Simulation calculation method for successive collapse of hull structure in waves

Abstract

According to the simulation calculation method for successive collapse of the hull structure in the waves, a set of load-structure integrated numerical analysis method is summarized, and the method is different from a method for calculating an external load and structural strength separately in a traditional method. On one hand, the hull ultimate strength calculation precision is improved, and on the other hand, the hull structure successive collapse characteristics are more truly presented. Firstly, a theoretical basis and a calculation process of the method are introduced; then, in order to verify the feasibility and rationality of the method, a series of simulation analysis of successive collapse of the hull structure in waves is carried out according to the method, and the ultimate strength of the hull structure and the characteristics of stress distribution, deformation and the like in the successive collapse process are obtained. The result shows that the load-structure integrated numerical analysis method is reasonable and feasible, can be used as a simulation calculation method for successive collapse of ship body structures of various ships, and has important application value.

Description

Technical Field

[0001] The present invention relates to the technical field of simulation of collapse and destruction of a hull structure, and in particular to a simulation calculation method for successive collapse of a hull structure in waves. Background Art

[0002] Traditional hull structural analysis often uses a separate calculation method, that is, the fluid dynamic load is calculated independently first, and then applied to the structural analysis model as an external input. However, this method ignores the interaction between the fluid and the structure, which may lead to inaccurate calculation results. In order to overcome this limitation, the fluid-structure integrated numerical analysis method has gradually become a research hotspot in recent years. This method can simultaneously consider the dynamic response of the fluid and the structure, thereby more accurately simulating the behavior of the hull structure in waves;

[0003] Therefore, developing a simulation calculation method for the successive collapse of hull structures in waves is of great significance for improving the safety and reliability of ship design. This method combines the numerical analysis method of fluid-structure integration, the high-precision hull structure model, the linear frequency domain hydrodynamic calculation model based on three-dimensional potential flow theory, the load equivalent conversion method with smaller error, and the nonlinear finite element analysis based on the arc length method, which can more accurately predict the ultimate strength and successive collapse process of the hull structure in waves. Summary of the invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies in the prior art and provide a method for solving the external fluid induced loads and the internal structural response of the hull based on three-dimensional potential flow theory and nonlinear finite element analysis theory, and to construct a "two-way" channel for "structure-fluid" data transmission between the external fluid loads and the hull structural response, thereby forming a complete set of small unmanned boat vector control devices.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution: a simulation calculation method for the successive collapse of a hull structure in waves, the steps of which are as follows:

[0006] (1) Using the fluid-structure integrated numerical analysis method, a three-dimensional finite element model of the hull structure is first established. According to the size parameters of the experimental model, S4R and S3R units are used in MSC / PATRAN, and grids of different sizes are divided as needed;

[0007] (2) A three-dimensional hydrodynamic calculation model was established. The linear frequency domain method based on three-dimensional potential flow theory was used to calculate the wave-induced loads on the hull structure in waves in HYDROSTAR, including static water pressure, dynamic water pressure and inertial force.

[0008] (3) Using a load equivalent conversion method with smaller error, the wave-induced loads are converted into equivalent nodal forces and whole-ship acceleration in HOMER. The hydrostatic pressure and hydrodynamic pressure are converted separately, and the quadratic reintegration method is used to ensure that the static / dynamic water pressure in the hydrodynamic model is equivalently converted to the structural model.

[0009] (4) Prepare the ABAQUS calculation input file together with the load, structure and boundary conditions, and submit it to ABAQUS for nonlinear finite element analysis based on the arc length method to track the ultimate strength and successive collapse process of the hull structure.

[0010] The technical problem to be solved by the present invention can also be achieved by the following technical solutions. In the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, when establishing a three-dimensional finite element model of the hull structure, the middle frame structure adopts a square grid with a side length of 10 mm, and the grid side length at the connection between the middle frame and the front and rear frames of the intermediate sheet gradually increases from 10 mm to 50 mm. The remaining structures all adopt a square grid with a side length of 50 mm. The waterline is divided into units to ensure that the waterline surface is the unit edge line, which is convenient for hydrodynamic calculation, and the units and nodes are renumbered to ensure the accuracy of load conversion.

[0011] The technical problem to be solved by the present invention can also be achieved by the following technical solutions. In the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, when establishing a hydrodynamic calculation model, a coarser hydrodynamic grid is re-divided according to the hull draft, and the hull outer plate grid is extracted, including the bottom plate, side plate and bow and stern cover plate, and the direction of the outer plate unit, the hydrodynamic grid and the outer plate grid is adjusted from the inside of the structure to the outside, and output as "DAT" and "HS0" files for subsequent calculations.

[0012] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, the three-dimensional linear frequency domain method in step (2) has two basic assumptions:

[0013] The first assumption is that the fluid is incompressible and the surface tension of the fluid is not considered;

[0014] The second assumption is that the fluid motion is irrotational, that is, there is velocity potential, and the velocity vector of the fluid motion can be represented by the fluid particle gradient;

[0015] Therefore, solving the velocity potential of the flow field is the key to calculating the wave-induced loads. The velocity potential can be expressed as:

[0016]

[0017] in:

[0018] O-XYZ is a fixed coordinate system in space, with the Z axis pointing vertically upward and the origin O located on the undisturbed water surface; o-xyz is a coordinate system that moves with the ship, with the z axis pointing vertically upward and the origin o located on the undisturbed water surface; Φ(x, y, z, t) is the velocity potential; [-U X +Φ S (x,y,z)] is a steady potential; Re{φ T (x,y,z)e iωt} is the unsteady potential; φ I (x, y, z) is the incident potential; φ D (x, y, z) is the diffraction potential; φ R (x, y, z) is the radiation potential; p = p(x, y, z, t) is the pressure at a point in the flow field; (u, v, w) is the velocity component of the point in the flow field. The velocity potential V(x, y, z, t) at the point can be expressed as:

[0019]

[0020] p0 is the pressure change caused by velocity potential. The pressure at any point in the flow field is obtained by the Bernoulli equation:

[0021]

[0022] From the Laplace equation we can get:

[0023]

[0024] The fluid domain must also satisfy the bottom, free liquid surface, instantaneous wet surface of the hull and remote control surface, as follows:

[0025]

[0026] By combining differential equations and boundary conditions, we can solve the radiation potential φ R or φ j and the diffraction potential φ D Or φ7.

[0027] The technical problem to be solved by the present invention can also be achieved by the following technical solution. In the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, in step (2), the calculation process of the wave load is:

[0028] (1) When constructing the hydrodynamic calculation model, according to the hull draft under different ballasts, the structure below the waterline is extracted and re-meshed in PATRAN, and the hull mesh and hydrodynamic mesh are extracted;

[0029] (2) Determine the amplitude response operator of the midship section bending moment, perform the response analysis of the structural midship section bending moment at unit wave height and different frequencies, and determine the frequency range of the maximum midship section bending moment;

[0030] (3) Determine a series of simulation conditions, select the frequency determined in process (2), and choose 1 / 200 of the ship length as the wave height increment to form a series of simulation parameters;

[0031] (4) Divide the calculation time, divide the wave period into equal intervals, and obtain multiple calculation times, that is, the wave period of each working condition is 2.1s, the time interval is 0.105s, and a total of 21 times;

[0032] (5) Perform hydrodynamic calculations and carry out simulation calculations in HYDROSTAR to obtain the wave-induced loads at each moment.

[0033] The technical problem to be solved by the present invention can also be achieved by the following technical solutions: in the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, the transformation process of the wave-induced load includes re-integrating to obtain the finite element grid node pressure instead of interpolation, and selecting appropriate methods to convert different pressure components respectively, and the overall acceleration of the hull is obtained by integrating the structural finite element grid instead of the hydrodynamic calculation grid to reduce the calculation error;

[0034] The calculation process of dynamic water pressure is as follows:

[0035] The calculation of dynamic water pressure is re-integrated in the calculation area, rather than using interpolation functions. By analyzing the model information, the program can obtain the coordinates of the points to be calculated, and then integrate to obtain the corresponding potential:

[0036]

[0037] Where: G is Green's function, x s =(x s ,y s ,z s ) is the structural point, x h =(x h ,y h ,z h ) is the hydrodynamic point, σ is the source strength;

[0038] exist superior;

[0039] in, is the hydrodynamic grid at the wet surface, V n represents the hull boundary condition;

[0040] In the case of no speed, because the water pressure is proportional to the velocity potential, and the velocity potential is continuous on the entire wet surface, the linear load analysis is more accurate. When all pressure components are equivalently converted to the structural grid, the load used for structural nonlinear finite element analysis can be obtained by integrating the structural grid, that is:

[0041]

[0042] Where: the superscript “s” represents the corresponding load item on the structural grid;

[0043] The calculation process of hydrostatic pressure is as follows:

[0044] To solve the hydrostatic recovery matrix, first calculate the dynamic hydrostatic pressure change value P hs ,Right now,

[0045] P hs =-ρg[η3+η4(YY G )-η5(XX G )];

[0046] For ease of expression, the dynamic hydrostatic pressure change value P hs Expressed more concisely:

[0047]

[0048] Among them: P1 hs =0,

[0049]

[0050] Using this representation, the first part of the hydrostatic response matrix can be expressed as:

[0051]

[0052] Among them: n1, n2, n3 represent n x ,n y ,n z , that is, the normal vectors in three directions; n4, n5, n6 represent (RR G )∧n;

[0053] The complete hydrostatic reversion matrix also needs to consider the change of the coordinate system. An additional item needs to be added to consider the change of the normal direction of the coordinate system. In the fixed coordinate system, the change of the coordinate system can be reflected by changing the normal vector, but the structural response analysis is calculated in the ship-borne coordinate system, in which the normal vector does not change. In the ship-borne coordinate system, the change of the normal vector is equivalent to the change of the gravitational acceleration, so it can be written as:

[0054] F g =-mgΩ^k=[C] g {η};

[0055] Where: Ω represents {η4,η5,η6};

[0056] Get the total reply matrix:

[0057] [C] s =[C] P +[C] g .

[0058] The technical problem to be solved by the present invention can also be achieved by the following technical solutions: the above-mentioned simulation calculation method for the successive collapse of the hull structure in waves, the arc length method is used in the nonlinear finite element analysis to better track the extreme value of the structure, and the calculation input file of ABAQUS of the load, the structural model information, and the calculation method command flow are combined to write a complete calculation input file of ABAQUS, and submit it to ABAQUS / COMMAND for calculation;

[0059] The technical problem to be solved by the present invention can also be achieved by the following technical scheme. The above-mentioned simulation calculation method for the successive collapse of the hull structure in waves is suitable for evaluating the ultimate strength and collapse behavior of the hull structure in waves. The ultimate strength of the hull structure and the stress distribution and deformation characteristics during the successive collapse are obtained through simulation analysis.

[0060] Compared with the prior art, the beneficial technical effects of the present invention are:

[0061] (1) Improved accuracy and optimized computational efficiency: The present invention adopts a fluid-structure integrated numerical analysis method, which effectively considers the interaction between fluid-induced loads and hull structural responses, thereby greatly improving the computational accuracy.

[0062] Through reasonable grid division and load conversion methods, the accuracy of the calculation results is guaranteed, and the calculation time cost and performance requirements are effectively controlled, making this method highly operational in practical applications.

[0063] (2) Complete numerical simulation research system:

[0064] The present invention not only establishes a solution method for external fluid-induced loads and internal structural responses of the hull, but also constructs a "two-way" channel for "structure-fluid" data transmission between the two, forming a complete numerical simulation research method for analyzing the collapse characteristics of hull structures in waves.

[0065] This method can comprehensively and accurately simulate the dynamic collapse process of the hull structure in waves, providing strong technical support for the design and safety assessment of the hull structure.

[0066] (3) In-depth load transformation and precise structural response analysis:

[0067] In the process of transforming wave-induced loads, the present invention adopts a method of obtaining finite element grid node pressure by reintegration instead of interpolation, which effectively reduces calculation errors.

[0068] At the same time, different pressure components are converted separately using appropriate methods, and the overall acceleration of the hull is also integrated on the structural finite element grid, further improving the accuracy of load conversion.

[0069] Combined with the nonlinear finite element analysis of the arc length method, the present invention can better track the extreme values ​​of the structure and accurately evaluate the ultimate strength of the hull structure and the stress distribution and deformation characteristics during the successive collapse process.

[0070] (4) Broad application prospects and practical value:

[0071] The method of the present invention is not only suitable for evaluating the ultimate strength and collapse behavior of the hull structure in waves, but also can provide an important reference for the fields of ship design, structural optimization, safety assessment, etc.

[0072] The ultimate strength of the hull structure and the stress distribution and deformation characteristics during the successive collapse obtained through simulation analysis can provide strong data support for the manufacture, maintenance and improvement of ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a flow chart of the simulation calculation method of the successive collapse of the hull structure in waves of the present invention;

[0074] Figure 2 This is a finite element model diagram of an exemplary hull structure of the present invention;

[0075] Figure 3 The bending moment-time diagram of the midship section of the present invention;

[0076] Figure 4 This is the cross-sectional bending moment distribution diagram of the present invention at time U8;

[0077] Figure 5 This is the longitudinal stress distribution diagram of S4 and U8 of the present invention;

[0078] Figure 6 This is the longitudinal stress distribution diagram of S4 and U8 along the bottom of the ship according to the present invention;

[0079] Figure 7 It is the deformation diagram of the midship section in the S4 and U8 working conditions of the present invention. DETAILED DESCRIPTION

[0080] The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so as to facilitate further understanding of the present invention by those skilled in the art, and do not constitute a limitation on the rights thereof.

[0081] Example 1, reference Figure 1-7 , a simulation calculation method for the successive collapse of a hull structure in waves, the steps are as follows:

[0082] (1) Using the fluid-structure integrated numerical analysis method, a three-dimensional finite element model of the hull structure is first established. According to the size parameters of the experimental model, S4R and S3R units are used in MSC / PATRAN, and grids of different sizes are divided as needed;

[0083] (2) A three-dimensional hydrodynamic calculation model was established. The linear frequency domain method based on three-dimensional potential flow theory was used to calculate the wave-induced loads on the hull structure in waves in HYDROSTAR, including static water pressure, dynamic water pressure and inertial force.

[0084] (3) Using a load equivalent conversion method with smaller error, the wave-induced loads are converted into equivalent nodal forces and whole-ship acceleration in HOMER. The hydrostatic pressure and hydrodynamic pressure are converted separately, and the quadratic reintegration method is used to ensure that the static / dynamic water pressure in the hydrodynamic model is equivalently converted to the structural model.

[0085] (4) Prepare the ABAQUS calculation input file together with the loads, structures and boundary conditions, and submit it to ABAQUS for nonlinear finite element analysis based on the arc length method to track the ultimate strength and successive collapse process of the hull structure;

[0086] When establishing the three-dimensional finite element model of the hull structure, the middle frame structure uses a square grid with a side length of 10mm. The grid side length of the connection between the middle frame and the front and rear frames of the middle sheet gradually increases from 10mm to 50mm. The other structures all use a square grid with a side length of 50mm. The waterline is divided into units to ensure that the waterline surface is the unit edge line for easy hydrodynamic calculation, and the units and nodes are renumbered to ensure the accuracy of load conversion.

[0087] When establishing the hydrodynamic calculation model, the coarser hydrodynamic grid is re-divided according to the hull draft, and the hull outer plate grid is extracted, including the bottom plate, side plate and bow and stern cover plate. The direction of the outer plate unit, hydrodynamic grid and outer plate grid is adjusted from the inside of the structure to the outside, and output as "DAT" and "HS0" files for subsequent calculations;

[0088] In the above-mentioned simulation calculation method for the successive collapse of a hull structure in waves, the three-dimensional linear frequency domain method in step (2) has two basic assumptions:

[0089] The first assumption is that the fluid is incompressible and the surface tension of the fluid is not considered;

[0090] The second assumption is that the fluid motion is irrotational, that is, there is velocity potential, and the velocity vector of the fluid motion can be represented by the fluid particle gradient;

[0091] Therefore, solving the velocity potential of the flow field is the key to calculating the wave-induced loads. The velocity potential can be expressed as:

[0092]

[0093] in:

[0094] O-XYZ is a fixed coordinate system in space, with the Z axis pointing vertically upward and the origin O located on the undisturbed water surface; o-xyz is a coordinate system that moves with the ship, with the z axis pointing vertically upward and the origin o located on the undisturbed water surface; Φ(x, y, z, t) is the velocity potential; [-U X +Φ S (x,y,z)] is a steady potential; Re{φ T (x,y,z)e iωt} is the unsteady potential; φ I (x, y, z) is the incident potential; φ D (x, y, z) is the diffraction potential; φ R (x, y, z) is the radiation potential; p = p(x, y, z, t) is the pressure at a point in the flow field; (u, v, w) is the velocity component of the point in the flow field. The velocity potential V(x, y, z, t) at the point can be expressed as:

[0095]

[0096] p0 is the pressure change caused by velocity potential. The pressure at any point in the flow field is obtained by the Bernoulli equation:

[0097]

[0098] From the Laplace equation we can get:

[0099]

[0100] The fluid domain must also satisfy the bottom, free liquid surface, instantaneous wet surface of the hull and remote control surface, as follows:

[0101]

[0102] By combining differential equations and boundary conditions, we can solve the radiation potential φ R or φ j and the diffraction potential φ D or φ7;

[0103] In addition, in step (2), the calculation process of wave load is:

[0104] (1) When constructing the hydrodynamic calculation model, according to the hull draft under different ballasts, the structure below the waterline is extracted and re-meshed in PATRAN, and the hull mesh and hydrodynamic mesh are extracted;

[0105] (2) Determine the amplitude response operator of the midship section bending moment, perform the response analysis of the structural midship section bending moment at unit wave height and different frequencies, and determine the frequency range of the maximum midship section bending moment;

[0106] (3) Determine a series of simulation conditions, select the frequency determined in process (2), and choose 1 / 200 of the ship length as the wave height increment to form a series of simulation parameters;

[0107] (4) Divide the calculation time, divide the wave period into equal intervals, and obtain multiple calculation times, that is, the wave period of each working condition is 2.1s, the time interval is 0.105s, and a total of 21 times;

[0108] (5) Perform hydrodynamic calculations and conduct simulation calculations in HYDROSTAR to obtain the wave-induced loads at each moment;

[0109] In addition, the transformation process of wave-induced loads includes reintegration to obtain the finite element grid node pressure instead of interpolation, and the selection of appropriate methods to convert different pressure components separately. The overall acceleration of the hull is obtained by integration on the structural finite element grid instead of the hydrodynamic calculation grid to reduce the calculation error.

[0110] The calculation process of dynamic water pressure is as follows:

[0111] The calculation of dynamic water pressure is re-integrated in the calculation area, rather than using interpolation functions. By analyzing the model information, the program can obtain the coordinates of the points to be calculated, and then integrate to obtain the corresponding potential:

[0112]

[0113] Where: G is Green's function, x s =(x s ,y s ,z s ) is the structural point, x h =(x h ,y h ,z h ) is the hydrodynamic point, σ is the source strength;

[0114] exist superior;

[0115] in, is the hydrodynamic grid at the wet surface, V n represents the hull boundary condition;

[0116] In the case of no speed, because the water pressure is proportional to the velocity potential, and the velocity potential is continuous on the entire wet surface, the linear load analysis is more accurate. When all pressure components are equivalently converted to the structural grid, the load used for structural nonlinear finite element analysis can be obtained by integrating the structural grid, that is:

[0117]

[0118] Where: the superscript “s” represents the corresponding load item on the structural grid;

[0119] The calculation process of hydrostatic pressure is as follows:

[0120] To solve the hydrostatic recovery matrix, first calculate the dynamic hydrostatic pressure change value P hs ,Right now,

[0121] P hs =-ρg[η3+η4(YY G )-η5(XX G )];

[0122] For ease of expression, the dynamic hydrostatic pressure change value P hs Expressed more concisely:

[0123]

[0124] Among them: P1 hs =0,

[0125]

[0126] Using this representation, the first part of the hydrostatic response matrix can be expressed as:

[0127]

[0128] Among them: n1, n2, n3 represent n x ,n y ,n z , that is, the normal vectors in three directions; n4, n5, n6 represent (RR G )^n;

[0129] The complete hydrostatic reversion matrix also needs to consider the change of the coordinate system. An additional item needs to be added to consider the change of the normal direction of the coordinate system. In the fixed coordinate system, the change of the coordinate system can be reflected by changing the normal vector, but the structural response analysis is calculated in the ship-borne coordinate system, in which the normal vector does not change. In the ship-borne coordinate system, the change of the normal vector is equivalent to the change of the gravitational acceleration, so it can be written as:

[0130] F g=-mgΩ∧k=[C] g {η};

[0131] Where: Ω represents {η4,η5,η6};

[0132] Get the total reply matrix:

[0133] [C] s =[C] P +[C] g ;

[0134] The arc length method is used in nonlinear finite element analysis to better track the extreme values ​​of the structure. The complete ABAQUS calculation input file is compiled by combining the ABAQUS calculation input file of the load, the structural model information, and the calculation method command flow, and then submitted to ABAQUS / COMMAND for calculation.

[0135] This method is suitable for evaluating the ultimate strength and collapse behavior of the hull structure in waves. The ultimate strength of the hull structure and the stress distribution and deformation characteristics during the successive collapse process are obtained through simulation analysis.

[0136] a) Bending moment of midship section:

[0137] The bending moment of the midship section in the collapse condition is as follows: Figure 3 As shown in the figure, under the action of wave loads with the same parameters, the structure can continue to bear the load when the ballast at the bow and stern is 230kg; when the ballast at the bow and stern is 280kg, as the wave crest gradually moves to the midship area, at the 8th moment, the structure reaches the limit state, which is calculated as U8; at the 9th moment, the structure collapses and is destroyed rapidly. At this time, the structure undergoes a large deformation, and the wave-induced load on the hull will also change, and the data will be distorted, so the subsequent moments are no longer calculated; the U8 section bending moment is the limit bending moment of the hull structure, 4.279×10 6 N×mm, the bending moment is distributed along the length of the ship as Figure 4 As shown;

[0138] b) Stress distribution and structural deformation of the midship section:

[0139] In order to better reflect the stress distribution and structural deformation characteristics of the midship section, the same ballast water condition (S4) is compared with the ultimate collapse moment; the longitudinal stress distribution of the S4 and U8 side structures along the mold depth is as follows: Figure 5 As shown in the figure, the longitudinal stress of the bottom plate is distributed along the width of the ship as Figure 6 As shown, the structural deformation is Figure 7 As shown;

[0140] The stress distribution on the side of the ship is as follows: Figure 5As shown in the figure, the neutral axis position of U8 is Z=150mm, the longitudinal stress increases linearly from 150 to 250mm, and remains basically unchanged after reaching the yield value from 250 to 300mm; due to the adoption of the VON MISES yield criterion, the uniaxial stress can exceed 40MPa in a small range; at the depth of 0mm, the longitudinal stress reaches the yield strength value, and in the range of 150 to 75mm, the longitudinal stress increases slowly, and in the range of 0 to 75mm, the longitudinal stress increases rapidly;

[0141] The stress distribution on the bottom of the ship is as follows: Figure 6 As shown in the figure, the longitudinal stress of U8 is distributed in a symmetrical "J" shape. The bottom plate adjacent to the center longitudinal bone should be compressed, but the arching deformation in the middle changes the original stress distribution state, which is in a tensile state with positive stress. The bottom plate close to the side cannot produce a large deformation due to the restriction of the side, so the longitudinal stress remains negative, resulting in a "J"-shaped distribution of the longitudinal stress of the bottom under the limit state.

[0142] The midship section deformation is caused by Figure 7 It can be seen that compared with S4, the structural deformation of the U8 midship section is very obvious. The plate at the bottom longitudinal of S4 is obviously concave, which shows that the bottom longitudinal has a certain inhibitory effect on the arch deformation of the plate. However, due to the large-area yielding of the U8 bottom longitudinal, it can no longer limit the deformation of the bottom plate under the external water pressure and internal bending moment. Therefore, the bottom longitudinal and the plate are generally semicircular. The deformation of the U8 midship section also shows the significant influence of external water pressure on the overall and local deformation of the structure.

Claims

1. A simulation calculation method for the successive collapse of a hull structure in waves, characterized in that: The steps are as follows: (1) Using the fluid-structure integrated numerical analysis method, a three-dimensional finite element model of the hull structure is first established. According to the size parameters of the experimental model, S4R and S3R units are used in MSC / PATRAN, and grids of different sizes are divided as needed; (2) A three-dimensional hydrodynamic finite element model was established, and the wave-induced loads on the hull structure in waves, including hydrostatic pressure, hydrodynamic pressure, and inertial force, were calculated in HYDROSTAR using a linear frequency domain method based on three-dimensional potential flow theory. (3) Using a load equivalent conversion method with smaller error, the wave-induced loads are converted into equivalent nodal forces and whole-ship acceleration in HOMER. The hydrostatic pressure and hydrodynamic pressure are converted separately, and the quadratic reintegration method is used to ensure that the static / dynamic water pressure in the hydrodynamic model is equivalently converted to the structural model. (4) Prepare the ABAQUS calculation input file together with the load, structure and boundary conditions, and submit it to ABAQUS for nonlinear finite element analysis based on the arc length method to track the ultimate strength and successive collapse process of the hull structure.

2. The method for simulating the successive collapse of a hull structure in waves according to claim 1, characterized in that: When establishing the three-dimensional finite element model of the hull structure, the middle frame structure adopts a square grid with a side length of 10mm. The grid side length of the connection between the middle frame and the front and rear frames of the middle sheet gradually increases from 10mm to 50mm. The remaining structures all use a square grid with a side length of 50mm. The waterline is divided into units to ensure that the waterline surface is the unit edge line for easy hydrodynamic calculation. The units and nodes are renumbered to ensure the accuracy of load conversion.

3. The method for simulating the successive collapse of a hull structure in waves according to claim 1, characterized in that: When establishing the hydrodynamic calculation model, the hydrodynamic grid is re-divided according to the hull draft, and the hull outer plate grid is extracted, including the bottom plate, side plate and bow and stern cover plate. The direction of the outer plate unit, hydrodynamic grid and outer plate grid is adjusted from the inside of the structure to the outside, and output as "DAT" and "HS0" files for subsequent calculations.

4. The simulation calculation method for the successive collapse of a hull structure in waves according to claim 1 is characterized in that: The three-dimensional linear frequency domain method in step (2) has two basic assumptions: The first assumption is that the fluid is incompressible and the surface tension of the fluid is not considered; The second assumption is that the fluid motion is irrotational, that is, there is velocity potential, and the velocity vector of the fluid motion can be represented by the fluid particle gradient; Therefore, solving the velocity potential of the flow field is the key to calculating the wave-induced loads. The velocity potential can be expressed as: in: O-XYZ is a fixed coordinate system in space, with the Z axis pointing vertically upward and the origin O located on the undisturbed water surface; o-xyz is a coordinate system that moves with the ship, with the z axis pointing vertically upward and the origin o located on the undisturbed water surface; Φ(x, y, z, t) is the velocity potential; [-U X +Φ S (x,y,z)] is a steady potential; Re{φ T (x,y,z)e iωt } is the unsteady potential; φ I (x, y, z) is the incident potential; φ D (x, y, z) is the diffraction potential; φ R (x, y, z) is the radiation potential; p = p(x, y, z, t) is the pressure at a point in the flow field; (u, v, w) is the velocity component of the point in the flow field. The velocity potential V(x, y, z, t) at the point can be expressed as: V≡(u,v,w)=▽Φ; p0 is the pressure change caused by velocity potential. The pressure at any point in the flow field is obtained by the Bernoulli equation: From the Laplace equation we can get: The fluid domain must also satisfy the bottom, free liquid surface, instantaneous wet surface of the hull and remote control surface, as follows: By combining differential equations and boundary conditions, we can solve the radiation potential φ R or φ j and the diffraction potential φ D Or φ7.

5. The method for simulating the successive collapse of a hull structure in waves according to claim 1, characterized in that: In step (2), the calculation process of wave load is: (1) When constructing the hydrodynamic calculation model, according to the hull draft under different ballasts, the structure below the waterline is extracted and re-meshed in PATRAN, and the hull mesh and hydrodynamic mesh are extracted; (2) Determine the amplitude response operator of the midship section bending moment, perform the response analysis of the structural midship section bending moment at unit wave height and different frequencies, and determine the frequency range of the maximum midship section bending moment; (3) Determine a series of simulation conditions, select the frequency determined in process (2), and choose 1 / 200 of the ship length as the wave height increment to form a series of simulation parameters; (4) Divide the calculation time, divide the wave period into equal intervals, and obtain multiple calculation times, that is, the wave period of each working condition is 2.1s, the time interval is 0.105s, and a total of 21 times; (5) Perform hydrodynamic calculations and carry out simulation calculations in HYDROSTAR to obtain the wave-induced loads at each moment.

6. The method for simulating the successive collapse of a hull structure in waves according to claim 1, characterized in that: The transformation process of wave-induced loads includes reintegration to obtain the finite element mesh node pressures instead of interpolation, and the conversion of the hydrostatic pressure and hydrodynamic pressure components respectively. The overall acceleration of the hull is obtained by integrating the structural finite element mesh to reduce the calculation error; The calculation process of dynamic water pressure is as follows: The dynamic water pressure calculation is re-integrated in the calculation area. By analyzing the model information, the program can obtain the coordinates of the points to be calculated, and then integrate to obtain the corresponding potential: Where: G is Green's function, x s =(x s ,y s ,z s ) is the structural point, x h =(x h ,y h ,z h ) is the hydrodynamic point, σ is the source strength; exist superior; in, is the hydrodynamic grid at the wet surface, V n represents the hull boundary condition; In the case of no speed, because the water pressure is proportional to the velocity potential, and the velocity potential is continuous on the entire wet surface, when all pressure components are equivalently converted to the structural grid, the load used for structural nonlinear finite element analysis can be obtained by integrating the structural grid, that is: Where: the superscript "s" represents the corresponding load item on the structural grid; The calculation process of hydrostatic pressure is as follows: To solve the hydrostatic recovery matrix, first calculate the dynamic hydrostatic pressure change value P hs ,Right now, P hs =-ρg[η3+η4(Y-Y G )-η5(X-X G )]; For ease of expression, the dynamic hydrostatic pressure change value P hs Expressed more concisely: Among them: P1 hs =0, P3 hs = -ρg, Using this representation, the first part of the hydrostatic response matrix can be expressed as: Among them: n1, n2, n3 represent n x ,n y ,n z , that is, the normal vectors in three directions; n4, n5, n6 represent (RR G )∧n; The complete hydrostatic reversion matrix also needs to consider the change of the coordinate system. An additional item needs to be added to consider the change of the normal direction of the coordinate system. In the fixed coordinate system, the change of the coordinate system is reflected by changing the normal vector, but the structural response analysis is calculated in the ship-borne coordinate system, in which the normal vector does not change. In the ship-borne coordinate system, the change of the normal vector is equivalent to the change of the gravitational acceleration, so it can be written as: F g =-mgΩ^k=[C] g {or}; Where: Ω represents {η4,η5,η6}; Get the total reply matrix: [C] s =[C] P +[C] g 。 7. The method for simulating the successive collapse of a hull structure in waves according to claim 1, characterized in that: The arc length method is used in nonlinear finite element analysis to better track the extreme values ​​of the structure. The complete ABAQUS calculation input file is written in combination with the load ABAQUS calculation input file, structural model information, and calculation method command flow, and then submitted to ABAQUS / COMMAND for calculation.

8. The method for simulating the successive collapse of a hull structure in waves according to any one of claims 1 to 7, characterized in that: This method is suitable for evaluating the ultimate strength and collapse behavior of the hull structure in waves. The ultimate strength of the hull structure and the stress distribution and deformation characteristics during the successive collapse process are obtained through simulation analysis.

Images