Structural lightweight design method for methanol-powered bulk carrier

Abstract

The invention belongs to the technical field of ship structure lightweight design, and particularly discloses a structural lightweight design method for a methanol-powered bulk cargo ship, which comprises the following steps of: performing stress acquisition and water area environment parameter acquisition on each component on a ship body structure in the running process of a methanol-powered bulk cargo demonstration ship; therefore, component groups with merging potential are screened out, a demonstration ship structure lightweight model after component merging is built according to the component groups, operation simulation is carried out in different water area environments, and the component groups with the merging potential and feasible simulation results are selected from the model groups to carry out actual component merging design. On the premise that the operation safety of the ship body is guaranteed, the light weight of the structure can be achieved, the material consumption is invisibly reduced, the construction cost is reduced, meanwhile, the resource utilization efficiency is improved, in addition, the failure risk of connecting parts can be reduced by reducing the number of connecting points, and the safety and reliability of the ship body can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lightweight design of ship structures, and specifically discloses a lightweight design method for a methanol-powered bulk carrier. Background Art

[0002] As an alternative fuel, methanol has gradually attracted widespread attention in the shipping industry because it can significantly reduce greenhouse gas emissions and comply with the increasingly stringent environmental regulations of the International Maritime Organization. For bulk carriers powered by methanol, lightweight structural design is a key factor in increasing the ship's payload capacity, improving fuel efficiency and reducing operating costs.

[0003] In the lightweight design of methanol-powered bulk carriers, two main methods are usually adopted: material distribution optimization and hull shape optimization. Material distribution optimization aims to reduce weight as much as possible while meeting the structural strength requirements, while hull shape optimization reduces the requirements for structural strength by reducing water resistance, thereby indirectly achieving lightweighting. These optimization measures are usually carried out on the basis of maintaining the original component distribution of the hull structure to ensure that the integrity of the structure is not damaged.

[0004] In the initial design of the hull structure, splicing is usually used instead of integrated components. This design allows for a more flexible assembly sequence and method, which can significantly improve construction efficiency, especially in the construction of large ships. In addition, spliced ​​components are easy to maintain and replace individually. When a component is damaged, only that part needs to be replaced without replacing the entire integrated component, thereby reducing maintenance costs and time. However, this splicing method introduces a large number of splicing points, and the splicing points require the use of additional connectors (such as welds, bolts, rivets, etc.), which invisibly increases the total amount of hull materials. In addition, it does not take into account that the stress state of some adjacent components may be consistent during the operation of the ship. For these adjacent and similarly stressed components, continuing to use the splicing method appears redundant and inefficient, and fails to fully tap the potential of lightweight design. Summary of the invention

[0005] To this end, one purpose of an embodiment of the present application is to provide a structural lightweight design method for a methanol-powered bulk carrier, which effectively solves the problems mentioned in the background technology by focusing on the distribution of hull components to achieve lightweight design of the hull structure.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A structural lightweight design method for a methanol-powered bulk carrier, comprising the following steps: counting the components existing in the main structure of a methanol-powered bulk carrier demonstration ship, and installing stress sensors on each component, and deploying a water environment collection terminal outside the hull.

[0007] During the selected water operation period, stress sensors are used in real time to collect stresses of various components of the demonstration ship, and water environment parameters are simultaneously recorded through the water environment collection terminal, thereby generating stress time series data of each component and water environment parameter time series data.

[0008] Based on the stress time series data of each component and the time series data of water environment parameters, similar stress-bearing component groups are identified, and component groups with potential for merging are screened out.

[0009] A lightweight model of the demonstration ship structure after component merging is built based on the combined potential component group, and the extreme performance values ​​of the water environment parameters are extracted from the time series data of the water environment parameters.

[0010] The lightweight model of the demonstration ship structure is simulated under extreme performance values ​​of the water environment parameters, and the deformation and stress distribution data are collected by focusing on the merged component area during the simulation.

[0011] The feasibility of component merging is evaluated based on the deformation and stress distribution data in the merged component area.

[0012] The structural lightweight design of the demonstration ship is carried out based on the evaluation results of the feasibility of component merging.

[0013] Combined with all the above technical solutions, the positive effects of the present invention are as follows: the present invention collects stress and water environment parameters of each component of the hull structure during the operation of the methanol-powered bulk cargo demonstration ship, thereby screening out component groups with merging potential, and accordingly builds a lightweight model after the components are merged to conduct simulation tests in different water environments, from which feasible merging potential component groups are selected for actual design, which can achieve lightweight structure while ensuring the safety of hull operation. This not only reduces the amount of materials and construction costs, improves resource utilization efficiency, but also reduces the failure risk of the connection parts by reducing the number of connection points, and improves the safety and reliability of the hull. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0015] Figure 1 The present invention is a flowchart of the steps for implementing the method.

[0016] Figure 2 It is a schematic diagram of the identification operation of a group of similar force-bearing components of the present invention.

[0017] Figure 3 The present invention is a schematic diagram of the feasibility of component merging operation based on deformation and stress distribution data of the merged component area. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1 As shown, the present invention proposes a structural lightweight design method for a methanol-powered bulk carrier, comprising the following steps: counting the components existing in the main structure of the methanol-powered bulk carrier demonstration ship, and installing stress sensors on each component, and deploying a water environment collection terminal outside the hull.

[0020] It is important to know that the demonstration ship mentioned above refers to a dry bulk carrier that uses methanol as its main fuel. Its design and construction are intended to demonstrate and verify the technical feasibility and environmental benefits of methanol as an alternative fuel in the shipping industry. This type of demonstration ship collects performance data, evaluates fuel efficiency, monitors emission levels, and verifies the safety and reliability of the methanol fuel system through actual operation. The construction and design of the demonstration ship will provide an important reference for subsequent methanol-powered bulk carriers. Therefore, by designing the demonstration ship with a lightweight structure, it can provide key guidance for future ship design optimization.

[0021] In the example implementation of the above scheme, the water environment acquisition terminal includes a current meter, a wave sensor, and a wind sensor, etc., wherein the current meter is used to collect water flow velocity, which reflects the impact force of water flow on the surface of the hull. High-speed water flow will produce significant lateral and longitudinal thrust on the hull, and this thrust will cause the hull structure to bear additional static and dynamic water pressure; the wave sensor is used to collect wave impact frequency, which reflects the impact load of waves on the hull. The heaving movement caused by waves will cause the hull to fluctuate violently up and down, causing the hull structure to bear periodic dynamic loads, which will cause repeated tensile and compressive stresses on the hull structure; the wind sensor is used to collect wind speed, which reflects the wind pressure load on the surface of the hull. Changes in wind speed will cause the hull to be subjected to lateral thrust, which will increase the lateral deviation of the hull. It can be seen that the water environment parameters collected by the current meter, wave sensor, and wind sensor directly reflect the load caused by the water environment on the hull structure, and provide an actual load environment for the subsequent analysis of the stress distribution of each component on the hull structure.

[0022] During the selected water operation period, stress sensors are used in real time to collect stresses of various components of the demonstration ship, and water environment parameters are simultaneously recorded through a water environment collection terminal, where water environment parameters include water flow velocity, wave impact frequency and wind speed. Of course, water environment parameters are not limited to these, but can also include water temperature, thereby generating stress time series data of each component and water environment parameter time series data.

[0023] It should be added that in order to ensure that the performance of the lightweight structure design in harsh water environments meets the requirements, the collection of water environment parameters should cover typical harsh water conditions as much as possible. For this reason, when selecting the water operation period, it is recommended to select the time period with a high probability of harsh water environments in history for hull component stress distribution analysis based on historical ship operation data. This is because harsh water environments usually have periodic characteristics. Selecting this period can capture extreme water conditions to the maximum extent, providing representative data support for lightweight structure design. At the same time, it can also provide a simulation environment of actual extreme working conditions for the performance test after the components are merged, thereby effectively simulating the harsh working conditions that ships may encounter in actual operations and ensuring the reliability of the simulation results.

[0024] Based on the stress time series data of each component and the time series data of water environment parameters, similar stress-bearing component groups are identified, and component groups with potential for merging are screened out.

[0025] In the preferred implementation of the above scheme, see Figure 2 As shown, the identification of similarly stressed component groups refers to the following process: the components are paired up to form several component groups, and the stress difference of the stress-time series data of each component group is calculated at the same time, and then compared with the set critical stress difference. Exemplarily, the critical stress difference is 2MPa. If the stress difference of a component group at a certain time is less than or equal to the critical stress difference, the component group is used as a candidate component group with similar stress, and the time is used as the similar stress time.

[0026] In the above preferred implementation example, it is assumed that the main structure of the methanol-powered bulk cargo demonstration ship has 5 components, marked as A, B, C, D, and E, and they are grouped in pairs to form the following component groups: (A, B), (A, C), (A, D), (A, E), (B, C), (B, D), (B, E), (C, D), (C, E), (D, E). At this time, assuming that the stress difference of (A, B), (A, C), (B, C), (B, E), and (D, E) at a certain time is less than or equal to the critical stress difference, then (A, B), (A, C), (B, C), (B, E), and (D, E) are used as alternative component groups with similar forces.

[0027] The water environment parameters corresponding to similar stress times are extracted from the water environment parameter time series data.

[0028] The number of similar stress times captured in the stress time series data of each similar stress alternative component group is counted, and the water environment distribution state corresponding to the similar stress time is identified based on the water environment parameters corresponding to the similar stress time, where the water environment distribution state includes the duration of similar stress time in the same water environment and the number of similar stress time in different water environments.

[0029] Specifically, the water environment distribution state corresponding to the similar force-bearing time is identified as follows: the water environment parameters corresponding to the adjacent similar force-bearing time are similarly calculated to obtain the water environment parameter similarity. The specific similarity calculation formula is: Where WE similarity Indicates the similarity of water environment parameters, ΔG d represents the difference of water environment parameters corresponding to adjacent force-bearing times, d represents the water environment parameter number, d=1 or d=2 or d=3, where d=1 represents water flow velocity, d=2 represents wave impact frequency, d=3 represents wind speed, G d It represents the water environment parameter corresponding to the previous similar stress time in adjacent similar stress times, R represents the set constant, and R>1, exemplarily, R=3, when the similarity is calculated, the similarity of the water environment parameter is greater only when each water environment parameter corresponding to the adjacent similar stress times is similar, and it is compared with the set similarity threshold, exemplarily, the similarity threshold is 80%, if the similarity of the water environment parameter corresponding to a certain adjacent similar stress time reaches the similarity threshold, then the adjacent similar stress time is in the same water environment, otherwise the adjacent similar stress time is in different water environments.

[0030] It is important to know that when the stress of two components is similar at a certain point in time, if the water environment parameters at that point in time are also similar, it means that the two components have similar force responses in the same water environment. On the contrary, if the water environment parameters of two components are different at a time point with similar stress, it means that the two components can show similar stress states in different water environments. In other words, even in different water environments, the two components can still reach similar stress levels.

[0031] The duration of similar force-bearing times in the same water environment is obtained, and the number of similar force-bearing times in different water environments is counted.

[0032] It should be pointed out that the duration of similar stress time in the same water environment reflects the length of time that the two components maintain similar stress states under the same external load conditions. A longer similar stress time period indicates that the two components can maintain similar stress distributions for a long time under the same external load conditions, which means that the two components have good consistency and stability in design. The number of similar stress times in different water environments reflects the frequency with which the two components exhibit similar stress states under different working conditions.

[0033] The distribution state of the water environment corresponding to the similar stress time of each candidate component group with similar stress is used to evaluate the similar stress representation degree corresponding to each candidate component group with similar stress. The specific evaluation formula is: Where Q represents the similar force characterization degree, t represents the duration of similar force time in the same water environment, T represents the duration of the selected water operation period, x represents the number of similar force times in different water environments, and m represents the number of times existing in the stress time series data.

[0034] It should be noted that by analyzing the stress conditions of two components with similar stress in the same and different water environments, their similar stress characterization can be quantified, thereby evaluating their stress similarity. Only when the two components can show similar stress states in the same and different water environments can the combined structure maintain good performance and safety under various working conditions. Therefore, the evaluation results based on the similar stress characterization can provide a reliable basis for screening the potential component group for merging to achieve lightweight structural design.

[0035] The similar force characterization degree corresponding to each similar force candidate component group is compared with the set characterization degree threshold. Exemplarily, the characterization degree threshold is 0.7, thereby selecting the similar force candidate component group whose similar force characterization degree reaches the characterization degree threshold as the similar force component group.

[0036] The selected similar load-bearing component groups are compared to identify whether there are identical components. If some similar load-bearing component groups have identical components, these similar load-bearing component groups are removed to form similar load-bearing component groups.

[0037] In the example where (A, B), (A, C), (B, C), (B, E), and (D, E) are the similar force-bearing alternative component groups, assuming that the selected similar force-bearing component groups are (A, B), (A, C), (B, C), and (D, E), then since (A, B), (A, C), and (B, C) have the same components, (A, B), (A, C), and (B, C) are removed to form the similar force-bearing component group (A, B, C).

[0038] Furthermore, the following process is used to screen out the potential component groups for merging: locate the position of each component in the similar force-bearing component group on the main structure of the demonstration ship, thereby identifying whether the components in the similar force-bearing component group are adjacent to each other; if the components in a similar force-bearing component group are adjacent to each other, then the similar force-bearing component group is used as a valid component group.

[0039] The material properties of each component in the effective component group are obtained respectively to identify whether the material properties are consistent. If the material properties of each component in a certain effective component group are consistent, the effective component group is recorded as a component group with merging potential.

[0040] It should be explained that after identifying similar load-bearing component groups, they cannot be merged blindly. The following two key factors must be considered comprehensively: location proximity and consistency of material properties. This is because in actual structural design, if two components are far apart or have inconsistent material properties, the merging operation will face technical and engineering challenges. Specifically, when two components are far apart, due to the large physical distance, merging the two components will require crossing other structures, increasing the difficulty and risk of construction; when the material properties of the two components are inconsistent, only one material can be selected in the merged component, which will lead to a difficult choice. Selecting a material with lower performance may affect the strength and durability of the overall structure; while selecting a material with higher performance may lead to material waste and increased costs. Therefore, after identifying similar load-bearing component groups, their location proximity and consistency of material properties must be comprehensively considered to make a reasonable merging decision. Only when the two components are close enough in space and have similar material properties can the merged structure be guaranteed to achieve the best performance, safety and economy.

[0041] A lightweight model of the demonstration ship structure after component merging is built based on the combined potential component group, and the extreme performance values ​​of the water environment parameters are extracted from the time series data of the water environment parameters.

[0042] It should be emphasized that when constructing the lightweight model of the demonstration ship structure after the components are merged, it is necessary to ensure that the geometric dimensions, total weight, and external contours of the model are highly consistent with the actual demonstration ship to ensure the accuracy and representativeness of the model.

[0043] In the optimized implementation of the above operation, the extreme performance values ​​of the water environment parameters are extracted according to the following process: the maximum value of each water environment parameter is extracted from the water environment parameter time series data to form the extreme performance value of each water environment parameter.

[0044] As an explanation for the above optimization implementation, it is necessary to select extreme water conditions when simulating the water environment of the merged demonstration ship model. This is because extreme water conditions can impose the most severe test on the ship structure, thereby more significantly revealing the ship's operating performance after the components are merged. Since the selected water operation period is based on the time period with a high probability of severe water environment in history, the water environment parameters collected during this period can effectively reflect the extreme water environment. Therefore, the extreme values ​​extracted from the water environment parameter time series collected during the water operation period can be used as the extreme performance values ​​of the water environment parameters. When the water environment parameters are water flow velocity, wave impact frequency and wind speed, these parameters are usually positively correlated with the severity of the water environment, that is, the larger the parameter value, the worse the water environment. Therefore, when extracting the maximum value, the maximum value is extracted to reflect the worst water environment conditions. When the water environment parameters contain water temperature, the change of water temperature may have a complex impact on the water environment. Extreme high temperature or low temperature may lead to a severe water environment. For example, high temperature may aggravate corrosion and low temperature may cause ice. At this time, the extracted water environment parameter maximum value should include the maximum value and the minimum value.

[0045] The lightweight model of the demonstration ship structure is simulated under extreme performance values ​​of the water environment parameters, and the deformation and stress distribution data are collected by focusing on the merged component area during the simulation.

[0046] Specifically, the lightweight model of the demonstration ship structure is run under the extreme performance values ​​of the water environment parameters to simulate the following process: the extreme performance value combination of each water environment parameter is extracted to form a plurality of water environment simulation groups.

[0047] The formed water environment simulation group is used to build a water environment in the simulation software, and then the lightweight model of the demonstration ship structure is placed in the built water environment for operation simulation.

[0048] More specifically, focusing on the merged component area to collect deformation and stress distribution data during the simulation process is implemented as follows: virtual sensors are evenly arranged around the boundaries of the merged component area to collect deformation displacement and stress data of each layout point during the simulation process.

[0049] It needs to be explained that virtual sensors are deployed on the four sides of the merged component area because the four sides are the connection interfaces between the merged component and the adjacent structures. These areas usually bear greater stress concentration and complex load transfer. Therefore, deploying virtual sensors on the four sides to collect deformation, displacement and stress data can better capture the simulation performance of the merged component area.

[0050] It is further necessary to explain that the deformation displacement and stress data are collected in the simulation performance of the merged components because there are usually certain gaps or connection interfaces between the components in the splicing of two separate components. These gaps can serve as buffer areas for stress release. When external loads (such as wave impact, water flow pressure, etc.) act, part of the energy can be dispersed through these gaps, reducing the direct impact on individual components. After the components are merged, the gaps in the middle are eliminated to form a continuous overall structure. Although this can improve the overall rigidity and strength of the structure, it also means that the original stress release path is lost. The impact force cannot be dispersed through the gap, but is directly transmitted to the merged structure, which makes the merged component area prone to deformation and uneven stress distribution (i.e., local stress concentration).

[0051] See also Figure 3 As shown in the figure, the feasibility of component merging is evaluated based on the deformation and stress distribution data of the merged component area. The specific implementation is as follows: the deformation displacement of the merged component area corresponding to the same water environment simulation group at each layout point is compared with the set allowable deformation displacement through the expression The deformation characterization index DI is calculated, where s i It represents the deformation displacement of the merged component area at the i-th layout point, i represents the layout point number, i=1,2,......,n, n represents the number of layout points, s0 represents the allowable deformation displacement, ε represents the sudden change of deformation, and e represents the natural constant.

[0052] Furthermore, the sudden deformation degree is obtained as follows: the deformation displacement of the corresponding merged component area of ​​the same water environment simulation group at adjacent layout points is subtracted and compared with the set critical deformation displacement difference. For example, the critical deformation displacement difference is 2 cm. If the deformation displacement difference of adjacent layout points reaches the limited deformation displacement difference, it is identified that the adjacent layout points have a sudden deformation change.

[0053] The number of adjacent layout points with sudden deformation is summed up and divided by the total number of layout points to obtain the sudden deformation degree.

[0054] It should be noted that the allowable deformation displacement mentioned above can be obtained from the structural instructions of the demonstration ship.

[0055] The stress data of the corresponding combined component area at each layout point of the same water environment simulation group are compared to extract the maximum stress and minimum stress, and the distance between the layout point where the maximum stress is located and the layout point where the minimum stress is located is obtained, and then the formula is used to calculate the stress data of the corresponding combined component area at each layout point. Calculate the stress distribution uneven index UI, where F max 、F min They represent the maximum stress and the minimum stress respectively, l represents the distance between the layout point where the maximum stress is located and the layout point where the minimum stress is located, and l0 represents the length of the surrounding boundaries of the merged component area.

[0056] The deformation characterization index and stress distribution uneven index of the merged component area corresponding to the same water environment simulation group are weighted averaged to obtain the risk index of the merged component area under each water environment simulation group.

[0057] In the above exemplary embodiment, the weight factors corresponding to the deformation characterization index and the stress distribution unevenness index may be 0.6 and 0.4.

[0058] The risk index of the merged component area under each water environment simulation group is compared with the set allowable risk index, and the water environment simulation group with a risk index smaller than the allowable risk index is selected as the valid water environment simulation group.

[0059] The proportion of the effective water environment simulation group is counted and compared with the set standard-reaching proportion. For example, the standard-reaching proportion is 0.8. If the proportion of the effective water environment simulation group reaches the standard-reaching proportion, the merger of the assessment components is feasible, otherwise the merger of the assessment components is not feasible.

[0060] The structural lightweight design of the demonstration ship is carried out according to the evaluation results of the feasibility of component merging. The specific process is as follows: from the feasibility evaluation results of each potential merging component group corresponding to the main structure of the demonstration ship after the merging simulation, the potential merging component group that is evaluated as feasible is selected for component merging design.

[0061] The present invention collects stress and water environment parameters of each component of the hull structure during the operation of the methanol-powered bulk cargo demonstration ship, thereby screening out component groups with merging potential, and building a lightweight model of the combined components to conduct simulation tests in different water environments, from which feasible merging potential component groups are selected for actual design, which can achieve structural lightweighting while ensuring the safety of hull operation. This not only reduces the amount of materials and construction costs, improves resource utilization efficiency, but also reduces the failure risk of the connection parts by reducing the number of connection points, and improves the safety and reliability of the hull.

[0062] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for lightweight structural design of a methanol-powered bulk carrier, characterized in that: The following steps are involved: Count the components of the main structure of the methanol-powered bulk cargo demonstration ship, install stress sensors on each component, and deploy water environment collection terminals outside the hull; During the selected water area operation period, stress sensors are used to collect stress of each component of the demonstration ship in real time, and water environment parameters are recorded synchronously through the water environment collection terminal, thereby generating stress time series data of each component and water environment parameter time series data; Based on the stress time series data of each component and the time series data of the water environment parameters, similar stress component groups are identified, and potential component groups for merging are selected from them; A lightweight model of the demonstration ship structure after component merging is built based on the combined potential component group, and the extreme performance values ​​of the water environment parameters are extracted from the water environment parameter time series data; The lightweight model of the demonstration ship structure is simulated under extreme performance values ​​of water environment parameters, and the deformation and stress distribution data are collected by focusing on the merged component area during the simulation; Evaluate the feasibility of component merging based on deformation and stress distribution data in the merged component area; The structural lightweight design of the demonstration ship is carried out based on the evaluation results of the feasibility of component merging.

2. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 1, characterized in that: The identification of the similar force-bearing component group refers to the following process: The components are grouped in pairs to form several component groups, and the stress difference of the stress time series data of each component group is calculated at the same time, and then compared with the set critical stress difference. If the stress difference of a component group at a certain time is less than or equal to the critical stress difference, the component group is used as a candidate component group with similar stress, and the time is used as the similar stress time; Extract water environment parameters corresponding to similar stress times from water environment parameter time series data; The number of similar stress-bearing times captured by each similar stress-bearing candidate component group in the stress time series data is counted, and the water environment distribution state corresponding to the similar stress-bearing time is identified based on the water environment parameters corresponding to the similar stress-bearing time, wherein the water environment distribution state includes the duration of the similar stress-bearing time in the same water environment and the number of similar stress-bearing times in different water environments; The distribution state of the water environment corresponding to the similar stress time of each candidate component group with similar stress is used to evaluate the similar stress representation degree corresponding to each candidate component group with similar stress. The specific evaluation formula is: Where Q represents the similar force characterization degree, t represents the duration of similar force time in the same water environment, T represents the duration of the selected water operation period, x represents the number of similar force times in different water environments, and m represents the number of times existing in the stress time series data; Compare the similar force characterization degree corresponding to each similar force candidate component group with the set characterization degree threshold, thereby selecting the similar force candidate component group whose similar force characterization degree reaches the characterization degree threshold as the similar force component group; The selected similar load-bearing component groups are compared to identify whether there are identical components. If some similar load-bearing component groups have identical components, these similar load-bearing component groups are removed to form similar load-bearing component groups.

3. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 2, characterized in that: The process of identifying the distribution state of the water environment corresponding to similar force-bearing time is as follows: The water environment parameters corresponding to adjacent similar force-bearing times are similarly calculated to obtain the water environment parameter similarity, and compared with the set similarity threshold. If the water environment parameter similarity corresponding to adjacent similar force-bearing times reaches the similarity threshold, the adjacent similar force-bearing times are in the same water environment, otherwise the adjacent similar force-bearing times are in different water environments; The duration of similar force-bearing times in the same water environment is obtained, and the number of similar force-bearing times in different water environments is counted.

4. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 1, characterized in that: The process of screening out the potential component group for merging is as follows: Locate the position of each component in the similar force-bearing component group on the main structure of the demonstration ship, thereby identifying whether the components in the similar force-bearing component group are adjacent to each other; if the components in a certain similar force-bearing component group are adjacent to each other, then the similar force-bearing component group is regarded as a valid component group; The material properties of each component in the effective component group are obtained respectively to identify whether the material properties are consistent. If the material properties of each component in a certain effective component group are consistent, the effective component group is recorded as a potential component group for merging.

5. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 1, characterized in that: The extraction of extreme values ​​of water environment parameters is described in the following process: The maximum value of each water environment parameter is extracted from the time series data of water environment parameters to form the extreme performance value of each water environment parameter.

6. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 5, characterized in that: The lightweight model of the demonstration ship structure is run under the extreme performance values ​​of the water environment parameters to simulate the following process: The extreme performance value combinations of each water environment parameter are extracted to form several water environment simulation groups; The formed water environment simulation group is used to build a water environment in the simulation software, and then the lightweight model of the demonstration ship structure is placed in the built water environment for operation simulation.

7. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 6, characterized in that: The focusing and merging of component regions to collect deformation and stress distribution data during the simulation process is implemented as follows: Virtual sensors are evenly arranged on the four sides of the merged component area to collect deformation displacement and stress data of each arrangement point during the simulation process.

8. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 7, characterized in that: The feasibility of merging the evaluation components is described in the following process: The deformation displacement of the corresponding combined component area at each layout point of the same water environment simulation group is compared with the set allowable deformation displacement through the expression The deformation characterization index DI is calculated, where s i represents the deformation displacement of the merged component area at the i-th layout point, i represents the layout point number, i=1,2,......,n, n represents the number of layout points, s0 represents the allowable deformation displacement, ε represents the sudden change of deformation, and e represents the natural constant; The stress data of the corresponding combined component area at each layout point of the same water environment simulation group are compared to extract the maximum stress and minimum stress, and the distance between the layout point where the maximum stress is located and the layout point where the minimum stress is located is obtained, and then the formula is used to calculate the stress data of the corresponding combined component area at each layout point. Calculate the stress distribution uneven index UI, where F max 、F min They represent the maximum stress and the minimum stress respectively, l represents the distance between the layout point where the maximum stress is located and the layout point where the minimum stress is located, and l0 represents the length of the surrounding boundaries of the merged component area; The deformation characterization index and stress distribution unevenness index of the merged component area corresponding to the same water environment simulation group are weighted averaged to obtain the risk index of the merged component area under each water environment simulation group; Compare the risk index of the merged component area under each water environment simulation group with the set allowable risk index, and select the water environment simulation group with a risk index less than the allowable risk index as the valid water environment simulation group; The proportion of the effective water environment simulation group is counted and compared with the set standard proportion. If the proportion of the effective water environment simulation group reaches the standard proportion, the merger of the assessment components is feasible, otherwise the merger of the assessment components is not feasible.

9. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 8, characterized in that: The sudden change in deformation is obtained as follows: The deformation displacement of the corresponding merged component area of ​​the same water environment simulation group at adjacent layout points is subtracted and compared with the set critical deformation displacement difference. If the deformation displacement difference of the adjacent layout points reaches the limited deformation displacement difference, it is identified that the adjacent layout points have a sudden deformation change; The number of adjacent layout points with sudden deformation is summed up and divided by the total number of layout points to obtain the sudden deformation degree.

10. A method for lightweight design of a methanol-powered bulk carrier as claimed in claim 8, characterized in that: The structural lightweight design of the demonstration ship based on the evaluation results of the feasibility of component merging is as follows: From the feasibility evaluation results of each potential merging component group corresponding to the main structure of the demonstration ship after the merging simulation, a feasible potential merging component group is selected for component merging design.

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