Vibration test load amplifying device for structural member

Abstract

The application discloses a test load amplification device, which realizes prestress (static load) loading by changing the step bending stress of a symmetrical device in the device and realizes the purpose of amplifying different frequency band vibration load of a test piece by adjusting the length of an overhanging beam. The test load amplification device comprises a fixed base (110) located on both sides of a first horizontal direction, which is fixed on a test vibration table; and an overhanging beam (120) fixed on the fixed base (110), and a connecting end (121) at the front end of the overhanging beam (120) changes the overhanging distance in a second horizontal direction perpendicular to the first horizontal direction, both ends of a structural member (200) are respectively connected with the connecting end (121) of the overhanging beam (120), and the test load amplification device (100) is provided with a height adjusting member installed between the test vibration table and the fixed base (110).

Description

Technical Field

[0001] This application relates to the technical field of vibration testing of structural components, and more specifically to a vibration test load amplification device for structural components that can realize prestress (static load) loading and vibration load amplification. Background Technology

[0002] In the past, when conducting vibration tests on various structural components, if the problem of vibration fatigue life under complex mechanical stress environment is involved, such as vibration superposition static fatigue test, and static or fatigue loads need to be applied in the vibration environment, the following are some typical methods.

[0003] (1) Vibration fatigue test is conducted by connecting weights with a rubber rope (elastic rope) to the moving cylinder to change the static force.

[0004] For example, Chinese invention patent CN114705473B discloses an aircraft vibration superposition fatigue strength testing system and its low stiffness load application method. The rubber rope connecting weight method uses the geometric nonlinearity of the elongation of the rubber rope within a specific range to decouple the vibration motion direction from the loading direction, thereby avoiding the influence of the inertial force generated by the movement of the weight. Furthermore, in this patent, the static load can only be changed using weights, limiting its applicability and making it impossible to apply large loads. It can only apply unidirectional force. Additionally, the actuator is directly connected to the test piece via a loading rod. When the test piece reciprocates under vibration load, a separate control algorithm is needed to control the loading rod's movement, thus avoiding the effects of reciprocating motion and achieving static or fatigue loading. Moreover, this requires the separate development of servo control or iterative control algorithms, resulting in a complex and costly technical approach. The final control effectiveness is also constrained by various factors.

[0005] (2) The tension generated by the elastic deformation of the elastic rope is controlled and the static force is adjusted by adjusting the motor, and the test is carried out on the vibration table.

[0006] For example, Chinese invention patent CN114275187B discloses a vibration-static-excitation three-in-one testing device. This device uses a motor to control and adjust the tension generated by the elastic deformation of a tension rope, thereby adjusting the magnitude of the static load. Vibration tests are then conducted on a vibration table. The static load testing system changes the angle of the static load by adjusting the position of the pulleys in the fixed pulley mechanism. Furthermore, the amplitude of the static load is varied during the test by repeatedly starting and stopping a bidirectional rotating motor. However, this patent requires the separate development of a motor control algorithm, making the technical approach complex and costly.

[0007] (3) Vibration fatigue test was conducted by applying a low-stiffness airbag to adjust the static load.

[0008] For example, Chinese invention patent CN114813001B discloses a vibration fatigue testing system and method for aircraft with low added stiffness. It describes a low added stiffness airbag consisting of two airbags respectively positioned on the upper and lower surfaces of the aircraft wing structure. The test object is an airfoil test piece, which is a cantilever beam. Static loading is applied directly externally through the low added stiffness airbags with low stiffness characteristics. However, this patent requires the design of corresponding clamps for fixing the airbags, and the installation is complex and difficult to maintain a stable static load.

[0009] (4) Change the stiffness of the base support rod to amplify the vibration load.

[0010] For example, Chinese invention patent CN112857722B discloses a vibration table test acceleration amplification device with variable stiffness, mass, and damping. It describes how changing the stiffness of the base support rod can amplify the vibration load in different frequency bands. The principle is to change the local stiffness of the structural components to adjust the stiffness of the amplifier, thereby amplifying the load in the resonant frequency range. By adjusting the stiffness, mass, and damping ratio of the amplifier, the upper limit of the peak acceleration output of the vibration table can be broken, and a larger peak acceleration output can be achieved.

[0011] In the aforementioned prior art, vibration amplification devices mainly change the natural frequency of the structural component used as the test specimen by moving the relative position of the base clamp, or by applying a damping rod with variable stiffness to change the local stiffness of the structural component to achieve stiffness adjustment, thereby amplifying the vibration load in the resonant frequency range.

[0012] In addition, the methods for applying prestress (static load) during vibration testing include, for example:

[0013] (i) Static loading is performed by applying soft, low-stiffness devices, such as weights connected by rubber ropes or airbags. However, the disadvantage of this method is that the loading method is complex, requiring the design of relatively complex devices for static loading, and the force provided by the rubber ropes or airbags will change when the vibration displacement changes;

[0014] (ii) Apply a concentrated mass to the end of the structural component serving as the test specimen to achieve prestress loading through gravity. However, this method has obvious drawbacks. When high prestress is required, excessive weight can lead to excessive deflection of the test specimen, which will change the structural shape and dynamic characteristics of the actual test specimen.

[0015] Therefore, there is an urgent need for a vibration test load amplification device for structural components that can simultaneously amplify static and dynamic loads during combined static and dynamic loading. Summary of the Invention

[0016] This application is made to solve the above-mentioned technical problems. Its purpose is to provide a vibration test load amplification device, which realizes prestress (static load) loading by changing the step bending stress of the symmetrical device therein, and realizes the purpose of amplifying the vibration load of the test specimen at different frequency bands by adjusting the length of the extended beam.

[0017] To address the technical problem, this application provides a vibration test load amplification device for structural components, used to perform load tests on structural components used as test specimens, characterized by comprising: Fixed bases located on both sides of a first horizontal direction, the fixed bases being fixed to a test vibration table; and an extension beam fixed to the fixed bases, the extension distance of which is changed in a second horizontal direction perpendicular to the first horizontal direction as the connecting end of the extension beam, the two ends of the structural member being respectively installed and connected to the connecting end of the extension beam, and the test load amplification device having a height adjustment component installed between the test vibration table and the fixed bases.

[0018] Preferably, the height adjustment component adjusts the step difference between the two ends of the structural member in a vertical direction perpendicular to the first horizontal direction and the second horizontal direction, so as to change the magnitude of the bending stress borne by the structural member.

[0019] Alternatively, preferably, the protruding beam is fixed to the fixed base by the protruding beam fastening part.

[0020] Alternatively, preferably, the adapters are installed in the connecting ends of the protruding beams via adapter fasteners.

[0021] More preferably, the inner shape of the adapter is adapted to the outer shape of both ends of the structural member.

[0022] Alternatively, preferably, the height adjustment component is a single component capable of adjusting the height, or multiple components can be stacked to achieve overall height adjustment.

[0023] More preferably, the height adjustment element is a thickened pad with a fixed thickness.

[0024] In addition, the test load amplification device arranges acceleration sensors on both sides of the adapter joint near the structural component.

[0025] Based on the above-described configuration, the test load amplification device of this application is applicable to vibration tests in industries such as aviation, aerospace, and rail transportation, with a wide range of applications. In terms of device principle, the resonant frequency band can be calculated through a rapid natural frequency estimation formula, and the length of the cantilever beam can be adjusted to achieve vibration load amplification in different frequency bands. At the same time, by adjusting the upper and lower steps of the left and right symmetrical structures, different values ​​of prestress (static load) can be applied to the structure. The technical principle is simple, the load can be infinitely adjusted, the loading state is stable, and it is easy to operate.

[0026] In particular, in terms of specific form, this application adopts a combined design of thickened pads and extended beams for adjustment, which is easy to install and highly adaptable. It can also avoid the disadvantage of the additional mass caused by other methods, which leads to changes in dynamic characteristics. It is more applicable in vibration fatigue tests involving complex mechanical stress environments.

[0027] In particular, the prestress (static load) can be adjusted before the test by adjusting the number (or thickness) of the thickened shims according to the requirements of the test matrix. Thus, prestress (static load) loading can be achieved simply by changing the step bending stress of the symmetrical device. Furthermore, by adjusting the extension length of the extension beam and securing it firmly with fasteners, the natural frequency of the extension beam can be steplessly adjusted, thereby amplifying the vibration load of the structural components at different frequency bands.

[0028] In addition, acceleration sensors placed near the structural components at the adapter joints on both sides can be used as monitoring points for vibration load amplification, thereby allowing for a more intuitive confirmation of the vibration load amplification effect. Attached Figure Description

[0029] Figure 1 This is a schematic structural diagram illustrating the structure of the test load amplification device according to an embodiment of this application.

[0030] Figure 2 Viewed from the side Figure 1 The side view of the test load magnification device shown. (Symbol Explanation)

[0031] 100 Test Load Amplification Device; 110 fixed base; 111 mounting holes; 120mm extended beam; 121 connector; 130 Extending beam fixing part; 140 adapter connector; 150 adapter fastener; 160 thickened pad; 200 structural components. Detailed Implementation

[0032] The following is for reference Figure 1 and Figure 2 The structure and principle of the test load amplification device 100, which is an embodiment of this application, will be described, wherein... Figure 1 This is a schematic structural diagram illustrating the structure of the test load amplification device 100 according to an embodiment of this application. Figure 2 Viewed from the side Figure 1 The side view of the test load amplification device 100 shown.

[0033] like Figure 1 As shown, the test load amplification device 100 of this application includes: fixed bases 110 located on both sides of a first horizontal direction (e.g., left-right direction), the fixed bases 110 being fixed to a test vibration table (not shown) through mounting holes 111; and an extension beam 120 being fixed to the fixed bases 110 through an extension beam fastening part 130, and the connecting end 121 at its front end being able to change the extension distance relative to the extension beam fixing part 130 in a second horizontal direction (e.g., front-back direction) perpendicular to the first horizontal direction (e.g., left-right direction), and the two ends of the structural member 200 serving as the test piece being respectively connected to the connecting end 121 of the extension beam 120 through adapter joints 140.

[0034] like Figure 2 As shown, the adapter joints 140 (at both ends of the structural member 200) are respectively installed in the connecting end 121 of the protruding beam 120 via adapter joint fasteners 150, and their internal shape is adapted to the external shape of the two ends of the structural member 200. By selecting adapter joints 140 with different internal shapes, the test load amplification device 100 of this application can be adapted to load tests of various structural members.

[0035] The test load amplification device 100 of this application can further be equipped with a height adjustment component. The height adjustment component can be a single height-adjustable part or a part in which multiple components are stacked to achieve overall height adjustment. In this application, the height adjustment component is, for example, a thickened pad 160 with a fixed thickness, and the number of stacked blocks can be reasonably selected according to the actual test matrix. Specifically, the thickened pad 160 is installed between the vibration table and the fixed base 1. By increasing or decreasing the number of thickened pads 160, the different step differences between the two ends of the structural member 200 serving as the test specimen in the vertical direction perpendicular to the first and second horizontal directions can be adjusted, thereby changing the magnitude of the bending stress to achieve different prestress (static load) loading.

[0036] The following describes the test process of using the test load amplification device 100 of this application to perform load tests on the structural component 200.

[0037] First, based on the test objective of conducting load tests on structural component 200, a test load amplification device 100 of appropriate size is selected.

[0038] For example, for structural component 200, its natural frequency information ω can be obtained through modal analysis or experimentation. n Then, based on the inherent frequency information ω of structural component 200... n and the section properties of the selected protruding beam 120. The length calculation results of the corresponding protruding beam 120 are obtained by using the following equations (1) and (2).

[0039] The formulas for calculating the natural frequency of an extended beam (where n is the natural frequency order) are as follows: (1) (2):

[0040]

[0041] s n l=1.8751, 4.6941, 7.8548, 10.9955, 14.1372 (2)

[0042] in:

[0043] ω n It is the inherent frequency information of structural component 200;

[0044] s n These are intermediate variables defined in the process of solving the differential equation for the transverse vibration of the beam. l is the designed extension length of the beam (120 mm), while s... n l is determined by the natural frequency equation of the cantilever beam, cosslcoshsl=-1, which is a fixed value. When n=1, s n When l = 1.8751 and n = 2, s n l = 4.6941, and so on;

[0045] This is the cross-sectional property information of the extended beam 120.

[0046] In addition, for the load test of structural component 200, the complex mechanical stress environment needs to be considered to obtain the required static load test conditions, thereby carrying out the thickness dimension design of the thickened gasket 160.

[0047] Taking structural component 200 as an example Figure 1 Taking the solid beam structure or pipeline structure shown as an example, based on the complex mechanical stress environment to be considered, the maximum bending stress S at the end to be set in the load test is obtained, and the maximum thickness D of the thickened gasket 160 is calculated by the following formula (3).

[0048] The formula for quickly estimating the maximum bending stress at the end 121 of a solid beam structure or pipe structure is as follows (3):

[0049]

[0050] in,

[0051] E is the elastic modulus;

[0052] I is the moment of inertia;

[0053] D is the step difference value, which is also the maximum thickness dimension of the 160 thickened gasket to be determined;

[0054] P is the load perpendicular to the surface at the end of a solid beam or pipe structure;

[0055] L is the length of structural component 200;

[0056] C represents the pipe radius or half the thickness.

[0057] Therefore, the maximum thickness dimension D of the thickened gasket 160 can be calculated.

[0058] In summary, based on the dynamic characteristics of structural component 200 and the complex mechanical stress environment to be considered in the test, the design length l of the extended beam 120 and the maximum thickness D of the thickened shim 160 can be calculated using the above method, thereby completing the key dimension design of the test load amplification device 100.

[0059] Next, based on the structural shape of structural component 200, the inner shape of adapter 140 is designed.

[0060] Subsequently, the designed and manufactured test load amplification device 100 is assembled and installed with the structural component 200, which serves as the test specimen, and fixed to a vibration table (not shown).

[0061] According to the test load amplification device 100 of this application and the aforementioned test method, the prestress (static load) can be adjusted before the test by adjusting the number (or thickness) of the thickened shims 160 according to the test matrix requirements and according to formula (3). Thus, prestress (static load) loading can be achieved simply by changing the step bending stress of the symmetrical device.

[0062] Furthermore, according to the test load amplification device 100 of this application and the aforementioned test method, By adjusting the extension length of the extension beam 120 and fixing it firmly with the extension beam fastener 130, and by steplessly adjusting the natural frequency of the extension beam 120 according to formulas (1) and (2), the purpose of amplifying the vibration load of the structural component 200 at different frequency bands can be achieved.

[0063] In addition, during the test using the test load amplification device 100 of this application, acceleration sensors can be arranged near the structural member 120 on both sides of the adapter 140 as vibration load amplification monitoring points to confirm the amplification effect of the vibration load.

[0064] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vibration test load amplification device for structural components, used to perform load tests on structural components (200) used as test specimens, characterized in that, include: Fixed bases (110) located on both sides in the first horizontal direction are fixed to the test vibration table; and The extension beam (120) is fixed to the fixed base (110), and the connecting end (121) at its front end changes its extension distance in a second horizontal direction perpendicular to the first horizontal direction. Both ends of the structural member (200) are respectively installed and connected to the connecting end (121) of the protruding beam (120). The test load amplification device (100) has a height adjustment component installed between the test vibration table and the fixed base (110). The extension beam (120) is fixed to the fixed base (110) by the extension beam fastening part (130). The connecting end (121) at the front end of the extension beam (120) can change the extension distance in the second horizontal direction relative to the extension beam fastening part (130), and is fixed at the adjusted extension distance position by the extension beam fastening part (130). The height adjustment component adjusts the step difference between the two ends of the structural member (200) in a vertical direction perpendicular to the first horizontal direction and the second horizontal direction, so as to change the magnitude of the bending stress borne by the structural member (200).

2. The vibration test load amplification device for structural components as described in claim 1, characterized in that, The test load amplification device also includes an adapter. The adapter (140) is installed in the connecting end (121) of the protruding beam (120) by adapter fastener (150).

3. The vibration test load amplification device for structural components as described in claim 2, characterized in that, The inner shape of the adapter (140) is adapted to the outer shape of both ends of the structural member (200).

4. The vibration test load amplification device for structural components as described in claim 2, characterized in that, The height adjustment component is either a single component capable of adjusting the height, or multiple components stacked together to achieve overall height adjustment.

5. The vibration test load amplification device for structural components as described in claim 4, characterized in that, The height adjustment component is a thickened pad (160) with a fixed thickness.

6. The vibration test load amplification device for a structural member as described in any one of claims 2 to 5, characterized in that, The test load amplification device (100) has acceleration sensors arranged on both sides of the adapter (140) near the structural member (120).

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