CN103278305A - Wind channel model tail support rod structure capable of actively damping vibration - Google Patents

Abstract

The present invention provides a pneumatic model tail strut structure that uses piezoelectric stacks for active vibration reduction. The front end of the tail strut is used to install the model, and a strain gauge balance is installed inside the model. The rear end of the tail strut passes through a lock nut. fixed on the stand. The tail strut is divided into a front section of the tail strut and a rear section of the tail strut that are connected through the hole shaft, and a pair of symmetrically connected flanges are respectively located on the front section of the tail strut and the rear section of the tail strut at the joint, There are four positioning slots with an angle of 90° between the two flanges respectively, and piezoelectric stacks are installed between the positioning slots. Compared with the traditional passive vibration damping structure, the present invention has the advantages of high frequency and fast response due to the use of intelligent piezoelectric material as the vibration damping element, which can realize effective control of vibration, and the small size of the entire vibration damping part will not affect the The flow field of the test model is affected, the structure design is simple, it can be applied to the vibration reduction of tail strut structures of different sizes, and it has good usability and maintainability.

Description

A wind tunnel model tail strut structure for active vibration reduction

technical field

The invention relates to a wind tunnel model strut structure, in particular to an active damping wind tunnel model tail strut structure.

Background technique

In a conventional wind tunnel force test, the wind tunnel test model and its fixtures constitute a cantilever beam system. The cantilever beam system consists of a test model, a strain gauge balance, a tail rod and a bracket. The test model is located at the front end, the strain gauge balance is fixed in the model, the model is installed on the slender tail rod, and the tail rod is fixed on the bracket. superior. In this way, during the wind tunnel test, the model is subjected to unsteady aerodynamic force, and vibrates together with the balance, tail strut and support. This kind of vibration not only affects the accuracy of the test data, but also easily causes the support system to resonate because the aerodynamic force is a broadband excitation load. If the vibration time is too long, the amplitude is too large, and the frequency is too high, the model will be damaged, or even the tail strut will be broken, which will bring serious safety hazards to the test, hinder the smooth completion of the wind tunnel test, and affect the research and development of the aircraft. Therefore, how to effectively suppress the vibration characteristics of the tail strut during the blowing process is a key problem that needs to be solved urgently in the wind tunnel test.

Starting from the cause of the vibration, two solutions can be proposed: one is to improve the aerodynamic characteristics of the wind tunnel, that is, to improve the excitation source by changing the flow field of the wind tunnel or to obtain excellent aerodynamic characteristics by modifying the shape of the model to avoid reaching the support system The resonant frequency so as to achieve the purpose of reducing vibration. Obviously, it is very difficult to improve the incentive source, the economic cost is high and the applicability is not strong, and the modification of the model shape is contrary to the purpose of the experiment. The second is to improve the model support structure, by improving the dynamic characteristics of the model support structure and improving its damping characteristics to achieve the purpose of vibration reduction. Structural improvement mainly achieves the purpose of reducing vibration by improving structural quality, stiffness or increasing damping. However, improving the quality or rigidity of the structure will inevitably increase its size. For example, the cross-sectional size of the tail strut and support is equal to or larger than the size of the test model, which will inevitably bring disturbance to the flow field and affect the accuracy of the test data. Improving structural damping means adding damping material to the structure to absorb vibration energy through the damping material to achieve the vibration reduction effect, but adding damping material will inevitably lead to excessive structure size and unsatisfactory vibration reduction effect. The above methods are all traditional passive vibration reduction methods.

The emergence of piezoelectric materials has enabled the realization of active vibration reduction technology. Piezoelectric material means that when an external load acts on the material, charges with opposite signs will be generated on the surface of the material. This phenomenon is called the positive piezoelectric effect of piezoelectric materials. The positive piezoelectric effect shifts the charge center inside the material to generate polarization, and the charge density generated by the polarization is proportional to the size of the external load. On the contrary, when a certain voltage is applied to the piezoelectric material body, the piezoelectric body will produce a corresponding driving force and deformation. This phenomenon is called the inverse piezoelectric effect of the piezoelectric material, and the inverse piezoelectric effect of the piezoelectric material can be used to make Various piezoelectric actuators. At present, piezoelectric materials with a wide range of applications are piezoelectric ceramics. Piezoelectric ceramics have the advantages of fast response speed, wide frequency range, and large driving force, and are a good choice for active vibration reduction. In terms of structural form, there are two types of piezoelectric actuators: wafer structure and stacked structure. Both structural forms of piezoelectric actuators can be used for vibration reduction. In application, the wafer structure is to bond one side of the piezoelectric wafer to the structure or make a double wafer structure, and use the eccentric force generated on the wafer to apply a counter moment to the structure to achieve the purpose of vibration reduction, and its driving force and displacement are small. The piezoelectric stack structure is to stack piezoelectric sheets and encapsulate them in a movable metal shell at the end. The displacement and force accumulation of each piezoelectric sheet can generate large output force and displacement.

Great achievements have also been made in the research of piezoelectric actuators in China, but most of the research on using piezoelectric actuators for vibration reduction is concentrated in the experimental stage, and the research focuses on using piezoelectric sheets to reduce the vibration of cantilever beams. , that is, the piezoelectric sheet is bonded to one side of the cantilever beam, and the purpose of vibration reduction is achieved through the eccentric force generated by the piezoelectric sheet. The research object has small stiffness and low frequency, and the bending moment generated during the vibration process is also small, so the content mostly focuses on the establishment of analysis model and position optimization method. However, there are no relevant literature reports on the application of piezoelectric materials, especially piezoelectric stacks, to vibration reduction in engineering with high frequency and large external driving force. Internationally, countries that have done more research on piezoelectric actuators are mainly the United States, Germany and Japan, and Germany is at the forefront in the research on active vibration reduction of tail struts in wind tunnel tests using piezoelectric stack actuators. . The German ERAS company and the European Transonic Wind Tunnel Company first began to use piezoelectric stacks for active vibration reduction of the tail strut support system (Journal: AIAA-2001-0610, 2001, page number: 1–8), the principle is By analyzing the dynamic characteristics of the tail strut and improving the local structure to install the piezoelectric stack, under the excitation of the voltage, the inverse piezoelectric effect of the piezoelectric stack is used to generate a moment opposite to the vibration of the tail strut, so as to achieve The purpose of active vibration reduction. In the study, the connection between the strain gauge balance and the front end of the tail rod was designed as the active control interface of the piezoelectric stack. The piezoelectric stack was connected to the balance and the tail rod respectively. After the connection, the entire piezoelectric stack was located in the test model. Because the active damping structure needs to connect the piezoelectric stack structure with the strain gauge balance, not only the design of the strut structure but also the structure of the balance must be modified during application; in addition, the entire piezoelectric stack active control surface In the model, affected by the size and structure of the piezoelectric stack, the size of the model, balance and tail rod is required to be relatively large, so this structure is suitable for vibration reduction of large-scale or full-scale blower models; finally, the piezoelectric stack actively The vibration damping structure is complex, and the entire piezoelectric stack structure is installed in the model, which makes it very inconvenient to install and maintain during use, which is also the disadvantage of this structure.

Contents of the invention

The present invention provides an aerodynamic model tail strut structure using piezoelectric stacks for active vibration reduction, which can effectively suppress the main vibration modes, and can be applied to the vibration reduction of tail strut structures of different sizes. Easy to disassemble and maintain.

The front end of the tail rod of the present invention is used to install the model, and the rear end of the tail rod is fixed on the support by a lock nut. It is characterized in that: the tail rod is divided into a front part of the tail rod and a At the rear section of the tail strut, there are a pair of symmetrically connected flanges at the joint, which are respectively located on the front section of the tail strut and the rear section of the tail strut. There are four positioning grooves with an angle of 90° on each of the two flanges. , a piezoelectric stack is installed between the positioning slots.

As a further improvement, the symmetrically connected flanges are connected by compression bolts and nuts, and there are washers between the nuts and the flanges.

As a further improvement, the piezoelectric stack is fixed on the flange at the rear section of the tail strut by fixing screws.

The beneficial effects of the present invention are:

1. Compared with the traditional passive vibration damping structure, due to the use of intelligent piezoelectric material as the vibration damping element, it has the advantages of high frequency and fast response, which can realize effective control of vibration, and the small size of the entire vibration damping part will not affect The flow field of the test model has an influence;

2. The damping structure installs a piezoelectric stack on the top, bottom, left and right of the cross-section of the tail strut, which can effectively suppress the main vibration modes and meet the needs of engineering applications;

3. The design of the structure is simple. Since the vibration-damping surface of the piezoelectric stack is located at the rear end of the entire tail strut, the strain gauge balance does not need to be modified, so it can be applied to the vibration reduction of tail strut structures of different sizes;

4. The vibration damping structure does not need to disassemble the test model, strain gauge balance, etc. during the installation/maintenance process, and has good openness, good usability and maintainability.

Description of drawings

Fig. 1 is a front view of the present invention;

Fig. 2 is a top view of the present invention;

Figure 3 is a 2-fold enlarged view of the partial view of I in Figure 1;

Fig. 4 is a 2 times enlarged view of the A-A sectional view in Fig. 1;

Figure 5 is a 2-fold enlarged view of the partial view of II in Figure 2;

Figure 6 is a sectional view of the front section of the tail strut;

Figure 7 is a sectional view of the rear section of the tail strut;

Fig. 8 is a cross-sectional view of B-B plane in Fig. 6;

Fig. 9 is a sectional view of plane C-C in Fig. 7;

Fig. 10 is a cross-sectional view of D-D plane in Fig. 7;

Fig. 11 is the E-E plane sectional view among Fig. 9;

Figure 12 is an outline view of the piezoelectric stack.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

Fig. 1～Fig. 5 is the assembly relationship of the whole tail strut damping structure, Fig. 1 is the front view of the present invention, Fig. 2 is the top view of the present invention, model 1 is housed on the tail strut front section 3 of the present invention, and strain relief is housed inside the model 1 Instrument balance 2, the rear section 5 of the tail support rod is fixed on the support 6 through the lock nut 7, and it is characterized in that: the front section 3 of the tail support rod and the rear section 5 of the tail support rod are connected through the hole shaft, and at the joint A pair of symmetrically connected flanges are respectively located on the front section 3 of the tail strut and the rear section 5 of the tail strut. There are four positioning grooves with an angle of 90° between the two flanges. Electric stack 4.

Figure 3 is a 2-fold enlarged view of the partial view of I in Figure 1, Figure 4 is a 2-fold enlarged view of the A-A section view in Figure 1, and Figure 5 is a 2-fold enlarged view of the partial view of II in Figure 2, the two flanges They are connected with compression bolts 8 and nuts 9, and there is a washer 10 between the nuts 9 and the flange. The piezoelectric stack 4 is fixed on the flange of the rear section 5 of the tail strut by fixing screws 11 .

Figures 6 to 12 show the structural forms of the main components.

Installation technique of the present invention is:

1) Fit the front part of the tail rod and the rear part of the tail rod through the shaft hole to form a whole rod.

2) Put the front ball heads of the 4 piezoelectric stacks on the positioning grooves of the flanges in the front section of the tail strut with a mutual angle of 90°, and install the rear end of the piezoelectric stack on the rear section of the tail strut with a mutual angle of 90° It is fixed in the positioning slot of the tail support rod with fixing screws on the flange plate of the rear section of the tail strut.

3) Use compression bolts to pass through the bolt holes on the flanges of the front section of the tail strut and the rear section of the tail strut, and compress the piezoelectric stack between the two flanges with washers and compression nuts.

4) Install the strain gauge balance on the front end of the front section of the tail boom.

5) Connect the test model to the strain gauge balance.

6) Finally, fix the entire tail strut structure on the support with lock nuts.

The materials of the parts are as follows: the material used for the front part of the tail strut is No. 20 steel; the material used for the rear part of the tail strut is No. 20 steel; the material used for the support is No. 20 steel; Strengthening, the hardness after heat treatment is HRC31~35; the material used for the lock nut is 30CrMoSi steel, which is strengthened by heat treatment, and the hardness after heat treatment is HRC31~35; nuts, washers, and fixing screws are all standard parts and can be purchased in the market ; The test model and the strain gauge balance are finished parts, which are the existing parts when the blowing test is carried out; market to buy.

There are many specific application approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principles of the present invention. Improvements should also be regarded as the protection scope of the present invention.

Claims (3)

1. the wind tunnel model support sting structure of an active damping, the support sting front end is used for dress model (1), the support sting rear end is fixed on the bearing (6) by set nut (7), it is characterized in that: described support sting is divided into support sting leading portion (3) and the support sting back segment (5) that is connected by the hole axle, there is a pair of symmetrical flange connecting dish to lay respectively on support sting leading portion (3) and the support sting back segment (5) in the junction, it is 90 ° locating slot that four mutual angles are arranged respectively on two ring flanges, and piezoelectric stack (4) is installed between locating slot.

2. the wind tunnel model support sting structure of active damping according to claim 1 is characterized in that: be connected with nut (9) with hold-down bolt (8) between the described symmetrical flange connecting dish, packing ring (10) is arranged between nut (9) and the ring flange.

3. the wind tunnel model support sting structure of active damping according to claim 1, it is characterized in that: described piezoelectric stack (4) is fixed on the ring flange of support sting back segment (5) by gib screw (11).

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