An experimental method for modal measurement of a segmented ship model with an I-shaped measurement beam

Abstract

An experimental method for modal measurement of a sectional ship model using an I-shaped measuring beam includes the following steps: First, prepare a sectional ship model and a suspension beam; Second, make initial marks on the suspension beam according to the node positions; Third, install a walking gear assembly at the initial marks on the suspension beam; install a passive wheel set on the I-shaped measuring beam; connect the walking gear assembly and the passive wheel set with a suspension rope; Fourth, lift the suspension beam to make the sectional ship model leave the ground; Fifth, obtain the frequency and vibration mode of the current sectional ship model; Sixth, after adjusting each initial node position to the corresponding new node position, repeat the operation in the fifth step; Seventh, compare the frequencies in the fifth and sixth steps and find the accurate node positions; then conduct modal measurement of the sectional ship model. It is convenient to change the suspension point position during the process of finding the nodes, safe and convenient. At the same time, the position of the suspension point can cover the entire measuring beam, making the position of finding the nodes accurate, improving the accuracy of modal measurement, and reducing the requirements for the material properties of the suspension rope.

Description

Technical Field

[0001] The present invention relates to the technical field of sectional ship model tests, and in particular to a test method for modal measurement of an I-shaped measuring beam sectional ship model. Background Art

[0002] The modal test of the hull structure in air is an important task that must be carried out before the tank model test of large ships and ocean structures, and is the basis for its sectional load test and hydroelastic analysis. During the scale-down production of large ships, the mass distribution and stiffness distribution of their structures will change. The vibration characteristics are the decisive factors for the success or failure of their processing and are also important parameters for the tank model test. At the same time, compared with the modal parameter test in water, the dry structure modal test is the preparatory work for the wet modal test in water. If the dry structure modal test finds that it is inconsistent with the ship structure parameters before conversion, the reason should be immediately found, otherwise the results obtained from the tank test cannot verify its accuracy.

[0003] In addition, due to the large scale and small stiffness of large ships, they are prone to wave-induced vibration. The dry structure vibration test often needs to consider the first four-order modes, and the position of the suspension point is the key factor affecting the measurement results of each order of modes. In this case, the conventional method is to analyze the first four-order vibration modes based on numerical modeling, obtain the vibration nodes of each order, roughly measure the node positions before lifting the sectional ship model, and place the suspension points at the node positions. Due to the error between numerical calculation and actual model production, during the process of finding the accurate nodes, it is necessary to repeatedly try to change the suspension points to measure relevant parameters. Each time the position of the suspension point is changed, due to the movement of the suspension point, the tightness of the rope changes, which will cause the balance state of the ship during lifting to change, not only affecting the normal modal test results, but also posing a risk of lifting overturning.

[0004] At the same time, in the existing hoisting technology, since the measuring beam is assembled into a sectional ship model by welding with multiple fixed supports, once the welding position of the measuring beam and the fixed support, as well as the position where the acceleration sensor is pasted, coincide with the vibration node position, it is inevitable to move the lifting rope away by a certain distance. At this time, if a rigid rope is used, it will greatly change the natural frequency of the system and significantly affect the modal measurement results. If an elastic rope is used, it is necessary to find an elastic rope with good elasticity and low stiffness. Although it will still change the frequency of the system, the impact on the results is not significant, but the cost is that the lifting process is relatively dangerous. This is because the elastic rope has a large elongation range. On the one hand, a large lifting space is required, and on the other hand, the ship model is prone to shaking, posing a considerable risk to the safety of the ship model and the safety of the measurement personnel. Summary of the Invention

[0005] In view of the above-mentioned drawbacks in the existing production technology, the present applicant provides a test method for modal measurement of an I-shaped measuring beam segmented ship model, so as to facilitate the replacement of the suspension point position during the process of finding the node, which is safe and convenient. At the same time, the position of the suspension point can cover the entire measuring beam, making the position of the node accurately found, improving the accuracy of modal measurement, and reducing the requirements for the material properties of the suspension rope.

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

[0007] A test method for modal measurement of an I-shaped measuring beam segmented ship model includes the following steps:

[0008] Step 1: Establish a segmented hull numerical model, and obtain the positions of the modal bending nodes of each order of the segmented hull through modal calculation;

[0009] After determining the scale ratio, manufacture a segmented ship model according to the structure of the segmented hull numerical model. The structure of the segmented ship model includes a segmented hull, and a plurality of frames are installed at intervals along the ship length direction inside the segmented hull. A fixed support is installed at the upper end of each frame, and the upper end of the fixed support is simultaneously connected to an I-shaped measuring beam arranged along the ship length direction;

[0010] Prepare a suspension beam according to the length of the I-shaped measuring beam.

[0011] Step 2: According to the node positions and the scale ratio in Step 1, convert the node positions on the I-shaped measuring beam of the segmented ship model as multiple initial node positions for the test, and make initial marks on the suspension beam correspondingly;

[0012] Step 3: Install walking gear assemblies at the corresponding positions of the initial marks on the suspension beam;

[0013] Paste acceleration sensors on the surface of the I-shaped measuring beam of the segmented ship model, install a plurality of passive wheel sets corresponding to the walking gear assemblies on the I-shaped measuring beam, and the passive wheel sets avoid the acceleration sensors, the connecting wires of the acceleration sensors and the fixed supports. The contact positions of the passive wheel sets and the I-shaped measuring beam are the positions of the suspension points of the segmented ship model;

[0014] Connect the walking gear assemblies and the passive wheel sets with suspension ropes;

[0015] Step 4: Lift the suspension beam to make the segmented ship model leave the ground, and ensure that the positions of the walking gear assemblies on the suspension beam and the positions of the passive wheel sets on the I-shaped measuring beam correspond to the initial node positions, and make the suspension ropes in a vertical state; and adjust to make the passive wheel sets correspond to the initial node positions; at this time, the position of the suspension point is the initial node position;

[0016] Step 5: After the segmented ship model is stabilized, strike the I-shaped measuring beam with a heavy hammer. After the signal measured by the acceleration sensor is output to the test equipment, the frequency and vibration mode of the current segmented ship model are obtained through software analysis;

[0017] Step 6: Taking the initial node positions as a reference, simultaneously adjust the positions of the traveling gear assemblies and the passive wheel groups corresponding to the individual initial node positions, so that the traveling gear assemblies and the passive wheel groups at the individual initial node positions move simultaneously to the same side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat the operation in Step 5;

[0018] Step 7: Compare the frequencies in Step 5 and Step 6;

[0019] When the frequency in Step 5 is the minimum, the initial node position is the accurate node position;

[0020] When the minimum frequency in Step 6 is less than the frequency in Step 5, take the node position where the minimum frequency appears in Step 6 as the initial node position and repeat Step 6 until the minimum frequency no longer appears at the new node position, then the accurate node position is found;

[0021] Step 8: Conduct modal measurement of the segmented ship model with the accurate node position as the suspension point position. After the modal measurement of the segmented ship model is completed, lower the hanging beam to make the segmented ship model land stably, and the test is completed.

[0022] Its further technical solution lies in:

[0023] The multiple initial node positions include the node positions of two nodes, three nodes, and four nodes.

[0024] The structure of the traveling gear assembly is as follows: It includes a gear, and the gear meshes with a rack installed at the lower part of the hanging beam. The rack is arranged along the length direction of the hanging beam. There are through holes on the hanging beam, and the through holes are oblong holes. The length direction of the through holes is the same as the length direction of the hanging beam;

[0025] A pin shaft is installed in the middle of the gear and is in transmission connection with the gear. The two ends of the pin shaft pass through the through holes and are respectively located outside both sides of the hanging beam. First suspension rings are respectively sleeved on the two ends of the pin shaft. A first handle is installed at one end of the pin shaft, and the first handle is located outside the first suspension ring. The two first suspension rings are connected to the upper end of the suspension rope.

[0026] The hanging beam is of a rectangular tubular structure. A rack is installed on the upper surface of the bottom of the hanging beam. Through holes are respectively arranged on the side walls of both sides of the hanging beam, and the two through holes correspond to each other. The gear is located between the side walls of both sides of the hanging beam, and both sides of the gear are matched with the inner sides of the side walls of the hanging beam.

[0027] Scale lines are arranged on the outer sides of the side walls of the hanging beam below the through holes.

[0028] The cross-section of the hanging beam is of I-shaped structure. The lower part of the hanging beam is a bottom plate. A vertical plate is provided in the middle of the upper surface of the bottom plate. Rack bars are respectively provided on the upper surfaces of the bottom plate on both sides of the vertical plate. A gear is installed on each rack bar. A pin shaft is simultaneously connected to the two gears for transmission. The through hole is located on the vertical plate. A limiting plate that cooperates with the outside of the gear is provided on the bottom plate outside the rack bar.

[0029] Scale lines are provided outside the rack bar.

[0030] The number of the traveling gear assemblies is five, which are distributed along the length direction of the hanging beam. The through holes in the two traveling gear assemblies located on one side of the length direction of the hanging beam are communicated with each other.

[0031] The structure of the I-shaped measuring beam is as follows: it includes upper and lower wing plates that are parallel to each other. The middle parts in the width direction of the upper and lower wing plates are connected by a web plate, and the web plate is perpendicular to the upper wing plate;

[0032] The structure of the passive wheel set is as follows: it includes two upper rollers spaced on the upper surface of the upper wing plate and lower rollers respectively provided on the lower surfaces of the upper wing plates on both sides of the web plate. The upper rollers and the lower rollers are connected by a rectangular frame structure. The upper rollers and the lower rollers are rotatably connected to the rectangular frame structure. The lower part of the rectangular frame structure is open, and the opening of the rectangular frame structure corresponds to the web plate;

[0033] A second lifting ring is installed on the rectangular frame structure outside the upper roller. The second lifting ring is connected to the lower end of the lifting rope.

[0034] A second hand crank is installed outside the upper roller. The end of the second hand crank is fixedly connected to the center of the upper roller. The rectangular frame structure passes through the end of the second hand crank and is rotatably connected to the second hand crank.

[0035] The beneficial effects of the present invention are as follows:

[0036] The structure of the present invention is compact and reasonable, and the operation is convenient. Through the traveling gear assembly that can move relative to the hanging beam and the passive wheel set that can move relative to the I-shaped measuring beam, it is convenient to change the position of the suspension point during the process of finding the node, which is safe and convenient, time-saving and labor-saving, and improves the work efficiency; the passive wheel set avoids the acceleration sensor, the acceleration sensor connecting wire and the fixed support, so that the position of the suspension point can cover the entire measuring beam, making the position of finding the node accurate, improving the accuracy of modal measurement, and at the same time reducing the requirement for the material performance of the lifting rope.

[0037] At the same time, the present invention also has the following advantages:

[0038] (1) Since through holes are provided on the hanging beam, and both ends of the pin shaft connected to the gear drive are hung with the passive pulley group by suspension ropes. When it is necessary to adjust the position of the traveling gear assembly on the hanging beam, the gear rotates relative to the rack, and at the same time, the pin shaft moves in the through hole, driving the position of the suspension rope to move so as to correspond to the node position, which is convenient for operation.

[0039] (2) The number of the traveling gear assemblies is set to five. The through holes in the two traveling gear assemblies on one side in the length direction of the hanging beam are communicated to facilitate the adjustment of the node position: when performing the conversion between the second node and the fourth node positions, only the passive pulley group needs to be increased or decreased at positions A and E to complete, without the need to repeatedly lift the sectional ship model, which is safe, convenient, time-saving and labor-saving, and improves the work efficiency; when measuring the third-order mode, there is no need to set more than 5 traveling gear assemblies, and only the single traveling gear assemblies on both sides in the length direction of the hanging beam need to be moved to the positions corresponding to the nodes, which is convenient for operation.

[0040] (3) The upper roller and the lower roller installed on the rectangular frame structure are respectively in sliding fit with the upper surface and the lower surface of the upper wing plate of the I-shaped measuring beam, which is convenient for moving the position of the passive pulley group when adjusting the new node position, and at the same time can avoid the acceleration sensor on the upper surface of the I-shaped measuring beam. The way the roller contacts the I-shaped measuring beam is line contact, which ensures the accuracy of determining the node position. Brief Description of the Drawings

[0041] Figure 1 It is a schematic structural diagram of the present invention.

[0042] Figure 2 It is a schematic diagram of an embodiment of the traveling gear assembly of the present invention.

[0043] Figure 3 It is Figure 2 a side view of.

[0044] Figure 4 It is Figure 3 an enlarged view at F of.

[0045] Figure 5 It is a schematic diagram of another embodiment of the traveling gear assembly of the present invention.

[0046] Figure 6 It is Figure 5 a side view of.

[0047] Wherein: 1. Suspension beam; 11. Rack; 12. Through hole; 13. Scale line; 14. Bottom plate; 15. Vertical plate; 2. Traveling gear assembly; 21. Gear; 22. Pin shaft; 23. First handle; 3. Suspension rope; 31. First suspension ring; 32. Second suspension ring; 4. Passive wheel set; 401. Upper roller; 402. Rectangular frame structure; 403. Lower roller; 404. Second hand crank handle; 5. I-shaped measuring beam; 501. Upper flange; 502. Web; 503. Lower flange; 6. Fixed support; 7. Segmented hull. Detailed implementation manners

[0048] The following combines with the attached drawings to illustrate the detailed implementation manners of the present invention.

[0049] As Figures 1-6 shown, the test method for modal measurement of the I-shaped measuring beam segmented ship model in Embodiment 1 includes the following steps:

[0050] Step 1: Establish a numerical model of the segmented hull, and obtain the bending node positions of each order of the segmented hull through modal calculation;

[0051] After determining the scale ratio, manufacture a segmented ship model according to the structure of the segmented hull numerical model. The structure of the segmented ship model includes a segmented hull 7. Inside the segmented hull 7, a plurality of frames are installed at intervals along the ship length direction. At the upper end of each frame, a fixed support 6 is installed. The upper end of the fixed support 6 is simultaneously connected to an I-shaped measuring beam 5 arranged along the ship length direction; the I-shaped measuring beam 5 is generally welded to the fixed support 6.

[0052] Prepare a suspension beam 1 according to the length of the I-shaped measuring beam 5; the stiffness of the I-shaped measuring beam 5 is generally less than the stiffness of the suspension beam 1.

[0053] Step 2: According to the node positions and scale ratio in Step 1, convert the node positions on the I-shaped measuring beam 5 of the segmented ship model into multiple initial node positions for the test, and make initial marks on the suspension beam 1 correspondingly;

[0054] A reference line is set on the suspension beam 1 as the basis for the upper and lower correspondence between the suspension beam 1 and the I-shaped measuring beam 5; when the length dimension of the suspension beam 1 can be exactly the same as that of the I-shaped measuring beam 5, when the two ends of the suspension beam 1 and the I-shaped measuring beam 5 are aligned, the upper and lower correspondence between the suspension beam 1 and the I-shaped measuring beam 5 is realized, which is convenient for the marks on the suspension beam 1 to correspond to the initial node positions;

[0055] Step 3: Install traveling gear assemblies 2 at the corresponding positions of the initial marks on the suspension beam 1;

[0056] An acceleration sensor is pasted on the surface of the I-shaped measuring beam 5 of the sectional ship model. A plurality of passive wheel sets 4 corresponding to the traveling gear assembly 2 are installed on the I-shaped measuring beam 5. The passive wheel sets 4 avoid the acceleration sensor, the acceleration sensor connecting wire, and the fixed support 6. The contact position of the passive wheel sets 4 and the I-shaped measuring beam 5 is the position of the suspension point of the sectional ship model;

[0057] The traveling gear assembly 2 and the passive wheel sets 4 are connected by a suspension rope 3;

[0058] The acceleration sensor is used to measure the acceleration of each section of the sectional ship model to obtain the vibration dry mode of the sectional ship model;

[0059] Step 4: Lift the lifting beam 1 to lift the sectional ship model off the ground, and ensure that the position of the traveling gear assembly 2 on the lifting beam 1 and the position of the passive wheel sets 4 on the I-shaped measuring beam 5 both correspond to the initial node position, so that the suspension rope 3 is in a vertical state; and adjust to make the passive wheel sets 4 correspond to the initial node position; at this time, the position of the suspension point is the initial node position; in order to make the suspension rope 3 in a vertical state, a plumb bob reference can be used.

[0060] Step 5: After the sectional ship model is stable, strike the I-shaped measuring beam 5 with a force hammer. After the signal measured by the acceleration sensor is output to the test equipment, the frequency and vibration mode of the current sectional ship model are obtained through software analysis;

[0061] Step 6: Based on the initial node position, simultaneously adjust the positions of the traveling gear assembly 2 and the passive wheel sets 4 corresponding to a single initial node position, so that the traveling gear assembly 2 and the passive wheel sets 4 at a single initial node position both move to the same side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat the operation in Step 5;

[0062] This step is used to find a more accurate node position. There are various combination methods for adjusting the position of the new node in this step. For example, each new node position can be on both sides of the initial node position, obtaining various combined position conditions, and respectively measuring the frequency and vibration mode of the sectional ship model under the corresponding position conditions, and finding the position of the suspension point where the minimum frequency appears;

[0063] When moving the node position of the I-shaped measuring beam 5, moving the traveling gear assembly 2 and the passive wheel sets 4 together can ensure that the sectional ship model remains horizontal in the air, that is, it does not rotate forward and backward. On the one hand, it is for the safety of the sectional ship model and the measurement personnel, and on the other hand, it is to reduce the vibration measurement error caused by the offset of the force application point during measurement.

[0064] Step 7: Compare the frequencies in Step 5 and Step 6;

[0065] If the frequency in Step 5 is the smallest, the initial node position is the accurate node position;

[0066] When the minimum frequency in Step 6 is less than the frequency in Step 5, use the node position where the minimum frequency appears in Step 6 as the initial node position and repeat Step 6 until the minimum frequency no longer appears at the new node position, then the accurate node position is found.

[0067] Step 8: Conduct modal measurement on the sectional ship model with the accurate node position as the suspension point position. After the modal measurement of the sectional ship model is completed, lower the suspension beam 1 to make the sectional ship model land stably and complete the test.

[0068] As Figure 1 shown, multiple initial node positions include the node positions of two-node, three-node, and four-node. When measuring the second-order mode, the initial node positions are at B and D corresponding to the two-node; when measuring the third-order mode, the initial node positions are between B and D, at C, and between C and D; when measuring the fourth-order mode, the initial node positions are at A, B, D, and E corresponding to the four-node. Of course, for the convenience of subsequent measurement, all initial marks can be made on the suspension beam 1.

[0069] Through the traveling gear assembly 2 that can move relative to the suspension beam 1 and the passive wheel set 4 that can move relative to the I-shaped measuring beam 5, it is convenient to change the position of the suspension point during the process of finding the node, which is safe, convenient, time-saving and labor-saving, and improves work efficiency; the passive wheel set 4 avoids the acceleration sensor, the acceleration sensor connecting wire and the fixed support 6, so that the position of the suspension point can cover the entire measuring beam, making the position of finding the node accurate, improving the accuracy of modal measurement, and at the same time reducing the requirement for the material performance of the suspension rope 3.

[0070] This method reduces the requirement for the material of the suspension rope 3 and adopts a method of accurately finding the node position. As long as the passive wheel set 4 is actually installed at the vibration node position, the modal measurement result is quite accurate. In this method, the suspension rope 3 can be an elastic rope or a rigid rope, and a rope with a lower elastic modulus and high strength is preferably used.

[0071] The traditional suspension method is to wind the elastic rope around the I-shaped measuring beam 5. If there is an acceleration sensor at the lower end of the I-shaped measuring beam 5 at the upper initial node, the elastic rope cannot pass around the lower end of the I-shaped measuring beam 5, resulting in an incorrect dry frequency for the measurement of this node position. In this embodiment, the passive wheel set 4 is cleverly arranged on the upper surface of the I-shaped measuring beam 5, which can avoid the acceleration sensor on the upper surface of the I-shaped measuring beam 5 and does not require the elastic rope to pass through the lower part of the I-shaped measuring beam 5, facilitating hoisting and the movement of the node position.

[0072] As Figures 2-4 shown, in the test method for modal measurement of the sectional ship model with the I-shaped measuring beam in Embodiment 2: The steps are the same as those in Embodiment 1, where:

[0073] The structure of the traveling gear assembly 2 is as follows: it includes a gear 21, the gear 21 is meshed with a rack 11 installed at the lower part of the hanging beam 1, the rack 11 is arranged along the length direction of the hanging beam 1, and the hanging beam 1 is provided with a through hole 12, the through hole 12 is an elongated hole, and the length direction of the through hole 12 is consistent with the length direction of the hanging beam 1;

[0074] A pin shaft 22 transmission-connected to the gear 21 is installed in the middle of the gear 21, and both ends of the pin shaft 22 pass through the through hole 12 and are respectively located on the outside of both sides of the suspension beam 1, and both ends of the pin shaft 22 are respectively provided with a first lifting ring 31, and a first handle 23 is installed at one end of the pin shaft 22, and the first handle 23 is located on the outside of the first lifting ring 31, and the two first lifting rings 31 are connected to the upper end of the lifting rope 3.

[0075] In step four and step six, since a through hole 12 is provided on the suspension beam 1, the two ends of the pin shaft 22 which is transmission-connected to the gear 21 hang the passive wheel group 4 through the suspension rope 3. When the position of the traveling gear assembly 2 on the suspension beam 1 needs to be adjusted, by shaking the first handle 23, the gear 21 rotates relative to the rack 11, and at the same time the pin shaft 22 moves in the through hole 12, driving the position of the suspension rope 3 to move so that it corresponds to the node position, which is convenient for operation.

[0076] The suspension beam 1 is a rectangular tubular structure, with a rack 11 installed on the bottom upper surface of the suspension beam 1. Through holes 12 are respectively arranged on the side walls on both sides of the suspension beam 1. The two through holes 12 correspond to each other. The gear 21 is located between the side walls on both sides of the suspension beam 1, and the two sides of the gear 21 cooperate with the inner side of the side walls of the suspension beam 1.

[0077] The hanging beam 1 of the rectangular tubular structure can adopt the profile of the existing structure, which is convenient for manufacturing the hanging beam 1. The rack 11 is installed between the side walls of the hanging beam 1, which is safe and convenient.

[0078] A scale line 13 is arranged on the outer side of the side wall of the suspension beam 1 below the through hole 12. The scale line 13 can be set to the minimum scale according to the node displacement.

[0079] By setting the scale lines 13, the reference line and the initial node position set on the suspension beam 1 can be accurately marked, and the corresponding new node position can be accurately displayed, which is convenient for observation and data recording during the experiment.

[0080] like Figures 5-6 As shown, in the test method for modal measurement of segmented ship model of I-shaped measuring beam in embodiment 3, the steps are basically the same as those in embodiment 2, wherein the structure of the hanging beam 1 is improved, and the structure of the traveling gear assembly 2 is adjusted:

[0081] The cross-section of the hanging beam 1 is an I-shaped structure. The lower part of the hanging beam 1 is a bottom plate 14. In the middle of the upper surface of the bottom plate 14, a vertical plate 15 is provided. Rack bars 11 are respectively arranged on the upper surfaces of the bottom plate 14 on both sides of the vertical plate 15. A gear 21 is installed on each rack bar 11. A pin shaft 22 is simultaneously connected to the two gears 21 for transmission. A through hole 12 is located on the vertical plate 15. A limiting plate that cooperates with the outside of the gear 21 is arranged on the bottom plate 14 outside the rack bar 11.

[0082] By adopting the hanging beam 1 with an I-shaped cross-section and setting the number of gears 21 in the traveling gear assembly 2 to two, which are respectively located on the bottom plate 14 on both sides of the vertical plate 15, the area of the force-bearing part is increased, and at the same time, the stability of the gear 21 during walking is improved.

[0083] A scale line 13 is arranged outside the rack bar 11. The scale line 13 can set the minimum scale according to the node displacement situation.

[0084] By setting the scale line 13, the reference line set on the hanging beam 1 and the initial node position can be accurately marked, and the corresponding new node positions can be accurately displayed, which is convenient for data recording during observation and experiments.

[0085] As Figures 1-6 shown, in the test method for measuring the sectional ship model modal of the I-shaped measuring beam in Embodiment 4:

[0086] On the basis of Embodiment 1, Embodiment 2 and Embodiment 3, as Figure 1 shown, the number of traveling gear assemblies 2 is set to five, which are distributed along the length direction of the hanging beam 1. The through holes 12 in the two traveling gear assemblies 2 located on one side of the length direction of the hanging beam 1 are communicated. That is, one through hole 12 is arranged on each side of the length direction of the hanging beam 1 corresponding to the two traveling gear assemblies 2 at A and B and the two traveling gear assemblies 2 at D and E, and one through hole 12 is arranged in the middle of the length direction of the hanging beam 1 corresponding to the traveling gear assembly 2 at C in the middle of the length direction of the hanging beam 1.

[0087] To ensure the stiffness of the hanging beam 1, the total length of the through holes 12 should not exceed 1 / 5 of the length of the hanging beam 1 as much as possible.

[0088] When measuring the second-order mode, the initial node positions are the two nodes corresponding to B and D. The single traveling gear assemblies 2 on both sides of the length direction of the hanging beam 1 are corresponded to the node positions, and at the same time, they are connected to the corresponding two passive wheel groups 4 on the I-shaped measuring beam 5 through the suspension ropes 3.

[0089] When measuring the fourth-order mode, the initial node positions are at the four nodes corresponding to points A, B, D, and E. After measuring the second-order mode, a traveling gear assembly 2 is added to each side of the length direction of the hanging beam 1, and at the same time, it is connected to the traveling gear assemblies 2 on both sides of the hanging beam 1 through the suspension ropes 3, so that the number of traveling gear assemblies 2 is four and corresponds to the corresponding node positions.

[0090] When performing the two-node and four-node position conversions, it only needs to add or subtract the passive wheel sets 4 at points A and E to complete, without the need to repeatedly lift and segment the ship model. It is safe, convenient, time-saving and labor-saving, and improves work efficiency. The through holes 12 in the two traveling gear assemblies 2 on one side of the length direction of the hanging beam 1 are connected to facilitate the adjustment of the node positions.

[0091] When measuring the third-order mode, the initial node positions are between the three nodes corresponding to points B and D, point C, and between points C and D; there is no need to set more than 5 traveling gear assemblies 2, and only need to move the single traveling gear assemblies 2 on both sides of the length direction of the hanging beam 1 to the positions corresponding to the nodes, which is convenient for operation.

[0092] As Figures 2-6 shown, in addition, in the present invention, the structure of the I-shaped measuring beam 5 is: including the upper wing plate 501 and the lower wing plate 503 that are parallel to each other, and the middle parts of the upper wing plate 501 and the lower wing plate 503 in the width direction are connected by the web 502, and the web 502 is perpendicular to the upper wing plate 501;

[0093] The structure of the passive wheel set 4 is that the upper rollers 401 are arranged at intervals on the upper surface of the upper wing plate 501, and the lower rollers 403 are respectively arranged on the lower surface of the upper wing plate 501 on both sides of the web 502. The upper rollers 401 and the lower rollers 403 are connected by a rectangular frame structure 402. The upper rollers 401 and the lower rollers 403 are rotatably connected to the rectangular frame structure 402. The lower part of the rectangular frame structure 402 is open, and the opening of the rectangular frame structure 402 corresponds to the web 502;

[0094] A second suspension ring 32 is installed on the rectangular frame structure 402 outside the upper roller 401, and the second suspension ring 32 is connected to the lower end of the suspension rope 3.

[0095] A second hand crank 404 is installed outside the upper roller 401. The end of the second hand crank 404 is fixedly connected to the center of the upper roller 401. The rectangular frame structure 402 passes through the end of the second hand crank 404 and is rotatably connected to the second hand crank 404.

[0096] The upper roller 401 and the lower roller 403 installed on the rectangular frame structure 402 are respectively in sliding fit with the upper surface and the lower surface of the upper wing plate 501 of the upper part of the I-shaped measuring beam 5, and the upper wing plate 501 is clamped between the upper roller 401 and the lower roller 403, which is convenient for moving the position of the passive wheel set 4 when adjusting the position of a new node. At the same time, the acceleration sensor on the upper surface of the I-shaped measuring beam 5 can be avoided. In this embodiment, the roller contact method with the I-shaped measuring beam 5 is adopted, which belongs to line contact, and the accuracy of determining the position of the node is guaranteed. While the traditional elastic rope itself has a certain width, and its contact with the I-shaped measuring beam 5 is surface contact, which has a certain impact on the measurement accuracy.

[0097] In Step 4 and Step 6, when it is necessary to adjust the position of the passive wheel set 4 on the I-shaped measuring beam 5, move the passive wheel set 4 to make the upper roller 401 and the lower roller 403 roll on the upper wing plate 501.

[0098] Furthermore, a second hand crank 404 is provided. By rotating the second hand crank 404, the upper roller 401 rotates to drive the passive wheel set 4 to move, which is convenient for operation.

[0099] 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. Any form of modification can be made within the protection scope of the present invention.

Claims

1. An experimental method for modal measurement of a sectional ship model with an I-shaped measurement beam, characterized in that: It includes the following steps: Step 1: Establish a sectional hull numerical model, and obtain the bending node positions of each order of the sectional hull through modal calculation; After determining the scale ratio, manufacture a sectional ship model according to the structure of the sectional hull numerical model. The structure of the sectional ship model includes a sectional hull (7). Inside the sectional hull (7), a plurality of frames are installed at intervals along the ship length direction. At the upper end of each frame, a fixed support (6) is installed. The upper end of the fixed support (6) is simultaneously connected to an I-shaped measurement beam (5) arranged along the ship length direction; Prepare a lifting beam (1) according to the length of the I-shaped measurement beam (5); Step 2: According to the node positions and scale ratio in Step 1, convert the node positions on the I-shaped measurement beam (5) of the sectional ship model as multiple initial node positions for the test, and make initial marks on the lifting beam (1) correspondingly; Step 3: Install traveling gear assemblies (2) at the corresponding positions of the initial marks on the lifting beam (1); paste acceleration sensors on the surface of the I-shaped measurement beam (5) of the sectional ship model, and install a plurality of passive wheel sets (4) corresponding to the traveling gear assemblies (2) on the I-shaped measurement beam (5). The passive wheel sets (4) avoid the acceleration sensors, the acceleration sensor connecting wires and the fixed supports (6). The contact positions of the passive wheel sets (4) with the I-shaped measurement beam (5) are the positions of the suspension points of the sectional ship model; connect the traveling gear assemblies (2) and the passive wheel sets (4) with a lifting rope (3); Step 4: Lift the lifting beam (1) to make the sectional ship model leave the ground, and ensure that the positions of the traveling gear assemblies (2) on the lifting beam (1) and the positions of the passive wheel sets (4) on the I-shaped measurement beam (5) correspond to the initial node positions, and make the lifting rope (3) in a vertical state; and adjust to make the passive wheel sets (4) correspond to the initial node positions; at this time, the position of the suspension point is the initial node position; Step 5: After the sectional ship model is stable, strike the I-shaped measurement beam (5) with a force hammer. After the signal measured by the acceleration sensor is output to the test equipment, the frequency and vibration mode of the current sectional ship model are obtained through software analysis; Step 6: Taking the initial node positions as a reference, simultaneously adjust the positions of the traveling gear assemblies (2) and the passive wheel sets (4) corresponding to a single initial node position, so that the traveling gear assemblies (2) and the passive wheel sets (4) of a single initial node position move simultaneously to the same side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat the operation in Step 5; Step 7: Compare the frequencies in Step 5 and Step 6; When the frequency in Step 5 is the smallest, the initial node position is the accurate node position; When the minimum frequency in Step 6 is less than the frequency in Step 5, take the node position where the minimum frequency appears in Step 6 as the initial node position and repeat Step 6 until the minimum frequency does not appear in the new node position, that is, the accurate node position is found; Step 8: Perform modal measurement of the sectional ship model with the accurate node position as the position of the suspension point. After the modal measurement of the sectional ship model is completed, lower the lifting beam (1) to make the sectional ship model land stably and complete the test.

2. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 1, characterized in that: The multiple initial node positions include the node positions of two nodes, three nodes, and four nodes.

3. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 1, characterized in that: The structure of the traveling gear assembly (2) is as follows: It includes a gear (21), and the gear (21) meshes with a rack (11) installed at the lower part of the hanging beam (1). The rack (11) is arranged along the length direction of the hanging beam (1). A through hole (12) is provided on the hanging beam (1), and the through hole (12) is an elongated hole. The length direction of the through hole (12) is the same as the length direction of the hanging beam (1); A pin shaft (22) drivingly connected to the gear (21) is installed in the middle of the gear (21). Both ends of the pin shaft (22) pass through the through hole (12) and are respectively located outside both sides of the hanging beam (1). First hanging rings (31) are respectively sleeved on both ends of the pin shaft (22). A first handle (23) is installed at one end of the pin shaft (22), and the first handle (23) is located outside the first hanging ring (31). The two first hanging rings (31) are connected to the upper end of the hanging rope (3).

4. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 3, characterized in that: The hanging beam (1) is of a rectangular tubular structure. The rack (11) is installed on the upper surface of the bottom of the hanging beam (1). Through holes (12) are respectively provided on the side walls of both sides of the hanging beam (1), and the two through holes (12) correspond to each other. The gear (21) is located between the side walls of both sides of the hanging beam (1), and both sides of the gear (21) are matched with the inner sides of the side walls of the hanging beam (1).

5. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 4, characterized in that: A scale line (13) is provided on the outer side of the side wall of the hanging beam (1) below the through hole (12).

6. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 3, characterized in that: The cross-section of the hanging beam (1) is of an I-shaped structure. The lower part of the hanging beam (1) is a bottom plate (14). A vertical plate (15) is vertically provided in the middle of the upper surface of the bottom plate (14). Racks (11) are respectively provided on the upper surfaces of the bottom plate (14) on both sides of the vertical plate (15). A gear (21) is installed on each rack (11). The pin shaft (22) is drivingly connected to the two gears (21) at the same time. The through hole (12) is located on the vertical plate (15). A limiting plate matched with the outer side of the gear (21) is provided on the bottom plate (14) outside the rack (11).

7. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 6, characterized in that: A scale line (13) is provided on the outer side of the rack (11).

8. The experimental method for modal measurement of an I-shaped measuring beam segmented ship model according to any one of claims 3-7, characterized in that: The number of the traveling gear assemblies (2) is five, which are distributed along the length direction of the suspension beam (1), and the through holes (12) in the two traveling gear assemblies (2) located on one side of the length direction of the suspension beam (1) are communicated with each other.

9. A test method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 1, characterized in that: The structure of the I-shaped measuring beam (5) is: including an upper wing plate (501) and a lower wing plate (503) that are parallel to each other. The middle parts of the upper wing plate (501) and the lower wing plate (503) in the width direction are connected by a web (502), and the web (502) is perpendicular to the upper wing plate (501); The structure of the passive wheel set (4) is: including two upper rollers (401) spaced apart on the upper surface of the upper wing plate (501) and lower rollers (403) respectively arranged on the lower surfaces of the upper wing plates (501) on both sides of the web (502). The upper rollers (401) and the lower rollers (403) are connected by a rectangular frame structure (402). The upper rollers (401) and the lower rollers (403) are rotatably connected to the rectangular frame structure (402). The lower part of the rectangular frame structure (402) is open, and the opening of the rectangular frame structure (402) corresponds to the web (502); A second lifting ring (32) is installed on the rectangular frame structure (402) outside the upper roller (401), and the second lifting ring (32) is connected to the lower end of the lifting rope (3).

10. A test method for modal measurement of an I-shaped measuring beam segmented ship model according to claim 9, characterized in that: A second hand crank (404) is installed outside the upper roller (401). The end of the second hand crank (404) is fixedly connected to the center of the upper roller (401). The rectangular frame structure (402) passes through the end of the second hand crank (404) and is rotatably connected to the second hand crank (404).

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