Multi-field joint detection method for force transmission path change of deep flexural member

Abstract

The invention discloses a multi-field joint detection method for force transfer path change of a deep flexural member, relates to the technical field, and aims to solve the problems that the local bearing capacity of a structure is reduced and the uncertainty of a force transfer path is increased. Collecting crack width and concrete peeling thickness and area, calculating a cross section loss coefficient, determining pressure rod bearing width by combining the crack width, analyzing a crack density index after screening a target position, and judging whether a path migration signal is generated or not. After a signal is generated, acquiring strain data by using a fiber grating sensor, analyzing the characteristics of a force transmission path, detecting vibration acceleration, fusing the strain data and the vibration acceleration to evaluate a path reconstruction index, and judging whether the force transmission path is changed or not. The method effectively improves the monitoring precision and response speed of the deep flexural member, avoids potential faults, and guarantees the structural safety.

Description

Technical Field

[0001] The present invention relates to the field of data prediction and updating, and more particularly to a multi-field joint detection method for force transmission path changes of deep bending members. Background Art

[0002] Deeply flexural members under complex loads often exhibit significant shear-compression combined effects, non-uniform crack development, and localized concentration of damage zones, which can easily lead to significant force transmission path reconstruction. Existing structural health monitoring technologies mostly rely on single-type sensors such as strain gauges, displacement meters, and accelerometers, or invert the structural state through a limited number of physical quantity collection points. They lack the ability to systematically identify the continuous damage process from crack development to cross-section degradation to path change.

[0003] The existing technology has the following deficiencies: Currently, current crack identification methods are mostly based on manual inspection or image processing. The judgment of changes in the structural force transmission path is mostly based on overall deformation characteristics or simplified model deduction. These methods cannot provide effective judgment in the early stages of local damage, especially in the presence of microscopic cracks and local concrete spalling. This leads to a decrease in the local bearing capacity of the structure and an increase in the uncertainty of the force transmission path, which seriously affects the accuracy of damage identification and the reliability of structural safety assessment. Therefore, a multi-field joint detection method for force transmission path changes in deep-bending members is proposed.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a multi-field joint detection method for changes in the force transmission path of deep-bending members, which solves the problems raised in the above-mentioned background technology by using a multi-physical field coupling detection mechanism that combines laser scanning recognition, cross-section degradation assessment, fiber Bragg grating strain monitoring and vibration characteristic analysis.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a multi-field joint detection method for force transmission path changes in deep bending members, comprising the following steps: Step S1: using a laser scanner to identify and mark the crack locations of the deep-bending member, collect the crack width, concrete spalling thickness, and spalling area at the marked locations, and calculate the section loss coefficient using the concrete spalling thickness and spalling area; Step S2: Calculate the bearing width of the compression rod at the marked position by combining the crack width and the section loss coefficient at the marked position, select the target position according to the bearing width of the compression rod, detect the distance of each target position, analyze the crack density index of the deep bending member, and determine whether to generate a path migration signal; Step S3: After the path migration signal is generated, the strain data of each target position is collected based on the fiber grating sensor, the force transmission path characteristics of the target position are analyzed according to the strain data, and the vibration acceleration of each target position is detected; Step S4: After processing the vibration acceleration and force transmission path characteristics of each target, the path reconstruction index of the deep bending member is evaluated, and whether the force transmission path has changed is determined based on the path reconstruction index.

[0007] In a preferred embodiment, in step S1, the deep bending member is scanned by a laser scanner, and the timestamps of laser emission and reception are recorded; Calculate the distance from the laser scanner to the surface of the deep bending member based on the timestamps of laser emission and reception; The point cloud coordinates of each point on the surface of the deep bending member are obtained by calculating the distance from the laser scanner to the surface of the deep bending member; The point cloud coordinates of each point on the surface of the deep bending member are used as the target point in turn, and a spatial neighborhood is constructed with the target point as the center according to the preset radius, and the Z-axis height average of all point cloud coordinates in the spatial domain is calculated; The difference between the Z-axis height value of the target point and the average Z-axis height of all point cloud coordinate points in the spatial domain is taken as the crack characteristic value.

[0008] In a preferred embodiment, in step S1, the crack characteristic value is compared with a preset crack characteristic threshold to determine the crack position: If the crack characteristic value is less than 0 and the absolute value of the crack characteristic value is greater than the crack characteristic value threshold, the target point is determined to be the crack location; Otherwise, it is determined that the target point is not the crack location; The crack position is to screen candidate crack points in the spatial domain, and all the candidate crack points obtained by screening constitute the marked position; The distance between each pair of adjacent points is calculated using the point cloud coordinates on both sides of the marked position, and the maximum distance between the adjacent points is taken as the crack width at the marked position.

[0009] In a preferred embodiment, in step S2, only the point cloud coordinates of the marked position are retained. Axis and Axis coordinates and projected onto On a plane; Get the encirclement through the convex hull algorithm The minimum convex hull polygon of all points on the plane; The concrete spalling area at the marked position is calculated by the vertex coordinates of the minimum convex hull polygon; According to the marked position The maximum absolute value of the axis and the coordinates of all point clouds at non-marked positions The absolute value of the difference between the axis mean values ​​is taken as the concrete spalling thickness at the marked position; The section loss coefficient is calculated based on the concrete spalling thickness and concrete spalling area at the marked position.

[0010] In a preferred embodiment, in step S2, the bearing width of the compression rod at the marked position is calculated by comprehensively considering the crack width at the marked position and the section loss coefficient; If the pressure bar bearing width at the marked position is greater than the preset pressure bar bearing width threshold, it is determined that the marked position meets the bearing width requirement; Otherwise, it is judged that the mark position does not meet the load width requirement; The marked position that meets the load width requirement is recorded as the target position; Calculate the distance of each target position according to the point cloud coordinates of the target position, and calculate the crack density index based on the distance of each target position; If the crack density index is greater than or equal to a preset crack density index threshold, a path migration signal is generated; Otherwise, no path migration signal is generated.

[0011] In a preferred embodiment, in step S3, the strain data of the target position includes the strain peak value and the strain amplitude of the target position; The acquisition period is preset, and the central wavelength of the fiber Bragg grating reflection is recorded by the fiber Bragg grating sensor; During the acquisition cycle, the difference between the central wavelength collected at each acquisition moment and the central wavelength at the first acquisition moment is taken as the change in the central wavelength at the corresponding acquisition moment; Calculate the strain value at the target position according to the change in the central wavelength; The difference between the maximum and minimum strain values ​​at the target position is divided by 2 as the strain amplitude at the target position.

[0012] In a preferred embodiment, in step S3, the strain peak value at the target position and the strain amplitude at the target position are integrated and weighted to obtain the force transmission path characteristics; The vibration signal at the target position is collected by the vibration sensor and converted into an electrical signal, and the electrical signal is recorded by the vibration analyzer and converted into the vibration acceleration of the target position.

[0013] In a preferred embodiment, in step S4, the vibration acceleration and force transmission path characteristics of each target position are normalized and then the path reconstruction index is calculated.

[0014] In a preferred embodiment, in step S4, if the path reconstruction index is greater than or equal to a preset path reconstruction index threshold, the force transmission path changes; If the path reconstruction index is less than the preset path reconstruction index threshold, the force transmission path has not changed.

[0015] The technical effects and advantages of the present invention are as follows: The present invention uses a laser scanner to identify and mark the crack positions of deep-bending members, collects crack width, concrete spalling thickness and spalling area, calculates the section loss coefficient using the spalling thickness and area, calculates the compression rod bearing width in combination with the crack width and section loss coefficient, screens the target position and analyzes the crack density index to determine whether a path migration signal is generated. After the path migration signal is generated, the present invention uses a fiber grating sensor to collect strain data, analyzes the force transmission path characteristics and detects vibration acceleration. Through comprehensive processing of vibration acceleration and force transmission path characteristics, the path reconstruction index is evaluated to further determine whether the force transmission path has changed, effectively improving the accuracy and response speed of deep-bending member monitoring, avoiding the occurrence of potential faults, ensuring structural safety, and realizing dynamic tracking and early warning of the component damage evolution process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart for implementing a multi-field joint detection method for force transmission path changes of deep bending members according to the present invention.

[0017] Figure 2 This is a schematic diagram of the steps of a multi-field joint detection method for force transmission path changes of deep bending members according to the present invention. DETAILED DESCRIPTION

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

[0019] The present invention uses a laser scanner to identify and mark the crack positions of deep-bending members, collects crack width, concrete spalling thickness and spalling area, calculates the section loss coefficient using the spalling thickness and area, calculates the compression rod bearing width in combination with the crack width and the section loss coefficient, screens the target position and analyzes the crack density index to determine whether a path migration signal is generated. After the path migration signal is generated, the present invention uses a fiber grating sensor to collect strain data, analyzes the force transmission path characteristics and detects vibration acceleration. Through comprehensive processing of vibration acceleration and force transmission path characteristics, the path reconstruction index is evaluated to further determine whether the force transmission path has changed, thereby effectively improving the accuracy and response speed of deep-bending member monitoring, avoiding the occurrence of potential faults, and ensuring structural safety.

[0020] Example 1, a multi-field joint detection method for the change of force transmission path of deep bending members, such as Figures 1 to 2 As shown, the following steps are included: Step S1: using a laser scanner to identify and mark the crack locations of the deep-bending member, collect the crack width, concrete spalling thickness, and spalling area at the marked locations, and calculate the section loss coefficient using the concrete spalling thickness and spalling area; Step S2: Calculate the bearing width of the compression rod at the marked position by combining the crack width and the section loss coefficient at the marked position, select the target position according to the bearing width of the compression rod, detect the distance of each target position, analyze the crack density index of the deep bending member, and determine whether to generate a path migration signal; Step S3: After the path migration signal is generated, the strain data of each target position is collected based on the fiber grating sensor, the force transmission path characteristics of the target position are analyzed according to the strain data, and the vibration acceleration of each target position is detected; Step S4: After processing the vibration acceleration and force transmission path characteristics of each target, the path reconstruction index of the deep bending member is evaluated, and whether the force transmission path has changed is determined based on the path reconstruction index.

[0021] The specific implementation is as follows: In step S1, the deep bending member is fully scanned by a laser scanner, and the timestamp of each laser emission and reception by the laser scanner is recorded according to the internal clock unit of the laser scanner; The absolute value of the difference between the laser emission and reception timestamps is divided by 2 to obtain the one-way propagation time. The product of the one-way propagation time and the laser emission speed of the laser scanner is used as the distance from the laser scanner to the surface of the deep bending member. The point cloud coordinates of each point on the surface of the deep-bending member are obtained by combining the preset laser scanner installation information and the distance from the laser scanner to the surface of the deep-bending member through trigonometric function calculation.

[0022] It needs to be explained that a laser scanner is a device that uses laser technology to collect three-dimensional spatial data, and is used to perform comprehensive scanning of deep-bending members; the internal clock unit of the laser scanner is responsible for precise time measurement to ensure the time synchronization and accuracy of the laser scanner during measurement, and is used to record the timestamp of each laser emission and reception of the laser scanner; the preset laser scanner installation information refers to the installation position, angle, direction and other installation-related parameters of the laser scanner in the system, which are set by professionals according to the on-site implementation situation; trigonometric functions are used to describe the relationship between angles and right-angled triangles, and the sine function is used to calculate the distance from the laser scanner to the surface of the object and the vertical scanning angle of the laser scanner to obtain the z-axis coordinate of the object surface, and the cosine function is used to calculate the distance from the laser scanner to the surface of the object, the vertical scanning angle of the laser scanner and the horizontal scanning angle of the millimeter-wave radar to obtain the x-axis and y-axis coordinates of the object surface, forming a point cloud coordinate set of the surface of the deep-bending member.

[0023] The point cloud coordinates of each point on the surface of the deep bending member are used as the target point in turn. With the target point as the center, a spatial neighborhood is constructed according to the preset radius, and the Z-axis height average of all point cloud coordinates in the spatial domain is calculated; The difference between the Z-axis height value of the target point and the average Z-axis height value of all point cloud coordinate points in the spatial domain is used as the crack characteristic value; The crack characteristic value refers to the height deviation of the target point relative to the point cloud coordinates in its spatial domain, reflecting whether the target point has a concave trend in the Z-axis direction; Compare the crack characteristic value with the preset crack characteristic threshold to determine the crack location: If the crack characteristic value is less than 0 and the absolute value of the crack characteristic value is greater than the crack characteristic value threshold, the target point is determined to be the crack location; Otherwise, it is determined that the target point is not a crack location.

[0024] Taking the crack position as the starting point and the preset scale radius as the scale, a spatial neighborhood is constructed, and the crack positions in the spatial neighborhood are screened as candidate crack points. Then, each candidate crack point is used as a new starting point, and the above spatial neighborhood construction and screening operations are repeated until there is no crack position in the spatial neighborhood of the candidate crack point, and all candidate crack points constitute the marked position.

[0025] It should be explained that the preset scale radius refers to the maximum identification distance extending outward from the current crack position. When the spatial distance between two crack positions is less than or equal to the scale radius, it indicates that there is connectivity. The specific scale radius value is set by professionals.

[0026] Extract the point cloud coordinates on both sides of the marked position through area search; The distance between each pair of adjacent points is calculated by the point cloud coordinates on both sides of the marked position. The calculation formula is: , in, 、 and is the point cloud coordinate on one side of the crack, and is the point cloud coordinate corresponding to the other side of the crack, is the distance between a pair of adjacent points; The maximum distance between adjacent points is taken as the crack width at the marked position; Traverse the point cloud coordinates of the marked position and filter out the point cloud coordinates The point cloud coordinates with the largest absolute value of the axis coordinates are traversed to calculate the point cloud coordinates of all non-marked positions. Axis mean, mark the midpoint cloud coordinates The point cloud coordinate with the largest absolute value of the axis coordinate Axis coordinate values ​​and all point cloud coordinates at non-marked locations The absolute value of the difference between the axis mean values ​​is taken as the concrete spalling thickness at the marked position; Keep only the point cloud coordinates of the marked position Axis and Axis coordinates and projected onto On the plane, the convex hull algorithm is used to obtain the enclosed The minimum convex hull polygon of all points on the plane; The concrete spalling area is calculated by the vertex coordinates of the minimum convex hull polygon. The calculation formula is: ,in, and The convex hull polygon The coordinates of the vertices and the coordinates of the adjacent vertices, is the number of vertices of the convex hull polygon, is the concrete spalling area at the marked location; The point cloud coordinates of each point on the surface of the deep bending member The absolute value of the maximum and minimum values ​​of the axis coordinates are added together as the thickness of the deep bending member; The area of ​​the deep bending member is calculated by the convex hull algorithm mentioned above; The section loss coefficient is calculated by combining the concrete spalling thickness and concrete spalling area at the marked position with the thickness and area of ​​the deep-flexural member. The calculation formula is: ,in, and is the concrete spalling thickness and concrete spalling area at the marked position, and is the thickness and area of ​​the deep bending member, is the cross-sectional loss coefficient; It should be explained that the preset radius is used to fix the area of ​​the point cloud position, which is convenient for judging whether the point is the target point and is set by professionals; field search refers to data query within a specific field or range, which is used to extract the point cloud coordinates on both sides of the crack; the preset crack feature threshold is an important parameter used to judge whether the target point is the marked position, which is set by professionals; the convex hull algorithm is used to find the convex hull of a set of two-dimensional points to calculate the concrete spalling area and the area of ​​deep bending members.

[0027] In step S2, the crack width at the marked position and the section loss coefficient are combined to calculate the bearing width of the compression rod at the marked position. The calculation formula is: ,in, is the crack width at the marked position, is the cross-sectional loss coefficient, is the bearing width of the compression rod at the marked position; Compare the pressure bar bearing width at the marked position with the preset pressure bar bearing width threshold to determine: If the pressure bar bearing width at the marked position is greater than the preset pressure bar bearing width threshold, it is determined that the marked position meets the bearing width requirement; If the pressure bar bearing width at the marked position is less than or equal to the preset pressure bar bearing width threshold, it is determined that the marked position does not meet the bearing width requirement; The marked position that meets the load width requirement is recorded as the target position; Calculate the distance to each target position using the following formula: ,in, and For the The point cloud coordinate value of the target position, and For the The point cloud coordinate value of the target position, is the distance between the two target positions; The crack density index is calculated based on the distance of each target position. The calculation formula is: ,in, is the distance between the two target positions, is the area of ​​the deep bending member, is the crack density index; Compare the crack density index with the preset crack density index threshold to determine: If the crack density index is greater than or equal to a preset crack density index threshold, a path migration signal is generated; If the crack density index is less than the preset crack density index threshold, no path migration signal is generated; It needs to be explained that the preset pressure rod bearing width threshold is a key parameter, which is used to determine the maximum width that the pressure rod can bear under specific conditions and is set by professionals; the preset crack density index threshold is a standard value used to evaluate the crack density of an object and is set by professionals.

[0028] In step S3, the strain data at the target location generally refers to the strain measured around the crack or at the crack itself. The strain data reflects the deformation of the material or structure under stress, including the strain peak value and strain amplitude at the target location. The collection period is preset, and the central wavelength of the fiber Bragg grating reflection at each collection moment is recorded by the fiber Bragg grating sensor; During the acquisition cycle, the difference between the central wavelength collected at each acquisition moment and the central wavelength at the first acquisition moment is taken as the change in the central wavelength at the corresponding acquisition moment; The strain value at the target position is calculated based on the change in the central wavelength. The calculation formula is: ,in, is the change in the central wavelength reflected by the fiber Bragg grating, is the original central wavelength reflected by the grating, is the refractive index of the fiber Bragg grating reflection, is the strain value at the target position; Compare the strain values ​​of the target position at different acquisition times to obtain the maximum strain value of the target position at the acquisition time as the strain peak value of the target position; The difference between the maximum and minimum strain values ​​at the target position is divided by 2 as the strain amplitude at the target position; The force transmission path characteristics are calculated by combining the strain peak value and the strain amplitude at the target position. The calculation formula is: ,in, is the peak strain value at the target position, is the maximum value of the strain peaks among all target positions, is the strain amplitude at the target position, and is the preset weighting coefficient, is the force transmission path characteristic; It should be noted that the preset weighting coefficient is used to adjust the influence of the strain peak value and the strain amplitude at the target position on the force transmission path characteristics, and is set by professionals; The larger the strain amplitude and strain peak value at the target position, the greater the force transmission fluctuation at the target position, the more uneven the force transmission, and the greater the force transmission path characteristics; The smaller the strain amplitude and strain peak value at the target position, the smaller the force transmission fluctuation at the target position, the smoother the force transmission, and the smaller the force transmission path characteristics; The vibration signal of the target position is collected by a vibration sensor and converted into an electrical signal, the electrical signal is recorded by a vibration analyzer and converted into vibration acceleration according to analog-to-digital conversion; It needs to be explained that the preset acquisition period refers to the pre-set time interval during the data acquisition process, which is used to determine the frequency of data collection; the fiber grating sensor is a sensor based on the principle of grating reflection in optical fiber, which is used to record the central wavelength of fiber grating reflection; the vibration sensor is a device for monitoring the vibration of an object, which is used to collect the vibration signal at the target position and convert it into an electrical signal; the vibration analyzer is a device specifically used to measure, analyze and diagnose the vibration state of an object, which is used to record electrical signals and obtain vibration acceleration; analog-to-digital conversion is the process of converting analog signals into digital signals, which is used to convert electrical signals into vibration acceleration.

[0029] In step S4, by The normalization method processes the vibration acceleration and force transmission path characteristics of each target position to obtain the normalized values ​​of the vibration acceleration and force transmission path characteristics of each target. The normalized values ​​are: ,in, and are the force transmission path characteristics and vibration acceleration at the target position, and are the force transmission path characteristics of each target and the maximum and minimum values ​​of vibration acceleration, and are the force transmission path characteristics and normalized vibration acceleration values ​​of each target position; The path reconstruction index is calculated by combining the force transmission path characteristics of each target position with the normalized value of the vibration acceleration. The path reconstruction index is: ,in, is the number of target locations, For the The normalized value of the vibration acceleration at the target position, For the The normalized value of the force transmission path characteristics at each target position, Reconstruct index for the path; The larger the normalized value of the force transmission path characteristics and vibration acceleration at the target position is, the greater the dynamic change of the force at the target position is, the more significant the force transmission at the target position is, and the larger the path reconstruction index is; The smaller the normalized value of the force transmission path characteristics and vibration acceleration at the target position is, the smaller the dynamic change of the force at the target position is, the smaller the change of the force transmission path is, and the smaller the path reconstruction index is; It should be noted that Indicates the intensity of the change in vibration acceleration. When the vibration acceleration increases, it indicates that the force dynamics at that location have changed significantly, and the impact on the force transmission path of the structure will also increase. Indicates the intensity of the change in the force transmission path characteristics. If the force transmission path characteristics at a certain target location change significantly, it means that the force transmission method or path has changed significantly, which means that there is a problem with the structure or material in that area. It reflects the interaction between vibration acceleration and force transmission path characteristics. If the vibration acceleration and force transmission path characteristics change significantly at the same time, it means that the change of force transmission path is more complex or drastic. Compare the path reconstruction index with the preset path reconstruction index threshold to determine whether the force transmission path has changed: If the path reconstruction index is greater than or equal to the preset path reconstruction index threshold, the force transmission path changes; If the path reconstruction index is less than the preset path reconstruction index threshold, the force transmission path has not changed; What needs to be explained is that The normalization method is a common numerical normalization technique used to normalize the vibration acceleration and force transmission path characteristics of each target position; the preset path reconstruction index threshold is an important parameter for determining whether the force transmission path has changed. It is set by professionals and will not be elaborated here.

[0030] The change in the force transmission path reflects the evolution trend of the internal force mode of the deep-bending member structure and is an important indicator of the structural health status. By integrating the vibration acceleration and the force transmission path characteristics to construct a path reconstruction index, and based on the path reconstruction index to judge whether the path has changed, the potential risk of structural instability or local failure can be identified in advance, providing a scientific basis for structural safety assessment, operation and maintenance strategy formulation and fault prevention and control.

[0031] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0032] Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0033] As used herein, the singular forms "a," "an," and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include," "comprising," "having," and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Furthermore, the term "and / or" as used in this specification includes any and all combinations of the relevant listed items.

[0034] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referenced to each other.

[0035] The above description of the disclosed embodiments will enable those skilled in the art to implement or use various modifications of these embodiments, and it will be apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-field joint detection method for force transmission path changes in deep bending members, characterized by: The steps include: Step S1: using a laser scanner to identify and mark the crack locations of the deep-bending member, collect the crack width, concrete spalling thickness, and spalling area at the marked locations, and calculate the section loss coefficient using the concrete spalling thickness and spalling area; Step S2: Calculate the bearing width of the compression rod at the marked position by combining the crack width and the section loss coefficient at the marked position, select the target position according to the bearing width of the compression rod, detect the distance of each target position, analyze the crack density index of the deep bending member, and determine whether to generate a path migration signal; Step S3: After the path migration signal is generated, the strain data of each target position is collected based on the fiber grating sensor, the force transmission path characteristics of the target position are analyzed according to the strain data, and the vibration acceleration of each target position is detected; Step S4: After processing the vibration acceleration and force transmission path characteristics of each target, the path reconstruction index of the deep bending member is evaluated, and whether the force transmission path has changed is determined based on the path reconstruction index.

2. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 1, characterized in that: In step S1, the deep bending member is scanned by a laser scanner, and the timestamps of laser emission and reception are recorded; Calculate the distance from the laser scanner to the surface of the deep bending member based on the timestamps of laser emission and reception; The point cloud coordinates of each point on the surface of the deep bending member are obtained by calculating the distance from the laser scanner to the surface of the deep bending member; The point cloud coordinates of each point on the surface of the deep bending member are used as the target point in turn, and a spatial neighborhood is constructed with the target point as the center according to the preset radius, and the Z-axis height average of all point cloud coordinates in the spatial domain is calculated; The difference between the Z-axis height value of the target point and the average Z-axis height of all point cloud coordinate points in the spatial domain is taken as the crack characteristic value.

3. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 2, characterized in that: In step S1, the crack characteristic value is compared with the preset crack characteristic threshold to determine the crack location: If the crack characteristic value is less than 0 and the absolute value of the crack characteristic value is greater than the crack characteristic value threshold, the target point is determined to be the crack location; Otherwise, it is determined that the target point is not the crack location; The crack position is to screen candidate crack points in the spatial domain, and all the candidate crack points obtained by screening constitute the marked position; The distance between each pair of adjacent points is calculated using the point cloud coordinates on both sides of the marked position, and the maximum distance between the adjacent points is taken as the crack width at the marked position.

4. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 3, characterized in that: In step S2, only the point cloud coordinates of the marked position are retained Axis and Axis coordinates and projected onto On a plane; Get the encirclement through the convex hull algorithm The minimum convex hull polygon of all points on the plane; The concrete spalling area at the marked position is calculated by the vertex coordinates of the minimum convex hull polygon; According to the marked position The maximum absolute value of the axis and the coordinates of all point clouds at non-marked positions The absolute value of the difference between the axis mean values ​​is taken as the concrete spalling thickness at the marked position; The section loss coefficient is calculated based on the concrete spalling thickness and concrete spalling area at the marked position.

5. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 4, characterized in that: In step S2, the bearing width of the compression rod at the marked position is calculated by combining the crack width at the marked position with the section loss coefficient; If the pressure bar bearing width at the marked position is greater than the preset pressure bar bearing width threshold, it is determined that the marked position meets the bearing width requirement; Otherwise, it is judged that the mark position does not meet the load width requirement; The marked position that meets the load width requirement is recorded as the target position; Calculate the distance of each target position according to the point cloud coordinates of the target position, and calculate the crack density index based on the distance of each target position; If the crack density index is greater than or equal to a preset crack density index threshold, a path migration signal is generated; Otherwise, no path migration signal is generated.

6. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 1, characterized in that: In step S3, the strain data of the target position includes the strain peak value and the strain amplitude of the target position; The acquisition period is preset, and the central wavelength of the fiber Bragg grating reflection is recorded by the fiber Bragg grating sensor; During the acquisition cycle, the difference between the central wavelength collected at each acquisition moment and the central wavelength at the first acquisition moment is taken as the change in the central wavelength at the corresponding acquisition moment; Calculate the strain value at the target position according to the change in the central wavelength; The difference between the maximum and minimum strain values ​​at the target position is divided by 2 as the strain amplitude at the target position.

7. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 6, characterized in that: In step S3, the strain peak value at the target position and the strain amplitude at the target position are combined to obtain the force transmission path characteristics through weighted calculation; The vibration signal at the target position is collected by the vibration sensor and converted into an electrical signal, and the electrical signal is recorded by the vibration analyzer and converted into the vibration acceleration of the target position.

8. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 7, characterized in that: In step S4, the vibration acceleration and force transmission path characteristics of each target position are normalized and then the path reconstruction index is calculated.

9. The multi-field joint detection method for force transmission path changes of deep bending members according to claim 8, characterized in that: In step S4, if the path reconstruction index is greater than or equal to the preset path reconstruction index threshold, the force transmission path changes; If the path reconstruction index is less than the preset path reconstruction index threshold, the force transmission path has not changed.

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