A design method for low-noise hull plate frame based on bandgap theory

Abstract

The present invention relates to a method for designing a low-noise hull plate frame based on bandgap theory, comprising the following steps: determining characteristic information of an excitation source; carrying out low-noise plate frame structure design; optimizing the plate frame structure with non-periodic characteristics; verifying the design of the optimization scheme; and checking the structural strength. This technical scheme, starting from the perspective of ship plate frame structure design, takes vibration control as the design purpose on the basis of ensuring structural strength, and carries out vibration reduction design in a targeted manner based on the frequency spectrum characteristics of equipment excitation. This method does not significantly increase the empty ship weight and does not occupy cabin space resources. The design scheme is relatively flexible and has a good vibration damping effect, effectively avoiding the disadvantages of traditional means and meeting the current needs of ship vibration reduction design.

Description

Technical Field

[0001] The present invention relates to the technical field of ship structure design, and in particular to a design method for a low-noise ship hull plate frame based on bandgap theory. Background Art

[0002] Controlling hull mechanical vibration and noise has always been a key aspect of ship design. Military vessels are concerned about their impact on acoustic stealth, while civilian vessels also place higher demands on crew comfort. Improving vibration and noise reduction performance is a daunting challenge for modern ship structural design. In actual shipboard environments, hull mechanical vibration and noise are primarily transmitted through structural panels. Current equipment vibration isolation technology and damping material applications have reached a bottleneck and consume significant shipboard resources, necessitating the urgent need for new vibration and noise reduction methods.

[0003] Existing ship structure design specifications and guidelines generally only consider strength, stiffness, and stability requirements, lacking specific structural design methods and experience for vibration and noise reduction. Commonly used vibration and noise reduction methods for ship equipment include vibration isolation, damping, and increasing vibration damping mass. These methods fail to utilize the inherent bandgap characteristics of the plate frame structure, and the use of other vibration isolation devices and damping materials is expensive and has certain limitations.

[0004] Ship vibration isolation technologies primarily fall into three categories: passive, active, and hybrid. In practical applications, single-layer and double-layer isolation have evolved. These vibration reduction methods generally dissipate vibration energy along the vibration transmission path through isolators and intermediate masses. However, the use of these additional devices inevitably increases the light ship weight and requires additional cabin space.

[0005] Laying damping materials on the surface of the hull structure is one of the common measures for vibration reduction. Damping materials are generally expensive, and the main effect of damping is to reduce the peak value of the mid- and high-frequency response. The advantage of vibration reduction in the low-frequency area is not obvious. However, ship equipment whose main working frequency band is in the mid- and low-frequency range is relatively common. In this case, the cost-effectiveness of using damping materials is low.

[0006] The form of an anti-vibration mass in plate-type components is similar to that of conventional stiffeners or ribs, but their mechanisms of action differ. The presence of ribs acts as a linear excitation continuously distributed along the plate, thus affecting the field distribution of the original structure. The anti-vibration mass, on the other hand, is a large, heavy object, typically with a rectangular, square, or cylindrical cross-section. In a base structure, the anti-vibration mass is primarily located at the base and can be deployed on either side. However, its use also increases structural weight and consumes cabin space.

[0007] The basic principle of vibration band gap in periodic structures is to hinder the propagation of elastic waves in the structure. After years of research and development, many scholars have used a variety of research methods such as theory, experiment and numerical simulation to conduct in-depth exploration of the characteristics of vibration band gap in periodic structures, laying a solid foundation for the application of vibration band gap in periodic structures. Figure 1 represents the propagation characteristics of waves in a periodic structure, Figure 1 At a frequency of 156Hz, within the passband, elastic waves propagate unimpeded. However, at a frequency of 240Hz, within the bandgap, elastic wave transmission is hindered and rapidly attenuates. As a fundamental component of the hull structure, the dynamic characteristics of the plate frame structure largely determine the overall structural vibration response. Despite the increasing sophistication of vibration isolation technology, the structure's inherent vibration-damping capabilities remain unrealized. As a fundamental component of the hull structure, the periodic plate frame structure is the essential path for elastic wave propagation within the hull structure. Therefore, studying the vibration bandgap characteristics of the periodic plate frame structure is crucial for achieving vibration control of the periodic plate frame structure.

[0008] Therefore, a plate frame design method is currently needed to combine the hull plate frame with the basic theory of vibration band gap of periodic structures, providing new research ideas for vibration and noise reduction of hull structures. Summary of the Invention

[0009] The main design idea of ​​the existing technology is to use supplementary vibration isolation measures other than ship structure design. This method requires the use of other devices or materials besides the hull structure, which occupies a certain amount of cabin space resources and increases the weight of the entire ship. To address the above problems, a low-noise hull plate frame design method based on bandgap theory is proposed.

[0010] The technical solution of the present invention is: a method for designing a low-noise hull plate frame based on bandgap theory, comprising the following steps:

[0011] S1. Determine the characteristic information of the excitation source;

[0012] S2. Carry out low-noise panel frame structure design;

[0013] S3. Optimal design of plate-frame structure with non-periodic characteristics;

[0014] S4. Verify the optimization scheme design;

[0015] S5. Structural strength verification.

[0016] Furthermore, the step S1 specifically includes: determining the frequency and response size of the excitation source under each working condition based on equipment data.

[0017] Furthermore, the step S1 specifically includes: obtaining device excitation information according to bench test measurements.

[0018] Furthermore, step S2 is specifically as follows: according to the excitation source information input in step S1, the structural noise optimization target is clarified, the structural design is carried out for the vibration line spectrum peak of the selected frequency, the key design parameters of the periodic plate frame are determined, the corresponding frequency of the line spectrum is matched with the plate frame vibration band gap frequency range, so that the target frequency is within the band gap frequency range, the plate frame vibration transmission is reduced, and the underwater radiation noise is reduced, thereby obtaining the improved plate frame model and the original plate frame model.

[0019] Furthermore, the improved frame model has a quality comparable to that of the original frame model.

[0020] Furthermore, step S3 is specifically as follows: according to step 2, an optimized periodic plate frame structure can be obtained. If undesirable periodic characteristics appear in the actual ship layout, it is necessary to optimize the periodic plate frame obtained in step 2 according to the requirements of equipment layout, etc., and change the non-periodic unit structure parameters to improve the periodic defect characteristics in the plate frame model and obtain a low-noise plate frame structure with non-periodic characteristics.

[0021] Furthermore, the calculation inputs such as the equipment, excitation, and boundary of the plate frame structure with non-periodic characteristics are consistent with the improved plate frame structure model in steps S1 to S2 above.

[0022] Furthermore, step S4 is specifically as follows: by comparing and analyzing the low-noise improved panel frame model and the improved panel frame model with non-periodic characteristics obtained in step S2 or step S3 with the original panel frame model obtained in the general design scheme, the vibration responses of the two under the same excitation, boundary and other conditions are calculated to verify the feasibility and effectiveness of the panel frame optimization scheme.

[0023] Furthermore, in the structural strength check of step S5, the hull structure must meet both overall strength and local strength requirements.

[0024] Furthermore, in the structural strength check of step S5, if the strength requirements are not met, steps S2 to S5 need to be repeated, and the low-noise panel frame structural parameters can be further optimized according to the calculation results to obtain an optimized panel frame structure.

[0025] The beneficial effects of the present invention are as follows: the present invention provides a low-noise hull plate frame design method based on the bandgap theory. This technical solution starts from the perspective of ship plate frame structure design, takes vibration control as the design purpose on the basis of ensuring structural strength, and carries out vibration reduction design in a targeted manner according to the spectral characteristics of equipment excitation. It will not significantly increase the empty ship weight, nor will it occupy the space resources of the cabin. The design scheme is relatively flexible and has a good vibration damping effect, effectively avoiding the disadvantages of traditional means and meeting the current needs of ship vibration reduction design. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A comparison diagram of vibration transmission inside and outside the bandgap frequency range of the structure;

[0027] Figure 2 This is a flow chart of the method for designing a low-noise hull plate frame based on the bandgap theory of the present invention;

[0028] Figure 3 Schematic diagram of the original plate frame model structure in an embodiment of the present invention;

[0029] Figure 4 This is a graph showing the average acceleration level of the nodes of the outer plate of the original plate frame model in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the improved plate rack model structure in an embodiment of the present invention;

[0031] Figure 6 This is a graph showing average acceleration levels of nodes of outer plates of the improved plate frame model in an embodiment of the present invention;

[0032] Figure 7 Schematic diagram of the structure of an improved plate frame model with non-periodic characteristics in an embodiment of the present invention;

[0033] Figure 8 This is a graph showing average acceleration levels of nodes of outer plates of an improved plate frame model with non-periodic characteristics according to an embodiment of the present invention;

[0034] Figure 9 : These are comparison diagrams of the vibration responses of the plate frame model in an embodiment of the present invention, where (a) is the vibration response cloud diagram of the original plate frame model when f = 59 Hz; (b) is the vibration response cloud diagram of the improved plate frame model when f = 59 Hz; and (c) is the vibration response cloud diagram of the improved plate frame model with non-periodic characteristics when f = 59 Hz. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] refer to Figure 2 As shown, the present invention provides a method for designing a low-noise hull plate frame based on bandgap theory, comprising:

[0037] Step 1: Determine the characteristic information of the excitation source:

[0038] Based on the equipment data, the frequency and response size of the excitation source under each working condition can be clarified, and the equipment excitation information can also be obtained based on bench test measurements.

[0039] Step 2: Design low-noise panel structure:

[0040] Based on the excitation source information input in step 1, the structural noise optimization target is clarified, the structural design is carried out based on the vibration line spectrum peak of the selected frequency, the key design parameters of the periodic plate frame are determined, and the corresponding frequency of the line spectrum is matched with the plate frame vibration band gap frequency range. The target frequency is placed within the band gap frequency range, the plate frame vibration transmission is reduced, and the underwater radiation noise is reduced, thereby obtaining an improved plate frame model and the original plate frame model.

[0041] In this example, reference Figure 3 、 4 As shown, by calculating Figure 3 The original simplified model in the figure can obtain the average acceleration level frequency response curve of the outer plate node of the bottom plate frame structure as shown in the figure. Figure 4 As shown in the figure, the original plate frame model includes loads, boundary conditions, equipment information, and vibration isolation parameter inputs. The calculation results show that when the frequency is 59 Hz, the structure has a large response.

[0042] refer to Figure 5 、 6 As shown in the figure, the key design parameters of the vibration band gap of the periodic plate frame structure can be obtained through the existing numerical method. In order to improve the structural vibration corresponding to the frequency of 59 Hz, the parameter design can be obtained. Figure 5 The improved plate frame structure shown, the improved plate frame model and the original plate frame model have the same quality;

[0043] After calculation, we can get Figure 6 Comparing the frequency response curves shown in the figure, it can be found that the response peak of the original panel frame is reduced at the target frequency of 59Hz. At the same time, in the frequency range of 0-200Hz, the total acceleration level of the outer plate of the panel frame structure is also reduced to a certain extent.

[0044] Step 3: Optimization design of the plate frame structure with non-periodic characteristics:

[0045] According to step 2, an optimized periodic plate frame structure can be obtained. If undesirable periodic characteristics appear in the actual ship layout, the periodic plate frame obtained in step 2 needs to be optimized according to the requirements of equipment layout, etc., and the non-periodic unit structure parameters are changed to improve the periodic defect characteristics in the plate frame model and obtain a low-noise plate frame structure with non-periodic characteristics.

[0046] In actual ships, there is often no ideal periodic plate frame structure, so reference Figure 7 As shown in Figure 2, it is necessary to carry out non-periodic plate frame structure design under certain restrictions. Figure 5 The position of a longitudinal profile in the optimized rack model shown needs to be re-determined according to the equipment installation requirements. Figure 7The plate frame structure shown has non-periodic characteristics, and the calculation inputs such as equipment, excitation, and boundary in the plate frame structure are consistent with the improved plate frame structure model in steps S1 to S2.

[0047] Step 4: Verify the optimization design:

[0048] By comparing and analyzing the low-noise improved panel frame model obtained in step 2 or step 3 and the improved panel frame model with non-periodic characteristics with the original panel frame model obtained by the general design scheme, the vibration responses of the two under the same excitation, boundary and other conditions are calculated to verify the feasibility and effectiveness of the panel frame optimization scheme.

[0049] refer to Figure 8 、 9 As shown, by comparing the original plate frame model, the improved plate frame model, and the improved plate frame model with non-periodic characteristics, we can get Figure 8 The results show that when the frequency is 59 Hz, the optimized low-noise frame still has a low vibration level; the mass, 59 Hz vibration acceleration level and 0-200 Hz total acceleration level of the three are shown in Table 1; when the frequency is 59 Hz, the vibration response cloud diagrams of the three models can be obtained as follows Figure 9 , its vibration distribution state has also changed.

[0050] Table 1 Comparison of plate frame model mass and vibration acceleration level

[0051]

[0052] Step 5, structural strength verification:

[0053] The periodic plate frame structure obtained through steps 1 through 4 must also meet basic strength requirements, so a strength check is performed based on the above scheme. In the hull structure, both overall and local strength requirements must be met. If these requirements are not met, steps 2 through 5 must be repeated. Based on the calculation results, the low-noise plate frame structure parameters can be further optimized to obtain an optimized plate frame structure.

[0054] The beneficial effects are: this technical solution starts from the perspective of ship frame structure design, takes vibration control as the design purpose on the basis of ensuring structural strength, and carries out vibration reduction design in a targeted manner according to the spectral characteristics of equipment excitation. It will not significantly increase the weight of the empty ship, nor will it occupy the space resources of the cabin. The design solution is relatively flexible and has a good vibration damping effect, effectively avoiding the disadvantages of traditional means and meeting the current needs of ship vibration reduction design.

[0055] It should be noted that the orientations or positional relationships indicated by the above-mentioned terms "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. The terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. "Multiple" means two or more. "Installation", "connected", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for designing a low-noise ship hull frame based on bandgap theory, characterized in that: The following steps are involved: S1. Determine the characteristic information of the excitation source; S2. Carry out low-noise panel frame structure design; Based on the excitation source information input in step S1, the structural noise optimization target is clarified, the structural design is carried out for the vibration line spectrum peak of the selected frequency, the key design parameters of the periodic plate frame are determined, the corresponding frequency of the line spectrum is matched with the plate frame vibration band gap frequency range, the target frequency is placed within the band gap frequency range, the plate frame vibration transmission is reduced, and the underwater radiation noise is reduced, thereby obtaining an improved plate frame model and an original plate frame model; S3. Optimal design of plate-frame structure with non-periodic characteristics; If undesirable periodic characteristics appear in the actual ship layout after the optimized periodic frame structure obtained in step S2, the periodic frame obtained in step S2 is optimized according to the equipment layout requirements, and the non-periodic unit structure parameters are changed to improve the periodic defect characteristics in the frame model and obtain a low-noise frame structure with non-periodic characteristics; S4. Verify the optimization scheme design; By comparing and analyzing the low-noise improved frame model and the improved frame model with non-periodic characteristics obtained in step S2 or step S3 with the original frame model, the vibration responses of the two under the same excitation and boundary conditions are calculated to verify the feasibility and effectiveness of the frame optimization scheme; S5. Structural strength verification.

2. The low-noise hull plate design method based on bandgap theory according to claim 1 is characterized in that: The step S1 specifically includes: determining the frequency and response size of the excitation source under various working conditions based on equipment data.

3. The low-noise ship hull plate design method based on bandgap theory according to claim 1 is characterized in that: The step S1 specifically includes: obtaining device excitation information according to bench test measurements.

4. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 1 is characterized in that: The improved plate frame model has the same quality as the original plate frame model.

5. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 1 is characterized in that: The equipment, excitation, and boundary calculation inputs in the plate frame structure with non-periodic characteristics are consistent with the improved plate frame structure model in steps S1 to S2.

6. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 1 is characterized in that: In the structural strength check of step S5, the hull structure must meet both overall strength and local strength requirements.

7. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 6 is characterized in that: In the structural strength check of step S5, if the strength requirements are not met, steps S2 to S5 need to be repeated, and the low-noise panel frame structural parameters are further optimized according to the calculation results to obtain an optimized panel frame structure.

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