A full ship stress distribution inversion method based on limited strain monitoring data

Abstract

The application discloses a kind of whole ship stress distribution inversion methods based on limited strain monitoring data, it is related to ship structure stress monitoring field, the method includes the following steps: establishing whole ship finite element model, initialization configuration finite element model;The calculation of ship free vibration mode is carried out, and according to the vibration mode selection basis mode;Monitoring equipment is arranged at the ship structure capable of reflecting the total longitudinal deformation characteristics of ship body;Monitoring data on monitoring equipment is collected, and stress inversion calculation is carried out based on modal superposition method.The application can calculate the weight coefficient of each stage basis mode in actual response of ship based on limited number of local monitoring equipment, and the stress response of uninstalled measuring point part is inverted, the real-time monitoring of whole ship structure stress response is realized, the ship structure stress inversion technology can provide guidance for the structural safety inspection and fatigue analysis of ship, and provide strong technical support for ensuring the safe operation and long-term stability of ship.

Description

Technical Field

[0001] This invention relates to the field of ship structural stress monitoring, and in particular to a method for inverting the stress distribution of the entire ship based on finite strain monitoring data. Background Technology

[0002] With the continuous development of marine resources, the environmental loads faced by ships and marine engineering structures are becoming increasingly complex. Different types of ships are widely used in tourism transportation, oil and gas field development, and offshore wind power, among other fields. Reliability and safety are fundamental to the successful completion of these operations. After multiple voyages, the hull structure inevitably suffers from defects such as corrosion, cracks, and deformation, leading to a decrease in load-bearing capacity. Under the influence of external loads such as strong winds and waves, the hull structure is at risk of plastic deformation or fracture. Therefore, real-time stress monitoring and health assessment of the hull structure, issuing early warnings before plastic deformation or fracture occurs, and promptly reminding crew members to take evasive action to ensure the safety of the hull structure, are of great guiding significance for the use, maintenance, repair, and construction of ships. Effective and real-time monitoring of ship structural stress can bring greater economic benefits and more comprehensive safety assurance. At the same time, the load spectra currently used are relatively outdated, and with the continuous changes in global climate in recent years, the applicability of previous standards urgently needs to be verified. Collecting response data through monitoring equipment will help establish more reasonable standards that are more adapted to current realities. Hull stress monitoring systems are the primary method for real-time monitoring of ship structural conditions. These systems acquire data from sensors installed on the hull, providing real-time information on acceleration response and local strain response. They are mainly used for real-time monitoring of important hull structures, sensitive areas, and key components, as well as online assessment of hull structural strength.

[0003] However, ship stress monitoring equipment can only provide very limited stress monitoring data. To achieve accurate stress measurement across the entire ship, a large number of sophisticated stress sensors need to be deployed. The high cost of stress sensors and the limitations of ship structural space make this impossible. Relying solely on monitoring equipment cannot monitor all dangerous structural areas of the ship in real time, posing challenges to ship health monitoring. To achieve full-ship stress calculation, against the backdrop of intelligent ship development, numerous calculation software programs have been developed based on theories such as linear wave theory and three-dimensional potential flow theory, including WAMIT, Hydrostar, and COMPASS-WALCS. These software programs play a crucial role in the design, manufacturing, and safety verification of ships and marine structures. However, these calculations all require knowledge of the sea state conditions during ship navigation and cannot be directly embedded into the monitoring system, making it difficult to meet the timeliness requirements of intelligent navigation.

[0004] Therefore, those skilled in the art are dedicated to developing a method for inverting the stress distribution of the entire ship based on finite strain monitoring data. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is that due to the limitations of the spatial location of the ship structure and the cost of monitoring equipment, it is impossible to install monitoring equipment at every dangerous location of the ship to monitor the stress response of each component of the ship, which brings great difficulties to the health monitoring and safety assessment of the ship.

[0006] To achieve the above objectives, this invention provides a method for inverting the stress distribution of an entire ship based on finite strain monitoring data, the method comprising the following steps:

[0007] S101: Establish the finite element model of the entire ship and initialize the configuration of the finite element model;

[0008] S103: Calculate the free vibration modes of the ship and select the basic modes based on the mode shapes;

[0009] S105: Install monitoring equipment for monitoring hull stress at hull structures that can reflect the overall longitudinal deformation characteristics of the hull.

[0010] S107: Collect monitoring data from the monitoring equipment and perform stress inversion calculation based on the modal superposition method.

[0011] Furthermore, in step S101, a finite element model of the ship is established using the structural finite element analysis method. In the finite element model, the plate and keel structure are simulated using quadrilateral and / or triangular plate shell elements, and the longitudinal ribs and crossbeams are simulated using two-node beam elements.

[0012] Furthermore, in step S101, when initializing the configuration of the finite element model, the corresponding structural material properties in the finite element model are assigned based on the actual ship structural material properties, and the ship weight distribution and boundary conditions are adjusted.

[0013] Furthermore, in step S103, the basic modes include multiple vertical bending modes, multiple torsional modes, and a first-order transverse bending mode.

[0014] Furthermore, the multi-order vertical bending mode includes a first-order vertical bending mode, a second-order vertical bending mode, and a third-order vertical bending mode; the multi-order torsional mode includes a first-order torsional mode, a second-order torsional mode, and a third-order torsional mode.

[0015] Furthermore, in step S105, multiple monitoring points are deployed on the ship, and the monitoring equipment is deployed at these monitoring points, which are distributed at the bow, midships, and stern of the ship. The monitoring points are located near the waterline, on the deck, and on the side of the ship, with parameter L representing the length of the vessel.

[0016] Furthermore, in step S105, the monitoring device employs a long baseline sensor, which measures and acquires the longitudinal stress response at the monitoring point.

[0017] Furthermore, the monitoring point with the most severe longitudinal response is selected as the verification point. The relative error between the measured stress and the inverted stress at the verification point is calculated, and the relative error is used as the evaluation criterion for the reliability of the inversion results.

[0018] Furthermore, in step S107, when performing stress inversion calculation using the modal superposition method, the following calculation formula is used:

[0019]

[0020] Where σ is the actual stress response, σ i Let q be the stress response of the i-th fundamental mode. i denoted as the weight coefficient of the i-th fundamental mode, and n is the number of fundamental modes.

[0021] Further, in step S107, the weighting coefficients of each basic mode at the monitoring point are obtained by solving a system of linear equations, which are:

[0022] q=(σ monitor ) -1 σ real

[0023] Where q is the weight coefficient matrix of the basic mode, and σ monitor This is the stress monitoring value matrix at monitoring points in the modal vibration mode, σ real This is the matrix of measured stress values ​​at the monitoring points.

[0024] In a preferred embodiment of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention can decouple the vibrations of a ship by modal superposition. By linearly superimposing the stress distributions of each mode with their weighting coefficients, the stress response of the entire hull can be obtained. Based on a limited number of local monitoring devices, real-time monitoring of the stress response of the entire ship structure can be achieved.

[0026] 2. This invention can provide guidance for the structural safety inspection and fatigue analysis of ships, and provide strong technical support for ensuring the safe operation and long-term stability of ships;

[0027] 3. This invention pre-stores all the basic data required for stress inversion into the calculation program in the form of a database. During the calculation process, the solution of the equations and the calculation of stress only need to call the data inside the calculation program, without having to read the data from the finite element model. The calculation process does not need to interact with the finite element model, and can achieve real-time calculation within 1 second. This allows the stress inversion program to be smoothly embedded into the ship monitoring system and meets the requirements of computational timeliness during intelligent ship navigation with relatively small computer resources. It can provide support for real-time monitoring of ship structures and assist in early warning of ship structural risks.

[0028] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0029] Figure 1 This is a flowchart of the whole-ship stress distribution inversion method according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the full-ship finite element model according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the basic modal vibration modes of an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the monitoring equipment layout scheme according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the stress inversion result time history curve in an embodiment of the present invention. Detailed Implementation

[0034] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0035] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0036] like Figure 1As shown in the embodiment of the present invention, a method for inverting the stress distribution of a large-opening container ship based on finite strain monitoring data is proposed. This method involves establishing a stress estimation model for the entire structure of the large-opening container ship based on the modal superposition method and the finite element model. Using measured data from a finite number of stress monitoring devices installed on the ship, the stress levels of the remaining key structural areas without installed sensors are calculated and estimated. The method includes the following steps:

[0037] S1: Establish the finite element model of the entire ship and initialize the configuration of the finite element model.

[0038] In this embodiment, the structural finite element analysis method is used to establish the finite element model of the ship. In the finite element model, the plate and keel structure are simulated using quadrilateral and / or triangular plate shell elements, and the longitudinal ribs and crossbeams are simulated using two-node beam elements.

[0039] When initializing the finite element model, the corresponding structural material properties in the finite element model are assigned based on the actual ship structure material properties, and the ship weight distribution and boundary conditions are adjusted.

[0040] S2: Calculate the free vibration modes of the ship and select the basic mode based on the vibration mode shape.

[0041] The free vibration modes of the ship were calculated using the finite element method software FEMAP, with Lanczos as the solution method. Within the free vibration range of 0-50 Hz, based on the mode shapes, the selected fundamental modes included multiple vertical bending modes, multiple torsional modes, and a first-order transverse bending mode. Specifically, the multiple vertical bending modes included a first-order, second-order, and third-order vertical bending mode; the multiple torsional modes included a first-order, second-order, and third-order torsional mode.

[0042] S3: Install monitoring equipment for monitoring hull stress at hull structures that can reflect the overall longitudinal deformation characteristics of the hull.

[0043] The purpose of this invention is to invert the total longitudinal stress of a ship. Therefore, several monitoring points that can reflect the total longitudinal deformation characteristics of the ship are selected at the hull structure, and monitoring equipment is deployed at these points. The monitoring points are distributed at the bow, midships, and stern of the ship. The location of the monitoring points (where L is the length of the ship) includes the vicinity of the waterline, the deck, and the side of the ship.

[0044] The monitoring equipment uses long-baseline sensors to measure and collect the longitudinal stress response of the monitoring points. The monitoring point with the most severe overall longitudinal response is selected as the verification point. The relative error between the measured stress and the inverted stress at the verification point is calculated, and the relative error is used as the evaluation criterion for the reliability of the inversion results.

[0045] S4: Collect monitoring data from the monitoring equipment and perform stress inversion calculations based on the modal superposition method.

[0046] Based on the forced vibration principle of multi-degree-of-freedom systems, assuming that the displacement deformation of a structure can be composed of a finite number of mode shapes through linear superposition, then by selecting appropriate basic mode linear superposition, the actual response state of the ship under different sea conditions can be obtained.

[0047] In this embodiment, the following calculation formula is used when performing stress inversion calculation using the modal superposition method:

[0048]

[0049] Where σ is the actual stress response, σ i Let q be the stress response of the i-th fundamental mode. i denoted as the weight coefficient of the i-th fundamental mode, and n is the number of fundamental modes.

[0050] The weighting coefficients q of each basic mode at the monitoring point can be obtained by solving a system of linear equations, which are:

[0051] q=(σ monitor ) -1 σ real

[0052] Where q is the weight coefficient matrix of the basic mode, and σ monitor This is the stress monitoring value matrix at monitoring points in the modal vibration mode, σ real This is the matrix of measured stress values ​​at the monitoring points.

[0053] The stress response at the predicted point can be obtained by linearly superimposing the modes according to the modal weighting coefficients.

[0054] σ=σ prediction q.

[0055] Compared with existing technologies, the whole-ship stress distribution inversion method based on finite strain monitoring data provided in this invention has the following advantages:

[0056] 1. Due to limitations in the spatial location of ship structures and the cost of monitoring equipment, the number of sensors in existing technologies is limited, making it impossible to install monitoring equipment at every dangerous location on the ship and monitor the stress response of every component. This poses a significant challenge to ship health monitoring and safety assessment. This invention can calculate the weighting coefficients of each basic mode in the actual response of the ship based on stress monitoring data from a limited number of measuring points. By linearly superimposing the basic modal stresses of the corresponding region in the database at locations where no measuring points are installed, the stress response at the current location can be obtained.

[0057] 2. Based on the principles of structural mechanics, this invention addresses the vibrations of a ship navigating in waves, caused by wave loads. These vibrations consist of various modes of different orders. The modal superposition method decouples these vibrations, obtaining the stress response of the entire hull by linearly superimposing the stress distributions of each mode with their weighting coefficients. This allows for real-time monitoring of the stress response of the entire ship structure using a limited number of local monitoring devices. The ship structure stress inversion technology provided by this invention can guide ship structural safety inspections and fatigue analysis, possessing significant application value and practical importance in the field of ship structural monitoring and analysis. It provides strong technical support for ensuring the safe operation and long-term stability of ships.

[0058] 3. Addressing the issue that existing calculation software cannot be directly embedded into monitoring systems and suffers from long computation times, failing to meet the timeliness requirements of intelligent ship navigation, the method provided in this invention only requires access to the stress monitoring values ​​of each measuring point in the monitoring system during the inversion process. It does not require interaction with finite element software. By pre-storing all the basic data required for stress inversion into the calculation program in database form, the solution of equations and the calculation of stress only require calling data from within the calculation program, eliminating the need to read data from the finite element model. The calculation process does not require interaction with the finite element model, enabling real-time calculations within 1 second. This allows the stress inversion program to be smoothly embedded into the ship monitoring system, meeting the timeliness requirements of intelligent ship navigation with relatively small computer resources. It can support real-time monitoring of ship structures and assist in early warning of ship structural risks.

[0059] The present invention will now be described in detail with reference to preferred embodiments.

[0060] The purpose of this invention is to establish a stress estimation model for the entire structure of a large-aperture container ship based on the modal superposition method and the finite element model. By using measured data from a limited number of stress monitoring devices installed on the ship, the stress levels of the main critical structural areas where sensors are not installed can be calculated and estimated.

[0061] In this embodiment, the stress inversion test is conducted on a 14,000 TEU container ship, which is 330 meters long, 51 meters wide, and 30 meters deep. The test sea state is 14.4m draft with wave state, and the ship speed is 19.7 knots.

[0062] like Figure 1 As shown, the preferred embodiment of the present invention provides a method for inverting the stress distribution of the entire ship based on finite strain monitoring data, which includes the following steps:

[0063] Step 1: Establish the finite element model of the entire ship.

[0064] like Figure 2As shown, in this embodiment, based on the structural drawings of the 14,000 TEU container ship, a finite element model of the 14,000 TEU container ship was established using structural finite element analysis software such as Femap. This finite element model is a 1:1 full-size model. The plate and keel structure are simulated using quadrilateral and triangular plate shell elements, while the longitudinal ribs and crossbeams are simulated using two-node beam elements. Based on the material properties of the actual ship structure, the corresponding structural materials are assigned values, and the ship's weight distribution is adjusted and boundary conditions are set.

[0065] Step 2: Calculate and select the fundamental mode.

[0066] In this embodiment, the finite element method software Femap was used to calculate the free vibration modes of the ship. The Lanczos method was adopted for the calculation. Within the free vibration range of 0-50 Hz, based on the mode shape, the first to third order vertical bending, the first to third order torsion, and the first order transverse bending were selected as the basic modes. The schematic diagram of the basic mode shape of the 14,000 TEU container ship is shown below. Figure 3 As shown.

[0067] Step 3: Deploy monitoring equipment on the actual ship.

[0068] The purpose of this invention is to invert the total longitudinal stress of a ship. Therefore, several monitoring points that can reflect the total longitudinal deformation characteristics of the ship are selected at the hull structure. The selection process refers to Chapter 21 of Part VIII of the "Rules for Classification of Steel Seagoing Ships," which states that "for container ships with a length greater than 180m, the following parts should be monitored in detail: the total longitudinal stress at L / 4 from the midships, including the port and starboard sides; the longitudinal stress near the bottom (L / 2) of the midships, including the port and starboard sides; etc." Based on this principle, this embodiment deploys a total of 8 long-baseline sensors at the actual ship structure, distributed at the bow 1 / 4L, midships, and stern 1 / 4L, including near the waterline, deck, and sides, to better reflect the total longitudinal deformation characteristics of the ship.

[0069] In this embodiment, the stress monitoring device is a long baseline strain sensor with a data transmission frequency of 10Hz, and the stress refers to unidirectional stress in the ship's length direction.

[0070] like Figure 4 As shown in the schematic diagram of the monitoring equipment layout scheme for a 14,000 TEU container ship in this embodiment, measuring points are arranged at the bow 1 / 4L, midship and stern 1 / 4L of the ship, including a total of 8 monitoring points near the waterline, on the deck and on the side, which are marked as: G1, G2, G3, G4, G5, G6, G7 and G8 respectively.

[0071] Meanwhile, in order to verify the reliability of the stress inversion results of the present invention, G2 was selected as the verification point, and the relative error between the measured stress and the inverted stress at G2 was used as the evaluation criterion for the reliability of the inversion results.

[0072] The reason for choosing point G2 as the verification point is that G2 is located amidships, where the longitudinal response is the most severe and is one of the areas of greatest concern for ship structural safety. The good inversion effect in this area is more representative and can prove the reliability of the stress inversion method in this embodiment.

[0073] The distribution of each sensor rib is shown in Table 1. Based on these 8 sensors, the stress response inversion of the entire ship can be completed.

[0074] Table 1. Distribution of rib locations for each sensor

[0075] Sensor Name Sensor tag rib Long baseline sensor 1 G1 FR95 Long baseline sensor 2 G2 FR221 Long baseline sensor 3 G3 FR313 Long baseline sensor 4 G4 FR221 Long baseline sensor 5 G5 FR221 Long baseline sensor 6 G6 FR221 Long baseline sensor 7 G7 FR221 Long baseline sensor 8 G8 FR221

[0076] Step 4: Perform stress inversion calculations.

[0077] For the modal superposition method, the linear superposition of appropriate basic modes can obtain the actual response state of the ship under different sea states, and its mechanical principle is as follows.

[0078] The forced vibration equation for a multi-degree-of-freedom system is:

[0079]

[0080] In the formula, M, C, and K represent the mass matrix, damping matrix, and stiffness matrix of the structure, respectively, and F is the external load on the structure.

[0081] This equation is usually a coupled equation, which can be decoupled by regular coordinate transformation, thereby reducing the workload of solving the equation.

[0082] Assume that the displacement and deformation of the structure can be composed of a finite number of mode shapes through linear superposition, that is:

[0083] x=Φq=φ1q1+φ2q2+... (2)

[0084] The dominant modal shape of the structure is represented by q, which is a component of the generalized canonical coordinate.

[0085] Therefore, the forced vibration equation of a multi-degree-of-freedom structure can be written as:

[0086]

[0087] Define the generalized mass matrix M * C * K * The forced vibration equation of the decoupled multi-degree-of-freedom system is then:

[0088]

[0089] Therefore, if the generalized coordinate vector q of each mode is obtained, the actual response of the entire ship can be obtained by linearly superimposing all the response modes.

[0090]

[0091] Based on the measured stress values ​​at the actual ship monitoring points and the stress values ​​at the monitoring points extracted from the modal vibration modes, the weighting coefficient q for each mode is obtained.

[0092] q=(σ monitor ) -1 σ real (6) The stress response at the prediction point can be obtained by linearly superimposing the modal weighting coefficients q.

[0093] σ=σ prediction q (7)

[0094] Based on the above principles, and combined with the finite element model of the hull, a digital twin model for monitoring the stress of the hull structure can be established.

[0095] Taking a specific sampling moment of the sea state test as an example, a calculation example of stress inversion is presented. Among the stress monitoring points, G1, G3, G4, G5, G6, G7, and G8 are the stress calculation points. G2, the measuring point in the midship area where the stress response is relatively severe, is selected as the verification point to better reflect the reliability of the stress inversion method.

[0096] The stress response at point G2 under the current sea state is obtained by using the stress inversion technique based on the modal superposition method. To invert the stress at G2, the parameter that needs to be solved is the modal weighting coefficient q, which can be calculated using formula (6).

[0097] The basic modal stress matrix A of each stress monitoring point (including G2) corresponds to σ in formula (6). monitor As shown in Table 2, different rows in matrix A represent the stress values ​​corresponding to each measuring point, and different columns represent the stress values ​​corresponding to each mode, which are used for subsequent calculations.

[0098] Table 2. Basic Modal Stress Matrix A (MPa) at Each Stress Monitoring Point

[0099]

[0100] The target matrix B is the stress response at each stress monitoring point at the current moment (corresponding to σ in formula (6)). real The target matrix B is shown in Table 3.

[0101] Table 3 Stress response matrix at each measuring point (B)

[0102] Monitoring point sign Stress (MPa) G1 60.22 G3 47.24 G4 43.19 G5 59.66 G6 44.47 G7 27.83 G8 14.06

[0103] The linear equation system can be solved according to formula (6) to obtain the weight coefficients X of each basic mode (corresponding to q in formula (6)) as shown in Table 4. Each coefficient represents the proportion of different basic modes. The actual response of the ship can be obtained by adding the different basic modes according to the proportion.

[0104] Table 4 Weighting coefficients for each basic mode X

[0105] basic mode Weighting coefficient First-order vertical bend -2.35 Second-order vertical bend -0.21 Third-order vertical bend -1.45 First-order torsion -1.05 Second-order torsion -0.39 Third-order torsion -0.28 First-order horizontal bend -0.20

[0106] The basic modal stress matrix A' of G2 (corresponding to σ in formula (7)) prediction As shown in Table 5.

[0107] Table 5. G2 Basic Modal Stress Matrix A' (MPa)

[0108]

[0109] According to formula (7), the basic modal stress of the measuring point G2 is linearly superimposed using the weighting coefficients in Table 2. The stress value B' of G2 at the current moment can be obtained by inversion from A'X = B' (corresponding to σ in formula (7), i.e., the stress inversion result), which is B' = 56.50 MPa. According to the monitoring equipment data, the actual stress response at G2 at the current moment is 54.01 MPa. Therefore, the relative error of the stress inversion technique at the current moment is 4.61%.

[0110] Based on the above calculation process, the stress response at point G2 within 5 minutes was inverted, and the resulting stress inversion time-history curve is shown below. Figure 5 As shown, the average relative error of stress inversion at each time point is 4.78% over 5 minutes.

[0111] Actual testing has shown that the stress inversion technique based on the modal superposition method has good inversion results, can calculate the stress response of areas of the ship where no testing equipment is installed, and has good stability in the time domain. It can be applied to the health monitoring and safety assessment of actual ship structures.

[0112] The ship structure stress inversion method provided in this invention has the following advantages:

[0113] 1. It can achieve real-time stress monitoring of various structural parts of a ship without relying on a large number of monitoring devices, and requires less computing resources and has high computing efficiency.

[0114] 2. It can perform real-time monitoring of the stress response of the entire ship structure under different sea conditions with very few monitoring devices, providing some guidance for ship health monitoring and safety assessment.

[0115] Compared with existing technologies, the whole-ship stress distribution inversion method based on finite strain monitoring data provided in this invention has the following advantages in terms of technology, performance indicators, and production implementation:

[0116] 1. Technical advantages: The ship structure stress inversion method provided in this embodiment of the invention can realize the stress response inversion of important structures of the whole ship, provide real-time stress monitoring of the whole ship structure, provide timely early warning of structural failure during navigation, and record the fatigue loss of important ship structures, providing effective guidance for ship operation and maintenance.

[0117] 2. Performance indicators: The hull structure stress inversion method provided in this embodiment of the invention can stably maintain the relative error between the inversion results of the important structural stress of the ship and the actual response value within 10% under different sea conditions.

[0118] 3. Production Implementation: The ship structure stress inversion method provided in this embodiment of the invention does not require the use of additional finite element software during the stress inversion calculation process. It can independently complete the stress inversion based on the database built into the calculation program and combined with stress equipment monitoring data. It can be smoothly embedded into the ship monitoring system without the need to add additional equipment. At the same time, the calculation process requires little computational resources and has strong inversion timeliness, with a delay of no more than 1 second for inversion calculation of real-time stress data.

[0119] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for inverting the stress distribution of a whole ship based on finite strain monitoring data, characterized in that, The method includes the following steps: S101: Establish the finite element model of the entire ship and initialize the configuration of the finite element model; S103: Calculate the free vibration modes of the ship and select the basic modes based on the mode shapes; S105: Install monitoring equipment for monitoring hull stress at hull structures that can reflect the overall longitudinal deformation characteristics of the hull. S107: Collect monitoring data from the monitoring equipment and perform stress inversion calculation based on the modal superposition method; in, In step S103, the basic modes include multiple vertical bending modes, multiple torsional modes, and a first-order transverse bending mode; the multiple vertical bending modes include a first-order vertical bending mode, a second-order vertical bending mode, and a third-order vertical bending mode; the multiple torsional modes include a first-order torsional mode, a second-order torsional mode, and a third-order torsional mode. In step S105, multiple monitoring points are deployed on the ship, and monitoring equipment is deployed at these monitoring points, which are distributed at the bow, midships, and stern of the ship. The monitoring points are located near the waterline, on the deck, and on the side of the ship, and the parameters are... The length of the ship is specified; the monitoring equipment uses a long baseline sensor, which measures and collects the longitudinal stress response at the monitoring point. The method pre-sets the basic data required for inversion in a database, decouples it from the finite element model, and enables real-time calculation and embedding it into the ship monitoring system without relying on online finite element interaction for equation solving and stress calculation.

2. The method as described in claim 1, characterized in that, In step S101, a finite element model of the ship is established using the structural finite element analysis method. In the finite element model, the plate and keel structure are simulated using quadrilateral and / or triangular plate shell elements, and the longitudinal ribs and crossbeams are simulated using two-node beam elements.

3. The method as described in claim 2, characterized in that, In step S101, when initializing the configuration of the finite element model, the corresponding structural material properties in the finite element model are assigned based on the actual ship structural material properties, and the ship weight distribution and boundary conditions are adjusted.

4. The method as described in claim 3, characterized in that, The monitoring point with the most severe longitudinal response is selected as the verification point. The relative error between the measured stress and the inverted stress at the verification point is calculated, and the relative error is used as the evaluation criterion for the reliability of the inversion results.

5. The method as described in claim 4, characterized in that, In step S107, when performing stress inversion calculation using the modal superposition method, the following calculation formula is used: in, For actual stress response, For the first Stress response of the first fundamental mode, For the first The weighting coefficients of the first fundamental mode. The number of basic modes.

6. The method as described in claim 5, characterized in that, In step S107, the weighting coefficients of each basic mode at the monitoring point are obtained by solving a system of linear equations, which are: in, The weight coefficient matrix of the basic mode. This is a matrix of stress monitoring values ​​at monitoring points in the modal vibration mode. This is the matrix of measured stress values ​​at the monitoring points.

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