Fatigue test load design method for central part of suspension type semi-rigid propeller hub

Abstract

The invention belongs to the field of fatigue test design of helicopter rotor systems, and relates to a fatigue test load design method for a suspension type semi-rigid propeller hub central part. The method comprises the following steps: establishing a central part propeller hub central coordinate system and a local coordinate system for each support arm propeller blade butt joint surface; determining central part fatigue test characteristic load calculation input: blade butt joint surface force located in each local coordinate system and hub six force elements located in a central coordinate system; simulating a connection mode of the rotor shaft and the propeller hub by adopting a fake part to obtain a fatigue test product; in each local coordinate system, analyzing the stress of the butt joint surface of the blade, and determining the fatigue test characteristic load of the butt joint surface of the blade according to the stress analysis result, the force of the butt joint surface of the blade and the six force elements of the propeller hub; the fatigue test characteristic load of the blade butt joint surface is converted to the fatigue test characteristic load initial value of the corresponding loading section; and debugging the load of the actuator cylinder according to the fatigue test characteristic load initial value of the loading section.

Description

Technical Field

[0001] The present invention belongs to the field of fatigue test design of helicopter rotor systems, and relates to a fatigue test load design method for a suspended semi-rigid hub central member. Background Art

[0002] As Figure 1 shown, the hub central member is a key component of a helicopter, and plays an important role in transmitting the hub center load to the blades during flight. The suspended semi-rigid hub central member is suspended on an elastic universal joint in the form of bolts, etc., and is connected to the flapping arm through a roller bearing, etc., and the elastic universal joint is connected to the main shaft through a spline.

[0003] The connection mode between the suspended semi-rigid hub central member and the flapping arm can transmit centrifugal force, shear force and bending moment simultaneously. Fatigue test, as an important means for verifying the fatigue performance of the central member, is an effective method for testing the structural design. Summary of the Invention

[0004] Object of the Invention: To propose a fatigue test load design method for a suspended semi-rigid hub central member, which can reflect the characteristics of the central member fatigue test load of this force transmission type and accurately meet the requirements of the fatigue test.

[0005] Technical Solution:

[0006] Provide a fatigue test load design method for a suspended semi-rigid hub central member, including:

[0007] Establish a hub center coordinate system of the central member and a local coordinate system at the docking surface of each blade of the arm;

[0008] Determine the input for calculating the characteristic load of the central member fatigue test: the forces on the blade docking surfaces located in each local coordinate system and the six-force elements of the hub located in the center coordinate system;

[0009] Use a dummy part to simulate the connection mode between the rotor shaft and the hub to obtain a fatigue test product;

[0010] For each local coordinate system, perform a force analysis on the blade docking surface, and determine the fatigue test characteristic load of the blade docking surface according to the force analysis result, the forces on the blade docking surface and the six-force elements of the hub;

[0011] Convert the fatigue test characteristic load of the blade docking surface to the initial value of the fatigue test characteristic load of the corresponding loading profile;

[0012] According to the initial value of the fatigue test characteristic load of the loading profile, adjust the load of the actuator so that the difference from the measured value of the six-force element load at the hub center is within the allowable range.

[0013] Further, the forces on the blade docking surface include the centrifugal force F ci, Wave shear force F bi , Flap shear force F ti , Flap bending moment M bi , Lead-lag bending moment M ti .

[0014] Furthermore, the six force elements of the hub are synthesized into four elements, namely torque C, lift P, rotational shear force T r , Rotational bending moment M f .

[0015] Furthermore, for the i-th strut, the calculation formula for the fatigue test characteristic load of the blade docking surface is:

[0016] F Xi = F ci ;

[0017]

[0018] i is a positive integer;

[0019] In the formula, M bis is the static load of M bi , M tid is the dynamic load of M ti .

[0020] Furthermore, the conversion calculation formula for the initial value of the fatigue test characteristic load of the loading profile is:

[0021] F Xi = F ci ;

[0022]

[0023] H is the distance from the loading profile to the hub center, F Xi , F Yi , F Zi , M Xi , M Yi , and M Zi are the applied forces and bending moments.

[0024] Furthermore, according to the initial value of the fatigue test characteristic load of the loading profile, adjust the actuator load, including:

[0025] Coordinately load according to the initial value of the fatigue test characteristic load of the loading profile, measure Mf, Tr, C, P at the hub center; compare the difference between the measured value and the required value, and gradually adjust the actuator load value according to the law of the six force elements at the hub center, the forces at the blade docking surface and the actuator load, so that the difference between the actuator load value and the measured value of the six force elements at the hub center is within the allowable range.

[0026] Further, the method for converting the fatigue test characteristic load of the blade docking surface to the initial value of the fatigue test characteristic load of the corresponding loading profile is the force translation criterion.

[0027] Beneficial effects:

[0028] In the present invention, the fatigue test load at the blade docking surface of the central member is calculated through the six-force elements of the hub and the forces at the blade docking surface, and then the test load of any loading profile is obtained through the force translation criterion. This method provides an analysis method for the fatigue test design of the central member of the suspended semi-rigid hub, improves the design efficiency, and is of great significance for the fatigue test design of the helicopter rotor system. Description of the drawings

[0029] Figure 1 It is a model diagram of the central member.

[0030] Figure 2 It is a schematic diagram of the coordinate system. Detailed implementation manners

[0031] To make the purpose, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present application. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and should not be construed as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "axial direction", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present invention.

[0033] The steps for designing the fatigue test load of the central member are as follows:

[0034] [1] Establish a coordinate system as Figure 2 shown

[0035] The central member hub center coordinate system OXYZ and the local coordinate system OX i Yi Z i (i = 1 to n), where n is the number of hub arms.

[0036] [2] Determine the input for calculating the characteristic loads of the fatigue test

[0037] Select the forces at the blade butt joint: F ci 、F bi 、F ti 、M bi 、M ti (i = 1 to n) and the six-force elements of the hub: C, P, T r 、M f are the inputs for calculating the characteristic loads of the fatigue test of the semi-rigid hub central component, where F ci is the centrifugal force, F bi is the flapping shear force, F ti is the drag shear force, M bi is the flapping bending moment, M ti is the drag bending moment, C is the torque, P is the lift force, T r is the rotational shear force, M f is the rotational bending moment.

[0038] [3] Test constraints and loading

[0039] Simulate the connection method between the rotor shaft and the hub for constraint and apply loads at the arm ends.

[0040] [4] Calculate the characteristic loads of the fatigue test at the blade butt joint

[0041] The fatigue test is carried out through 5 × n actuators to coordinately apply the loads in the X i 、Y i 、Z i directions, namely the loads F Xi 、F Yi 、F Zi 、M Xi 、M Yi 、and M Zi The relationships between each load and the six-force elements of the hub center are as follows:

[0042] F Xi = F ci

[0043]

[0044] In the formula, M bis is the static load of M bi and M tid is the dynamic load of M ti .

[0045] [5] Calculate the initial values of the characteristic loads of the fatigue test for any loading profile

[0046] The fatigue test load of any section can be calculated according to the force translation criterion.

[0047] [6] Debug the actuator load

[0048] Coordinately load according to the initial value of the fatigue test characteristic load obtained in step [5], and measure Mf, Tr, C, and P at the hub center; compare the measured values with the required values, and gradually adjust the actuator load value according to the laws of the six-force elements at the hub center, the forces on the blade butt joint surface, and the actuator load in step [5] so that the difference between it and the measured value of the six-force element load at the hub center is within the allowable range, meet the test error requirements, and complete the debugging.

[0049] The following combines examples to further illustrate the design method of this specification. For a suspended rigid hub central component (such as Figure 1 ), the steps of the fatigue test load design method are as follows:

[0050] [1] Establish a coordinate system

[0051] Establish the hub center coordinate system OXYZ of the central component and the local coordinate system OX i Y i Z i (i = 1 to 3), and the number of hub arms is 3.

[0052] [2] Determine the input for calculating the fatigue test characteristic load

[0053] Select the forces on the blade butt joint surface: F ci 、F bi 、F ti 、M bi 、M ti (i = 1 to 3) and the six-force elements of the hub: C, P, T r 、M f as the input for calculating the fatigue test characteristic load of the semi-rigid hub central component, where F ci is the centrifugal force, F bi is the flapping shear force, F ti is the drag shear force, M bi is the flapping moment, M ti is the drag moment, C is the torque, P is the lift force, T r is the rotational shear force, M f is the rotational moment.

[0054] [3] Test constraints and loading

[0055] Simulate the connection method between the rotor shaft and the hub for constraint and load at the arm end.

[0056] [4] Calculate the fatigue test characteristic load of the blade butt joint surface

[0057] The fatigue test is carried out through 5×3 = 15 actuators to coordinately apply loads in the X i , Y i , Z i directions of the load F Xi , F Yi , F Zi , M Xi , M Yi , and M Zi loads. The relationship between each load and the six-force elements at the hub center is as follows:

[0058] F Xi = F ci

[0059]

[0060] where M bis is the static load of M bi , and M tid is the dynamic load of M ti .

[0061] [5] Calculation of the initial value of the characteristic load for the fatigue test of the loading profile

[0062] Assume that the distance from the loading profile to the hub center is 200 mm. The fatigue test load of the loading profile can be deduced according to the force translation criterion.

[0063] F Xi = F ci

[0064]

[0065]

[0066] where M bis is the static load of M bi , and M tid is the dynamic load of M ti .

[0067] [6] Debugging the actuator load

[0068] Coordinately apply the initial value of the characteristic load for the fatigue test obtained in step [5], measure Mf, Tr, C, P at the hub center; compare the difference between the measured value and the required value, and gradually adjust the actuator load value according to the law of the six-force elements at the hub center, the forces on the blade docking surface and the actuator load in step [5] so that the difference between it and the measured value of the six-force element load at the hub center is within the allowable range and meets the test error requirements to complete the debugging.

[0069] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure. The specification and examples are only to be considered exemplary, and the true scope and spirit of the present disclosure are pointed out by the following claims.

[0070] It should be understood that the present disclosure is not limited to the exact structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present disclosure is only limited by the appended claims.

Claims

1. A fatigue test load design method for a central member of a suspended semi-rigid hub, characterized in that Including: Establish the central component hub center coordinate system and the local coordinate system at the butting surface of each support arm blade; Determine the input for calculating the characteristic load of the central component fatigue test: the blade butting surface forces located in each local coordinate system and the hub six-force elements located in the center coordinate system; Use a dummy component to simulate the connection method between the rotor shaft and the hub to obtain the fatigue test product; For each local coordinate system, conduct a force analysis on the blade butting surface, and determine the characteristic load of the blade butting surface fatigue test based on the force analysis results, the blade butting surface forces, and the hub six-force elements; Convert the characteristic load of the blade butting surface fatigue test to the initial value of the characteristic load of the corresponding loading profile; According to the initial value of the characteristic load of the loading profile, adjust the actuator load so that the difference between it and the measured value of the hub center six-force element load is within the allowable range.

2. The method according to claim 1, characterized in that, The blade docking surface forces include the centrifugal force F ci , the flapping shear force F bi , the drag shear force F ti , the flapping moment M bi , the drag moment M ti .

3. The method according to claim 2, wherein The six force elements of the hub are synthesized into four elements, namely torque C, lift P, rotational shear force T r , and rotational bending moment M f .

4. The method according to claim 3, characterized in that, For the i-th support arm, the calculation formula for the characteristic load of the blade butting surface fatigue test is: F Xi = F ci ; i is a positive integer; Where M bis is the static load of M bi , and M tid is the dynamic load of M ti .

5. The method according to claim 4, characterized in that, The conversion calculation formula for the initial value of the characteristic load of the loading profile is: F Xi = F ci ; H is the distance of the loading profile from the hub center, F Xi 、F Yi 、F Zi 、M Xi 、M Yi 、and M Zi are the applied forces and bending moments.

6. The method according to claim 5, characterized in that According to the initial value of the characteristic load of the loading profile, adjust the actuator load, including: Coordinately load according to the initial value of the characteristic load of the loading profile, measure Mf, Tr, C, P at the hub center; compare the difference between the measured value and the required value, and gradually adjust the actuator load value according to the law of the hub center six-force elements, the blade butting surface forces, and the actuator load so that the difference between it and the measured value of the hub center six-force element load is within the allowable range.

7. The method according to claim 6, wherein The method used to convert the characteristic load of the blade butting surface fatigue test to the initial value of the characteristic load of the corresponding loading profile is the force translation criterion.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-7.

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