Whole ship stress distribution inversion method based on finite strain monitoring data

Abstract

The invention discloses a whole ship stress distribution inversion method based on finite strain monitoring data, and relates to the field of ship structure stress monitoring, and the method comprises the following steps: building a whole ship finite element model, and carrying out the initialization configuration of the finite element model; calculating a free vibration mode of the ship, and selecting a basic mode according to a vibration mode; monitoring equipment for monitoring the stress of the ship body is arranged at the ship body structure capable of reflecting the total longitudinal deformation characteristics of the ship body; and collecting monitoring data on the monitoring equipment, and carrying out stress inversion calculation based on a modal superposition method. According to the method, the weight coefficient of each order of basic mode in the actual response of the ship can be calculated based on the limited number of local monitoring equipment, and the stress response of the part without the measuring point is obtained through inversion, so that the real-time monitoring of the stress response of the whole ship structure is realized; the ship body structural stress inversion technology can provide guidance for structural safety inspection and fatigue analysis of the ship, and provides powerful technical support for ensuring safe operation and long-term stability of the ship.

Description

Technical Field

[0001] The invention relates to the field of ship structure stress monitoring, and in particular to a whole-ship stress distribution inversion method based on finite strain monitoring data. Background Art

[0002] With the continuous advancement of marine resource development, the types of 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. Reliability and safety are the basis for ships to successfully complete operations. After multiple stages of navigation, the hull structure will inevitably have defects such as corrosion, cracks, and deformation, resulting in a decrease in carrying capacity. Under the action of external loads such as strong winds and waves, the hull structure is at risk of plastic deformation or fracture damage. Therefore, real-time stress monitoring and health assessment of the hull structure, issuing early warnings before plastic deformation or fracture damage occurs, and timely reminding the crew to take evasive measures 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 complete safety guarantees. At the same time, the currently used standard load spectrum is relatively old. With the continuous changes in the global climate in recent years, the applicability of previous specifications needs to be verified. Collecting response data through monitoring equipment will help establish more reasonable and more suitable specifications for the current actual situation. The hull stress monitoring system is the main method for real-time monitoring of the ship's structural condition. The system obtains data from sensors installed on the hull and provides real-time information on acceleration response and local strain response. It is mainly used for real-time monitoring of important structures, sensitive areas and key components of the hull, as well as online evaluation of the hull's structural strength.

[0003] However, the stress monitoring equipment of the ship can only provide very limited stress monitoring data. If you want to achieve accurate stress measurement of the whole ship, you need to arrange a large number of precise stress sensors. The high cost of stress sensors and the limitation of ship structure space make this demand unsatisfactory. It is impossible to monitor all dangerous structural areas of the ship in real time by relying solely on monitoring equipment, which brings difficulties to ship health monitoring. In order to realize the calculation of the stress of the whole ship, under the background of the development of ship intelligence, many calculation software such as WAMIT, Hydrostar, COMPASS-WALCS, etc. have been developed based on many theoretical methods such as linear wave theory and three-dimensional potential flow theory. These software play a vital role in the design, manufacture and safety verification of ships and marine structures. However, these calculations require the known sea conditions of the ship's navigation, and cannot be directly embedded in the monitoring system, which makes it difficult to meet the requirements for calculation timeliness in intelligent navigation.

[0004] Therefore, technicians in this field are committed to developing a full-ship stress distribution inversion method based on finite strain monitoring data. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that due to the limitations of the spatial position of the ship structure and the cost of the monitoring equipment, it is impossible to install monitoring equipment at each dangerous position 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 object, the present invention provides a method for inverting the stress distribution of a whole ship based on finite strain monitoring data, the method comprising the following steps:

[0007] S101: Establishing a finite element model of the entire ship and initializing the configuration of the finite element model;

[0008] S103: Calculate the free vibration mode of the ship and select the basic mode according to the vibration mode;

[0009] S105: Arrange monitoring equipment for monitoring hull stress at the hull structure that can reflect the total 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 the step S101, a structural finite element analysis method is used to establish a 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 bones and beams are simulated using two-node beam elements.

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

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

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

[0015] Furthermore, in step S105, a plurality of monitoring points are deployed on the ship, and the monitoring equipment is deployed at the monitoring points, and the monitoring points are distributed at the bow, midship and stern of the ship. The monitoring points include the vicinity of the waterline, the deck and the side, and the parameter L is the length of the ship.

[0016] Furthermore, in the step S105, the monitoring device uses a long baseline sensor, and the sensor measures and collects the longitudinal stress response of the monitoring point.

[0017] Furthermore, a monitoring point with the most intense total longitudinal response is selected as a verification point, a relative error between the measured stress and the inverted stress of the verification point is calculated, and the relative error is used as a criterion for judging the reliability of the inversion result.

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

[0019]

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

[0021] Furthermore, in step S107, the weight coefficients of the basic modes of the monitoring points are obtained by solving a linear equation group, and the linear equation group is:

[0022] q=(σ monitor ) -1 σ real

[0023] Among them, q is the weight coefficient matrix of the basic mode, σ monitor is the stress monitoring value matrix of the monitoring points in the modal vibration shape, σ real is the stress measured value matrix of 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. The present invention can decouple the vibrations of each order of the ship through the modal superposition method, and obtain the stress response of the entire hull by linearly superposing the stress distribution of each mode with its weight coefficient. It can realize real-time monitoring of the stress response of the entire ship structure based on a limited number of local monitoring devices;

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

[0027] 3. The present invention pre-stores all basic data required for stress inversion into the calculation program in the form of a database. During the calculation process, the solution of the equation and the calculation of stress only need to call the data inside the calculation program, and there is no need to read 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, so that the stress inversion program can be smoothly embedded in the ship monitoring system, and meet the requirements of calculation timeliness during the navigation of intelligent ships with relatively small computer resources, which can provide support for real-time monitoring of ship structures and assist in early warning of ship structure risks.

[0028] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of a method for inverting the stress distribution of a whole ship according to an embodiment of the present invention;

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

[0031] Figure 3 is a schematic diagram of a basic mode vibration shape of an embodiment of the present invention;

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

[0033] Figure 5 Schematic diagram of a time history curve of stress inversion results according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0035] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0036] like Figure 1As shown, an embodiment of the present invention proposes a method for inverting the stress distribution of the whole ship based on finite strain monitoring data, which is to establish a stress deduction model of the whole ship structure of a large-opening container ship based on the modal superposition method and the finite element model, and calculate and deduce the stress level of the remaining main key area structure where no sensors are installed by using the measured data of a limited number of stress monitoring devices installed on the ship. The method includes the following steps:

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

[0038] In this embodiment, a structural finite element analysis method is used to establish a 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 bones and beams are simulated using two-node beam elements.

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

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

[0041] The free vibration modes of the ship are calculated using the finite element calculation software femap. The calculation and solution method uses Lanczos. In the free vibration range of 0-50 Hz, according to the vibration type, the selected basic modes include multi-order vertical bending modes, multi-order torsional modes and first-order lateral bending modes. Among them, the multi-order vertical bending modes include first-order vertical bending modes, second-order vertical bending modes and third-order vertical bending modes; the multi-order torsional modes include first-order torsional modes, second-order torsional modes and third-order torsional modes.

[0042] S3: Monitoring equipment for monitoring hull stress is arranged at the hull structure that can reflect the total longitudinal deformation characteristics of the hull.

[0043] The purpose of the present invention is to invert the total longitudinal stress of the 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 the monitoring points. The monitoring points are distributed at the bow, midship and stern of the ship. The monitoring points are located near the waterline, on the deck and on the side (parameter L is the length of the ship).

[0044] The monitoring equipment uses a long baseline sensor, which measures and collects the longitudinal stress response of the monitoring point, and selects the monitoring point with the most intense total longitudinal response as the verification point. The relative error between the measured stress and the inverted stress of the verification point is calculated, and the relative error is used as the criterion for judging the reliability of the inversion result.

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

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

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

[0048]

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

[0050] The weight coefficient q of each basic mode of the monitoring point can be obtained by solving the linear equation system, which is:

[0051] q=(σ monitor ) -1 σ real

[0052] Among them, q is the weight coefficient matrix of the basic mode, σ monitor is the stress monitoring value matrix of the monitoring points in the modal vibration shape, σ real is the stress measured value matrix of the monitoring points.

[0053] According to the modal weight coefficient, the stress response of the prediction point can be obtained by linearly superposing each mode:

[0054] σ=σ prediction q.

[0055] Compared with the prior art, the whole ship stress distribution inversion method based on finite strain monitoring data provided by the embodiment of the present invention has the following beneficial effects:

[0056] 1. In the prior art, due to the limitation of the spatial position of the ship structure and the cost of monitoring equipment, the number of sensors is limited, and it is impossible to install monitoring equipment at every dangerous position of the ship. It is impossible 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. The present invention can calculate the weight coefficients of each order of basic modes in the actual response of the ship according to the stress monitoring data of a limited number of measuring points, and linearly superimpose the basic modal stress of the corresponding area in the database according to the same weight coefficient at the position where the measuring point is not installed, so as to invert the stress response of the current position.

[0057] 2. The present invention is based on the principle of structural mechanics. When a ship sails in the waves, the vibration generated by the load of the waves is composed of various modes of various vibration types. The modal superposition method can decouple the various vibrations of the ship. The stress response of the entire hull is obtained by linearly superimposing the stress distribution of each mode with its weight coefficient. Based on a limited number of local monitoring equipment, real-time monitoring of the stress response of the entire ship structure can be achieved. The hull structure stress inversion technology provided by the present invention can provide guidance for the structural safety inspection and fatigue analysis of the ship. It has important application value and practical significance in the field of ship structure monitoring and analysis, and provides strong technical support for ensuring the safe operation and long-term stability of the ship.

[0058] 3. In view of the problem that the existing calculation software cannot be directly embedded in the monitoring system and the calculation takes a long time, and cannot meet the calculation timeliness requirements during the navigation of intelligent ships, the method provided by the embodiment of the present invention only needs to access the stress monitoring values ​​of each measuring point of the monitoring system during the inversion process, and no interaction with the finite element software is required. All basic data required for stress inversion are pre-stored in the calculation program in the form of a database. During the calculation process, the solution of the equation and the calculation of the stress only need to call the data inside the calculation program, and no data needs to be read 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, so that the stress inversion program can be smoothly embedded in the ship monitoring system, and the calculation timeliness requirements during the navigation of intelligent ships can be met with relatively small computer resources. Support can be provided for real-time monitoring of ship structures and assist in early warning of ship structure risks.

[0059] The present invention is described in detail below in conjunction with the preferred embodiments of the present invention.

[0060] The purpose of the present invention is to establish a stress deduction model for the entire ship structure of a large-opening container ship based on the modal superposition method and the finite element model, and to calculate and deduce the stress levels of the remaining main key area structures where no sensors are installed, with the help of the measured data of a limited number of stress monitoring devices installed on the ship.

[0061] In this embodiment, the object of the stress inversion test is a 14000TEU container ship, which is 330 meters long, 51 meters wide, and 30 meters deep. The test sea condition is a 14.4m draft and wave condition, and the ship speed is 19.7kn.

[0062] like Figure 1 As shown, the method for inverting the stress distribution of the whole ship based on finite strain monitoring data provided by the preferred embodiment of the present invention comprises the following steps:

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

[0064] like Figure 2As shown, in this embodiment, according to the structural drawings of the 14000TEU container ship, a 14000TEU container ship finite element model is established by using structural finite element analysis software such as femap. The finite element model is a 1:1 real-size model, in which the plate and keel structure are simulated by quadrilateral and triangular plate and shell elements, and the longitudinal bones and beams are simulated by two-node beam elements. The corresponding structural materials are assigned based on the material properties of the actual ship structure, and the ship weight distribution is adjusted and the boundary conditions are set.

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

[0066] In this embodiment, the finite element calculation software femap is used to calculate the free vibration mode of the ship. The calculation solution method adopts Lanczos. In the free vibration range of 0-50 Hz, according to the vibration mode, the first to third order vertical bending, the first to third order torsion and the first order transverse bending are selected as the basic modes. The schematic diagram of the basic mode vibration mode of a 14000TEU container ship is shown in Figure 3 shown.

[0067] Step 3: Deploy monitoring equipment on board.

[0068] The purpose of the present invention is to invert the total longitudinal stress of the ship. Therefore, several monitoring points that can reflect the total longitudinal deformation characteristics of the ship are selected at the hull structure. The point selection process refers to Chapter 21 of Part 8 of the "Rules for Classification of Seagoing Steel Ships", "Container ships with a length of more than 180m should focus on monitoring the following parts: the total longitudinal stress at L / 4 from the midship, including the port and starboard sides; the longitudinal stress at the bottom (L / 2) close to the middle of the ship, including the port and starboard sides; etc." Based on this principle, this embodiment arranges a total of 8 long baseline sensors at the actual ship structure, which are distributed at the bow 1 / 4L, midship and stern 1 / 4L of the ship, including near the waterline, deck and side, so as 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, the data transmission frequency is 10 Hz, and the stress refers to the unidirectional stress in the direction of the ship length.

[0070] like Figure 4 As shown, the schematic diagram of the monitoring equipment layout of a 14000TEU container ship in this embodiment, measuring points are arranged at 1 / 4L of the bow, amidships and 1 / 4L of the stern of the ship, including 8 monitoring points near the waterline, on the deck and on the side, which are marked as: G1, G2, G3, G4, G5, G6, G7, G8.

[0071] At the same time, in order to verify the reliability of the stress inversion result of the present invention, G2 is selected as the verification point, and the relative error between the measured stress and the inverted stress at G2 is used as the criterion for judging the reliability of the inversion result.

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

[0073] The rib position distribution of each sensor 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 sensor ribs

[0075] Sensor Name Sensor marking Costal position 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 calculation.

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

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

[0079]

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

[0081] This equation is usually a coupled equation, which can be decoupled by changing the canonical coordinates, thereby reducing the workload of solving the equation.

[0082] It is assumed that the displacement deformation of the structure can be composed of a finite number of vibration modes linearly superposed, namely:

[0083] x=Φq=φ1q1+φ2q2+... (2)

[0084] represents the principal mode shape of the structure and q is the component of the generalized canonical coordinates.

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

[0086]

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

[0088]

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

[0090]

[0091] According to the measured stress values ​​of the monitoring points on the actual ship and the stress values ​​of the monitoring points in the extracted modal vibration shapes, the weight coefficient q of each mode is obtained.

[0092] q=(σ monitor ) -1 σ real (6) According to the modal weight coefficient q, the stress response of the prediction point can be obtained by linearly superposing each mode.

[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 hull structure stress monitoring can be established.

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

[0096] Through the stress inversion technology based on the modal superposition method, the stress response of point G2 under the current sea conditions is inverted. To invert the stress at G2, the parameter that needs to be solved is the modal weight coefficient q, which can be calculated using formula (6).

[0097] The basic modal stress matrix A of each stress monitoring point (including G2) (corresponding 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) of each stress monitoring point

[0099]

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

[0101] Table 3 Stress response matrix B of each measuring point

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

[0103] By solving the linear equations according to formula (6), the weight coefficients X of each basic mode (corresponding to q in formula (6)) can be obtained 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 different basic modes according to the proportion.

[0104] Table 4 Weight coefficients X of each basic mode

[0105] Basic Mode Weight coefficient First-order vertical bending -2.35 Second order vertical bending -0.21 Three-step vertical bend -1.45 First-order torsion -1.05 Second-order torsion -0.39 Third-order torsion -0.28 First-order transverse bending -0.20

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

[0107] Table 5G2 basic modal stress matrix A' (MPa)

[0108]

[0109] According to formula (7), the basic modal stress of the table measuring point G2 is linearly superimposed by the weight coefficient in Table 2, and the stress value B' of G2 at the current moment can be inverted from A'X=B' (corresponding to σ in formula (7), i.e., the stress inversion result), and B'=56.50MPa. According to the monitoring equipment data, the actual stress response at G2 at the current moment is 54.01MPa, so the relative error of the stress inversion technology at the current moment is 4.61%.

[0110] According to the above calculation process, the stress response at G2 within 5 minutes is inverted and the obtained stress inversion result time history curve is as follows: Figure 5 As shown, the relative error of stress inversion at each moment is 4.78% on average within 5 minutes.

[0111] Practical tests have shown that the stress inversion technology based on the modal superposition method has a good inversion effect, can calculate the stress response of the area of ​​the ship where no detection equipment is arranged, 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 by the embodiment of the present invention has the following advantages:

[0113] 1. Real-time stress monitoring of various structural parts of the ship can be achieved without relying on a large number of monitoring equipment, with low computing resource requirements and high computing efficiency.

[0114] 2. Under different sea conditions, real-time monitoring of the stress response of the entire ship structure can be completed based on very few monitoring equipment, providing certain guidance for ship health monitoring and safety assessment.

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

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

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

[0118] 3. Production implementation: The hull structure stress inversion method provided by the embodiment of the present invention does not require access to additional finite element software during the stress inversion calculation process. It can independently complete stress inversion based on the built-in database of the calculation program and combined with the stress equipment monitoring data. It can be smoothly embedded in the ship monitoring system without adding additional equipment. At the same time, the calculation process requires small computing resources, the inversion timeliness is strong, and the inversion calculation delay for real-time stress data does not exceed 1s.

[0119] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for inversion of stress distribution of a whole ship based on finite strain monitoring data, characterized in that: The method comprises the following steps: S101: Establishing a finite element model of the entire ship and initializing the configuration of the finite element model; S103: Calculate the free vibration mode of the ship and select the basic mode according to the vibration mode; S105: Arrange monitoring equipment for monitoring hull stress at the hull structure that can reflect the total 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.

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

3. The method according to claim 2, characterized in that In the step S101, when the finite element model is initially configured, the corresponding structural material properties in the finite element model are assigned based on the material properties of the actual ship structure, and the ship weight distribution is adjusted and boundary conditions are set.

4. The method according to claim 3, characterized in that In the step S103, the basic modes include multiple-order vertical bending modes, multiple-order torsional modes and a first-order lateral bending mode.

5. The method according to claim 4, characterized in that The multi-order vertical bending modes include a first-order vertical bending mode, a second-order vertical bending mode and a third-order vertical bending mode; the multi-order torsional modes include a first-order torsional mode, a second-order torsional mode and a third-order torsional mode.

6. The method according to claim 5, characterized in that In step S105, a plurality of monitoring points are deployed on the ship, and the monitoring equipment is deployed at the monitoring points. The monitoring points are distributed at the bow, midship and stern of the ship. L, the monitoring point locations include near the waterline, deck and side, and the parameter L is the length of the ship.

7. The method according to claim 6, characterized in that In the step S105, the monitoring device uses a long baseline sensor, and the sensor measures and collects the longitudinal stress response of the monitoring point.

8. The method according to claim 7, characterized in that The monitoring point with the most intense total longitudinal response is selected as the verification point, the relative error between the measured stress and the inversion stress of the verification point is calculated, and the relative error is used as the criterion for judging the reliability of the inversion result.

9. The method according to claim 8, characterized in that In step S107, when the modal superposition method is used to perform stress inversion calculation, the following calculation formula is used: Where σ is the actual stress response, σ i is the stress response of the i-th order fundamental mode, q i is the weight coefficient of the i-th order basic mode, and n is the number of basic modes.

10. The method according to claim 9, characterized in that In step S107, the weight coefficients of the basic modes of the monitoring points are obtained by solving a linear equation group, and the linear equation group is: q=(σ monitor ) -1 s real Among them, q is the weight coefficient matrix of the basic mode, σ monitor is the stress monitoring value matrix of the monitoring points in the modal vibration shape, σ real is the stress measured value matrix of the monitoring points.

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