Typical engineering target rapid damage assessment method based on image recognition technology

Abstract

The invention belongs to the field of damage assessment, and relates to a typical engineering target rapid damage assessment method based on an image recognition technology, and the method comprises the steps: building different types of image damage feature damage assessment criteria: obtaining damage pictures and anti-explosion damage data, carrying out the classification of damage grades, drawing a P-I curve graph, defining the damage grade and the critical state of damage, and carrying out the calculation of the damage assessment criteria; adopting a cyclic interpolation method to obtain a failure critical condition, a critical progressive impulse and a critical progressive overpressure, substituting into a classical P-I curve expression for fitting to obtain a failure critical curve expression, and further simulating to obtain a failure critical area; establishing a corresponding relationship between the damage assessment criterion-damage critical area and the damage level of the image damage feature under the engineering target category; a damage picture is shot, the damage area is extracted, the damage area is compared with the image damage feature damage evaluation criterion, and the damage level is rapidly determined. According to the method, the mapping relation between the image damage characteristics and the structural mechanical response is established, so that the damage level is quickly researched and judged.

Description

Technical Field

[0001] The present invention belongs to the technical field of weapon damage assessment, and particularly relates to a method for rapid damage assessment of typical engineering targets based on image recognition technology. Background Art

[0002] Weapon damage assessment, as a key supporting link in the modern military decision-making system, its core value lies in providing decision-making support for combat command through scientific and quantitative dynamic judgment. This technology can not only assist commanders in real-time mastering the actual effectiveness of combat operations, but also provide an engineering basis for the optimization and adjustment of subsequent strike strategies. At the technical implementation level, the pressure-impulse curve method (P-I curve method) has become one of the most valuable quantitative criteria for explosion damage assessment in the field of engineering applications due to its accurate characterization of the anti-explosion characteristics of structures.

[0003] In military strikes and disaster assessment practices, for critical infrastructure composed of typical concrete components such as beams, slabs, and columns, the current P-I curve method exposes significant technical bottlenecks. Although the prediction model constructed by this method based on mechanical parameters such as deflection-span ratio, structural rotation angle, and concrete spalling thickness has shown excellent guidance in pre-war strike plan planning, in the post-war damage assessment scenario, its characteristic of relying on precise parameter measurement leads to limited practical applications. Especially in complex battlefield or post-disaster environments, restricted by two major core contradictions: ① the contradiction between the security and timeliness of sensor network deployment; ② the contradiction between the feasibility and accuracy of manual detection in dangerous areas, the acquisition of key parameters faces severe challenges. Traditional assessment methods have been difficult to meet the dual requirements of modern combat and emergency rescue for the immediacy of situation awareness and the reliability of assessment results.

[0004] It is worth looking forward to that with the breakthrough development of frontier technologies such as computer vision, unmanned aerial vehicle clusters, and intelligent analysis of multi-source heterogeneous data, real-time panoramic imaging and multi-dimensional data collection in battlefield and post-disaster environments have become possible. Under this technical background, how to deeply mine the damage characteristics of the image data of damaged targets, construct a damage assessment method based on image damage characteristics, and then achieve non-contact rapid damage assessment has become a technical high point that urgently needs to be overcome in the current fields of military engineering and emergency management. This research direction not only concerns the paradigm innovation of assessment methods, but also has important strategic value for improving battlefield response speed and reducing the risk of casualties. Summary of the Invention

[0005] The purpose of the present invention is to solve the above-mentioned disadvantages existing in the prior art, and to propose a method for rapid damage assessment of typical engineering targets based on image recognition technology, so as to achieve rapid and efficient damage assessment.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions: A typical engineering target rapid damage assessment method based on image recognition technology, comprising the following steps: Establish corresponding image damage feature damage assessment criteria according to the typical engineering target category. The specific method is as follows: Obtain the damage pictures and anti-explosion damage data of the engineering target, conduct damage level division and draw a P-I curve graph, and define different damage levels and damage critical states according to the explosion damage degree and characteristics; For the fixed overpressure scatter points, fixed impulse scatter points, limit overpressure scatter points and limit impulse scatter points respectively, use the cyclic interpolation method to obtain the damage critical conditions, critical progressive impulse and critical progressive overpressure, and substitute them into the classical P-I curve expression for fitting to obtain the expression of the damage critical curve; According to the expression of the damage critical curve, simulate the new damage critical conditions to obtain damage pictures and anti-explosion damage data, and identify the damage pictures of each new damage critical condition through the image damage feature recognition program to obtain the damage area; Calculate the average value of the damage areas of the same type of damage critical conditions to obtain the damage critical area; Establish the image damage feature damage assessment criteria under this engineering target category, and the image damage feature damage assessment criteria is the corresponding relationship between the damage critical area and the damage level; Take the damage pictures of the engineering target after damage; Input the damage pictures into the image damage feature extraction program to extract and obtain the damage area; Determine the corresponding image damage feature damage assessment criteria of the photographed engineering target according to the typical engineering target category; Compare the extracted damage area with the corresponding image damage feature damage assessment criteria to quickly determine the damage level of the photographed engineering target, realizing the rapid damage assessment of the engineering target.

[0007] Preferably, the cyclic interpolation method comprises the following steps: S1-1: Find two explosion conditions with two different damage levels and each closest to the damage critical, and denote them as blasting condition a and blasting condition b respectively; S1-2: Numerically average the overpressure P and impulse I of blasting condition a and blasting condition b respectively to obtain a new blasting condition, denoted as blasting condition n; S1-3: Conduct numerical simulation or experimental research on blasting condition n, obtain damage pictures and anti-explosion damage data, and conduct damage level division on this blasting condition n according to the anti-explosion damage data and draw it on the P-I curve graph; S1-4. If the damage level of blasting condition n is the same as that of blasting condition a, replace blasting condition a with blasting condition n, and then re-execute S1-2 to S1-4; if the damage level of blasting condition n is the same as that of blasting condition b, replace blasting condition b with blasting condition n, and then re-execute S1-2 to S1-4; if blasting condition n falls on the damage critical condition, then the current blasting condition n is the damage critical condition.

[0008] Preferably, the blasting conditions include: selecting a fixed overpressure and different impulses increasing in sequence as the blasting conditions; selecting a fixed impulse and different overpressures increasing in sequence as the blasting conditions; selecting a limit overpressure and different impulses increasing in sequence as the blasting conditions; selecting a limit impulse and different overpressures increasing in sequence as the blasting conditions.

[0009] Preferably, the anti-explosion damage data includes: deflection-span ratio, structural rotation angle, and spalling thickness.

[0010] Preferably, the damage levels are divided into mild damage, moderate damage, severe damage, and complete damage.

[0011] Preferably, the damage critical states include moderate damage critical, severe damage critical, and complete damage critical. The critical state between mild damage and moderate damage is defined as moderate damage critical, the critical state between moderate damage and severe damage is defined as severe damage critical, and the critical state between severe damage and complete damage is defined as complete damage critical.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The innovative breakthrough of the present invention lies in constructing a damage assessment framework of "image damage characteristics - mechanical response". By using mature image recognition technology, the damage characteristics in the images of typical engineering targets are identified and extracted, and the extraction results are compared with the preset damage assessment criteria. By establishing the mapping relationship between the image damage characteristics and the structural mechanical response, the rapid judgment of the damage level of engineering targets is realized. This method breaks through the physical limitations of data acquisition in complex battlefield environments, realizes fast and safe non-contact assessment, can improve military decision-making efficiency, reduce personnel risks, and provides key technical support for forming an intelligent combat chain of "detection - assessment - attack". It is urgent to protect the patent to promote technology transformation and application. Description of the Drawings

[0013] Figure 1 It is a typical P-I curve diagram in the prior art. Figure 1 (a) is a schematic diagram of the P-I curve. Figure 1 (b) is a diagram of the P-I curve grade division. Figure 2Flow chart for establishing damage assessment criteria for image damage features in an embodiment of the present invention; Figure 3 Flow chart for a rapid damage assessment method based on image recognition in an embodiment of the present invention; Figure 4 Damage picture of the experimental results of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 5 Damage picture of the simulation results of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 6 Fixed overpressure scatter plot and fixed impulse scatter plot of the simulation results of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 7 Ultimate overpressure scatter plot and ultimate impulse scatter plot of the simulation results of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 8 Time - history curve of the damaged area of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 9 Time - history curve of the deflection - span ratio of the cross - beam and slab composite structure in an embodiment of the present invention; Figure 10 Damage assessment criterion diagram for image damage features of the cross - beam and slab composite structure in an embodiment of the present invention. Detailed implementation manners

[0014] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0015] To make the above - mentioned objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0016] A typical P - I curve is as Figure 1 shown, and its core mechanism lies in constructing a correlation response model between the overpressure value and the impulse value of the explosion load. Figure 1 (a) The P - I curve shown divides the coordinate plane into two characteristic regions through the critical failure curve: when the explosion parameters fall below the curve to the lower left, the damage degree of the component is lower than the preset damage threshold; when the explosion parameters are above the curve to the upper right, it means that the component structure has suffered substantial damage exceeding the expected value. Figure 1(b) The corresponding P-I curve divides the area into multiple regions, which respectively correspond to different degrees of damage of the component. Each region corresponds to a certain degree of damage, namely mild damage, moderate damage, severe damage, and complete damage. The overpressure and impulse corresponding to the explosion load fall into a certain region. By determining the region where the explosion parameters are located, the accurate calibration of the damage level can be achieved. This grading evaluation mechanism significantly improves the engineering applicability of damage prediction.

[0017] The rapid damage assessment method for typical engineering targets provided by the embodiments of the present invention has the core of establishing a damage assessment criterion for image damage characteristics. The overall idea is to conduct experiments or numerical simulation calculations under different explosion conditions to obtain the damage images and damage levels under these explosion conditions, so as to establish the corresponding relationship between the damage images and the damage levels. However, due to the high cost of explosion experiments and the large amount of time and computing power consumed by explosion simulations, it is difficult to simulate all blasting conditions in the entire P-I diagram. Therefore, the embodiments of the present invention adopt a calculation strategy of "selecting some blasting conditions, obtaining the damage critical conditions through cyclic interpolation method, fitting the damage critical conditions to obtain the curve expression of the damage critical conditions, and using the expression to find more damage critical conditions".

[0018] As Figure 2 shown, the specific steps for establishing the damage assessment criterion for image damage characteristics are as follows: S1. Determine the type of engineering target to be studied. Typical types of engineering targets such as beams, plates, columns, walls, etc. belong to the common classification methods in blasting science.

[0019] For example, the type of engineering target in the embodiments of the present invention is a cross-shaped beam and plate composite structure.

[0020] S2. Select different blasting conditions to conduct anti-explosion experiments or simulations on the engineering target, obtain the damage pictures and anti-explosion damage data under this blasting condition, divide the damage level of this blasting condition according to the anti-explosion damage data and plot it on the P-I diagram; the critical state between different damage levels is called the "damage critical state", and the blasting condition corresponding to the damage critical state is called the damage critical condition.

[0021] The "different blasting conditions" include the following four types: ① Select a fixed overpressure and different impulses that increase sequentially as the blasting conditions; ② Select a fixed impulse and different overpressures that increase sequentially as the blasting conditions; ③ Select an extreme overpressure and different impulses that increase sequentially as the blasting conditions; ④ Select an extreme impulse and different overpressures that increase sequentially as the blasting conditions. The extreme overpressure refers to an extremely high overpressure value. Under this overpressure condition, the impulse of the damage critical condition tends to the impulse fixed value, and this impulse fixed value is called the "critical asymptotic impulse I sn ". The "damage critical condition" is drawn on the P-I diagram in the shape of Figure 1As shown in (a), when the overpressure increases infinitely, the impulse I gradually approaches a fixed value; when the impulse increases infinitely, the overpressure P gradually approaches a fixed value. The so-called limit overpressure / limit impulse refers to taking a very large value of P or I.

[0022] The limit impulse refers to a situation where the impulse value is extremely high. Under this impulse condition, the overpressure that destroys the critical condition tends to the overpressure fixed value, and this overpressure fixed value is called the "critical progressive overpressure P sn ". In this embodiment, the fixed overpressure is taken as 0.22 MPa, the fixed impulse is taken as 11 MPa×ms, the limit overpressure is taken as 0.3 MPa, and the limit impulse is taken as 60 MPa×ms. There are three types of critical damage conditions: moderate / severe / complete. Therefore, the critical progressive impulse and the critical progressive overpressure are also divided into three types: moderate / severe / complete.

[0023] The blasting conditions are usually described by the overpressure P and the impulse I. Among them, the overpressure P refers to the difference between the pressure on the shock wave front generated by the explosion and the ambient pressure; the impulse I is the integral of the shock wave pressure over time, which represents the total effect of the shock wave on the object. For blast resistance experiments and simulation, the overpressure P and the impulse I can be set by adjusting the amount of explosive, the blasting distance, etc.

[0024] The so-called simulation refers to establishing an engineering target model in blasting simulation software (such as Ansys-dyna, Abauqs, Autodyn), setting the blasting conditions, and performing numerical simulation on the target blasting process, which is a commonly used method in this field.

[0025] The damage pictures can be obtained by photographing the damaged surface of the experimental engineering target, or directly exporting the image of the damaged surface of the engineering target of the simulation model. Figure 4 、 Figure 5 respectively show the damage pictures of the experiment and simulation results of the cross-shaped beam-slab composite structure.

[0026] The blast resistance damage data includes: deflection-span ratio, structural rotation angle, and spalling thickness. The deflection-span ratio, structural rotation angle, and spalling thickness are all commonly used parameters in the blasting field, and can be obtained by simple measurement and calculation of the experimental results. The specific measurement and calculation methods belong to the well-known technology in this field and will not be elaborated here.

[0027] In addition, the damage pictures and the blast resistance damage data can also be obtained from public papers, patents and other materials.

[0028] In this embodiment, the damage levels are divided into four levels: mild damage, moderate damage, severe damage, and complete damage. The specific meanings of the definitions of the damage levels are as follows: ① Mild damage: A small number of cracks or local deformations appear on the surface of the engineering target, but it does not affect the overall bearing capacity and safety of the structure, and it can continue to be used after simple repair; ② Moderate damage: Obvious cracks, deformations or local damages appear on the surface of the engineering target, but the overall structure still has good bearing capacity and safety, and it can be repaired and continue to be used in a short time; ③ Severe damage: Obvious damages appear in some parts of the engineering target, large deformations or a large number of cracks occur, the bearing capacity is lost, and a certain degree of bending damage appears in some parts of the structure, but the structure still has a certain integrity and bearing capacity, and there is a possibility of repair. ④ Complete damage: The structure of the engineering target completely loses its bearing capacity, the overall structure completely fails, it is difficult to continue to be used, and the repair value is completely lost.

[0029] The description of the damage levels is given here. However, when actually judging which level a certain explosion result belongs to, it is not to manually observe which description the engineering target conforms to, but to calculate the anti-explosion damage data (deflection-span ratio, structural rotation angle, and spalling thickness) based on the explosion result, and compare the anti-explosion damage data with the existing damage level comparison table to rigorously obtain the damage level.

[0030] The specific definitions of the damage critical states are the following three: ① The critical state between mild damage and moderate damage is defined as "moderate damage critical"; ② The critical state between moderate damage and severe damage is defined as "severe damage critical"; ③ The critical state between severe damage and complete damage is defined as "complete damage critical". Correspondingly, the damage critical conditions are also divided into moderate damage critical conditions, severe damage critical conditions, and complete damage critical conditions.

[0031] The method of "dividing the damage level of the blasting condition according to the anti-explosion damage data" is a commonly used method in the blasting field. A large number of public materials in this field give the comparison table between the anti-explosion damage data and the damage level of typical engineering targets, or disclose the experimental methods for establishing the comparison table. For example, in "Research on Damage Criteria of Reinforced Concrete Beams under Blast Loads", Acta Armamentarii, Vol. 37 No. 8, Aug. 2016, Table 2 in the article gives the correspondence between the deflection-span ratio and the damage level. By comparing the deflection-span ratio, structural rotation angle, and spalling thickness obtained from this experiment or simulation with the comparison table, the damage level can be obtained. Usually, the larger the deflection-span ratio and the larger the spalling thickness, the more serious the damage degree usually means. For example, Table 1 below shows the damage levels corresponding to different deflection-span ratios of the cross-shaped beam-slab composite structure. The deflection-span ratio of 0 - 7.6% belongs to mild damage, 7.6% - 20.9% belongs to moderate damage, 20.9% - 30.8% is severe damage, and above 30.8% is complete damage.

[0032] Table 1: Deflection-span ratio - failure grade comparison table of cross-shaped beam-slab composite structure

[0033] The specific steps for selecting different blasting conditions are as follows: ① Select a fixed overpressure P0 and different increasing impulses I1, I2... I n , and conduct anti-explosion experiments or simulations with (P0, I1), (P0, I2)... (P0, I n ) as the blasting conditions respectively. Denote the set of these blasting conditions as "fixed overpressure scatter points". ② Select a fixed impulse I0 and different increasing overpressures P1, P 2······ P n , and conduct anti-explosion experiments or simulations with (P1, I0), (P2, I0) ······ (P n , I0) as the blasting conditions respectively. Denote the set of these blasting conditions as "fixed impulse scatter points". ③ Select an extremely high limit overpressure P max and different increasing impulses I1, I 2······ I n , and conduct anti-explosion experiments or simulations with (P max , I1), (P max , I2) ······ (P max , I n ) as the blasting conditions respectively. Denote the set of these blasting conditions as "limit overpressure scatter points". ④ Select an extremely high limit impulse I max and different increasing overpressures P1, P 2······ P n , and conduct anti-explosion experiments or simulations with (P1, I max ), (P2, I max ) ······ (P n , I max ) as the blasting conditions respectively. Denote the set of these blasting conditions as "limit impulse scatter points".

[0034] Figure 6 In the P-I diagram, two types of blasting conditions, namely the fixed overpressure P0 and the fixed impulse I0, obtained through simulation calculations and the corresponding failure grades are shown. Each scatter point represents its blasting condition with the horizontal and vertical coordinates P-I, and represents its failure grade with different color and shape legends. Figure 6 A row of scatter points arranged horizontally in is the fixed overpressure scatter points, which are the simulation results of selecting the fixed overpressure P0 as 0.22 MPa and different impulses I as the blasting conditions. Figure 6A column of scattered points arranged vertically in the middle is the fixed impulse scattered points, which are the simulation results of selecting the fixed impulse I0 of 11 MPa×ms and different overpressures P as the blasting conditions. It can be seen that under the same overpressure, the greater the impulse, the more serious the damage; under the same impulse, the greater the overpressure, the more serious the damage.

[0035] Figure 7 The limit overpressure P obtained through simulation calculations is shown in the P-I diagram. max And the limit impulse I max Two types of blasting conditions and the corresponding damage levels. Figure 7 A row of scattered points arranged horizontally in the upper left corner is the limit overpressure scattered points, which are the simulation results of selecting the limit overpressure P max Of 0.3 MPa and different impulses I as the blasting conditions. Observing the three curves, it can be seen that under this overpressure, the curves of the three different damage critical conditions all tend to be vertical (the abscissa I approaches a fixed value), that is, when the overpressure value is extremely high, the impulse of the damage critical condition approaches a fixed value. Figure 7 A column of scattered points arranged vertically in the lower right corner is the limit impulse scattered points, which are the simulation results of selecting the limit impulse I max Of 60 MPa×ms and different overpressures P as the blasting conditions. It can be seen that when the impulse value is extremely high, the overpressure of the damage critical condition approaches a fixed value.

[0036] S3. For the fixed overpressure scattered points, fixed impulse scattered points, limit overpressure scattered points and limit impulse scattered points, the cyclic interpolation method is respectively used to obtain the damage critical conditions; the impulse of the damage critical condition under the limit overpressure is denoted as the critical progressive impulse I sn ; the overpressure of the damage critical condition under the limit impulse is denoted as the critical progressive overpressure P sn .

[0037] Since the damage critical conditions include "moderate / severe / complete" three types, the "obtaining the damage critical conditions" mentioned above means: performing each of the above three damage critical conditions once.

[0038] The cyclic interpolation method includes the following steps: S1-1. Among the scattered points of the specified type, find two explosion conditions with two different damage levels and each closest to the damage critical, and denote them as blasting condition a and blasting condition b respectively. The scattered points refer to one of the fixed overpressure scattered points, fixed impulse scattered points, limit overpressure scattered points or limit impulse scattered points.

[0039] S1-2. Perform numerical averaging on the P and I of the above two blasting conditions respectively to obtain a new blasting condition, denoted as blasting condition n.

[0040] S1-3. Conduct numerical simulation on the blasting condition n to obtain damage pictures and anti-explosion damage data. Classify the damage level of this blasting condition according to the anti-explosion damage data and plot it on the P-I diagram. The blasting condition n must be located at the midpoint between the blasting condition a and the blasting condition b.

[0041] S1-4. If the damage level of the blasting condition n is the same as that of the blasting condition a, replace the blasting condition a with the blasting condition n, and then re-execute S1-2 to S1-4; if the damage level of the blasting condition n is the same as that of the blasting condition b, replace the blasting condition b with the blasting condition n, and then re-execute S1-2 to S1-4; if the blasting condition n exactly falls on the damage critical condition, end the execution, and the blasting condition n at this time is the damage critical condition.

[0042] For example, for fixed overpressure scatter points: S2-1. Find two explosion conditions with two different damage levels and each closest to the damage critical condition, and denote them as (P0, I a ) and (P0, I b ).

[0043] Taking the search for the moderate damage critical condition as an example, find two adjacent blasting conditions in the P-I diagram, where the blasting condition a (P0, I a ) belongs to mild damage and the blasting condition b (P0, I b ) is moderate damage. Then (P0, I a ) and (P0, I b ) are the two blasting conditions among the fixed overpressure scatter points that are closest to the moderate damage critical condition.

[0044] S2-2. Take the numerical average of the above two blasting conditions to obtain a new blasting condition n (P0, I new ).

[0045] From (P0, I a ), (P0, I b ), since their overpressures are the same, after taking the numerical average, the overpressure value of the blasting condition n is still P0, and the impulse value is I new = (I a + I b ) / 2.

[0046] S2-3. Conduct numerical simulation or experimental research on the blasting condition n (P0, I new ) to obtain damage pictures and anti-explosion damage data. Classify the damage level of this blasting condition according to the anti-explosion damage data and plot it on the P-I diagram.

[0047] S2-4. If the damage level of the blasting condition n (P0, I new ) is the same as that of the blasting condition a (P0, Ia ), if they are the same, replace the blasting condition a with (P0, I new ), and re - execute operations S2 - 2 to S2 - 4; if the damage level of the blasting condition n (P0, I new ) is the same as that of the blasting condition b (P0, I b ), replace the blasting condition b with (P0, I new ), and re - execute operations S2 - 2 to S2 - 4; loop until the newly obtained blasting condition n exactly falls on the damage critical state, and at this time, the blasting condition n is the moderate damage critical condition.

[0048] The search for the severe damage critical condition and the complete damage critical condition is similar to the above steps. Finally, three damage critical conditions under the fixed overpressure P0 are obtained.

[0049] Also perform the cyclic interpolation method on the fixed impulse scatter points, the limit overpressure scatter points, and the limit impulse scatter points to find the three damage critical conditions for each type of scatter point.

[0050] "Interpolation" actually means finding the mid - point between two points. If the newly interpolated point falls in the left region, then perform interpolation on the new point and the original right - hand point; if the new point falls on the right, perform interpolation on the new point and the left - hand point, and repeat until the new point exactly falls on the critical line. For the fixed overpressure scatter points, interpolate and find the mid - point between two points, one above and one below, and loop.

[0051] Table 2 below shows the calculation results of the damage critical conditions for fixed impulse and fixed overpressure. Among them, the values in the first row are the three damage critical conditions for a fixed overpressure of 0.22 MPa. The values in the second row are the three damage critical conditions for a fixed impulse of 11 MPa×ms. The values in the third row are the three damage critical conditions for a limit overpressure of 0.30 MPa; the values in the fourth row are the three damage critical conditions for a limit impulse of 60 MPa×ms. The moderate critical progressive impulse is 1.80 MPa×ms, the severe critical progressive impulse is 2.10 MPa×ms, and the complete critical progressive impulse is 3.00 MPa×ms. The moderate critical progressive overpressure is 0.210 MPa, the severe critical progressive overpressure is 0.215 MPa, and the complete critical progressive overpressure is 0.219 MPa.

[0052] Table 2: Calculation Results of Damage Critical Conditions for Fixed Impulse and Fixed Overpressure

[0053] The above method is based on the method of "selecting the scatter points closest to the critical conditions and performing cyclic interpolation", which can quickly find the scatter points on the critical curves of various failure critical conditions with very few simulation times. After finding at least 2 blast condition scatter points and the critical asymptotic overpressure and critical asymptotic impulse of the curve for each failure critical condition, the curve expression of the failure critical condition can be obtained by the method of curve fitting, thus greatly reducing the experimental or simulation cost.

[0054] S4. Substitute the above failure critical conditions, critical asymptotic overpressure and critical asymptotic impulse into the classical P-I curve expression for fitting to obtain the expression of the failure critical curve. The classical P-I curve expression is:

[0055] where P is the overpressure value, I is the impulse value, P sn is the critical asymptotic overpressure; I sn is the critical asymptotic impulse; α PI is the failure mode factor, which is related to the failure mode of the blast and can be directly determined according to the engineering target category, failure mode, etc. In this embodiment, α PI = 0.8; the parameters A PI and β PI are both constants determined by fitting.

[0056] Specifically, substitute the moderately damaged critical conditions (0.22, 16.50) and (0.23, 11.00) obtained in the previous step, as well as the critical asymptotic overpressure P sn = 0.210 and the critical asymptotic impulse I sn = 1.80 into the classical P-I curve expression for fitting to obtain A PI = 0.8 and β PI = 1.8 for moderately damaged critical. Similarly, perform the above operations on the severely damaged and completely damaged critical conditions respectively, and finally obtain the P-I curve expressions for the three failure critical conditions:

[0057] S5. According to the expression of the failure critical curve, select more failure critical conditions. Simulate the newly selected failure critical conditions to obtain damage pictures and anti-blast damage data; identify the damage pictures of each failure critical condition through a mature image damage feature recognition program and obtain their damage areas; calculate the average value of the damage areas for the same type of failure critical conditions to obtain the failure critical area.

[0058] Taking the medium damage criticality as an example, the specific steps to select more medium damage critical conditions are as follows: Specify an overpressure range and a step size △P. Within this overpressure range, select an overpressure P at every interval of the step size △P. Substitute each overpressure P into the curve expression of the medium damage criticality, and calculate the corresponding overpressure I. This blasting condition (P, I) must be a medium damage critical condition.

[0059] The image damage feature recognition program can adopt existing open-source programs. For example, it can adopt image contour detection based on OpenCV and quickly calculate the damage area according to the image contour. Currently, there are a large number of relevant mature algorithms available for use.

[0060] After simulating different (P, I) values on the damage critical curve, the obtained damage areas will be slightly different due to numerical errors. Therefore, in this step, multiple different damage critical conditions are selected on the damage critical curve, the damage areas are identified and averaged after simulation, and this average value is used as the damage critical area to make the data more accurate and reliable. The damage critical area includes: medium damage critical area, severe damage critical area, and complete damage critical area.

[0061] S6. Establish the damage assessment criterion for the image damage features under this engineering target category.

[0062] The damage assessment criterion for the image damage features is the corresponding relationship between the damage critical area and the damage level. The specific corresponding relationship is as follows: When the damage area is lower than the medium damage critical area, the current damage level is mild damage; when the damage area is between the medium damage critical area and the severe damage critical area, the current damage level is medium damage; when the damage area is between the severe damage critical area and the complete damage critical area, the current damage level is severe damage; when the damage area is higher than the complete damage critical area, the current damage level is complete damage.

[0063] Figure 8 、 Figure 9 respectively show the time history curves of the damage area and the deflection-span ratio of the cross-shaped beam-slab composite structure. Both the damage area and the deflection-span ratio increase with time. Figure 10 is the damage assessment criterion for the image damage features of the cross-shaped beam-slab composite structure. The three horizontal dotted lines in the figure from bottom to top are the medium damage critical area, the severe damage critical area, and the complete damage critical area respectively. As long as the damage area at any time is known, the current damage level can be quickly obtained by comparison.

[0064] As Figure 3 shown, after establishing the damage assessment criterion for the image damage features, the rapid damage assessment method for typical engineering targets based on image recognition technology includes the following steps: S01. Take damaged images of the engineering target after damage.

[0065] It can be done by personnel or advanced methods such as drone photography.

[0066] S02. Input the damage pictures into the image damage feature recognition program to quickly obtain the damaged area.

[0067] S03. Classify the photographed engineering targets according to typical structural components such as beams, slabs, columns, and walls, and determine the corresponding typical engineering target category of the photographed engineering target.

[0068] S04. Compare the extracted damaged area with the damage criterion of the image damage feature corresponding to the typical engineering target category, and the damage level can be determined to achieve rapid damage assessment.

Claims

1. A method for rapid damage assessment of typical engineering targets based on image recognition technology, characterized in that It includes the following steps: Establish corresponding damage assessment criteria for image damage characteristics according to typical engineering target categories. The specific method is as follows: Obtain damage pictures and anti-explosion damage data of engineering targets, conduct damage level division and draw P-I curves, and define different damage levels and damage critical states according to the explosion damage degree and characteristics; For fixed overpressure scatter points, fixed impulse scatter points, limit overpressure scatter points, and limit impulse scatter points, respectively use the cyclic interpolation method to obtain the damage critical conditions, critical progressive impulse, and critical progressive overpressure, and substitute them into the classical P-I curve expression for fitting to obtain the expression of the damage critical curve; According to the expression of the damage critical curve, simulate the new damage critical conditions to obtain damage pictures and anti-explosion damage data, and identify the damage area of the damage pictures of each new damage critical condition through the image damage characteristic recognition program. Calculate the average value of the damage areas of the same type of damage critical conditions to obtain the damage critical area; Establish the damage assessment criteria for image damage characteristics under this engineering target category, and the damage assessment criteria for image damage characteristics are the corresponding relationship between the damage critical area and the damage level. Take pictures of the damage pictures of the engineering target after damage. Input the damage pictures into the image damage characteristic extraction program to extract the damage area. Determine the damage assessment criteria for image damage characteristics corresponding to the photographed engineering target according to the typical engineering target category. Compare the extracted damage area with the corresponding damage assessment criteria for image damage characteristics to quickly determine the damage level of the photographed engineering target.

2. The rapid damage assessment method for typical engineering targets based on image recognition technology according to claim 1, characterized in that The cyclic interpolation method includes the following steps: S1-1: Find two explosion conditions with different damage levels and each closest to the damage critical, and record them as blasting condition a and blasting condition b respectively. S1-2: Numerically average the overpressure P and impulse I of blasting condition a and blasting condition b to obtain a new blasting condition, denoted as blasting condition n. S1-3: Conduct numerical simulation or experimental research on blasting condition n to obtain damage pictures and anti-explosion damage data, and divide the damage level of this blasting condition n according to the anti-explosion damage data and plot it on the P-I curve. S1-4: If the damage level of blasting condition n is the same as that of blasting condition a, then replace blasting condition a with blasting condition n, and then re-execute S1-2 to S1-4; If the damage level of blasting condition n is the same as that of blasting condition b, then replace blasting condition b with blasting condition n, and then re-execute S1-2 to S1-4; If blasting condition n falls on the damage critical condition, then the current blasting condition n is the damage critical condition.

3. The rapid damage assessment method for typical engineering targets based on image recognition technology according to claim 2, characterized in that The blasting conditions include: Select a fixed overpressure and different impulses increasing in sequence as the blasting condition; Select a fixed impulse and different overpressures increasing in sequence as the blasting condition; Select a limit overpressure and different impulses increasing in sequence as the blasting condition; Select a limit impulse and different overpressures increasing in sequence as the blasting condition.

4. The rapid damage assessment method for typical engineering targets based on image recognition technology according to claim 1, characterized in that, The anti-explosion damage data includes: deflection-span ratio, structural rotation angle, and spalling thickness.

5. The rapid damage assessment method for typical engineering targets based on image recognition technology according to claim 1, characterized in that, The damage levels are divided into slight damage, moderate damage, severe damage, and complete damage.

6. The rapid damage assessment method for typical engineering targets based on image recognition technology according to claim 5, characterized in that The damage critical state includes the moderate damage critical state, the severe damage critical state, and the complete damage critical state. The critical state between mild damage and moderate damage is defined as the moderate damage critical state, the critical state between moderate damage and severe damage is defined as the severe damage critical state, and the critical state between severe damage and complete damage is defined as the complete damage critical state.

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