Three-dimensional acoustic-elastic model testing method and apparatus with mechanical isolation system

Abstract

The present application relates to a kind of three-dimensional acoustic elastic model test method and device with mechanical vibration isolation system, it is related to ship vibration isolation system vibration and underwater three-dimensional acoustic elastic calculation and testing field, by considering the excitation of simulating different equipment, the replacement and test of different types of isolators are realized, the vibration transmission path from equipment excitation to acoustic radiation is completely obtained by arranging measuring point, the scientific test of the test of model in air and underwater, the three-dimensional acoustic elastic model test device with mechanical vibration isolation system designed in the present application constructs corresponding air and open water test technology, and effectively supports the development and popularization and application of calculation method.

Description

Technical Field

[0001] This invention relates to the field of vibration calculation and testing technology for ship vibration isolation systems and underwater three-dimensional acoustoelasticity, and in particular to a three-dimensional acoustoelastic model test method and apparatus with a mechanical vibration isolation system. Background Technology

[0002] Mechanical noise is the primary source of noise for ships when stationary or cruising at low speeds. Effectively reducing the vibration and sound radiation of mechanical systems is crucial for ship noise reduction. Currently, among mechanical noise reduction methods, using floating raft isolation systems is the most suitable and effective method for large ship machinery, primarily consisting of a base, isolators, and floating rafts. In floating raft isolation systems, the vibration transmission path involves multiple structural levels, making the calculation of radiated noise extremely complex. Extensive research has been conducted both domestically and internationally on the calculation and testing of ship acoustic vibration with floating raft isolation systems. Recently, the academic community has developed linear and nonlinear three-dimensional acoustic elasticity theories and calculation methods for ships with mechanical isolation systems, enabling complete calculations of the entire process from equipment excitation to floating raft vibration, isolator transmission, base vibration, and hull vibration and sound radiation. The calculation method has been established, and corresponding calculation software modules have been developed and implemented in engineering trials.

[0003] Model testing with a complete vibration isolation system is a crucial means of verifying the correctness of computational methods and software. For mechanical vibration isolation systems on ship hulls, the test model needs to specifically consider how to simulate the excitation of different equipment, how to implement the replacement and testing of different types of vibration isolators, how to arrange measuring points to completely capture the vibration transmission path from equipment excitation to sound radiation, and how to conduct scientific tests on the model in air and underwater. Designing a three-dimensional acoustoelastic model test device with a mechanical vibration isolation system and constructing corresponding air and open water testing techniques can strongly support the development and widespread application of computational methods. Summary of the Invention

[0004] To address the aforementioned issues, the applicant provides a three-dimensional acoustoelastic model testing method and apparatus with a reasonably structured mechanical vibration isolation system.

[0005] The technical solution adopted in this invention is as follows: A three-dimensional acoustoelastic model with a mechanical vibration isolation system includes a shell, end plates at both ends of the shell, and a vibration isolation system inside the shell. The vibration isolation system includes: The base is connected to the inner curved wall of the shell. Vibration isolators are installed on the mounting surface formed at the top of the base. A floating raft is mounted on a vibration isolator; the raft is equipped with an excitation signal output device, which includes an excitation rod. The location of the concentrated excitation point of the vibration isolation system is adjustable.

[0006] As a further improvement to the above technical solution: It is suitable for vibration isolation testing in air and water environments. When testing in a water environment, the end plate and the shell form a closed test space.

[0007] A testing method for a three-dimensional acoustoelastic model using a mechanical vibration isolation system employs an exciter and a vibration motor to provide excitation signals. The excitation methods for the model include: Method 1: The vibrator is turned on, the excitation rod is connected to the boss of the floating raft, and the concentrated excitation point acts on the middle of the boss. At the same time, the vibration motor on the floating raft is turned on. The second method involves turning on the vibrator, connecting the excitation rod to the boss on the floating raft, concentrating the excitation point on the center of the boss, and turning off the vibration motor on the floating raft. The third method: The vibrator is turned on, the vibrator rod is connected to the bottom shell of the column shell, and the concentrated excitation point acts on the shell, while the vibration motor on the floating raft is turned off.

[0008] As a further improvement to the above technical solution: When the model is tested in an air environment, the process is divided into two stages: testing the model's natural frequencies and mode shapes, and testing the vibration isolation transfer. The excitation method for the natural frequency and mode shape stages of the test model is as follows: the vibrator is turned on, the excitation rod is connected to the bottom shell of the column shell, the concentrated excitation point acts on the bottom shell of the column shell, and the vibration motor on the floating raft is turned off. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing. The excitation method for the vibration isolation transmission stage of the test is as follows: the vibrator is turned on, the excitation rod is connected to the boss of the floating raft, the concentrated excitation point acts on the middle of the boss, and at the same time the vibration motor on the floating raft is turned on. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing.

[0009] The arrangement of measuring points used in the air environment test is as follows: Accelerometers are uniformly distributed along the circumferential cross-section inside the housing. An acceleration sensor is placed on the panel of the base corresponding to the vibration isolator. The vibrator and vibration motor of the floating raft are respectively arranged with acceleration sensors at diagonal positions. A force sensor is placed at the end of the excitation rod.

[0010] When the model is used for underwater environment testing, the following tests are conducted: wet model natural frequencies and mode shapes, vibration transmission of the underwater mechanical vibration isolation system, and acoustic radiation of the model. The testing steps are as follows: The excitation method is as follows: the vibrator is turned on, the excitation rod is connected to the boss of the floating raft, the concentrated excitation point is applied to the middle of the boss, the vibration motor on the floating raft is turned off, after the acceleration sensor and force sensor are arranged, the two ends of the shell are sealed. The model device is equipped with real-time monitoring equipment and is watertight. The model is lowered into the water to the desired depth; hydrophones are placed in the water to detect background noise. Before the formal test, the hydrophone was removed, and the vibration acceleration and underwater acoustic data at each measuring point were recorded. After one test, the model was lifted and the excitation method was changed to: the vibrator was turned on, the vibrator rod was connected to the floating raft boss, the concentrated excitation point was applied to the middle of the boss, and the vibration motor on the floating raft was turned on at the same time. Adjust the installation position of the vibrator, fix the vibrator rod and force sensor to ensure that both devices excite the raft simultaneously, and test again.

[0011] The underwater testing measurement point layout is as follows: Accelerometers are uniformly distributed along the circumferential cross-section inside the housing. An acceleration sensor is placed at the vibration isolator mounting location on the base panel. An acceleration sensor is installed at the connection point of the vibration isolator to the floating raft. Accelerometers are placed diagonally on the excitation signal output device of the floating raft. An acceleration sensor is placed at the protrusion of the floating raft. A force sensor is placed at the end of the excitation rod.

[0012] The verification process is as follows: First, vibration tests are conducted on linear isolators, then nonlinear isolators are installed and tested again. The vibration transmission characteristics of the mechanical vibration isolation system under different isolators are obtained, and the comparison and verification guide the design of nonlinear isolators. In the time-domain and frequency-domain acoustic vibration verification methods, different signals are used for excitation. In the time-domain acoustic vibration test, under the second excitation method, the exciter emits a 1-second short transient excitation signal; in the frequency-domain acoustic vibration test, under the second excitation method, the exciter emits a wide-frequency steady-state excitation, and the excitation signal is adjusted in real time according to the test purpose.

[0013] The beneficial effects of this invention are as follows: This invention provides a low-cost and highly operable model test scheme for verifying the three-dimensional acoustoelastic calculation methods of linear and nonlinear ships with mechanical vibration isolation systems.

[0014] According to the method provided by this invention, it is convenient to carry out the design of a ring-ribbed cylindrical shell test model with a mechanical vibration isolation system, the selection of excitation equipment, the vibration test of the dry model in air and the arrangement of measuring points, the acoustic vibration test of the underwater model and the arrangement of internal and external measuring points, etc., forming a systematic and directly instructive test method and device for three-dimensional acoustic elastic model of ships with a mechanical vibration isolation system.

[0015] This invention serves the development of three-dimensional acoustic elasticity theory and application technology for ships, providing model test schemes and professional test devices for the evaluation and verification of corresponding calculation methods and software, and playing a good supporting role in their further development and promotion. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the housing in its closed state according to the present invention.

[0017] Figure 2 This is a perspective view of the housing structure of the present invention.

[0018] Figure 3 Built into Figure 2 A schematic diagram of the floating raft structure within the hull.

[0019] Figure 4 This is a front view of the shell and raft assembly of the present invention. The red dots in the figure indicate the positions of different excitation points.

[0020] Figure 5 This is a radial sectional view of the shell and raft assembly of the present invention.

[0021] Figure 6 This is a schematic diagram showing the arrangement of the acceleration sensor measuring points for a model device in air.

[0022] Figure 7 This is a schematic diagram of the vibration test state of the model device in air.

[0023] Figure 8 This is a schematic diagram showing the cables leading out in the model; the red lines represent the cables.

[0024] Figure 9 This is a schematic diagram of the accelerometer measurement points on the shell when the model is underwater.

[0025] Figure 10 This is a schematic diagram showing the accelerometer measurement points on the base and raft when the model is underwater.

[0026] Figure 11 A schematic diagram showing the arrangement of measuring points and test conditions for underwater hydrophones when conducting acoustic and vibration tests on a model underwater.

[0027] Figure 12This is a schematic diagram of the circumferential measurement point arrangement on the floating platform when the model is subjected to acoustic and vibration tests underwater.

[0028] Figure 13 This is a flowchart of the present invention.

[0029] The components are: 1. Shell; 2. End plate; 3. Base; 4. Vibration isolator; 5. Floating raft; 6. Vibration exciter; 7. Vibration motor; 8. Excitation rod; 9. Boss; 10. Groove; 11. Pagoda head; 12. Cable; 13. Flexible hose; 14. Gantry frame; 15. Floating platform. Detailed Implementation

[0030] The following is in conjunction with the appendix Figures 1-13 The following describes specific embodiments of the present invention.

[0031] A three-dimensional acoustoelastic model with a mechanical vibration isolation system includes a shell, end plates at both ends of the shell, and a vibration isolation system inside the shell. The vibration isolation system includes: The base is connected to the inner curved wall of the shell. Vibration isolators are installed on the mounting surface formed at the top of the base. A floating raft is mounted on a vibration isolator; the raft is equipped with an excitation signal output device, which includes an excitation rod. The location of the concentrated excitation point of the vibration isolation system is adjustable.

[0032] As a further improvement to the above technical solution: It is suitable for vibration isolation testing in air and water environments. When testing in a water environment, the end plate and the shell form a closed test space.

[0033] A testing method for a three-dimensional acoustoelastic model using a mechanical vibration isolation system employs an exciter and a vibration motor to provide excitation signals. The excitation methods for the model include: Method 1: The vibrator is turned on, the excitation rod is connected to the boss of the floating raft, and the concentrated excitation point acts on the middle of the boss. At the same time, the vibration motor on the floating raft is turned on. The second method involves turning on the vibrator, connecting the excitation rod to the boss on the floating raft, concentrating the excitation point on the center of the boss, and turning off the vibration motor on the floating raft. The third method: The vibrator is turned on, the vibrator rod is connected to the bottom shell of the column shell, and the concentrated excitation point acts on the shell, while the vibration motor on the floating raft is turned off.

[0034] As a further improvement to the above technical solution: When the model is tested in an air environment, the process is divided into two stages: testing the model's natural frequencies and mode shapes, and testing the vibration isolation transfer. The excitation method for the natural frequency and mode shape stages of the test model is as follows: the exciter is turned on, the excitation rod is connected to the bottom shell 1 of the column shell, the concentrated excitation point acts on the bottom shell 1 of the column shell, and the vibration motor on the floating raft is turned off. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing. The excitation method for the vibration isolation transmission stage of the test is as follows: the vibrator is turned on, the excitation rod is connected to the boss of the floating raft, the concentrated excitation point acts on the middle of the boss, and at the same time the vibration motor on the floating raft is turned on. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing.

[0035] The arrangement of measuring points used in the air environment test is as follows: Accelerometers are uniformly distributed along the circumferential cross-section inside the housing. An acceleration sensor is placed on the panel of the base corresponding to the vibration isolator. The vibrator and vibration motor of the floating raft are respectively arranged with acceleration sensors at diagonal positions. A force sensor is placed at the end of the excitation rod.

[0036] When the model is used for underwater environment testing, the following tests are conducted: wet model natural frequencies and mode shapes, vibration transmission of the underwater mechanical vibration isolation system, and acoustic radiation of the model. The testing steps are as follows: The excitation method is as follows: the vibrator is turned on, the excitation rod is connected to the boss of the floating raft, the concentrated excitation point is applied to the middle of the boss, the vibration motor on the floating raft is turned off, after the acceleration sensor and force sensor are arranged, the two ends of the shell are sealed. The model device is equipped with real-time monitoring equipment and is watertight. The model is lowered into the water to the desired depth; hydrophones are placed in the water to detect background noise. Before the formal test, the hydrophone was removed, and the vibration acceleration and underwater acoustic data at each measuring point were recorded. After one test, the model was lifted and the excitation method was changed to: the vibrator was turned on, the vibrator rod was connected to the floating raft boss, the concentrated excitation point was applied to the middle of the boss, and the vibration motor on the floating raft was turned on at the same time. Adjust the installation position of the vibrator, fix the vibrator rod and force sensor to ensure that both devices excite the raft simultaneously, and test again.

[0037] The underwater testing measurement point layout is as follows: Accelerometers are uniformly distributed along the circumferential cross-section inside the housing. An acceleration sensor is placed at the vibration isolator mounting location on the base panel. An acceleration sensor is installed at the connection point of the vibration isolator to the floating raft. Accelerometers are placed diagonally on the excitation signal output device of the floating raft. An acceleration sensor is placed at the protrusion of the floating raft. A force sensor is placed at the end of the excitation rod.

[0038] The verification process is as follows: First, vibration tests are conducted on linear isolators, then nonlinear isolators are installed and tested again. The vibration transmission characteristics of the mechanical vibration isolation system under different isolators are obtained, and the comparison and verification guide the design of nonlinear isolators. In the time-domain and frequency-domain acoustic vibration verification methods, different signals are used for excitation. In the time-domain acoustic vibration test, under the second excitation method, the exciter emits a 1-second short transient excitation signal; in the frequency-domain acoustic vibration test, under the second excitation method, the exciter emits a wide-frequency steady-state excitation, and the excitation signal is adjusted in real time according to the test purpose.

[0039] The specific structure and working principle of this invention are as follows: like Figure 1 , Figure 2 As shown, this invention provides a ring-ribbed cylindrical shell model with a built-in mechanical vibration isolation system as an experimental device. Figure 4 and Figure 5 As shown, the axis of the ring-ribbed cylindrical shell model is placed horizontally, and the inner wall of the shell 1 has a ring array of T-shaped ribs. End plates 2 are sealed and installed at both ends of the shell 1. A base 3 is installed inside the shell 1. The base 3 consists of two coplanar platforms parallel to the axis of the shell 1. A floating raft 5 is connected to the base 3 via vibration isolators 4. Excitation equipment is installed on the panel of the floating raft 5. The excitation equipment includes a vibrator 6 and a vibration motor 7. The vibrator 6 provides a wide-band excitation signal, and the vibration motor 7 emits a low-frequency typical line spectrum, ensuring a high signal-to-noise ratio for the model and enabling the simulation of various vibration excitations of real ship equipment.

[0040] The vibrator 6 is flexibly mounted, for example, on a spring or buffer layer. This provides an ideal high-frequency filtering effect at the mounting location, effectively isolating the dynamic forces transmitted from the vibrator 6 to the structure through the mounting location. This ensures that the excitation force is transmitted to the structure only through the vibrating rod 8. The vibration motor 7 is rigidly connected with bolts, allowing the vibration to be directly transmitted to the floating raft 5.

[0041] The device of this invention can be used for both air and underwater testing. When performing dry model vibration tests in air, end plates 2 do not need to be installed. When performing underwater acoustic and vibration tests on the model device, end plates 2 are installed on the model for sealing and counterweighting. The end plates 2 on both sides are bolted to the cylindrical shell flanges. Sealing grooves are provided on the cylindrical shell flanges to accommodate rubber sealing rings and ensure watertightness.

[0042] When conducting model tests in air and underwater, the excitation methods can be summarized into the following three types: Method 1: The vibrator 6 is turned on, the vibrating rod 8 is connected to the boss 9 of the floating raft 5, and the concentrated excitation point acts on the middle of the boss 9. At the same time, the vibration motor 7 on the floating raft 5 is turned on. The second method: The vibrator 6 is turned on, the vibrating rod 8 is connected to the boss 9 of the floating raft 5, and the concentrated excitation point acts on the middle of the boss 9. The vibration motor 7 on the floating raft 5 is turned off. The third method: the vibrator 6 is turned on, the vibrator rod 8 is connected to the bottom of the cylindrical shell 1, the concentrated excitation point acts on the shell 1, and the vibration motor 7 on the floating raft 5 is turned off.

[0043] The following provides a verification method for using the above structure in experiments for linear and nonlinear three-dimensional acoustoelastic calculations of ships.

[0044] In order to realize the time-domain and frequency-domain verification method of linear and nonlinear vibration isolation system, the vibration isolator 4 on the base 3 is first selected as a linear BE rubber vibration isolator 4. Based on the installation height, load, dynamic and static stiffness of the rubber vibration isolator 4, a high static and low dynamic quasi-zero stiffness vibration isolator 4 with strong nonlinearity is designed.

[0045] The bottom of the raft 5 and the panel of the base 3 have round holes for matching BE rubber vibration isolators 4 and nonlinear vibration isolators 4, which serve as bolt interfaces to connect the two types of vibration isolators 4.

[0046] During the experiment, a vibration test was first conducted on the BE rubber vibration isolator 4. Then, the bolts were removed, and the nonlinear vibration isolator 4 was installed before testing. This not only provides a test installation platform for different vibration isolators 4, allowing the vibration transmission characteristics of the mechanical vibration isolation system under different vibration isolators 4 to be obtained, but also allows for comparison and verification between the vibration isolators 4 to guide the design of the nonlinear vibration isolator 4.

[0047] In the time-domain and frequency-domain acoustic vibration verification methods, different excitation signals are required. The time-domain acoustic vibration test needs to be carried out in the second excitation mode, that is, with the exciter 6 turned on, the concentrated excitation point acting on the middle of the boss 9, and the vibration motor 7 on the floating raft 5 turned off. The exciter 6 emits a short transient excitation signal of 1 second. Frequency domain acoustic vibration testing requires the exciter 6 to emit a wideband steady-state excitation under the second excitation method, and the excitation signal should be adjusted in real time according to the test objective.

[0048] The following are some specific experimental schemes for explanation.

[0049] Experiment 1: Test Procedure for Vibration Testing of a Dry Model in Air. (Reference) Figure 6 , Figure 7 The arrangement of measuring points.

[0050] The steps for vibration testing of a dry model in air are as follows: 1. The natural frequency and mode shape of the test model are tested using the third excitation method, namely, the vibration motor 6 is turned on and the vibration motor 7, which is applied to the bottom shell 1 and the floating raft 5, is turned off, to ensure that only one excitation force excites the bottom shell 1. Then, according to the expected measurement point requirements, acceleration sensors and force sensors are arranged.

[0051] A hook is welded to the top of the model device, and a crane is used to slowly lift the model and suspend it in the air for testing.

[0052] 2. When testing the vibration transmission of the vibration isolation system of the model, the first excitation method is adopted, that is, with the exciter 6 turned on, the concentrated excitation point acting on the middle of the boss 9, and the vibration motor 7 turned on, both excitation devices are turned on simultaneously to excite the floating raft 5. Then, acceleration sensors and force sensors are arranged according to the expected measurement point requirements. The model is slowly lifted by a crane and suspended in the air for testing.

[0053] The arrangement of measuring points for the dry model vibration test in air is as follows: Figure 5 As shown, 12 accelerometers are evenly arranged in the central circumferential section of the model device and numbered sequentially from #1 to #12. These accelerometers are used to test the natural frequencies and typical mode shapes, as well as the vibration response on the housing 1.

[0054] Near the installation positions of the four vibration isolators 4 on the base 3 panel, four acceleration sensors, numbered #13 to #16, are arranged. These four acceleration sensors are used to obtain the vibration response transmitted from the vibration isolators 4 to the base 3. The installation position of the vibration motor 7 on the floating raft 5, that is, the location of the floating raft 5 at... Figure 5 Two acceleration sensors, numbered #17 and #18, are arranged diagonally opposite to the vibration motor 7, for example, at the left front and right rear of the vibration motor 7, respectively, to obtain the vibration response at the foot of the vibration motor 7, which is regarded as the vibration input of the vibration motor 7. Two accelerometers, numbered #19 and #20, are also arranged diagonally at the installation location of the vibrator 6 on the floating raft 5 to obtain the vibration response at the installation location of the vibrator 6 and to detect the effectiveness of the vibration isolation of the flexible installation. A force sensor, numbered #21, is placed at the connection point of the end of the excitation rod 8 to obtain the excitation force provided by the exciter 6. The force sensor is determined according to the excitation position. For example, if the excitation rod 8 excites the boss 9 of the floating raft 5, the force sensor is connected to the excitation rod 8 and fixed to the boss 9; if the excitation rod 8 excites the shell 1, the force sensor is connected to the excitation rod 8 and fixed to the shell 1.

[0055] If the test is to be conducted in open water, the end plates 2 at both ends of the shell 1 need to be sealed. In this case, it is necessary to design how to lead out the cables 12 of the equipment inside the model device.

[0056] When testing in open water, the interior of the housing 1 forms a closed structure. Considering the opening control of the excitation equipment and the data transmission of the acceleration sensor, it is necessary to design the lead-out of the equipment cable 12.

[0057] like Figure 8 As shown, to ensure the model has an outlet, a groove 10 is specially made on one end plate 2 for all cables 12 to be knotted and passed through. A round hole is made at the top of the groove 10 to weld a pagoda head 11, which avoids large-angle bending of the connecting hose 13 and allows it to be connected to the water surface more smoothly. The length of the hose 13 must exceed the diving depth of the model by at least 5m. The vertical upward tension on the model when it is suspended underwater is provided only by the traction rope on the lifting lug, ensuring that the hose 13 and the connection point do not bear tension.

[0058] The height of the pagoda head 11 should be no less than 10cm to increase the length of the hose 13 connection and ensure the connection is secure. After the hose 13 is connected, use clamps and waterproof tape to double-fix the connection point to ensure reliable water tightness of the pagoda head 11 and hose 13 connection. In this way, the cable 12 can be smoothly connected to the water surface by passing through the end cap protrusion 10, exiting the pagoda head 11, and then through the hose 13.

[0059] Experiment 2: When conducting vibration and acoustic radiation tests on the model underwater, the main tasks include testing the natural frequencies and mode shapes of the wet model, testing the vibration transmission of the underwater mechanical vibration isolation system, and testing the model's acoustic radiation. The underwater vibration measurement point layout is as follows: Figure 9 and Figure 10 .

[0060] Specifically, the second excitation method is adopted: the vibrator 6 is turned on, the excitation rod 8 is connected to the boss 9 of the floating raft 5, and the concentrated excitation point acts on the middle of the boss 9. The vibration motor 7 on the floating raft 5 is turned off, ensuring that only one excitation force excites the bottom shell 1 of the column shell. Then, the acceleration sensor and force sensor are arranged according to the measurement point requirements. After the vibrator 6 and acceleration sensor are installed and checked to be normal, the end caps of the fixed model are installed.

[0061] Cameras are installed inside the model for real-time monitoring, allowing for real-time monitoring of the interior from the ship to check for leaks.

[0062] After tidying up and bundling the cables 12 of the equipment inside the model, pass them through the pagoda head 11 on the end cap. Use clamps and waterproof tape to ensure the model is watertight. After the water has completely solidified, check the watertightness.

[0063] Thread a rope through the model's lifting lugs and connect it to the lifting ring. Mark the appropriate position on the rope according to the water depth. Use lifting equipment to lift the lifting ring and slowly lower the model into the water. Stop lowering when the mark is close to the water surface.

[0064] Hydrophones were placed in the water area to test the background noise.

[0065] The equipment is turned on for testing, and the hydrophone array is moved. Vibration acceleration and underwater acoustic data are recorded at each measuring point.

[0066] After the first working condition test is completed, the model is slowly lifted from the water and placed on the support frame. The end cap on the side without the pagoda head 11 is opened, and the first excitation method is adopted: the vibrator 6 is turned on, the excitation rod 8 is connected to the boss 9 of the floating raft 5, and the excitation point is concentrated on the middle of the boss 9. At the same time, the vibration motor 7 on the floating raft 5 is turned on. The installation position of the vibrator 6 is adjusted, and the excitation rod 8 and force sensor are fixed to ensure that the two devices excite the floating raft 5 at the same time. After the installation is completed and checked to be normal, the end caps of the model are installed and fixed.

[0067] Repeat the steps described above: immerse the model in water, test the background noise, and obtain point vibration acceleration and underwater acoustic data, until all tests are completed.

[0068] During testing, the selection of the test water area, environment, and feasibility must be considered. The test water area should be at least 30 meters deep, preferably not close to the shore, open, with a relatively flat bottom, and in a quiet environment. The test should ideally be conducted at night to avoid conflict with the working hours of surrounding facilities such as dams, power plants, shipyards, and docks. Furthermore, it should be avoided during summer and winter to prevent underwater currents caused by strong winds and heavy rain, and to prevent equipment malfunctions, hose cracking, and surface freezing due to low temperatures. During testing, vessel traffic in the test water area should be avoided, and background noise levels must meet testing requirements. Once the equipment is turned on, the signal-to-noise ratio should be greater than 6 dB to ensure reliable and uninterrupted test data.

[0069] The internal vibration measurement point arrangement for the underwater acoustic and vibration test of the model is as follows, in conjunction with reference. Figure 11 The arrangement of measuring points.

[0070] When conducting underwater acoustic and vibration tests on the model device, due to the large number of measurement points, they are divided into measurement points on the shell 1 and measurement points on the base 3 and the floating raft 5.

[0071] like Figure 7 As shown, 12 accelerometers, numbered #1 to #12, are evenly arranged in the circumferential section in the middle of the model to test the natural frequencies and mode shapes of the wet model, as well as the vibration response on the shell 1.

[0072] like Figure 7 As shown, four acceleration sensors, numbered #13 to #16, are arranged near the installation positions of the four vibration isolators 4 on the panel of the base 3 to obtain the vibration response transmitted to the base 3 through the vibration isolators 4, that is, the vibration response after the vibration isolators 4 transmit the vibration. Four acceleration sensors, numbered #17 to #20, are arranged near the connection of the vibration isolator 4 on the lower panel of the floating raft 5 to obtain the vibration response of the floating raft 5 panel, that is, the vibration response before the vibration isolator 4 transmits the vibration. Two acceleration sensors, numbered #21 and #22, are arranged near the diagonal vertex of the vibratory motor 7 on the floating raft 5 to obtain the vibration response at the foot of the vibratory motor 7, which is regarded as the vibration input of the vibratory motor 7. Two accelerometers, numbered #23 and #24, are placed near the diagonal vertex of the vibrator 6 on the floating raft 5 to acquire the vibration response at the installation location of the vibrator 6 and to detect the effectiveness of the vibration isolation of the flexible installation. An accelerometer, numbered #25, is placed near the excitation point of the boss 9 to acquire the vibration response at the excitation point of the excitation rod 8. A force sensor, numbered #26, is placed at the connection point of the end of the excitation rod 8 to obtain the excitation force provided by the exciter 6. The force sensor is determined according to the excitation position. For example, if the excitation rod 8 excites the boss 9 of the floating raft 5, the force sensor is connected to the excitation rod 8 and fixed to the boss 9; if the excitation rod 8 excites the shell 1, the force sensor is connected to the excitation rod 8 and fixed to the shell 1.

[0073] The specific arrangement of external hydrophone measuring points for the underwater acoustic vibration test of the model is as follows: refer to Figure 12 Open water testing requires a dedicated floating platform 15, consisting of platforms on the left and right sides and a gantry 14 between the platforms, with lifting equipment installed on the gantry 14. After the model is launched into the water, a ten-element vertical acoustic array is used for testing. The acoustic array consists of 10 hydrophones spaced 1m apart in series.

[0074] During the experiment, the model device was lowered to a depth of 15m underwater, and the hydrophone at the top of the acoustic array was 5m above the water surface. Figure 11 As shown. Moving measurements were conducted along the outer perimeter of the floating platform 15. Eight measurement points were arranged on each of the left and right sides of the platform, with a spacing of 5 meters between adjacent measurement points; four measurement points were arranged at each of the front and rear ends, for a total of 24 moving measurement points, as shown. Figure 12 As shown. An underwater envelope region can be formed through mobile measurement, and the average sound pressure level of this region can be calculated and compared with the calculated results. The specific calculation process is not within the scope of this invention; this invention only provides the test model and test method, therefore the calculation process will not be elaborated.

[0075] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A testing method for a three-dimensional acoustoelastic model, characterized in that, A three-dimensional acoustoelastic model with a mechanical vibration isolation system is adopted. The model includes a shell (1), end plates (2) at both ends of the shell (1), and a vibration isolation system is provided inside the shell (1). The vibration isolation system includes: The base (3) is connected to the inner wall of the arc surface of the shell (1); Vibration isolator (4) is installed on the mounting plane formed on the top of the base (3); A floating raft (5) is installed on a vibration isolator (4); an excitation signal output device is installed on the floating raft (5), and the excitation signal output device is equipped with an excitation rod (8); The position of the concentrated excitation point of the vibration isolation system is adjustable; the model is suitable for vibration isolation tests in air and water environments. In water environment tests, the end plate (2) and the shell (1) form a closed test space. The test method uses a vibrator (6) and a vibration motor (7) to provide excitation signals. The excitation methods of the model include: The first method: The vibrator (6) is turned on, the vibrating rod (8) is connected to the boss (9) of the floating raft (5), and the concentrated excitation point acts on the middle of the boss (9). At the same time, the vibration motor (7) on the floating raft (5) is turned on. The second method: The vibrator (6) is turned on, the vibrating rod (8) is connected to the boss (9) of the floating raft (5), the concentrated excitation point acts on the middle of the boss (9), and the vibration motor (7) on the floating raft (5) is turned off. The third method: the exciter (6) is turned on, the exciter rod (8) is connected to the bottom shell (1) of the column shell, the concentrated excitation point acts on the shell (1), and the vibration motor (7) on the raft (5) is turned off; when the model is tested in an air environment, it is divided into the test model natural frequency and mode shape stage and the test vibration isolation transmission stage. The excitation method for the natural frequency and mode shape stages of the test model is as follows: the exciter (6) is turned on, the excitation rod (8) is connected to the bottom shell (1) of the column shell, the concentrated excitation point acts on the bottom shell (1) of the column shell, and the vibration motor (7) on the raft (5) is turned off. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing. The excitation method for the vibration isolation transmission stage is as follows: the vibrator (6) is turned on, the excitation rod (8) is connected to the boss (9) of the floating raft (5), the concentrated excitation point acts on the middle of the boss (9), and at the same time the vibration motor (7) on the floating raft (5) is turned on. Accelerometers and force sensors were installed, and the model was lifted and suspended in the air for testing. When the model is used for underwater environment testing, the following tests are conducted: wet model natural frequencies and mode shapes, vibration transmission of the underwater mechanical vibration isolation system, and acoustic radiation of the model. The testing steps are as follows: The excitation method is as follows: the vibrator (6) is turned on, the excitation rod (8) is connected to the boss (9) of the floating raft (5), the concentrated excitation point acts on the middle of the boss (9), the vibration motor (7) on the floating raft (5) is turned off, after the acceleration sensor and force sensor are arranged, the two ends of the shell (1) are closed. The model device is equipped with real-time monitoring equipment and is watertight. The model is lowered into the water to the desired depth; hydrophones are placed in the water to detect background noise. Before the formal test, the hydrophone was moved and the vibration acceleration and underwater acoustic data at each measuring point were recorded. After a test is completed, the model is lifted and the excitation method is changed as follows: the vibrator (6) is turned on, the vibrator rod (8) is connected to the boss (9) of the floating raft (5), the concentrated excitation point is applied to the middle of the boss (9), and the vibration motor (7) on the floating raft (5) is turned on at the same time. Adjust the installation position of the vibrator (6), fix the vibrator rod (8) and force sensor to ensure that the two devices simultaneously excite the raft (5), and test again.

2. The test method as described in claim 1, characterized in that, The arrangement of measuring points used in the air environment test is as follows: The accelerometer is uniformly distributed in the circumferential cross section inside the housing (1). An acceleration sensor is arranged on the panel of the base (3) corresponding to the vibration isolator (4). The vibrator (6) and vibration motor (7) of the floating raft (5) are respectively arranged with acceleration sensors at diagonal positions. A force sensor is placed at the end of the excitation rod (8).

3. The test method as described in claim 2, characterized in that: The underwater testing measurement point layout is as follows: Accelerometers are uniformly distributed along the circumferential cross-section inside the housing (1). An acceleration sensor is placed at the installation position of the vibration isolator (4) on the base (3) panel. An acceleration sensor is placed at the connection point between the floating raft (5) and the vibration isolator (4). An accelerometer is placed diagonally on the excitation signal output device on the floating raft (5). An acceleration sensor is placed at the protrusion (9) of the raft (5). A force sensor is placed at the end of the excitation rod (8).

4. The test method as described in claim 1, characterized in that, The verification process is as follows: First, a vibration test is conducted on the linear isolator (4), and then the nonlinear isolator (4) is installed and the test is conducted again. The vibration transmission characteristics of the mechanical vibration isolation system under different isolators (4) are obtained. The comparison and verification guides the design of the nonlinear isolator (4). In the time-domain and frequency-domain acoustic vibration verification methods, different signals are used for excitation. In the time-domain acoustic vibration test, under the second excitation mode, the exciter (6) emits a 1s short transient excitation signal; in the frequency-domain acoustic vibration test, under the second excitation mode, the exciter (6) emits a wide-band steady-state excitation, and the excitation signal is adjusted in real time according to the test purpose.

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