A "transient damping" metamaterial bolted joint structure

Abstract

The application discloses a material bolt connection structure of "transmitting static load and restraining dynamic load", and relates to the technical field of vibration reduction of bolt connection structure of an aero-engine and a fuselage. The bolt connection structure comprises two local resonance type metamaterial plates, a bolt and a nut. The local resonance type metamaterial plate is formed by integrating a spiral resonant system into a variable-wall-thickness multistage honeycomb structure, the spiral resonant system is periodically distributed, and a bolt hole is arranged on the local resonance type metamaterial plate for mounting the bolt and the nut. The spiral resonant system is formed by cutting spiral elastic beams on the upper and lower surfaces of the plate, and vertically mounting cylindrical oscillators between the spiral elastic beams. The bolt connection structure is designed as a variable-wall-thickness multistage honeycomb structure, has stronger compression mechanical performance and higher energy absorption rate, and can complete the transmission of static load. The spiral resonant system is periodically embedded on the plate of the bolt connection structure, the vibration reduction frequency band is flexibly adjustable, the elastic wave is efficiently manipulated, and the dynamic load is restrained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration reduction of bolt connection structure of aero-engine and fuselage, in particular to a metamaterial bolt connection structure of "transmitting static and suppressing dynamic", BACKGROUND

[0002] The connection structure is an essential component in mechanical systems. Due to the wide speed and large space of the flight profile of an aircraft, it will experience complex mechanical environments such as strong thrust, high lift, vibration and impact. The bolt connection structure between the aero-engine and the aircraft is a weak link in the mechanical performance of the aircraft, bearing the transmission of static and dynamic loads, and participating in the vibration of the whole machine, which is the key path of energy flow. Taking the typical whole machine vibration of a certain type of aero-engine as an example, the low-pressure fundamental frequency and the high-pressure fundamental frequency are about 95 Hz and 179 Hz respectively. How to make the connection structure suppress the dangerous vibration of the aero-engine at the fundamental frequency from being transmitted to the aircraft is of great significance to improve the service life of the aircraft and reduce the cabin noise.

[0003] In Chinese invention patents with publication numbers CN 112382461 A and CN 113775064 B, rubber pads are used in the bolt connection structure to achieve vibration reduction and noise reduction. In Chinese invention patents with publication numbers CN 113775231 B and CN 117432078 A, a vibration damping assembly designed with springs and rubber is used to complete the attenuation of vibration. In US invention patent with publication number US10,274,037B2, a rubber part is also used to dissipate vibration energy, achieving the vibration reduction effect of the connection structure. However, the attenuation effect of using rubber or spring, which is an elastic body, on vibration is low, only dissipating a part of the energy, and cannot achieve a large degree of vibration attenuation.

[0004] In order to meet the strict requirements of the aerospace field for vibration control, it is urgent to design a new type of connection structure that can efficiently control the dangerous vibration of the aero-engine at the fundamental frequency without damaging the integrity of the connection structure and conflicting with the strength and stiffness requirements of the connection structure itself. SUMMARY

[0005] To solve the problem of dangerous vibration of the aero-engine at the fundamental frequency being transmitted to the aircraft, the present application integrates the elastic wave manipulation ability of the spiral harmonic system into the variable wall thickness multi-stage honeycomb structure with light weight and high strength mechanical properties, and designs a metamaterial bolt connection structure of "transmitting static and suppressing dynamic".

[0006] To achieve the above purpose, the present application provides the following technical solution: a metamaterial bolt connection structure of "transmitting static and suppressing dynamic", comprising an upper plate and a lower plate of a locally resonant metamaterial, a bolt hole is provided on the plate, and the upper plate and the lower plate of the locally resonant metamaterial can be fixed by lapping with a bolt and a nut.

[0007] Preferably, the upper plate and the lower plate of the local resonance type metamaterial are the same structure, which integrates a spiral resonant system into a variable wall thickness multi-stage honeycomb structure, the spiral resonant system realizes efficient elastic wave manipulation ability through the resonance of local resonators, and the variable wall thickness multi-stage honeycomb structure has light weight and high strength mechanical properties through gradient design and multi-stage design.

[0008] Preferably, the spiral resonant system is periodically embedded in the upper and lower plates of the connecting structure, and the spiral resonant system mainly consists of two spiral elastic beams and a cylindrical resonator; wherein the spiral elastic beam is cut from two Archimedes spirals, and the cylindrical resonator and the spiral elastic beam are connected by welding.

[0009] Preferably, the variable wall thickness multi-stage honeycomb structure includes inner circular hole and outer circular corner features, so that the honeycomb structure has the characteristics of variable wall thickness and multi-stage, and has stronger compression mechanical properties and higher energy absorption rate compared with conventional honeycomb structures.

[0010] Preferably, the spiral resonant system can change the equivalent stiffness K of the system by adjusting the height, width and spiral angle of the spiral elastic beam, or change the equivalent mass M of the system by adjusting the diameter, height and material of the cylindrical resonator, according to the resonant frequency f = 1 / 2πK / M 1 / 2 , and then realize the flexible adjustable characteristics of the vibration reduction frequency band of the bolted joint structure, which can be expanded to the vibration control of other precision equipment.

[0011] Preferably, the material density of the cylindrical resonator is generally greater than that of the spiral elastic beam; if the material of the spiral elastic beam is structural steel, the preferred material of the cylindrical resonator can be designed as lead; the greater the material density of the resonator, the higher the equivalent mass, and the lower the vibration reduction frequency band.

[0012] Preferably, according to the VDI 2230 standard, the flexibility of the bolt is much greater than that of the lower plate and the upper plate of the local resonance type metamaterial, that is, the lattice constant a and the height h of the spiral resonant system need to meet: a > dw + h; wherein dw represents the diameter of the support surface of the bolt.

[0013] Preferably, the "static transmission" means that the bolted joint structure can transmit static load in the vertical direction; and the "dynamic suppression" means that the bolted joint structure can suppress dynamic load in the horizontal direction.

[0014] Preferably, the spiral resonant system is embedded in the variable wall thickness multi-stage honeycomb structure, which is more compact in space compared with the external resonant system, and lighter in mass compared with the solid connection structure, and can be better applied to the field of aerospace.

[0015] Compared with the prior art, the present application has the beneficial effects that:

[0016] 1、The helical resonant system of the present application is periodically embedded into the plate of the connecting structure without damaging the integrity of the connecting structure, and the first order mode of the helical elastic beam is the bending mode, which can suppress the transmission of bending waves in the connecting structure at low frequency.

[0017] 2、The main body of the present application uses a variable wall thickness multi-stage honeycomb structure, which can realize lightweight while meeting the strength and stiffness requirements of the bolted connection structure in an aero-engine.

[0018] 3、The present application can easily realize low-frequency adjustable band gap by changing the geometric parameters and material parameters of the helical elastic beam or the vibrator, and can be expanded to the vibration control needs of other precision equipment.

[0019] 4、The present application is a multifunctional combination of metamaterials and honeycomb structures, and compared with the elastic elements used for vibration reduction in the published patent, the bolted connection structure of the present application has more significant vibration reduction effect. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The overall structure axial view provided by the present application;

[0021] Figure 2 The overall structure top view provided by the present application;

[0022] Figure 3 The overall structure side cross-sectional view provided by the present application

[0023] Figure 4 The enlarged structure schematic view at B in Figure 3

[0024] Figure 5 The helical resonant system schematic view of the present application;

[0025] Figure 6 The variable wall thickness multi-stage honeycomb structure schematic view of the present application;

[0026] Figure 7 The time history response curve graph of the present application when the excitation frequency is 95Hz;

[0027] In the figure: 1, local resonance type metamaterial lower plate; 2, local resonance type metamaterial upper plate; 3, bolt; 4, nut; 5, cylindrical vibrator; 6, helical resonant system; 7, variable wall thickness multi-stage honeycomb structure; 11, helical elastic beam; 12, inner circular hole; 13, outer round corner; 14, bolt hole. DETAILED DESCRIPTION

[0028] ​In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] As shown in Figure 1 , 2 , 3, a "static transmission and motion suppression" metamaterial bolt connection structure includes a local resonance type metamaterial lower plate 1, a local resonance type metamaterial upper plate 2, a bolt 3 and a nut 4. The local resonance type metamaterial lower plate 1 and the local resonance type metamaterial upper plate 2 are structurally identical, both of which integrate a spiral resonant system 6 into a variable-wall-thickness multi-stage honeycomb structure 7 and are provided with a bolt hole 14. The local resonance type metamaterial lower plate 1 and the local resonance type metamaterial upper plate 2 are overlapped by the bolt 3 and the nut 4. The spiral resonant system 6 is periodically distributed and includes an upper and lower spiral elastic beam 11 and a cylindrical vibrator 5. The spiral elastic beam 11 is cut from two Archimedes spirals, and the cylindrical vibrator 5 and the spiral elastic beam 11 are connected by welding.

[0030] As shown in Figure 4 , 5 , 6, the variable-wall-thickness multi-stage honeycomb structure 7 includes inner circular holes 12 and outer rounded corners 13 features, so that the honeycomb structure has the characteristics of variable wall thickness and multi-stage. The height, width and spiral angle of the spiral elastic beam 11 can be adjusted to change the equivalent stiffness of the system, or the diameter, height and material of the cylindrical vibrator 5 can be adjusted to change the equivalent mass of the system, thereby realizing the flexible adjustable characteristics of the vibration reduction frequency band of the bolt connection structure. The material density of the cylindrical vibrator 5 is generally greater than that of the spiral elastic beam 6, so as to obtain a relatively high equivalent mass and a low-frequency vibration reduction frequency band. According to the VDI 2230 criterion, the flexibility of the bolt 3 is much greater than that of the local resonance type metamaterial lower plate 1 and the local resonance type metamaterial upper plate 2, that is, the lattice constant a and the height h of the spiral resonant system 6 need to meet: a > d w +h; wherein d w represents the diameter of the support surface of the bolt.

[0031] Embodiment one:

[0032] The size parameters and material parameters of the "static transmission and motion suppression" metamaterial bolt connection structure are designed according to the low-pressure fundamental frequency of about 95 Hz of the typical whole machine vibration of a certain type of aero-engine.

[0033] The material of the local resonance type metamaterial lower plate 1, the local resonance type metamaterial upper plate 2, the bolt 3 and the nut 4 is preferably structural steel, the density of which is 7850 kg / m 3 , the Young's modulus is 210 GPa, and the Poisson's ratio is 0.3; the material of the cylindrical vibrator 5 is lead, the density of which is 11340 kg / m 3 , the Young's modulus is 17 GPa, and the Poisson's ratio is 0.42. The height of the cylindrical vibrator 5 is 20 mm, and the radius is 7.5 mm; the height of the spiral resonant system 6 is 23 mm, the lattice constant is 50 mm, the height of the spiral elastic beam 11 is 1.5 mm, the width is 3.5 mm, and the spiral angle is 2.25pi; the thickness of the variable-wall-thickness multistage honeycomb structure 7 is 1.5 mm, the radius of the inner circular hole 12 is 4 mm, and the radius of the outer circular corner is 10 mm.

[0034] As shown in Figure 1 , 7 , a bolt connection structure of a super material that transmits static and suppresses vibration applies a point excitation harmonic load at a position 20 mm away from the edge of a local resonance type metamaterial lower plate 1, and records a response load at a position 20 mm away from the edge of a local resonance type metamaterial upper plate 2. When the excitation frequency is 95 Hz, the acceleration response amplitude of the output signal is significantly smaller than that of the input signal, and the vibration suppression effect reaches 83%.

[0035] The mechanism and advantages of the bolt connection structure of the super material that transmits static and suppresses vibration are described below. The cylindrical vibrator 5 is fixed between the upper and lower spiral elastic beams 11, and is equivalent to a single-degree-of-freedom spring-mass system; when the bolt connection structure is subjected to external excitation, if the excitation frequency is close to the natural frequency of the single-degree-of-freedom system, the single-degree-of-freedom system will produce anti-phase vibration with the bolt connection structure; such anti-phase motion will generate a force opposite to the vibration direction of the bolt connection structure, thereby offsetting part of the vibration energy of the external excitation acting on the bolt connection structure and reducing the amplitude of the bolt connection structure. The bolt connection structure of the super material that transmits static and suppresses vibration periodically embeds the spiral resonant system 6 into the plate of the connection structure, without damaging the integrity of the connection structure; the main body of the bolt connection structure uses a variable-wall-thickness multistage honeycomb configuration, which can achieve lightweight while meeting the strength and stiffness requirements of the connection structure in an aero-engine. By changing the geometric parameters and material parameters of the spiral elastic beam 11 or the cylindrical vibrator 5, the low-frequency bandgap can be easily adjusted, and the vibration control requirements of other precision equipment can be expanded. The present application is a multifunctional combination of metamaterials and honeycomb structures. Compared with the published patent using elastic elements for vibration reduction, the bolt connection structure of the present application has more significant vibration reduction effect. Compared with the external resonant system, the space is more compact. Compared with the solid connection structure, the mass is lighter.

[0036] It is apparent for a person skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments, but that it can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than the above description, and all changes coming within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, no reference signs in the claims being regarded as limiting the claim in which they are used.

Claims

1. A metamaterial bolted joint structure that "transmits static and suppresses dynamic", comprising a local resonance type metamaterial lower plate (1), a local resonance type metamaterial upper plate (2), a bolt (3), and a nut (4); characterized in that, The local resonance type metamaterial lower plate (1) and the local resonance type metamaterial upper plate (2) are provided with bolt holes (14), and the local resonance type metamaterial lower plate (1) and the local resonance type metamaterial upper plate (2) are overlapped by bolts (3) and nuts (4) through the bolt holes (14); the local resonance type metamaterial lower plate (1) and the local resonance type metamaterial upper plate (2) are the same structure, and the spiral resonant system (6) is embedded into the variable wall thickness multi-stage honeycomb structure (7); The spiral resonant system (6) has high elastic wave manipulation ability, and the variable wall thickness multi-stage honeycomb structure (7) has light weight and high strength mechanical properties; the spiral resonant system (6) is periodically distributed, including two spiral elastic beams (11) and a cylindrical vibrator (5); wherein the spiral elastic beam (11) is cut from two Archimedes spirals, and the cylindrical vibrator (5) and the spiral elastic beam (11) are connected by welding; the "static transmission" is the vertical direction, and the "motion suppression" is the horizontal direction.

2. A "vibration-damping" metamaterial bolted joint structure according to claim 1, characterized in that, The variable wall thickness multi-stage honeycomb structure (7) includes an inner circular hole (12) and an outer round corner (13), so that the honeycomb structure has the characteristics of variable wall thickness and multi-stage.

3. A "vibration-damping" metamaterial bolted joint structure according to claim 1, characterized in that, The spiral resonant system (6) changes the equivalent stiffness of the system by adjusting the height, width and spiral angle of the spiral elastic beam (11), or changes the equivalent mass of the system by adjusting the diameter, height and material of the cylindrical vibrator (5), thereby realizing the flexible adjustable characteristics of the vibration reduction frequency band of the bolted joint structure.

4. A metamaterial bolted joint structure that transmits static and suppresses dynamic according to claim 3, characterized in that, The material density of the cylindrical vibrator (5) is greater than that of the spiral elastic beam (6), thereby obtaining a relatively high equivalent mass and realizing a low-frequency vibration reduction frequency band.

5. A "vibration-damping" metamaterial bolted joint structure according to claim 1, characterized in that, The spiral resonant system (6) is embedded into the variable wall thickness multi-stage honeycomb structure (7).

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