Large-diameter flexible pipe dynamic stiffness test bench

Abstract

This application relates to a dynamic stiffness test bench for large-diameter flexible nozzles, belonging to the field of testing and inspection equipment. It includes a direct test bench and an indirect test bench for flexible nozzles. The direct test bench includes a direct test base, a direct force measuring plate mounted on the direct test base, and a direct transition mounting assembly mounted on the direct force measuring plate. The direct mounting assembly mounts the flexible nozzle. The indirect test bench includes an indirect test base, a blocking mass block mounted on the indirect test base, and an indirect transition mounting assembly mounted above the blocking mass block. The indirect transition mounting assembly mounts the flexible nozzle. Vibration testing components are mounted on both the indirect and direct transition mounting assemblies. This application ensures the accuracy of test data while reducing the design cost, manufacturing cost, and testing difficulty of the test bench.

Description

Technical Field

[0001] This application relates to the field of testing and inspection equipment, and in particular to a test bench for the dynamic stiffness of large-diameter flexible nozzles. Background Technology

[0002] Piping systems, often referred to as the "blood vessels" of a ship, are primarily used to transport various media such as oil, water, and steam, playing a crucial role in ensuring the ship's navigation and the operation of its machinery. However, while fulfilling their media transmission function, vibration and noise are also transmitted to the hull structure, becoming significant factors limiting the ship's acoustic stealth performance. Flexible nozzle technology is one of the important methods for effectively suppressing the vibration and noise of piping systems, and it has been widely used in the marine industry, with relatively detailed standards established for its design, inspection, installation, and maintenance. However, due to the diverse structural forms and materials used, its vibration characteristics are particularly complex, and research on the vibration dynamic characteristics of flexible nozzles is still under development.

[0003] To evaluate the vibration reduction performance of flexible nozzles, researchers typically build a platform to simulate the installation environment on a real ship and assess the nozzle's characteristics by measuring insertion loss. However, in actual operation, it has been found that insertion loss is significantly affected by installation conditions, and the consistency of test results under different installation conditions is poor, ultimately leading to inconsistencies between the insertion loss of the simulated ship platform and the actual ship installation. Furthermore, in the analysis phase of flexible nozzle design, transfer matrix analysis or the finite element method are usually employed, and the insertion loss results cannot directly verify or guide the design results.

[0004] Based on this, most domestic research institutions have gradually separated flexible hoses from their application environment and begun to evaluate their dynamic stiffness characteristics. Since flexible hoses and vibration isolators are both vibration damping components, their dynamic stiffness is usually tested and analyzed using direct impedance testing or indirect impedance testing methods.

[0005] Regarding the aforementioned technologies, the inventors believe that the direct impedance testing method requires a sufficiently high impedance of the mounting base at the blocking end. For large-diameter flexible conduits, due to their large installation dimensions, it is difficult to design and manufacture mounting bases with first-order free modes greater than 1000Hz, resulting in a low upper limit frequency for testing. The indirect impedance testing method requires a significant impedance mismatch between the component under test and the blocking mass, and the lower limit frequency for testing is generally about three times the overall system installation frequency. Although increasing the mass of the blocking mass can broaden the lower limit frequency for testing, excessively large blocking masses increase the manufacturing cost of the test bench and the difficulty of testing. Summary of the Invention

[0006] To ensure the accuracy of test data while reducing the design cost, processing cost, and testing difficulty of the test bench, this application provides a dynamic stiffness test bench for large-diameter flexible pipes.

[0007] The large-diameter flexible nozzle dynamic stiffness test bench provided in this application adopts the following technical solution:

[0008] A dynamic stiffness test bench for large-diameter flexible joints includes a direct test bench and an indirect test bench. The direct test bench includes a direct test base, a direct force measuring plate on the direct test base, and a direct transition mounting assembly on the direct force measuring plate, the direct mounting assembly mounting the flexible joint. The indirect test bench includes an indirect test base, a blocking mass on the indirect test base, an indirect transition mounting assembly above the blocking mass, the indirect transition mounting assembly mounting the flexible joint, and vibration testing components on both the indirect and direct transition mounting assemblies.

[0009] Optionally, the testing range of the flexible connector direct test bench is 10Hz-f. L f L The range is 200Hz-300Hz.

[0010] Optionally, the direct transition installation assembly includes a direct upper cover plate, which is fixedly connected to the flexible connector, and a direct lower cover plate is fixedly connected to the bottom end of the flexible connector. The direct upper cover plate and the direct lower cover plate seal the interior of the flexible connector.

[0011] Optionally, a direct adapter plate is provided between the direct lower cover plate and the direct force measuring plate, with the top end of the direct adapter plate fixed to the direct lower cover plate and the bottom end of the direct adapter plate fixed to the direct force measuring plate.

[0012] Optionally, the testing range of the flexible connector indirect test bench is f. H -1000Hz, f H The range is 200Hz-300Hz.

[0013] Optionally, the indirect transition installation assembly includes an indirect top cover plate, which is fixedly connected to the flexible conduit. An indirect adapter plate is fixedly connected to the bottom end of the flexible conduit, and the indirect adapter plate and the top cover plate seal the interior of the flexible conduit.

[0014] Optionally, a support frame is provided at the bottom of the blocking mass block, and an airbag is provided between the bottom of the support frame and the indirect test base, the airbag supporting the support frame.

[0015] Optionally, a first indirect acceleration sensor is fixedly connected to the indirect upper cover plate, and a second indirect acceleration sensor is fixedly connected to the indirect adapter plate.

[0016] Optionally, when the vibration acceleration level at the input end is 20 dB higher than the vibration acceleration at the output end, the dynamic stiffness of the flexible conduit is calculated using the following formula:

[0017]

[0018] Where: m2 is the mass of the blocking mass block; m f a1 is the mass of the transition tool; a2 is the output acceleration; a1 is the input acceleration; Z n For the resistance of the flexible conduit; Z t For airbag impedance; Z m For blocking mass impedance.

[0019] Optionally, the vibration testing assembly includes a gantry frame on which a vibration exciter is suspended. The excitation end of the vibration exciter is connected to the direct transition mounting assembly and the indirect transition mounting assembly, respectively.

[0020] In summary, this application includes at least one of the following beneficial technical effects:

[0021] 1. By reasonably dividing the test frequency bands, and based on the test mechanisms of the direct and indirect methods, test benches are designed in their respective advantageous frequency band ranges to solve the problem that a single test bench cannot meet the needs of wide-band dynamic stiffness testing.

[0022] 2. Since both testing methods avoid their disadvantageous frequency bands, the design difficulty, manufacturing cost, and testing difficulty of the test bench will be greatly reduced. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the flexible nozzle direct test bench in the large-diameter flexible nozzle dynamic stiffness test bench of this application embodiment.

[0024] Figure 2 This is a schematic diagram of the overall structure of the flexible nozzle indirect test bench in the large-diameter flexible nozzle dynamic stiffness test bench of this application embodiment.

[0025] Figure 3 This is a three-dimensional schematic diagram of the direct test bench for flexible nozzles in the large-diameter flexible nozzle dynamic stiffness test bench of this application embodiment.

[0026] Figure 4 This is a side view of the flexible nozzle direct test bench in the large-diameter flexible nozzle dynamic stiffness test bench of this application embodiment.

[0027] Figure 5This is a side view of the indirect test bench for flexible nozzles in the large-diameter flexible nozzle dynamic stiffness test bench of this application embodiment.

[0028] Explanation of reference numerals in the attached drawings: 1. Direct test bench for flexible connectors; 11. Direct test base; 12. Direct force plate; 13. Direct adapter plate; 14. Direct upper cover plate; 15. Direct lower cover plate; 2. Indirect test bench for flexible connectors; 21. Indirect test base; 22. Support frame; 23. Airbag; 24. Blocking mass block; 25. Indirect upper cover plate; 26. Indirect adapter plate; 3. Flexible connector; 4. Gantry frame; 41. Vibration exciter. Detailed Implementation

[0029] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0031] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0032] This application discloses a test bench for the dynamic stiffness of large-diameter flexible nozzles. (Refer to...) Figure 1 , Figure 2 The large-diameter flexible joint dynamic stiffness test bench includes a flexible joint direct test bench 1 and a flexible joint indirect test bench 2. The flexible joint direct test bench 1 is used to test the low-frequency range of the flexible joint 3, with a test range of 10Hz-f. L ,f L The frequency range is approximately 200Hz to 300Hz. The flexible conduit indirect test bench 2 is used to test the flexible conduit 3 in the high-frequency range, with a test range of f... H -1000Hz, f H It is approximately 200Hz-300Hz.

[0033] Reference Figure 3 , Figure 4 The flexible connector direct test bench 1 includes a direct test base 11 located at the bottom. The direct test base 11 is a rigid base, and a direct force measuring plate 12 is provided above the direct test base 11. The direct force measuring plate 12 is rigidly fixed on the low-frequency test base by the pressure plates around it. The direct force measuring plate 12 is used to obtain the blocking force at the output end of the flexible connector 3.

[0034] A direct adapter plate 13 is also provided at the top of the direct force measuring plate 12. The direct adapter plate 13 is set vertically, and multiple direct adapter plates 13 are set along the circumferential direction. One end of each direct adapter plate 13 is located at the center of the flexible pipe 3, and the other end of each direct adapter plate 13 is set outward along its circumferential direction.

[0035] A direct upper cover plate 14 is coaxially disposed at the top end of the flexible conduit 3, and a direct lower cover plate 15 is coaxially disposed at the bottom end of the flexible conduit 3. The direct upper cover plate 14 is fixedly connected to the flexible conduit 3, and the direct lower cover plate 15 is fixedly connected to the flexible conduit 3. The flexible conduit 3 is sealed by the direct upper cover plate 14 and the direct lower cover plate 15, which facilitates the injection and pressure holding of the flexible conduit 3.

[0036] The bottom sidewall of the direct lower cover plate 15 is fixedly connected to the top wall of the direct adapter plate 13, so that the direct adapter plate 13 connects the direct lower cover plate 15 and the direct force measuring plate 12. A first direct acceleration sensor is fixedly connected to the direct upper cover plate 14, and a second direct acceleration sensor is fixedly connected to the direct lower cover plate 15.

[0037] By rationally designing the upper cover plate 14, the lower cover plate 15, the force measuring plate 12, and the test base 11, such as increasing the plate thickness and the number of stiffeners, the first-order free mode frequency of the test fixture is increased, thereby increasing the upper limit frequency of the direct method test.

[0038] Reference Figure 2 , Figure 5 The flexible connector indirect test bench 2 includes an indirect test base 21, which is a rigid base. A support frame 22 is disposed opposite to the indirect test base 21. Multiple airbags 23 are disposed between the support frame 22 and the indirect test base 21, and the airbags 23 are respectively located at the connection positions between the support frame 22 and the indirect test base 21, providing support for the support frame 22.

[0039] A blocking mass block 24 is provided at the top of the support frame 22. The bottom wall of the blocking mass block 24 abuts against the top wall of the support frame 22. The blocking mass block 24 is used to simulate blocking the output end of the flexible pipe 3. The blocking force value is indirectly calculated by the mass of the blocking mass block 24 and the vibration acceleration level.

[0040] An indirect top cover plate 25 is provided at the top of the flexible connector 3. The indirect top cover plate 25 is coaxially arranged with the flexible structure and is fixedly connected to the flexible connector 3. An indirect adapter plate 26 is coaxially arranged at the bottom of the flexible structure and is fixedly connected to the flexible connector 3. The interior of the flexible connector 3 is sealed and fixed by the indirect top cover plate 25 and the indirect adapter plate 26.

[0041] The top end of the indirect adapter plate 26 is connected to the flexible structure, and the bottom end of the indirect adapter plate 26 is connected to the blocking mass block 24. The flexible pipe 3 and the blocking mass block 24 are connected relative to each other through the indirect adapter plate 26.

[0042] A first indirect acceleration sensor is fixedly connected to the indirect upper cover plate 25, and a second indirect acceleration sensor is fixedly connected to the indirect adapter plate 26.

[0043] According to ISO 10846-3, when the vibration acceleration level at the input end is 20 dB higher than that at the output end, the dynamic stiffness of the flexible nozzle 3 can be calculated by the following formula:

[0044]

[0045] Where: m2 is the mass of the blocking mass block, m f The mass of the transition tool is given by a2, the acceleration at the output end is given by a1, and the acceleration at the input end is given by a1.

[0046] In the system consisting of flexible nozzle 3, blocking mass block 24, and airbag 23, the dynamic stiffness of flexible nozzle 3 is rewritten from the above formula as:

[0047]

[0048] Where: m2 is the mass of the blocking mass block, m f For the mass of the transition tool, a2 is the output acceleration, and a1 is the input acceleration; Z n For the resistance of the flexible conduit; Z t For airbag impedance; Z m For blocking mass impedance.

[0049] When Z n -(2πf) 2 (m2+m f )+Z tWhen the dynamic stiffness is 0, a peak value will appear in the measured dynamic stiffness value. This peak value is the anti-resonance point of the system. When the blockage mass increases or the dynamic stiffness of the flexible conduit under test decreases, the anti-resonance point of the system will shift to a lower frequency band. The lower limit frequency of the indirect method test needs to avoid the anti-resonance point of the system, while ensuring that the vibration acceleration level at the input end is 20dB higher than the vibration acceleration at the output end. Increasing the lower limit frequency of the test band of the indirect method is beneficial to reducing the weight of the blockage mass, reducing the cost of bench design and the difficulty of testing.

[0050] By rationally dividing the test frequency bands and designing test benches in their respective advantageous frequency ranges according to the test mechanisms of the direct and indirect methods, the problem that a single test bench cannot meet the needs of wide-band dynamic stiffness testing can be solved.

[0051] Reference Figure 1 , Figure 2 Both the direct test bench 1 and the indirect test bench 2 of the flexible connector are equipped with a gantry 4 located outside the flexible connector 3. The height of the top crossbeam of the gantry 4 is higher than the height of the direct upper cover plate 14 and the indirect upper cover plate 25. A vibrator 41 is suspended on the gantry 4. The excitation end of the vibrator 41 is fixed to the direct upper cover plate 14 or the indirect upper cover plate 25 respectively.

[0052] In this application, the term "multiple" refers to at least two or more, unless otherwise expressly defined. The terms "installed," "connected," "linked," and "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "linked" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A test bench for the dynamic stiffness of large-diameter flexible nozzles, characterized in that: The test bench includes a direct test bench (1) and an indirect test bench (2) for flexible connectors. The direct test bench (1) includes a direct test base (11), on which a direct force measuring plate (12) is mounted. A direct transition mounting assembly is mounted on the direct force measuring plate (12), and the direct mounting assembly mounts the flexible connector (3). The indirect test bench (2) includes an indirect test base (21), on which a blocking mass block (24) is mounted. An indirect transition mounting assembly is mounted above the blocking mass block (24), and the indirect transition mounting assembly mounts the flexible connector (3). A vibration test assembly is mounted on both the indirect transition mounting assembly and the direct transition mounting assembly. The test range of the direct test bench (1) for flexible connectors is 10Hz-f. L f L The range is 200Hz-300Hz; the test range of the flexible connector indirect test bench (2) is f H -1000Hz, f H The range is 200Hz-300Hz; when the vibration acceleration level at the input end is 20dB higher than the vibration acceleration at the output end, the formula for calculating the dynamic stiffness of the flexible conduit is as follows: Where: m2 is the mass of the blocking mass block; m f For the quality of transition tooling; Z n For the resistance of the flexible conduit; Z t f is the airbag impedance; f is the frequency.

2. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 1, characterized in that: The direct transition installation assembly includes a direct upper cover plate (14), which is fixedly connected to the flexible connector (3). A direct lower cover plate (15) is fixedly connected to the bottom end of the flexible connector (3). The direct upper cover plate (14) and the direct lower cover plate (15) seal the interior of the flexible connector (3).

3. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 2, characterized in that: A direct adapter plate (13) is provided between the direct lower cover plate (15) and the direct force measuring plate (12). The top end of the direct adapter plate (13) is fixed to the direct lower cover plate (15), and the bottom end of the direct adapter plate (13) is fixed to the direct force measuring plate (12).

4. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 1, characterized in that: The indirect transition installation assembly includes an indirect top cover plate (25), which is fixedly connected to the flexible pipe (3). An indirect adapter plate (26) is fixedly connected to the bottom end of the flexible pipe (3). The indirect adapter plate (26) and the top cover plate seal the interior of the flexible pipe (3).

5. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 4, characterized in that: The bottom end of the blocking mass block (24) is provided with a support frame (22), and an airbag (23) is provided between the bottom end of the support frame (22) and the indirect test base (21), and the airbag (23) supports the support frame (22).

6. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 4, characterized in that: A first indirect acceleration sensor is fixedly connected to the indirect upper cover plate (25), and a second indirect acceleration sensor is fixedly connected to the indirect adapter plate (26).

7. The dynamic stiffness test bench for large-diameter flexible nozzles according to claim 1, characterized in that: The vibration testing assembly includes a gantry (4), on which a vibration exciter (41) is suspended. The excitation end of the vibration exciter (41) is connected to the direct transition mounting assembly and the indirect transition mounting assembly, respectively.

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