CN110160732B - Friction force adjustable device and friction force adjustable method for flutter test - Google Patents

Abstract

The invention provides an adjustable friction force device and an adjustable friction force method for flutter test. The device includes a base, a spring sheet with bending stiffness, a plurality of friction adjustment rings with different materials, and a plurality of adjustment rings with different heights. The spacer block and the fastening assembly, the connecting end of the bending stiffness spring sheet is fixedly arranged on the base, the open end of the bending stiffness spring sheet has a first accommodating cavity and a second accommodating cavity, the first accommodating cavity is used for accommodating the rudder shaft, and more A plurality of friction adjusting rings are alternately arranged in the first accommodating cavity and sleeved on the rudder shaft, a plurality of adjusting pads are alternately arranged in the second accommodating cavity to adjust the size of the first accommodating cavity, and the fastening components are used to adjust the bending stiffness The second accommodating cavity of the spring sheet is locked, and the adjustable friction force device adjusts the friction force of the rotational degree of freedom of the rudder shaft by adjusting the material of the friction adjusting ring and/or adjusting the height of the pad. The technical solution of the present invention is applied to solve the technical problem that the influence law of friction force on the flutter characteristic cannot be obtained in the prior art.

Description

Adjustable friction force device and adjustable friction force method for flutter test

technical field

The invention relates to the technical field of nonlinear flutter test, in particular to an adjustable friction force device and an adjustable friction force method for flutter test.

Background technique

The rudder is an important control surface on the missile. When studying the flutter characteristics of the rudder surface, the study of the friction nonlinearity of the rudder surface structure is very important. The effect of friction on the flutter velocity and limit cycle characteristics of the structure can be obtained by numerical simulation. In the study of model flutter, how to increase the flutter speed by increasing the friction is a difficult point. However, due to the complexity of friction nonlinearity, it is difficult to accurately simulate the friction force of the friction structure during the flutter test, so the influence of the friction force on the flutter characteristics cannot be obtained.

SUMMARY OF THE INVENTION

The invention provides an adjustable friction force device and an adjustable friction force method for flutter test, which can solve the technical problem that the influence law of friction force on flutter characteristics cannot be obtained in the prior art.

According to an aspect of the present invention, an adjustable friction force device for flutter test is provided, the adjustable friction force device includes: a base; The connection end of the stiffness spring sheet is fixedly arranged on the base, and the open end of the bending stiffness spring sheet has a first accommodating cavity and a second accommodating cavity which are communicated. The first accommodating cavity is used for accommodating the rudder shaft, and the length of the bending stiffness spring sheet is The direction is perpendicular to the axis direction of the rudder shaft; a plurality of friction adjustment rings with different materials are alternately arranged in the first accommodating cavity and sleeved on the rudder shaft; a plurality of adjustment pads with different heights, many The adjustment spacers are alternately arranged in the second accommodating cavity to adjust the size of the first accommodating cavity; the fastening assembly is arranged at the open end of the bending stiffness spring sheet, and the fastening assembly is used to adjust the first accommodating cavity of the bending stiffness spring sheet. The two accommodating chambers are locked; wherein, the adjustable friction force device adjusts the friction force of the rotational degree of freedom of the rudder shaft by adjusting the material of the friction adjusting ring and/or adjusting the height of the pad.

Further, the bending stiffness spring sheet includes a bending stiffness connecting section, a first arc-shaped clamping section, a second arc-shaped clamping section, a first clamping section and a second clamping section, one end of the first arc-shaped clamping section. and one end of the second arc-shaped clamping segment are connected to the bending rigidity connecting segment, the first arc-shaped clamping segment and the second arc-shaped clamping segment together form a first accommodating cavity, and the other end of the first arc-shaped clamping segment One end is connected to the first clamping segment, the other end of the second arc-shaped clamping segment is connected to the second clamping segment, and the first clamping segment and the second clamping segment are arranged in parallel to form a second accommodating cavity.

Further, the fastening assembly includes a screw and a nut, and the screw passes through the first clamping segment and the second clamping segment respectively and is matched with the nut to lock the second accommodating cavity of the bending stiffness spring sheet.

Further, the material of the friction adjusting ring includes polytetrafluoroethylene, phenolic plastic or bronze material.

Further, the structural shape of the adjustment pad includes a circle or a square, the adjustment pad has a central through hole, the adjustment pad is arranged between the first clamping section and the second clamping section, and the screws pass through the first clamping section in turn. segment, the central through hole of the adjusting spacer and the second clamping segment and are matched with the nut to connect the bending stiffness spring sheet with the rudder shaft.

Further, the height of the adjustment pad is inversely proportional to the frictional force of the rotational degree of freedom of the rudder shaft.

According to yet another aspect of the present invention, there is provided an adjustable friction force method for flutter testing, the adjustable friction force method using the adjustable friction force device as described above.

Further, the method for adjusting the friction force includes: step 1, installing the friction adjustment ring on the rudder shaft; step 2, setting the bending stiffness spring sheet on the outside of the friction adjustment ring, so that both the friction adjustment ring and the rudder shaft are located in the bending direction. In the first accommodating cavity of the stiffness spring piece; step 3, fix the bending stiffness spring piece on the base; step 4, insert the adjusting pad into the second accommodating cavity of the bending stiffness spring piece, and tighten the The bending stiffness spring piece is connected with the rudder shaft; Step 5, measure the friction force of the rotational degree of freedom of the rudder shaft; Step 6, change the thickness of the adjusting pad and the material of the friction adjusting ring, repeat steps 1 to 5 to measure the rotation of the rudder shaft respectively The friction force of the degree of freedom, and record and store the measurement results; Step 7, during the flutter test, select the combined state of the adjustment pad and the friction adjustment ring according to the record of the measurement results to carry out the test.

By applying the technical solution of the present invention, an adjustable friction force device for flutter test is provided. Precise control of friction in the rotational (torsional) degrees of freedom of the rudder shaft. Since the rudder surface and the rudder shaft are designed in one piece, by adjusting the material of the friction adjusting ring and/or the thickness of the adjusting pad, the precise control of the friction force of the rotational (torsional) degree of freedom during the flutter test can be achieved, which solves the problem. Influence of friction force on the flutter characteristics of rudder surface structure in flutter test. At the same time, the adjustable friction force device of the present invention can obtain the influence rule of the friction force on the flutter characteristics and limit cycle characteristics by adjusting the magnitude of the friction force.

Description of drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention, constitute a part of the specification, are used to illustrate the embodiments of the invention, and together with the description, serve to explain the principles of the invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 shows the front view of the adjustable friction force device for flutter test provided according to a specific embodiment of the present invention;

Figure 2 shows a top view of the adjustable friction device provided in Figure 1 for flutter testing;

FIG. 3 shows a cross-sectional view of the adjustable friction device provided in FIG. 1 for flutter testing.

Wherein, the above-mentioned drawings include the following reference signs:

10, the base; 20, the bending stiffness spring sheet; 20a, the first accommodating cavity; 20b, the second accommodating cavity; 21, the bending stiffness connecting section; 22, the first arc-shaped clamping section; holding section; 24, the first clamping section; 25, the second clamping section; 30, the friction adjustment ring; 40, the adjustment pad; 50, the fastening component; 51, the screw; 52, the nut;

Detailed ways

It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the invention unless specifically stated otherwise. Meanwhile, it should be understood that, for the convenience of description, the dimensions of various parts shown in the accompanying drawings are not drawn in an actual proportional relationship. Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the authorized description. In all examples shown and discussed herein, any specific value should be construed as illustrative only and not as limiting. Accordingly, other examples of exemplary embodiments may have different values. It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further discussion in subsequent figures.

As shown in FIG. 1 to FIG. 3 , an adjustable friction force device for flutter test is provided according to a specific embodiment of the present invention. The adjustable friction force device includes a base 10 , a bending stiffness spring plate 20 , a plurality of A friction adjusting ring 30 with different materials, a plurality of adjusting pads 40 and fastening components 50 with different heights, the bending stiffness spring sheet 20 has a connecting end and an open end, and the connecting end of the bending stiffness spring sheet 20 is fixedly arranged on the base 10 Above, the open end of the bending stiffness spring piece 20 has a first accommodating cavity 20a and a second accommodating cavity 20b that communicate with each other. The first accommodating cavity 20a is used for accommodating the rudder shaft 100. The axis directions are perpendicular to each other, a plurality of friction adjusting rings 30 are alternately arranged in the first accommodating cavity 20a and sleeved on the rudder shaft, and a plurality of adjusting pads 40 are alternately arranged in the second accommodating cavity 20b to adjust the first accommodating cavity 20a size, the tightening assembly 50 is arranged at the open end of the bending stiffness spring sheet 20, and the tightening assembly 50 is used to lock the second accommodating cavity 20b of the bending stiffness spring sheet 20; wherein, the adjustable friction force device is adjusted by adjusting the friction The material of the ring 30 and/or the height of the spacer block 40 are adjusted to adjust the frictional force of the rotational freedom of the rudder shaft.

Using this configuration, an adjustable friction force device for flutter test is provided, which can realize the rudder during flutter test by adjusting the material of the friction adjustment ring and/or the thickness of the adjustment pad. Precise control of friction in the rotational (torsional) degrees of freedom of the shaft. Since the rudder surface and the rudder shaft are designed in one piece, by adjusting the material of the friction adjusting ring and/or the thickness of the adjusting pad, the precise control of the friction force of the rotational (torsional) degree of freedom during the flutter test can be achieved, which solves the problem. Influence of friction force on the flutter characteristics of rudder surface structure in flutter test. At the same time, the adjustable friction force device of the present invention can obtain the influence rule of the friction force on the flutter characteristics and limit cycle characteristics by adjusting the magnitude of the friction force.

In the present invention, the material of the friction adjusting ring 30 includes polytetrafluoroethylene, phenolic plastic or bronze material. As a specific embodiment of the present invention, in order to adjust the friction force of the rotational (torsion) degree of freedom of the rudder shaft, it can be achieved by simultaneously adjusting the material of the friction adjusting ring and the thickness of the adjusting pad. As another embodiment of the present invention, the material of the friction adjusting ring can also be kept unchanged, and only the thickness of the adjusting pad can be changed to adjust the friction force of the rotational (torsion) degree of freedom of the rudder shaft. Alternatively, the thickness of the adjusting pad can also be kept unchanged, and only the material of the friction adjusting ring can be changed to adjust the friction force of the rotational (torsion) degree of freedom of the rudder shaft.

Further, in the present invention, as shown in FIG. 3 , the bending stiffness spring piece 20 includes a bending stiffness connecting section 21 , a first arc-shaped clamping section 22 , a second arc-shaped clamping section 23 , and a first clamping section 24 and the second clamping segment 25, one end of the first arc-shaped clamping segment 22 and one end of the second arc-shaped clamping segment 23 are connected to the bending rigidity connecting segment 21, and the first arc-shaped clamping segment 22 and the second arc-shaped clamping segment 22 are connected The other end of the first arc-shaped clamping segment 22 is connected with the first clamping segment 24, and the other end of the second arc-shaped clamping segment 23 is connected with the second clamping segment 23. The segments 25 are connected, and the first clamping segment 24 and the second clamping segment 25 are arranged in parallel to form a second accommodating cavity 20b.

Applying this configuration, by installing the friction adjusting ring 30 on the rudder shaft 100, the friction adjusting ring 30 and the rudder shaft 100 are in transition fit, and the bending stiffness spring sheet 20 is sleeved on the friction adjusting ring 30 to adjust the friction. The ring 30 is located in the first accommodating cavity 20a of the bending stiffness spring piece 20, and the adjusting spacer 40 is arranged in the second accommodating cavity 20b to adjust the size of the first accommodating cavity 20a, thereby adjusting the ring material and/or By adjusting the thickness of the pad, the friction force of the rotational (torsional) degree of freedom of the rudder shaft can be precisely controlled during the flutter test.

Further, in the present invention, in order to realize the fixed connection between the bending stiffness spring sheet and the rudder shaft, the fastening assembly 50 can be configured to include a screw 51 and a nut 52, and the screw 51 passes through the first clamping section 24 and 52 respectively. The second clamping section 25 cooperates with the nut 52 to lock the second accommodating cavity 20 b of the bending stiffness spring piece 20 .

Applying this arrangement, when the friction force measurement of the device is performed, after the material of the friction adjustment ring 30 and the thickness of the adjustment pad 40 are selected, the friction adjustment ring 30 is installed on the rudder shaft 100, and the bending stiffness is adjusted. One end of the spring sheet 20 is sleeved on the friction adjusting ring 30 so that the friction adjusting ring 30 is located in the first accommodating cavity 20a of the bending stiffness spring sheet 20, and one end of the bending stiffness spring sheet 20 is fixed on the base 10 by tightening screws , the adjusting spacer 40 is arranged in the second accommodating cavity 20b to adjust the size of the first accommodating cavity 20a, and is tightened by the screw 51 and the nut 52 to lock the second accommodating cavity 20b of the bending stiffness spring piece 20, thus namely The friction force of the rotational (torsional) degree of freedom of the rudder shaft under the selected material of the friction adjusting ring 30 and the thickness of the adjusting pad 40 can be measured.

Further, in the present invention, the structural shape of the adjusting pad 40 includes a circle or a square, the adjusting pad 40 has a central through hole, and the adjusting pad 40 is arranged between the first snap-on section 24 and the second snap-on section 25 During this time, the screw 51 passes through the first clamping section 24 , the central through hole of the adjusting pad 40 and the second clamping section 25 in sequence and cooperates with the nut 52 to connect the bending stiffness spring piece 20 to the rudder shaft 100 . In addition, in the present invention, the height of the adjusting pad 40 is determined by the required friction force, and an appropriate height can be selected according to the test requirements. The height of the adjustment pad 40 is inversely proportional to the frictional force of the rotational freedom of the rudder shaft.

According to another aspect of the present invention, there is provided an adjustable friction method for flutter testing using an adjustable friction device as described above. The method of adjusting the friction force of the present invention includes: step 1, installing the friction adjusting ring 30 on the rudder shaft; The shafts are all located in the first accommodating cavity 20a of the bending stiffness spring piece 20; in step 3, the bending stiffness spring piece 20 is fixedly arranged on the base 10; Adjust the pad 40, and connect the bending stiffness spring sheet 20 with the rudder shaft through the fastening assembly 50; Step 5, measure the friction force of the rotational freedom of the rudder shaft; Step 6, change the thickness of the adjustment pad 40 and the friction adjustment ring 30 materials, repeat steps 1 to 5, measure the friction force of the rotational degrees of freedom of the rudder shaft respectively, and record and store the measurement results; step 7, during the flutter test, select the adjustment pad 40 and the friction adjustment ring 30 according to the record of the measurement results. The combined state is tested.

By applying the adjustable friction force method of the present invention, the structural design of the rotational (torsion) degree of freedom with adjustable friction force in the flutter test model design is realized, and the nonlinear effect of the rotational (torsional) degree of freedom friction force on the flutter of the rudder surface is realized. Research on the law of influence of characteristics.

In order to have a further understanding of the present invention, the adjustable friction force device and method for flutter test of the present invention will be described in detail below with reference to FIG. 1 to FIG. 3 .

As shown in FIG. 1 to FIG. 3, as a specific embodiment of the present invention, the adjustable friction force device includes a base 10, a bending stiffness spring plate 20, a plurality of friction adjustment rings 30 of different materials, a plurality of For the adjustment pad 40 and the fastening assembly 50, the material of the friction adjustment ring 30 includes polytetrafluoroethylene, phenolic plastic or bronze material. The bending stiffness spring piece 20 includes a bending stiffness connecting section 21, a first arc-shaped clamping section 22, a second arc-shaped clamping section 23, a first clamping section 24 and a second clamping section 25. The first arc-shaped clamping section One end of the segment 22 and one end of the second arc-shaped clamping segment 23 are both connected to the bending rigidity connecting segment 21, and the first arc-shaped clamping segment 22 and the second arc-shaped clamping segment 23 together form a first accommodating cavity 20a, The other end of the first arc-shaped clamping section 22 is connected to the first clamping section 24, the other end of the second arc-shaped clamping section 23 is connected to the second clamping section 25, and the first clamping section 24 and the second clamping section 25 are connected. The connecting segments 25 are arranged in parallel to form the second accommodating cavity 20b. Fastening assembly 50 includes screws 51 and nuts 52 . When adjusting the friction force, mainly follow the steps below.

Step 1, install the friction adjusting ring 30 of the selected material on the rudder shaft 100;

Step 2, the bending stiffness spring sheet 20 is sleeved outside the friction adjusting ring 30, so that the friction adjusting ring 30 and the rudder shaft 100 are both located in the first accommodating cavity 20a of the bending stiffness spring sheet 20;

Step 3, fixing the bending stiffness connecting section 21 of the bending stiffness spring piece 20 on the base 10 by fastening screws;

Step 4: Insert the adjustment spacer 40 of the selected height into the second accommodating cavity 20b of the bending stiffness spring piece 20, and the screw 51 passes through the first clamping section 24, the central through hole of the adjustment spacer 40 and the second clamp in sequence. The connecting section 25 is matched with the nut 52 to connect the bending stiffness spring piece 20 with the rudder shaft 100;

Step 5, measure the frictional force of the rotational degree of freedom of the rudder shaft under the friction adjustment ring 30 of the selected material and the adjustment pad 40 of the selected height;

Step 6, after the measurement is completed, loosen the nut 52, take out the screw 51, the adjustment pad 40 and the friction adjustment ring 30 in the device in turn, change the thickness of the adjustment pad 40 and the material of the friction adjustment ring 30, repeat steps 1 to 5 , respectively measure the friction force of the rotational degrees of freedom of the rudder shaft under the changed friction adjusting ring 30 and the adjusting pad 40, and record and store the measurement results;

Step 7: During the flutter test, select the combined state of the adjusting pad 40 and the friction adjusting ring 30 to carry out the test according to the record of the measurement results.

To sum up, compared with the prior art, the adjustable friction force device for flutter test of the present invention can realize the precise control of the friction force of the rotational (torsion) degree of freedom during the flutter test, and solve the problem of the flutter test. The influence of medium friction on the flutter characteristics of the rudder surface structure. At the same time, the adjustable friction force device of the present invention can obtain the influence rule of the friction force on the flutter characteristics and limit cycle characteristics by adjusting the magnitude of the friction force. Therefore, the present invention has advanced technology and simple and practical test implementation method, which not only greatly reduces the difficulty of model design and the cost of wind tunnel test, but also saves research and development expenses, and has high model practical value.

For ease of description, spatially relative terms such as "on", "over", "on the surface", "above", etc., may be used herein to describe what is shown in the figures. The spatial positional relationship of one device or feature shown to other devices or features. It should be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or features would then be oriented "below" or "over" the other devices or features under other devices or constructions". Thus, the exemplary term "above" can encompass both an orientation of "above" and "below." The device may also be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly.

In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing corresponding components. Unless otherwise stated, the above words have no special meaning and therefore cannot be understood to limit the scope of protection of the present invention.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. An adjustable friction method for flutter test, which uses an adjustable friction device to adjust the friction of a rudder shaft rotation degree of freedom, the adjustable friction device comprising:

a base (10);

the bending stiffness spring piece (20) is provided with a connecting end and an opening end, the connecting end of the bending stiffness spring piece (20) is fixedly arranged on the base (10), the opening end of the bending stiffness spring piece (20) is provided with a first accommodating cavity (20a) and a second accommodating cavity (20b) which are communicated, the first accommodating cavity (20a) is used for accommodating a steering shaft, and the length direction of the bending stiffness spring piece (20) is perpendicular to the axial direction of the steering shaft;

the friction adjusting rings (30) are made of different materials, and the friction adjusting rings (30) are alternately arranged in the first accommodating cavity (20a) and sleeved on the rudder shaft;

a plurality of adjusting cushion blocks (40) with different heights, wherein the adjusting cushion blocks (40) are alternately arranged in the second accommodating cavity (20b) to adjust the size of the first accommodating cavity (20 a);

a fastening member (50), the fastening member (50) being provided at an open end of the bending rigidity spring piece (20), the fastening member (50) being for locking the second accommodation chamber (20b) of the bending rigidity spring piece (20);

the adjustable friction method comprises the following steps:

step one, installing a friction adjusting ring (30) on a rudder shaft;

sleeving the bending rigidity spring piece (20) outside the friction adjusting ring (30) so that the friction adjusting ring (30) and the rudder shaft are both positioned in a first accommodating cavity (20a) of the bending rigidity spring piece (20);

step three, fixedly arranging the bending rigidity spring piece (20) on a base (10);

fourthly, inserting an adjusting cushion block (40) into a second accommodating cavity (20b) of the bending rigidity spring piece (20), and connecting the bending rigidity spring piece (20) with the rudder shaft through a fastening assembly (50);

measuring the friction force of the rotation freedom degree of the rudder shaft;

step six, changing the thickness of the adjusting cushion block (40) and/or the material of the friction adjusting ring (30), repeating the steps one to five, respectively measuring the friction force of the rotation freedom degree of the rudder shaft, and recording and storing the measurement result;

and seventhly, selecting the combination state of the adjusting cushion block (40) and the friction adjusting ring (30) according to the record of the measuring result during the flutter test to carry out the test.

2. The adjustable friction method for flutter testing according to claim 1, the bending stiffness spring piece (20) comprises a bending stiffness connecting section (21), a first arc-shaped clamping section (22), a second arc-shaped clamping section (23), a first clamping section (24) and a second clamping section (25), one end of the first arc-shaped clamping section (22) and one end of the second arc-shaped clamping section (23) are both connected with the bending rigidity connecting section (21), the first arc-shaped clamping section (22) and the second arc-shaped clamping section (23) jointly enclose the first accommodating cavity (20a), the other end of the first arc-shaped clamping section (22) is connected with the first clamping section (24), the other end of the second arc-shaped clamping section (23) is connected with the second clamping section (25), the first clamping section (24) and the second clamping section (25) are arranged in parallel to form the second accommodating cavity (20 b).

3. The adjustable friction method for flutter test according to claim 2, wherein the fastening assembly (50) comprises a screw (51) and a nut (52), the screw (51) respectively passes through the first clamping section (24) and the second clamping section (25) and cooperates with the nut (52) to lock the second accommodating cavity (20b) of the bending stiffness spring piece (20).

4. The adjustable friction method for flutter testing according to claim 3, wherein the material of the friction adjusting ring (30) comprises polytetrafluoroethylene, phenolic plastic or bronze material.

5. The adjustable friction method for flutter test according to claim 3, wherein the structural shape of the adjusting pad block (40) comprises a circular shape or a square shape, the adjusting pad block (40) has a central through hole, the adjusting pad block (40) is arranged between the first clamping section (24) and the second clamping section (25), and the screw (51) sequentially passes through the first clamping section (24), the central through hole of the adjusting pad block (40) and the second clamping section (25) and cooperates with the nut (52) to connect the bending stiffness spring piece (20) with the rudder shaft.

6. The adjustable friction method for flutter test according to claim 5, wherein the height of the adjusting pad block (40) is inversely proportional to the friction of the rudder shaft rotational degree of freedom.

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