A wide-area sea ice dynamic break-up model generation method

Abstract

The application discloses a wide-area sea ice dynamic damage model generation method, and belongs to the technical field of polar engineering, which comprises the following steps: determining the geometric size and physical parameters of the sea ice area; establishing a fracture area calculation model; establishing a sea ice non-fracture area calculation model; step-by-step solving to determine the time step of different calculation domains; iterative calculation, interactive transmission of physical information of different calculation domains; judging the contact between sea ice and structures; calculating ice force pulsation, sea ice deformation and damage field; judging whether the crack extends to the fracture area; judging whether the time iteration step reaches the maximum increment step, and outputting the calculation after the maximum increment step is reached. The application adopts the above method, uses the hybrid algorithm of OSBPD-NLFEM to construct a wide-area sea ice environment field, uses the OSBPD method suitable for damage problems to simulate the crack initiation and expansion of the ice body by presetting the sea ice fracture area, and greatly reduces the time consumption of the calculation.

Description

Technical Field

[0001] This invention relates to the field of polar engineering technology, and in particular to a method for generating a wide-area sea ice dynamic damage model. Background Technology

[0002] With the expansion of polar resource development and shipping activities, the dynamic coupling effect between sea ice fields and marine equipment has become a core challenge restricting engineering safety. Current numerical simulations of sea ice are mostly based on continuum theory or meshless methods. However, while the conventional finite element method can effectively characterize the dynamic response of structures, it cannot accurately capture the crack propagation and discontinuous failure of the ice field induced by ice-solid impact. Meshless methods such as discrete element methods or near-field dynamics methods can describe ice fragmentation, but their computational efficiency limits their ability to achieve dynamic reconstruction of large-scale sea ice fields. Therefore, in order to better analyze the structural dynamic characteristics of structures interacting with the sea ice environment, there is an urgent need to develop a method for generating wide-area sea ice dynamic failure models. Summary of the Invention

[0003] The purpose of this invention is to provide a method for generating a wide-area sea ice dynamic failure model. It uses a hybrid algorithm of conventional state-based near-field dynamics (OSBPD) and nonlinear finite element method (NLFEM) to construct a wide-area sea ice environment field. By pre-setting the sea ice fracture region and adopting the OSBPD method adapted to failure problems, it simulates the initiation and propagation of ice cracks, which greatly reduces the computation time.

[0004] To achieve the above objectives, the present invention provides a method for generating a wide-area sea ice dynamic failure model, comprising the following steps:

[0005] S1. Determine the geometric dimensions and physical parameters of the sea ice area;

[0006] S2. Initially define the initial fracture zone of sea ice and establish a calculation model for the fracture zone;

[0007] S3. Establish a calculation model for the non-fractured region of sea ice;

[0008] S4. A step-by-step solution strategy is adopted, with different time steps for the sea ice fracture region and the non-fracture region, and the number of time iteration steps for the coupling interface update is set.

[0009] S5. Determine the overall time increment step, set the coupling interface conditions between the fractured and non-fractured regions, and perform iterative calculations;

[0010] S6. Determine the contact between the structure and sea ice based on the surface shape of the marine structure, and calculate the ice load on the structure.

[0011] S7. Calculate ice force pulsation, sea ice deformation and failure field, and output sea ice deformation cloud map and dynamic failure cloud map;

[0012] S8. Determine whether the sea ice crack extends into the non-fracture region. If so, delete the finite element elements in the crack tip region.

[0013] S9. Determine if the number of time iteration steps has reached the maximum increment step. If yes, stop the calculation; otherwise, repeat steps S4-S8 until the number of time iteration steps reaches the maximum increment step.

[0014] Preferably, the geometric dimensions and physical parameters of the sea ice region in step S1 include the length L, width B, and thickness H of the sea ice region, as well as the elastic modulus E, Poisson's ratio ν, density ρ, and fracture toughness K of the sea ice. I .

[0015] Preferably, in step S2, the fracture and crack occurrence regions of sea ice are initially predefined, wherein the length of the fracture and crack occurrence region is L1, the width is B1, and the thickness is H1. The occurrence region is discretized using conventional state-based near-field dynamics methods to obtain the initial coordinates (x, y, y) of different particle points. i y i , z i (0)).

[0016] Preferably, in step S3, the non-fractured region is discretized in a mesh space using the nonlinear finite element method.

[0017] Preferably, step S4 includes:

[0018] The time step for both the sea ice fracture region and the non-fracture region is set using the following formula:

[0019]

[0020] In the formula, Δt FEM Indicates the time step of the non-fractured region; Δt PD The time step represents the fracture region; l represents the characteristic length of the mesh element; E represents the elastic modulus of sea ice; ν represents the Poisson's ratio of sea ice; a and d represent sea ice-related parameters in the peridynamics method; δ represents the neighborhood radius in the peridynamics method; ξ lk V represents the initial distance between matter point l and matter point k. j ξ represents the volume of substance point j. lj The initial distance ξ between matter point l and matter point j kj This represents the initial distance between matter point k and matter point j;

[0021] Set the time iteration step for updating the coupling interface. For the fractured region, information exchange occurs once between the non-fractured region after every m1 iterations, as shown in the formula:

[0022] m1Δt PD=m2Δt FEM ;

[0023] In the formula, m2 represents the number of time iteration steps in the non-fracture region; m1 represents the number of time iteration steps in the fracture region; m1 and m2 are the smallest integers that can be taken.

[0024] Preferably, step S5 specifically includes:

[0025] Determine the total time increment step and set the initial time iteration step number k = 1;

[0026] Set the coupling interface conditions between the fractured and non-fractured regions. For the coupling interface, it is both a finite element mesh node and a meshless particle point. Its motion control equation is obtained by conventional state-based near-field dynamics method.

[0027] The coupling interface transmits the obtained particle velocity and displacement to the finite element mesh nodes that share the same spatial location with it.

[0028] The motion information of the particle points at the coupling interface is obtained and used as the moving boundary of the non-fractured region. The information of all mesh nodes in the non-fractured region is updated, and the mesh nodes satisfy the dynamic equilibrium equation of the finite element structure.

[0029] After the mesh nodes are calculated, the mesh nodes within the neighborhood of the coupled boundary particle points are used as the particle points within the neighborhood, so as to realize the control of the fractured area by the non-fractured area. If the mesh size is larger than the particle point size radius, the principle of shape function space allocation is used to equivalently allocate the motion and position information of the mesh nodes to the particle points.

[0030] Preferably, in step S8, the damage level of particle points sharing the same spatial location with the mesh nodes in the interface is used to determine whether the sea ice crack has extended to the non-fracture region. The formula is as follows:

[0031] s ij <s0;

[0032]

[0033] In the formula, s ij si represents the relative deformation length between boundary layer particle i and its neighboring particle j; s0 represents the limiting elongation of the particle point pair.

[0034] Therefore, the present invention employs the above-described method for generating a wide-area sea ice dynamic destruction model, which has the following beneficial effects:

[0035] (1) The conventional state-type peri-field dynamics method is used to establish a dynamic fracture model of sea ice, which can overcome the limitations of the bond-type peri-field dynamics method in simulating sea ice materials. The coupling method used can realize the interactive transmission of displacement and velocity information between the discontinuous and continuous domains of sea ice. Compared with the existing peri-field dynamics method or nonlinear finite element method single coupling model, the displacement deformation coordination effect at the coupling boundary is smoother and the coupling effect is better.

[0036] (2) To address the computational divergence problem caused by sea ice cracks extending into the finite element domain under extreme conditions, stable convergence of the computation is ensured by deleting the finite element mesh in this region.

[0037] (3) It can quickly realize the numerical solution of ice force and sea ice failure in the interaction between the structure and the wide-area sea ice environment field, thus providing technical support for the performance prediction and structural design of polar structures.

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0039] Figure 1 This is a flowchart of a method according to an embodiment of the present invention;

[0040] Figure 2 This is a model diagram of the sea ice area according to an embodiment of the present invention;

[0041] Figure 3 This is a diagram of the method for modeling the sea ice area according to an embodiment of the present invention.

[0042] Figure 4 This is a simulation diagram of the micro-deformation transmission of the interaction between the ship hull and sea ice in an embodiment of the present invention;

[0043] Figure 5 This is a simulation diagram of sea ice destruction caused by the interaction between the ship hull and sea ice in an embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0045] Example

[0046] Reference Figure 1 This invention provides a method for generating a wide-area sea ice dynamic destruction model, the steps of which include:

[0047] S1. Determine the geometric dimensions and physical parameters of the sea ice region, including its length L, width B, thickness H, elastic modulus E, Poisson's ratio ν, density ρ, and fracture toughness K. I .

[0048] S2. The initial fracture region of sea ice is pre-defined. This initial fracture region is the area where sea ice fractures and cracks occur, with a length of L1, a width of B1, and a thickness of H1. A fracture region calculation model is established using conventional state-based near-field dynamics methods, i.e., the fracture region is discretized into particle points to obtain the initial coordinates (x, y, y) of different particle points. i y i , z i (0)).

[0049] S3. Use the nonlinear finite element method to establish a calculation model for the non-fractured region of sea ice, that is, use the nonlinear finite element method to discretize the non-fractured region in the grid space.

[0050] Sea ice models established using conventional state-based peri-field dynamics methods and nonlinear finite element methods, such as... Figure 2 and Figure 3 As shown.

[0051] S4. A step-by-step solution strategy is adopted, with different time steps for the sea ice fracture region and the non-fracture region, and the number of time iteration steps for updating the coupling interface is set.

[0052] Due to differences in solution strategies and mesh sizes, the numerical values ​​of the time iteration steps may differ between the fractured and non-fractured regions. The formulas for the time step sizes of the sea ice fractured and non-fractured regions are shown below:

[0053]

[0054] In the formula, Δt FEM Indicates the time step of the non-fractured region; Δt PD The time step represents the fracture region; l represents the characteristic length of the mesh element; E represents the elastic modulus of sea ice; ν represents the Poisson's ratio of sea ice; a and d represent sea ice-related parameters in the peridynamics method; δ represents the neighborhood radius in the peridynamics method; ξ lk V represents the initial distance between matter point l and matter point k. j ξ represents the volume of substance point j. lj The initial distance ξ between matter point l and matter point j kj This represents the initial distance between matter point k and matter point j.

[0055] For the fractured region, information exchange occurs once between the fractured and non-fractured regions after every m1 iterations, as shown in the formula:

[0056] m1Δt PD =m2Δt FEM ;

[0057] In the formula, m2 represents the number of time iteration steps in the non-fracture region; m1 represents the number of time iteration steps in the fracture region; m1 and m2 are the smallest integers that can be taken.

[0058] S5. Determine the overall time increment step, set the coupling interface conditions between the fractured and non-fractured regions, and perform iterative calculations. Through the bidirectional coupling of physical information between the fractured and non-fractured regions, the smooth and coordinated transition of deformation displacement in the coupled boundary region is ensured.

[0059] Since the time step size of the non-fracture region is generally larger than that of the fracture region, the overall increment step is equal to the time step size of the non-fracture region, as shown in the formula:

[0060] Δt total =Δt FEM ;

[0061] In the formula, Δt total This indicates the total increment step.

[0062] The initial time iteration step k = 1 is set. The coupling interface conditions between the fractured and non-fractured regions are set. For the coupling interface, it is both a finite element mesh node and a meshless particle point. Its motion control equations are obtained by conventional state-based near-field dynamics methods, and the formula is:

[0063]

[0064] In the formula, ρ represents the density of the substance point k; V represents the acceleration of matter point i at the nth time iteration step; m represents the number of neighboring particles of matter point i; V j Represents the volume of substance point j; This represents the external force density experienced by material point i at the nth time step; This represents the displacement of matter point j at the nth time step. The force density represents the interaction force between matter points i and j; x j Let x represent the initial position of matter point j. i This represents the initial position of substance point i;

[0065] The coupling interface transfers the obtained particle velocity and displacement to the finite element mesh nodes that share the same spatial location, as shown in the formula:

[0066]

[0067] In the formula, This represents the displacement of material point i at the nth iteration step; This represents the displacement of node i at the nth iteration step; This represents the velocity of node i at the nth iteration step; This represents the velocity of material point i at the nth iteration step.

[0068] The motion information of particle points at the coupling interface is obtained and used as the moving boundary of the non-fractured region. All mesh node information in the non-fractured region is updated, and the mesh nodes satisfy the finite element structural dynamic equilibrium equations, as follows:

[0069]

[0070] In the formula, M and C represent the mass matrix and damping matrix of the finite element structure, respectively, and F int F ext This represents the resultant internal and external forces acting on the structure; 'a' represents the nodal displacement. Indicates the node speed.

[0071] After the mesh nodes are calculated, the mesh nodes within the neighborhood of the coupled boundary particle points are used as the particle points within that neighborhood. This enables the non-fractured region to control the fractured region. If the mesh size is larger than the particle point radius, the motion and position information of the mesh nodes are equivalently allocated to the particle points using the principle of shape function space allocation.

[0072]

[0073] In the formula, N represents the displacement of a particle within a grid node at the (n+1)th iteration step; i Represents a grid shape function.

[0074] S6. Considering the interaction between marine structures and sea ice, determine the contact between the structure and sea ice based on the surface shape of the marine structure, and calculate the ice load on the structure.

[0075] S7. Calculate ice force pulsations, sea ice deformation and failure fields, and output sea ice deformation contour maps and dynamic failure contour maps.

[0076] S8. Determine whether the sea ice crack extends into the non-fracture region. If so, delete the finite element elements in the crack tip region.

[0077] The damage level of particle points sharing the same spatial location with mesh nodes in the interface is used to determine whether sea ice cracks have extended into the non-fracture region. The formula is as follows:

[0078] s ij <s0;

[0079]

[0080] In the formula, s ij si represents the relative deformation length between boundary layer particle i and its neighboring particle j; s0 represents the limiting elongation of the particle point pair, which is related to the fracture mechanics properties of the material.

[0081] S9. Determine if the number of time iteration steps has reached the maximum increment step. If yes, stop the calculation; otherwise, repeat steps S4-S8 until the number of time iteration steps reaches the maximum increment step.

[0082] This invention can directly predict sea ice deformation and dynamic damage cloud maps caused by the interaction between sea ice and structures over a wide area. Figure 4 Micro-deformation cloud maps of the ice mass interacting with the ship's hull over a wide area are presented. (a) shows the sea ice-ship interaction model established using the method of this invention, with a computation time of 15.5 hours; (b) shows the sea ice-ship interaction model established using the nonlinear finite element method, with a computation time of 41.1 hours. Figure 5 Wide-area sea ice-ship interaction ice destruction cloud maps are presented, where (a) is the sea ice-ship interaction ice destruction cloud map established using the method of this invention, and (b) is the sea ice-ship interaction ice destruction cloud map established using the nonlinear finite element method. As can be seen from the figure, the deformation coordination transition between the non-fracture region and the fracture region of the ice layer coupling boundary is very smooth, and the periodic destruction phenomenon of the ice layer is well simulated, verifying the effectiveness of this invention.

[0083] Therefore, the present invention adopts the above-mentioned method for generating a wide-area sea ice dynamic failure model, and uses the OSBPD-NLFEM hybrid algorithm to construct a wide-area sea ice environment field. By pre-setting the sea ice fracture region and using the OSBPD method adapted to failure problems, the initiation and propagation of ice cracks are simulated, which greatly reduces the computation time consumption and improves the deformation transition ability at the coupling boundary, thereby improving the coupling effect.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for generating a wide-area sea ice dynamic failure model, characterized by the following steps: include: S1. Determine the geometric dimensions and physical parameters of the sea ice area; S2. Initially define the initial fracture zone of sea ice and establish a calculation model for the fracture zone; S3. Establish a calculation model for the non-fractured region of sea ice; S4. A step-by-step solution strategy is adopted, using different time steps for the sea ice fracture region and the non-fracture region, and setting the number of time iteration steps for the coupling interface update, specifically including: The time step for both the sea ice fracture region and the non-fracture region is set using the following formula: ； ； In the formula, Indicates the time step of the non-fractured region; Indicates the time step of the fracture region. l Indicates the characteristic length of a grid cell; E This represents the elastic modulus of sea ice. Poisson's ratio represents sea ice; a , d Representation of parameters related to sea ice in near-field dynamics methods; This represents the neighborhood radius in near-field dynamics methods. Representing a point of matter l and matter points k The initial distance between them Representing a point of matter j volume, Matter Point l and matter points j The initial distance between them Representing a point of matter k and matter points j The initial distance between them; Set the time iteration step for updating the coupling interface; for the fracture region, every interval... m After one iteration, an information exchange occurs between the non-fractured regions, as shown in the formula: ； In the formula, m 2 indicates the number of time iteration steps in the non-fracture region; m 1 indicates the number of time iteration steps in the fracture region; m 1 and m 2 is the smallest integer that can be obtained; S5. Determine the overall time increment step, set the coupling interface conditions between the fractured and non-fractured regions, and perform iterative calculations; S6. Determine the contact between the structure and sea ice based on the surface shape of the marine structure, and calculate the ice load on the structure. S7. Calculate ice force pulsation, sea ice deformation and failure field, and output sea ice deformation cloud map and dynamic failure cloud map; S8. Determine whether the sea ice crack extends into the non-fracture region. If so, delete the finite element elements in the crack tip region. S9. Determine if the number of time iteration steps has reached the maximum increment step. If yes, stop the calculation; otherwise, repeat steps S4-S8 until the number of time iteration steps reaches the maximum increment step.

2. The method for generating a wide-area sea ice dynamic destruction model according to claim 1, characterized in that: The geometric dimensions and physical parameters of the sea ice area in step S1 include the length of the sea ice area. L ,width B ,thickness H The elastic modulus of sea ice E Poisson's ratio ,density ρ and fracture toughness K I .

3. The method for generating a wide-area sea ice dynamic destruction model according to claim 1, characterized in that: In step S2, the fracture and crack occurrence areas of sea ice are initially predefined, wherein the length of the fracture and crack occurrence areas is... L 1. Width is B 1. Thickness is H 1. The region where the event occurred was discretized using conventional state-based near-field dynamics methods to obtain the initial coordinates of different particle points. x i , y i , z i (0)).

4. The method for generating a wide-area sea ice dynamic destruction model according to claim 3, characterized in that: In step S3, the nonlinear finite element method is used to discretize the non-fractured region in a mesh space.

5. The method for generating a wide-area sea ice dynamic destruction model according to claim 1, characterized in that, Step S5 specifically includes: Determine the total time increment step and set the initial number of time iteration steps. k =1; Set the coupling interface conditions between the fractured and non-fractured regions. For the coupling interface, it is both a finite element mesh node and a meshless particle point. Its motion control equation is obtained by conventional state-based near-field dynamics method. The coupling interface transmits the obtained particle velocity and displacement to the finite element mesh nodes that share the same spatial location with it. The motion information of the particle points at the coupling interface is obtained and used as the moving boundary of the non-fractured region. The information of all mesh nodes in the non-fractured region is updated, and the mesh nodes satisfy the dynamic equilibrium equation of the finite element structure. After the mesh nodes are calculated, the mesh nodes within the neighborhood of the coupled boundary particle points are used as the particle points within the neighborhood, so as to realize the control of the fractured area by the non-fractured area. If the mesh size is larger than the particle point size radius, the principle of shape function space allocation is used to equivalently allocate the motion and position information of the mesh nodes to the particle points.

6. The method for generating a wide-area sea ice dynamic destruction model according to claim 5, characterized in that, In step S8, the damage level of particle points sharing the same spatial location with mesh nodes in the interface is used to determine whether sea ice cracks have extended into the non-fracture region. The formula is as follows: ； ； In the formula, Represents boundary layer particles i Its neighboring particles j The relative deformation length; This represents the limiting elongation of a particle point pair.

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