Shipboard finite element analysis method based on target value

Abstract

The application discloses a cruise ship finite element analysis method based on a target value, and relates to the field of ship structure design; the method comprises the following steps: establishing a whole ship finite element model; simulating a target load distribution by using a polynomial; converting the target load into a distributed force; applying the distributed force and calculating an actual value; calculating a transfer function; calculating a stress correction amount; correcting the stress; and evaluating the structural strength; the target load is converted into a distributed force along the ship length by using a numerical method, the obtained load is a load applied to the model, the actual value of the load is obtained, the stress result is obtained through a transfer function condition, the stress caused by the unit bending moment and the shear force on the element is calculated according to the stress result, the stress calculation is the transfer function, the stress correction amount is calculated, and the actual stress is corrected; the stress result after the correction can more accurately reflect the stress distribution of the ship beam under the target load, and the method has a great improvement in fitting precision compared with the existing method.

Description

Technical Field

[0001] This invention relates to the field of ship structural design, specifically to a finite element analysis method for cruise ships based on target values. Background Technology

[0002] The finite element method (FEM) is widely used for ship structural strength assessment. For general cargo ships, the finite element method for individual compartments is sufficient. However, for high-tech, high-value-added vessels, such as large liquefied gas carriers, container ships, and cruise ships, whole-ship finite element analysis is necessary. A whole-ship finite element model can better simulate the overall stiffness characteristics of the hull, thus obtaining a more realistic stress distribution. However, because displacement constraints cannot be applied at both ends of the model as with compartment models, the loading of a whole-ship finite element model is limited, requiring the applied loads to form a balanced force system.

[0003] To address this challenge, existing whole-ship finite element analysis methods obtain wave loads through hydrodynamic analysis. These loads form a balanced force system with zero resultant force and moment. This force system is then superimposed with the static load and applied to the model for structural analysis. The resulting total load also forms a balanced force system acting on the whole-ship model, thus bringing the model to equilibrium. When using existing whole-ship finite element methods, a specific wave load parameter is used as the dominant load to determine the design wave. The design wave can bring the dominant load to its target value and determine the values ​​of other load components, but it generally cannot achieve the target value.

[0004] For cruise ships, the overall longitudinal strength of the hull beams is the most important assessment target in the overall ship analysis. However, existing methods can only achieve the target value of the hull beam load at a certain longitudinal position. The stress results obtained from this cannot reflect the worst possible conditions, and the assessment of the hull structure strength is not accurate enough, with stresses either too high or too low. Summary of the Invention

[0005] The purpose of this invention is to provide a finite element analysis method for cruise ships based on target values. This method uses numerical methods to transform the target load into a distributed force along the ship's length, generating bending moments and target shear forces. The resulting loads are the actual values ​​of the loads applied to the model. Stress results are obtained through transfer function conditions, and the stresses caused by unit bending moments and shear forces on the elements are calculated based on these stress results. The stress calculation is the transfer function. Stress corrections are calculated based on the transfer function and the difference between the actual load values ​​at each location and the target load values. The actual stresses are then corrected based on these corrections, resulting in a more accurate reflection of the stress distribution of the ship's beams under the target load.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This application provides a finite element analysis method for cruise ships based on target values, including the following steps:

[0008] S1: Establish a finite element model of the entire ship. Based on the geometry, structural layout and material properties of the cruise ship, establish a finite element model of the entire cruise ship in the finite element software.

[0009] S2: Determine the target load distribution. Based on the design requirements of the entire cruise ship and the strength indicators that need to be evaluated, determine the target load distribution of the hull beams at different locations, including the distribution of bending moment and shear force.

[0010] S3: Use polynomials to simulate the target load distribution. Use polynomial functions (such as 5th degree polynomials) to simulate the distribution of the target load along the ship's length, determine the coefficients, and transform the target load into a continuous function expression.

[0011] S4: The target load is converted into a distributed force. Based on the differential / integral relationship of the load, the target load is converted into a distributed force distributed along the length of the ship using numerical methods.

[0012] S5: Apply distributed force and calculate actual value. Load the obtained distributed force into the whole ship finite element model, perform whole ship analysis, and obtain the actual stress and deformation results of each section of the hull under the target load.

[0013] S6: Calculate the transfer function. Based on the actual stress results and the transfer function conditions, calculate the stress caused by the unit bending moment and shear force on the element. The stress calculation is the transfer function.

[0014] S7: Calculate the stress correction amount based on the transfer function and the difference between the actual and target values ​​of the load at each location;

[0015] S8: Stress correction, by correcting the actual stress result, the deviation is added to the actual stress value to obtain the stress result under the target load;

[0016] S9: Structural strength assessment. The structural strength is assessed using the corrected stress results to check whether the hull structure meets the design requirements and strength indicators.

[0017] As a preferred method, the numerical method described in step S4 is the finite element method. First, the region is determined, and the hull is divided into several small regions along the length of the ship, which are called finite element methods. The load in each small region is considered to be uniformly distributed. Then, the distributed force is numerically calculated. By applying the target load to the corresponding finite element and using the finite element method to solve the displacement and stress field of the structure, the distributed force along the length of the ship is obtained.

[0018] Preferably, based on the bending moment described in step S2, the distribution of the target bending moment along the ship's length is simulated using a 5th-order polynomial. The bending moment is calculated as follows:

[0019] BM1(x)=M W (a1x 5 +a2x 4 +a3x 3 +a4x 2 );

[0020] Where BM1(x) represents the target bending moment distribution along the ship's length direction, in kN·m, and x represents the ship's position coordinates, M W These are represented as scaling factors, used to adjust the overall bending moment; a1, a2, a3, and a4 are represented as coefficients of determination.

[0021] Preferably, based on the shear force distribution described in step S2, the distribution expression of wave shear force along the ship's length is obtained by differentiating the calculation method of the bending moment:

[0022] SF1(x)=M W / L0(5a1x 4 +4a2x 3 +3a3x 2 +2a4x);

[0023] Where SF1(x) represents the distribution function of wave shear force along the ship's length, M W Used to adjust the magnitude of the overall wave shear force, x represents the ship's position coordinates, and L0 is a length scale used to convert the wave shear force into a distributed force per unit length.

[0024] Preferably, based on the distributed force described in step S4, the expression for the distributed force is obtained by further differentiating the distribution function of the wave shear force along the ship's length direction:

[0025] P1(x)=M W / L 2 0(20a1x 3 +12a2x 2 +6a3x+2a4);

[0026] Where P1(x) represents the magnitude of the distributed force at different positions x on the hull structure, M W L0 is a length scale used to adjust the magnitude of the overall distributed force, and is used to convert the distributed force into a value per unit length.

[0027] Preferably, the stress correction is calculated based on the transfer function described in step S7 and the difference between the actual load value and the target load value at each location. The expression for the stress correction in the x-direction is as follows:

[0028] σ x =σ x-FEM +fmx ΔM+f mx ΔQ;

[0029] Where, σ x Expressed as the stress correction in the x-direction, the stress amplitude refers to the range of stress variation under dynamic or fatigue loading, used to assess the fatigue life and strength of a structure; σ x-FEM This represents the stress in the x-direction from the actual stress results obtained through finite element analysis; f mx It is expressed as a transfer function in the x-direction, describing the stress induced on a unit moment element.

[0030] Preferably, the expression for the stress correction in the y-direction is as follows:

[0031] σ y =σ y-FEM +f my ΔM+f my ΔQ;

[0032] Where, σ y This is expressed as the stress correction in the y-direction; σ y-FEM This represents the stress in the y-direction from the actual stress results obtained through finite element analysis; f my It is expressed as a transfer function in the y-direction, describing the stress induced on a unit bending moment element.

[0033] Preferably, the expression for the shear stress component of the stress correction is as follows:

[0034] γ xy =γ xy-FEM +f mxy ΔM+f mxy ΔQ;

[0035] Where, γ xy The shear stress component, expressed as a stress correction, is γ. xy-FEM This represents the shear stress in the actual stress results obtained from finite element analysis; f mxy It is expressed as the transfer function of the shear stress component, describing the stress induced by a unit bending moment on the shear stress component of the stress correction.

[0036] Preferably, the expression for the stress amplitude correction amount is:

[0037] σ a =σ aFEM +f ma ΔM+f qa ΔQ;

[0038] Where, σ a This is expressed as a stress amplitude correction factor; σ aFEMΔM represents the stress amplitude in the actual stress results obtained from the finite element analysis; ΔQ represents the difference between the target bending moment and the actual bending moment; f represents the difference between the target shear force and the actual shear force. ma Expressed as a transfer function of stress amplitude, it describes the change in stress amplitude caused by unit bending moment and shear force on an element; f qa It is expressed as a stress range transfer function, which describes the change in stress range caused by a unit shear force on an element.

[0039] Preferably, according to the structural strength assessment described in step S9, after obtaining the corrected stress results, the corrected stress results are compared with the design requirements and strength indicators. If the structural strength meets the design requirements and strength indicators, the strength assessment ends, and the structure has sufficient strength and safety. If the structural strength does not meet the requirements, it needs to be modified and optimized. After structural optimization or reinforcement, the assessment is returned to the whole ship finite element model, the previous steps are repeated, the corrected stress results are obtained, and the strength is checked and compared with the specifications again.

[0040] The beneficial effects of this invention are as follows:

[0041] (1) This method uses the differential / integral relationship of the load to convert the target load into a distributed force along the ship length through numerical methods. The resulting bending moment and target shear force will be close to the target bending moment and target shear force. The obtained load is the load applied to the model and the actual value of the load is obtained. The stress result is obtained through the transfer function working condition, and the stress caused by the unit bending moment and shear force on the element is calculated based on the stress result. The stress calculation is the transfer function. The stress correction amount is calculated based on the transfer function and the difference between the actual load value and the target load value at each position. The actual stress is corrected based on the stress correction amount. The corrected stress result can more accurately reflect the stress distribution of the ship beam under the target load. This method has greatly improved the fitting accuracy compared with the existing methods.

[0042] (2) Through strength assessment and structural optimization, the corrected stress results are used to assess the structural strength, which can check whether the hull structure meets the design requirements and strength indicators. If the structural strength does not meet the requirements, the corresponding structural optimization or reinforcement can be carried out and the assessment can be repeated until the strength requirements are met. Attached Figure Description

[0043] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0044] Figure 1 A flowchart of the finite element analysis method for cruise ships based on target values ​​provided in this application;

[0045] Figure 2The target-actual bending moment curve is shown in the finite element analysis method for cruise ships based on target values ​​provided in this application. Detailed Implementation

[0046] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description relating to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and systems consistent with some aspects of this application as detailed in the appended claims.

[0047] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0048] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0049] Example 1

[0050] Please see Figures 1-2 In this embodiment, a finite element model of the entire ship is established to determine the target load. Utilizing the differential / integral relationship of the load, the target load is converted into a distributed force along the ship's length using numerical methods. The resulting bending moment and target shear force will approximate the target bending moment and target shear force, and the obtained load is the actual value of the load applied to the model. Stress results are obtained through the transfer function load case, and the stress caused by unit bending moment and shear force on the element is calculated based on the stress results. The stress correction is calculated based on the transfer function and the difference between the actual load value and the target load value at each location. The actual stress is then corrected based on the stress correction, and the corrected stress result can more accurately reflect the stress distribution of the hull beams under the target load.

[0051] This invention provides a finite element analysis method for cruise ships based on target values, comprising the following steps:

[0052] S1: Establish a finite element model of the entire ship. Based on the geometry, structural layout and material properties of the cruise ship, establish a finite element model of the entire cruise ship in the finite element software. The model should include the main structural components such as the various sections of the hull, decks, longitudinal and transverse beams, keel, etc., and take into account the connection methods and support devices.

[0053] In this embodiment, the finite element model of the entire ship includes various structural parts of the hull, such as hull plates, decks, keel, longitudinal and transverse beams, and support devices. The finite element model needs to specify the material properties used in the hull structure, including elastic modulus, Poisson's ratio, yield strength, and fracture toughness. These material properties are used to calculate the stress and deformation of the structure. Appropriate boundary conditions need to be set in the finite element model, including fixed supports, constraints, and applied loads. Boundary conditions are used to limit the displacement or stress of certain nodes to reflect the constraint situation under actual working conditions. Then, according to the actual working conditions and design requirements, corresponding loads are applied to the finite element model. These loads may include self-weight, additional loads (such as cargo and equipment), wind loads, and wave loads. The magnitude, direction, and location of the load application need to be specified.

[0054] S2: Determine the target load distribution. Based on the design requirements of the entire cruise ship and the strength indicators that need to be evaluated, determine the target load distribution of the hull beams at different locations, including the distribution of bending moment and shear force.

[0055] S3: The target load distribution is simulated using a polynomial. A polynomial function (such as a 5th degree polynomial) is used to simulate the distribution of the target load along the ship's length. By determining the coefficients, the target load is transformed into a continuous function expression.

[0056] S4: The target load is converted into distributed forces. Based on the differential / integral relationship of the load, the target load is converted into distributed forces along the ship's length using numerical methods, i.e., stresses on the load. These distributed forces can be applied to the corresponding hull beams and structures.

[0057] S5: Apply distributed forces and calculate actual values. Load the obtained distributed forces into the entire ship's finite element model and perform a whole-ship analysis to obtain the actual stress and deformation results on each section of the hull under the target load. These actual values ​​may deviate from the target values ​​due to the envelope characteristics of the target load.

[0058] S6: Calculate the stress transfer function. Based on the actual stress results and the load conditions of the stress transfer function, calculate the stress caused by unit bending moment and shear force on the element. The stress calculation is the stress transfer function. The stress transfer function describes the law of stress transfer in the hull structure.

[0059] In this embodiment, the target bending moment is calculated by simulating the target load distribution using a polynomial method. The resulting distributed force is then applied to the entire ship's finite element model for whole-ship analysis. This yields the actual bending moment on each section of the hull under the target load, resulting in the target-actual bending moment curve, as shown below. Figure 2 As shown,

[0060] Where 1 represents the actual bending moment on the model after the load is applied, and 2 represents the target bending moment. As shown in the figure, the two match very well, which is a huge improvement in fitting accuracy compared with existing methods.

[0061] In this embodiment, before calculating the transfer function, the load under the transfer function condition needs to be applied first, and then the structural analysis is performed. After the transfer function is calculated, the transfer function is combined with the stress transfer function calculated by applying the load to the ship beam to correct the stress result.

[0062] In this embodiment, the load cases of the transfer function include bending moment load cases, shear force load cases, etc. The load cases of the transfer function may also involve different boundary conditions, such as fixed supports, free ends, etc. These boundary conditions will affect the calculation results of the transfer function.

[0063] S7: Calculate the stress correction. Based on the transfer function and the difference between the actual and target load values ​​at each location, calculate the stress correction. The stress correction represents the deviation between the actual stress and the target stress.

[0064] S8: Stress correction, by correcting the actual stress result, the deviation is added to the actual stress value to obtain the stress result under the target load;

[0065] S9: Structural strength assessment. The structural strength is assessed using the corrected stress results to check whether the hull structure meets the design requirements and strength indicators. Based on the assessment results, necessary structural optimization or reinforcement measures can be taken.

[0066] In this embodiment, according to the numerical method described in step S4, common numerical methods include the finite difference method and the finite element method. Choosing the finite element method, the region is first determined by dividing the hull along its length into several small regions, called finite element units. The load within each small region can be considered uniformly distributed, thus approximating a distributed force. The distributed force is then numerically calculated by applying the target load to the corresponding finite element unit and using the finite element method to solve for the displacement and stress field of the structure, thereby obtaining the distributed force along the ship's length.

[0067] In this embodiment, based on the bending moment described in step S2, the distribution of the target bending moment along the ship's length is simulated using a 5th-order polynomial. The bending moment is calculated as follows:

[0068] BM1(x)=M W (a1x 5 +a2x 4 +a3x 3 +a4x 2 );

[0069] Where BM1(x) represents the target bending moment distribution along the ship's length, x represents the ship's position coordinates, and M W These are represented as scaling factors, used to adjust the overall bending moment; a1, a2, a3, and a4 are represented as coefficients of determination.

[0070] In this embodiment, based on the shear force distribution described in step S2, the distribution expression of wave shear force along the ship's length is obtained by differentiating the calculation method of the bending moment:

[0071] SF1(x)=M W / L0(5a1x 4 +4a2x 3 +3a3x 2 +2a4x);

[0072] Where SF1(x) represents the distribution function of wave shear force along the ship's length, M W Used to adjust the magnitude of the overall wave shear force, x represents the ship's position coordinates, and L0 is a length scale used to convert the wave shear force into a distributed force per unit length.

[0073] In this embodiment, based on the distributed force described in step S4, the expression for the distributed force is obtained by further differentiating the distribution function of the wave shear force along the ship's length direction:

[0074] P1(x)=M W / L 2 0(20a1x 3 +12a2x 2 +6a3x+2a4);

[0075] Where P1(x) represents the magnitude of the distributed force at different positions x on the hull structure, M W L0 is a length scale used to adjust the magnitude of the overall distributed force, and is used to convert the distributed force into a value per unit length.

[0076] In this embodiment, the stress correction is calculated based on the transfer function described in step S7 and the difference between the actual load value and the target load value at each location. The expression for the stress correction in the x-direction is as follows:

[0077] σ x =σ x-FEM +f mx ΔM+f mx ΔQ;

[0078] Where, σ x Expressed as the stress correction in the x-direction, the stress amplitude refers to the range of stress variation under dynamic or fatigue loading, used to assess the fatigue life and strength of a structure; σ x-FEMThis represents the stress in the x-direction from the actual stress results obtained through finite element analysis; f mx It is expressed as a transfer function in the x-direction, describing the stress induced on a unit bending moment element;

[0079] In this embodiment, the expression for the stress correction in the y-direction is as follows:

[0080] σ y =σ y-FEM +f my ΔM+f my ΔQ;

[0081] Where, σ y This is expressed as the stress correction in the y-direction; σ y-FEM This represents the stress in the y-direction from the actual stress results obtained through finite element analysis; f my It is expressed as a transfer function in the y-direction, describing the stress induced on a unit bending moment element;

[0082] In this embodiment, the expression for the shear stress component of the stress correction is as follows:

[0083] γ xy =γ xy-FEM +f mxy ΔM+f mxy ΔQ;

[0084] Where, γ xy The shear stress component, expressed as a stress correction, is γ. xy-FEM This represents the shear stress in the actual stress results obtained from finite element analysis; f mxy It is expressed as the transfer function of the shear stress component, which describes the stress induced on the shear stress component by a unit bending moment with respect to the stress correction.

[0085] In this embodiment, the expression for the stress amplitude correction amount is:

[0086] σ a =σ aFEM +f ma ΔM+f qa ΔQ;

[0087] Where, σ a This is expressed as a stress amplitude correction factor; σ aFEM ΔM represents the stress amplitude in the actual stress results obtained from the finite element analysis; ΔQ represents the difference between the target bending moment and the actual bending moment; f represents the difference between the target shear force and the actual shear force. ma Expressed as a transfer function of stress amplitude, it describes the change in stress amplitude caused by unit bending moment and shear force on an element; f qaIt is expressed as a stress range transfer function, which describes the change in stress range caused by a unit shear force on an element.

[0088] In this embodiment, according to the structural strength assessment described in step S9, after obtaining the corrected stress results, the influence of the target load is considered, which more accurately reflects the stress state of the structure under the target load. The corrected stress results are compared with the design requirements and strength indicators. The comparison requirements include the assessment of stress extreme values, stress amplitude, stress range, fatigue life, etc. If the structural strength meets the design requirements and strength indicators, the strength assessment ends, and the structure has sufficient strength and safety. If the structural strength does not meet the requirements, modification and optimization are required. For the parts that do not meet the strength requirements, structural optimization or strengthening measures are designed, which may include adjusting the structural dimensions, increasing the material thickness, changing the structural layout, etc. Through optimization and strengthening, the structure meets the design requirements and its strength and stability are improved. After structural optimization or strengthening, the assessment is returned to the whole ship finite element model, the previous steps are repeated, the corrected stress results are obtained, and the strength is checked and compared with the specifications again.

[0089] Example 2

[0090] This embodiment utilizes a polynomial form of the bending moment distribution formula for bending moment prediction and finite element analysis, and evaluates the bending moment response of the cruise ship structure. This allows for a more accurate understanding of the bending moment distribution characteristics of the cruise ship under different operating conditions, providing a reference for optimized design and structural strength assessment.

[0091] This invention provides a finite element analysis method for cruise ships based on target values, comprising the following steps:

[0092] Collect data, including actual data related to the bending moment distribution of the cruise ship. This data can come from design documents, experimental data, or other sources.

[0093] Data preprocessing involves preprocessing the collected data, including data cleaning, outlier removal, and normalization, to ensure the accuracy and usability of the data.

[0094] For fitting parameter selection, choose an appropriate number of parameters n based on the required polynomial order. Determine the optimal polynomial order through experimentation and verification.

[0095] Polynomial fitting uses a fitting algorithm (such as the least squares method) to fit the preprocessed data into a polynomial form of the bending moment distribution formula. During the fitting process, the values ​​of the coefficients a0, a1, ..., an are adjusted to make the fitting result as close as possible to the actual data.

[0096] The target load is converted into a distributed force. Based on the target load distribution, it is converted into a distributed force along the ship's length direction. This can be calculated using numerical methods. The resulting distributed force is then applied to the corresponding hull beams and structures. The distributed force is then applied and the actual value is calculated, the transfer function is calculated, the stress correction is calculated, and the stress correction and structural strength assessment are performed.

[0097] The polynomial form of the expression for calculating the distribution of the fitted bending moment along the ship's length is as follows:

[0098] BM(x) = a0 + a1x + a2x 2 +...+a n x n

[0099] BM(x) represents the bending moment distribution along the ship's length, where x represents the ship's position coordinates, and a0, a1, ..., a n These represent the coefficients of determination, used to describe the distribution of bending moment in the hull structure; based on actual data and fitting algorithms (such as the least squares method), the coefficients a0, a1, ..., a are determined. n The value of is used to fit the preprocessed data into a polynomial form of the bending moment distribution formula.

[0100] Example 3

[0101] This embodiment mainly addresses the problem that existing methods, which achieve the target value of the hull beam load at a certain longitudinal position, cannot reflect the worst possible conditions, resulting in inaccurate assessment of the hull structure strength and either excessively high or low stress.

[0102] This embodiment introduces a variable cross-section beam model to adaptively adjust the cross-section size and stiffness according to actual working conditions and loading.

[0103] The specific steps include:

[0104] Step 1: Determine the initial cross-section. Based on the design parameters and ship structural requirements, determine the initial cross-section shape, dimensions, and material properties.

[0105] Step 2: Establish a finite element model. Using finite element analysis software, establish a three-dimensional finite element model of the ship's hull beam. In the model, set the cross-sectional properties of each beam element to the initial cross-section.

[0106] Step 3: Define loading conditions. Based on the actual working conditions and loading situation, define the loads on the hull beams. This includes static and dynamic loads, such as gravity loads and acceleration loads caused by hull motion.

[0107] Step 4: Solve the finite element model. By solving the finite element model, the stress and deformation distribution of the hull beam under different working conditions can be obtained.

[0108] Step 5: Adjust the cross-section. Based on the solution results, evaluate the stress and deformation of each beam element. If some beam elements are found to have excessively high stress or large deformation, cross-section adjustment is required.

[0109] Step 6: Cross-section adjustment calculation. Based on the required strength and stiffness requirements, use structural mechanics theory and empirical formulas to calculate the new cross-section dimensions and stiffness. Adjust the cross-section shape, height, width and other parameters of the beam element according to the magnitude of stress and deformation.

[0110] Step 7: Update the finite element model by updating the corresponding beam elements in the finite element model with the new cross-sectional dimensions and stiffness information;

[0111] Step 8: Repeat the solution and adjustment, repeating steps 4-7, until the hull beam design meets the strength and stiffness requirements;

[0112] Step 9: Evaluate the results. By iteratively adjusting and solving the variable cross-section beam model, a more accurate distribution of stress and deformation in the hull beams can be obtained. Ultimately, the evaluation results can be used to determine the overall longitudinal strength of the hull beams and provide optimized design recommendations.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A finite element analysis method for cruise ships based on target values, characterized in that: Includes the following steps: S1: Establish a finite element model of the entire ship. Based on the geometry, structural layout and material properties of the cruise ship, establish a finite element model of the entire cruise ship in the finite element software. S2: Determine the target load distribution. Based on the design requirements of the entire cruise ship and the strength indicators that need to be evaluated, determine the target load distribution of the hull beams at different locations, including the distribution of bending moment and shear force. S3: The target load distribution is simulated using a polynomial. A polynomial function is used to simulate the distribution of the target load along the ship's length, and the coefficients are determined to transform the target load into a continuous function expression. S4: The target load is converted into a distributed force. Based on the differential / integral relationship of the load, the target load is converted into a distributed force distributed along the length of the ship using numerical methods. S5: Apply distributed force and calculate actual value. Load the obtained distributed force into the whole ship finite element model, perform whole ship analysis, and obtain the actual stress and deformation results of each section of the hull under the target load. S6: Calculate the transfer function. Based on the actual stress results and the transfer function conditions, calculate the stress caused by the unit bending moment and shear force on the element. The stress calculation is the transfer function. S7: Calculate the stress correction amount based on the transfer function and the difference between the actual and target values ​​of the load at each location; S8: Stress correction, by correcting the actual stress result, the deviation is added to the actual stress value to obtain the stress result under the target load; S9: Structural strength assessment. The structural strength is assessed using the corrected stress results to check whether the hull structure meets the design requirements and strength indicators.

2. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: According to the numerical method described in step S4, the finite element method is used. First, the region is determined and the hull is divided into several small regions along the length of the ship, which are called finite elements. The load in each small region is considered to be uniformly distributed. Then, the distributed force is numerically calculated. By applying the target load to the corresponding finite element and using the finite element method to solve the displacement and stress field of the structure, the distributed force along the length of the ship is obtained.

3. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: Based on the bending moment described in step S2, the distribution of the target bending moment along the ship's length is simulated using a 5th-order polynomial. The bending moment is calculated as follows: BM1(x) = M W (a1x 5 +a2x 4 +a3x 3 +a4x 2 ); Where BM1(x) represents the target bending moment distribution along the ship's length direction, in kN·m, and x represents the ship's position coordinates, M W These are represented as scaling factors, used to adjust the overall bending moment; a1, a2, a3, and a4 are represented as coefficients of determination.

4. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: Based on the shear force distribution described in step S2, the distribution expression of wave shear force along the ship's length is obtained by differentiating the calculation method of the bending moment: SF1(x)=M W / L0(5a1x 4 +4a2x 3 +3a3x 2 +2a4x); Where SF1(x) represents the distribution function of wave shear force along the ship's length, in units of kN and M. W Used to adjust the magnitude of the overall wave shear force, x represents the ship's position coordinates, and L0 is a length scale used to convert the wave shear force into a distributed force per unit length.

5. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: Based on the distributed force described in step S4, by further differentiating the distribution function of wave shear force along the ship's length, the expression for the distributed force is obtained: P1(x)=M W / L 2 0(20a1x 3 +12a2x 2 +6a3x+2a4); Where P1(x) represents the magnitude of the distributed force at different locations x on the hull structure, in kN / m, M W L0 is a length scale used to adjust the magnitude of the overall distributed force, and is used to convert the distributed force into a value per unit length.

6. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: The stress correction is calculated based on the transfer function described in step S7 and the difference between the actual load value and the target load value at each location. The expression for the stress correction in the x-direction is as follows: s x = σ x-FEM +f mx ΔM+f mx ΔQ; Where, σ x Expressed as the stress correction in the x-direction, the stress amplitude refers to the range of stress variation under dynamic or fatigue loading, used to assess the fatigue life and strength of a structure; σ x-FEM The stress in the x-direction is represented by the actual stress result obtained from the finite element analysis; ΔM represents the difference between the target bending moment and the actual bending moment; ΔQ represents the difference between the target shear force and the actual shear force; f mx It is expressed as a transfer function in the x-direction, describing the stress induced on a unit moment element.

7. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: The expression for the stress correction in the y-direction is as follows: s y = σ y-FEM +f my ΔM+f my ΔQ; Where, σ y This is expressed as the stress correction in the y-direction; σ y-FEM The stress in the y-direction is represented by the actual stress obtained from the finite element analysis; ΔM represents the difference between the target bending moment and the actual bending moment; ΔQ represents the difference between the target shear force and the actual shear force; f my It is expressed as a transfer function in the y-direction, describing the stress caused by a unit bending moment on the element.

8. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: The expression for the shear stress component of the stress correction is as follows: c xy = c xy-FEM +f mxy ΔM+f mxy ΔQ; Where, γ xy The shear stress component, expressed as a stress correction, is γ. xy-FEM The shear stress is represented by ΔM, which is the difference between the target bending moment and the actual bending moment obtained from the finite element analysis; ΔQ represents the difference between the target shear force and the actual shear force; f mxy It is expressed as the transfer function of the shear stress component, describing the stress induced by a unit bending moment on the shear stress component of the stress correction.

9. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: The expression for the stress amplitude correction amount is: s a = σ aFEM +f ma ΔM+f qa ΔQ; Where, σ a This is expressed as a stress amplitude correction factor; σ aFEM ΔM represents the stress amplitude in the actual stress results obtained from the finite element analysis; ΔQ represents the difference between the target bending moment and the actual bending moment; f represents the difference between the target shear force and the actual shear force. ma Expressed as a transfer function of stress amplitude, it describes the change in stress amplitude caused by unit bending moment and shear force on an element; f qa It is expressed as a stress range transfer function, which describes the change in stress range caused by a unit shear force on an element.

10. The finite element analysis method for cruise ships based on target values ​​according to claim 1, characterized in that: According to the structural strength assessment described in step S9, after obtaining the corrected stress results, the corrected stress results are compared with the design requirements and strength indicators. If the structural strength meets the design requirements and strength indicators, the strength assessment ends and the structure has sufficient strength and safety. If the structural strength does not meet the requirements, it needs to be modified and optimized. After structural optimization or reinforcement, the assessment is returned to the whole ship finite element model. The previous steps are repeated to obtain the corrected stress results and to perform strength verification and comparison with specifications again.

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