A multi-hull vessel total vibration calculation method

Abstract

The present application relates to a kind of multi-habitat boat total vibration calculation method, comprising the following steps: step one, hull structure-bag-wear layer coupling model creation: multi-habitat boat total vibration calculation model is combined by metal hull, damping air bag and wear layer, three are connected using the way of common node;Step two, total vibration calculation boundary condition under multiple environments: after completing whole ship coupling modeling, reasonable boundary condition needs to be set, and multi-habitat boat total vibration calculation boundary condition should be divided into water surface, ground / ice surface two environments to carry out;Step three, total vibration calculation: after completing modeling and boundary condition setting, submit ABAQUS to calculate total vibration, and calculation is completed.Solve the problem that multi-habitat boat total vibration analysis method cannot fully consider the influence of its own structure composition and working environment on total vibration and is distorted, can be used for the total vibration characteristic prediction of multi-habitat boat under different working environments, and provide technical support for the design of this kind of ship.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration and noise control, in particular to a multi-environment boat total vibration calculation method. BACKGROUND

[0002] The multi-environment boat has the ability to navigate in multi-interface environments such as water surface, ground / ice surface, and ice-water mixed interface. Its special structure makes its total vibration characteristics different from those of conventional water surface boats, and the total vibration characteristics in different navigation environments are different due to the diversity of the navigation environment. These are all important considerations in design, so it is necessary to study the total vibration characteristic calculation method of the multi-environment boat to support the structure design.

[0003] The multi-environment boat is usually composed of a metal boat body structure, a buffer airbag, and a bottom wear-resistant layer, as shown in Figure 1 The weight and stiffness of the buffer airbag and the wear-resistant layer will affect the boat body vibration. In addition, the buffer airbag will also change the stiffness when it is inflated to the working pressure during operation. Therefore, when calculating the total vibration of the multi-environment boat, the simulation of the buffer airbag and the wear-resistant layer and their coupling with the boat body structure need to be considered. The water medium around the boat body will affect the boat body vibration when the multi-environment boat navigates on the water surface, so the influence of the attached water needs to be considered in the total vibration calculation. When the multi-environment boat navigates on the ice surface, the influence of the rigid ground on the free vibration of the boat body needs to be considered.

[0004] In related research, there are total vibration analysis methods for hovercrafts with airbags, but there is no research considering the wear-resistant layer. There are total vibration calculation methods for boats navigating on the water surface, but there is no total vibration calculation method considering the contact boundary condition with the rigid ground.

[0005] Technical problem 1: The influence of the structure composition of the multi-environment boat on the total vibration

[0006] The special structure composition of the multi-environment boat makes its total vibration characteristic calculation different from that of conventional boats, and the coupling of the metal boat body structure, the buffer airbag, and the wear-resistant layer needs to be considered.

[0007] Technical problem 2: The influence of the working environment of the multi-environment boat on the total vibration

[0008] The diversity of the working environment of the multi-environment boat makes its total vibration characteristics different from those of conventional water surface boats, and the influence of the water surface and the ground / ice surface on its natural frequency needs to be considered. SUMMARY

[0009] In view of the problem that the total vibration analysis method of the multi-environment boat does not fully consider the influence of its structure composition and working environment on the total vibration and is distorted, a multi-environment boat total vibration calculation method is proposed.

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

[0011] A multi-habitat boat total vibration calculation method, comprising the following steps:

[0012] Step one, the creation of a boat structure-air bag-wear layer coupling model

[0013] The multi-habitat boat total vibration calculation model is composed of a metal boat body, a damping air bag and a wear layer, and the three are connected in a common node manner;

[0014] Step 1.1, the metal boat structure adopts plate and beam elements to establish a full-boat range finite element model; modeling is performed in the commercial software ABAQUS;

[0015] Step 1.2, the buffer air bag structure first creates an air bag wall using plate elements, and assigns rubber material properties; the air bag material is chlorosulfonated polyethylene; the air bag wall forms a closed cavity and is defined as a surface; then a fluid cavity method is used to establish the gas element inside the air bag; the air inside the air bag is air; define the reference point in the cavity, the reference point is not connected to any element in the model, and only has one degree of freedom, i.e. the pressure inside the fluid cavity;

[0016] Step 1.3, the wear layer is modeled using plate elements, and rubber material properties are set; the wear layer material is high molecular polyethylene; the connection part with the two sides of the ship body adopts a common node manner, and the contact part with the air bag is set as a common node;

[0017] Step two, total vibration calculation boundary conditions in multiple environments

[0018] After completing the full-boat coupling modeling, reasonable boundary conditions need to be set; the multi-habitat boat total vibration calculation boundary conditions should be divided into water surface and ground / ice surface environments;

[0019] Step 2.1, the wear layer, the boat body and the fluid interact in the water floating state; in the floating state on the water surface, the boundary can be considered as completely free; set the fluid-structure interaction of the wear layer in contact with the water, and model the wear layer surface of the boat body as the inner surface of the flow field using three-dimensional fluid elements; set the zero pressure boundary condition at the free liquid surface, and use the non-reflecting boundary condition on the outer surface of the finite 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 restricts the vertical movement freedom of the bottom part of the boat; constrain the vertical freedom of the wear layer plate element nodes at the bottom;

[0021] Step three, total vibration calculation

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

[0023] Step 3.1, set up static analysis step, load the air pressure in the air bag to the working pressure;

[0024] Step 3.2, create modal calculation analysis step, extract calculation modal by Lanczos method, complete total vibration calculation;

[0025] So far, the total vibration calculation of the multi-habitat boat is completed.

[0026] Further, in step 1.1, the materials of the plate and beam elements are all aluminum alloy, the Young's modulus is 70GPa, the Poisson's ratio is 0.33, and the density is 2700kg / m 3 , and the thickness has three specifications of 3mm, 4mm and 5mm.

[0027] Further, in step 1.2, the buffer air bag structure is first created by plate elements to form the air bag wall, and the rubber material properties are given. The air bag material is chlorosulfonated polyethylene, the Young's modulus is 1.25GPa, the Poisson's ratio is 0.45, the density is 1170kg / m 3 , and the thickness is 1.2mm. The air bag wall forms a closed cavity and is defined as a surface. Then the fluid cavity method is used to establish the gas element inside the air bag. The element type is F3D4, the gas inside the air bag is air, the bulk modulus is 1.01×10 -5 GPa, and the density is 1.2kg / m 3 .

[0028] Further, in 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, and the thickness is 8mm.

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

[0030] Further, in step 2.1, the contact surface between the fluid element and the boat structure is connected by TIE.

[0031] Further, in step 2.1, the flow field around the boat is simulated by three-dimensional fluid elements, i.e. AC3D4 elements, and the water radius should be no less than 5 times the structure draft.

[0032] Further, in step 3.1, the static analysis step is set, and the gas pressure in the air bag is loaded to the working pressure 16Kpa, and the specific method is to set the reference point gas pressure value.

[0033] Further, in step 1.1, for the total vibration calculation, the weight and stiffness distribution need to be accurate, so some structural details that have little influence can be simplified, and the model omits structural details that have little influence on calculation, such as knee plates and lightening holes.

[0034] Further, 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 application are:

[0036] The present application provides a multi-habitat boat total vibration calculation method, which can be used for total vibration characteristic prediction of multi-habitat boats in different working environments, and provides technical support for the design of such boats. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a schematic diagram of the transverse section of the multi-habitat boat;

[0038] Figure 2 It is a schematic diagram of the joint connection of the boat body structure-air bag-wear-resistant layer of the present application;

[0039] Figure 3 It is a schematic diagram of the air bag gas unit established based on fluid cavity of the present application;

[0040] Figure 4 It is a schematic diagram of the boundary condition under the ground / ice surface state of the present application;

[0041] Figure 5 It is a flow chart of the multi-habitat boat total vibration calculation method of the present application.

[0042] IDENTIFICATION OF DRAWINGS:

[0043] 1, metal boat body; 2, buffer air bag; 3, wear-resistant layer; 4, metal boat body plate unit; 5, air bag wall plate unit; 6, wear-resistant layer plate unit; 7, metal boat body and air bag wall shared node; 8, air bag wall and wear-resistant layer shared node; 9, shared node between air bag walls; 10, reference point; 11, surface composed of air bag wall plate unit 5; 12, air bag wall plate unit node; 13, wear-resistant layer bottom and ground contact node. DETAILED DESCRIPTION

[0044] The present application will be described in detail below in combination with the drawings and specific embodiments. The present embodiment is implemented on the basis of the technical solution of the present application, and gives a detailed implementation manner and specific operation process, but the protection scope of the present application is not limited to the following embodiments.

[0045] To form a reasonable and effective multi-habitat boat total vibration calculation method, the method steps are as follows:

[0046] I. Coupling model creation of boat body structure-air bag-wear-resistant layer

[0047] The multi-habitat boat total vibration calculation model is composed of a metal boat body, a damping air bag and a wear-resistant layer, as shown in Figure 1 . The three are connected in a common node manner, that is, only the stiffness and weight effects of the air bag and the wear-resistant layer on the total vibration are considered, and the relative friction and slip effects are not considered, as shown in Figure 2 .

[0048] (1) The metal boat body structure adopts plate and beam elements to establish a full-boat range finite element model. The modeling is carried out in the commercial software ABAQUS, the plate and beam element materials are all aluminum alloy, the Young's modulus is 70 GPa, the Poisson's ratio is 0.33, the density is 2700 kg / m 3 , and the thickness has three specifications of 3 mm, 4 mm and 5 mm. For total vibration calculation, the accurate weight and stiffness distribution is needed, so some structural details with less influence can be simplified, such as the knee plate and the lightening hole. Finally, the material density is adjusted to make the weight distribution consistent with the actual loading state;

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

[0050] (3) The wear-resistant layer is modeled by using plate elements, and rubber material properties are set. The wear-resistant layer material is high molecular polyethylene, and the thickness is 8 mm. The connection part with the two sides of the ship body adopts a common node manner, and the contact part with the air bag is set as a common node.

[0051] ​II. Boundary conditions for total vibration calculation in multiple environments

[0052] After the full-boat coupling modeling is completed, reasonable boundary conditions need to be set. The total vibration calculation boundary conditions of the amphibious boat should be divided into water surface and ground / ice surface environments.

[0053] (4) Interaction between wear-resistant layer and fluid in water floating state. In the floating state on the water surface, the boundary can be considered completely free. The interaction between the wear-resistant layer and the fluid is set as fluid-structure coupling. The flow field around the boat body is simulated by three-dimensional fluid elements, i.e., AC3D4 elements. The water radius should be no less than 5 times the structure draft. The surface of the boat body wear-resistant layer is modeled as the inner surface of the flow field. Zero pressure boundary conditions are set at the free surface, and non-reflecting boundary conditions are used for the outer surface of the finite water area to simulate the far-field boundary conditions. The contact surface between the fluid element and the boat structure is connected by TIE. The density of seawater in the flow field is ρ = 1025 kg / m 3 , the sound speed in seawater is c = 1450 m / s, the bulk modulus of seawater is K = ρc 2 ; the air density in the air impedance boundary condition is ρ a = 1.29 kg / m 3 , the sound speed in air is c a = 340 m / s, and the air impedance is Z a = ρ a c a .

[0054] (5) Smooth ground / ice surface state can be considered as a rigid ground, which restricts the vertical freedom degree of the boat bottom. The boundary of the boat floating on the water surface can be considered completely free, but for the boat running on the smooth ground, the calculation result will not be consistent with the actual situation if the free boundary condition is used. The boundary condition of the bottom wear-resistant layer plate element node (see Figure 4 Figure 13) vertical freedom degree is constrained.

[0055] III. Total vibration calculation

[0056] After the modeling and boundary condition setting are completed, submit ABAQUS for total vibration calculation:

[0057] (6) Set the static analysis step, load the gas pressure in the airbag to the working pressure of 16 Kpa. The specific way is to set the air 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 boat is completed, and the main process is shown in Figure 5 .

[0060] References:

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

[0062] [2] Sun Di, Research on the 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. Research on the bending resistance performance of offshore inflatable membrane structure based on fluid cavity method[J]. China Shipbuilding, 2023, Vol. 64 (No. 3), 13-22.

[0064] The above-described embodiments only express one embodiment of the present application, which is described in more detail and in detail, but should not be construed as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application patent should be subject to the appended claims.

Claims

1. A method for calculating the total vibration of a multi-purpose vessel, characterized in that, Includes the following steps: Step 1: Creating a Coupled Model of Hull Structure, Airbags, and Wear-Resistant Layer The overall vibration calculation model of the amphibious vessel consists of a metal hull, vibration damping airbags, and a wear-resistant layer, which are connected by sharing nodes. Step 1.1: A full-scale finite element model of the metal hull structure is established using plate and beam elements; the model is then built using the commercial software ABAQUS. Step 1.2: The airbag structure first uses plate elements to create the airbag wall, assigning it rubber material properties. The airbag material is chlorosulfonated polyethylene. The airbag wall forms a closed cavity and is defined as a surface. Then, the gas element inside the airbag is established using the fluid cavity method. The gas inside the airbag is air. A reference point is defined inside the cavity. The reference point is not connected to any element 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 using plate elements, and the rubber material properties are set. The wear-resistant layer material is high molecular weight polyethylene. The connection between the wear-resistant layer and the two sides of the hull is made using a common node method, and the part in contact with the airbag is also made using a common node method. Step 2: Boundary conditions for total vibration calculation under multiple environments After completing the coupled modeling of the entire vessel, reasonable boundary conditions need to be set. The boundary conditions for the total vibration calculation of the amphibious vessel should be divided into two environments: water surface and land / ice surface. Step 2.1: Interaction between the wear-resistant layer, hull, and fluid in the floating state; When floating on the water surface, its boundary can be regarded as completely free. The fluid-structure interaction between the wear-resistant layer and the water is set. The flow field around the hull is modeled using three-dimensional fluid elements. The surface of the wear-resistant layer of the hull is modeled as the inner surface of the flow field. Zero pressure boundary conditions are set at the free liquid surface, and non-reflective boundary conditions are used on the outer surface of the finite water area to simulate the far-field boundary conditions. Step 2.2: The smooth ground / ice surface can be regarded as a rigid ground. The rigid ground restricts the vertical motion degree of freedom of the bottom part of the boat; the boundary conditions constrain the vertical degree of freedom of the bottom wear-resistant plate unit nodes. Step 3: Total Vibration Calculation After completing the modeling and boundary condition settings, submit the ABAQUS calculation to calculate the total vibration: Step 3.1: Set up the static analysis step and load the gas pressure inside the airbag to the working pressure; Step 3.2: Create a modal calculation and analysis step, use the Lanczos method to extract calculation modes, and complete the total vibration calculation; At this point, the total vibration calculation for the multi-purpose vessel is complete.

2. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 1.1, both the plate and beam elements are made of aluminum alloy with a Young's modulus of 70 GPa, a Poisson's ratio of 0.33, and a density of 2700 kg / m³. 3 The thickness is available in three specifications: 3mm, 4mm and 5mm.

3. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 1.2, the airbag structure first uses plate units to create the airbag wall, giving it the properties of rubber material. 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 / m³. 3 The thickness is 1.2 mm; the airbag wall forms a closed cavity and is defined as the surface; then, the gas element inside the airbag is constructed using the fluid cavity method, with the element type being F3D4, and the gas inside the airbag is air with a bulk modulus of 1.01 × 10⁻⁶. -5 GPa, density 1.2 kg / m³ 3 .

4. The method for calculating the total vibration of a multi-purpose 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 weight polyethylene with a thickness of 8mm.

5. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 2.1, the density of seawater in the flow field =1025kg / m 3 Speed ​​of sound in seawater =1450m / s, seawater bulk modulus Air density in air impedance boundary conditions =1.29kg / m 3 Speed ​​of sound in air =340m / s, air resistance .

6. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 2.1, the contact surfaces between the fluid unit and the hull structure are connected using TIE.

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

8. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 3.1, a static analysis step is set up, where the gas pressure inside the airbag is loaded to the working pressure of 16 kPa. Specifically, the gas pressure value of the reference point is set.

9. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 1.1, for the calculation of total vibration, the weight and stiffness distribution need to be accurate. For this purpose, structural details with less impact can be simplified.

10. The method for calculating the total vibration of a multi-purpose vessel according to claim 1, characterized in that, In step 1.1, the material density is finally adjusted so that the weight distribution matches the actual loading condition.

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