High-strength bolt for aviation airplane wheel brake and design optimization method thereof

Abstract

The invention relates to the technical field of airplane wheel braking, in particular to a high-strength bolt for aviation airplane wheel braking and a design optimization method thereof.The method comprises the steps that the dangerous section tensile stress of a single high-strength bolt is obtained; the maximum shear stress borne by the single high-strength bolt is obtained; according to the dangerous section tensile stress and the borne maximum shear stress of the single high-strength bolt, the comprehensive stress of the single high-strength bolt is obtained; and the high-strength bolt meeting the use requirement is obtained. The design method of the high-strength bolt has guiding significance on design and selection of the high-strength bolt for the aviation aircraft wheel.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft wheel brakes, and particularly relates to a high-strength bolt for aircraft wheel brakes and a design optimization method thereof. Background Art

[0002] The braking wheel is a key airborne system to ensure the safety of aircraft takeoff and landing. In recent years, safety problems caused by brake failures have occurred frequently. Therefore, the reliability of the braking wheel directly affects the flight safety of the aircraft. The aircraft braking wheel mainly consists of a wheel assembly and a braking device. Under the braking pressure provided by the braking system, the piston assembly on the cylinder seat assembly generates a hydraulic thrust force on the main braking wheel, so that the piston assembly presses against the brake disc to achieve the braking function.

[0003] The cylinder seat assembly, the brake housing, and the brake disc assembly are important components of the braking device. The conventional brake housing is usually circumferentially limited to the cylinder seat through a stop block and axially limited to the cylinder seat through a snap ring. As Figure 1 shown, the fixed block is fixed in the limit groove of the cylinder seat by screws. In recent years, brake vibration problems have occurred frequently. Excessive vibration or brake vibration that can cause resonance is very harmful. At least, it affects the riding comfort and generates fatigue cracks. At worst, it may cause the landing gear to break, or even lead to aircraft failures or safety accidents. The overall structure has many cooperating parts (mainly the fixed block structure), and the force transmission path is complex. If the clearance with other components is too large, it will inevitably result in insufficient stiffness constraint, thus exacerbating the overall vibration tendency.

[0004] To improve the vibration suppression effect, it is necessary to simplify the cooperating and installed parts or improve the stiffness of the connection form. Using high-strength bolts to connect the cylinder seat assembly and the brake housing can effectively improve the stiffness constraint ability of the brake housing at different connection parts, which is beneficial to enhancing the vibration suppression ability. As Figure 2 shown. As an important part of the braking device, the high-strength bolt connects the cylinder seat and the brake housing through threads. During use, on the one hand, it is subjected to the axial force generated by the thrust of the piston assembly in the cylinder seat assembly, and on the other hand, it also bears the shear force generated by the torsional action under the structural moment of the braking device. Under normal braking pressure and takeoff line braking pressure, the high-strength bolts in the braking device should meet the strength requirements under twice the takeoff line braking pressure, without fracture and damage, and should be able to withstand the structural moment without damage. At the same time, the performance of the high-strength bolts directly affects the service life of the wheel brake system. Therefore, if the design of the high-strength bolts is improper, they are very likely to break during actual braking, resulting in brake failure.

[0005] Although the prior art proposes to fix the inner and outer half hubs of the front wheel by connecting parts such as high-strength bolts, flat washers, and self-locking nuts, the prior art only briefly introduces the high-strength bolts used in wheel assemblies, and has not formed an effective design method for the high-strength bolts in the brake device and their material selection, thread type selection, and design selection ideas, which has no guiding significance for the design of high-strength bolts in actual wheel products.

[0006] Therefore, it is necessary to provide a high-strength bolt for aircraft wheel brakes and a design optimization method thereof to solve the above problems. Summary of the invention

[0007] The invention provides a high-strength bolt for aircraft wheel brake and a design optimization method thereof to solve the existing problems.

[0008] A high-strength bolt for aircraft wheel brakes of the present invention adopts the following technical solution, including: A screw having an MJ thread; and a nut, which is coaxially connected to the end of the screw rod away from the thread, and is provided with a plurality of anti-slip protrusions; Among them, the screw and nut are made of GH4169 high-temperature alloy material.

[0009] Preferably, the nut comprises: The conical hat brim has a large end surface connected to the end of the screw rod, and a small end surface connected to a cylindrical block, wherein the anti-skid protrusion is arranged on the cylindrical block.

[0010] Preferably, a plurality of anti-slip protrusions are evenly distributed on the outer circumferential surface of the cylindrical block along the axial direction of the cylindrical block.

[0011] Preferably, the cross section of the anti-slip protrusion is triangular.

[0012] Preferably, a fuse hole for preventing loosening is provided between two adjacent anti-slip protrusions.

[0013] A design optimization method for high-strength bolts for aircraft wheel brakes adopts the following technical solutions, including: Obtain the tensile stress of the dangerous section of a single high-strength bolt; Obtain the maximum shear stress on a single high-strength bolt; According to the tensile stress of the dangerous section of a single high-strength bolt and the maximum shear stress it is subjected to, the comprehensive stress of a single high-strength bolt is obtained; When the combined stress of the high-strength bolt is less than or equal to the allowable stress of the GH4169 superalloy material, the high-strength bolt meets the service requirements for the axial thrust; when the combined stress of the high-strength bolt is greater than the allowable stress of the GH4169 superalloy material, the number and diameter of the high-strength bolts are increased until the combined stress of the adjusted high-strength bolt is less than or equal to the allowable stress of the GH4169 superalloy material, then the high-strength bolt meets the service requirements.

[0014] Preferably, the steps for obtaining the tensile stress of the critical section of a single high-strength bolt are as follows: According to the braking pressure of the aircraft wheel, obtain the total thrust generated by the piston assembly on a single high-strength bolt; Obtain the pre-tightening force of the high-strength bolt according to the tightening torque of the high-strength bolt; According to the total thrust generated by the piston assembly on a single high-strength bolt and the pre-tightening force of the high-strength bolt, obtain the axial force borne by the high-strength bolt; According to the axial force borne by the high-strength bolt and the diameter of the high-strength bolt, obtain the initial tensile stress of the critical section of the high-strength bolt; When the initial tensile stress of the critical section is greater than or equal to the allowable stress of the GH4169 superalloy material, the high-strength bolt meets the service requirements for the axial thrust; when the initial tensile stress of the critical section is less than the allowable stress of the GH4169 superalloy material, the number and diameter of the high-strength bolts are increased until the tensile stress of the critical section of the adjusted high-strength bolt is greater than or equal to the allowable stress of the GH4169 superalloy material, then the high-strength bolt meets the service requirements for the axial thrust; Take the tensile stress of the critical section when the high-strength bolt meets the service requirements for the axial thrust as the tensile stress of the critical section of the high-strength bolt.

[0015] Preferably, the steps for obtaining the maximum shear stress borne by a single high-strength bolt are as follows: According to the maximum axial force of the high-strength bolt and the total thrust generated by the piston assembly under the maximum braking pressure, obtain the remaining pre-tightening force of the high-strength bolt; According to the number of high-strength bolts and the remaining pre-tightening force of the high-strength bolt, obtain the acting force on the friction surface between the cylinder block and the brake housing, and obtain the friction torque between the cylinder block and the brake housing; According to the difference between the structural torque and the friction torque corresponding to the cylinder block and the brake housing, and the distribution circle radius of the high-strength bolt, obtain the maximum shear force borne by a single high-strength bolt, and obtain the initial maximum shear stress; When the initial maximum shear stress is less than or equal to the allowable stress of the GH4169 superalloy material, the high-strength bolts meet the service requirements for shear stress; when the initial maximum shear stress is greater than the allowable stress of the GH4169 superalloy material, the number and diameter of the high-strength bolts are increased until the maximum shear stress of the adjusted high-strength bolts is less than or equal to the allowable stress of the GH4169 superalloy material, then the high-strength bolts meet the service requirements for shear stress; Take the maximum shear stress at which the high-strength bolts meet the service requirements for shear stress as the maximum shear stress borne by the high-strength bolts.

[0016] Preferably, the expression for the combined stress of a single high-strength bolt is:

[0017] In the formula, represents the combined stress of the high-strength bolt; represents the tensile stress at the critical section of a single high-strength bolt; represents the maximum shear stress borne by a single high-strength bolt.

[0018] The beneficial effects of the present invention are: 1. The high-strength bolts proposed by the present invention are made of GH4169 superalloy material. Compared with the conventional high-strength bolt material 40CrNiMoA structural steel, the GH4169 superalloy material has comprehensive properties such as ultra-high strength, good plasticity and toughness, and high stress corrosion resistance. Its tensile strength can be increased from 900 MPa of 40CrNiMoA to 1500 MPa. It can be used not only for high-temperature fastening bolt parts, but also for ultra-high strength fasteners for aircraft serving in stress corrosion environments (such as marine environments).

[0019] 2. The high-strength bolts proposed by the present invention adopt MJ threads with relatively high fatigue strength. Since the root of the MJ external thread uses a root arc with a relatively large radius, its root is a continuous smooth curve, and the accuracy is higher than that of ordinary threads. Compared with ordinary threads of the same strength, it can further reduce the weight and has a compact specification.

[0020] 3. The high-strength bolts proposed by the present invention are provided with fuse holes at the head. When assembled and used, "paired in twos" are mutually locked to achieve the anti-loosening effect; 4. The present invention also proposes the design idea of the tensile strength and shear strength of high-strength bolts and the design method of the arrangement quantity, which has guiding significance for the design and selection of high-strength bolts for aircraft wheels. Description of the Drawings

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a three-dimensional structural schematic diagram of a high-strength bolt for aircraft wheel brakes of the present invention; Figure 2 This is a front view of a high-strength bolt for aircraft wheel brakes according to the present invention; Figure 3 A schematic diagram of a brake housing and a cylinder seat assembly connected by high-strength bolts according to an embodiment of the present invention; Figure 4 The present invention is a flow chart of a design optimization method for high-strength bolts for aircraft wheel brakes.

[0023] In the figure: 1. screw; 2. nut; 3. fuse hole; 4. cylinder seat; 5. brake housing; 6. piston assembly; 7. brake disc assembly; 8. high-strength bolt. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] An embodiment of a high-strength bolt for aircraft wheel brakes of the present invention is as follows Figure 1 As shown, it includes: a screw rod 1 and a nut 2, wherein the screw rod 1 and the nut 2 are both made of GH4169 high-temperature alloy material, and the thread on the screw rod 1 is an MJ thread; the nut 2 is concentrically connected to the end of the screw rod 1 away from the thread, and a plurality of anti-slip protrusions 21 are arranged on the nut 2.

[0026] For example, Figure 1 and Figure 2 As shown, the nut 2 includes: a conical brim, the large end face of the conical brim is connected to the end of the screw 1, and the small end face of the conical brim is connected to a cylindrical block, wherein a plurality of anti-slip protrusions 21 are evenly distributed on the outer circumferential surface of the cylindrical block along the axial direction of the cylindrical block, the cross-section of the anti-slip protrusion 21 is triangular, and a fuse hole 3 for preventing loosening is provided between two adjacent anti-slip protrusions 21.

[0027] like Figure 3 As shown, Figure 3Schematic diagram of using high-strength bolts provided by this embodiment to connect the brake housing and the cylinder block assembly. Among them, the cylinder block 4 is installed on the brake housing 5 through high-strength bolts 8. Under the braking pressure provided by the brake system, the brake main wheel causes the piston assembly 6 on the cylinder block assembly to generate a hydraulic thrust, so that the piston assembly 6 presses the brake disc assembly 7. The brake disc assembly 7 transmits the braking torque through cooperation with the hub of the aircraft wheel hub to achieve the braking of the aircraft wheel and realize the braking function.

[0028] An embodiment of the design optimization method of a high-strength bolt for an aircraft wheel brake of the present invention is as follows Figure 4 shown. This embodiment includes: S1. Obtain the tensile stress of the dangerous section of a single high-strength bolt; Specifically, the steps for obtaining the tensile stress of the dangerous section of a single high-strength bolt include: S11. According to the braking pressure of the aircraft wheel, obtain the total thrust generated by the piston assembly on a single high-strength bolt, that is, the expression is:

[0029] where F is the total thrust generated by the piston assembly on a single high-strength bolt; D is the piston radius; P is the braking pressure; n is the number of pistons; N is the number of high-strength bolts.

[0030] S12. Obtain the pre-tightening force of the high-strength bolt according to the tightening torque of the high-strength bolt, that is, the expression of the pre-tightening force is:

[0031] In the formula, T is the tightening torque of the high-strength bolt, and T takes (40 - 45) N·m; K is the pre-tightening force calculation coefficient, taking 3.98×10 -3 .

[0032] S13. According to the total thrust generated by the piston assembly on a single high-strength bolt and the pre-tightening force of the high-strength bolt, obtain the axial force borne by the high-strength bolt, that is, the expression of the axial force borne by the high-strength bolt is:

[0033] In the formula, is the axial force borne by the high-strength bolt; is the axial coefficient, taking 0.73.

[0034] S14. According to the axial force borne by the high-strength bolt and the diameter of the high-strength bolt, obtain the initial tensile stress of the dangerous section of the high-strength bolt, that is, the initial tensile stress of the dangerous section is:

[0035] In the formula, is the diameter of the high-strength bolt.

[0036] S15. At the tensile stress of the initial dangerous section is greater than or equal to the allowable stress of the GH4169 superalloy material , that is ≥ , the high-strength bolt meets the service requirements for the axial thrust; at the tensile stress of the initial dangerous section is less than the allowable stress of the GH4169 superalloy material , that is < , by increasing the number and diameter of the high-strength bolts until the tensile stress of the dangerous section of the adjusted high-strength bolt is greater than or equal to the allowable stress of the GH4169 superalloy material , then the high-strength bolt meets the service requirements for the axial thrust.

[0037] S16. Take the tensile stress of the dangerous section where the high-strength bolt meets the service requirements for the axial thrust as the tensile stress of the dangerous section of the high-strength bolt .

[0038] S2. Obtain the maximum shear stress borne by a single high-strength bolt; Since the high-strength bolt not only bears the axial force but also bears the shear force generated by the torsional action of the braking device during braking. During the process of bearing the torque, the pre-tightening force of the bolt generates a frictional torque through the contact surface between the cylinder block and the brake housing to eliminate the braking torque during braking and prevent torsional movement between the brake housing and the cylinder block; under the action of the pre-tightening force of the high-strength bolt, a frictional torque will be generated between the contact surfaces of the cylinder block and the brake housing, and the magnitude of this torque is related to the magnitude of the frictional force f and the distribution circle diameter r of the high-strength bolts. When the working pressure is greater, the remaining pre-tightening force of the cylinder block / brake housing friction surface is smaller, the frictional torque is smaller, and the shear force borne by the high-strength bolt is greater. Therefore, it is necessary to examine the shear situation of the bolts when the braking pressure is P.

[0039] Exemplarily, in one embodiment, the steps to obtain the maximum shear stress borne by a single high-strength bolt are as follows: S21. According to the maximum axial force of the high-strength bolt and the total thrust generated by the piston assembly under the maximum braking pressure, obtain the remaining pre-tightening force of the high-strength bolt, that is, the expression of the remaining pre-tightening force is:

[0040] In the formula, is the maximum axial force of the high-strength bolt; is the total thrust generated by the piston assembly under the maximum braking pressure.

[0041] S22. Obtain the acting force on the friction surface between the cylinder block and the brake housing according to the number of high-strength bolts and the remaining pre-tightening force of the high-strength bolts, and obtain the frictional torque between the cylinder block and the brake housing; Among them, the acting force on the friction surface between the cylinder block and the brake housing (the acting force is the normal pressure) is expressed as:

[0042] In the formula, n1 is the number of high-strength bolts.

[0043] Among them, the frictional torque M f between the cylinder block and the brake housing is expressed as:

[0044] In the formula, is the friction coefficient between the cylinder block and the brake housing, taking 0.15; r is the distribution circle diameter of the high-strength bolts.

[0045] S23. According to the difference between the structural torque and the frictional torque corresponding to the cylinder block and the brake housing, and the distribution circle radius of the high-strength bolts, obtain the maximum shear force received by a single high-strength bolt, and obtain the initial maximum shear stress; Among them, the maximum shear force received by a single high-strength bolt is expressed as:

[0046] In the formula, is the difference between the structural torque and the frictional torque M f .

[0047] Among them, the initial maximum shear stress is expressed as:

[0048] In the formula, A represents the dangerous cross-sectional area of the high-strength bolt, that is, the dangerous cross-sectional area of the high-strength bolt.

[0049] S24. When the initial maximum shear stress is less than or equal to the allowable stress of the GH4169 superalloy material, ≥ , the high-strength bolts meet the usage requirements for shear stress; when the initial maximum shear stress is greater than the allowable stress of the GH4169 superalloy material, that is, < When it is, by increasing the number and diameter of high-strength bolts until the maximum shear stress of the adjusted high-strength bolts is less than or equal to the allowable stress of the GH4169 superalloy material , then the high-strength bolts meet the service requirements for shear stress; S25. Take the maximum shear stress at which the high-strength bolts meet the service requirements for shear stress as the maximum shear stress borne by the high-strength bolts .

[0050] S3. Obtain the combined stress of a single high-strength bolt based on the tensile stress of the critical section of a single high-strength bolt and the maximum shear stress borne by it; Combined stress The expression is:

[0051] S4. Obtain high-strength bolts that meet the service requirements; Specifically, when the combined stress of the high-strength bolts is less than or equal to the allowable stress of the GH4169 superalloy material , that is ≥ when, the high-strength bolts meet the service requirements for axial thrust; when the combined stress of the high-strength bolts is greater than the allowable stress of the GH4169 superalloy material , that is < when, by increasing the number and diameter of high-strength bolts until the combined stress of the adjusted high-strength bolts is less than or equal to the allowable stress of the GH4169 superalloy material , then the high-strength bolts meet the service requirements.

[0052] In summary, a high-strength bolt for aircraft wheel brakes and its design optimization method provided by the embodiments of the present invention pass through.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-strength bolt for aircraft wheel brakes, characterized in that: include: A screw having an MJ thread; and a nut, which is coaxially connected to the end of the screw rod away from the thread, and is provided with a plurality of anti-slip protrusions; Among them, the screw and nut are made of GH4169 high-temperature alloy material.

2. A high-strength bolt for aircraft wheel brakes according to claim 1, characterized in that: Nut includes: The conical hat brim has a large end surface connected to the end of the screw rod, and a small end surface connected to a cylindrical block, wherein the anti-skid protrusion is arranged on the cylindrical block.

3. A high-strength bolt for aircraft wheel brakes according to claim 2, characterized in that: A plurality of anti-skid protrusions are evenly distributed on the outer peripheral surface of the cylindrical block along the axial direction of the cylindrical block.

4. The high-strength bolt for aircraft wheel brakes according to claim 1, characterized in that: The cross section of the anti-slip protrusion is a triangle.

5. The high-strength bolt for aircraft wheel brakes according to claim 1, characterized in that: A fuse hole for preventing loosening is arranged between two adjacent anti-slip protrusions.

6. A design optimization method for high-strength bolts for aircraft wheel brakes, characterized in that: include: Obtain the tensile stress of the dangerous section of a single high-strength bolt; Obtain the maximum shear stress on a single high-strength bolt; According to the tensile stress of the dangerous section of a single high-strength bolt and the maximum shear stress it is subjected to, the comprehensive stress of a single high-strength bolt is obtained; When the comprehensive stress of the high-strength bolt is less than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolt meets the use requirements of the axial thrust; when the comprehensive stress of the high-strength bolt is greater than the allowable stress of the GH4169 high-temperature alloy material, by increasing the number of high-strength bolts and the diameter of the high-strength bolts until the adjusted comprehensive stress of the high-strength bolt is less than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolt meets the use requirements.

7. The design optimization method for high-strength bolts for aircraft wheel brakes according to claim 6, characterized in that: The steps to obtain the tensile stress of the dangerous section of a single high-strength bolt are: According to the braking pressure of the aircraft wheel, the total thrust generated by the piston assembly on a single high-strength bolt is obtained; Obtain the preload force of the high-strength bolts according to the tightening torque of the high-strength bolts; The axial force borne by the high-strength bolt is obtained according to the total thrust generated by the piston assembly on a single high-strength bolt and the pre-tightening force of the high-strength bolt; According to the axial force borne by the high-strength bolt and the diameter of the high-strength bolt, the initial dangerous cross-section tensile stress of the high-strength bolt is obtained; When the initial tensile stress of the dangerous section is greater than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolt meets the use requirements of the axial thrust; when the initial tensile stress of the dangerous section is less than the allowable stress of the GH4169 high-temperature alloy material, by increasing the number of high-strength bolts and the diameter of the high-strength bolts until the tensile stress of the dangerous section of the adjusted high-strength bolts is greater than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolt meets the use requirements of the axial thrust; The tensile stress of the dangerous section of the high-strength bolt that meets the use requirements of axial thrust is used as the tensile stress of the dangerous section of the high-strength bolt.

8. The design optimization method for high-strength bolts for aircraft wheel brakes according to claim 6, characterized in that: The steps to obtain the maximum shear stress of a single high-strength bolt are: Obtain the residual preload of the high-strength bolt according to the maximum axial force of the high-strength bolt and the total thrust generated by the piston assembly under the maximum brake pressure; According to the number of high-strength bolts and the residual preload of the high-strength bolts, the force acting on the friction surface of the cylinder seat and the brake housing is obtained, and the friction torque of the cylinder seat and the brake housing is obtained; According to the difference between the structural moment and the friction moment corresponding to the cylinder seat and the brake housing, and the radius of the distribution circle of the high-strength bolt, the maximum shear force on a single high-strength bolt is obtained, and the initial maximum shear stress is obtained; When the initial maximum shear stress is less than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolts meet the use requirements of the shear stress; when the initial maximum shear stress is greater than the allowable stress of the GH4169 high-temperature alloy material, by increasing the number of high-strength bolts and the diameter of the high-strength bolts until the adjusted maximum shear stress of the high-strength bolts is less than or equal to the allowable stress of the GH4169 high-temperature alloy material, the high-strength bolts meet the use requirements of the shear stress; The maximum shear stress of the high-strength bolt that meets the shear stress requirements is taken as the maximum shear stress to which the high-strength bolt is subjected.

9. The design optimization method for high-strength bolts for aircraft wheel brakes according to claim 1, characterized in that: The expression of the comprehensive stress of a single high-strength bolt is: In the formula, Indicates the comprehensive stress of high-strength bolts; Indicates the dangerous cross-sectional tensile stress of a single high-strength bolt; Indicates the maximum shear stress borne by a single high-strength bolt.

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