Ship structure stress field detection system and method based on ultrasonic guided waves

Abstract

The invention discloses a ship structure stress field detection system and method based on ultrasonic guided waves. The system comprises a guided wave excitation receiving module, a signal processing module, a stress evaluation module and an imaging output module. The guided wave excitation receiving module excites a ship structure, receives guided wave signals on the ship structure and transmits the guided wave signals to the signal processing module. The signal processing module performs signal preprocessing on the received guided wave signal, extracts time domain characteristics and frequency domain characteristics of the signal, extracts information related to stress and transmits the information to the stress evaluation module; the stress evaluation module calculates guided wave signal group velocities on different paths based on guided wave signal flight time, and calculates stress field distribution of a ship structure under different working conditions based on a finite element method of material mechanical characteristics; and the imaging output module forms a stress field distribution image of the ship structure in the detection area based on the stress field distribution. According to the invention, ship structure stress field detection under different working conditions can be realized, and the method has the advantages of non-destructiveness and high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of stress field nondestructive testing, and in particular to a ship structure stress field testing system and method based on ultrasonic guided waves. Background Art

[0002] With the rapid development of the shipbuilding industry, the safety and reliability of ships are increasingly valued. During the use of ships, the outer plate structure is subjected to complex stress states, including static loads, dynamic loads and environmental factors. These stresses may cause material fatigue, crack propagation and structural failure, thus affecting the overall safety of the ship. Therefore, it is particularly important to detect and evaluate the stress state of the ship structure in a timely and accurate manner.

[0003] Traditional stress field detection methods mainly include physical measurement methods and destructive detection methods. Physical measurement methods usually rely on equipment such as strain gauges and pressure sensors. Although these methods can provide certain stress data, they have disadvantages such as complex installation, high cost, and poor real-time performance in practical applications. Destructive detection methods require cutting or drilling of ship structures. Although relatively accurate stress data can be obtained, they will cause irreversible damage to the ship and are not suitable for the detection of ships in service. In recent years, ultrasonic detection technology has attracted widespread attention due to its non-destructive, high sensitivity and real-time monitoring capabilities. Ultrasonic guided wave technology uses the propagation characteristics of sound waves in materials to effectively detect defects and stress states inside materials. By analyzing the reflection, scattering and attenuation characteristics of ultrasonic waves when propagating in materials, the stress field distribution information of the material can be obtained. However, the existing ultrasonic guided wave detection system still has some shortcomings in practical applications, such as complex signal processing, inaccurate stress assessment models, and lack of real-time imaging output.

[0004] Therefore, there is an urgent need for a new type of ship structure stress field detection technology based on ultrasonic guided waves, which can overcome the shortcomings of the existing technology and realize efficient, accurate and real-time detection of ship structure stress. This technology should have good operability and adaptability, be able to operate stably under different working environments, and provide intuitive stress field distribution images to facilitate ship maintenance and safety assessment. Summary of the invention

[0005] In order to overcome the defects and shortcomings of the prior art, the present invention provides a ship structure stress field detection system and method based on ultrasonic guided waves. According to the measured guided wave signals, the present invention overcomes the shortcomings of various traditional stress field detection methods such as inaccuracy, destructiveness, complex equipment, and difficulty in operation, and has the advantages of fast response speed, accurate detection and positioning of stress fields in the detection area, and high detection accuracy.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a ship structure stress field detection system based on ultrasonic guided waves, comprising: a guided wave excitation receiving module, a signal processing module, a stress evaluation module, and an imaging output module;

[0008] The waveguide excitation receiving module is used to excite the ship structure and receive the waveguide signal on the ship structure, and transmit the waveguide signal to the signal processing module;

[0009] The signal processing module is used to perform signal preprocessing on the received waveguide signal, extract the time domain characteristics and frequency domain characteristics of the signal, extract stress-related information based on the time domain characteristics and frequency domain characteristics, and transmit the information to the stress assessment module;

[0010] The stress evaluation module is used to calculate the group velocity of the guided wave signal on different paths based on the flight time of the guided wave signal on the ship deck, and calculate the stress field distribution of the ship structure under different working conditions based on the finite element method of material mechanical properties;

[0011] The imaging output module is used to form a stress field distribution image of the ship structure in the detection area based on the stress field distribution, and to display the stress state of the ship structure.

[0012] As a preferred technical solution, it also includes a pre-detection calibration module, which is used to perform self-detection and calibration on the entire detection system, detect the working status of each module and the influence of environmental factors, and monitor the status of the detection system itself.

[0013] As a preferred technical solution, the waveguide excitation receiving module transmits an ultrasonic signal of a set frequency to the ship structure through a high-frequency piezoelectric sensor to excite the material to generate guided waves.

[0014] As a preferred technical solution, the waveguide excitation receiving module is provided with a probe and a piezoelectric sheet. The piezoelectric sheet of each probe transmits a specified excitation signal in turn, and the remaining probes receive the signal and transmit the received signal to the signal processing module.

[0015] As a preferred technical solution, the signal processing module is used to perform signal preprocessing on the received waveguide signal, and the signal preprocessing includes signal alignment processing, signal filtering processing and signal denoising processing.

[0016] As a preferred technical solution, the stress assessment module is used to calculate the group velocity of the waveguide signal on different paths based on the flight time of the waveguide signal on the ship deck, derive the theoretical group velocity of the mode existing in the ship deck, and the theoretical group velocity of the main mode when the stress condition changes, and quantitatively deduce the stress magnitude of the measuring point based on the group velocity, and jointly evaluate the intersection of each path according to the stress condition on different paths, and calculate the stress magnitude of all measuring points.

[0017] As a preferred technical solution, the method of deriving the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the main mode when the stress state changes specifically includes:

[0018] The stress assessment module calculates the group velocity of the waveguide signal on a single path through the flight time of the waveguide signal. At the same time, it calculates the group velocity under the additional stress state in advance based on the known material parameters, establishes the corresponding relationship between the group velocity and the stress value, and finds the stress value under the current path through the calculated group velocity.

[0019] The corresponding relationship between the group velocity and the stress value is established, including:

[0020] The material is divided into grid elements, and the governing equation of wave motion for each element is expressed as:

[0021] ∫ Γ δu (e)T t (e) dΓ=∫ V δu (e)T (ρ (e) ü (e) )dV+∫ V δε (e)T σ (e) dV

[0022] Among them, δu(e) and δε(e) represent the virtual displacement and virtual strain of the unit, respectively, t (e) and σ (e) represents the external force and internal stress vector, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second-order derivative with respect to time, Γ is the unit surface, and V is the unit volume;

[0023] After assembling all unit matrices and applying stress conditions, the characteristic equation of the entire system is expressed as:

[0024] (K1+ikK2+k 2 K3-ω 2 M)Q=0

[0025]

[0026]

[0027]

[0028]

[0029] Among them, the global stiffness matrix K1, K2, K3 and the global mass matrix M are obtained by solving the stiffness matrix of a single unit of the control equation and the mass matrix M (e) It is obtained that N represents the number of all mesh nodes, Q is the node displacement 3N×1 vector, C is the stiffness matrix, B is the element shape function, and dξ represents the grid line element differential;

[0030] The group velocity corresponding to the stress is expressed as:

[0031]

[0032] Among them, Q L and Q R are the left eigenvector and the right eigenvector respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. The corresponding relationship between the group velocity and the stress value of the object is obtained, and then the corresponding stress value on the path is found by calculating the group velocity on a single path according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece.

[0033] The present invention also provides a ship structure stress field detection method based on ultrasonic guided waves, provided with the ship structure stress field detection system based on ultrasonic guided waves, the method comprising the following steps:

[0034] The guided wave excitation receiving module transmits ultrasonic guided wave signals through the ultrasonic transmitter to excite the ship structure, and receives the reflected ultrasonic guided wave signals through the ultrasonic receiver;

[0035] The signal processing module performs signal preprocessing on the received waveguide signal, extracts the time domain characteristics and frequency domain characteristics of the signal, extracts stress-related information based on the time domain characteristics and frequency domain characteristics, and transmits the information to the stress assessment module;

[0036] The stress assessment module calculates the group velocity of the guided wave signal on different paths based on the flight time of the guided wave signal on the ship deck, and calculates the stress field distribution of the ship structure under different working conditions using the finite element method based on the mechanical properties of the material;

[0037] The imaging output module forms a stress field distribution image of the ship structure in the detection area based on the stress field distribution, and displays the stress state of the ship structure.

[0038] As a preferred technical solution, the stress assessment module calculates the group velocity of the waveguide signal on different paths based on the flight time of the waveguide signal on the ship deck, derives the theoretical group velocity of the mode existing in the ship deck, and the theoretical group velocity of the main mode when the stress condition changes, and quantitatively deduces the stress magnitude of the measuring point based on the group velocity, and jointly evaluates the intersection points of each path according to the stress conditions on different paths, and calculates the stress magnitude of all measuring points.

[0039] As a preferred technical solution, the method of deriving the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the main mode when the stress state changes specifically includes:

[0040] The stress assessment module calculates the group velocity of the waveguide signal on a single path through the flight time of the waveguide signal. At the same time, it calculates the group velocity under the additional stress state in advance based on the known material parameters, establishes the corresponding relationship between the group velocity and the stress value, and finds the stress value under the current path through the calculated group velocity.

[0041] The corresponding relationship between the group velocity and the stress value is established, including:

[0042] The material is divided into grid cells, and the governing equation of wave motion for each cell is expressed as:

[0043] ∫ Γ δu (e)T t (e) dΓ=∫ V δu (e)T (ρ (e) ü (e) )dV+∫ V δε (e)T σ (e) dV

[0044] Among them, δu(e) and δε(e) represent the virtual displacement and virtual strain of the unit, respectively, t (e) and σ (e) represents the external force and internal stress vector, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second-order derivative with respect to time, Γ is the unit surface, and V is the unit volume;

[0045] After assembling all unit matrices and applying stress conditions, the characteristic equation of the entire system is expressed as:

[0046] (K1+ikK2+k 2 K3-ω 2 M)Q=0

[0047]

[0048]

[0049]

[0050]

[0051] Among them, the global stiffness matrix K1, K2, K3 and the global mass matrix M are obtained by solving the stiffness matrix of a single unit of the control equation and the mass matrix M (e) It is obtained that N represents the number of all mesh nodes, Q is the node displacement 3N×1 vector, C is the stiffness matrix, B is the element shape function, and dξ represents the grid line element differential;

[0052] The group velocity corresponding to the stress is expressed as:

[0053]

[0054] Among them, Q L and Q R are the left eigenvector and the right eigenvector respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. The corresponding relationship between the group velocity and the stress value of the object is obtained, and then the corresponding stress value on the path is found by calculating the group velocity on a single path according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece.

[0055] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0056] (1) The present invention utilizes ultrasonic guided wave technology to achieve efficient, accurate and non-destructive ship structure stress field detection, and can monitor the stress state of the ship structure in real time to ensure the safety and reliability of the ship.

[0057] (2) The present invention makes full use of the propagation characteristics of ultrasonic guided waves in materials. By emitting ultrasonic signals of a specific frequency, the ship structure is stimulated and its reflected signals are monitored. Ultrasonic guided waves can penetrate materials and effectively detect their internal defects and stress states, and have the advantages of being non-destructive and highly sensitive.

[0058] (3) The present invention designs the detection system into multiple functional modules, including a pre-detection calibration module, a guided wave excitation receiving module, a signal processing module, a stress assessment module and an imaging output module. The integration of each module enables the system to operate flexibly in different working environments, thereby ensuring the efficiency and accuracy of the detection process.

[0059] (4) The signal processing module of the present invention preprocesses and analyzes the received reflected signal, and extracts information related to the stress state, such as amplitude, phase and frequency changes, by deeply analyzing the time domain and frequency domain characteristics of the signal, thereby effectively improving the accuracy of stress assessment.

[0060] (5) The stress assessment module of the present invention is based on known material parameters and propagation models, and uses calculation methods such as finite element analysis to quantitatively calculate the stress field distribution of the ship structure. By establishing an accurate stress assessment model, it is possible to achieve a comprehensive assessment of the stress state of the outer plate under different working conditions.

[0061] (6) The imaging output module of the present invention visualizes the calculated stress field distribution data to generate an intuitive stress field distribution image. This function not only facilitates technicians to quickly understand and analyze the test results, but also provides an important basis for subsequent maintenance and decision-making. It can also provide real-time feedback during the test process to ensure that the stress state of the ship during operation is monitored and evaluated in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic diagram of the overall architecture of the ship structure stress field detection system based on ultrasonic guided waves of the present invention;

[0063] Figure 2 A schematic diagram of the arrangement of piezoelectric sheets of the present invention;

[0064] Figure 3 A schematic diagram of a process for evaluating stress magnitude by the stress evaluation module of the present invention;

[0065] Figure 4 It is a schematic diagram of the overall process of the ship structure stress field detection method based on ultrasonic guided waves of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0067] Example 1

[0068] like Figure 1 As shown, this embodiment provides a ship structure stress field detection system based on ultrasonic guided waves, including: a pre-detection calibration module, a guided wave excitation receiving module, a signal processing module, a stress evaluation module, and an imaging output module;

[0069] The pre-detection and calibration module is used to perform self-detection and calibration on the entire detection system, detect the impact of other uncontrollable factors such as installation conditions and temperature on the detection, and detect the faults of the system itself, such as loose piezoelectric pieces, to ensure that the system operates in the best condition.

[0070] Specifically, the pre-detection and calibration module includes but is not limited to a self-check function, an environmental impact detection function, and a fault diagnosis function. The self-check function is to start the self-check program through the interface, and the system will automatically check the working status of each module; the environmental impact detection function is to detect the potential impact of uncontrollable factors such as installation conditions and temperature changes on the test results to ensure that environmental factors do not interfere with the test accuracy; the fault diagnosis function is to monitor the status of the system itself in real time, identify possible faults, such as loose piezoelectric pieces, poor sensor connections, etc., and provide fault information and maintenance suggestions;

[0071] The guided wave excitation receiving module is used to excite the measured object (ship structure) and receive the guided wave signal on the measured object (ship structure), and transmit the signal to the signal processing module;

[0072] Among them, signal excitation is to transmit ultrasonic signals of set frequency to the ship structure through high-frequency piezoelectric sensors to stimulate the material to generate guided waves. Signal reception is to receive the guided wave signals reflected from the measured object and pass them to the signal processing module for subsequent analysis. During the entire signal transmission process, it ensures that the received signal maintains high quality and reduces signal attenuation and distortion.

[0073] like Figure 2 As shown, the waveguide excitation receiving module is provided with a probe and a piezoelectric sheet, wherein the piezoelectric sheets are of the same specification and are placed in a specified manner, including but not limited to in the manner of equidistant points on a circle, the piezoelectric sheet of each probe sequentially transmits a specified excitation signal, and the remaining probes receive the signal and transmit the received signal to the signal processing module;

[0074] In this embodiment, the ultrasonic transmitter of the waveguide excitation receiving module can be a single-frequency or multi-frequency transmitter, and the ultrasonic receiver has a wide-band receiving capability to meet different detection requirements; and its placement includes but is not limited to taking the equidistant nodes on the circumference as the center point;

[0075] The signal processing module is used to process the signal received by the guided wave excitation receiving module, to perform pre-processing such as alignment and filtering on the received reflected signal, to analyze the time domain and frequency domain characteristics of the signal, and to extract information related to stress;

[0076] In this embodiment, the signal processing module performs preprocessing such as alignment, filtering, and denoising on the received reflected signal to improve the signal quality, uses time domain and frequency domain analysis techniques to analyze the amplitude, phase, frequency and other characteristics of the signal, identifies changes related to the stress state, such as amplitude, phase and frequency changes, extracts information related to stress, and transmits the processed data to the stress assessment module for further analysis;

[0077] In this embodiment, the signal processing module uses a variety of signal processing technologies, including but not limited to: Fast Fourier Transform (FFT), Wavelet Transform and adaptive filtering, etc., to improve the analysis accuracy of signal characteristics.

[0078] The stress assessment module is used to calculate the stress state of each measurement point on the ship structure based on the information processed by the signal processing module, and calculate the stress field distribution using known material parameters and propagation models;

[0079] In this embodiment, the stress assessment module uses the finite element method based on known material mechanical properties (including elastic modulus, yield strength, etc.) to calculate the stress field distribution of the ship structure under different working conditions, and on this basis provides an assessment of the degree of stress concentration, provides quantitative stress assessment results based on the stress field distribution data of the ship structure, and verifies the accuracy and reliability of the stress assessment by comparing it with the actual measurement data;

[0080] In this embodiment, the stress assessment module first performs a preliminary assessment on the stress state of each path, assesses the average stress magnitude on the path, and after completing the stress assessment of all single paths, performs a joint assessment on the intersections of the paths according to the stress states on different paths, further narrowing the range of the stress concentration area;

[0081] The group velocity is calculated based on the flight time of the ultrasonic guided wave in the ship deck, and combined with the material and geometry of the ship structure, the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the main mode when the stress condition changes are derived. The stress magnitude of the measuring point is quantitatively deduced from the calculated group velocity;

[0082] After calculating the stress magnitude of all measurement points, the imaging output module images the detection area according to the position of each measurement point to display the stress field distribution of the detection area;

[0083] like Figure 3 As shown, the stress evaluation module evaluates the stress magnitude. The stress evaluation module can calculate the group velocity of the waveguide signal on a single path through the flight time of the waveguide signal, and at the same time calculate the group velocity under the additional stress state in advance based on known material parameters such as Young's modulus, density, Pearson coefficient, etc., and establish a corresponding relationship between the group velocity magnitude and the stress value magnitude, so as to find the stress value magnitude under the current path through the calculated group velocity. The process of establishing the relationship between the group velocity and the stress value is obtained according to the following method:

[0084] The material is divided into grid units, and the governing equation of wave motion for each unit can be obtained by the following virtual work principle:

[0085] ∫ Γ δu (e)T t (e) dΓ=∫ V δu (e)T (ρ (e) ü (e) )dV+∫ V δε (e)T σ (e) dV

[0086] where δu(e) and δε(e) represent the virtual displacement and virtual strain of the element, respectively. (e) and σ (e)represents the external force and internal stress vector, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second-order derivative with respect to time, Γ is the unit surface, and V is the unit volume.

[0087] After assembling all unit matrices and applying stress conditions, the characteristic equation of the entire system can be expressed as follows:

[0088] (K1+ikK2+k 2 K3-ω 2 M)Q=0

[0089] The global stiffness matrices K1, K2, K3 and the global mass matrix M are obtained by solving the stiffness matrix of a single unit in the control equation And the mass matrix M(e) is obtained, and the expression of the unit matrix is ​​as follows:

[0090]

[0091]

[0092]

[0093]

[0094] The size of matrices K1, K2, K3 and M is 3N×3N, where N is the number of all mesh nodes. Q is a 3N×1 vector of node displacements, C is a stiffness matrix, B is a simplified element shape function for ease of calculation, and dξ is the grid line element differential.

[0095] The group velocity corresponding to the stress can be expressed as:

[0096]

[0097] Where Q L and Q R are the left eigenvector and the right eigenvector respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. The corresponding relationship between the group velocity and the stress value of the object is thus obtained, and then the corresponding stress value on the path is found according to the flight time obtained from the analysis signal, the distance from the piezoelectric piece, and the group velocity on a single path.

[0098] The group velocity of the guided wave signal in the measured object under different additional stress conditions is calculated by the above method, and the stress on each path is measured;

[0099] The stress data on all paths are integrated, and the stress values ​​of the sampling points are calculated based on the average stress values ​​of different paths.

[0100] The imaging output module is used to form a stress field distribution image in the detection area using the calculated stress field distribution data, displaying the stress state of the ship structure and facilitating rapid analysis of the detection results.

[0101] In this embodiment, the imaging output module has at least one visualization tool to display the stress field distribution results in the form of a heat map, a vector map or a three-dimensional graph, thereby enhancing the understanding and analysis of the detection results.

[0102] This embodiment uses ultrasonic guided wave technology to achieve high-precision detection and non-destructive detection of the stress state of the ship structure. By jointly evaluating the stress states of different paths, it is possible to have a more comprehensive understanding of the stress concentration area, provide more accurate stress field distribution information, reduce possible errors in traditional methods, and obtain stress data in real time, so as to facilitate the timely discovery of potential structural problems and improve the safety of the ship. It can also be adjusted according to ship structures of different materials and geometric shapes, has strong adaptability, and is suitable for various types of ships.

[0103] Example 2

[0104] like Figure 4 As shown, this embodiment also provides a ship structure stress field detection method based on ultrasonic guided waves, provided with the ship structure stress field detection system based on ultrasonic guided waves of the above embodiment 1, the method comprises the following steps:

[0105] S1: Use the pre-detection calibration module to fully calibrate the detection system and monitor the status of each sensor to ensure that the detection environment is in the best condition;

[0106] S2: In the guided wave excitation receiving module, an ultrasonic guided wave signal is emitted by an ultrasonic transmitter to excite the ship structure, and an ultrasonic receiver is used to receive the echo signal reflected from the outer plate;

[0107] In this embodiment, ultrasonic guided waves of various frequencies can be selected to perform multi-angle and multi-level stress field detection;

[0108] S3: In the signal processing module, the received waveguide signal is preprocessed, including signal alignment and noise elimination, and then frequency domain analysis is performed to extract the amplitude, phase and change characteristics of the waveguide signal;

[0109] S4: In the stress assessment module, based on the extracted information and known material properties, the propagation model and finite element analysis method are used to quantitatively calculate the stress state of different measurement points of the ship structure, including:

[0110] First, a preliminary assessment is made on the stress state of each path, and the average stress magnitude on the path is evaluated. After the stress assessment of all single paths is completed, a joint assessment is performed on the intersections of the paths according to the stress conditions on different paths, so as to further narrow the scope of the stress concentration area.

[0111] The group velocity is calculated based on the flight time of the ultrasonic guided wave in the ship deck, and combined with the material and geometry of the ship structure, the theoretical group velocity of the mode in the plate and the theoretical group velocity of the main mode when the stress condition changes are derived. The stress magnitude of the measuring point is quantitatively deduced from the calculated group velocity;

[0112] S5: In the imaging output module, the calculated stress field distribution results are visualized to generate a stress field distribution image of the ship structure for further evaluation and analysis.

[0113] The present invention utilizes ultrasonic guided wave technology to realize efficient, accurate and non-destructive detection of ship structure stress field, and can monitor the stress state of the ship structure in real time to ensure the safety and reliability of the ship. It overcomes the shortcomings of traditional feedback control and has the advantages of fast response speed, good adaptability to severe sea conditions and high positioning accuracy.

[0114] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A ship structure stress field detection system based on ultrasonic guided waves, characterized in that: include: Guided wave excitation receiving module, signal processing module, stress assessment module, imaging output module; The waveguide excitation receiving module is used to excite the ship structure and receive the waveguide signal on the ship structure, and transmit the waveguide signal to the signal processing module; The signal processing module is used to perform signal preprocessing on the received waveguide signal, extract the time domain characteristics and frequency domain characteristics of the signal, extract stress-related information based on the time domain characteristics and frequency domain characteristics, and transmit the information to the stress assessment module; The stress evaluation module is used to calculate the group velocity of the guided wave signal on different paths based on the flight time of the guided wave signal on the ship deck, and calculate the stress field distribution of the ship structure under different working conditions based on the finite element method of material mechanical properties; The imaging output module is used to form a stress field distribution image of the ship structure in the detection area based on the stress field distribution, and to display the stress state of the ship structure.

2. The ship structure stress field detection system based on ultrasonic guided waves according to claim 1 is characterized in that: It also includes a pre-detection calibration module, which is used to perform self-detection and calibration on the entire detection system, detect the working status of each module and the influence of environmental factors, and monitor the status of the detection system itself.

3. The ship structure stress field detection system based on ultrasonic guided waves according to claim 1 is characterized in that: The waveguide excitation receiving module transmits an ultrasonic signal of a set frequency to the ship structure through a high-frequency piezoelectric sensor to excite the material to generate a waveguide.

4. The ship structure stress field detection system based on ultrasonic guided waves according to claim 1 is characterized in that: The waveguide excitation receiving module is provided with a probe and a piezoelectric sheet. The piezoelectric sheet of each probe transmits a designated excitation signal in turn, and the remaining probes receive the signal and transmit the received signal to the signal processing module.

5. The ship structure stress field detection system based on ultrasonic guided waves according to claim 1 is characterized in that: The signal processing module is used to perform signal preprocessing on the received waveguide signal. Signal preprocessing includes signal alignment processing, signal filtering processing and signal denoising processing.

6. The ship structure stress field detection system based on ultrasonic guided waves according to claim 1 is characterized in that: The stress evaluation module is used to calculate the group velocity of the waveguide signal on different paths based on the flight time of the waveguide signal on the ship deck, derive the theoretical group velocity of the mode existing in the ship deck, and the theoretical group velocity of the main mode when the stress condition changes, and quantitatively deduce the stress magnitude of the measuring point based on the group velocity, and jointly evaluate the intersection points of each path according to the stress conditions on different paths, and calculate the stress magnitude of all measuring points.

7. The ship structure stress field detection system based on ultrasonic guided waves according to claim 6 is characterized in that: The derivation of the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the main mode when the stress state changes specifically includes: The stress assessment module calculates the group velocity of the waveguide signal on a single path through the flight time of the waveguide signal. At the same time, it calculates the group velocity under the additional stress state in advance based on the known material parameters, establishes the corresponding relationship between the group velocity and the stress value, and finds the stress value under the current path through the calculated group velocity. The corresponding relationship between the group velocity and the stress value is established, including: The material is divided into grid cells, and the governing equation of wave motion for each cell is expressed as: ∫ Γ you (e)T t (e) dΓ=∫ V you (e)T (r (e) ü (e) )dV+∫ V not (e)T s (e) dV Among them, δu(e) and δε(e) represent the virtual displacement and virtual strain of the unit, respectively, t (e) and σ (e) represents the external force and internal stress vector, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second-order derivative with respect to time, Γ is the unit surface, and V is the unit volume; After assembling all unit matrices and applying stress conditions, the characteristic equation of the entire system is expressed as: (K1+ikK2+k 2 K3-ω 2 M)Q=0 Among them, the global stiffness matrix K1, K2, K3 and the global mass matrix M are obtained by solving the stiffness matrix of a single unit of the control equation and the mass matrix M (e) It is obtained that N represents the number of all mesh nodes, Q is the node displacement 3N×1 vector, C is the stiffness matrix, B is the element shape function, and dξ represents the grid line element differential; The group velocity corresponding to the stress is expressed as: Among them, Q L and Q R are the left eigenvector and the right eigenvector respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. The corresponding relationship between the group velocity and the stress value of the object is obtained, and then the corresponding stress value on the path is found by calculating the group velocity on a single path according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece.

8. A method for detecting stress field of ship structure based on ultrasonic guided waves, characterized in that: A ship structure stress field detection system based on ultrasonic guided waves according to any one of claims 1 to 7 is provided, and the method comprises the following steps: The guided wave excitation receiving module transmits ultrasonic guided wave signals through the ultrasonic transmitter to excite the ship structure, and receives the reflected ultrasonic guided wave signals through the ultrasonic receiver; The signal processing module performs signal preprocessing on the received waveguide signal, extracts the time domain characteristics and frequency domain characteristics of the signal, extracts stress-related information based on the time domain characteristics and frequency domain characteristics, and transmits the information to the stress assessment module; The stress assessment module calculates the group velocity of the guided wave signal on different paths based on the flight time of the guided wave signal on the ship deck, and calculates the stress field distribution of the ship structure under different working conditions using the finite element method based on the mechanical properties of the material; The imaging output module forms a stress field distribution image of the ship structure in the detection area based on the stress field distribution, and displays the stress state of the ship structure.

9. The method for detecting stress field of ship structure based on ultrasonic guided waves according to claim 8, characterized in that: The stress assessment module calculates the group velocity of the waveguide signal on different paths based on the flight time of the waveguide signal on the ship deck, derives the theoretical group velocity of the mode existing in the ship deck, and the theoretical group velocity of the main mode when the stress condition changes, and quantitatively deduces the stress magnitude of the measuring point based on the group velocity, and jointly evaluates the intersection points of each path according to the stress conditions on different paths, and calculates the stress magnitude of all measuring points.

10. The method for detecting stress field of ship structure based on ultrasonic guided waves according to claim 9, characterized in that: The derivation of the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the main mode when the stress state changes specifically includes: The stress assessment module calculates the group velocity of the waveguide signal on a single path through the flight time of the waveguide signal. At the same time, it calculates the group velocity under the additional stress state in advance based on the known material parameters, establishes the corresponding relationship between the group velocity and the stress value, and finds the stress value under the current path through the calculated group velocity. The corresponding relationship between the group velocity and the stress value is established, including: The material is divided into grid cells, and the governing equation of wave motion for each cell is expressed as: ∫ Γ you (e)T t (e) dΓ=∫ V you (e)T (r (e) ü (e) )dV+∫ V not (e)T s (e) dV Among them, δu(e) and δε(e) represent the virtual displacement and virtual strain of the unit, respectively, t (e) and σ (e) represents the external force and internal stress vector, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second-order derivative with respect to time, Γ is the unit surface, and V is the unit volume; After assembling all unit matrices and applying stress conditions, the characteristic equation of the entire system is expressed as: (K1+ikK2+k 2 K3-ω 2 M)Q=0 Among them, the global stiffness matrix K1, K2, K3 and the global mass matrix M are obtained by solving the stiffness matrix of a single unit of the control equation and the mass matrix M (e) It is obtained that N represents the number of all mesh nodes, Q is the node displacement 3N×1 vector, C is the stiffness matrix, B is the element shape function, and dξ represents the grid line element differential; The group velocity corresponding to the stress is expressed as: Among them, Q L and Q R are the left eigenvector and the right eigenvector respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. The corresponding relationship between the group velocity and the stress value of the object is obtained, and then the corresponding stress value on the path is found by calculating the group velocity on a single path according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece.

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