Method for designing strength of up-down split type tiltable propeller hub

Abstract

The invention relates to the field of strength design of helicopter parts, in particular to a strength design method of an up-down split type tiltable propeller hub. The method comprises the following steps: analyzing a force transmission route according to an up-down split type tiltable propeller hub structure and a load, and determining a dangerous part; determining a characteristic load set of all dangerous parts according to the loads of the upper and lower split type tiltable propeller hub and the dangerous parts; according to the up-and-down split type tiltable propeller hub structure, a finite element simulation or engineering method is adopted, and the load / bending moment distribution relation in the upper and lift directions of the upper propeller hub, the lower propeller hub and the connecting structure of the upper propeller hub and the lower propeller hub is determined; 4, according to the up-down split type tiltable propeller hub structure and the variable total pitch and variable rotating speed control process, the load action range of the variable pitch rocker arm structure is determined; and according to the results from the step 1 to the step 4, carrying out finite element simulation on the upper and lower split type tiltable propeller hub structure, and carrying out stress calculation.

Description

Technical Field

[0001] The invention relates to the field of helicopter component strength design, and in particular to a strength design method for an upper and lower split tiltable hub. Background Art

[0002] With the rapid development of the new energy industry, battery and motor technology have made continuous breakthroughs, and electric-driven vertical take-off and landing aircraft have gradually acquired military and civilian value and broad market prospects. The electric-driven tilt-rotor aircraft is a new type of electric-driven vertical take-off and landing aircraft that can achieve vertical take-off and landing while increasing flight speed, and has high economic efficiency and technological innovation.

[0003] like Figure 1 As shown in the figure, the upper and lower split tilting hub is an important component of the electric-driven tilt-rotor aircraft and an important structure for realizing the variable pitch and variable speed control of the electric-driven tilt-rotor aircraft. Compared with the traditional helicopter hub forms such as the ball flexible hub and the rigid connection hub, the upper and lower split tilting hub does not contain structures such as splines and cone rings, and has completely different characteristics in terms of torsional moment transmission, hub center moment transmission, and lift direction load / moment transmission. Summary of the invention

[0004] The purpose of the present invention is to provide a strength design method for a split-up and split-up tilting hub, including force transmission route analysis, selection of dangerous parts, selection of characteristic loads, load distribution in the lift direction, determination of the control range, stress calculation, static strength analysis, fatigue strength analysis, etc. First, according to the structure and load of the split-up and split-up tilting hub, the force transmission route analysis is carried out, the dangerous parts and the corresponding characteristic loads are determined, and the stress calculation is carried out after improving the details such as load distribution, and according to the stress calculation results, the static strength analysis and fatigue strength analysis are completed to complete the strength design.

[0005] Technical solution:

[0006] A strength design method for an upper and lower split tiltable propeller hub is provided, comprising:

[0007] Step 1: Analyze the force transmission route and identify dangerous parts based on the upper and lower split tilting hub structure and load;

[0008] Step 2: Determine the characteristic load set of all dangerous parts according to the loads and dangerous parts of the upper and lower split tiltable hub;

[0009] Step 3: According to the upper and lower split tiltable hub structure, use finite element simulation or engineering methods to determine the load / bending moment distribution relationship in the lift direction on the upper and lower hubs and their connection structures;

[0010] Step 4: Determine the load action range of the pitch rocker arm structure according to the upper and lower split tilting hub structure and the variable pitch and variable speed operation process;

[0011] Step 5: Based on the results of steps 1 to 4, carry out finite element simulation of the upper and lower split tiltable hub structure and perform stress calculation.

[0012] Furthermore, the method further comprises:

[0013] Step six: Based on the results of steps two and five, conduct static strength analysis and fatigue strength analysis of the upper and lower split tiltable hub structure to complete the strength design.

[0014] Furthermore, the dangerous parts include static strength dangerous parts and fatigue dangerous parts. According to the upper and lower split tilting hub structure and load, the force transmission route analysis is carried out and the dangerous parts are determined, including:

[0015] According to the analysis of the force transmission route, it can be determined that the load and bending moment transmitted by the upper and lower hubs to the blades, and the control load transmitted by the pitch rocker arm and the control structure all show the characteristics of changing with time, which are fatigue loads. Therefore, it is determined that the upper and lower hubs, the pitch rocker arm, the control structure and the related connection structures are all static strength and fatigue risk areas.

[0016] Furthermore, according to the loads and dangerous parts of the upper and lower split tiltable hub, the characteristic load set of all dangerous parts is determined, including:

[0017] According to the loads and dangerous parts of the upper and lower split tiltable hub, the characteristic loads of the upper and lower hubs are determined to include blade centrifugal force, blade shear force and bending moment; the characteristic loads of the variable pitch rocker arm and the control structure are taken as the control loads; and the loads related to the connected structure are determined as the characteristic loads of the connecting structure.

[0018] Furthermore, according to the upper and lower split tiltable hub structure, finite element simulation or engineering method is used to determine the load / bending moment distribution relationship in the lift direction on the upper and lower hubs and their connection structures, including:

[0019] Apply bolt preload according to the design value and fix the upper and lower propeller hubs together with bolts;

[0020] According to the actual contact and connection mode, the upper hub, lower hub, connecting bolts and lift direction bearing are combined for modeling and force transmission analysis. The model structure is simplified without affecting the structural stiffness during modeling. The load / bending moment distribution relationship in the lift direction of the blade is obtained through analysis of the simplified model, that is, the distribution ratio of the upper and lower hub lift.

[0021] Furthermore, the load acting range of the root variable pitch rocker arm structure is 5 to 15 mm.

[0022] Further, according to the results of step 1 to step 4, the finite element simulation of the upper and lower split tiltable hub structure is carried out to perform stress calculation, including:

[0023] Determine all characteristic loads of each component of the upper and lower split tiltable hub and their locations and methods of action, determine the constraint locations and methods, and perform detailed modeling stress analysis of each component as a separate body; when the load / bending moment in the lift direction is applied, apply loads of corresponding distribution proportions to the upper and lower hubs respectively; select the two end points and the middle point of the range of action within the range of action of the variable pitch rocker arm structure load for loading, and analyze the stresses at different action positions of the variable pitch rocker arm structure load; complete the stress calculation.

[0024] Beneficial effects:

[0025] The present invention effectively solves the key links in the strength design process of the upper and lower split tilting hub structure, quantitatively analyzes the characteristic load values ​​of various components of the upper and lower split hub structure through force transmission analysis methods such as combined modeling, and determines the stresses in dangerous parts of static strength and fatigue strength through accurate simulation of the separated bodies of each component, thereby solving the force transmission and load decomposition problems of the upper and lower split tilting hub structure, improving the accuracy of stress analysis, and meeting the needs of engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the upper and lower split tiltable propeller hub;

[0027] Figure 2 This is a schematic diagram of the movement range of the variable pitch rocker arm in the control structure

[0028] Figure 3 This is a schematic diagram of the loading position of the variable pitch rocker arm in the motion range of the control structure.

[0029] 1-upper propeller hub, 2-lower propeller hub, 3-pitch rocker arm, 4-upper and lower propeller hub connecting bolts, 5-control structure. DETAILED DESCRIPTION

[0030] The present invention provides a strength design method for a vertically split tiltable hub, comprising:

[0031] Step 1: According to the structure and load of the upper and lower split tilting hub, carry out force transmission route analysis and determine the dangerous parts / positions, including static strength dangerous parts and fatigue dangerous parts;

[0032] Step 2: According to the loads and dangerous parts of the upper and lower split tilting hub, determine the characteristic loads of the dangerous parts, which generally include load extremes, static loads, dynamic loads, etc.;

[0033] Step 3: According to the upper and lower split tiltable hub structure, use finite element simulation or engineering methods to determine the load / bending moment distribution relationship in the lift direction on the upper and lower hubs and their connection structures;

[0034] Step 4: Determine the load action range of the pitch rocker arm structure according to the upper and lower split tilting hub structure and the variable pitch and variable speed operation process;

[0035] Step 5: Based on the results of steps 1 to 4, carry out finite element simulation of the upper and lower split tilting hub structure and perform stress calculation; for bolts, lugs, etc., stress calculation can be performed using engineering methods as appropriate;

[0036] Step six: Based on the results of steps two and five, conduct static strength analysis and fatigue strength analysis of the upper and lower split tiltable hub structure to complete the strength design.

[0037] The following takes the strength design of a certain type of aircraft upper and lower split tilting hub as an example, and further describes the present invention in detail in conjunction with the accompanying drawings:

[0038] Step 1: The upper and lower split tiltable hub structure of a certain type of aircraft is composed of an upper hub 1, a lower hub 2, a pitch rocker arm 3, a control structure 5 and a related connection structure 4, wherein the upper and lower hubs do not contain structures such as splines and cone rings, such as Figure 1 As shown. The lower hub is fixed to the motor with bolts; the centrifugal force of the blades is transmitted to the upper and lower hubs through the bearings and balanced with each other on the hubs; the blade torque is connected to the pitch rocker arm through the root of the blade and transmitted to the control structure to balance with the control load; the blade shear force and bending moment are transmitted to the hub through the root bearing of the blade, forming the main shaft bending moment, shear force and hub torque. According to the analysis of the force transmission route, the upper and lower hubs transmit the load and bending moment of the blades, and the pitch rocker arm and the control structure transmit the control load. Except for the centrifugal force, the above loads all show the characteristics of changing with time and are typical fatigue loads. Therefore, the upper and lower hubs, pitch rocker arm, control structure and related connection structures are all static strength and fatigue hazardous components / parts;

[0039] Step 2: According to the upper and lower split tiltable hub loads and dangerous parts, the characteristic loads of the upper and lower hubs include blade centrifugal force, blade shear force and bending moment, etc.; the characteristic loads of the variable pitch rocker arm and the control structure are the control loads; the characteristic loads of the connecting structure are related to the connected structure;

[0040] Step 3: The upper and lower propeller shells are fixed together by bolts, and the bolt preload is applied according to the design value. Combined modeling and force transmission analysis are performed on the upper propeller shell, lower propeller shell, connecting bolts, lift direction bearings, etc. according to actual contact and other connection methods; during modeling, the connecting bolts and the upper and lower propeller shells can be bound or frictionally contacted, and the upper and lower propeller shells are in friction contact. Bearings and other components can be appropriately simplified without affecting the structural stiffness. Coupling constraints are used between the simplified bearing parts and the upper and lower propeller shells; according to the analysis results, the lift direction load / bending moment of the blades transmitted by the upper and lower propeller shells are extracted respectively. According to the analysis results, the upper propeller shell transmits 45% of the lift direction load / bending moment, and the lower propeller shell transmits 55% of the lift direction load / bending moment. Step 4: According to the upper and lower split tiltable hub structure and the variable pitch and variable speed control process, motion simulation is performed to obtain a motion range of 5 to 15 mm for the variable pitch rocker arm in the control structure. The contact position at the boundary of the motion range is as follows: Figure 2 As shown;

[0041] Step 5: According to Step 1 and Step 2, determine all characteristic loads of each component and their acting positions and modes, determine the constraint positions and modes, and conduct detailed modeling stress analysis of the separated bodies of each component; According to Step 3, when the load / bending moment in the lift direction is applied, apply corresponding proportional loads to the upper and lower hubs respectively, such as Figure 2 As shown; according to step 4, the two ends and the middle of the action range are selected within the load action range of the variable pitch rocker arm structure for loading, such as Figure 3 As shown in points A, B and M, the stress of the variable pitch rocker arm structure under different load action positions is analyzed; the stress calculation under different combination characteristics is completed;

[0042] Step 6: Based on the results of Step 2 and Step 5, conduct static strength analysis and fatigue strength analysis on the upper and lower split tilting hub structure. The static strength analysis should meet

[0043]

[0044] Among them, σ limit is the structural limit stress, K safe is the safety factor; K link is the joint coefficient of each connection part, σ 02 is the material yield limit, and σb is the material strength limit.

[0045] During fatigue strength analysis, the static stress σ of different dangerous parts / positions in state i is obtained respectively. si and dynamic stress σ di , calculate the equivalent dynamic stress:

[0046] σ eqi =σ di / (1-(σ si / σ 02) 2 )

[0047] Among them, σ 02 is the material yield limit

[0048] According to the material safety SN curve and load spectrum, the fatigue damage in each state can be obtained:

[0049] lgN i =a0-b0×lg(σ eqi -σ ∞ ) (3)

[0050]

[0051] Among them, a0 and b0 are material parameters, σ ∞ is the material safety fatigue limit corresponding to an infinite number of cycles, n i is the frequency corresponding to the i-th state per hour, N i is the equivalent dynamic stress σ eqi The number of damages under action, D i is the damage in the ith state.

[0052] According to Miner's linear cumulative damage theory, the safe fatigue life of each dangerous component / part is obtained:

[0053]

[0054] Where m is the load level in the load spectrum and L is the safe fatigue life.

[0055] Furthermore, in step one, the upper and lower split tiltable hub structure can generally be made of aluminum alloy, structural steel, titanium alloy, etc.

[0056] Furthermore, in step three, when the contact relationship between the parts is established, the friction coefficient is determined according to the material and matching relationship of the contact parts, and can generally be taken as a coefficient between 0.02 and 0.2.

[0057] Furthermore, in step six, low cycle fatigue damage may be further considered based on the structure and load spectrum.

[0058] Furthermore, in step 6, K safe Generally, it can be taken as 1.5, K link It can generally be taken as 1.15.

Claims

1. A strength design method for a vertically split tiltable hub, characterized in that: include: Step 1: Analyze the force transmission route and identify dangerous parts based on the upper and lower split tilting hub structure and load; Step 2: Determine the characteristic load set of all dangerous parts according to the loads and dangerous parts of the upper and lower split tiltable hub; Step 3: According to the upper and lower split tiltable hub structure, use finite element simulation or engineering methods to determine the load / bending moment distribution relationship in the lift direction on the upper and lower hubs and their connection structures; Step 4: Determine the load action range of the pitch rocker arm structure according to the upper and lower split tilting hub structure and the variable pitch and variable speed operation process; Step 5: Based on the results of steps 1 to 4, carry out finite element simulation of the upper and lower split tiltable hub structure and perform stress calculation.

2. The method according to claim 1, characterized in that The method further comprises: Step six: Based on the results of steps two and five, conduct static strength analysis and fatigue strength analysis of the upper and lower split tiltable hub structure to complete the strength design.

3. The method according to claim 2, characterized in that Dangerous parts include static strength dangerous parts and fatigue dangerous parts. According to the structure and load of the upper and lower split tilting hub, the force transmission route analysis is carried out and the dangerous parts are determined, including: According to the analysis of the force transmission route, it can be determined that the load and bending moment transmitted by the upper and lower hubs to the blades, and the control load transmitted by the pitch rocker arm and the control structure all show the characteristics of changing with time, which are fatigue loads. Therefore, it is determined that the upper and lower hubs, the pitch rocker arm, the control structure and the related connection structures are all static strength and fatigue risk areas.

4. The method according to claim 3, characterized in that According to the loads and dangerous parts of the upper and lower split tilting hub, the characteristic load set of all dangerous parts is determined, including: According to the loads and dangerous parts of the upper and lower split tiltable hub, the characteristic loads of the upper and lower hubs are determined to include blade centrifugal force, blade shear force and bending moment; the characteristic loads of the variable pitch rocker arm and the control structure are taken as the control loads; and the loads related to the connected structure are determined as the characteristic loads of the connecting structure.

5. The method according to claim 4, characterized in that According to the upper and lower split tiltable hub structure, finite element simulation or engineering methods are used to determine the load / bending moment distribution relationship in the lift direction on the upper and lower hubs and their connection structures, including: Apply bolt preload according to the design value and fix the upper and lower propeller hubs together with bolts; According to the actual contact and connection mode, the upper hub, lower hub, connecting bolts and lift direction bearing are combined for modeling and force transmission analysis. The model structure is simplified without affecting the structural stiffness during modeling. The load / bending moment distribution relationship in the lift direction of the blade is obtained through analysis of the simplified model, that is, the distribution ratio of the upper and lower hub lift.

6. The method according to claim 5, characterized in that The load range of the root variable pitch rocker arm structure is 5 to 15 mm.

7. The method according to claim 5, characterized in that: According to the results of steps 1 to 4, the finite element simulation of the upper and lower split tiltable hub structure is carried out to perform stress calculation, including: Determine all characteristic loads of each component of the upper and lower split tiltable hub and their locations and methods of action, determine the constraint locations and methods, and perform detailed modeling stress analysis of each component as a separate body; when the load / bending moment in the lift direction is applied, apply loads of corresponding distribution proportions to the upper and lower hubs respectively; select the two end points and the middle point of the range of action within the range of action of the variable pitch rocker arm structure load for loading, and analyze the stresses at different action positions of the variable pitch rocker arm structure load; complete the stress calculation.

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

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