Method for calculating stress of high-strength bolt for aviation aircraft wheel

Abstract

The invention discloses a high-strength bolt stress calculation method for an aviation aircraft wheel, and belongs to the field of high-strength bolt design. The method comprises the steps that the sum of external loads borne by a single high-strength bolt is calculated based on the external loads borne by the single high-strength bolt due to tire inflation pressure and tire foot external expansion tension of the single high-strength bolt due to tire compression; calculating the initial tension of the single high-strength bolt caused by the pre-tightening torque; calculating a bolt equivalent stiffness coefficient; the maximum force borne by the single high-strength bolt is calculated based on the sum of the external loads borne by the single high-strength bolt, the initial pulling force, caused by the pre-tightening torque, of the single high-strength bolt and the equivalent stiffness coefficient of the bolt; bolt stress is calculated based on the maximum force borne by the single high-strength bolt. According to the method, the problems of cracks, fractures and the like of the bolt in engineering practice are avoided, and basic data are provided for the reliability of the bolt in practical application.

Description

Technical Field

[0001] The invention belongs to the field of high-strength bolt design, and in particular relates to a stress calculation method for high-strength bolts used in aircraft wheels. Background Art

[0002] In the field of aviation brakes, the brake system is the last barrier for safe takeoff and landing of aircraft. It needs to be used thousands of times in complex and harsh environments. Among them, aircraft wheels are an important part of the aircraft brake system. Aircraft wheels are installed on the main landing gear of the aircraft for takeoff, landing, traction taxiing, ground taxiing, turning, landing braking and parking. These functions together ensure the safe operation of the aircraft and the comfort of passengers.

[0003] Typical wheel structures include split structures and bolted single-web structures. High-strength bolts are important parts that connect the various components of the wheel structure and bear the fatigue load and ultimate load of the aircraft. If problems such as bolt cracks, reduced bolt preload, bolt deformation and breakage occur during use, the stress and fatigue results of the bolts used to install and fix components will increase, leading to the risk of wheel leakage and reduced load-bearing capacity, which will directly affect the reliability of the wheel structure and cause safety accidents. Therefore, great caution must be exercised when designing and selecting high-strength bolts.

[0004] In order to avoid the problems of bolts loosening, breaking, etc. during use and ensure the landing brake safety of the aircraft, the present invention proposes a stress calculation method for high-strength bolts for aircraft wheels. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a method for calculating the stress of high-strength bolts for aircraft wheels. By calculating the external load on the bolt, the bolt stiffness coefficient and the stiffness coefficient of the connected part, the maximum stress on the bolt is obtained, and by comparing the allowable stress of the bolt, it is determined whether the strength of the bolt meets the strength design requirements. The present invention avoids the problems of cracks and fractures of the bolts in actual engineering, and provides basic data for its reliability in practical applications.

[0007] The technical solution of the present invention is: a method for calculating the stress of high-strength bolts for aircraft wheels, and the specific steps are as follows:

[0008] Calculate the external load on a single high-strength bolt caused by tire inflation pressure;

[0009] Calculate the bulging tension of a single high-strength bolt caused by tire compression;

[0010] Based on the external load on a single high-strength bolt caused by the tire inflation pressure and the external expansion tension of the tire foot of a single high-strength bolt caused by tire compression, the sum of the external loads on a single high-strength bolt is calculated;

[0011] Calculate the initial tension of a single high-strength bolt caused by the preload torque;

[0012] Calculate the equivalent stiffness coefficient of the bolt;

[0013] The maximum force on a single high-strength bolt is calculated based on the sum of the external loads on the single high-strength bolt, the initial tension of the single high-strength bolt caused by the pre-tightening torque, and the equivalent stiffness coefficient of the bolt;

[0014] Calculates bolt stress based on the maximum force experienced by a single high-strength bolt.

[0015] A further technical solution of the present invention is: the method for calculating the external load borne by a single high-strength bolt caused by tire inflation pressure is:

[0016] Calculate external loads caused by tire inflation pressure;

[0017] The external load caused by the tire inflation pressure is calculated and divided by the pressure variation coefficient, and then divided by the number of high-strength bolts connecting the inner and outer half hubs on the aircraft wheel, to obtain the external load borne by a single high-strength bolt caused by the tire inflation pressure.

[0018] A further technical solution of the present invention is: the calculation formula of the external load borne by the single high-strength bolt caused by the tire inflation pressure is as follows:

[0019]

[0020] Among them, P C is the external load caused by the tire inflation pressure, P0 is the normal tire inflation pressure, R is the nominal tire radius, r is the tire section height, R gd is the tire combination radius; n is the number of high-strength bolts; f is the pressure variation coefficient.

[0021] A further technical solution of the present invention is that the calculation formula of the bulging tension of the tire foot of a single high-strength bolt caused by tire compression is as follows:

[0022]

[0023] Among them, K is a coefficient determined by the tire diameter and compression.

[0024] A further technical solution of the present invention is: the calculation formula for the sum of the external loads borne by the single high-strength bolt is:

[0025] A further technical solution of the present invention is: the formula for calculating the initial tension of a single high-strength bolt caused by the pre-tightening torque is:

[0026]

[0027] Among them, M is the preload torque, d is the nominal diameter of the bolt, and μ is the friction coefficient between the nut and the supporting surface of the connected part.

[0028] A further technical solution of the present invention is: the method for calculating the equivalent stiffness coefficient of the bolt is:

[0029] Calculate the bolt stiffness coefficient using the following formula:

[0030]

[0031] Among them, E I is the elastic modulus of the bolt, I is the bolt connection length;

[0032] Calculate the stiffness coefficient of the connected parts using the following formula:

[0033]

[0034] Among them, A B is the equivalent compressive area of ​​the connected parts, d0 is the inner diameter of the hole of the connected part, D0=1.5d+αI B , I B is the total thickness of the connected parts under pressure, I d is the thickness of the gasket, α is the coefficient determined by the material coefficient of the connected parts, the material is steel α = 0.1, the material is cast iron α = 0.125, the material is aluminum alloy α = 0.17, E B is the elastic modulus of the connected parts, E d is the elastic modulus of the gasket;

[0035] Based on the stiffness coefficient of the bolt and the stiffness coefficient of the connected parts, the equivalent stiffness coefficient of the bolt is calculated, and the formula is as follows:

[0036]

[0037] A further technical solution of the present invention is: the calculation formula of the maximum force on the single high-strength bolt is:

[0038] P max =P I +K C P.

[0039] A further technical solution of the present invention is: the calculation formula of the bolt stress is:

[0040]

[0041] A further technical solution of the present invention is: the condition that the bolt strength satisfies is that when σ≥[σ 0.2 ], the bolt does not meet the fatigue requirements, when σ<[σ 0.2 ], the bolts meet the fatigue requirements.

[0042] Beneficial Effects

[0043] The beneficial effects of the present invention are:

[0044] The present invention proposes a stress calculation method for high-strength bolts for aircraft wheels, which fully considers the influence of the external load on the bolt, the bolt stiffness coefficient and the stiffness coefficient of the connected part on the bolt strength, calculates the maximum stress on the bolt, and judges whether the strength of the bolt meets the strength design requirement by comparing the allowable stress of the bolt, thereby providing basic data for its reliability in practical applications.

[0045] According to statistics, the high-strength bolts designed according to the method of the present invention have been applied to multiple models of products. After simulation analysis and test verification, they meet the strength requirements under various working conditions and complex conditions. At the same time, according to the fatigue load requirements specified in GJB 3376, the fatigue test is carried out at a cycle frequency of 200 to 6500 times / min, and the average fatigue life is not less than 1.8×10 7 It meets the service life requirements and effectively solves the problems of bolt loosening and breakage during field use.

[0046] The calculation method of the present invention greatly reduces the trial and error cost in the design process, meets the increasingly complex and demanding technical environment of aircraft wheels, and ensures that the bolts can play their connecting and supporting roles while ensuring high reliability.

[0047] The calculation method of the present invention adapts to the increasingly complex and demanding technical environment of aircraft wheels, ensuring that the bolts can play their connecting and supporting roles while ensuring high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is an assembly diagram of the inner and outer half hubs connected by high-strength bolts of the present invention.

[0049] Figure 2 It is a schematic diagram of the high-strength bolt structure of the present invention.

[0050] Explanation of the reference numerals: 1 - outer half hub; 2 - inner half hub; 3 - high-strength bolt; 4 - gasket; 5 - nut. DETAILED DESCRIPTION

[0051] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0052] Based on the low strength of bolts designed in the prior art, problems such as loosening and breaking may occur during use. The present invention provides a method for calculating the stress of high-strength bolts for aircraft wheels. The specific steps are as follows:

[0053] Step 1: Calculate the external load on a single high-strength bolt caused by tire inflation pressure;

[0054] Step 2: Calculate the bulging tension of a single high-strength bolt caused by tire compression;

[0055] Step 3: Based on the external load on a single high-strength bolt caused by the tire inflation pressure and the external expansion tension of the tire foot of a single high-strength bolt caused by tire compression, calculate the sum of the external loads on a single high-strength bolt;

[0056] Step 4: Calculate the initial tension of a single high-strength bolt caused by the preload torque;

[0057] Step 5: Calculate the equivalent stiffness coefficient of the bolt;

[0058] Step 6: Calculate the maximum force on a single high-strength bolt based on the sum of the external loads on the single high-strength bolt, the initial tension of the single high-strength bolt caused by the preload torque, and the equivalent stiffness coefficient of the bolt;

[0059] Step 7: Calculate bolt stress based on the maximum force applied to a single high-strength bolt.

[0060] The calculation method of the present invention adapts to the increasingly complex and demanding technical environment of aircraft wheels, ensuring that the bolts can play their connecting and supporting roles while ensuring high reliability.

[0061] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0062] Reference Figure 1 As shown, the split wheel is connected by high-strength bolts 3 to the outer half hub 1 and the inner half hub 2.

[0063] Reference Figure 2 As shown, the high-strength bolt 3 connects the inner and outer half hubs through the matching gasket 4 and the nut 5.

[0064] This embodiment provides an example of stress analysis of high-strength bolts in a split wheel, and performs bolt stress calculation according to the calculation method in the invention content to verify the feasibility of this method for calculating high-strength bolt stress in a split wheel.

[0065] The bolt specification is M14 and the number of bolts is 16.

[0066] Step 1, calculating the external load caused by the tire inflation pressure;

[0067]

[0068] Among them, P0 is the normal inflation pressure of the tire, R is the nominal radius of the tire, r is the section height of the tire, R gd is the tire joint radius.

[0069] In this embodiment, P0=1.5MP, and the split wheel is equipped with a 762×224R381 tire. The external load P caused by the tire inflation pressure is calculated as C =213767.22N.

[0070] Step 2, calculating the external load borne by a single high-strength bolt due to the inflation pressure according to the external load caused by the tire inflation pressure calculated in step 1;

[0071]

[0072] Where n is the number of bolts, f is the pressure variation coefficient, and when the bolts are designed according to fatigue strength, f=2.5, and when they are designed according to static strength, f=3.5.

[0073] In this embodiment, n = 14; f = 3.5. The external load P borne by a single high-strength bolt due to the inflation pressure is calculated as P =3817.27N.

[0074] Step 3, calculating the external expansion tension of the tire foot of the single high-strength bolt caused by tire compression according to the external load borne by the single high-strength bolt due to the inflation pressure calculated in step 2;

[0075]

[0076] Among them, K is a coefficient determined by the tire diameter and compression.

[0077] In this embodiment, K = 0.5. The external load on a single high-strength bolt due to the inflation pressure is calculated to calculate the external expansion tension P of a single high-strength bolt caused by tire compression. W =7634.54N.

[0078] Step 4, calculating the initial tension of a single high-strength bolt caused by the preload torque;

[0079]

[0080] Where M is the preload torque, d is the nominal diameter of the bolt, μ is the friction coefficient between the nut and the supporting surface of the connected part, and μ = 0.15 when lubricated.

[0081] In this embodiment, M = 60 N.m; the bolt specification is M14; μ = 0.17. The initial tension P of a single high-strength bolt caused by the preload torque is calculated as I =50420.17N.

[0082] Step 5, calculating the sum P of the external loads on the single high-strength bolt according to the inflation pressure of the single high-strength bolt calculated in step 2 and the external expansion tension of the tire foot of the single high-strength bolt caused by tire compression calculated in step 3;

[0083]

[0084] The calculated sum of external loads on a single high-strength bolt is P=11451.82N.

[0085] Step 6: Calculate the bolt stiffness coefficient;

[0086]

[0087] Among them, E I is the elastic modulus of the bolt, I is the bolt connection length.

[0088] In this embodiment, the bolt material is GH4169; I =70GPa; I = 70mm. The bolt stiffness coefficient C is calculated L =1.54E+08.

[0089] Step 7, calculate the stiffness coefficient of the connected parts;

[0090]

[0091] Among them, A B is the equivalent compressive area of ​​the connected parts, d0 is the inner diameter of the hole of the connected part, D0=1.5d+αI B , I B is the total thickness of the connected parts under pressure, I d is the thickness of the gasket, α is determined by the material coefficient of the connected parts (steel α=0.1; cast iron α=0.125; aluminum alloy α=0.17), the material is steel α=0.1, the material is cast iron α=0.125, the material is aluminum alloy α=0.17, E B is the elastic modulus of the connected parts, E d is the elastic modulus of the gasket.

[0092] In this embodiment, α=0.17; d0=7mm; I B =70mm,; E B=69GPa; E d =206GPa; I d =4mm. Calculate the stiffness coefficient C of the connected part B =7.85E+08.

[0093] Step 8, calculating the equivalent stiffness coefficient of the bolt according to the stiffness coefficient of the bolt calculated in step 6 and the stiffness coefficient of the connected member calculated in step 7;

[0094]

[0095] Calculate the equivalent stiffness coefficient K of the bolt C =0.164.

[0096] Step 9, calculating the maximum force borne by a single high-strength bolt according to the initial tension of the single high-strength bolt caused by the pre-tightening torque calculated in step 4, the sum P of the external loads borne by the single high-strength bolt calculated in step 5, and the bolt equivalent stiffness coefficient calculated in step 8;

[0097] P max =P I +K C P

[0098] The maximum force P of a single high-strength bolt is calculated max =52297.65N.

[0099] Step 10, calculating the bolt stress according to the maximum force on the single high-strength bolt calculated in step 9;

[0100]

[0101] The calculated bolt stress σ=339.73MPa.

[0102] Theoretical calculations and physical tests show that high-strength wheel bolts should be designed according to fatigue strength, which means:

[0103] When σ≥[σ 0.2 ], the bolt does not meet the fatigue requirements, when σ<[σ 0.2 ], the bolts meet the fatigue requirements. In this embodiment, the bolt material is GH4169, σ 0.2 =700MPa, satisfying σ<[σ 0.2 ], that is, the bolts meet the fatigue requirements.

[0104] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for calculating stress of high-strength bolts for aircraft wheels, characterized in that The specific steps are as follows: Calculate the external load on a single high-strength bolt caused by tire inflation pressure; Calculate the bulging tension of a single high-strength bolt caused by tire compression; Based on the external load on a single high-strength bolt caused by the tire inflation pressure and the external expansion tension of the tire foot of a single high-strength bolt caused by tire compression, the sum of the external loads on a single high-strength bolt is calculated; Calculate the initial tension of a single high-strength bolt caused by the preload torque; Calculate the equivalent stiffness coefficient of the bolt; The maximum force on a single high-strength bolt is calculated based on the sum of the external loads on the single high-strength bolt, the initial tension of the single high-strength bolt caused by the pre-tightening torque, and the equivalent stiffness coefficient of the bolt; Calculates bolt stress based on the maximum force experienced by a single high-strength bolt.

2. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 1, characterized in that: The method for calculating the external load on a single high-strength bolt caused by tire inflation pressure is: Calculate external loads caused by tire inflation pressure; The external load caused by the tire inflation pressure is calculated and divided by the pressure variation coefficient, and then divided by the number of high-strength bolts connecting the inner and outer half hubs on the aircraft wheel, thus obtaining the external load borne by a single high-strength bolt caused by the tire inflation pressure.

3. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 2, characterized in that: The calculation formula for the external load borne by a single high-strength bolt caused by the tire inflation pressure is as follows: Among them, P C is the external load caused by the tire inflation pressure, P0 is the normal tire inflation pressure, R is the nominal tire radius, r is the tire section height, R gd is the tire combination radius; n is the number of high-strength bolts; f is the pressure variation coefficient.

4. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 3, characterized in that: The calculation formula for the bulging tension of a single high-strength bolt caused by tire compression is as follows: Among them, K is a coefficient determined by the tire diameter and compression.

5. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 4, characterized in that: The calculation formula for the sum of the external loads on the single high-strength bolt is:

6. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 5, characterized in that: The formula for calculating the initial tension of a single high-strength bolt caused by the preload torque is: Among them, M is the preload torque, d is the nominal diameter of the bolt, and μ is the friction coefficient between the nut and the supporting surface of the connected part.

7. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 6, characterized in that: The method for calculating the equivalent stiffness coefficient of the bolt is: Calculate the bolt stiffness coefficient using the following formula: Among them, E I is the elastic modulus of the bolt, I is the bolt connection length; Calculate the stiffness coefficient of the connected parts using the following formula: Among them, A B is the equivalent compressive area of ​​the connected parts, d0 is the inner diameter of the hole of the connected part, D0=1.5d+αI B , I B is the total thickness of the connected parts under pressure, I d is the thickness of the gasket, α is the coefficient determined by the material coefficient of the connected parts, the material is steel α = 0.1, the material is cast iron α = 0.125, the material is aluminum alloy α = 0.17, E B is the elastic modulus of the connected parts, E d is the elastic modulus of the gasket; Based on the stiffness coefficient of the bolt and the stiffness coefficient of the connected parts, the equivalent stiffness coefficient of the bolt is calculated, and the formula is as follows:

8. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 7, characterized in that: The calculation formula for the maximum force on a single high-strength bolt is: P max =P I +K C P.

9. A method for calculating stress of high-strength bolts for aircraft wheels according to claim 8, characterized in that: The calculation formula of the bolt stress is:

10. The method for calculating stress of high-strength bolts for aircraft wheels according to claim 9, characterized in that: The condition for whether the bolt strength meets the requirement is that when σ≥[σ 0.2 ], the bolt does not meet the fatigue requirements, when σ<[σ 0.2 ], the bolts meet the fatigue requirements.

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