A ball contact type nonlinear dynamic vibration absorber and its operating method

Abstract

The present invention relates to a ball-contact nonlinear dynamic vibration absorber and its operating method, comprising an upper mounting seat, an upper supporting cylindrical sleeve, an adjustment component, a lower mounting seat, a lower supporting cylindrical sleeve, a rubber ball, a compression threaded rod, and a mass block. The upper mounting seat and the lower mounting seat are respectively mounted in the upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve, the mass block is mounted between the two rubber balls, the rubber ball and the mass block are placed between the upper mounting seat and the lower mounting seat, the upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve are connected by a compression threaded rod, and the distance between them is adjusted by the adjustment component. The upper supporting cylindrical sleeve is provided with a threaded mounting rod, and the vibration absorber is connected to the main vibration system via the threaded mounting rod. The present invention adopts a new variable stiffness form of ball contact to provide stiffness parameters in the dynamic vibration absorber and applies different contact pressures by tightening the screw. The structure is novel, the vibration suppression frequency band is wide, and the feasibility is high.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration reduction and noise reduction processing, and in particular to a ball contact type nonlinear stiffness adjustable dynamic vibration absorber and an operating method thereof. Background Art

[0002] With the continuous development of science and technology, the issue of mechanical vibration has gradually attracted people's attention and exploration. Solving the series of negative problems caused by vibration remains a hot topic in current research. Dynamic vibration absorbers are currently an effective technology for suppressing vibration. Their basic principle is to attach a substructure, namely the vibration absorber, to the main vibration system. The structural form, dynamic parameters, and coupling relationship of the substructure with the main vibration system are appropriately selected to change the vibration state of the main vibration system, thereby reducing the forced vibration response of the main vibration system within the desired frequency range. Traditional dynamic vibration absorbers design a three-parameter vibration absorption structure based on mass-damping-linear spring according to the structural characteristics of the main vibration system. Although this dynamic vibration absorption structure has a good vibration suppression effect for a single vibration frequency point and within a similar frequency range, the vibration absorption parameters are fixed and the structure cannot be changed. When facing a main vibration system with a wide vibration frequency band, the vibration absorption effect is very small. In addition, when the damping ratio of the dynamic vibration absorber itself or the natural frequency of the main vibration system changes and deviates from the optimal design state, the vibration suppression performance will decrease accordingly. Therefore, in order to improve the robustness of the dynamic vibration absorber affected by these parameters, multiple dynamic vibration absorbers came into being, that is, one or more vibration absorption structures are connected in parallel in the single vibration absorption structure. Although this method increases the vibration suppression frequency band of the dynamic vibration absorber to a certain extent, the vibration suppression frequency band is still not wide. To maximize the vibration suppression bandwidth of dynamic vibration absorbers and improve their adaptive characteristics, active, adjustable dynamic vibration absorbers with feedback systems have been extensively researched. These typically use sensors to measure the vibration information of the main vibration system and feed it back to a central controller. Active devices then use this feedback to adjust the modifiable parameter structure in real time, thereby achieving targeted changes in the absorber frequency. While this approach offers excellent vibration suppression, it suffers from complex structures, low reliability, and high energy consumption, making it unsuitable for applications requiring low energy consumption and high reliability, such as aerospace systems. Consequently, nonlinear parameter dynamic vibration absorber structures have been introduced to improve absorber performance. Studies have shown that the vibration suppression bandwidth of nonlinear absorbers is twice that of corresponding linear absorbers when the nonlinearity is strong. Current designs utilize monolithic structures, such as nonlinear springs, and applications that incorporate nonlinear parameters based on contact theory are limited.

[0003] In view of this, it is of great significance to design a ball contact type dynamic vibration absorber with adjustable nonlinear stiffness, namely a tuned mass damper. Summary of the Invention

[0004] In response to the defects of existing dynamic vibration absorbers, such as wide vibration suppression bandwidth, high energy consumption, low reliability, and lack of universal applicability, the present invention provides a ball-contact type dynamic vibration absorber with adjustable nonlinear stiffness. The present invention utilizes the contact stiffness adjustability and nonlinear characteristics generated by the compression deformation of the rubber ball to design the dynamic vibration absorber, and constructs a theoretical model from the adjustment end to the contact stiffness end. Unlike traditional dynamic vibration absorbers, where the vibration absorption parameters cannot be changed after the structure is fixed, a passive adjustable method is used to change the vibration absorption stiffness parameters, and the overall dynamic vibration absorber consumes no energy. The rubber ball element is made of a common material, has adjustable stiffness when a certain contact force and contact form are applied, and has strong adaptability to load and vibration frequency. Changing the rubber ball, contact form, or mass block parameters can provide a more flexible and wide vibration suppression frequency band. It avoids the disadvantages of complex structure and low reliability brought about by active control, has a simple structure, is easy to install, has high reliability, low development cost, and strong interchangeability, and is applicable to main vibration systems of any structural form.

[0005] The present invention also provides an operating method of the ball contact type nonlinear dynamic vibration absorber.

[0006] The technical solution of the present invention is:

[0007] A ball contact type nonlinear stiffness adjustable dynamic vibration absorber comprises an upper mounting seat, an upper supporting cylindrical sleeve, an adjusting component, a lower mounting seat, a lower supporting cylindrical sleeve, a rubber ball, a compression threaded rod and a mass block, wherein:

[0008] The upper mounting seat and the lower mounting seat are respectively installed in the upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve. A mass block is installed between the two rubber balls. The rubber balls and the mass block are placed between the upper mounting seat and the lower mounting seat. The upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve are connected by a compression threaded rod and the distance between the two is adjusted by an adjusting component. A threaded mounting rod is provided on the upper supporting cylindrical sleeve, and the vibration absorber is connected to the main vibration system through this threaded mounting rod.

[0009] According to the preferred embodiment of the present invention, the upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve are fixed to the adjusting component by a compression threaded rod. Both ends of the compression threaded rod are provided with a certain length of thread for screwing the adjusting component into and applying pressure to the rubber ball. The certain length refers to the length of the rubber ball diameter. and between.

[0010] According to the preferred embodiment of the present invention, the number of the rubber balls is an even number, and the even number of rubber balls is arranged to realize the movement of the mass block in multiple degrees of freedom.

[0011] Preferably, according to the present invention, the contact forms of the two rubber balls are consistent, and the upper mounting seat, the rubber ball, the mass block and the lower mounting seat are symmetrically arranged with respect to a vertical line of the central axis of the dynamic vibration absorber.

[0012] Further preferably, the contact form between the rubber ball and the upper supporting cylindrical sleeve, the lower supporting cylindrical sleeve and the mass block is inner conical surface contact or inner spherical surface contact with the same size parameters.

[0013] Preferably, according to the present invention, a threaded mounting rod is provided on the central axis of the circular surface of the upper supporting cylindrical sleeve, and the threaded mounting rod is an integrated threaded mounting rod.

[0014] Preferably, according to the present invention, the upper mounting seat is connected to the upper supporting cylindrical sleeve by countersunk screws, and the lower mounting seat is connected to the lower supporting cylindrical sleeve by hexagon socket head screws.

[0015] Preferably, according to the present invention, the upper supporting cylindrical sleeve, the lower supporting cylindrical sleeve, the upper mounting seat and the lower mounting seat are all made of aluminum alloy 2A12; the rubber ball is made of low-phenyl silicone rubber; and the mass block is made of stainless steel metal material 9Cr18Mo.

[0016] Preferably, according to the present invention, the two rubber balls are symmetrically pressed against the upper and lower sides of the mass block, and contact constraints exist between the rubber balls and the mass block only in the axial direction.

[0017] The operating method of the above-mentioned ball contact type nonlinear stiffness adjustable dynamic vibration absorber comprises:

[0018] (1) Measure the vibration characteristics of the main vibration system, use the hammer method or the exciter method to perform modal testing based on the structural characteristics of the main vibration system, identify its modal parameters from the frequency response function curve of the main vibration system, and obtain the natural frequency of the main vibration system;

[0019] (2) The mass range of the vibration absorber is determined based on the overall mass requirements of the main vibration system and the minimum vibration reduction requirements. The range of the mass ratio μ of the vibration absorber mass block m1 to the main vibration system mass m2 is given. The mass block mass m1 is given according to the structural space constraints, and the natural frequency ω of the vibration absorber is obtained based on the optimal coherent design conditions of the dynamic vibration absorber. a , calculate the contact stiffness k2 of one end of a single rubber ball, calculate the vibration absorber damping c based on the optimal damping conditions, and determine the rubber ball material and hardness value H A ;

[0020] (3) Determine the inner cone semi-cone angle θ and the rubber ball diameter R1 based on the rubber ball fixing requirements, the internal installation space requirements of the vibration absorber, and the rubber ball damping value. Determine the normal pressure F on the rubber ball based on the Hertz contact theory. Then, calculate the nut tightening torque M based on the relationship between the nut tightening torque M and the normal pressure F on the rubber ball.

[0021] (4) Install the vibration absorber on the main vibration system, tighten the nut with the given calculated nut tightening torque value, and the rubber ball will generate contact stiffness. Then the vibration of the main vibration system will be transmitted to the rubber ball and the mass block position, and the vibration absorber will suppress the vibration.

[0022] According to the preferred embodiment of the present invention, in step (2), the formula for obtaining the contact stiffness k2 of one end of a single rubber ball is as shown in formula (I):

[0023]

[0024] In formula (I), w refers to the normal strain of the rubber ball contact area, and F is the normal pressure on the rubber ball.

[0025] According to the preferred embodiment of the present invention, in step (2), the material of the dynamic vibration absorber is aluminum alloy 2A12, and the material of the mass block is stainless steel metal material 9Cr18Mo. The elastic modulus and Poisson's ratio of the rubber ball can be obtained by looking up the mechanical design manual; the relationship between the elastic modulus and hardness value of the rubber ball is shown in formula (II):

[0026]

[0027] In formula (II), E2 is the elastic modulus of the rubber ball, H A is the Shore hardness of the rubber ball.

[0028] According to a preferred embodiment of the present invention, in step (3), the nut tightening torque is calculated by the relationship between the bolt tightening torque and the normal pressure on the rubber ball, as shown in formula (III):

[0029]

[0030] In formula (III), M is the tightening torque of the nut, F is the normal pressure on the rubber ball, d2 is the pitch diameter of the threads at both ends of the compression threaded rod, λ is the thread lead angle, t is the thread pitch at both ends of the compression threaded rod, f is the friction coefficient between the adjusting nut and the upper supporting cylindrical sleeve, ρ is the equivalent friction angle of the helical pair, β is the thread half angle, f' is the friction coefficient between the helical pairs, R is the outer radius of the nut bearing surface, and r is the inner radius of the nut bearing surface.

[0031] The beneficial effects of the present invention are:

[0032] 1. All structural parts of the present invention are simple to process, do not require high assembly precision, are easy to assemble, and do not require active equipment to adjust the variable stiffness, so the reliability is high.

[0033] 2. The present invention adopts a new variable stiffness ball contact method to provide stiffness parameters in the dynamic vibration absorber and applies different contact pressures by tightening the screws. The structure is novel, the vibration suppression frequency band is wide, and the feasibility is high.

[0034] 3. The structure corresponding to the contact-related parameters of the rubber ball of this invention can be changed according to the application and vibration environment. It has extremely high controllability, high interchangeability, wide vibration suppression bandwidth, simple and compact structure, and low cost. It can meet the vibration absorption requirements of many equipment, especially small and medium-sized aerospace equipment with extremely high vibration level requirements. It has the advantages of low design cost and simple installation, while taking into account passive control and zero energy consumption. In addition, the simple threaded mounting position makes it highly applicable for both ground and aerospace applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the cross-section of the structure of the ball contact type dynamic vibration absorber with adjustable nonlinear stiffness according to the present invention;

[0036] Figure 2 Schematic diagram of the structure and appearance of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber of the present invention;

[0037] FIG3( a ) is a schematic cross-sectional view of the inner spherical contact structure of the rubber ball of the present invention;

[0038] FIG3( b ) is a schematic cross-sectional view of the contact structure of the inner cone surface of the rubber ball of the present invention;

[0039] Figure 4 This is a schematic flow chart of the operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber of the present invention;

[0040] Among them, 1. upper mounting seat; 2. upper supporting cylindrical sleeve; 3. adjusting nut; 4. lower mounting seat; 5. lower supporting cylindrical sleeve; 6. rubber ball; 7. compression threaded rod; 8. mass block; 9. threaded mounting rod. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below in conjunction with the accompanying drawings and embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0042] Example 1

[0043] A ball contact type nonlinear stiffness adjustable dynamic vibration absorber, such as Figure 1 、 Figure 2 As shown, it includes an upper mounting seat 1, an upper supporting cylindrical sleeve 2, an adjusting nut 3, a lower mounting seat 4, a lower supporting cylindrical sleeve 5, a rubber ball 6, a compression threaded rod 7 and a mass block 8, wherein,

[0044] The upper mounting seat 1 and the lower mounting seat 4 are respectively installed in the upper supporting cylindrical sleeve 2 and the lower supporting cylindrical sleeve 5 by screws. A mass block 8 is installed between the two rubber balls 6. The rubber balls 6 and the mass block 8 are placed between the upper mounting seat 1 and the lower mounting seat 4. The upper supporting cylindrical sleeve 2 and the lower supporting cylindrical sleeve 5 are connected by a compression threaded rod 7 and the distance between the two is adjusted by adjusting the nut 3. A threaded mounting rod 9 is provided on the upper supporting cylindrical sleeve 2, and the vibration absorber is connected to the main vibration system through this threaded mounting rod 9.

[0045] The dynamic vibration absorber adjusts the tightening torque between the adjustment nut 3 and the compression threaded rod 7 to change the screw-in distance. This in turn applies varying positive pressures to the rubber ball 6 through the upper and lower mounting bases 1 and 4, causing contact deformation and generating variable contact stiffness. This changes the natural frequency of the tuned mass damper, aligning the natural frequency of the dynamic vibration absorber with that of the primary vibration system. A portion of the primary vibration system's vibration passes through the damper's metal structure and is then dissipated by the rubber ball 6, while a portion is transmitted to the mass block 8 for vibration suppression, thereby absorbing the primary vibration system. The three equivalent parameters of the dynamic vibration absorber are: stiffness—the contact stiffness between the inner conical surface of the rubber ball 6 and the mass block 8; damping—the damping of the rubber ball 6 material; and mass—the mass of the mass block 8.

[0046] Example 2

[0047] The difference between the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to embodiment 1 is that:

[0048] The upper supporting cylindrical sleeve 2 and the lower supporting cylindrical sleeve 5 are fixed to the adjusting nut 3 through four M4×60 compression threaded rods 7. Both ends of the compression threaded rod 7 are provided with a certain length of thread for screwing the adjusting nut 3 into and applying pressure to the rubber ball 6. The certain length refers to the length within the diameter of the rubber ball 6. and A small amount of compression of the rubber ball 6 can produce a certain contact stiffness. If the axial compression distance exceeds the diameter of the rubber ball 6, When the pressure is adjusted, the pressure applied by the tightening torque of the adjusting nut 3 can be calculated using the calculation formula.

[0049] There are two rubber balls 6, each with a diameter of 60 mm. The two rubber balls 6 are arranged to enable the mass block 8 to move in multiple degrees of freedom, thereby achieving the purpose of vibration absorption.

[0050] The two rubber balls 6 have the same contact form, and the upper mounting seat 1, rubber ball 6, mass block 8, and lower mounting seat 4 are arranged symmetrically about the central axis of the dynamic vibration absorber. This avoids the coupling characteristics of contact stiffness caused by different contact modes and asymmetric structural positions, which can lead to large calculated deviations in contact stiffness and affect the effectiveness of the dynamic vibration absorber. The upper mounting seat 1, lower mounting seat 4, and mass block 8 can be replaced according to the contact form required by the rubber ball 6, making them easy to disassemble and assemble, and highly interchangeable and controllable. As shown in Figures 3(a) and 3(b), the contact form between the rubber ball 6 and the upper supporting cylindrical sleeve 2, lower supporting cylindrical sleeve 5, and mass block 8 is either an inner conical surface contact or an inner spherical surface contact with identical dimensional parameters. The semi-cone angle of the inner cone is 30°, and the inner spherical diameter is 60 mm. Both contact forms have the function of fixing the rubber ball 6, and the contact form is simple, making the contact model easy to construct. The semi-cone angle of the inner cone and the inner sphere radius are important parameters that determine the contact stiffness, are highly controllable, and have a high adaptability to the vibration absorption frequency band.

[0051] A threaded mounting rod 9 is provided on the central axis of the circular surface of the upper supporting cylindrical sleeve 2, and the threaded mounting rod 9 is an integrated threaded mounting rod 9. It is convenient for the installation of the dynamic vibration absorber and the main vibration system, and the operation is simple and efficient.

[0052] The upper mounting base 1 is connected to the upper support cylindrical sleeve 2 with two M3×12 countersunk screws, and the lower mounting base 4 is connected to the lower support cylindrical sleeve 5 with two M3×12 hexagon socket head screws. This prevents the upper mounting base 1 and the lower mounting base 4 from being unstable and shaking, which would cause additional frictional vibration. It also facilitates the introduction of vibrations from the main vibration system into the stiffness-damping structure, achieving efficient vibration absorption and suppression.

[0053] The upper support cylindrical sleeve 2, lower support cylindrical sleeve 5, upper mounting base 1, and lower mounting base 4 are all made of 2A12 aluminum alloy, resulting in a lightweight and high-strength dynamic vibration absorber. The rubber ball 6 is made of corrosion-resistant, low-phenyl silicone rubber. To achieve a high mass ratio and optimal vibration absorption, the vibration frequency of the dynamic vibration absorber can be adjusted by adjusting the hardness, diameter, material, and contact pattern of the rubber ball 6, resulting in a wide adjustable vibration absorption band. The mass block 8 is made of high-density stainless steel 9Cr18Mo.

[0054] The material and mass of the mass block 8 can be changed according to the requirements of the main vibration system, but the overall volume and mass of the mass block 8 must be controlled within a certain range. The overall volume of the mass block 8 must not exceed the volume of the built-in space of the rubber ball 6 in its natural state and the limit assembly of the overall vibration absorber element. Based on the requirements of lightweight and optimal design of the dynamic vibration absorber, the mass ratio of the mass block 8 to the main vibration system should not exceed 0.2 to avoid irregular sliding of the mass block 8 and interference caused by excessive mass and volume.

[0055] The two rubber balls 6 are symmetrically pressed against the upper and lower sides of the mass 8, and the contact constraint between the rubber balls 6 and the mass 8 exists only in the axial direction. The vibration of the main vibration system not only excites the compression mode of the rubber balls 6, but also their rocking mode and other modes. Therefore, this dynamic vibration absorber has a strong vibration absorption effect not only in the axial direction, but also in other directions to a large extent.

[0056] Example 3

[0057] The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber described in embodiment 1 or 2 is as follows: Figure 4 As shown, including:

[0058] (1) Measure the vibration characteristics of the main vibration system, use the hammer method or the exciter method to perform modal testing based on the structural characteristics of the main vibration system, identify its modal parameters from the frequency response function curve of the main vibration system, and obtain the natural frequency of the main vibration system;

[0059] (2) The mass range of the vibration absorber is determined based on the overall mass requirements of the main vibration system and the minimum vibration reduction requirements. The range of the mass ratio μ of the vibration absorber mass block 8 m1 and the main vibration system mass m2 is given. The mass block 8 m1 is given according to the structural space constraints, and the natural frequency ω of the vibration absorber is obtained based on the optimal coherent design conditions of the dynamic vibration absorber. a , calculate the contact stiffness k2 of one end of a single rubber ball 6, calculate the vibration absorber damping (i.e., the damping of the rubber ball 6) c based on the optimal damping condition, and determine the material and hardness value H of the rubber ball 6 A ;

[0060] (3) Determine the inner cone semi-cone angle θ and the diameter R1 of the rubber ball 6 by comprehensively considering the fixing requirements of the rubber ball 6, the internal installation space requirements of the vibration absorber, and the damping value of the rubber ball 6. Determine the normal pressure F on the rubber ball 6 based on the Hertz contact theory. Then, calculate the nut tightening torque M based on the relationship between the nut tightening torque M and the normal pressure F on the rubber ball 6.

[0061] (4) Install the vibration absorber on the main vibration system, tighten the nut with the given calculated nut tightening torque value, and the rubber ball 6 will generate contact stiffness. Then the vibration of the main vibration system will be transmitted to the rubber ball 6 and the mass block 8, and the vibration absorber will suppress the vibration.

[0062] In step (2), the formula for calculating the contact stiffness k2 of one end of a single rubber ball 6 is shown in formula (1):

[0063]

[0064] In formula (I), w refers to the normal strain of the contact area of ​​the rubber ball 6, and F is the normal pressure on the rubber ball 6.

[0065] In step (2), the contact stiffness of the rubber ball 6 is in the form of series-parallel connection:

[0066] A single rubber ball 6 has contact forms at both ends. The upper end of the upper rubber ball 6 contacts the supporting cylindrical sleeve, and the lower end contacts the mass block 8. If there is contact at the two locations with the same structural form, the contact stiffness at the two locations is connected in series. The calculation relationship is shown as follows:

[0067]

[0068] Where k up is the overall contact stiffness of the upper rubber ball 6, k down is the overall contact stiffness of the lower rubber ball 6.

[0069] The two rubber balls 6 are each regarded as a whole contact stiffness, and are connected to the mass block 8 respectively. Then the contact stiffness of the two rubber balls 6 is connected in parallel. The total contact stiffness generated in the vibration absorber is calculated as follows:

[0070] k all =k up +k down =k2

[0071] The derivation process of the contact stiffness of one end of a single rubber ball 6 in step (2) is given by the following formula:

[0072] Apply force F and F N The relationship between them can be expressed as:

[0073]

[0074] Where F is the normal pressure on the rubber ball 6, F N is the normal pressure on the contact line between the lower hemisphere of the rubber ball 6 and the inner conical surface or inner spherical surface of the support, that is, the force per unit circumference, θ is the semi-cone angle of the inner cone, and R1 is the radius of the rubber ball 6;

[0075] According to the Hertz contact modeling theory, the normal pressure distribution function on the contact surface is expressed as:

[0076]

[0077] Where x is the distance from any point on the contact surface to the center of the removal, p(x) is the normal pressure distribution function of the contact surface, b is the contact half-width, p0 is the contact distribution coefficient, and E * is the equivalent elastic modulus, E1, μ1, E2, and μ2 are the elastic modulus and Poisson's ratio of the contact structure (upper mounting seat 1, lower mounting seat 4, mass block 8) of the rubber ball 6 and the rubber ball 6, respectively.

[0078]

[0079] The stress component generated by p(x) distributed at any point in the rubber ball 6 is:

[0080]

[0081]

[0082] Where σ x is the stress component in the x direction, σ z is the stress component in the z direction, and z is the distance from the contact normal to the origin.

[0083] In the contact mechanics description, under any contact surface pressure distribution, the z-direction strain at any point in the entire rubber ball 6 is obtained from Hooke's law of plane strain as follows:

[0084]

[0085] Wherein, E2 is the elastic modulus of the rubber ball 6, ν is the Poisson's ratio of the rubber ball 6, ν = μ2.

[0086] Then the normal strain of the rubber ball 6 contact area is expressed as:

[0087]

[0088] Where w is the normal strain of the contact area of ​​the rubber ball 6, and R1 is the radius of the rubber ball 6.

[0089] The nonlinear stiffness generated by the compression geometric deformation, that is, the contact stiffness of a single rubber ball 6, is:

[0090]

[0091] In step (2), the material of the dynamic vibration absorber is aluminum alloy 2A12, and the material of the mass block 8 is stainless steel metal material 9Cr18Mo. The elastic modulus and Poisson's ratio of the rubber ball 6 are obtained by looking up the mechanical design manual. For rubber materials, the rubber hardness value is often used in engineering to characterize the size of the elastic modulus. The relationship between the elastic modulus and the hardness value of the rubber ball 6 is shown in formula (II):

[0092]

[0093] In formula (II), E2 is the elastic modulus of the rubber ball 6, H A is the Shore hardness of the rubber ball 6.

[0094] In step (3), the nut tightening torque is calculated by the relationship between the bolt tightening torque and the normal pressure on the rubber ball 6, as shown in formula (III):

[0095]

[0096] In formula (III), M is the tightening torque of the nut, F is the normal pressure on the rubber ball 6, d2 is the pitch diameter of the threads at both ends of the compression threaded rod 7, λ is the thread lead angle, t is the thread pitch at both ends of the compression threaded rod 7, f is the friction coefficient between the adjusting nut 3 and the upper supporting cylindrical sleeve 2, ρ is the equivalent friction angle of the helical pair, β is the thread half angle, f' is the friction coefficient between the helical pairs, R is the outer radius of the nut bearing surface, and r is the inner radius of the nut bearing surface.

[0097] The foregoing is an example of the best mode of carrying out the present invention. Any portion not described in detail herein is common knowledge within the skill of one of ordinary skill in the art. The scope of protection of the present invention is determined by the claims. Any equivalent transformation based on the technical teachings of the present invention is also within the scope of protection of the present invention.

Claims

1. A method for operating a ball-contact type nonlinear stiffness adjustable dynamic vibration absorber, the vibration absorber comprising an upper mounting seat, an upper supporting cylindrical sleeve, an adjusting component, a lower mounting seat, a lower supporting cylindrical sleeve, a rubber ball, a compression threaded rod, and a mass block, wherein: The upper mounting seat and the lower mounting seat are respectively installed in the upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve, and a mass block is installed between the two rubber balls. The rubber balls and the mass block are placed between the upper mounting seat and the lower mounting seat. The upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve are connected by a compression threaded rod, and the distance between them is adjusted by an adjustment component. The upper supporting cylindrical sleeve is provided with a threaded mounting rod, and the vibration absorber is connected to the main vibration system through this threaded mounting rod; it is characterized by comprising: (1) Measure the vibration characteristics of the main vibration system, use the hammer method or the exciter method to perform modal testing based on the structural characteristics of the main vibration system, identify its modal parameters from the frequency response function curve of the main vibration system, and obtain the natural frequency of the main vibration system; (2) The mass range of the vibration absorber is determined based on the overall mass requirements of the main vibration system and the minimum vibration reduction requirements. The range of the mass ratio μ of the vibration absorber mass block m1 to the main vibration system mass m2 is given. The mass block mass m1 is given according to the structural space constraints, and the natural frequency ω of the vibration absorber is obtained based on the optimal coherent design conditions of the dynamic vibration absorber. a , calculate the contact stiffness k2 of one end of a single rubber ball, calculate the vibration absorber damping c based on the optimal damping conditions, and determine the rubber ball material and hardness value H A ; (3) Determine the inner cone semi-cone angle θ and the rubber ball diameter R1 based on the rubber ball fixing requirements, the internal installation space requirements of the vibration absorber, and the rubber ball damping value. Determine the normal pressure F on the rubber ball based on the Hertz contact theory. Then, calculate the nut tightening torque M based on the relationship between the nut tightening torque M and the normal pressure F on the rubber ball. (4) Install the vibration absorber on the main vibration system, tighten the nut with the given calculated nut tightening torque value, and the rubber ball will generate contact stiffness. Then the vibration of the main vibration system will be transmitted to the rubber ball and the mass block position, and the vibration absorber will suppress the vibration.

2. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: The upper supporting cylindrical sleeve and the lower supporting cylindrical sleeve are fixed to the adjusting component through a compression threaded rod. Both ends of the compression threaded rod are provided with a certain length of thread for screwing the adjusting component into and applying pressure to the rubber ball. The certain length refers to the length within the diameter of the rubber ball. and between.

3. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: The number of the rubber balls is an even number, and the even-numbered rubber ball structure arrangement enables the mass block to move in multiple degrees of freedom.

4. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 3, characterized in that: The contact forms of the two rubber balls are consistent, and the upper mounting seat, the rubber ball, the mass block and the lower mounting seat are symmetrically arranged with respect to a vertical line of the central axis of the dynamic vibration absorber.

5. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 4, characterized in that: The contact forms of the rubber ball, the upper supporting cylindrical sleeve, the lower supporting cylindrical sleeve and the mass block are inner cone contact or inner spherical contact with the same size parameters.

6. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: A threaded mounting rod is provided on the central axis of the circular surface of the upper supporting cylindrical sleeve, and the threaded mounting rod is an integrated threaded mounting rod; The upper mounting seat is connected to the upper supporting cylindrical sleeve by countersunk screws, and the lower mounting seat is connected to the lower supporting cylindrical sleeve by hexagon socket head screws.

7. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: The materials of the upper supporting cylindrical sleeve, the lower supporting cylindrical sleeve, the upper mounting seat and the lower mounting seat are all aluminum alloy 2A12; the material of the rubber ball is low-phenyl silicone rubber; and the material of the mass block is stainless steel metal material 9Cr18Mo.

8. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: The two rubber balls are symmetrically pressed against the upper and lower sides of the mass block, and there is contact constraint between the rubber balls and the mass block only in the axial direction.

9. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: In step (2), the formula for calculating the contact stiffness k2 of one end of a single rubber ball is shown in formula (1): In formula (I), w refers to the normal strain of the rubber ball contact area, and F is the normal pressure on the rubber ball; In step (2), the material of the dynamic vibration absorber is aluminum alloy 2A12, and the material of the mass block is stainless steel metal material 9Cr18Mo. The elastic modulus and Poisson's ratio of the rubber ball can be obtained by looking up the mechanical design manual; the relationship between the elastic modulus and hardness value of the rubber ball is shown in formula (II): In formula (II), E2 is the elastic modulus of the rubber ball, H A is the Shore hardness of the rubber ball.

10. The operating method of the ball contact type nonlinear stiffness adjustable dynamic vibration absorber according to claim 1, characterized in that: In step (3), the nut tightening torque is calculated by the relationship between the bolt tightening torque and the normal pressure on the rubber ball, as shown in formula (III): In formula (III), M is the tightening torque of the nut, F is the normal pressure on the rubber ball, d2 is the pitch diameter of the threads at both ends of the compression threaded rod, λ is the thread lead angle, t is the thread pitch at both ends of the compression threaded rod, f is the friction coefficient between the adjusting nut and the upper supporting cylindrical sleeve, ρ is the equivalent friction angle of the helical pair, β is the thread half angle, f' is the friction coefficient between the helical pairs, R is the outer radius of the nut bearing surface, and r is the inner radius of the nut bearing surface.

Images