application (including the main landing gear shock strut joint and its connecting frame).

[0038] Figure 3 It is a schematic overall structural diagram of the test device provided by an embodiment of the present application.

[0039] Figure 4 It is a schematic structural diagram of the support member provided by an embodiment of the present application.

[0040] Figure 5 It is a schematic structural diagram of the test piece pressing plate assembly provided by an embodiment of the present application.

[0041] Figure 6 It is a schematic structural diagram of the load loading joint provided by an embodiment of the present application.

[0042] Figure 7 It is a schematic structural diagram of the load loading angle adjustment assembly provided by an embodiment of the present application. Specific embodiments

[0043] In the device of the present invention, a test piece support member, a test piece pressing mechanism, a load loading joint, a load loading angle adjustment mechanism, an actuator support frame, and a test device bottom plate are designed to simulate the real boundary conditions and loading characteristics of the main landing gear shock strut joint and its connecting frame. Among them, the plate thickness of the connection area between the key mechanism test piece pressing mechanism and the test piece is the same as that of the real fuselage skin (the area around the shock strut joint). This mechanism can achieve the real force transmission and effective fixation of the test piece during the test, and at the same time meet the requirements of load upgrade of the main landing gear shock strut joint.

[0044] The device and test method of the present invention can achieve synchronous loading of the fatigue test of the main landing gear shock strut joint and its connecting frame, effectively improve the test efficiency, shorten the test cycle, and reduce the test cost.

[0045] Please refer to Figure 1-Figure 7 , the technical solution of the present invention: The fatigue test loading device for the main landing gear shock strut joint and its connecting frame is composed of a test piece support member 1, a test piece pressing plate assembly 2, a load loading joint 3, a load loading angle adjustment assembly 4, an actuator support frame 5, a test device bottom plate 6, and an actuator and force sensor 7.

[0046] During the test, the fatigue load of the main landing gear shock strut joint and its connecting frame is loaded by applying a load through the actuator and monitoring with a force sensor. Through this set of fatigue test devices, the synchronous assessment of the main landing gear shock strut joint and its connecting frame can be achieved, significantly shortening the test cycle and effectively reducing the test cost.

[0047] Figure 4It is a schematic diagram of the test piece support structure on the left side. First, the test piece support 1 on the left side is installed on the test device base plate 6 through the first bolt 1-3, and then the left side of the test piece is connected to the test piece support plate 1-1 on the left side through the second bolt 1-2. Similarly, the right side of the test piece is connected to the support member on the right side through a similar method.

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

[0049] Figure 5 It is a schematic diagram of the test piece clamping mechanism structure, wherein 2-1 is a multi-threaded hole bearing block; 2-2 is a clamping bolt; 2-3 is a clamping bolt gasket; 2-4 is a test piece pressure plate (the lower surface of the pressure plate fits with 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 (to limit the plane movement of the test piece); 2-6 is the first nut.

[0050] Place the test piece pressure plate 2-4 on the upper curved surface of the test piece. The lower surface of the test piece pressure plate needs to be milled to fit the upper curved surface of the test piece. The upper surface of the test piece pressure plate near the buffer strut joint also needs to be milled to ensure that its plate thickness is consistent with the real fuselage skin, so as to achieve an effective and real force transmission process. The test piece pressure plate needs to leave assembly space for the buffer strut joint. The test piece is preliminarily 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, use the matching left multi-threaded hole bearing block 2-1 (which is welded to the inner side of the left test piece support), tightening bolt 2-2 and gasket 2-3 to further tighten the left side of the test piece pressure plate. Similarly, tighten the right side of the test piece pressure plate using a similar method. Since the above tightening operation will cause a gap between the first nut 2-6 and the mating surface, the first nut 2-6 needs to be tightened again. Tests and inspections have shown that the test piece clamping mechanism can effectively reduce the number of test interruptions caused by instability or damage of the test fixture, meet the stringent strength and stiffness requirements brought about by load upgrades in fatigue tests of the main lifting buffer strut joints, 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 bearing; 3-3 is the fourth bolt; 3-4 is the loading joint connector; 3-5 is the locking nut

[0052] The front end of the load loading joint 3 is connected to the main buffer support joint in the test piece through the second nut 3-1, the joint bearing 3-2 and the fourth bolt 3-3. The rear end of the loading joint 3 is connected to the actuator and the force sensor 7 through the loading joint connector 3-4 and 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 gasket; 4-6 is the base clamping plate.

[0054] Taking into account the role of the actuator cylinder base, the bottom of the actuator cylinder is connected to the adjustment base 4-2 through the fifth bolt 4-3. The fifth bolt 4-3 passes through the adjustment base 4-2 and the base clamping plate 4-6, and cooperates with the use of the fourth nut 4-4 and the gasket 4-5 to realize the connection between the load loading angle adjustment mechanism 4 and the actuator cylinder support frame 5. The load loading angle adjustment mechanism 4 can move up and down on the actuator cylinder base frame 5 to adjust the loading angle of the actuator cylinder, wherein the actuator cylinder base frame 5 is fixedly connected to the bottom plate 6 of the test device by bolts.

[0055] In summary, the fatigue test device for the main buffer support joint and its connecting frame can accurately simulate the load boundary conditions, and its structural design is ingenious, adjustable, and easy to install and disassemble. It meets the fatigue test requirements of the test piece (including the main buffer support joint and its connecting frame) under synchronous loading, so that the fatigue test that previously needed to be divided into two tests for separate assessment can now be carried out on this test device to achieve synchronous assessment of its fatigue characteristics, which is used to determine the fatigue life and weak points of the test piece. This test device can effectively reduce the test cost while shortening the test cycle, and has good economy. In actual test verification, the test device has stable operation and the total test error can be controlled within 3%.

[0056] In other embodiments of the present application, a test method is provided, comprising the following steps:

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

[0058] Step 2: Place the test piece's pressure plates 2-4 against the upper curved surface of the test piece, and use 10 pairs of bolts and nuts to perform preliminary positioning of the test piece and restrict its planar motion;

[0059] Step 3: Use the matching left multi-threaded hole bearing block 2-1, tightening bolt 2-2 and gasket 2-3 to further tighten the left side of the test piece pressure plate. Then use a similar method to tighten the right side of the test piece pressure plate and tighten the nut 2-6 again.

[0060] Step 4: Use the load-applying connector to connect the main lifting and buffering support connector and the force sensor in the test piece, and tighten them with lock nuts 3-5.

[0061] Step 5: Connect the bottom of the actuator cylinder to the load angle adjustment assembly 4, and connect the load angle adjustment assembly 4 to the actuator support frame 5. Use the inclinometer to move the loading angle adjustment mechanism up and down until the loading angle requirement is reached;

[0062] Step 6: After the above test piece and test device are assembled, fatigue load is applied starting from the first level load, and the load is increased step by step according to a certain proportion;

[0063] Step 7: During the test, the test piece must be regularly checked for cracks or damage. Multiple test pieces have been used to verify that the connection frame is the first to crack or damage. The number of fatigue cycles resulting from the crack or damage is recorded.

[0064] Step 8: After cracks or damage occur in the connection frame, continue to complete the test under the fatigue load of the current level, and then upgrade the load to continue to assess the fatigue performance of the main buffer support joint until the design requirements are met or the joint cracks or damage occurs, terminate the test and record the number of fatigue cycles.

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

Claims

1. A fatigue test device for synchronously assessing a buffer strut joint and a frame, characterized in that, The device includes: A bottom plate; A support member, arranged on the bottom plate, for installing and supporting a test piece, the test piece including a main take-off buffer strut joint and its connecting frame; An actuating cylinder support frame, arranged on the bottom plate; A load loading angle adjustment assembly, connected to the actuating cylinder support frame; An actuating cylinder and a force sensor, with one end connected to the test piece and the other end connected to the load loading angle adjustment assembly; Wherein, a load is applied through the actuating cylinder, and the force sensor is used for monitoring to achieve fatigue load loading on the main take-off buffer strut joint and its connecting frame, and through this set of fatigue test device, synchronous assessment of the main take-off buffer strut joint and its connecting frame is achieved.

2. The device according to claim 1, wherein The device further includes: A pressing plate assembly for pressing the test piece.

3. The device according to claim 2, characterized in that, The pressing plate assembly further includes: A pressing plate, the lower surface of the pressing plate fits the curved surface of the frame, the area of the pressing plate near the joint is made into a thin plate to achieve true force transmission to the frame, an opening is provided in the middle of the thin plate, the joint extends out from the opening, and the pressing plate preliminarily positions the test piece through bolts and nuts and restricts its planar movement.

4. The device according to claim 3, characterized in that, The pressing plate assembly further includes: Multi-threaded hole bearing blocks, arranged on both sides of the pressing plate, and the multi-threaded hole bearing blocks further press the pressing plate through pressing bolts.

5. The device according to claim 1, characterized in that, The actuating cylinder support frame includes: Columns, arranged on the bottom plate, for installing the load loading angle adjustment assembly.

6. The device according to claim 5, characterized in that, The load loading angle adjustment assembly includes: An adjustment base, including a rectangular plate and a connecting part arranged on the rectangular plate, the connecting part is connected to the bottom of the actuating cylinder; A base pressing plate, connected to the rectangular plate through bolts and nuts and clamped on the column.

7. The device according to claim 5, characterized in that, The load loading angle adjustment assembly can move up and down along the column.

8. A fatigue test method for synchronously assessing a buffer strut joint and a frame, characterized in that, The method includes: Step 1: First, fixedly connect the test piece to the left test piece support member, and then connect it to the right test piece support member; Step 2: Place the test piece pressing plate in fit with the upper curved surface of the test piece, and preliminarily position the test piece through bolts and nuts and restrict its planar movement; Step 3: Use the supporting left multi-threaded hole bearing block, pressing bolts and gaskets to further press the left side of the test piece pressing plate, then use a similar method to press the right side of the test piece pressing plate, and tighten the nuts again; Step 4: Use a load loading joint to connect the main take-off buffer strut joint in the test piece and the force sensor, and lock it with a locking nut; Step 5: Connect the bottom of the actuating cylinder to the load loading angle adjustment assembly, and connect the load loading angle adjustment assembly and the actuating cylinder support frame. With the use of an angle gauge, move the load loading angle adjustment assembly up and down until the loading angle requirement is met; Step 6: After the above test piece and test device are assembled, start loading the fatigue load from the first-stage load, and gradually increase the load by a certain proportion step by step; Step 7: During the test, it is necessary to regularly check whether cracks or damages occur in the test piece. After verification by multiple test pieces, cracks or damages are always first generated in the connecting frame during this period, and record the fatigue cycle times when the cracks or damages occur at this time. Step 8: After cracks or damage occur in the connecting box body, continue to complete the test under the fatigue load of this level, and then upgrade the load to continue to assess the fatigue performance of the main landing buffer strut joint until the design requirements are met or cracks and damage occur in the joint. Terminate the test and record the number of fatigue cycles.

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