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

Abstract

The present 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 assessment module, and an imaging output module. The guided wave excitation receiving module excites the ship structure and receives the guided wave signal from the ship structure, transmitting it to the signal processing module. The signal processing module preprocesses the received guided wave signal, extracts the signal's time domain and frequency domain characteristics, extracts stress-related information, and transmits it to the stress assessment module. The stress assessment module calculates the guided wave signal group velocity along different paths based on the guided wave signal's flight time, and calculates the stress field distribution of the ship structure under different operating conditions using the finite element method of material mechanical properties. The imaging output module generates a stress field distribution image of the ship structure in the detection area based on the stress field distribution. The present invention can realize stress field detection of ship structures under different operating conditions and 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 detection system and method based on ultrasonic guided waves. Background Art

[0002] With the rapid development of the shipbuilding industry, ship safety and reliability are receiving increasing attention. During operation, a ship's shell structure is subject to complex stresses, including static and dynamic loads, as well as environmental factors. These stresses can lead to material fatigue, crack propagation, and structural failure, compromising the overall safety of the ship. Therefore, timely and accurate detection and assessment of stress states in ship structures is crucial.

[0003] Traditional stress field detection methods primarily include physical measurement and destructive testing. Physical measurement methods typically rely on equipment such as strain gauges and pressure sensors. While these methods can provide certain stress data, they suffer from complex installation, high cost, and poor real-time performance in practical applications. Destructive testing methods require cutting or drilling into the ship structure. While they can obtain relatively accurate stress data, they can cause irreversible damage to the ship and are unsuitable for testing in-service vessels. In recent years, ultrasonic testing technology has garnered widespread attention due to its non-destructive, high-sensitivity, and real-time monitoring capabilities. Ultrasonic guided wave technology utilizes the propagation characteristics of sound waves in materials to effectively detect internal defects and stress states. By analyzing the reflection, scattering, and attenuation characteristics of ultrasonic waves as they propagate through the material, information about the material's stress field distribution can be obtained. However, existing ultrasonic guided wave testing systems still have some shortcomings in practical applications, such as complex signal processing, inaccurate stress assessment models, and a 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 that can overcome the shortcomings of existing technologies and achieve 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 existing technology, 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. It has the advantages of fast response speed, accurate detection and positioning of the stress field 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 guided wave excitation receiving module is used to excite the ship structure and receive the guided wave signal on the ship structure, and transmit the guided wave signal to the signal processing module;

[0009] The signal processing module is used to perform signal preprocessing on the received guided wave 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 assessment module is used to calculate the guided wave signal group velocity 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 and 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 an optimal 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 guided wave signal on different paths based on the flight time of the guided wave 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 measurement point based on the group velocity, and jointly evaluate the intersection of each path according to the stress condition on different paths to calculate the stress magnitude of all measurement points.

[0017] As a preferred technical solution, 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 condition changes specifically includes:

[0018] The stress assessment module calculates the group velocity of the guided wave signal on a single path through the flight time of the guided wave signal. It also pre-calculates the group velocity under the additional stress state based on known material parameters, establishes a corresponding relationship between the group velocity and the stress value, and uses the calculated group velocity to find the stress value under the current path.

[0019] Establish the corresponding relationship between group velocity and stress value, 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 vectors, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second derivative with respect to time, Γ is the unit surface, and V is the unit volume;

[0023] 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) We obtain: 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. From this, the corresponding relationship between the group velocity and the stress value of the target object is obtained. Then, according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece, the group velocity on a single path is calculated, and the corresponding stress value on the path is found.

[0033] The present invention also provides a ship structure stress field detection method based on ultrasonic guided waves, provided with the above-mentioned 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 guided wave 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 it to the stress assessment module;

[0036] The stress assessment module calculates the guided wave signal group velocity 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 guided wave signal on different paths based on the flight time of the guided wave 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 calculates the stress magnitude of the measurement point based on the group velocity. The intersection points of each path are jointly evaluated according to the stress conditions on different paths, and the stress magnitude of all measurement points is calculated.

[0039] As a preferred technical solution, 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 condition changes specifically includes:

[0040] The stress assessment module calculates the group velocity of the guided wave signal on a single path through the flight time of the guided wave signal. It also pre-calculates the group velocity under the additional stress state based on known material parameters, establishes a corresponding relationship between the group velocity and the stress value, and uses the calculated group velocity to find the stress value under the current path.

[0041] Establish the corresponding relationship between group velocity and stress value, including:

[0042] The material is divided into grid elements, and the governing equation of wave motion for each element 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 vectors, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second derivative with respect to time, Γ is the unit surface, and V is the unit volume;

[0045] 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) We obtain: 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. From this, the corresponding relationship between the group velocity and the stress value of the target object is obtained. Then, according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece, the group velocity on a single path is calculated, and the corresponding stress value on the path is found.

[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, which 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, it excites the ship structure and monitors its reflected signals. Ultrasonic guided waves can penetrate the material and effectively detect its internal defects and stress state, 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 these modules enables the system to operate flexibly in different working environments, 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. By deeply analyzing the time domain and frequency domain characteristics of the signal, it extracts information related to the stress state, such as amplitude, phase and frequency changes, which can effectively improve 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 can 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 and generates 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 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 Schematic diagram of the arrangement of piezoelectric sheets of the present invention;

[0064] Figure 3 A schematic diagram of the process of stress assessment module of the present invention for assessing stress magnitude;

[0065] Figure 4 The figure 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 solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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-test calibration module is used to perform self-test and calibration on the entire detection system, detecting the impact of uncontrollable factors such as installation conditions and temperature on the detection, and detecting system faults such as loose piezoelectric pieces to ensure that the system operates in optimal conditions.

[0070] Specifically, the pre-test calibration module includes but is not limited to a self-test function, an environmental impact detection function, and a fault diagnosis function. The self-test function is to start the self-test 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 a set frequency to the ship structure through high-frequency piezoelectric sensors, which 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, the received signal is ensured to maintain high quality and reduce signal attenuation and distortion.

[0073] like Figure 2 As shown, the guided wave excitation receiving module is provided with a probe and a piezoelectric sheet, wherein the piezoelectric sheets are all of the same specifications and are placed in a specified manner, including but not limited to at 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 guided wave excitation receiving module can be a single-frequency or multi-frequency transmitter, and the ultrasonic receiver has a wide-band receiving capability to adapt to 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, perform pre-processing such as alignment and filtering on the received reflected signal, analyze the time domain and frequency domain characteristics of the signal, and extract stress-related information;

[0076] In this embodiment, the signal processing module performs preprocessing such as alignment, filtering, and denoising on the received reflected signals to improve signal quality. It uses time-domain and frequency-domain analysis techniques to analyze the signal's amplitude, phase, frequency, and other characteristics, identifies changes related to the stress state, such as amplitude, phase, and frequency changes, extracts stress-related information, 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, to improve the analysis accuracy of signal features.

[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 provides an assessment of the degree of stress concentration based on this. It 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 actual measurement data.

[0080] In this embodiment, the stress assessment module first performs a preliminary assessment of the stress state of each path, estimating the average stress magnitude along the path. After completing the stress assessment of all individual paths, the module then performs a joint assessment of the intersections of the paths based on the stress states of the 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. 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 calculated group velocity is then used to quantitatively deduce the stress magnitude at the measurement point.

[0082] After calculating the stress magnitudes of all measurement points, the imaging output module images the inspection area according to the positions of each measurement point to display the stress field distribution in the inspection area.

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

[0084] The material is divided into grid elements, and the governing equation of wave motion for each element 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 unit, respectively, (e) and σ (e)represents the external force and internal stress vectors, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second 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 of 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 matrices K1, K2, K3, and M are of size 3N × 3N, where N represents the number of mesh nodes. Q is a 3N × 1 vector of nodal displacements, C is the stiffness matrix, B is a simplified element shape function for computational convenience, and dξ represents the element differential of the mesh line.

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

[0096]

[0097] where Q L and Q R where are the left and right eigenvectors, respectively, k is the corresponding wave number, ω is the corresponding angular frequency, and i is the imaginary unit. This allows us to determine the relationship between the group velocity and stress for the target object. We then use the flight time derived from the analysis signal, the distance from the piezoelectric patch, and the calculated group velocity along a single path to find the corresponding stress value for that 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 use the calculated stress field distribution data to form a stress field distribution image in the detection area, showing 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 and non-destructive detection of the stress state of ship structures. By jointly evaluating the stress states of different paths, it can more comprehensively understand the stress concentration areas, provide more accurate stress field distribution information, reduce the errors that may exist in traditional methods, and obtain stress data in real time, facilitating the timely discovery of potential structural problems and improving the safety of ships. 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 further 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 comprising 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, the ultrasonic transmitter transmits the ultrasonic guided wave signal to excite the ship structure, and the ultrasonic receiver receives 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. Then, frequency domain analysis is performed to extract the amplitude, phase, and variation 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 at different measurement points of the ship structure. Specifically, the following are performed:

[0110] First, a preliminary assessment of the stress state of each path is performed to evaluate the average stress magnitude on the path. After completing the stress assessment of all single paths, a joint assessment is performed on the intersections of the paths based on the stress conditions on the different paths 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. Combined with the material and geometry of the ship structure, the theoretical group velocity of the mode existing in the plate and the theoretical group velocity of the main mode when the stress condition changes are derived. The calculated group velocity is then used to quantitatively deduce the stress magnitude at the measurement point.

[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 uses ultrasonic guided wave technology to achieve efficient, accurate and non-destructive detection of ship structure stress fields. It 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 adverse 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 considered as equivalent replacement methods and are included in the scope of protection 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 guided wave excitation receiving module is used to excite the ship structure and receive the guided wave signal on the ship structure, and transmit the guided wave signal to the signal processing module; The signal processing module is used to perform signal preprocessing on the received guided wave 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 assessment module is used to calculate the guided wave signal group velocity 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 stress assessment module derives the theoretical group velocity of the mode existing in the ship deck, as well as the theoretical group velocity of the mode when the stress condition changes, and quantitatively calculates the stress magnitude at the measurement point based on the group velocity. The intersection points of each path are jointly evaluated according to the stress conditions on different paths to calculate the stress magnitude of all measurement points; The derivation of the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the mode when the stress condition changes specifically includes: The stress assessment module calculates the group velocity of the guided wave signal on a single path through the flight time of the guided wave signal. It also pre-calculates the group velocity under the additional stress state based on known material parameters, establishes a corresponding relationship between the group velocity and the stress value, and uses the calculated group velocity to find the stress value under the current path. Establish the corresponding relationship between group velocity and stress value, including: The material is divided into grid elements, and the governing equation of wave motion for each element is expressed as: 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 vectors, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second derivative with respect to time, Γ is the unit surface, and V is the unit volume; 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) We obtain: 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, 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 target object is thus obtained. Then, according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece, the group velocity on a single path is calculated, and the corresponding stress value on the path is found. 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 and 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 guided wave excitation receiving module transmits an ultrasonic signal of a set frequency to the ship structure through a high-frequency piezoelectric sensor, thereby exciting the material to generate guided waves.

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 piece. The piezoelectric piece 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.

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, and the signal preprocessing includes signal alignment processing, signal filtering processing and signal denoising processing.

6. A method for detecting stress fields of ship structures 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 5 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 guided wave 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 it to the stress assessment module; The stress assessment module calculates the guided wave signal group velocity 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 stress assessment module derives the theoretical group velocity of the mode existing in the ship deck, as well as the theoretical group velocity of the mode when the stress condition changes, and quantitatively calculates the stress magnitude at the measurement point based on the group velocity. The intersection points of each path are jointly evaluated according to the stress conditions on different paths to calculate the stress magnitude of all measurement points; The derivation of the theoretical group velocity of the mode existing in the ship deck and the theoretical group velocity of the mode when the stress condition changes specifically includes: The stress assessment module calculates the group velocity of the guided wave signal on a single path through the flight time of the guided wave signal. It also pre-calculates the group velocity under the additional stress state based on known material parameters, establishes a corresponding relationship between the group velocity and the stress value, and uses the calculated group velocity to find the stress value under the current path. Establish the corresponding relationship between group velocity and stress value, including: The material is divided into grid elements, and the governing equation of wave motion for each element is expressed as: 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 vectors, T represents the complex conjugate transpose, ρ (e) is the density, ∵ is the second derivative with respect to time, Γ is the unit surface, and V is the unit volume; 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) We obtain: 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, 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 target object is thus obtained. Then, according to the flight time obtained from the analysis signal and the distance from the piezoelectric piece, the group velocity on a single path is calculated, and the corresponding stress value on the path is found. 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.

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