Hull low-noise grillage design method based on band gap theory

Abstract

The invention relates to a ship body low-noise grillage design method based on a band gap theory. The method comprises the following steps that excitation source feature information is determined; carrying out low-noise grillage structure design; optimization design of a grillage structure with a non-periodic characteristic; verifying the optimization scheme design; checking the structural strength; according to the technical scheme, starting from the angle of ship grillage structural design, vibration control serves as the design purpose on the basis of guaranteeing the structural strength, vibration reduction design is carried out in a targeted mode according to the spectral characteristics of equipment excitation, the weight of an empty ship cannot be obviously increased, cabin space resources cannot be occupied, the design scheme is relatively flexible, and the design cost is low. And meanwhile, a good vibration stopping effect is achieved, the defects of traditional means are effectively overcome, and the requirements of current ship vibration reduction design are met.

Description

Technical Field

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

[0002] The control of mechanical vibration and noise of the hull has always been an important part of ship design. Military ships are concerned about its impact on acoustic stealth capabilities, and civilian ships also have higher requirements for the comfort of personnel working and living. Improving vibration and noise reduction performance is a difficult challenge for modern ship structure design. In the actual ship environment, the mechanical vibration and noise of the hull are mainly transmitted through the structural plate frame. The current equipment vibration isolation technology and damping material application have entered a bottleneck period and occupy a large amount of resources on the entire ship. Therefore, it is urgent to develop new vibration and noise reduction methods.

[0003] The existing ship structure design specifications or guidelines generally only consider the requirements of strength, stiffness and stability, and there is a relative lack of structural design methods and experience specifically for vibration and noise reduction. The commonly used vibration and noise reduction methods on ship equipment generally include vibration isolation, damping, and increasing vibration-damping mass. Such methods fail to utilize the band gap characteristics of the plate frame structure itself, and the use of other vibration isolation devices and vibration reduction materials is expensive and has certain limitations.

[0004] Ship vibration isolation technology mainly includes three types: passive vibration isolation, active vibration isolation and hybrid vibration isolation. In practical applications, single-layer vibration isolation and double-layer vibration isolation have gradually emerged. The general idea of ​​this type of vibration reduction method is to dissipate vibration energy through vibration isolators, intermediate masses, etc. on the vibration transmission path. Due to the use of other devices, the empty ship weight will inevitably increase and a larger cabin space will be required.

[0005] Laying damping material 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 mid- and high-frequency response. The advantage of vibration reduction in the low-frequency area is not obvious. However, it is common for ship equipment whose main working frequency band is in the mid- and low-frequency range. In this case, the cost-effectiveness of using damping materials is low.

[0006] The form of the vibration-damping mass structure is similar to the general ribbed or ribbed structure in plate-type components, but the working principles of the two are different. The existence of ribs or ribs is equivalent to applying a line excitation continuously distributed along the ribs on the plate, thereby affecting the field distribution of the original structure; while the vibration-damping mass is a large and heavy object, generally with a rectangular, square or cylindrical cross-section. The vibration-damping mass in the base structure is mainly distributed at the root of the base, and can be arranged on one side or on both sides. The use of vibration-damping mass also increases the weight of the structure and occupies cabin space resources.

[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 to conduct in-depth exploration of the characteristics of vibration band gaps in periodic structures, laying a solid foundation for the application of vibration band gaps in periodic structures. Figure 1 represents the propagation characteristics of waves in a periodic structure, Figure 1 When the frequency is 156Hz, it is in the passband, and the elastic wave will be transmitted forward without hindrance. When the frequency is 240Hz, it is in the band gap range, and the transmission of the elastic wave will be hindered and quickly attenuated. As a basic component of the hull structure, the dynamic characteristics of the plate frame structure largely determine the vibration response of the overall structure. Today, with the increasingly mature vibration isolation technology, the vibration-proofing ability of the structure itself has not been brought into play. As a basic component of the hull structure, the periodic plate frame structure is the only way for the propagation of elastic waves in the hull structure. Therefore, studying the vibration band gap characteristics of the hull periodic plate frame structure is an important guarantee for realizing the vibration control of the hull 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 periodic structural vibration band gap, so as to provide a new research idea for vibration and noise reduction of hull structure. Summary of the invention

[0009] The main design idea of ​​the existing technology is to take supplementary vibration isolation measures other than the ship structure design. This type of approach requires the use of other devices or materials besides the hull structure, occupies a certain amount of cabin space resources and increases the weight of the entire ship. To address the above problems, a hull low-noise 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 according to the equipment data.

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

[0018] Further, the step S2 is specifically as follows: according to the excitation source information input in step S1, clarify the structural noise optimization target, carry out structural design for the vibration line spectrum peak of the selected frequency, determine the key design parameters of the periodic frame, match the line spectrum corresponding frequency with the frame vibration band gap frequency range, make the target frequency within the band gap frequency range, reduce the frame vibration transmission, and reduce the underwater radiation noise, thereby obtaining an improved frame model and an original frame model.

[0019] Furthermore, the improved frame model is of comparable quality to the original frame model.

[0020] Further, 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, change the non-periodic unit structure parameters, thereby improving the periodic defect characteristics in the plate frame model, and obtaining a low-noise plate frame structure with non-periodic characteristics.

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

[0022] Furthermore, step S4 is specifically as follows: 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 obtained in the general design scheme, the vibration responses of the two under the same excitation, boundary and other conditions are calculated, and the feasibility and effectiveness of the frame optimization scheme are verified.

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

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

[0025] The beneficial effects of the present invention are as follows: the present invention provides a method for designing a low-noise hull frame based on the bandgap theory. The 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 frequency spectrum 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, which effectively avoids the disadvantages of traditional means and meets the current needs of ship vibration reduction design. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0028] Figure 3 This is a schematic diagram of the structure of the original plate frame model in an embodiment of the present invention;

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

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

[0031] Figure 6 It is a curve diagram of average acceleration level of outer plate nodes of the improved plate frame model in the embodiment of the present invention;

[0032] Figure 7 It is a 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 It is a curve diagram of average acceleration level of outer plate nodes of the improved plate frame model with non-periodic characteristics in an embodiment of the present invention;

[0034] Fig. 9 : It is a comparison diagram of the vibration response of the plate frame model in the embodiment of the present invention, wherein (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; (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 in conjunction with 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 the 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] According to the excitation source information input in step 1, the optimization target of structural noise is clarified, the structural design is carried out for the peak value of the vibration line spectrum of the selected frequency, the key design parameters of the periodic frame are determined, and the corresponding frequency of the line spectrum is matched with the frequency range of the vibration band gap of the frame. The target frequency is placed in the band gap frequency range, the vibration transmission of the frame is reduced, and the underwater radiation noise is reduced, thereby obtaining an improved frame model and an original 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 Figure 4 As shown in the figure, the original plate frame model contains loads, boundary conditions, equipment information and vibration isolation parameter inputs. The calculation results show that when the frequency is 59Hz, 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 From the comparison of the frequency response curves shown, it can be found that at the position corresponding to the target frequency of 59Hz, the response peak of the original frame is reduced. At the same time, in the frequency range of 0-200Hz, the total acceleration level of the outer panel of the frame structure is also reduced to a certain extent.

[0044] Step 3: Optimization design of 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, it is necessary to optimize the periodic plate frame obtained in step 2 according to the requirements of equipment layout, change the non-periodic unit structure parameters, thereby improving the periodic defect characteristics in the plate frame model and obtaining a low-noise plate frame structure with non-periodic characteristics.

[0046] In actual ships, there is usually 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 certain longitudinal profile in the optimized plate 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 frame model obtained in step 2 or step 3 and the improved frame model with non-periodic characteristics with the original 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 frame optimization scheme.

[0049] refer to Figure 8 , 9 As shown in the figure, 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 Fig. 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 the above steps 1 to 4 also needs to meet the basic strength requirements, so it is necessary to carry out strength verification based on the above scheme. In the hull structure, the total strength and local strength requirements must be met at the same time. If the strength requirements are not met, steps 2 to 5 must be repeated. According to the calculation results, the low-noise plate frame structure parameters can be further optimized to obtain the optimized plate frame structure.

[0054] The beneficial effects are as follows: 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-isolating effect, which effectively avoids the drawbacks of traditional means and meets 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, rather than indicating or implying 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 used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. "Multiple" means two or more. "Installed", "connected", and "connected" 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 is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. 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 protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes 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; S3. Optimal design of plate frame structure with non-periodic characteristics; S4. Verify the optimization scheme design; S5. Structural strength verification.

2. The method for designing a low-noise ship hull frame 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 each working condition according to the equipment data.

3. The method for designing a low-noise ship hull frame 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 step S2 specifically includes: clarifying the structural noise optimization target according to the excitation source information input in step S1, carrying out structural design for the vibration line spectrum peak of the selected frequency, determining the key design parameters of the periodic frame, matching the line spectrum corresponding frequency with the frame vibration band gap frequency range, making the target frequency within the band gap frequency range, reducing the frame vibration transmission, and reducing the underwater radiation noise, thereby obtaining an improved frame model and an original frame model.

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

6. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 1 is characterized in that: The 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, change the non-periodic unit structure parameters, thereby improving the periodic defect characteristics in the plate frame model, and obtaining a low-noise plate frame structure with non-periodic characteristics.

7. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 6 is characterized in that: The calculation inputs such as equipment, excitation, and boundary in the plate frame structure with non-periodic characteristics are consistent with the improved plate frame structure model in steps S1 to S2.

8. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 1 is characterized in that: The step S4 is specifically as follows: 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 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 frame optimization scheme.

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

10. The method for designing a low-noise ship hull frame based on bandgap theory according to claim 9, characterized in that: In the structural strength check of step S5, if the strength requirement is 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.

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