A high frequency dynamic stiffness measuring device

Abstract

The application relates to a high-frequency dynamic stiffness measuring device, which comprises a frame, an inertial mass assembly arranged at the bottom of the frame, a preloading assembly connected to the top of the frame, and a high-frequency excitation assembly connected to the frame and located between the inertial mass assembly and the preloading assembly; the preloading assembly comprises an air chamber connected to the top of the frame and an air spring communicated with the air chamber and facing the inertial mass assembly; the high-frequency excitation assembly comprises a piezoelectric exciter abutting against the air spring and an elastic support assembly for fixing the piezoelectric exciter on the frame; the device further comprises an acceleration sensor arranged on the piezoelectric exciter and a force sensor arranged between the piezoelectric exciter and the inertial mass assembly. The device has the characteristics of high preloading adjustment flexibility, strong test universality, high detection accuracy and suitability for high-frequency detection.

Description

Technical Field

[0001] This application relates to the field of dynamic stiffness measurement, and in particular to a high-frequency dynamic stiffness measurement device. Background Technology

[0002] Dynamic stiffness is a physical quantity that describes a structure's ability to resist elastic deformation under dynamic loads. Its measurement standard is the dynamic force required to induce a unit amplitude of vibration. In engineering applications, dynamic stiffness directly affects the working accuracy of mechanical systems, such as machine tool cutting stability and gear shaft transmission error control.

[0003] Dynamic stiffness measuring devices simulate the actual working conditions of a workpiece by applying a predetermined static preload (preload) and a superimposed dynamic excitation load, and measure its response to calculate the dynamic stiffness value. Dynamic stiffness itself is a function of frequency, and the dynamic stiffness values ​​of structures differ significantly at different frequencies. Therefore, the frequency of the exciter directly determines the accuracy and validity of the dynamic stiffness measurement results. However, traditional dynamic stiffness measuring devices have the following inherent and insurmountable limitations: Insufficient Frequency Upper Limit: Traditional electromagnetic vibrators, due to their operating principle relying on electromagnetic induction and the inertia of moving components, have a physical upper limit to their operating frequency range. Typically, the effective output frequency of commercial electromagnetic vibrators is limited to 5000Hz to 7000Hz. Even with special designs, their high-frequency output force decays sharply, and the waveform is severely distorted, making it impossible to provide a stable and sufficiently powerful excitation signal at higher frequencies (e.g., 10000Hz to 20000Hz). This directly results in existing measurement devices being unable to cover the high-frequency dynamic stiffness testing requirements above 10000Hz.

[0004] High-frequency resonance and structural limitations: The moving coil and connecting parts of the electromagnetic exciter will generate mechanical resonance at high frequencies, which will seriously interfere with the purity of the excitation signal during high-frequency excitation and introduce significant measurement errors. At the same time, in order to drive a relatively large moving mass, its size and weight are usually large, and the overall system rigidity is low, which further limits its high-frequency response characteristics.

[0005] Therefore, there is an urgent need in this field for a dynamic stiffness measurement device that can break through the existing frequency bottleneck and achieve higher frequency bands, especially one that can stably and reliably cover up to 20,000 Hz, in order to fill the gap in existing technology and meet the urgent needs of high-end equipment R&D and precision component testing. Utility Model Content

[0006] The purpose of this application is to address the shortcomings of existing technologies and propose a high-frequency dynamic stiffness measuring device with wide frequency coverage, strong anti-interference ability, and high measurement accuracy.

[0007] The high-frequency dynamic stiffness measuring device designed in this application includes: a frame, an inertial mass assembly disposed at the bottom of the frame, a preload assembly connected to the top of the frame, and a high-frequency excitation assembly connected to the frame and located between the inertial mass assembly and the preload assembly. The preloaded component includes an air chamber connected to the top of the frame and an air spring communicating with the air chamber and toward the inertial mass component. The high-frequency excitation assembly includes a piezoelectric vibrator held against an air spring and an elastic support assembly that fixes the piezoelectric vibrator to a frame; It also includes an acceleration sensor disposed on the piezoelectric vibrator and a force sensor disposed between the piezoelectric vibrator and the inertial mass assembly.

[0008] More specifically, the elastic support assembly includes: an adjusting ring connected to the frame, a plurality of elastic connectors fixed to the adjusting ring, and the piezoelectric vibrator fixed between the plurality of elastic connectors.

[0009] More specifically, the elastic connector includes a vertical plate fixed to the adjusting ring, a lower spring plate connected to the side of the vertical plate near the adjusting ring, and an upper spring plate connected to the side of the vertical plate away from the adjusting ring. The piezoelectric vibrator is fixed between the upper spring plate and the lower spring plate.

[0010] More specifically, the adjusting ring is connected to the frame via a first height adjusting mechanism.

[0011] More specifically, several of the aforementioned elastic connectors are evenly distributed on the adjusting ring.

[0012] More specifically, the inertial mass assembly includes an inertial mass block and a support plate disposed below the inertial mass block and connected to the bottom of the frame.

[0013] More specifically, the support plate is connected to the bottom of the frame via a second height adjustment mechanism.

[0014] More specifically, a first shock absorber is provided between the support plate and the inertial mass block.

[0015] More specifically, the first shock absorber is an elastic vibration isolation pad.

[0016] More specifically, the frame includes a frame body, a frame bottom plate disposed at the bottom of the frame body, a frame top plate disposed at the top of the frame body, and a frame middle plate disposed in the middle of the frame body. The inertial mass component is disposed on the frame bottom plate, the preload component is disposed under the frame top plate, and the high-frequency excitation component is disposed on the frame middle plate.

[0017] This application has the following beneficial effects: 1. This application employs a high-frequency excitation technology based on the inverse piezoelectric effect. The "zero inertia" characteristic of piezoelectric materials eliminates the risk of connection failure under high-frequency vibration, enabling the stable generation of an excitation frequency of 20,000 Hz. This solves the problem of poor connection reliability at high frequencies caused by the large inertia of moving parts in existing electromagnetic exciters, and fills the technological gap in ultra-high frequency dynamic stiffness measurement.

[0018] 2. This application employs an elastic support structure to connect the high-frequency excitation assembly, ensuring that the vibration force axis of the piezoelectric exciter is aligned with the center of the workpiece under test, thus reducing lateral vibration interference. The adjusting ring, in conjunction with the first height adjustment mechanism, can precisely adjust the position of the exciter to accommodate workpieces of different sizes. At the same time, the elastic support effectively buffers high-frequency vibration stress, improving the reliability of the exciter connection and the stability of the vibration direction.

[0019] 3. This application employs a preloading mechanism combining an air chamber and an air spring. By adjusting the internal air pressure, the preload force can be continuously and precisely adjusted. Compared to traditional mechanical preloading methods, this is more convenient to operate and can adapt to the preload requirements of different test pieces. The air spring combines preload application and high-frequency vibration isolation functions. Its internal gas volume buffer design avoids instantaneous pressure fluctuations caused by exciter vibration, ensuring the stability of the preload force under high-frequency conditions. Simultaneously, it absorbs vibration energy, reduces vibration transmission between the exciter and the frame top plate, isolates external interference, and ensures the accuracy of force and acceleration detection at high frequencies.

[0020] The high-frequency dynamic stiffness measuring device provided in this application, through innovative design and structural optimization of core components, breaks through the bottlenecks of existing technologies in high-frequency measurement, significantly improving the stability, accuracy, and applicability of dynamic stiffness testing. It provides a revolutionary solution for ultra-high frequency dynamic characteristic testing in fields such as aerospace and precision manufacturing. Attached Figure Description

[0021] Figure 1 This is a three-dimensional schematic diagram of the high-frequency dynamic stiffness measuring device in this application.

[0022] Figure 2 This is a front sectional view of the high-frequency dynamic stiffness measuring device in this application.

[0023] Figure 3 This is a three-dimensional schematic diagram of the elastic support component in this application.

[0024] Figure 4 This is a three-dimensional schematic diagram of the elastic connector in this application.

[0025] In the diagram: 100, Frame; 101, Top plate of the frame; 102, Middle plate of the frame; 103, Bottom plate of the frame; 104, Frame body; 200, Preload assembly; 201, Air chamber; 202, Air spring; 300, High-frequency excitation assembly; 301, Piezoelectric vibrator; 310, Elastic support component; 311, Adjusting ring; 312, Screw; 313, First height adjustment mechanism; 320, Spring assembly; 321, Fixed base; 322, Vertical plate; 323, Lower spring plate; 324, Upper spring plate; 400, Inertial mass assembly; 401, Inertial mass block; 402, Elastic vibration isolation pad; 403, Support plate; 500, Workpiece to be tested; 501, Accelerometer; 502, Force sensor. Detailed Implementation

[0026] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0029] The main purpose of this application is to provide a dynamic stiffness measurement device that can break through the existing frequency bottleneck and achieve higher frequency bands, especially a dynamic stiffness measurement device that can stably and reliably cover up to 20,000 Hz, so as to fill the gap in the existing technology and meet the urgent needs of high-end equipment research and development and precision component testing.

[0030] Traditional dynamic stiffness measurement devices typically employ electromagnetic exciters, based on the laws of electromagnetic induction (Faraday's law) and the Ampere force principle (the principle that a current-carrying conductor experiences a force in a magnetic field). They utilize the superposition of alternating and constant magnetic fields to polarize a moving armature within the magnetic field, causing the armature to experience an excitation force due to the alternating magnetic force. The moving component of an electromagnetic exciter is usually an excitation coil (moving coil). However, high-frequency vibration poses a significant challenge to the reliability of the moving coil's connection, and existing electromagnetic exciters struggle to maintain a stable connection under high-frequency vibration. To achieve dynamic stiffness detection in the high-frequency range, this application employs a piezoelectric high-frequency exciter based on the inverse piezoelectric effect of piezoelectric materials. The piezoelectric material exhibits almost "zero inertia" micro-deformation, and the device has no additional moving parts, exhibiting high-frequency response and high rigidity. The excitation force is directly generated through the micro-expansion and contraction of the piezoelectric material (such as a ceramic wafer), fundamentally eliminating the need for large-inertia moving parts (such as the moving coil structure) required by electromagnetic exciters.

[0031] like Figure 1 As shown, the high-frequency dynamic stiffness measuring device designed in this application has a vertical configuration. All device components are set within a vertical frame 100. The frame 100 includes a frame body 104, a frame base plate 103 at the bottom of the frame body 104, a frame top plate 101 at the top of the frame body 104, and a frame middle plate 102 in the middle of the frame body 104. Specifically, an inertial mass component 400 is set on the frame base plate 103, a preload component 200 is suspended and connected on the frame top plate 101, and a high-frequency excitation component 300 is set on the frame middle plate 102. A through hole is opened in the frame middle plate 102, and the high-frequency excitation component 300 is fixed above the through hole and faces the through hole. When it is necessary to measure the dynamic stiffness, the workpiece 500 to be measured is placed in the through hole, and the two ends of the workpiece 500 are respectively held against the inertial mass component 400 and the high-frequency excitation component 300.

[0032] In this application, the high-frequency excitation assembly 300 includes a piezoelectric exciter 301 and an elastic support assembly 310 that fixes the piezoelectric exciter 301 to the frame plate 102. Figure 3 and Figure 4As shown, the elastic support assembly 310 includes an adjusting ring 311 connected to the frame plate 102 and several elastic connectors 320 fixed to the adjusting ring 311. The adjusting ring 311 is connected to the frame plate 102 via a first height adjustment mechanism 313 and screws 312. The first height adjustment mechanism 313 can be an adjusting stud, which can be used to change the distance between the adjusting ring 311 and the frame plate 102. The elastic connectors 320 include a vertical plate 322 fixedly connected (e.g., welded, bolted, etc.) to the adjusting ring 311 via a fixing seat 321. An upper spring plate 324 and a lower spring plate 323 are fixedly connected to the vertical plate 322. The piezoelectric vibrator 301 is fixed between the upper spring plate 324 and the lower spring plate 323. To ensure the reliability of the piezoelectric vibrator 301 connection and the stability of the vibration force axis, several elastic connectors 320 are symmetrically and evenly distributed on the adjusting ring 311. A through hole is provided on the frame plate 102. The piezoelectric vibrator 301 is fixed to the through hole by the elastic support 310. The moving part of the piezoelectric vibrator 301 faces the through hole. Preferably, the vibration force axis of the piezoelectric vibrator 301 passes through the center of the through hole.

[0033] The piezoelectric vibrator 301 can generate a vibration frequency of 20,000 Hz. To meet the requirements of stable preload adjustment and high-frequency vibration isolation in high-frequency scenarios, and to ensure structural adaptability and ultimately guarantee the accuracy of high-frequency dynamic stiffness measurement, this application provides a preload assembly 200 between the piezoelectric vibrator 301 and the frame top plate 101. The preload assembly 200 includes an air chamber 201 fixedly connected to the frame top plate 101. The air chamber 201 faces the frame middle plate 102 and is connected to an air spring 202, which rests against the piezoelectric vibrator 301. The gas in the air spring 202 is connected to the gas in the air chamber 201. The preload force of the air spring 202 depends on the internal air pressure. The air chamber 201 can increase the gas volume, making the air pressure distribution more uniform and providing a larger buffer space for air pressure changes, thus avoiding instantaneous pressure fluctuations caused by vibrator vibration. This design can ensure the stability of the preload force. By adjusting the overall air pressure of the air chamber 201 and the air spring 202, continuous and precise adjustment of the preload force can be achieved, adapting to the preload requirements of different test pieces. The operation is more convenient and precise than traditional mechanical preload. The air spring 202 serves as both the preload application structure and a stable vibration isolation structure. When the high-frequency piezoelectric exciter 301 is working, the air spring 202 absorbs some of the vibration energy transferred to the air chamber 201, reducing the transmission of exciter vibration to the frame top plate 101. Simultaneously, it isolates the exciter from external vibration interference, preventing any impact on the accuracy of force and acceleration detection at high frequencies.

[0034] This application adopts a vertical configuration. To construct a stable inertial reference and block vibration interference, the inertial mass assembly 400 is mounted on the frame base plate 103 at the bottom of the device. The frame base plate 103 is the part of the device with the least vibration, and its stability reduces the additional vibration of the inertial mass assembly 400 itself. The inertial mass assembly 400 includes a support plate 403 connected to the frame base plate 103 and an inertial mass block 401 mounted on the support plate 403. To enhance the vibration isolation and interference suppression effect, an elastic vibration isolation pad 402 is provided between the support plate 403 and the inertial mass block 401. The support plate 403 is connected to the frame base plate 103 through a second height adjustment mechanism, which can also be an adjustment stud. The adjustment stud can be used to change the distance between the inertial mass block 401 and the frame base plate 103, thereby providing sufficient placement space for test pieces of different sizes and models.

[0035] The embodiments of this application have been described in detail above, but this application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this application, and these variations still fall within the protection scope of this application.

Claims

1. A high-frequency dynamic stiffness measuring device, characterized in that, include: The frame, an inertial mass assembly disposed at the bottom of the frame, a preload assembly connected to the top of the frame, and a high-frequency excitation assembly connected to the frame and located between the inertial mass assembly and the preload assembly; The preloaded component includes an air chamber connected to the top of the frame and an air spring communicating with the air chamber and toward the inertial mass component. The high-frequency excitation assembly includes a piezoelectric vibrator held against an air spring and an elastic support assembly that fixes the piezoelectric vibrator to a frame; It also includes an acceleration sensor disposed on the piezoelectric vibrator and a force sensor disposed between the piezoelectric vibrator and the inertial mass assembly.

2. The high-frequency dynamic stiffness measuring device according to claim 1, characterized in that, The elastic support assembly includes: an adjusting ring connected to the frame, a plurality of elastic connectors fixed to the adjusting ring, and the piezoelectric vibrator fixed between the plurality of elastic connectors.

3. The high-frequency dynamic stiffness measuring device according to claim 2, characterized in that, The elastic connector includes a vertical plate fixed to the adjusting ring, a lower spring plate connected to the side of the vertical plate near the adjusting ring, and an upper spring plate connected to the side of the vertical plate away from the adjusting ring. The piezoelectric vibrator is fixed between the upper spring plate and the lower spring plate.

4. The high-frequency dynamic stiffness measuring device according to claim 3, characterized in that, The adjusting ring is connected to the frame via a first height adjusting mechanism.

5. The high-frequency dynamic stiffness measuring device according to claim 2, characterized in that, Several of the aforementioned elastic connectors are evenly distributed on the adjusting ring.

6. The high-frequency dynamic stiffness measuring device according to claim 1, characterized in that, The inertial mass assembly includes an inertial mass block and a support plate disposed below the inertial mass block and connected to the bottom of the frame.

7. The high-frequency dynamic stiffness measuring device according to claim 6, characterized in that, The support plate is connected to the bottom of the frame via a second height adjustment mechanism.

8. The high-frequency dynamic stiffness measuring device according to claim 6, characterized in that, A first shock absorber is provided between the support plate and the inertial mass block.

9. The high-frequency dynamic stiffness measuring device according to claim 8, characterized in that, The first shock absorber is an elastic vibration isolation pad.

10. The high-frequency dynamic stiffness measuring device according to claim 1, characterized in that, The frame includes a frame body, a frame bottom plate at the bottom of the frame body, a frame top plate at the top of the frame body, and a frame middle plate in the middle of the frame body. The inertial mass component is disposed on the frame bottom plate, the preload component is disposed under the frame top plate, and the high-frequency excitation component is disposed on the frame middle plate.

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