A helicopter dynamic fatigue test device and test method

Abstract

The present application belongs to the technical field of helicopter fatigue test, and particularly relates to a helicopter moving ring fatigue test device and a test method. The device is composed as follows: a lower bottom surface of a stationary ring dummy mounting support is mounted on a fixed platform, and a stationary ring dummy is mounted above the stationary ring dummy mounting support; an outer cylindrical surface of the stationary ring dummy is mounted through interference fit with an inner cylindrical surface of a helicopter moving ring large bearing; a cylinder base is mounted on the fixed platform and is uniformly distributed around the stationary ring dummy mounting support, a fixed end of the cylinder is connected with the cylinder base, a loading end of the cylinder is connected with a variable torque rod loading connector, the other end of the variable torque rod loading connector is fixed to a helicopter moving ring support arm; a torsion arm loading yoke assembly is connected with a helicopter moving ring 2# torsion arm, a torsion prevention yoke assembly is connected with a helicopter moving ring 1# torsion arm at one end and connected with a torsion prevention rod assembly at the other end; the torsion arm loading yoke assembly and the torsion prevention rod assembly are fixed with a ground rail through a torsion arm loading support.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter fatigue testing, and in particular relates to a helicopter dynamic ring fatigue testing device and a testing method. Background Art

[0002] With the rapid development of my country's economy, fueled by its robust economic strength, the development of domestic helicopter models has seen explosive growth, with numerous new models and configurations emerging. This has indirectly driven the further development of helicopter fatigue testing technology. The helicopter rotor ring is a key moving component in the main rotor system. As it rotates with the main rotor, it primarily bears alternating loads from the pitch lever and torque arm. Consequently, the rotor ring is susceptible to fatigue damage, leading to failure of the main rotor system and directly impacting helicopter flight safety. Therefore, fatigue testing of the rotor ring during the helicopter development phase is crucial to simulate the stress conditions experienced during flight and determine its fatigue performance and weak points. Given the current lack of a reliable domestic reference method and related equipment for fatigue testing of the rotor ring, there is an urgent need to design a loading device for fatigue testing of the rotor ring and develop corresponding fatigue testing methods to guide this testing. Summary of the Invention

[0003] Purpose of the invention: The present invention designs a helicopter dynamic ring fatigue loading test device and provides a helicopter dynamic ring fatigue method. By designing a special loading test device, adopting a scientific and feasible test method, and applying a test load with an actuator, the actual installation boundary conditions and load characteristics of the helicopter dynamic ring are simulated, providing a real and accurate helicopter dynamic ring fatigue test assessment environment, thereby obtaining accurate fatigue risk locations and failure modes of the helicopter dynamic ring, and providing a test basis for determining its service life.

[0004] The present invention relates to a fatigue test method and loading device for a helicopter dynamic ring, including a fatigue test for a helicopter dynamic ring support arm and a fatigue test for a connecting ear between a helicopter dynamic ring and a torque arm. This design scheme and test method, which can realize fatigue test loading for a helicopter dynamic ring support arm and fatigue test loading for a connecting ear between a helicopter dynamic ring and a torque arm, provides a reference for the current design and improvement of the helicopter dynamic ring structure, as well as for life evaluation.

[0005] Technical Solution

[0006] A helicopter dynamic ring fatigue test device includes: a stationary ring dummy, a stationary ring dummy mounting bracket, a fixed platform, an actuator cylinder base, a variable pitch pull rod loading joint, a torque arm loading fork ear assembly, an anti-torsion fork ear assembly, an anti-torsion rod assembly and a torque arm loading bracket;

[0007] The lower surface of the fixed ring dummy mounting support is mounted on the fixed platform, and the fixed ring dummy is mounted above the fixed ring dummy mounting support;

[0008] The outer cylindrical surface of the stationary ring dummy and the inner cylindrical surface of the helicopter's dynamic ring large bearing are installed through interference fit;

[0009] The actuator base is installed on a fixed platform and evenly distributed around the fixed ring dummy mounting bracket. The fixed end of the actuator is connected to the actuator base, and the loading end of the actuator is connected to the torque converter rod loading joint. The other end of the torque converter rod loading joint is fixed to the helicopter dynamic ring support arm.

[0010] The torque arm loading fork ear assembly is connected to the helicopter dynamic ring 2# torque arm, one end of the anti-torsion fork ear assembly is connected to the helicopter dynamic ring 1# torque arm, and the other end is connected to the anti-torsion rod assembly;

[0011] The torque arm loading fork ear assembly and the anti-torsion bar assembly are fixed to the ground rail through the torque arm loading support.

[0012] Furthermore, a force sensor is installed between the variable pitch tie rod loading joint and the loading end of the actuator cylinder.

[0013] Furthermore, both ends of the anti-twist rod assembly are reverse-threaded for adjusting the length.

[0014] Furthermore, the torque arm loading fork ear assembly and the anti-torsion fork ear assembly are symmetrically installed about the center of the dynamic ring.

[0015] A method for fatigue testing of a helicopter dynamic ring is implemented based on the above device and comprises the following steps:

[0016] Step 1: Debug the test device;

[0017] Step 2: Determine the initial dynamic ring arm load F 1i , i = 1, n, n is the number of east ring arms, and the initial dynamic ring torque arm load F2;

[0018] Step 3: Load according to the determined test load;

[0019] Step 4: Regularly check and record the test load, number of test cycles and test damage during the loading process;

[0020] Step 5: When detectable cracks appear on the helicopter dynamic ring or the set number of cycles is reached, the test is terminated. Otherwise, the load is increased based on the initial dynamic ring support arm load and the initial dynamic ring torque arm load, and the test returns to step 3.

[0021] Furthermore, the initial dynamic ring arm load calculation formula is as follows:

[0022] F 1i =Fs1+F d1*cos[wt-2π / 5(i-1)]

[0023] Among them, F s1 is the static load of the arm, F d1 is the dynamic load of the arm, w is the angular velocity, t is the time, and i is the arm number.

[0024] Furthermore, the calculation formula of the initial dynamic ring torque arm load F2 is as follows:

[0025] F2=F s2 +F d2 *cos(wt)

[0026] Among them, F s2 is the static load of the torque arm, F d2 is the dynamic load of the torque arm, w is the angular velocity, and t is the time.

[0027] Furthermore, in step 1, the test device debugging process is as follows:

[0028] Start the test device, preheat for 1 minute, check the communication status, and ensure that the test device is working properly;

[0029] Adjust the polarity of the force sensor, define the pulling direction as positive and the pressing direction as negative, and the positive direction of the load F actually applied by the actuator is the same as the test load F. 1i Or the positive direction defined by F2 is consistent;

[0030] Generally, 10%, 40%, 60%, 90% and 100% of F are applied in 5 levels. 1i Or F2 load, adjust the proportional, integral and differential parameters of the control channel to ensure that the feedback signal can quickly follow the command signal and eliminate hysteresis as much as possible;

[0031] At the same time, set upper and lower limit protection and load error protection.

[0032] Furthermore, in step 5, the second level load F is increased. B Compared with the first level load F before the increase A With the following relationship:

[0033] F B / F A =[F s1 +(1+20%)*F d1 *cos(wt)] / [F s1 +F d1 *cos(wt)] or F B / F A =[F s2 +(1+20%)

[0034] *F d2*cos(wt)] / [F s2 +F d2 *cos(wt)].

[0035] In summary, the beneficial effects of the present invention are as follows:

[0036] The helicopter dynamic ring fatigue loading test device designed by the present invention can simultaneously meet the requirements of coordinated loading of each dynamic ring arm and fatigue loading of the connection between the dynamic ring and the torque arm, and accurately simulates the installation boundary conditions and load characteristics of the helicopter dynamic ring. This effectively solves the problem of developing a helicopter dynamic ring fatigue test device from scratch in China, fills the gap in domestic helicopter fatigue strength testing technology, and further improves the level of helicopter strength testing in my country. The helicopter dynamic ring fatigue test method involved in the present invention is reasonable and correct, and can accurately reproduce the loading process of the helicopter dynamic ring in flight. Tests have shown that the loading device and test method can accurately simulate the installation boundary conditions and load characteristics of the helicopter dynamic ring during the helicopter dynamic ring fatigue test, providing a realistic and accurate assessment environment for the helicopter dynamic ring, achieving coordinated loading of each dynamic ring arm and fatigue loading of the connection lug between the dynamic ring and the torque arm, with a high degree of overlap between load feedback data and command data. When using this test device to conduct helicopter dynamic ring fatigue tests, the total test error can be controlled within 3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the load on the helicopter's dynamic ring;

[0038] Figure 2 This is a schematic diagram of the structure of a helicopter dynamic ring fatigue test device;

[0039] Figure 3 This is a flow chart of a helicopter dynamic ring fatigue test method. DETAILED DESCRIPTION

[0040] For the fatigue test of helicopter dynamic ring, a test device is provided that can simultaneously meet the coordinated loading of each arm of the dynamic ring and the fatigue loading of the ear piece connecting the dynamic ring and the torque arm. The structural design, size and fitting tolerance of the device simulate the installation boundary conditions of the helicopter dynamic ring. At the same time, the variable pitch pull rod force and torque arm load are applied to the helicopter dynamic ring through the tooling dummy, simulating the stress state of the helicopter dynamic ring on the helicopter, and can accurately reproduce the loading process of the helicopter dynamic ring in flight.

[0041] The technical solution of the present invention: The helicopter dynamic ring fatigue loading device consists of a stationary ring dummy 1, a stationary ring dummy mounting support 2, a fixed platform 3, an actuator base 4, a variable pitch pull rod loading joint 5, a torque arm loading fork ear assembly 6, an anti-torsion fork ear assembly 7, an anti-torsion rod assembly 8 and a torque arm loading support 9.

[0042] The outer cylindrical surface of the stationary ring dummy 1 is fixed to the inner cylindrical surface of the large bearing of the helicopter dynamic ring through interference fit. The stationary ring dummy 1 together with the helicopter dynamic ring is installed on the mounting plane of the stationary ring dummy mounting support 2 through the bolt holes on the stationary ring dummy 1 and fixed. The lower bottom surface of the stationary ring dummy mounting support 2 is surface-to-surface with the upper plane of the fixed platform 3 and fixed with standard bolts; the actuator base 4 is evenly distributed and fixed on the upper plane of the fixed platform 3, and the fixed end of the actuator is connected to the actuator base. The loading end of the actuator is connected to the embedded threaded hole of the pitch rod loading joint 5, and the other end of the pitch rod loading joint 5 is fixed on the helicopter dynamic ring support arm to realize the loading of the helicopter dynamic ring pitch rod force; the torque arm loading fork ear assembly 6 is installed at the helicopter dynamic ring 2# torque arm connection, and the anti-torsion fork ear assembly 7 is installed at the helicopter dynamic ring 1# torque arm connection and connected to the anti-torsion bar assembly 8. Finally, the torque arm loading fork ear assembly 6 and the anti-torsion bar assembly 8 are both fixed to the ground rail through the torque arm loading support 9.

[0043] (1) Test device: The device of the invention is designed with a fixed ring dummy, a fixed ring dummy mounting bracket, a fixed platform, an actuator base, a variable pitch pull rod loading joint, a torque arm loading fork ear assembly, a torque arm loading bracket, an anti-torsion fork ear assembly and an anti-torsion rod assembly, and an actuator is used to apply the test load. The device can realize the phase-coordinated loading of the loads of each arm of the helicopter dynamic ring, that is, each arm can be loaded in the same phase or in different phases, meeting the assessment requirements of the helicopter dynamic ring under different working conditions. At the same time, by designing the fixed ring dummy and other tooling, the actual boundary conditions and loading conditions of the helicopter dynamic ring installation are simulated, providing a real and accurate helicopter dynamic ring fatigue test assessment environment, so that the accurate fatigue risk parts and failure modes of the helicopter dynamic ring can be obtained, providing a test basis for determining its service life. The main features of the device are as follows: (1) The variable pitch tie rod load loading device (consisting of a variable pitch tie rod loading joint, a force sensor, an actuator, and an actuator base) is designed to be in the same direction as the load, so that the load is stable in the tensile direction; at the same time, each set of variable pitch tie rod load loading devices is independent of each other, which can achieve phase-coordinated loading on the one hand and facilitate the adjustment and calibration of the installation angle on the other hand. (2) The anti-torsion bar assembly adopts a reverse thread design at both ends, which can adjust the length of the anti-torsion bar without disassembly, thereby achieving the adjustment of the torque arm loading angle, reducing the disassembly and assembly time and labor costs. (3) The torque arm loading device (consisting of a torque arm loading fork ear assembly, a force sensor, an actuator, and a torque arm loading support) and the anti-torsion device (consisting of an anti-torsion fork ear assembly, an anti-torsion bar assembly, a force sensor, and a torque arm loading support) are designed to be centrally symmetrical. The torque generated during loading is transmitted to the fixed platform through the fixed ring dummy mounting support, achieving internal force balance in the system, improving the stability of the test bench, and reducing the test load fluctuation, thereby improving the test efficiency.

[0044] In summary, the test device can accurately simulate the boundary conditions and load conditions of the helicopter dynamic ring during flight, and at the same time meet the fatigue test requirements of the helicopter dynamic ring support arm and the fatigue test of the ear piece connecting the dynamic ring and the torque arm. It has a clever structural design, stable and reliable working performance, good adjustability, and is easy to install and disassemble. The total test error can be controlled within 3%, which can fully verify the fatigue performance of the helicopter dynamic ring, thereby providing a basis for determining the service life and weak points of the helicopter dynamic ring.

[0045] (2) Test methods:

[0046] The helicopter dynamic ring is subjected to complex fatigue loads under different flight conditions such as takeoff, landing and hovering. Once fatigue damage occurs, the helicopter rotor system control will fail and the helicopter will crash. For flight safety, fatigue tests need to be carried out on the helicopter dynamic ring in a ground state to simulate the fatigue loads that the helicopter dynamic ring is subjected to under flight conditions, so as to determine the fatigue performance and weak points of the helicopter dynamic ring and provide a basis for determining its service life. In view of the current lack of a fatigue life test method for helicopter dynamic rings, the present invention provides a fatigue method for helicopter dynamic rings, which mainly includes: test installation and fixing method, test load determination, test implementation steps and test installation, loading and inspection requirements, etc. The basic test process is shown in Figure 3 The helicopter dynamic ring fatigue method includes two parts: dynamic ring support arm fatigue test loading and torque arm connection ear fatigue test loading.

[0047] (1) In the fatigue test of helicopter dynamic ring, the fatigue test of the dynamic ring support arm is generally carried out first, and then the fatigue test of the torque arm connection ear is carried out.

[0048] (2) Installation and fixing method of helicopter dynamic ring fatigue test Figure 2 shown.

[0049] (3) Fatigue test load of helicopter dynamic ring. The fatigue test load of helicopter dynamic ring is usually given by the test task book. The fatigue test load given in the test task book is obtained by the load-stress relationship determined by the finite element analysis of the helicopter dynamic ring and calculated based on the load spectrum of the helicopter dynamic ring and the average SN curve of the material.

[0050] The load direction of the helicopter dynamic ring support arm is perpendicular to the dynamic ring rotation surface. The load is transmitted by the pitch rod end joint bearing and acts on the dynamic ring support arm through the connecting bolt. The corresponding pitch rod tension is positive. The load on each arm of the helicopter dynamic ring has a phase relationship. The specific phase needs to be determined according to the structural distribution of the helicopter dynamic ring. Generally, the load form of the helicopter dynamic ring with 5 arms is as follows: F 1i =Fs1+F d1 *cos[wt-2π / 5(i-1)],F s1 is the static load, F d1is the dynamic load, w is the angular velocity, t is the time, and i is the arm number.

[0051] The torque arm connecting ear of the helicopter dynamic ring bears the torque arm load, which is tangential to the rotating surface of the dynamic ring. The load is transmitted by the torque arm and acts on the dynamic ring ear through the connecting bolt. The positive direction of the load is opposite to the rotation direction of the helicopter main rotor. The load form of the torque arm connecting ear of the helicopter dynamic ring is as follows: F2=F s2 +F d2 *cos(wt), F s2 is the static load, F d2 is the dynamic load, w is the angular velocity, and t is the time.

[0052] (4) Test implementation steps:

[0053] a) Test installation, according to Figure 2 The test installation is completed as shown;

[0054] b) Test debugging: Start the coordinated loading control system, preheat for 1 minute, check the software communication status, and ensure that the test equipment is working properly; adjust the polarity of the force sensor, define the pulling direction as positive and the pressing direction as negative, and ensure that the positive direction of the actual load F applied by the actuator is consistent with the test load F. 1i Or the positive direction defined by F2; generally, 10%, 40%, 60%, 90% and 100% of F are applied in 5 levels respectively. 1i Or F2 load, adjust the proportional, integral and differential parameters of the control channel to ensure that the feedback signal can quickly follow the command signal and eliminate the hysteresis phenomenon as much as possible; after the previous step is completed, load 100% test load F 1i Or F2 test, at the same time set the upper and lower limit protection to prevent the load F applied by the actuator from exceeding the bearing range of the helicopter dynamic ring and causing abnormal damage; set the load error protection to ensure that the actual loading load F is consistent with the test load F 1i Or the F2 ratio does not exceed 2.5%, that is, the loading error does not exceed 2.5%. This involves error allocation. The error allocation scheme of this test method is set as follows: During the test, the load measurement sensor error is controlled within 0.5%, and the control system error is controlled within 0.5%. That is, the error of the load measurement sensor and control system selected for this test does not exceed 0.5%. The loading error is controlled within 2.5%. The total test error is calculated as the root mean square of each error to ensure that the total test error does not exceed 3%.

[0055] c) Conduct the test: The test will be started after debugging and no problems are found. In the fatigue test of the helicopter dynamic ring, the test load is applied to the helicopter dynamic ring through the telescopic movement of the actuator. When conducting the fatigue test of the helicopter dynamic ring arm, the load is transmitted to each arm of the helicopter dynamic ring through the variable pitch pull rod loading joint. The load direction is perpendicular to the rotation surface of the helicopter dynamic ring. At the same time, the torque arm is used to load the anti-torsion component at the connection of the helicopter dynamic ring 1# torque arm to constrain the circumferential displacement of the helicopter dynamic ring and measure the constraint force. When conducting the fatigue test of the connection between the dynamic ring and the torque arm, the test load is applied to the connection of the helicopter dynamic ring 2# torque arm through the torque arm loading component. At the same time, the torque arm is used to load the anti-torsion component at the connection of the helicopter dynamic ring 1# torque arm to constrain the circumferential displacement of the helicopter dynamic ring and measure the constraint force. The arms of the helicopter dynamic ring are in an unconstrained state.

[0056] (5) Test installation, loading and inspection requirements

[0057] a. The installation of the helicopter dynamic ring shall be carried out according to the requirements of the test device drawing, and the required tightening torque shall be applied to the connecting bolts of the helicopter dynamic ring;

[0058] b. During the fatigue test of helicopter dynamic ring, the load should be monitored, including but not limited to setting load error and limit protection;

[0059] c. Upgrade and adjust the load of helicopter dynamic ring fatigue test. The dynamic load F can be adjusted step by step during the test. d1 or F d2 Generally, the adjustment ratio is 20% of the first level dynamic load, that is, the second level load F B / First level load F A For: F B / F A =[F s1 +(1+20%)*F d1 *cos(wt)] / [F s1 +F d1 *cos(wt)] or F B / F A =[F s2 +(1+20%)*F d2 *cos(wt)] / [F s2 +F d2 *cos(wt)], Generally, if the helicopter dynamic ring is not damaged after 300,000 to 500,000 test load cycles, the fatigue test dynamic load can be increased until it is damaged or the assessment purpose is achieved. The first-level test load of the latter part can be adjusted according to the test results of the previous part;

[0060] d. During the fatigue test of helicopter dynamic ring, it is necessary to regularly check and record the test load, number of test cycles, test damage, etc. (generally no more than every 100,000 cycles);

[0061] e. Test termination conditions: the test can be terminated if one of the following conditions occurs: visually detectable cracks appear on the helicopter dynamic ring (the crack length is generally greater than 2mm) or the test purpose is achieved;

[0062] f Principles for determining test validity: After the test, visually inspect the dynamic ring. If there is no crack, the number of test cycles completed is valid. If visually visible cracks appear on the dynamic ring, review the relevant test data. If there is a significant change in load, the number of cycles when the load changes significantly is used as the valid number of test cycles.

Claims

1. A helicopter dynamic ring fatigue test device, characterized by: The device includes: Immovable ring dummy, immovable ring dummy mounting bracket, fixed platform, actuator base, variable pitch tie rod loading joint, torque arm loading fork ear assembly, anti-torsion fork ear assembly, anti-torsion bar assembly and torque arm loading bracket; The lower surface of the fixed ring dummy mounting support is mounted on the fixed platform, and the fixed ring dummy is mounted above the fixed ring dummy mounting support; The outer cylindrical surface of the stationary ring dummy and the inner cylindrical surface of the helicopter's dynamic ring large bearing are installed through interference fit; The actuator base is installed on a fixed platform and evenly distributed around the fixed ring dummy mounting bracket. The fixed end of the actuator is connected to the actuator base, and the loading end of the actuator is connected to the torque converter rod loading joint. The other end of the torque converter rod loading joint is fixed to the helicopter dynamic ring support arm. The torque arm loading fork ear assembly is connected to the helicopter dynamic ring 2# torque arm, one end of the anti-torsion fork ear assembly is connected to the helicopter dynamic ring 1# torque arm, and the other end is connected to the anti-torsion rod assembly; The torque arm loading fork ear assembly and the anti-torsion bar assembly are fixed to the ground rail through the torque arm loading support.

2. The device according to claim 1, characterized in that: A force sensor is installed between the variable pitch rod loading joint and the loading end of the actuator.

3. The device according to claim 2, characterized in that: The anti-twist bar assembly is reverse threaded at both ends for adjusting the length.

4. The device according to claim 3, characterized in that: The torque arm loading fork ear assembly and the anti-torsion fork ear assembly are symmetrically installed about the center of the dynamic ring.

5. A method for fatigue testing of a helicopter dynamic ring, said method being implemented based on any of the aforementioned devices, characterized in that: The following steps are involved: Step 1: Debug the test device; Step 2: Determine the initial dynamic ring arm load F 1i , i = 1, n, n is the number of east ring arms, and the initial dynamic ring torque arm load F2; Step 3: Load according to the determined test load; Step 4: Regularly check and record the test load, number of test cycles and test damage during the loading process; Step 5: When detectable cracks appear on the helicopter dynamic ring or the set number of cycles is reached, the test is terminated. Otherwise, the load is increased based on the initial dynamic ring support arm load and the initial dynamic ring torque arm load, and the test returns to step 3.

6. The method according to claim 5, characterized in that: The calculation formula for the initial dynamic ring arm load is as follows: F 1i =Fs1+F d1 *cos[wt-2π / 5(i-1)] Among them, F s1 is the static load of the arm, F d1 is the dynamic load of the arm, w is the angular velocity, t is the time, and i is the arm number.

7. The method according to claim 6, characterized in that: The calculation formula for the initial dynamic ring torque arm load F2 is as follows: F2=F s2 +F d2 *cos(wt) Among them, F s2 is the static load of the torque arm, F d2 is the dynamic load of the torque arm, w is the angular velocity, and t is the time.

8. The method according to claim 7, wherein: In step 1, the test device debugging process is as follows: Start the test device, preheat for 1 minute, check the communication status, and ensure that the test device is working properly; Adjust the polarity of the force sensor, define the pulling direction as positive and the pressing direction as negative, and the positive direction of the load F actually applied by the actuator is the same as the test load F. 1i Or the positive direction defined by F2 is consistent; Generally, 10%, 40%, 60%, 90% and 100% of F are applied in 5 levels. 1i Or F2 load, adjust the proportional, integral and differential parameters of the control channel to ensure that the feedback signal can quickly follow the command signal and eliminate hysteresis as much as possible; At the same time, set upper and lower limit protection and load error protection.

9. The method according to claim 8, characterized in that: In step 5, the second level load F is increased B Compared with the first level load F before the increase A With the following relationship: F B / F A =[F s1 +(1 + 20%)*F d1 *cos(wt)] / [F s1 +F d1 *cos(wt)] or F B / F A =[F s2 +(1 + 20%) *F d2 *cos(wt)] / [F s2 +F d2 *cos(wt)]。

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