Total vibration calculation method for multi-habitat boat

Abstract

The invention relates to a method for calculating the total vibration of a multi-habitat boat, which comprises the following steps of: 1, creating a boat body structure-air bag-wear-resistant layer coupling model: combining a metal boat body, a vibration reduction air bag and a wear-resistant layer, and connecting the metal boat body, the vibration reduction air bag and the wear-resistant layer in a node-sharing manner; step 2, total vibration calculation boundary conditions in multiple environments: after the coupling modeling of the whole boat is completed, reasonable boundary conditions need to be set, and the total vibration calculation boundary conditions of the multi-habitat boat should be carried out in a water surface environment and a ground / ice surface environment; and step 3, total vibration calculation: after modeling and boundary condition setting are completed, ABAQUS calculation total vibration is submitted, and calculation is completed. The method solves the problem that the method for analyzing the total vibration of the multi-habitat boat is distorted due to the fact that the influence of the self structural composition and the working environment on the total vibration is not fully considered, can be used for forecasting the total vibration characteristics of the multi-habitat boat in different working environments, and provides technical support for the design of the multi-habitat boat.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration and noise control, and in particular to a method for calculating the total vibration of an amphibious vessel. Background Art

[0002] Amphibious vessels have the ability to navigate in multiple interface environments such as water surface, ground / ice surface, and ice-water mixed interface. Their special structure makes their total vibration characteristics different from those of conventional surface vessels. At the same time, due to the diversity of navigation environments, the total vibration characteristics in different navigation environments are different. These are all key considerations during design. Therefore, it is necessary to study the calculation method of the total vibration characteristics of amphibious vessels to support structural design.

[0003] Amphibious boats are usually composed of three parts: a metal hull structure, a cushioning airbag and a bottom wear-resistant layer. Figure 1 As shown in the figure, the weight and stiffness of the cushion airbag and the wear-resistant layer will affect the vibration of the hull. In addition, the cushion airbag will be inflated to the working pressure when it is working, which will also cause changes in stiffness. Therefore, when calculating the total vibration of the amphibious boat, it is necessary to consider the simulation of the cushion airbag and the wear-resistant layer and their coupling with the hull structure. When the amphibious boat is sailing on the water, the water medium around the hull will affect the vibration of the hull. The influence of attached water needs to be considered when calculating the total vibration; when sailing on the ice, it is necessary to consider the influence of the rigid ground on the free vibration of the hull.

[0004] In related research, there are total vibration analysis methods for hovercraft with airbag structures, but there is no research that considers the wear-resistant layer; there are total vibration calculation methods for boats under surface navigation, but there is no total vibration calculation method that considers the contact boundary conditions with the rigid ground.

[0005] Technical Problem 1: The impact of the amphibious vessel’s own structural composition on the overall vibration

[0006] The special structure of the amphibious boat makes the calculation of its total vibration characteristics different from that of conventional boats. It is necessary to comprehensively consider the coupling effect of the metal hull structure, the cushioning airbag, and the wear-resistant layer.

[0007] Technical Problem 2: Impact of the Amphibious Craft Working Environment on Total Vibration

[0008] The diversity of the working environment of amphibious vessels makes their overall vibration characteristics different from those of conventional surface vessels, and the influence of the water surface, ground / ice surface on their natural frequency must be considered. Summary of the invention

[0009] Aiming at the problem that the total vibration analysis method of amphibious craft fails to fully consider the influence of its own structure and working environment on the total vibration and causes distortion, a total vibration calculation method of amphibious craft is proposed.

[0010] The technical solution of the present invention is:

[0011] A method for calculating the total vibration of an amphibious vessel comprises the following steps:

[0012] Step 1: Create a coupled model of hull structure, airbag and wear-resistant layer

[0013] The total vibration calculation model of the amphibious boat is composed of a metal hull, a vibration-damping airbag and a wear-resistant layer, and the three are connected by a common node.

[0014] Step 1.1: The metal hull structure uses plate and beam elements to establish a finite element model of the entire boat; the modeling is performed in the commercial software ABAQUS;

[0015] Step 1.2, cushioning airbag structure First, the airbag wall is created using plate units and given rubber material properties. The airbag material is chlorosulfonated polyethylene; the airbag wall constitutes a closed cavity and is defined as a surface; then the gas unit inside the airbag is established using the fluid cavity method, and the gas inside the airbag is air; define the reference point in the cavity, which is not connected to any unit in the model and has only one degree of freedom, namely the pressure inside the fluid cavity;

[0016] Step 1.3, the wear-resistant layer is modeled by plate elements, and the rubber material properties are set. The wear-resistant layer material is high molecular polyethylene; the connection part with both sides of the hull adopts the common node method, and the part in contact with the airbag is set as a common node;

[0017] Step 2: Boundary conditions for total vibration calculation under multiple environments

[0018] After completing the coupling modeling of the entire boat, reasonable boundary conditions need to be set. The boundary conditions for the total vibration calculation of the amphibious boat should be divided into two environments: water surface and ground / ice surface.

[0019] Step 2.1, the wear-resistant layer, hull and fluid interact in the floating state on the water surface; when floating on the water surface, its boundary can be regarded as completely free, and the fluid-solid coupling interaction between the wear-resistant layer and the water is set. The flow field around the hull adopts a three-dimensional fluid unit, and the surface of the wear-resistant layer of the hull is modeled as the inner surface of the flow field; a zero pressure boundary condition is set at the free liquid surface, and a non-reflection boundary condition is used on the outer surface of the limited water area to simulate the far-field boundary condition;

[0020] Step 2.2, the smooth ground / ice surface state can be regarded as a rigid ground, which limits the vertical freedom of the bottom part of the boat; the boundary conditions constraining the vertical freedom of the bottom wear-resistant layer plate unit node;

[0021] Step 3: Calculation of total vibration

[0022] After completing the modeling and boundary condition settings, submit ABAQUS to calculate the total vibration:

[0023] Step 3.1, set the static analysis step and load the gas pressure in the airbag to the working pressure;

[0024] Step 3.2, create a modal calculation analysis step, use the Lanczos method to extract the calculation mode, and complete the total vibration calculation;

[0025] At this point, the total vibration calculation of the amphibious vessel is completed.

[0026] Furthermore, in step 1.1, the plate and beam unit materials are aluminum alloy, with a Young's modulus of 70 GPa, a Poisson's ratio of 0.33, and a density of 2700 kg / m 3 The thickness is available in three specifications: 3mm, 4mm and 5mm.

[0027] Furthermore, in step 1.2, the cushioning airbag structure first uses plate elements to create the airbag wall and assigns rubber material properties. The airbag material is chlorosulfonated polyethylene, with a Young's modulus of 1.25 GPa, a Poisson's ratio of 0.45, and a density of 1170 kg / m 3 , with a thickness of 1.2 mm; the airbag wall constitutes a closed cavity and is defined as a surface; the fluid cavity method is then used to establish the gas unit inside the airbag, the unit type is F3D4, the gas inside the airbag is air, and the bulk modulus is 1.01×10 -5 GPa, density 1.2 kg / m 3 .

[0028] Furthermore, in step 1.3, the wear-resistant layer is modeled using plate elements, and the rubber material properties are set. The wear-resistant layer material is high molecular polyethylene with a thickness of 8 mm.

[0029] Furthermore, in step 2.1, the seawater density in the flow field is ρ = 1025 kg / m 3 , the speed of sound in seawater c = 1450m / s, the bulk modulus of seawater K = ρc 2 ; Air density ρ in air impedance boundary condition a =1.29kg / m 3 , the speed of sound in air c a =340m / s, air impedance Z a =ρ a c a .

[0030] Furthermore, in step 2.1, the contact surface between the fluid unit and the hull structure is connected by TIE.

[0031] Furthermore, in step 2.1, the flow field around the hull is simulated using a three-dimensional fluid unit, namely, an AC3D4 unit, and the water area radius should be no less than 5 times the structural draft.

[0032] Furthermore, in step 3.1, a static analysis step is set to load the gas pressure in the airbag to the working pressure of 16Kpa, specifically by setting the air pressure value of the reference point.

[0033] Furthermore, in step 1.1, for the total vibration calculation, the accurate distribution of weight and stiffness is required. For this purpose, the structural details with less influence can be simplified to a certain extent, and the structural details with less influence on the calculation, such as brackets and lightening holes, are omitted in the model.

[0034] Furthermore, in step 1.1, the material density is finally adjusted so that the weight distribution conforms to the actual loading state.

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

[0036] The present invention provides a method for calculating the total vibration of an amphibious boat, which can be used to predict the total vibration characteristics of the amphibious boat under different working environments, and provide technical support for the design of such boats. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the cross section of an amphibious boat;

[0038] Figure 2 This is a schematic diagram of the common node connection of the hull structure-airbag-wear-resistant layer of the present invention;

[0039] Figure 3 The schematic diagram of the gas unit in the airbag based on the fluid cavity is shown in the present invention;

[0040] Figure 4 It is a schematic diagram of boundary conditions in the ground / ice surface state of the present invention;

[0041] Figure 5 The figure is a flow chart of the total vibration calculation method of the amphibious vessel of the present invention.

[0042] Figure ID:

[0043] 1. Metal hull; 2. Cushion airbag; 3. Wear-resistant layer; 4. Metal hull plate unit; 5. Airbag wall plate unit; 6. Wear-resistant layer plate unit; 7. Common node between metal hull and airbag wall; 8. Common node between airbag wall and wear-resistant layer; 9. Common node between airbag walls; 10. Reference point; 11. Surface composed of airbag wall plate unit 5; 12. Airbag wall plate unit node; 13. Node where the bottom of the wear-resistant layer contacts the ground. DETAILED DESCRIPTION

[0044] 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.

[0045] In order to form a reasonable and effective method for calculating the total vibration of an amphibious vessel, the method steps are as follows:

[0046] 1. Creation of the coupling model of hull structure, airbag and wear-resistant layer

[0047] The total vibration calculation model of the amphibious boat is composed of a metal hull, a vibration-damping airbag and a wear-resistant layer. Figure 1 The three are connected by a common node, that is, only the stiffness and weight of the airbag and the wear-resistant layer on the total vibration are considered, and their relative friction and slip are not considered, as shown in Figure 2 shown.

[0048] (1) The metal hull structure uses plate and beam elements to establish a finite element model of the entire boat. The modeling was carried out in the commercial software ABAQUS. The plate and beam element materials are all aluminum alloys with a Young's modulus of 70 GPa, a Poisson's ratio of 0.33, and a density of 2700 kg / m 3 The thickness is 3mm, 4mm and 5mm. For the total vibration calculation, the weight and stiffness distribution need to be accurate. For this purpose, the structural details with less influence can be simplified to a certain extent. The structural details with less influence on the calculation, such as brackets and lightening holes, are omitted in the model. Finally, the material density is adjusted to make the weight distribution conform to the actual loading state;

[0049] (2) As an inflatable closed structure, the cushioning airbag interacts with the internal air under external excitation, and the gas-solid coupling effect needs to be considered. First, the airbag wall is created using plate elements and the rubber material properties are given. The airbag material is chlorosulfonated polyethylene (Hypalon), with a Young's modulus of 1.25 GPa, a Poisson's ratio of 0.45, and a density of 1170 kg / m 3 The thickness is 1.2 mm; the airbag wall forms a closed cavity and is defined as a surface; the fluid cavity method is then used to establish the gas unit inside the airbag. The unit type is F3D4, the gas inside the airbag is air, and the bulk modulus is 1.01×10 -5 GPa, density 1.2 kg / m 3 . Define the reference point in the cavity (see Figure 3 The reference point is not connected to any unit in the model and has only one degree of freedom, namely the pressure inside the fluid cavity. Figure 3 shown.

[0050] (3) The wear-resistant layer is modeled with plate elements and the rubber material properties are set. The wear-resistant layer material is high molecular polyethylene with a thickness of 8 mm. The connection part with both sides of the hull adopts the common node method, and the part in contact with the airbag is set as a common node.

[0051] 2. Boundary conditions for total vibration calculation under multiple environments

[0052] After completing the coupling modeling of the entire boat, reasonable boundary conditions need to be set. The boundary conditions for the total vibration calculation of the amphibious boat should be divided into two environments: water surface and ground / ice surface.

[0053] (4) Interaction between the wear-resistant layer, hull and fluid when floating on the water surface. When floating on the water surface, its boundary can be regarded as completely free. The fluid-solid coupling interaction between the wear-resistant layer and the water is set. The flow field around the hull is simulated by a three-dimensional fluid unit, namely, the AC3D4 unit. The radius of the water area should be no less than 5 times the structural draft. The surface of the wear-resistant layer of the hull is modeled as the inner surface of the flow field. A zero pressure boundary condition is set at the free liquid surface, and a non-reflecting boundary condition is used on the outer surface of the limited water area to simulate the far-field boundary condition. The contact surface between the fluid unit and the hull structure is connected by TIE. The density of seawater in the flow field is ρ = 1025 kg / m 3 , the speed of sound in seawater c = 1450m / s, the bulk modulus of seawater K = ρc 2 ; Air density ρ in air impedance boundary condition a =1.29kg / m 3 , the speed of sound in air c a =340m / s, air impedance Z a =ρ a c a .

[0054] (5) The smooth ground / ice surface state can be regarded as a rigid ground, which limits the vertical freedom of the bottom part of the boat. The boundary of a ship floating on the water surface can be regarded as completely free. However, for a ship traveling on a smooth ground, if the free boundary condition is used for calculation, the result will not be consistent with the actual situation. Constrain the bottom wear-resistant layer plate unit nodes (see Figure 4 13) Boundary conditions for the vertical degrees of freedom.

[0055] 3. Total vibration calculation

[0056] After completing the modeling and boundary condition settings, submit ABAQUS to calculate the total vibration:

[0057] (6) Set the static analysis step and load the gas pressure in the airbag to the working pressure of 16KPa. The specific method is to set the pressure value of the reference point;

[0058] (7) Create a modal calculation analysis step, use the Lanczos method to extract the calculation mode, and complete the total vibration calculation.

[0059] At this point, the total vibration calculation of the amphibious craft is completed. The main process is as follows: Figure 5 shown.

[0060] References:

[0061] [1] Xu Wei, Research on the calculation method of total vibration of full-cushion air cushion vehicle[D]. Dalian University of Technology, 2018.

[0062] [2] Sun Di, Research on simplified analysis method of total vibration of full-cushion air cushion vehicle[D]. Dalian University of Technology, 2020.

[0063] [3] Ye Yunling, Gan Jin, Zheng Zhongyi, et al., Study on the flexural bearing performance of offshore inflatable membrane structures based on fluid cavity method [J]. China Shipbuilding. 2023, Vol. 64 (Issue 3), 13-22.

[0064] The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for calculating the total vibration of an amphibious vessel, characterized in that: The following steps are involved: Step 1: Create a coupled model of hull structure, airbag and wear-resistant layer The total vibration calculation model of the amphibious boat is composed of a metal hull, a vibration-damping airbag and a wear-resistant layer, and the three are connected by a common node. Step 1.1: The metal hull structure uses plate and beam elements to establish a finite element model of the entire boat; the modeling is performed in the commercial software ABAQUS; Step 1.2, cushioning airbag structure First, the airbag wall is created using plate units and given rubber material properties. The airbag material is chlorosulfonated polyethylene; the airbag wall constitutes a closed cavity and is defined as a surface; then the gas unit inside the airbag is established using the fluid cavity method, and the gas inside the airbag is air; define the reference point in the cavity, which is not connected to any unit in the model and has only one degree of freedom, namely the pressure inside the fluid cavity; Step 1.3, the wear-resistant layer is modeled by plate elements, and the rubber material properties are set. The wear-resistant layer material is high molecular polyethylene; the connection part with both sides of the hull adopts the common node method, and the part in contact with the airbag is set as a common node; Step 2: Boundary conditions for total vibration calculation under multiple environments After completing the coupling modeling of the entire boat, reasonable boundary conditions need to be set. The boundary conditions for the total vibration calculation of the amphibious boat should be divided into two environments: water surface and ground / ice surface. Step 2.1, the wear-resistant layer, hull and fluid interact in the floating state on the water surface; when floating on the water surface, its boundary can be regarded as completely free, and the fluid-solid coupling interaction between the wear-resistant layer and the water is set. The flow field around the hull adopts a three-dimensional fluid unit, and the surface of the wear-resistant layer of the hull is modeled as the inner surface of the flow field; a zero pressure boundary condition is set at the free liquid surface, and a non-reflection boundary condition is used on the outer surface of the limited water area to simulate the far-field boundary condition; Step 2.2, the smooth ground / ice surface state can be regarded as a rigid ground, which limits the vertical freedom of the bottom part of the boat; the boundary conditions constraining the vertical freedom of the bottom wear-resistant layer plate unit node; Step 3: Total vibration calculation After completing the modeling and boundary condition settings, submit ABAQUS to calculate the total vibration: Step 3.1, set the static analysis step and load the gas pressure in the airbag to the working pressure; Step 3.2, create a modal calculation analysis step, use the Lanczos method to extract the calculation mode, and complete the total vibration calculation; At this point, the total vibration calculation of the amphibious vessel is completed.

2. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 1.1, the plate and beam unit materials are aluminum alloy, with a Young's modulus of 70 GPa, a Poisson's ratio of 0.33, and a density of 2700 kg / m 3 The thickness is available in three specifications: 3mm, 4mm and 5mm.

3. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 1.2, the cushioning airbag structure first uses plate elements to create the airbag wall and assigns rubber material properties. The airbag material is chlorosulfonated polyethylene, with a Young's modulus of 1.25 GPa, a Poisson's ratio of 0.45, and a density of 1170 kg / m 3 , with a thickness of 1.2 mm; the airbag wall constitutes a closed cavity and is defined as a surface; the fluid cavity method is then used to establish the gas unit inside the airbag, the unit type is F3D4, the gas inside the airbag is air, and the bulk modulus is 1.01×10 -5 GPa, density 1.2 kg / m 3 .

4. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 1.3, the wear-resistant layer is modeled using plate elements, and the rubber material properties are set. The wear-resistant layer material is high molecular polyethylene with a thickness of 8 mm.

5. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 2.1, the density of seawater in the flow field is ρ = 1025 kg / m 3 , the speed of sound in seawater c = 1450m / s, the bulk modulus of seawater K = ρc 2 ; Air density ρ in air impedance boundary condition a =1.29kg / m 3 , the speed of sound in air c a =340m / s, air impedance Z a =ρ a c a .

6. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 2.1, the contact surface between the fluid unit and the hull structure is connected by TIE.

7. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 2.1, the flow field around the hull is simulated using a three-dimensional fluid unit, namely, the AC3D4 unit, and the water area radius should be no less than 5 times the structural draft.

8. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 3.1, set the static analysis step and load the gas pressure in the airbag to the working pressure of 16Kpa. The specific method is to set the air pressure value of the reference point.

9. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 1.1, for the total vibration calculation, the accurate distribution of weight and stiffness is required. For this purpose, the structural details with less influence can be simplified to a certain extent. The structural details with less influence on the calculation, such as brackets and lightening holes, are omitted in the model.

10. The method for calculating the total vibration of an amphibious vessel according to claim 1, characterized in that: In step 1.1, the material density is finally adjusted so that the weight distribution conforms to the actual loading state.

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