An experimental method for modal measurement of a segmented ship model with a tubular measuring beam

Abstract

An experimental method for modal measurement of a segmented ship model using a tubular measurement beam, comprising the steps of: First, prepare a segmented ship model; Second, mark the initial nodes on the tubular measurement beam; Third, set up parallel supports on the ground and slidably mount a steel arm on the upper surface of the supports; a bearing sleeve is provided in the middle of the steel arm; Fourth, insert the tubular measurement beam into the centers of multiple bearing sleeves, and the segmented ship model is in a suspended state; Fifth, move the steel arm to adjust the position of the suspension point to the initial node position; Sixth, obtain the frequency and vibration mode of the current ship model; Seventh, repeat step six after adjusting the initial node position to a new node position; Eighth, compare the frequencies in steps six and seven; and find the accurate node position; Ninth, perform modal measurement at the accurate node position of the suspension point. It is convenient to change the position of the suspension point during the process of finding the nodes, safe and convenient, time-saving and labor-saving. At the same time, the position of the suspension point can cover the entire measurement beam, the position of the node is accurate, and the accuracy of modal measurement is improved.

Description

Technical Field

[0001] The invention relates to the technical field of segmented ship model testing, in particular to a test method for modal measurement of segmented ship models with a tubular measuring beam. Background Art

[0002] Modal testing of hull structures in air is a crucial step required prior to tank model testing of large ships and marine structures. It forms the basis for cross-sectional load testing and hydroelastic analysis. Since the mass and stiffness distribution of large ships undergo changes during scaled-down fabrication, vibration characteristics are crucial for successful fabrication and serve as crucial parameters for tank model testing. Furthermore, compared to testing modal parameters in water, dry modal testing is a crucial precursor to wet modal testing. If dry modal testing reveals discrepancies between the ship's structural parameters and those obtained before conversion, the cause must be identified immediately; otherwise, the accuracy of the tank test results cannot be verified.

[0003] Furthermore, large ships, due to their large size and low stiffness, are prone to wave-induced vibration. Dry structural vibration testing often requires consideration of the first four modes, and the location of the suspension points is a key factor affecting the measured results of each modal order. In this case, the conventional approach is to analyze the first four vibration modes based on numerical modeling, obtain the vibration nodes for each order, and then roughly measure the node locations before lifting the segmented ship model. The suspension points are then positioned at these nodes. Due to errors between the numerical calculations and the actual model, finding the correct nodes requires multiple attempts to change the suspension points to measure relevant parameters. Each change in the suspension point position causes changes in the tension of the ropes, which can alter the equilibrium state during lifting. This not only affects the normal modal test results but also poses a risk of capsizing during lifting. Furthermore, the repeated lifting and node changes required to switch the hoisting test modal method from two nodes to three and four nodes is time-consuming and labor-intensive.

[0004] At the same time, in existing lifting technology, since the measuring beam is assembled into a segmented ship model by welding with multiple fixed supports, once the welding position of the measuring beam and the fixed supports, as well as the location of the acceleration sensor, coincides with the location of the vibration node, it is inevitable that the lifting rope needs to be moved a distance. In this case, if a rigid rope is used, it will greatly change the natural frequency of the system, significantly affecting the modal measurement results. If an elastic rope is used, it is necessary to find an elastic rope with good elasticity and low rigidity. Although it will still change the frequency of the system, the impact is not significant. The trade-off is that the lifting process is more dangerous. This is because the elastic rope has a large elongation range, which requires a large lifting space on the one hand, and the ship model is prone to shaking on the other hand, which poses 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 a segmented ship model with a tubular measurement beam, so as to facilitate the replacement of the suspension point position during the process of finding the node, without the need to repeatedly lift the segmented ship model, nor the need for ropes for hoisting, which is safe, convenient, time-saving and labor-saving, improves work efficiency. At the same time, the position of the suspension point can cover the entire measurement beam, making the position of finding the node accurate and improving the accuracy of modal measurement.

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

[0007] A test method for modal measurement of a segmented ship model with a tubular measurement beam includes the following steps:

[0008] Step 1: Establish a segmented hull numerical model, and obtain the bending node positions 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. Inside the segmented hull, a plurality of frames are installed at intervals along the ship length direction. At the upper end of each frame, a fixed support is installed, and the upper end of the fixed support is simultaneously connected to a tubular measurement beam arranged along the ship length direction;

[0010] Step 2: According to the node position and scale ratio in Step 1, convert the node position of the segmented ship model and mark it on the tubular measurement beam as multiple initial node positions for testing;

[0011] Step 3: Intermittently set two parallel brackets on the ground, and slidably install both ends of the length direction of a plurality of steel arms for suspending the tubular measurement beam on the upper surfaces of the two brackets. The plurality of steel arms are parallel to each other, and the length direction of the bracket is perpendicular to the length direction of the steel arm;

[0012] In the middle of the length direction of each steel arm, a bearing sleeve matching the outer wall surface of the tubular measurement beam is installed, and the bearing sleeve corresponds to the initial node position; the bearing sleeve is used for hoisting the tubular measurement beam, and the contact position between the tubular measurement beam and the bearing sleeve is the position of the suspension point of the segmented ship model;

[0013] Paste acceleration sensors on the surface of the tubular measurement beam, and avoid the acceleration sensors, the connecting wires of the acceleration sensors and the fixed supports at the contact position between the tubular measurement beam and the bearing sleeve;

[0014] Step 4: Place the segmented ship model between the two brackets, insert one end of the tubular measurement beam into the centers of a plurality of bearing sleeves in sequence, and make the segmented ship model leave the ground and be in a suspended state;

[0015] Step 5: Move the steel arms to adjust the position of the bearing sleeve on the tubular measurement beam so that the bearing sleeve contacts the tubular measurement beam at the initial node position; at this time, the position of the suspension point is the initial node position;

[0016] Step 6: After the segmented ship model is stable, use a hammer to strike the tubular measuring beam. 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 7: Using the initial node position as a reference, adjust the bearing sleeve position corresponding to the initial node position at the same time, so that the bearing sleeve position of a single initial node position moves toward the side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat step 6;

[0018] Step 8: Compare the frequency in step 6 with the frequency in step 7;

[0019] When the frequency in step six is the minimum, the initial node position is the accurate node position;

[0020] When the minimum frequency in step 7 is less than the frequency in step 6, repeat step 7 with the node position where the minimum frequency appears in step 7 as the initial node position until the minimum frequency no longer appears at the new node position, and the accurate node position is found;

[0021] Step 9: Use the accurate node position as the location of the suspension point to perform segmented ship model modal measurement.

[0022] Its further technical solution is:

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

[0024] After the modal measurement of the segmented ship model in step nine is completed, add or reduce the steel arm installed in conjunction with the tubular measuring beam, repeat steps five to eight to perform modal measurement at another node position, and after completing the modal measurement of the segmented ship model at various node positions, remove the segmented ship model from the steel arm to complete the test.

[0025] The structure of the bearing sleeve is as follows: it includes a block-shaped body, a through hole matching the shape of the tubular measuring beam is provided in the middle of the block body, a notch corresponding to the fixed support is provided at the bottom of the through hole, and multiple bull's eye bearings are installed inside the through hole. The centers of the multiple bull's eye bearings are evenly distributed on the same cross-section of the through hole, and the large steel balls of the bull's eye bearings are in contact with the outer surface of the tubular measuring beam.

[0026] Rollers are installed at the lower part of both ends of each steel arm, and a guide rail is installed on the upper surface of the bracket. The guide rail is in sliding cooperation with the rollers.

[0027] Before adjusting the position of the bearing sleeve in Step 5, fixing parts are arranged on both sides of the tubular measuring beam in the length direction. A fixing piece is installed on the upper part of each steel arm. The fixing parts, multiple fixing pieces, and fixing parts are sequentially connected to each other. The fixing piece adjacent to the fixing part and the fixing part are connected by a rope. One group of adjacent fixing pieces are connected by a spring, and the remaining steel arms are connected by ropes.

[0028] The fixing part is a connecting rod, and both ends of the connecting rod are detachably connected to the same-side ends of two brackets.

[0029] The fixing part is a profile, the axis of the profile is vertically arranged, and a support is arranged at the lower end of the profile. The support is detachably installed on the ground.

[0030] A wire reel is rotatably installed at the upper end of the fixing piece. The wire reel is connected to one end of the rope on one side of the wire reel. A handle is installed on the wire reel, and a locking mechanism for fixing the length of the rope is further included.

[0031] A plurality of lifting mechanisms are installed at the lower part of each bracket.

[0032] The beneficial effects of the present invention are as follows:

[0033] The structure of the present invention is compact and reasonable, and the operation is convenient. By using the steel arm to hoist the circular tubular measuring beam, and at the same time the steel arm can move relative to the tubular measuring beam through the bearing sleeve, it is convenient to change the position of the suspension point during the process of finding the node. It is not necessary to repeatedly lift the segmented ship model, nor is it necessary to use rope materials for hoisting, which is safe, convenient, time-saving and labor-saving, and improves work efficiency; the contact position between the tubular measuring beam and the bearing sleeve avoids the acceleration sensor, the acceleration sensor connection 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 and improving the accuracy of modal measurement.

[0034] At the same time, the present invention also has the following advantages:

[0035] (1) Since the bearing sleeve on the steel arm is sleeved on the circular tubular measuring beam to lift the segmented ship model, and at the same time the lower part of the steel arm is slidably connected to the upper surface of the bracket, it is not only convenient for the steel arm to move the position, but also convenient to remove or sleeve a single steel arm from one end of the tubular measuring beam to facilitate switching the hoisting test mode, so that it can adapt to modal tests such as the second-order mode, the third-order mode, and the fourth-order mode. The operation is convenient and it is not necessary to repeatedly lift the segmented ship model.

[0036] (2) The centers of the bull's-eye bearings arranged inside the bearing sleeve are evenly distributed on the same cross-section, and the circular tubular measuring beam is supported in a multi-point contact manner. The multiple contact points are located on the circumferential line of the node position of the circular tubular measuring beam, and the determination of the node position is guaranteed in terms of accuracy.

[0037] (3) By arranging fixing parts on both sides of the tubular measuring beam in the length direction, and using multiple ropes and a spring for tensioning the ropes to connect the fixing parts, the steel arms, and the fixing parts in sequence, it is convenient for the position movement and fixation of the steel arms relative to the tubular measuring beam, making the adjustment of the node position more convenient.

[0038] (4) By setting up a lifting mechanism to move the steel arms when the segmented ship is stationary, the tubular measuring beam of the ship model can be inserted into multiple bearing sleeves, with convenient operation and precise movement. Description of the Drawings

[0039] Figure 1 Structural schematic diagram of the present invention (two steel arms and the fixing parts are connecting rods).

[0040] Figure 2 is Figure 1 Enlarged view at F in

[0041] Figure 3 is Figure 1 Top view of

[0042] Figure 4 is Figure 3 Enlarged view at G in

[0043] Figure 5 Structural schematic diagram of the present invention (two steel arms and the fixing parts are profiles).

[0044] Figure 6 is Figure 5 Top view of

[0045] Figure 7 Side view of the present invention.

[0046] Figure 8 Structural schematic diagram of the present invention (three steel arms and the fixing parts are connecting rods).

[0047] Figure 9 Side view of the present invention (including the lifting mechanism).

[0048] Figure 10 Structural schematic diagram of the present invention (including the lifting mechanism).

[0049] Figure 11 Structural schematic diagram of the segmented ship model of the present invention.

[0050] Wherein: 1, steel arm; 11, roller; 12, bearing sleeve; 1201, block-shaped body; 1202, bull's-eye bearing; 13, fixing piece; 2, bracket; 21, guide rail; 2201, connecting rod; 2202, profile; 23, lifting mechanism; 3, tubular measuring beam; 4, fixed support; 5, segmented ship hull; 6, rope; 7, spring; 8, wire reel. Detailed implementation manners

[0051] The following combines the accompanying drawings to illustrate the detailed implementation manners of the present invention.

[0052] As Figures 1 - 11 shown, the test method for modal measurement of a segmented ship model with a tubular measurement beam in the first embodiment includes the following steps:

[0053] Step 1: Establish a segmented hull numerical model, and obtain the bending node positions of each order of the segmented hull through modal calculation;

[0054] 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 5. Inside the segmented hull 5, a plurality of frames are installed at intervals along the ship length direction. At the upper end of each frame, a fixed support 4 is installed. The upper end of the fixed support 4 is simultaneously connected to a tubular measurement beam 3 arranged along the ship length direction; the cross-section of the tubular measurement beam 3 is circular or rectangular, the tubular measurement beam 3 is continuously penetrated front and back, and the fixed support 4 is generally welded to the tubular measurement beam 3.

[0055] Step 2: According to the node positions and scale ratio in Step 1, convert the node positions of the segmented ship model and mark them on the tubular measurement beam 3 as multiple initial node positions for testing.

[0056] Step 3: Intermittently set two parallel brackets 2 on the ground. Slide the two ends of the length direction of a plurality of steel arms 1 used for suspending the tubular measurement beam 3 onto the upper surfaces of the two brackets 2 respectively. The plurality of steel arms 1 are parallel to each other, and the length direction of the bracket 2 is perpendicular to the length direction of the steel arm 1;

[0057] The bracket 2 is made of concrete casting. Steel fixed ends are provided at both ends of the bracket 2, which has a limiting function to prevent the outer steel arm 1 from detaching.

[0058] In the middle of the length direction of each steel arm 1, a bearing sleeve 12 matching the outer wall surface of the tubular measurement beam 3 is installed. The bearing sleeve 12 corresponds to the initial node position; the bearing sleeve 12 is used to hoist the tubular measurement beam 3, and the contact position between the tubular measurement beam 3 and the bearing sleeve 12 is the position of the suspension point of the segmented ship model;

[0059] Acceleration sensors are pasted on the surface of the tubular measurement beam 3. The contact position between the tubular measurement beam 3 and the bearing sleeve 12 avoids the acceleration sensors, the acceleration sensor connection wires and the fixed support 4;

[0060] The acceleration sensors are used to measure the acceleration of each section of the segmented ship model to obtain the vibration dry mode of the segmented ship model.

[0061] Step 4: Place the segmented ship model between two supports 2. Insert one end of the tubular measuring beam 3 into the centers of multiple bearing sleeves 12 in sequence, so that the segmented ship model is lifted off the ground and in a suspended state.

[0062] Step 5: Move the steel arm 1 to adjust the position of the bearing sleeve 12 on the tubular measuring beam 3 so that the bearing sleeve 12 contacts the tubular measuring beam 3 at the initial node position; at this time, the position of the suspension point is the initial node position.

[0063] Step 6: After the segmented ship model is stable, strike the tubular measuring beam 3 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 segmented ship model are obtained through software analysis.

[0064] Step 7: Taking the initial node position as a reference, simultaneously adjust the position of the bearing sleeve 12 corresponding to this initial node position, so that the position of the bearing sleeve 12 at a single initial node position moves towards one side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat Step 6.

[0065] 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, the position of each new node can be on both sides of the initial node position respectively, obtaining various combined position conditions, and measuring the frequency and vibration mode of the segmented ship model under the corresponding position conditions respectively, to find the position of the suspension point where the minimum frequency appears.

[0066] Step 8: Compare the frequencies in Step 6 and Step 7.

[0067] If the frequency in Step 6 is the minimum, then the initial node position is the accurate node position.

[0068] If the minimum frequency in Step 7 is less than the frequency in Step 6, take the node position where the minimum frequency appears in Step 7 as the initial node position and repeat Step 7 until the minimum frequency no longer appears at the new node position, then find the accurate node position.

[0069] Step 9: Conduct modal measurement of the segmented ship model with the accurate node position as the position of the suspension point.

[0070] As Figure 11 shown, multiple initial node positions include the node positions of two nodes, three nodes, and four nodes. When measuring the second-order mode, the initial node positions are at B and D corresponding to the two nodes; 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 nodes. Of course, for the convenience of subsequent measurement, all the above nodes can be marked on the tubular measuring beam 3 at one time.

[0071] By using a steel arm 1 to lift the tubular measuring beam 3, and at the same time the steel arm 1 can move relative to the tubular measuring beam 3 through the bearing sleeve 12, it is convenient to change the position of the suspension point in the process of finding the node, without the need to repeatedly lift the segmented ship model, and without the need for ropes for lifting. This is safe and convenient, saves time and effort, and improves work efficiency; the contact position between the tubular measuring beam 3 and the bearing sleeve 12 avoids the acceleration sensor, the acceleration sensor connecting line and the fixed support 4, so that the position of the suspension point can cover the entire measuring beam, so that the position of the node can be accurately found, and the accuracy of the modal measurement is improved.

[0072] This method completely eliminates the constraints of ropes and employs a precise method for finding node locations. Theoretically, this method is certain to locate vibration nodes. As long as the bearing sleeve 12 is securely installed at the vibration node location, the modal measurement results are highly accurate. Furthermore, when replacing a node, simply move the steel arm 1, which does not affect the start and end states of the model, making it convenient and quick.

[0073] like Figures 1 - 11 As shown, the test method for modal measurement of a segmented ship model with a tubular measuring beam of Example 2, wherein steps 1 to 9 are the same as those of Example 1;

[0074] After the modal measurement of the segmented ship model in step nine is completed, add or reduce the steel arm 1 installed in conjunction with the tubular measuring beam 3, repeat steps five to eight to perform modal measurement at another node position, and after completing the modal measurement of the segmented ship model at various node positions, remove the segmented ship model from the steel arm 1 to complete the test.

[0075] Since the bearing sleeve 12 on the steel arm 1 is mounted on the tubular measuring beam 3 to lift the segmented ship model, and the lower part of the steel arm 1 is slidably connected to the upper surface of the bracket 2, it is not only convenient to move the steel arm 1, but also convenient to remove the separate steel arm 1 from one end of the tubular measuring beam 3 or to mount it, which is convenient for switching the lifting test mode, making it suitable for modal tests such as second-order mode, third-order mode, and fourth-order mode. It is easy to operate and there is no need to repeatedly lift the segmented ship model.

[0076] like Figure 7 、 Figure 9 As shown, in the first and second embodiments, the matching structure of the bearing sleeve 12 and the tubular measuring beam 3 is as follows:

[0077] The structure of the bearing sleeve 12 is as follows: it includes a block body 1201, a through hole matching the shape of the tubular measuring beam 3 is provided in the middle of the block body 1201, a notch corresponding to the fixed support 4 is provided at the bottom of the through hole, and multiple bull's eye bearings 1202 are installed inside the through hole. The centers of the multiple bull's eye bearings 1202 are evenly distributed on the same cross-section of the through hole, and the large steel balls of the bull's eye bearings 1202 are in contact with the outer surface of the tubular measuring beam 3.

[0078] The centers of the bull's-eye bearings 1202 provided inside the bearing sleeve 12 are evenly distributed on the same cross-section, and the circular tubular measuring beam 3 is supported in a multi-point contact manner. The multiple contact points are located on the circumferential line at the node positions of the circular tubular measuring beam 3, and the determination of the node positions is guaranteed in terms of accuracy. For the traditional suspension rope method, since the suspension rope itself has a certain width and has a surface contact with the circular tubular measuring beam 3, it has a certain impact on the measurement accuracy.

[0079] As Figures 1 - 11 shown, in the first embodiment and the second embodiment, the mating structure between the steel arm 1 and the bracket 2 is as follows:

[0080] At the lower parts of both ends of each steel arm 1, rollers 11 are installed, and on the upper surface of the bracket 2, a guide rail 21 is installed. The guide rail 21 is in sliding fit with the rollers 11.

[0081] As Figures 1 - 10 shown, for the test method of modal measurement of the segmented ship model of the tubular measuring beam in the third embodiment, steps one to nine are the same as those in the first embodiment;

[0082] Before adjusting the position of the bearing sleeve 12 in step five, fixing parts are provided on both sides in the length direction of the tubular measuring beam 3. A fixing member 13 is installed on the upper part of each steel arm 1. The fixing parts, the multiple fixing members 13, and the fixing parts are connected to each other in sequence. The fixing member 13 adjacent to the fixing part and the fixing part are connected by a rope 6. Between one group of adjacent fixing members 13, they are connected by a spring 7, and the remaining steel arms 1 are connected by a rope 6.

[0083] As Figure 11 shown, the number of steel arms 1 corresponds to the number of initial nodes. When measuring the second-order mode, the number of steel arms 1 is two, corresponding to positions B and D; when measuring the third-order mode, the number of steel arms 1 is three, corresponding to the positions between B and D, C, and between C and D; when measuring the fourth-order mode, the number of steel arms 1 is four, corresponding to positions A, B, D, and E.

[0084] When the number of steel arms 1 is two, the two steel arms 1 are connected by a spring 7, and the two steel arms 1 are respectively connected to the fixing part by a rope 6. By adjusting the lengths of the two ropes 6, the contact position of the bearing sleeve 12 on the steel arm 1 and the tubular measuring beam 3 is moved, and thus moved to a new node position.

[0085] When the number of steel arms 1 is greater than two, the fixing member 13 adjacent to the fixing part and the fixing part are connected by a rope 6. Between one group of adjacent fixing members 13, they are connected by a spring 7, and the number of spaces between the remaining steel arms 1 is greater than or equal to one. The remaining steel arms 1 are connected by a rope 6. By adjusting the lengths of multiple ropes 6, the contact position of the bearing sleeve 12 on the steel arm 1 and the tubular measuring beam 3 is moved, and thus moved to a new node position.

[0086] By arranging fixing parts on both sides in the length direction of the tubular measuring beam 3, and using multiple ropes 6 and a spring 7 for tensioning the ropes 6 to connect the fixing parts, the steel arms 1, and the fixing parts in sequence, it is convenient for the position movement and fixation of the steel arms 1 relative to the tubular measuring beam 3, making the adjustment of the node position more convenient.

[0087] As Figures 1 - 3 shown, the fixing part is a connecting rod 2201, and both ends of the connecting rod 2201 are detachably connected to the same-side ends of two brackets 2.

[0088] As Figures 5 - 6 shown, the fixing part is a profile 2202, the axis of the profile 2202 is vertically arranged, a support is arranged at the lower end of the profile 2202, and the support is detachably installed on the ground; the profile 2202 can be an I-beam, an H-beam, etc.

[0089] A wire reel 8 is rotatably installed at the upper end of the fixing member 13. One end of a rope 6 on one side of the wire reel 8 is connected to the wire reel 8. A handle is installed on the wire reel 8, and a locking mechanism for fixing the length of the rope 6 is further included. The locking mechanism can fix the position of the handle through a rope, or a buckle installed on the wire reel 8 can lock the relative position of the wire reel 8 and the fixing member 13. By shaking the handle, the wire reel 8 is driven to rotate, and the rope 6 is wound around or loosened from the wire reel 8 to adjust the relative distance between adjacent steel arms 1.

[0090] When the above fixing parts are disassembled, the segmented ship model can be placed between the two brackets 2 from this side.

[0091] As Figures 1 - 10 shown, the test method for modal measurement of the tubular measuring beam segmented ship model in the fourth embodiment

[0092] A plurality of lifting mechanisms 23 are installed at the lower part of each bracket 2. The lifting mechanism 23 can be a jack or a scissor lift.

[0093] Therefore, in step four, the segmented ship model is placed on the bottom surface between the two brackets 2, and the segmented ship model is located inside the space between the brackets 2. By adjusting the lifting mechanism 23, the height of the steel arm 1 on the bracket 2 is made to correspond to the tubular measuring beam 3. The steel arm 1 slides on the bracket 2 towards the tubular measuring beam 3, and the tubular measuring beam 3 and a plurality of bearing sleeves 12 can be installed together. Then, the lifting mechanism 23 is started to raise the bracket 2, so that the segmented ship model leaves the ground and is in a suspended state.

[0094] By setting the lifting mechanism 23, when the segmented ship is static, the steel arm 1 can be moved, so that the tubular measuring beam 3 of the ship model can be inserted into a plurality of bearing sleeves 12, which is convenient for operation and has accurate movement.

[0095] If the lifting mechanism 23 is not installed in the lower part, auxiliary tools such as a crane or a trolley can be used to move the sectional ship model so that one end of the tubular measuring beam 3 is inserted into the centers of a plurality of bearing sleeves 12 in sequence.

[0096] The above description is an explanation of the present invention, not a limitation of the invention. The scope defined by the present invention can be seen in 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 segmented ship model with a tubular measuring beam, characterized in that: It includes the following steps: Step 1: Establish a segmented hull numerical model, and obtain the bending node positions of each order of the segmented hull through modal calculation; 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 (5). Inside the segmented hull (5), a plurality of frames are installed at intervals along the ship length direction. At the upper end of each frame, a fixed support (4) is installed. The upper ends of the fixed supports (4) are simultaneously connected to a tubular measuring beam (3) arranged along the ship length direction; Step 2: According to the node positions and scale ratio in Step 1, convert the node positions of the segmented ship model and mark them on the tubular measuring beam (3) as multiple initial node positions for testing; Step 3: Set two parallel brackets (2) at intervals on the ground. Slide the two ends of the length direction of a plurality of steel arms (1) for suspending the tubular measuring beam (3) on the upper surfaces of the two brackets (2) respectively. The plurality of steel arms (1) are parallel to each other. The length direction of the brackets (2) is perpendicular to the length direction of the steel arms (1); In the middle of the length direction of each steel arm (1), a bearing sleeve (12) matching the outer wall surface of the tubular measuring beam (3) is installed. The bearing sleeve (12) corresponds to the initial node position; the bearing sleeve (12) is used to hoist the tubular measuring beam (3), and the contact position between the tubular measuring beam (3) and the bearing sleeve (12) is the position of the suspension point of the segmented ship model; Paste acceleration sensors on the surface of the tubular measuring beam (3). The contact position between the tubular measuring beam (3) and the bearing sleeve (12) avoids the acceleration sensors, the acceleration sensor connection wires, and the fixed support (4); Step 4: Place the segmented ship model between the two brackets (2). Insert one end of the tubular measuring beam (3) into the centers of a plurality of bearing sleeves (12) in sequence, and make the segmented ship model leave the ground and be in a suspended state; Step 5: Move the steel arms (1) to adjust the positions of the bearing sleeves (12) on the tubular measuring beam (3) so that the bearing sleeves (12) contact the tubular measuring beam (3) at the initial node positions; at this time, the position of the suspension point is the initial node position; Step 6: After the segmented ship model is stable, strike the tubular measuring beam (3) with a force hammer. After the signals measured by the acceleration sensors are output to the test equipment, the frequency and vibration mode of the current segmented ship model are obtained through software analysis; Step 7: Based on the initial node positions, simultaneously adjust the positions of the bearing sleeves (12) corresponding to the initial node positions, so that the positions of the bearing sleeves (12) at a single initial node position move towards one side of the initial node position. After adjusting each initial node position to the corresponding new node position, repeat Step 6; Step 8: Compare the frequencies in Step 6 and the frequencies in Step 7; When the frequency in Step 6 is the smallest, the initial node position is the accurate node position; When the minimum frequency in Step 7 is less than the frequency in Step 6, use the node position where the minimum frequency appears in Step 7 as the initial node position and repeat Step 7 until the minimum frequency does not appear at the new node position, and then find the accurate node position; Step 9: Perform modal measurement of the segmented ship model with the accurate node position as the position of the suspension point.

2. The test method for modal measurement of a segmented ship model with a tubular measuring beam according to claim 1, characterized in that: The multiple initial node positions include node positions of two nodes, three nodes, and four nodes.

3. The test method for modal measurement of a segmented ship model with a tubular measuring beam as described in claim 1, characterized in that: After the modal measurement of the segmented ship model in step nine is completed, the steel arm (1) installed in conjunction with the tubular measuring beam (3) is increased or decreased, and steps five to eight are repeated to perform modal measurement at another node position. After the modal measurement of the segmented ship model at various node positions is completed, the segmented ship model is removed from the steel arm (1) to complete the test.

4. The test method for modal measurement of a segmented ship model with a tubular measurement beam as described in claim 1, characterized in that: The structure of the bearing sleeve (12) is as follows: it includes a block-shaped body (1201); a through hole matching the outer shape of the tubular measuring beam (3) is provided in the middle of the block-shaped body (1201); a notch corresponding to the fixed support (4) is provided at the bottom of the through hole; a plurality of bull's eye bearings (1202) are installed inside the through hole; the centers of the plurality of bull's eye bearings (1202) are evenly distributed on the same cross section of the through hole; and the large steel balls of the bull's eye bearings (1202) are in contact with the outer surface of the tubular measuring beam (3).

5. The test method for modal measurement of a segmented ship model with a tubular measurement beam according to claim 1, characterized in that: Rollers (11) are installed at the lower parts of both ends of each steel arm (1), and guide rails (21) are installed on the upper surface of the bracket (2), and the guide rails (21) are slidably matched with the rollers (11).

6. The test method for modal measurement of a segmented ship model with a tubular measuring beam according to claim 1, characterized in that: Before adjusting the position of the bearing sleeve (12) in step five, fixed parts are set on both sides of the length direction of the tubular measuring beam (3), and a fixing piece (13) is installed on the upper part of each steel arm (1). The fixed part, multiple fixing pieces (13), and the fixed part are connected to each other in sequence, and the adjacent fixing pieces (13) of the fixed part are connected to the fixed part by a rope (6). A group of adjacent fixing pieces (13) are connected by a spring (7), and the remaining steel arms (1) are connected by a rope (6).

7. The experimental method for modal measurement of a segmented ship model with a tubular measuring beam as described in claim 6, characterized in that: The fixing portion is a connecting rod (2201), and both ends of the connecting rod (2201) are detachably connected to the ends of the same side of the two brackets (2).

8. The test method for modal measurement of a segmented ship model with a tubular measuring beam as described in claim 6, characterized in that: The fixing part is a profile (2202), the axis of the profile (2202) is vertically arranged, and a support is arranged at the lower end of the profile (2202), and the support is detachably installed on the ground.

9. The experimental method for modal measurement of a segmented ship model with a tubular measuring beam according to claim 6, characterized in that: A winding wheel (8) is rotatably mounted on the upper end of the fixing member (13), and the winding wheel (8) is connected to one end of a rope (6) on one side of the winding wheel (8). The winding wheel (8) is provided with a handle and also includes a locking mechanism for fixing the length of the rope (6).

10. The experimental method for modal measurement of a segmented ship model with a tubular measuring beam according to claim 1, characterized in that: A plurality of lifting mechanisms (23) are installed at the lower part of each bracket (2).

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