An experimental device and method for measuring the dry structural mode of a ship model

Abstract

An experimental device and method for measuring the dry structural mode of a ship model, including a sectional ship model, a suspension bracket and a vacuum chamber; a plurality of rib position frames are arranged at intervals along the length direction of the inner wall of the ship hull, the rib position frames are magnetic, and a magnetic first bow magnet and a first stern magnet are respectively arranged at the bow and stern of the sectional ship model; there are a plurality of hull magnet assemblies corresponding to the rib position frames on the suspension bracket, as well as a second bow magnet assembly and a second stern magnet assembly respectively corresponding to the first bow magnet and the first stern magnet, so that the sectional ship model is suspended inside the suspension bracket; in the vacuum environment of the vacuum chamber, the manipulator drives the shaker to apply an exciting force to the sectional ship model, thereby avoiding finding nodes, repeated unloading and lifting, and adjusting the lifting attitude of the ship model during the test, measuring the multi-point bending parameters of the dry structure of the sectional ship model at one time, improving the work efficiency, and at the same time avoiding dangerous factors and uncertain factors, and conducting the test in a vacuum environment to improve the accuracy of the test.

Description

Technical Field

[0001] The invention relates to the technical field of ship and ocean engineering model test and testing, in particular to a test device and method for modal measurement of a ship model dry structure. Background Art

[0002] The modal test of the hull structure in the air is an important task that must be carried out before the tank model test of large ships and marine structures. It is the basis for the section load test and hydroelastic analysis. Since the mass distribution and stiffness distribution of the structure of large ships will change during the scaled production process, the vibration characteristics are the determining factors for the success or failure of its processing, and are also important parameters for the tank model test. At the same time, compared with the test of modal parameters in water, the dry structure modal test is the immediate predecessor of the wet mode test in water. If the dry structure modal test finds that the ship structure parameters are inconsistent with those before the conversion or the deviation is large, the cause should be found immediately, otherwise the results obtained by the tank test cannot be verified for accuracy.

[0003] Large ships are prone to wave-induced vibration due to their large scale and low stiffness. The dry structure vibration test often needs to consider several elastic modes, and the position of these elastic mode nodes is the key condition affecting the measurement results of each order of mode. In this case, the conventional practice is to analyze the elastic mode according to numerical modeling, obtain the vibration nodes of each order, roughly measure the node position before lifting the ship model, and lift the ship model off the ground by suspension or support. However, due to the error between the numerical calculation and the actual model, in the process of finding a node, it is necessary to try to change the node position many times to measure the relevant parameters. Every time the lifting position is changed, the tightness of the rope changes due to the movement of the lifting point, which will cause the center of gravity of the ship to change during lifting, which not only affects the normal modal test results, but also has the risk of lifting and capsizing. In addition, in the process of changing from two nodes to three nodes and four nodes, it is still necessary to try to change the node position many times, which is time-consuming and labor-intensive, and it is also necessary to adjust the lifting posture of the ship model to switch between horizontal and torsional modal measurements. Not only that, there are also sensors arranged on the ship model structure or the measurement beam, which cannot provide convenient conditions for lifting and threading.

[0004] In addition, since air is thinner than water, the dry modal of the ship model structure is often tested in the air. However, the temperature, humidity in the air and the dust particles in the laboratory will more or less affect the dry modal test. The most ideal environment for testing dry modal is a vacuum state, but the ship model and the ship model suspension device occupy a large space as a whole, which is not convenient for the realization of a vacuum environment; conventional measurement methods require operators to intervene multiple times, change the suspension method and apply force to the ship model through a hammer, which cannot achieve operation in a vacuum environment, affecting the accuracy of the modal test. Summary of the invention

[0005] In view of the above-mentioned drawbacks in the existing production technology, the present applicant provides a test device and method for measuring the dry structure mode of a ship model, thereby avoiding finding nodes, repeated unloading, hoisting, and adjusting the hoisting attitude of the ship model during the dry structure mode test of the sectional ship model, and measuring the bending parameters of the two-node, three-node, four-node, etc. of the sectional ship model dry structure at one time. While improving work efficiency, it avoids risk factors and uncertain factors, and at the same time conducts tests in a vacuum environment to improve the accuracy of the test.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A test device for measuring the dry structure mode of a ship model includes a sectional ship model and a suspension bracket matching the sectional ship model;

[0008] The structure of the sectional ship model is as follows: it includes sectional ship hulls arranged side by side in sequence. Along the length direction of the ship, a plurality of rib position frames are arranged at intervals on the inner wall of each sectional ship hull. The rib position frames are U-shaped. The two ends of a single rib position frame are connected by a transverse frame. A fixed base is arranged on the upper part of each transverse frame. A plurality of fixed bases are simultaneously connected to a measuring beam arranged along the length direction of the ship. The rib position frames are made of neodymium iron boron permanent magnets and are magnetized.

[0009] A first bow magnet is installed at the longitudinal section of the bow of the sectional ship model, and a first stern magnet is installed at the longitudinal section of the tail of the sectional ship model. Both the first bow magnet and the first stern magnet are made of neodymium iron boron permanent magnets and are magnetized;

[0010] The structure of the suspension bracket is as follows: it includes a frame body. The internal space of the frame body matches the outside of the ship model. A plurality of hull magnet components are arranged at intervals along the length direction of the ship on the frame body. Each hull magnet component corresponds to the rib position frame one by one.

[0011] A second bow magnet component is arranged on the frame body corresponding to the first bow magnet, and a second stern magnet component is arranged on the frame body corresponding to the first stern magnet;

[0012] When the sectional ship model is placed above the inside of the suspension bracket, the opposite surfaces of the hull magnet components and the rib position frames have the same magnetic poles and are facing each other. The opposite surfaces of the first bow magnet and the second bow magnet component have the same magnetic poles and are facing each other. The opposite surfaces of the first stern magnet and the second stern magnet component have the same magnetic poles and are facing each other. The magnetic fields generated by the hull magnet components, the second bow magnet component, and the second stern magnet component respectively repel the magnetic fields generated by the rib position frames, the first bow magnet, and the first stern magnet, suspending the sectional ship model above the inside of the suspension bracket;

[0013] It further includes a vacuum chamber, inside which a robotic arm is arranged. An exciter is installed at the operating end of the robotic arm. When the sectional hull model is suspended above the inside of the suspension bracket and they are both placed inside the vacuum chamber, the probe of the exciter contacts the sectional hull model to apply an exciting force to the sectional hull model.

[0014] A vacuum pumping device is arranged outside the vacuum chamber, and the vacuum pumping device is connected to the inside of the vacuum chamber through a pipeline.

[0015] Its further technical solution lies in that:

[0016] The structures of the second bow magnet assembly, the second stern magnet assembly and the hull magnet assembly are the same;

[0017] The structure of the hull magnet assembly is: including an electromagnetic box with a tubular structure, one side of the electromagnetic box is connected to the frame, both ends of the electromagnetic box are closed, and a plurality of block-shaped electromagnets are installed inside the electromagnetic box. The curvature of the electromagnetic box adapts to the magnetic field direction of the hull magnet assembly.

[0018] The circuits of the second bow magnet assembly, the second stern magnet assembly and the plurality of hull magnet assemblies are connected in parallel.

[0019] A single hull magnet assembly is sectional, including a left section of the hull magnet and a right section of the hull magnet respectively located on both sides along the ship length direction. The left section of the hull magnet and the right section of the hull magnet respectively correspond to both sides of the frame of the rib position. It also includes a middle section of the hull magnet located at the bottom of the suspension bracket, and the middle section of the hull magnet corresponds to the bottom edge of the frame of the rib position;

[0020] The circuits of the left section of the hull magnet, the right section of the hull magnet and the middle section of the hull magnet are connected in parallel.

[0021] Warning lights are arranged on the second bow magnet assembly, the second stern magnet assembly and the hull magnet assembly.

[0022] One side of the vacuum chamber is open and is provided with a side cover. It further includes a hydraulic strut. When the side cover is opened, it is supported by the hydraulic strut. A sealing interface is arranged on the vacuum chamber for leading out the wires required by the test device.

[0023] The vacuum chamber is made of a transparent material.

[0024] The frame is the female mold shell for manufacturing the ship model, and the female mold shell is made by turning from a male mold made according to the lines of the target ship model. Universal wheels are installed at the lower part of the frame.

[0025] A method for measuring the dry structural mode of a ship model includes the following steps:

[0026] Preparation before testing:

[0027] Fabricate a sectional ship model and a floating bracket that matches the sectional ship model. The floating bracket is provided with a second bow magnet assembly, a second stern magnet assembly, and a hull magnet assembly that suspend the sectional ship model above the interior thereof.

[0028] The rib frames of the sectional ship model are made of neodymium iron boron permanent magnets and magnetized. At the same time, the rib frames correspond to the hull magnet assembly. A first bow magnet and a first stern magnet are respectively installed at the bow longitudinal section and the stern longitudinal section of the sectional ship model. Both the first bow magnet and the first stern magnet are made of neodymium iron boron permanent magnets and magnetized. The first bow magnet and the first stern magnet respectively correspond to the second bow magnet assembly and the second stern magnet assembly.

[0029] Place the sectional ship model:

[0030] In the case where the hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly do not generate a magnetic field at the floating bracket, place the sectional ship model inside the floating bracket.

[0031] Suspend the sectional ship model:

[0032] The hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly are all combined structures in which a plurality of block-shaped electromagnets are installed inside a tubular electromagnetic box. After placing the sectional ship model, after energizing the electromagnets of the hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly, the sectional ship model is suspended inside the floating bracket, and it is detected and confirmed that each part of the sectional ship model is separated from the floating bracket.

[0033] Dry modal test:

[0034] After the sectional ship model is suspended above the interior of the floating bracket and placed in a vacuum chamber together, a vacuum pumping device outside the vacuum chamber pumps the vacuum chamber. When the set vacuum degree is reached, a mechanical arm inside the vacuum chamber drives an exciter at the operation end of the mechanical arm to apply an exciting force to the sectional ship model, and the probe of the exciter contacts the sectional ship model.

[0035] Operate the mechanical arm to make the probe contact the upper part of the measuring beam at the bow or stern of the sectional ship model but without being stressed. Turn on the exciter and collect signals to test the vertical bending modal parameters.

[0036] Operate the mechanical arm to make the probe contact the side of the measuring beam at the bow or stern of the sectional ship model but without being stressed. Turn on the exciter and collect signals to test the horizontal bending modal parameters.

[0037] Operate the mechanical arm to make the probe contact the outer side of the ship's side of the sectional ship model at the bow or stern but without being stressed. Turn on the exciter and collect signals to test the torsional modal parameters.

[0038] After the test, restore the robotic arm to its initial state, turn off the vacuum pumping device, and return the interior of the vacuum chamber to normal pressure;

[0039] Segmented ship model de - suspension:

[0040] Cut off the power supply of the electromagnets of the hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly, remove the magnetism at the corresponding positions of the hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly of the suspension bracket, so that the segmented ship model steadily descends into the suspension bracket and no longer floats, and the measurement work is completed.

[0041] Its further technical solution lies in:

[0042] A single hull magnet assembly is segmented, including a left hull magnet segment and a right hull magnet segment respectively located on both sides along the ship length direction. The left hull magnet segment and the right hull magnet segment respectively correspond to the two side edges of the rib frame. It also includes a middle hull magnet segment located at the bottom of the suspension bracket. The middle hull magnet segment corresponds to the bottom edge of the rib frame. The circuits of the left hull magnet segment, the right hull magnet segment, and the middle hull magnet segment are connected in parallel;

[0043] In the step of suspending the segmented ship model: The segmented ship model is placed inside the suspension bracket and together placed inside the vacuum chamber. After the electromagnets are powered on, the sequence is as follows: First, power on the electromagnets at the second bow magnet assembly and the second stern magnet assembly, then power on the electromagnets at the left hull magnet segment and the right hull magnet segment, and finally power on the electromagnet at the middle hull magnet segment;

[0044] In the step of de - suspending the segmented ship model: The segmented ship model floats inside the suspension bracket and together is placed inside the vacuum chamber. The power - off sequence of the electromagnets is as follows: First, cut off the power supply of the electromagnet at the middle hull magnet segment, then cut off the power supply of the electromagnets at the left hull magnet segment and the right hull magnet segment, and finally cut off the power supply of the electromagnets at the second bow magnet assembly and the second stern magnet assembly.

[0045] The beneficial effects of the present invention are as follows:

[0046] The structure of the present invention is compact and reasonable, and the operation is convenient. By arranging a suspension bracket under the sectional ship model, and at the same time arranging magnets with the same poles facing each other at the bow and stern of the sectional ship model and at the positions of the rib positions, the suspension bracket generates a uniform counter-thrust on the outside of the sectional ship model, restricting the four sides of the sectional ship model while overcoming the gravity of the sectional ship model so that the sectional ship model does not undergo horizontal displacement, suspending the sectional ship model above the inside of the suspension bracket. Thus, when conducting the dry structure modal test of the ship model, the way of hanging is avoided, so that the sectional ship model 1 is in a state of contacting with external components, the bending nodes are avoided to be searched for, repeated unloading and hoisting are avoided, the hoisting attitude of the ship model is avoided to be adjusted, the interference-free suspension of the sectional ship model is realized at one time, the bending parameters such as two-node, three-node, and four-node of the dry structure of the sectional ship model can be measured at one time, the horizontal bending and torsional modal parameters can be tested without adjusting the state, the modal characteristics can be obtained quickly and accurately, the work efficiency is improved, and at the same time, the dangerous factors and uncertain factors in multiple hoistings are avoided; the way of the suspension bracket lifting the sectional ship model greatly reduces the space occupied by the test device, and combined with the use of a robotic arm and an exciter to apply an exciting force to the sectional ship model instead of manual operation, the dry modal test is realized under a vacuum state, further improving the accuracy of the test.

[0047] Meanwhile, the present invention also has the following advantages:

[0048] (1) The second bow magnet assembly, the second stern magnet assembly and the hull magnet assembly generate a magnetic field through an electromagnet, which is controlled by energizing and de-energizing. Without disassembling and assembling parts of the suspension bracket, the presence, absence and magnitude of the magnetic field inside the suspension bracket can be controlled by passing current through the holes, and thus the suspension and the lifting distance of the sectional ship model can be realized; at the same time, the work of disassembling and assembling permanent magnetic components manually is also reduced, further reducing the space occupied by the test device and reducing the load of the vacuum pumping device.

[0049] (2) The second bow magnet assembly, the second stern magnet assembly and a plurality of hull magnet assemblies are connected in parallel, which can avoid suspension failure caused by the open circuit of the local electromagnet coil; in addition, it is easier to check the location of the open circuit.

[0050] (3) The hull magnet assembly is segmented, which can save materials and facilitate the design and manufacture of the magnet structure while meeting the repulsive force at the rib position frame; the circuits of the left section of the hull magnet, the right section of the hull magnet and the middle section of the hull magnet are connected in parallel, which is convenient for controlling the magnetic field at different positions of the suspension bracket.

[0051] (4) The female mold shell is used as a frame, and an electromagnetic box is installed outside the female mold shell. By utilizing the perfect fit between the female mold shell and the sectional ship model, it is also convenient for the design and manufacture of the external electromagnetic box. At the same time, the frame has a better effect when carrying the sectional ship model, and the female mold shell is reused, achieving the purpose of cost saving, quality improvement and efficiency increase.

[0052] (5) In the method for measuring the modal of a sectional ship model, taking the sectional ship model as a reference, the sequence of energizing the electromagnets is first the bow and stern, then both sides, and finally the bottom of the ship; the sequence of de-energizing the electromagnets, taking the sectional ship model as a reference, is first the bottom of the ship, then both sides, and finally the bow and stern, which is used to ensure the steady suspension and de-suspension of the sectional ship model. Description of the Drawings

[0053] Figure 1 It is a schematic structural diagram of the present invention.

[0054] Figure 2 It is a schematic structural diagram of the sectional ship model and the suspension bracket of the present invention.

[0055] Figure 3 It is a side view (sectional view) of the sectional ship model and the suspension bracket of the present invention.

[0056] Figure 4 It is Figure 3 The enlarged view at A in

[0057] Figure 5 It is the working principle diagram when the opposite faces of the magnets of the sectional ship model and the suspension bracket of the present invention are facing each other.

[0058] Figure 6 It is a schematic structural diagram of the hull magnet assembly of the present invention.

[0059] Figure 7 It is Figure 6 The side view of

[0060] Figure 8 It is a schematic diagram of the parallel control of the hull magnet assembly, the second bow magnet assembly, and the second stern magnet assembly of the present invention.

[0061] Figure 9 It is a schematic diagram of the working state of the vibrator of the present invention.

[0062] Wherein: 1. Sectional ship model;

[0063] 11. Sectional hull; 12. First bow magnet; 13. Frame at rib position; 14. Measuring beam; 15. Fixed base; 16. Acceleration sensor; 17. First stern magnet; 18. Transverse frame;

[0064] 2. Suspension bracket;

[0065] 21. Frame body; 22. Second bow magnet assembly; 23. Hull magnet assembly; 231. Left section of hull magnet; 232. Right section of hull magnet; 233. Middle section of hull magnet; 23301. Electromagnetic box; 23302. Electromagnet; 23303. Warning lamp; 24. Universal wheel; 27. Second stern magnet assembly;

[0066] 3. Robotic arm; 4. Vacuum chamber; 401. Side cover; 402. Hydraulic support rod; 403. Sealing interface; 5. Vibrator; 501. Probe; 6. Vacuum pumping device. Specific implementation manner

[0067] The following combines with the attached drawings to illustrate the specific implementation manner of the present invention.

[0068] As Figures 1-9 shown, the test device for measuring the dry structural mode of the ship model in the first embodiment includes a segmented ship model 1 and a suspension bracket 2 that matches the segmented ship model 1. During the test, the suspension bracket 2 keeps the segmented ship model 1 in a suspended state.

[0069] The structure of the segmented ship model 1 is as follows: it includes segmented hulls 11 arranged side by side in sequence. Along the length direction of the ship, a plurality of rib frames 13 are arranged at intervals on the inner wall of each segmented hull 11. The rib frames 13 are U-shaped. The two ends of a single rib frame 13 are connected by a transverse frame 18. A fixed base 15 is arranged on the upper part of each transverse frame 18. A plurality of fixed bases 15 are simultaneously connected to a measuring beam 14 arranged along the length direction of the ship. The rib frames 13 are made of neodymium iron boron permanent magnets and are magnetized. In order to collect the vibration frequency and modal vibration mode of the segmented ship model 1 in the suspended state during the test, generally, acceleration sensors 16 are arranged on the measuring beam 14, and a plurality of acceleration sensors 16 correspond to the upper surface of the measuring beam 14 at the opening of the segmented ship model 1.

[0070] A first bow magnet 12 is installed at the longitudinal section of the bow of the segmented ship model 1, and a first stern magnet 17 is installed at the longitudinal section of the stern of the segmented ship model 1. Both the first bow magnet 12 and the first stern magnet 17 are made of neodymium iron boron permanent magnets and are magnetized.

[0071] The segmented hull 11 is made of fiberglass laminate and is designed in segments according to the test requirements. The frame at rib positions 13, the first bow magnet 12, and the first stern magnet 17 are connected to the segmented hull 11 by means of multi-layer fiberglass bonding. The frame at rib positions 13 and the transverse frame 18 are connected by bonding or riveting. The connection between the transverse frame 18, the fixed base 15, and the measuring beam 14 can be welded. The frame at rib positions 13, the first bow magnet 12, and the first stern magnet 17 not only serve as the skeleton of the segmented hull 11 but also have magnetism. The neodymium iron boron permanent magnets used in the production of the frame at rib positions 13, the first bow magnet 12, and the first stern magnet 17 are calculated based on the weight of the segmented ship model 1 and its load. Generally, the magnetic force of the neodymium iron boron permanent magnet is proportional to its volume. When calculating the size of the neodymium iron boron permanent magnet, the total weight of all objects in the segmented ship model 1 (including the components that make up the segmented ship model 1 and measuring instruments, etc.) should be fully estimated. According to the principle of force balance, the magnetic force generated by the neodymium iron boron permanent magnet should be greater than the total weight of all objects in the segmented ship model 1, and a safety factor of 1.5 is taken. The neodymium iron boron permanent magnet is magnetized according to the required structure and magnetic field distribution in the design to ensure that the direction of the magnetic poles meets the requirements.

[0072] The neodymium iron boron permanent magnet can be made into a single-sided magnet and is surface-treated with zinc plating.

[0073] The structure of the suspension bracket 2 is as follows: It includes a frame body 21. The internal space of the frame body 21 matches the outside of the ship model. Along the length direction of the ship, a plurality of hull magnet components 23 are arranged at intervals on the frame body 21, and each hull magnet component 23 corresponds to the position of the frame at rib positions 13 one by one.

[0074] A second bow magnet component 22 is arranged on the frame body 21 corresponding to the first bow magnet 12, and a second stern magnet component 27 is arranged on the frame body 21 corresponding to the first stern magnet 17.

[0075] The hull magnet components 23, the first stern magnet 17, and the second stern magnet component 27 are magnetic components. After being arranged on the frame body 21 and generating a magnetic field corresponding to the segmented ship model 1, the segmented ship model 1 in the suspension bracket 2 is in a suspended state. The magnetic components referred to here can be permanent magnetic or electromagnetic.

[0076] When the sectional ship model 1 is placed above the inside of the suspension bracket 2, the opposite faces of the hull magnet assembly 23 and the rib position frame 13 have the same magnetic poles and face each other directly, the opposite faces of the first bow magnet 12 and the second bow magnet assembly 22 have the same magnetic poles and face each other directly, and the opposite faces of the first stern magnet 17 and the second stern magnet assembly 27 have the same magnetic poles and face each other directly. The magnetic fields generated by the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 suspend the sectional ship model 1 above the inside of the suspension bracket 2. The magnetic fields generated by the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 repel the magnetic fields generated by the rib position frame 13, the first bow magnet 12, and the first stern magnet 17 respectively, suspending the sectional ship model 1 above the inside of the suspension bracket 2. As Figure 5 shown, the upper part represents the magnet of the sectional ship model 1, and the lower part represents the magnet of the suspension bracket 2. The opposite magnetic poles of the two opposite faces are N poles and face each other directly. Of course, the opposite faces can also be S poles.

[0077] The interaction between the rib position frame 13 of the sectional ship model 1 and the hull magnet assembly 23 of the suspension bracket 2 can generate vertical and horizontal forces, so that the sectional ship model 1 will not have horizontal displacement in the ship width direction after being lifted; the first bow magnet 12 and the first stern magnet 17 of the sectional ship model 1 face the second bow magnet assembly 22 and the second stern magnet assembly 27 of the suspension bracket 2 respectively, which are mainly used to limit the horizontal displacement of the sectional ship model 1 in the ship length direction, so that the sectional ship model 1 reaches suspension balance above the inside of the suspension bracket 2.

[0078] It also includes a vacuum chamber 4. A robotic arm 3 is arranged inside the vacuum chamber 4. An exciter 5 is installed at the operating end of the robotic arm 3. When the sectional ship model 1 is suspended above the inside of the suspension bracket 2 and placed together inside the vacuum chamber 4, the probe 501 of the exciter 5 contacts the sectional ship model 1 to apply an exciting force to the sectional ship model 1.

[0079] The exciter 5 is an off-the-shelf component and can continuously output exciting forces with different frequency components according to the setting in a vacuum state. When starting to measure the mode after the sectional ship model 1 is suspended in the suspension bracket 2, the probe 501 of the exciter 5 will output a harmonic exciting force according to the requirements, acting on the sectional ship model 1. The acceleration sensor 16 will receive and record the actual vibration process and transmit it to the data acquisition device. The robotic arm 3 is also an off-the-shelf component and is a common handling operation structure in the automation field.

[0080] Applying an external force with the exciter 5 has higher efficiency compared with the conventional force hammer knocking. The user of the force hammer often needs to be trained to avoid double knocking when knocking once. During the acquisition process, once double knocking occurs, it is necessary to wait for the sectional ship model 1 to stabilize before knocking and testing again. The exciter 5 can avoid this repetitive work.

[0081] A vacuum pumping device 6 is provided outside the vacuum chamber 4, and the vacuum pumping device 6 is connected to the inside of the vacuum chamber 4 through a pipeline. The vacuum pumping device 6 is a vacuum pump or a vacuum generator, which is used to pump the air inside the vacuum chamber 4, so that the air pressure inside the vacuum chamber 4 is lower than the atmospheric pressure. After reaching the set air pressure value, such as when the air pressure drops below 1 / 5 of the atmospheric pressure, the dry structural modal test of the sectional ship model 1 can be carried out.

[0082] By arranging a suspension bracket 2 under the sectional ship model 1 and setting magnets with the same poles facing each other at the bow and stern of the sectional ship model 1 and at the positions of the corresponding rib positions, a uniform reaction force is generated on the outside of the sectional ship model 1 by the suspension bracket 2. While overcoming the gravity of the sectional ship model 1, the four sides of the sectional ship model 1 are restricted so that the sectional ship model 1 will not have a horizontal displacement, and the sectional ship model 1 is suspended above the inside of the suspension bracket 2. Therefore, when carrying out the dry structural modal test of the ship model, the hanging method is avoided to make the sectional ship model 1 in a state of contact with external components, avoiding searching for bending nodes and repeated unloading and lifting, avoiding adjusting the lifting attitude of the ship model, and realizing the non-interference suspension of the sectional ship model 1 at one time. The bending parameters such as two-node, three-node, and four-node of the dry structure of the sectional ship model 1 can be measured at one time, and the horizontal bending and torsional modal parameters can be tested without adjusting the state, quickly and accurately obtaining the modal characteristics, improving the work efficiency while avoiding the risk factors and uncertain factors in multiple liftings; the way of the suspension bracket 2 supporting the sectional ship model 1 greatly reduces the space occupied by the test device. Combined with the use of a robotic arm 3 and an exciter 5 to apply an exciting force to the sectional ship model 1 instead of manual labor, the dry modal test is realized under a vacuum state, further improving the accuracy of the test.

[0083] In order to ensure that when the magnetic fields of the sectional ship model 1 and the suspension bracket 2 interact, they do not interact with their respective components and affect the direction of the suspension force, further improvements can be made in the material selection of the sectional ship model 1 and the suspension bracket 2, and non-magnetic materials are preferably selected as much as possible. The transverse frame 18, the fixed base 15, the measuring beam 14, etc. in the sectional ship model 1 can be made of materials such as aluminum, aluminum alloy or austenitic stainless steel, and the frame body 21 of the suspension bracket 2 is made of non-magnetic material, and the material is specifically selected according to the structural form.

[0084] Further, as Figures 2-7 shown, the structures of the second bow magnet assembly 22, the second stern magnet assembly 27 and the hull magnet assembly 23 are the same.

[0085] The structure of the hull magnet assembly 23 is: including an electromagnetic box 23301 with a tubular structure, one side of the electromagnetic box 23301 is connected to the frame body 21, both ends of the electromagnetic box 23301 are closed, and a plurality of block-shaped electromagnets 23302 are installed inside the electromagnetic box 23301, and the curvature of the electromagnetic box 23301 adapts to the magnetic field direction of the hull magnet assembly 23.

[0086] The electromagnet 23302 includes a magnetic core and a coil wound around the magnetic exterior. The coil is connected to an electric control terminal located outside the vacuum chamber 4. The electric control terminal is used for the circuit control of the electromagnet 23302 and the control of devices such as the robotic arm 3 and the vibrator 5. The relevant circuits of the robotic arm 3, the acceleration sensor 16, the vibrator 5, and the relevant circuit of the coil are led out through a sealed interface 403 provided on the vacuum chamber 4.

[0087] The electromagnetic box 23301 is made of non-magnetic material. Its tubular structure can be the tubular structure of the electromagnetic box 23301 component, or it can be a tubular structure formed by the combination of the connection surface at the opening in the length direction of the electromagnetic box 23301 and the frame 21. The tubular electromagnetic box 23301 is mainly used to house the electromagnet 23302 and maintain the state of the electromagnet 23302.

[0088] The electromagnets 23302 with multiple block structures are connected end to end and arranged inside the electromagnetic box 23301 with a certain curvature, and are spliced to form a magnet with a certain curvature requirement. The closed structures at both ends of the electromagnetic box 23301 are detachable structures for initial installation and later maintenance.

[0089] Specifically, it is set that the second bow magnet assembly 22, the second stern magnet assembly 27, and the hull magnet assembly 23 generate a magnetic field through the electromagnet 23302, which is controlled by energizing and de-energizing. Without disassembling and assembling parts of the suspension bracket 2, the control of the presence, absence, and magnitude of the magnetic field inside the suspension bracket 2 can be achieved by controlling the through-hole current, thereby realizing whether the segmented ship model 1 floats or not and the lifting distance; at the same time, it also reduces the manual work of disassembling and assembling permanent magnet components, further reduces the space occupied by the test device, and reduces the load on the vacuum pumping device 6.

[0090] Furthermore, as Figure 8 shown, the circuits of the second bow magnet assembly 22, the second stern magnet assembly 27, and multiple hull magnet assemblies 23 are connected in parallel.

[0091] Adopting the parallel connection method can avoid the suspension failure caused by the open circuit of the coil of the local electromagnet 23302; in addition, for a parallel circuit, it is easier to check the location of the open circuit through a multimeter.

[0092] As Figure 3 shown, a single hull magnet assembly 23 is segmented, including a left hull magnet segment 231 and a right hull magnet segment 232 located on both sides along the ship length direction respectively. The left hull magnet segment 231 and the right hull magnet segment 232 respectively correspond to both sides of the rib frame 13, and also include a middle hull magnet segment 233 located at the bottom of the suspension bracket 2. The middle hull magnet segment 233 corresponds to the bottom edge of the rib frame 13;

[0093] The circuits of the left section 231 of the hull magnet, the right section 232 of the hull magnet, and the middle section 233 of the hull magnet are connected in parallel.

[0094] As Figure 3 , Figure 6 shown, the structures of the left section 231 of the hull magnet, the right section 232 of the hull magnet, and the middle section 233 of the hull magnet are the same. The structure of the middle section 233 of the hull magnet is as follows: it includes an electromagnetic box 23301 with a tubular structure. One side of the electromagnetic box 23301 is connected to the frame 21. Both ends of the electromagnetic box 23301 are closed, and a plurality of block-shaped electromagnets 23302 are installed inside the electromagnetic box 23301.

[0095] The hull magnet assembly 23 is segmented, which can save materials and facilitate the design and manufacture of the magnet structure while meeting the repulsive force at the rib position frame 13. The circuits of the left section 231 of the hull magnet, the right section 232 of the hull magnet, and the middle section 233 of the hull magnet are connected in parallel, which is convenient for controlling the magnetic fields at different positions of the suspension bracket 2.

[0096] As Figure 3 , Figure 4 , Figure 6 , Figure 8 shown, warning lights 23303 are provided on the second bow magnet assembly 22, the second stern magnet assembly 27, and the hull magnet assembly 23.

[0097] The warning lights 23303 can be set outside the corresponding electromagnetic box 23301 of the second bow magnet assembly 22, the second stern magnet assembly 27, and the hull magnet assembly 23, which is convenient for the operator to observe. They can also be set on the circuit of the electromagnet 23302 or on the display screen at the electric control end, which is convenient for integrated observation.

[0098] As Figure 1 shown, one side of the vacuum chamber 4 is open and provided with a side cover 401. It also includes a hydraulic strut 402. When the side cover 401 is opened, it is supported by the hydraulic strut 402. A sealing interface 403 is provided on the vacuum chamber 4 for leading out the wires required for the test device.

[0099] The vacuum chamber 4 is made of a transparent material, which is convenient for the testers outside the vacuum chamber 4 to observe, record, and operate. The specific material can be selected as acrylic or other transparent materials with high strength.

[0100] The frame 21 is mainly used to provide an installation foundation for the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27. The frame 21 can be a frame structure or a shell-like structure. After the segmented ship model 1 is placed in the internal space of the frame 21, the gap between the internal space of the frame 21 and the segmented ship model 1 is greater than or equal to zero.

[0101] As Figures 1-3As shown in the figure, the frame body 21 is the female mold shell for manufacturing a ship model. The female mold shell is made by replicating a male mold made according to the lines of the target ship model. A universal wheel 24 is installed at the lower part of the frame body 21. The universal wheel 24 facilitates the movement of the suspension bracket 2 and the overall movement of the suspension bracket 2 and the sectional ship model 1.

[0102] The female mold shell is generally made of fiberglass. Since ship models are often only made in one piece for relevant experimental performance analysis, the female mold shell is discarded after the hull line is finalized, and the utilization rate of the female mold is extremely low. Using the female mold shell as the frame body 21, an electromagnetic box 23301 is installed outside the female mold shell, generally by pasting. Taking advantage of the perfect fit between the female mold shell and the sectional ship model 1, it is also convenient for the design and manufacture of the external electromagnetic box 23301. At the same time, the frame body 21 has a better effect when carrying the sectional ship model 1, and the female mold shell is reused, achieving the purpose of cost savings and efficiency improvement. The material of the electromagnetic box 23301 can be fiberglass.

[0103] The method for measuring the dry structural mode of the ship model in Embodiment 2 includes the following steps:

[0104] Preparation before testing: Manufacture the sectional ship model 1 and the suspension bracket 2 matching the sectional ship model 1. The suspension bracket 2 is provided with a second bow magnet assembly 22, a second stern magnet assembly 27, and a hull magnet assembly 23 for suspending the sectional ship model 1 above its interior. The rib frame 13 of the sectional ship model 1 is made of neodymium iron boron permanent magnet and magnetized. At the same time, the rib frame 13 corresponds to the hull magnet assembly 23. A first bow magnet 12 and a first stern magnet 17 are respectively installed at the bow longitudinal section and the stern longitudinal section of the sectional ship model 1. The first bow magnet 12 and the first stern magnet 17 are both made of neodymium iron boron permanent magnet and magnetized. The first bow magnet 12 and the first stern magnet 17 respectively correspond to the second bow magnet assembly 22 and the second stern magnet assembly 27. An acceleration sensor 16 is arranged on the measuring beam 14 and connected to a data acquisition device.

[0105] Place the sectional ship model 1: Place the sectional ship model 1 inside the suspension bracket 2 when the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 do not generate a magnetic field at the suspension bracket 2.

[0106] Suspend the sectional ship model 1: The hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 are all combined structures with a plurality of block-shaped electromagnets 23302 installed inside a tubular electromagnetic box 23301. After placing the sectional ship model 1, after energizing the electromagnets 23302 of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27, the sectional ship model 1 is suspended inside the suspension bracket 2, and it is detected and confirmed that each part of the sectional ship model 1 is separated from the suspension bracket 2.

[0107] Dry modal test: After the sectional ship model 1 is suspended above the inside of the suspension bracket 2 and placed together inside the vacuum chamber 4, the vacuum pumping device 6 outside the vacuum chamber 4 pumps the vacuum chamber 4. When the set vacuum degree is reached, the manipulator 3 inside the vacuum chamber 4 drives the shaker 5 at the operating end of the manipulator 3 to apply an exciting force to the sectional ship model 1, and the probe 501 of the shaker 5 contacts the sectional ship model 1. Operate the manipulator 3 to make the probe 501 contact the upper part of the measuring beam 14 at the bow or stern of the sectional ship model 1 but without force, turn on the shaker 5, and collect signals to test the vertical bending modal parameters; Operate the manipulator 3 to make the probe 501 contact the side of the measuring beam 14 at the bow or stern of the sectional ship model 1 but without force, turn on the shaker 5, and collect signals to test the horizontal bending modal parameters; Operate the manipulator 3 to make the probe 501 contact the outer side of the ship's side of the sectional ship model 1 at the bow or stern but without force, turn on the shaker 5, and collect signals to test the torsional modal parameters; After the test is completed, restore the manipulator 3 to its initial state, turn off the vacuum pumping device 6, and return the inside of the vacuum chamber 4 to normal pressure.

[0108] Desuspension of the sectional ship model 1: Cut off the power supply of the electromagnets 23302 of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27, remove the magnetism at the corresponding positions of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 of the suspension bracket 2, so that the sectional ship model 1 steadily descends into the suspension bracket 2 and no longer floats, and the measurement work is completed.

[0109] For the above method of measuring the modal of the sectional ship model, a new suspension type dry structural modal test system is built. There is no need to find the bending nodes, no need to consider the tightness of the elastic rope, and no need to unload and lift the ship model repeatedly. Just energize the electromagnets 23302 of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 on the suspension bracket 2 to realize the suspension of the sectional ship model in the suspension bracket 2. The vertical two-node, three-node, four-node and other bending parameters of the dry structure can be measured at one time. At the same time, the horizontal bending and torsional bending parameters can be tested, and the modal characteristics can be obtained accurately and quickly. By using the manipulator 3 and the shaker 5 to replace manual labor to apply the exciting force to the sectional ship model 1, the dry modal test is realized under the vacuum state, and the accuracy of the test is further improved.

[0110] The method for measuring the dry structural modal of the ship model in Embodiment 3 includes the following steps:

[0111] Preparation before testing: Fabricate a sectional ship model 1 and a suspension bracket 2 that matches the sectional ship model 1. On the suspension bracket 2, there are a second bow magnet assembly 22, a second stern magnet assembly 27, and a hull magnet assembly 23 that suspend the sectional ship model 1 above its interior. The frame ribs 13 of the sectional ship model 1 are made of neodymium iron boron permanent magnet and magnetized. At the same time, the frame ribs 13 correspond to the hull magnet assembly 23. A first bow magnet 12 and a first stern magnet 17 are respectively installed at the bow longitudinal section and the stern longitudinal section of the sectional ship model 1. Both the first bow magnet 12 and the first stern magnet 17 are made of neodymium iron boron permanent magnet and magnetized. The first bow magnet 12 and the first stern magnet 17 respectively correspond to the second bow magnet assembly 22 and the second stern magnet assembly 27. An acceleration sensor 16 is arranged on the measuring beam 14 and connected to a data acquisition device.

[0112] Place the sectional ship model 1: Place the sectional ship model 1 inside the suspension bracket 2 when the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 do not generate a magnetic field at the suspension bracket 2.

[0113] Suspend the sectional ship model 1: The hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 are all combined structures where the electromagnetic box 23301 with a tubular structure contains multiple block-shaped electromagnets 23302 inside. After placing the sectional ship model 1, after energizing the electromagnets 23302 of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27, the sectional ship model 1 is suspended inside the suspension bracket 2, and it is detected and confirmed that each part of the sectional ship model 1 is separated from the suspension bracket 2.

[0114] Among them, a single hull magnet assembly 23 is sectional, including a left hull magnet section 231 and a right hull magnet section 232 respectively located on both sides along the ship length direction. The left hull magnet section 231 and the right hull magnet section 232 respectively correspond to both sides of the frame ribs 13. It also includes a middle hull magnet section 233 located at the bottom of the suspension bracket 2. The middle hull magnet section 233 corresponds to the bottom edge of the frame ribs 13. The circuits of the left hull magnet section 231, the right hull magnet section 232, and the middle hull magnet section 233 are in parallel.

[0115] Specifically, after the sectional ship model 1 is placed inside the suspension bracket 2 and they are placed together inside the vacuum chamber 4, the electromagnets 23302 are energized inside the vacuum chamber 4. It can be operated through the electric control terminal, which is fast and convenient. The order of energizing the electromagnets 23302 is: first, energize the electromagnets 23302 at the second bow magnet assembly 22 and the second stern magnet assembly 27, then energize the electromagnets 23302 at the left hull magnet section 231 and the right hull magnet section 232, and finally energize the electromagnets 23302 at the middle hull magnet section 233.

[0116] Dry modal test: After the sectional ship model 1 is suspended above the inside of the suspension bracket 2 and placed together inside the vacuum chamber 4, the vacuum pump 6 outside the vacuum chamber 4 evacuates the vacuum chamber 4. When the set vacuum degree is reached, the manipulator 3 inside the vacuum chamber 4 drives the shaker 5 at the operating end of the manipulator 3 to apply an exciting force to the sectional ship model 1, and the probe 501 of the shaker 5 contacts the sectional ship model 1. Operate the manipulator 3 to make the probe 501 contact the upper part of the measuring beam 14 at the bow or stern of the sectional ship model 1 but without force, turn on the shaker 5, and collect signals to test the vertical bending modal parameters; Operate the manipulator 3 to make the probe 501 contact the side of the measuring beam 14 at the bow or stern of the sectional ship model 1 but without force, turn on the shaker 5, and collect signals to test the horizontal bending modal parameters; Operate the manipulator 3 to make the probe 501 contact the outer side of the ship's side of the sectional ship model 1 at the bow or stern but without force, turn on the shaker 5, and collect signals to test the torsional modal parameters; After the test is completed, restore the manipulator 3 to its initial state, turn off the vacuum pump 6, and return the inside of the vacuum chamber 4 to normal pressure.

[0117] Desuspension of the sectional ship model 1: Cut off the power supply of the electromagnets 23302 of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27, remove the magnetism at the corresponding positions of the hull magnet assembly 23, the second bow magnet assembly 22, and the second stern magnet assembly 27 of the suspension bracket 2, so that the sectional ship model 1 steadily descends into the suspension bracket 2 and no longer floats, and the measurement work is completed.

[0118] Specifically, when the sectional ship model 1 is suspended inside the suspension bracket 2 and placed together inside the vacuum chamber 4, the operation of cutting off the power supply of the electromagnet 23302 can be carried out inside the vacuum chamber 4, and it can be operated through the electric control end, which is fast and convenient. The power-off sequence of the electromagnet 23302 is to first cut off the power supply of the electromagnet 23302 at the middle section 233 of the hull magnet, then cut off the power supply of the electromagnets 23302 at the left section 231 and the right section 232 of the hull magnet, and finally cut off the power supply of the electromagnets 23302 at the second bow magnet assembly 22 and the second stern magnet assembly 27.

[0119] In the above method for measuring the modal of the sectional ship model, taking the sectional ship model 1 as the reference, the power-on sequence of the electromagnet 23302 is first the bow and stern, then both sides, and finally the bottom of the ship; taking the sectional ship model 1 as the reference, the power-off sequence of the electromagnet 23302 is first the bottom of the ship, then both sides, and finally the bow and stern, which is used to ensure the steady suspension and desuspension of the sectional ship model 1.

[0120] To further ensure the stability of the sectional ship model 1 during the operation, during the suspension of the sectional ship model 1: when the electromagnets 23302 at the left section 231 of the hull magnet and the right section 232 of the hull magnet are energized, the left section 231 of the hull magnet and the right section 232 of the hull magnet at the same rib position can be operated simultaneously, and at the same time, symmetric operation can be carried out with the right section 232 of the hull magnet in the middle as the center; when the electromagnets 23302 at the left section 231 of the hull magnet and the right section 232 of the hull magnet are energized, the two places are operated simultaneously; when the electromagnets 23302 at the middle section 233 of the hull magnet are energized, they are carried out sequentially from one end to the other along the ship length direction.

[0121] To further ensure the stability of the sectional ship model 1 during the operation, during the de-suspension of the sectional ship model 1: when the electromagnets 23302 at the middle section 233 of the hull magnet are de-energized, they are carried out sequentially from one end to the other along the ship length direction; when the electromagnets 23302 at the left section 231 of the hull magnet and the right section 232 of the hull magnet are de-energized, the left section 231 of the hull magnet and the right section 232 of the hull magnet at the same rib position can be operated simultaneously, and at the same time, symmetric operation can be carried out with the right section 232 of the hull magnet in the middle as the center; when the electromagnets 23302 at the second bow magnet assembly 22 and the second stern magnet assembly 27 are de-energized, the two places are operated simultaneously.

[0122] The above description is an explanation of the present invention, not a limitation of the invention. The scope defined by the present invention is referred to the claims. Within the protection scope of the present invention, any form of modification can be made.

Claims

1. An experimental device for measuring the dry structural mode of a ship model, characterized in that: it includes a sectional ship model (1) and a suspension bracket (2) matching the sectional ship model (1); The structure of the sectional ship model (1) is: it includes sectional ship hulls (11) arranged side by side in sequence, and a plurality of rib position frames (13) are arranged at intervals along the ship length direction on the inner wall of each sectional ship hull (11). The rib position frames (13) are U-shaped, and the two ends of a single rib position frame (13) are connected by a transverse frame (18). A fixed base (15) is arranged on the upper part of each transverse frame (18), and a plurality of fixed bases (15) are simultaneously connected to a measuring beam (14) arranged along the ship length direction. The rib position frames (13) are made of neodymium iron boron permanent magnets and are magnetized. A first ship bow magnet (12) is installed at the longitudinal section of the bow of the sectional ship model (1), and a first ship tail magnet (17) is installed at the longitudinal section of the tail of the sectional ship model (1). Both the first ship bow magnet (12) and the first ship tail magnet (17) are made of neodymium iron boron permanent magnets and are magnetized. The structure of the suspension bracket (2) is: it includes a frame body (21), the internal space of the frame body (21) matches the outside of the ship model, and a plurality of hull magnet assemblies (23) are arranged at intervals along the ship length direction on the frame body (21). Each hull magnet assembly (23) corresponds to the rib position frame (13) one by one. A second ship bow magnet assembly (22) is arranged on the frame body (21) corresponding to the first ship bow magnet (12), and a second ship tail magnet assembly (27) is arranged on the frame body (21) corresponding to the first ship tail magnet (17). When the sectional ship model (1) is placed above the inside of the suspension bracket (2), the opposite surfaces of the hull magnet assemblies (23) and the rib position frames (13) have the same magnetic poles and face each other directly. The opposite surfaces of the first ship bow magnet (12) and the second ship bow magnet assembly (22) have the same magnetic poles and face each other directly. The opposite surfaces of the first ship tail magnet (17) and the second ship tail magnet assembly (27) have the same magnetic poles and face each other directly. The magnetic fields generated by the hull magnet assemblies (23), the second ship bow magnet assembly (22), and the second ship tail magnet assembly (27) respectively repel the magnetic fields generated by the rib position frames (13), the first ship bow magnet (12), and the first ship tail magnet (17), suspending the sectional ship model (1) above the inside of the suspension bracket (2). It further includes a vacuum chamber (4). A robotic arm (3) is arranged inside the vacuum chamber (4), and an exciter (5) is installed at the operating end of the robotic arm (3). When the sectional ship model (1) is suspended above the inside of the suspension bracket (2) and placed together inside the vacuum chamber (4), the probe (501) of the exciter (5) contacts the sectional ship model (1) to apply an exciting force to the sectional ship model (1). A vacuum pumping device (6) is arranged outside the vacuum chamber (4), and the vacuum pumping device (6) is communicated with the inside of the vacuum chamber (4) through a pipeline.

2. The experimental device for measuring the dry structural mode of a ship model according to claim 1, characterized in that: The structures of the second ship bow magnet assembly (22), the second ship tail magnet assembly (27), and the hull magnet assemblies (23) are the same. The structure of the hull magnet assembly (23) is as follows: It includes an electromagnetic box (23301) with a tubular structure. One side of the electromagnetic box (23301) is connected to the frame (21). Both ends of the electromagnetic box (23301) are closed. Inside the electromagnetic box (23301), multiple block-shaped electromagnets (23302) are installed. The curvature of the electromagnetic box (23301) adapts to the magnetic field direction of the hull magnet assembly (23).

3. An experimental device for measuring the dry structure mode of a ship model, as described in claim 2, characterized in that: The circuits of the second bow magnet assembly (22), the second stern magnet assembly (27), and multiple hull magnet assemblies (23) are connected in parallel.

4. An experimental device for measuring the dry structure mode of a ship model, as described in claim 3, characterized in that: A single hull magnet assembly (23) is segmented, including a left hull magnet segment (231) and a right hull magnet segment (232) located on both sides along the ship length direction. The left hull magnet segment (231) and the right hull magnet segment (232) respectively correspond to the two side edges of the frame of rib positions (13). It also includes a middle hull magnet segment (233) located at the bottom of the suspension bracket (2). The middle hull magnet segment (233) corresponds to the bottom edge of the frame of rib positions (13); The circuits of the left hull magnet segment (231), the right hull magnet segment (232), and the middle hull magnet segment (233) are connected in parallel.

5. An experimental device for measuring the dry structure mode of a ship model, as described in any one of claims 1 - 4, characterized in that: Warning lights (23303) are provided on the second bow magnet assembly (22), the second stern magnet assembly (27), and the hull magnet assembly (23).

6. An experimental device for measuring the dry structure mode of a ship model, as described in claim 1, characterized in that: One side of the vacuum chamber (4) is open and is provided with a side cover (401). It also includes a hydraulic strut (402). When the side cover (401) is opened, it is supported by the hydraulic strut (402). A sealing interface (403) is provided on the vacuum chamber (4) for leading out the wires required for the experimental device.

7. An experimental device for measuring the dry structure mode of a ship model, as described in claim 6, characterized in that: The vacuum chamber (4) is made of a transparent material.

8. An experimental device for measuring the dry structure mode of a ship model, as described in claim 1, characterized in that: The frame (21) is a female mold shell for making a ship model. The female mold shell is formed by being molded from a male mold made according to the lines of the target ship model. Universal wheels (24) are installed at the lower part of the frame (21).

9. A method for measuring the dry structure mode of a ship model using the experimental device as described in claim 1, characterized in that: It includes the following steps: Preparation before testing: Fabricate a segmented ship model (1) and a suspension bracket (2) that matches the segmented ship model (1). On the suspension bracket (2), there are a second bow magnet assembly (22), a second stern magnet assembly (27), and a hull magnet assembly (23) that suspend the segmented ship model (1) above the interior thereof. The frame (13) of the sectional ship model (1) is made of neodymium iron boron permanent magnet and magnetized. At the same time, the frame (13) corresponds to the hull magnet assembly (23). A first bow magnet (12) and a first stern magnet (17) are respectively installed at the longitudinal section of the bow and the longitudinal section of the stern of the sectional ship model (1). Both the first bow magnet (12) and the first stern magnet (17) are made of neodymium iron boron permanent magnet and magnetized. The first bow magnet (12) and the first stern magnet (17) respectively correspond to the second bow magnet assembly (22) and the second stern magnet assembly (27); Place the sectional ship model (1): When the hull magnet assembly (23), the second bow magnet assembly (22) and the second stern magnet assembly (27) do not generate a magnetic field at the suspension bracket (2), place the sectional ship model (1) inside the suspension bracket (2); Suspend the sectional ship model (1): The hull magnet assembly (23), the second bow magnet assembly (22) and the second stern magnet assembly (27) are a combined structure in which a plurality of block-shaped electromagnets (23302) are installed inside a tubular electromagnetic box (23301). After placing the sectional ship model (1), after energizing the electromagnets (23302) of the hull magnet assembly (23), the second bow magnet assembly (22) and the second stern magnet assembly (27), the sectional ship model (1) is suspended inside the suspension bracket (2), and it is detected and confirmed that each part of the sectional ship model (1) is separated from the suspension bracket (2); Dry modal test: After the sectional ship model (1) is suspended above the inside of the suspension bracket (2) and placed in the vacuum chamber (4) together, the vacuum pumping device (6) outside the vacuum chamber (4) pumps the vacuum chamber (4). When the set vacuum degree is reached, the manipulator (3) located inside the vacuum chamber (4) drives the exciter (5) at the operating end of the manipulator (3) to apply an exciting force to the sectional ship model (1). The probe (501) of the exciter (5) contacts the sectional ship model (1), Operate the manipulator (3) to make the probe (501) contact the upper part of the measuring beam (14) but not be stressed at the bow or stern of the sectional ship model (1). Turn on the exciter (5) and collect signals to test the vertical bending modal parameters, Operate the manipulator (3) to make the probe (501) contact the side of the measuring beam (14) but not be stressed at the bow or stern of the sectional ship model (1). Turn on the exciter (5) and collect signals to test the horizontal bending modal parameters, Operate the manipulator (3) to make the probe (501) contact the outer side of the ship's side of the sectional ship model (1) but not be stressed at the bow or stern of the sectional ship model (1). Turn on the exciter (5) and collect signals to test the torsional modal parameters, After the test is completed, restore the manipulator (3) to its initial state, turn off the vacuum pumping device (6), and restore the inside of the vacuum chamber (4) to normal pressure; Remove the suspension of the sectional ship model (1): Cut off the power supply of the electromagnets (23302) of the hull magnet assembly (23), the second bow magnet assembly (22) and the second stern magnet assembly (27), and remove the magnetism at the corresponding positions of the hull magnet assembly (23), the second bow magnet assembly (22) and the second stern magnet assembly (27) of the suspension bracket (2), so that the segmented ship model (1) steadily descends into the suspension bracket (2) and no longer floats, completing the measurement work.

10. A method for measuring the dry structural mode of a ship model as described in claim 9, characterized in that: A single hull magnet assembly (23) is segmented, including a left hull magnet segment (231) and a right hull magnet segment (232) respectively located on both sides along the ship length direction. The left hull magnet segment (231) and the right hull magnet segment (232) respectively correspond to the two side edges of the rib position frame (13). It also includes a middle hull magnet segment (233) located at the bottom of the suspension bracket (2), and the middle hull magnet segment (233) corresponds to the bottom edge of the rib position frame (13). The circuits of the left hull magnet segment (231), the right hull magnet segment (232) and the middle hull magnet segment (233) are connected in parallel; In the step of suspending the segmented ship model (1): The segmented ship model (1) is placed inside the suspension bracket (2) and together placed inside the vacuum chamber (4). After the electromagnet (23302) is powered on, the sequence is as follows: First, power on the electromagnets (23302) at the second bow magnet assembly (22) and the second stern magnet assembly (27), then power on the electromagnets (23302) at the left hull magnet segment (231) and the right hull magnet segment (232), and finally power on the electromagnet (23302) at the middle hull magnet segment (233); In the step of de - suspending the segmented ship model (1): The segmented ship model (1) floats inside the suspension bracket (2) and together is placed inside the vacuum chamber (4). The power - off sequence of the electromagnet (23302) is as follows: First, cut off the power supply of the electromagnet (23302) at the middle hull magnet segment (233), then cut off the power supply of the electromagnets (23302) at the left hull magnet segment (231) and the right hull magnet segment (232), and finally cut off the power supply of the electromagnets (23302) at the second bow magnet assembly (22) and the second stern magnet assembly (27).

Images