Intelligent concrete stress damage detection method using 3D printing technology

Abstract

The application provides a kind of intelligent concrete stress damage detection method using 3D printing technology, and specifically relates to the technical field of building structure stress damage detection.The method specifically includes: preparing a high-resistivity intelligent concrete substrate; using 3D printing to print low-resistivity intelligent concrete straight strips, point electrodes, ring-shaped strips on the intelligent concrete substrate and connect copper wires; preparing an intelligent concrete detection device and calibrating initial parameters and sensitivity values; preparing a concrete component to be tested containing the intelligent concrete detection device and obtaining the actual strain size received in three dimensions; then by applying external force to the concrete component to be tested, analyzing the damage state of the intelligent concrete substrate and the volumetric deformation of the ring-shaped strip, and then obtaining the overall stress damage of the concrete component to be tested. The application utilizes the spatial characteristics of 3D printing technology and the high sensitivity of intelligent concrete material to simultaneously achieve precise monitoring of structural damage, strain stress and volumetric deformation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building structure stress damage detection, and specifically relates to an intelligent concrete stress damage detection method using 3D printing technology. BACKGROUND

[0002] With the development of the construction industry and science and technology, more and more huge, complex structure, and multi-functional concrete structures have emerged, such as super-large-span bridges, large-scale water conservancy projects, offshore platform structures, nuclear power plant buildings, and the like. These structures are often important, long in service life, complex in load and stress, and the cost is huge once they fail. Therefore, in order to ensure the safety of these structures, effective means for testing and structural health monitoring are often needed to accurately grasp the internal stress, deformation and damage distribution characteristics of the key parts of these complex structures, especially the multi-dimensional strain characteristics, which has become an important research focus in the field of building structures.

[0003] The so-called intelligent concrete is a kind of pressure-resistance sensor composed of conductive particles mixed in concrete, which can not only monitor the strain of concrete, but also monitor its damage. According to the corresponding relationship between the resistance change rate of such intelligent materials and the strain, it can be used for the detection of concrete strain and damage; however, the detection effect is often affected by the uniformity of intelligent concrete, multi-axial stress state, stability, etc., therefore, the intelligent concrete material prepared by the conventional pouring method has problems such as insufficient precision and unstable intelligent characteristics. 3D printing is a kind of rapid prototyping technology, which has the advantages of high precision, low cost, good repeatability, etc., and has become a new promising process means in the field of electronic product preparation. It is based on digital model files and constructs three-dimensional physical objects by layer-by-layer extrusion of concrete materials with certain flowability and plasticity.

[0004] Therefore, in order to solve the above problems, the present application provides an intelligent concrete stress damage detection method using 3D printing technology. SUMMARY

[0005] In order to overcome the shortcomings of the prior art and solve the problems of insufficient uniformity, precision and unstable intelligent characteristics of the intelligent concrete material prepared by the conventional pouring method, which further affects the detection results, the present application provides an intelligent concrete stress damage detection method using 3D printing technology, and the specific technical solutions are as follows:

[0006] An intelligent concrete stress damage detection method using 3D printing technology, specifically comprising the following steps:

[0007] S1. Pouring two intelligent concrete substrates with high resistivity;

[0008] S2. Using a 3D printer, print low-resistivity straight-line strips of smart concrete on one side of the top of one piece of smart concrete substrate along the X, Y, and Z directions, respectively; print two low-resistivity point electrodes and a low-resistivity ring-shaped strip of smart concrete on the top and bottom of another piece of smart concrete substrate, respectively;

[0009] S3. Before the smart concrete straight-line strips, point electrodes, and ring-shaped strip in S2 solidify, insert copper wires and make marks, respectively;

[0010] S4. Stack the two pieces of smart concrete substrate in S3, and place the one side of the smart concrete straight-line strips opposite the one side of the smart concrete ring-shaped strip;

[0011] S5. Pour a common concrete encapsulation layer on one side of the smart concrete straight-line strips and one side of the smart concrete ring-shaped strip, respectively, and obtain a smart concrete detection device after solidification; keep the lead ends of the copper wires exposed on the surface of the smart concrete detection device;

[0012] S6. Apply an external force to the smart concrete detection device, measure the resistivity variation of the copper wires between the three smart concrete straight-line strips under different external forces, respectively, calibrate the initial parameters of the relationship between the resistance of the smart concrete straight-line strips and the external force, and measure the initial resistivity values of the smart concrete point electrodes and the smart concrete ring-shaped strip, and obtain the sensitivity value of the smart concrete detection device;

[0013] S7. Pour the concrete member to be detected, and place the smart concrete detection device obtained in S5 in the concrete member to be detected, and keep the lead ends of the copper wires exposed on the surface of the concrete member to be detected;

[0014] S8. Calculate the actual stress size of the whole concrete member to be detected in the X, Y, and Z directions by using the initial parameters and sensitivity values of the smart concrete straight-line strips;

[0015] By applying external forces of different directions and sizes to the concrete member to be detected, measure the resistivity variation of the smart concrete point electrodes under different external forces, analyze the damage state of the smart concrete substrate, and further obtain the damage state of the whole concrete member to be detected;

[0016] By applying external forces of different directions and sizes to the concrete member to be detected, measure the resistivity variation of the smart concrete ring-shaped strip under different external forces, analyze the volume deformation of the area inside the smart concrete ring-shaped strip, and further obtain the volume deformation of the whole concrete member to be detected;

[0017] S9. Collect measurement parameters and data according to the measurement results obtained in S8, and timely make early warnings and take structural maintenance measures.

[0018] Preferably, the high resistivity ranges from >10000 Ω·m; the low resistivity ranges from ≤10000 Ω·m.

[0019] Preferably, the material ratio of the smart concrete base in S1 is cement: sand: water: graphene: superplasticizer = 1-1.5: 2.5-3: 0.4-0.6: 0.0025-0.01: 0.0025-0.01; the material ratio of the smart concrete straight strip, the smart concrete point electrode and the smart concrete ring-shaped strip in S2 is cement: sand: water: graphene: superplasticizer = 1-1.5: 2.5-3: 0.4-0.6: 0.03-0.08: 0.03-0.08.

[0020] Preferably, the specific insertion position of the copper wire in S3 is as follows:

[0021] Take six copper wires, insert one copper wire at each end of each smart concrete straight strip, and lead out the other end of the copper wire; regard the two copper wires on each smart concrete straight strip as a group, and number the three groups of copper wires as A, B and C respectively;

[0022] Take another two copper wires, insert one copper wire on each smart concrete point electrode, and lead out the other end of the copper wire; regard the copper wires on the two smart concrete point electrodes as a group, and number it as D;

[0023] Take another two copper wires, take two points at the position where the diameter intersects the arc on the smart concrete ring-shaped strip, insert one copper wire on each point, and lead out the other end of the copper wire; regard the two copper wires on the smart concrete ring-shaped strip as a group, and number it as E.

[0024] Preferably, the measurement method of the resistivity variation law between the copper wires on the smart concrete straight strip in S6 is as follows:

[0025] Apply different directions and different sizes of external force to the smart concrete detector by the press machine, measure the resistance values between the paired copper wires in groups A, B and C corresponding to different external forces respectively, obtain the variation law of the resistivity of the smart concrete straight strip with the change of external force in three directions, and then calculate the initial parameter values of the relationship between the resistance of each smart concrete straight strip and the external force it bears.

[0026] Further preferably, the specific conversion method of the actual stress size of the whole to-be-detected concrete member in X, Y and Z directions in S8 is as follows:

[0027] According to the relationship between resistance and stress size:

[0028] S = aR + b;

[0029] Wherein, R is the resistance value of the concrete component to be detected, a, b are the initial parameter values obtained in S6, S is the stress;

[0030] Combined with the sensitivity value obtained in S6, the specific value of the actual stress received by the concrete component to be detected along the X, Y and Z directions can be converted.

[0031] It is also preferred that the resistivity variation law measurement method between the copper wires of the intelligent concrete point electrode in S8 is as follows:

[0032] Different directions and different sizes of external force are applied to the concrete component to be detected in S7 by a press machine, the resistance value between the paired copper wires in number D corresponding to different external forces is measured, and then the variation law of the resistivity of the intelligent concrete point electrode with the change of external force is obtained.

[0033] It is further preferred that the damage state of the whole concrete component to be detected in S8 is divided into the following three cases:

[0034] If the variation range between the resistivity of the two copper wires on the intelligent concrete point electrode and the initial value of the resistivity of the intelligent concrete point electrode obtained in S6 is within ±0.1%, it indicates that the intelligent concrete substrate is undamaged, i.e. the concrete component to be detected is in the undamaged stage;

[0035] If the variation range between the resistivity of the two copper wires on the intelligent concrete point electrode and the initial value of the resistivity of the intelligent concrete point electrode obtained in S6 is greater than 0.1% and less than or equal to 5%, it indicates that the intelligent concrete substrate appears slight damage, i.e. the concrete component to be detected is in the damage stage;

[0036] If the variation range between the resistivity of the two copper wires on the intelligent concrete point electrode and the initial value of the resistivity of the intelligent concrete point electrode obtained in S6 is greater than 5%, it indicates that the intelligent concrete substrate appears serious damage or even cracks, i.e. the concrete component to be detected is in the destruction stage.

[0037] It is still further preferred that the resistivity variation law measurement method between the copper wires on the intelligent concrete ring-shaped strip in S8 is as follows:

[0038] Different directions and different sizes of external force are applied to the concrete component to be detected in S7 by a press machine, the resistance value between the paired copper wires in number E corresponding to different external forces is measured, and then the variation law of the resistivity of the intelligent concrete ring-shaped strip with the change of external force is obtained.

[0039] It is still further preferred that the volume deformation state of the whole concrete component to be detected in S8 is divided into the following three cases:

[0040] Case one: if the resistivity between the two copper wires on the smart concrete ring-shaped strip gradually decreases with the change of external force, then it indicates that the volume of the region inside the smart concrete ring-shaped strip shrinks, and further indicates that the volume of the concrete member to be detected shrinks;

[0041] Case two: if the resistivity between the two copper wires on the smart concrete ring-shaped strip gradually increases with the change of external force, then it indicates that the volume of the region inside the smart concrete ring-shaped strip expands, and further indicates that the volume of the concrete member to be detected expands;

[0042] Case three: if the change range between the resistivity between the two copper wires on the smart concrete ring-shaped strip and the initial value of the resistivity of the smart concrete ring-shaped strip obtained in S6 is greater than 5%, then it indicates that cracks appear in the region inside the smart concrete ring-shaped strip, and further indicates that the volume of the concrete member to be detected further expands compared to the state in case two.

[0043] The beneficial effects of the present application are:

[0044] The present application intends to use high-resistivity smart concrete as the base body, combine the low-resistivity smart concrete structure with the high-resistivity smart concrete base body through 3D printing technology, compared with the traditional pouring type detection test piece, the present application can obtain X, Y, Z multi-dimensional structure detection of the test piece by using the spatial characteristics of the 3D printing technology; in addition, the present application uses smart concrete material, which has higher measurement sensitivity and accuracy than ordinary concrete material, and can simultaneously realize comprehensive monitoring of the damage, strain stress and volume deformation of the structure; and provides effective basis for improving the safety of civil engineering facilities, reasonably guiding the maintenance scheme of the structure health and prolonging the service life of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0045] The drawings constituting the specification of the present application are used to provide further understanding of the present application and do not constitute undue limitation on the present application.

[0046] Figure 1 It is a schematic diagram for the preparation of the smart concrete base in the present application;

[0047] Figure 2 It is a schematic diagram of the smart concrete base in the present application in the concrete member to be detected;

[0048] Figure 3 It is the change rule of the resistivity between the smart concrete point electrodes with the stress state;

[0049] Figure 4 It is the change rule of the resistivity of the smart concrete straight strip in the X direction with the stress state;

[0050] Figure 5 It is the change rule of the resistivity of the smart concrete straight strip in the Y direction with the stress state;

[0051] Figure 6 The resistivity of the straight strip of intelligent concrete in the Z direction varies with the stress state.

[0052] Figure 7 The resistivity of intelligent concrete ring strips varies with stress state.

[0053] In the diagram, 1-3D printer; 11-extrusion nozzle; 2-smart concrete substrate; 21-smart concrete straight strip; 22-smart concrete point electrode; 23-smart concrete ring strip; 3-encapsulation layer; 4-concrete component to be inspected. Detailed Implementation

[0054] The specific implementation of the intelligent concrete stress damage detection method using 3D printing technology provided by the present invention will be further described in conjunction with the accompanying drawings and embodiments.

[0055] like Figures 1-2 As shown, a smart concrete stress damage detection method utilizing 3D printing technology specifically includes the following steps:

[0056] S1. Pour two high-resistivity smart concrete substrates; wherein, the high-resistivity smart concrete has intelligent features for coarse damage condition detection.

[0057] S2. Using a 3D printer, low-resistivity smart concrete straight strips are printed on the top of one smart concrete substrate along the X, Y, and Z directions respectively; two low-resistivity smart concrete point electrodes and a smart concrete annular strip are printed on the top and bottom of another smart concrete substrate respectively; the low-resistivity smart concrete has high sensitivity and more accurate stress and resistivity variation law, and is used for strain detection.

[0058] The high resistivity ranges from >100000 Ω·m, and the low resistivity ranges from ≤10000 Ω·m.

[0059] Preferably, the material ratio of the smart concrete substrate in S1 is cement:sand:water:graphene:superplasticizer = 1~1.5:2.5~3:0.4~0.6:0.0025~0.01:0.0025~0.01;

[0060] Preferably, the material ratio of the intelligent concrete linear strip, intelligent concrete point electrode, and intelligent concrete annular strip in S2 is cement: sand: water: graphene: superplasticizer = 1~1.5: 2.5~3: 0.4~0.6: 0.03~0.08: 0.03~0.08.

[0061] S3. In S2, the copper wires are inserted into the smart concrete linear strips, the smart concrete point electrodes and the smart concrete ring-shaped strips respectively before they are solidified, and are marked;

[0062] Preferably, the specific insertion positions of the copper wires in S3 are as follows:

[0063] Take six copper wires, insert one copper wire into each end of each smart concrete linear strip, and lead the other end of the copper wire out; regard the two copper wires on each smart concrete linear strip as a group, and number three groups of copper wires as A, B and C respectively;

[0064] Take another two copper wires, insert one copper wire into each of the smart concrete point electrodes respectively, and lead the other end of the copper wire out; regard the copper wires on the two smart concrete point electrodes as a group, and number them as D;

[0065] Take another two copper wires, take two points at the positions where the diameter and the circular arc intersect on the smart concrete ring-shaped strip, insert one copper wire into each point respectively, and lead the other end of the copper wire out; regard the two copper wires on the smart concrete ring-shaped strip as a group, and number them as E.

[0066] S4. Stack the two smart concrete substrates in S3, and set the one side of the smart concrete linear strips opposite to the one side of the smart concrete ring-shaped strips;

[0067] S5. Pour the ordinary concrete packaging layer on the one side of the smart concrete linear strips and the one side of the smart concrete ring-shaped strips respectively, and obtain the smart concrete detection device after solidification; keep the leading ends of the copper wires exposed on the surface of the smart concrete detection device;

[0068] S6. Apply external force to the smart concrete detection device, measure the resistivity variation law between the copper wires on the smart concrete linear strips under different external forces, and calibrate the initial parameters of the relationship between the resistance of the smart concrete linear strips and the external force; measure and calculate the initial values of the resistivity of the smart concrete point electrodes and the smart concrete ring-shaped strips, and obtain the sensitivity value of the smart concrete detection device at the same time;

[0069] S7. Pour the concrete member to be detected, and place the smart concrete detection device obtained in S5 in the concrete member to be detected, and keep the leading ends of the copper wires exposed on the surface of the concrete member to be detected;

[0070] S8. First, calculate the actual stress size of the whole concrete member to be detected in X, Y and Z directions by the initial parameters and the sensitivity value of the smart concrete linear strips, and the specific method is as follows:

[0071] According to the relationship between the resistance and the stress size:

[0072] S = aR + b;

[0073] Wherein, R is the resistance value of the concrete member to be detected (known measurable), a, b is the initial parameter value obtained in S6 (known);

[0074] Combined with the sensitivity value obtained in S6, the specific value of the actual stress S received by the concrete member to be detected along the X, Y and Z directions can be calculated.

[0075] Secondly, the concrete member to be detected in S7 is subjected to different directions and different sizes of external force by the press machine, and the resistance values between the paired copper wires in the number D corresponding to different external forces are measured, and the change rule of the point electrode resistivity of the smart concrete with the change of the external force is obtained;

[0076] Further, the damage state of the whole concrete member to be detected is divided into the following three cases:

[0077] Case 1: If the change range between the resistivity of the two copper wires on the smart concrete point electrode and the initial value of the smart concrete point electrode resistivity obtained in S6 is within ±0.1%, it indicates that the smart concrete substrate is undamaged, that is, the concrete member to be detected is in the undamaged stage;

[0078] Case 2: If the change range between the resistivity of the two copper wires on the smart concrete point electrode and the initial value of the smart concrete point electrode resistivity obtained in S6 is greater than 0.1% and less than or equal to 5%, it indicates that the smart concrete substrate appears small damage, that is, the concrete member to be detected is in the damage stage;

[0079] Case 3: If the change range between the resistivity of the two copper wires on the smart concrete point electrode and the initial value of the smart concrete point electrode resistivity obtained in S6 is greater than 5%, it indicates that the smart concrete substrate appears serious damage or even cracks, that is, the concrete member to be detected is in the destruction stage.

[0080] Finally, the concrete member to be detected in S7 is subjected to different directions and different sizes of external force by the press machine, and the resistance values between the paired copper wires in the number E corresponding to different external forces are measured, and the change rule of the ring-shaped strip resistivity of the smart concrete with the change of the external force is obtained;

[0081] Further, the volume deformation state of the whole concrete member to be detected is divided into the following three cases:

[0082] Case 1: If the resistivity between the two copper wires on the smart concrete ring-shaped strip gradually decreases with the change of the external force, it indicates that the volume of the inner region of the smart concrete ring-shaped strip shrinks, and further indicates that the volume of the concrete member to be detected shrinks;

[0083] Case two: if the resistivity between the two copper wires on the smart concrete ring-shaped strip gradually increases with the change of external force, it indicates that the volume of the area inside the smart concrete ring-shaped strip expands, and further indicates that the volume of the concrete member under test expands;

[0084] Case three: if the change range between the resistivity between the two copper wires on the smart concrete ring-shaped strip and the initial value of the resistivity of the smart concrete ring-shaped strip obtained in S6 is greater than 5%, it indicates that cracks appear in the area inside the smart concrete ring-shaped strip, and further indicates that the volume of the concrete member under test further expands compared to the state in case two.

[0085] S9. Collect measurement parameters and data according to the measurement results obtained in S8, and make timely early warning and take structure maintenance measures.

[0086] Embodiment 1:

[0087] The high-resistivity smart concrete ratio used in this embodiment is cement: sand: water: graphene: superplasticizer = 1:3:0.5:0.005:0.005; the low-resistivity smart concrete ratio is cement: sand: water: graphene: superplasticizer = 1:3:0.5:0.04:0.04;

[0088] Prepare the concrete member under test containing the smart concrete detection device according to the above steps S1-S7, and obtain the initial parameter value of the relationship between the resistance of the smart concrete linear strip and the external force, the initial value of the resistivity of the smart concrete point electrode and the smart concrete ring-shaped strip, and the sensitivity value of the smart concrete detection device;

[0089] Then apply an external force in the vertical direction to the concrete member under test, and cooperate with the temperature compensation principle to obtain the following conclusions respectively:

[0090] As shown in Figure 3 , the resistivity between the copper wires of the smart concrete point electrode changes obviously with the increase of the external force, but there is no linear characteristic between them:

[0091] (1) When the resistivity changes non-significantly with the change of external force, that is, the change range between the resistivity between the two copper wires on the smart concrete point electrode and the initial value of the resistivity of the smart concrete point electrode is within ±0.1%, it indicates that the smart concrete substrate is in the undamaged stage;

[0092] (2) When the resistivity changes with the change of external force, that is, the change range between the resistivity between the two copper wires on the smart concrete point electrode and the initial value of the resistivity of the smart concrete point electrode is greater than 0.1% and less than or equal to 5%, it indicates that the smart concrete substrate is in the damaged stage;

[0093] (3) When the resistivity increases suddenly and greatly, i.e. the change range between the resistivity between the two copper wires on the smart concrete point electrode and the initial value of the resistivity of the smart concrete point electrode is greater than 5%, it indicates that the smart concrete substrate has a serious damage or even a crack, and at this time, it is in the damage stage.

[0094] As shown in S6, the change of the resistivity between the straight strip copper wires of the smart concrete and the external force size approximately presents a linear relationship, and they present an inverse proportional variation relationship; the actual stress value of the concrete member to be detected in the X, Y and Z directions can be calculated according to the initial parameters obtained in S6. Figures 4-6 As shown in S6, the change of the resistivity between the straight strip copper wires of the smart concrete and the external force size approximately presents a linear relationship, and they present an inverse proportional variation relationship; the actual stress value of the concrete member to be detected in the X, Y and Z directions can be calculated according to the initial parameters obtained in S6.

[0095] Figure 7 As shown in S6, the change of the resistivity between the straight strip copper wires of the smart concrete and the external force size approximately presents a linear relationship, and they present an inverse proportional variation relationship; the actual stress value of the concrete member to be detected in the X, Y and Z directions can be calculated according to the initial parameters obtained in S6.

[0096] The first stage is the linear change stage, in which the concrete is in an elastic state, the resistivity decreases with the increase of the external force, i.e. the volume of the concrete member to be detected is shrunk in the initial compression stage;

[0097] The second stage is the development stage of small damage, in which the concrete is in a plastic state, the change of the resistivity with the external force presents a nonlinear relationship, and in this stage, the concrete member to be detected begins to expand;

[0098] The third stage is the rapid development stage of damage, in which the resistivity increases sharply, and in this stage, the concrete member to be detected further expands compared with the second stage.

[0099] When the resistivity between the two copper wires on the smart concrete ring-shaped strip gradually decreases with the change of the external force, it indicates that the volume of the inner region of the smart concrete ring-shaped strip is shrunk; when the concrete member to be detected is slowly stressed or in a complex stress state, the resistivity between the two copper wires on the smart concrete ring-shaped strip also slowly increases with the change of the external force, which indicates that the volume of the inner region of the smart concrete ring-shaped strip begins to expand; when the resistivity between the two copper wires on the smart concrete ring-shaped strip increases greatly, it indicates that the inner region of the smart concrete ring-shaped strip has a crack, and the structure further expands.

[0100] ​In actual engineering application, only the intelligent concrete detection device is prepared in the laboratory, and the initial parameters of the relationship between the linear strip resistance of the intelligent concrete and the external force, the initial value of the resistivity of the intelligent concrete point electrode and the ring-shaped strip of the intelligent concrete, and the sensitivity value of the intelligent concrete detection device are measured; then the intelligent concrete detection device is placed in the detection area of the concrete building to be measured, by referring to the initial value of the resistivity, the change rule of the resistivity with time is observed, so that the structure damage, strain stress and volume deformation of the current detection point of the concrete building to be measured can be accurately judged, and then a warning can be accurately made and timely structure maintenance measures can be taken, so as to avoid causing irreparable major losses and reducing safety hazards.

[0101] The application has the advantages of simple structure, convenient operation and low cost, can realize the detection of health parameters such as internal damage evolution, multi-dimensional strain distribution and volume deformation of the concrete structure, and the research results can be used in structural test research and structural health monitoring, which has important significance for improving the safety of civil engineering facilities, reasonably guiding structural health maintenance and prolonging the service life.

[0102] In the application, the terms such as "upper", "lower", "bottom", "top" and the like indicate the orientation or positional relationship shown in the drawings, which is only a relationship word determined for the purpose of describing the structural relationship of components or elements of the application, and cannot be understood as a limitation of the application. The terms such as "connected", "connected" should be understood in a broad sense, which means that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. For related researchers or technicians in the field, the specific meaning of the above terms in the application can be determined according to the specific circumstances, and cannot be understood as a limitation of the application.

[0103] Of course, the above description is not a limitation of the application, and the application is not limited to the above examples. Changes, modifications, additions or replacements made by those skilled in the art within the essential scope of the application should also be within the protection scope of the application.

Claims

1. A method for detecting damage of intelligent concrete under stress by using 3D printing technology, characterized in that, Specifically comprising the following steps: S1. Pouring two high-resistivity intelligent concrete substrates; S2. Using a 3D printer to print low-resistivity intelligent concrete straight-line strips in X, Y and Z directions on the top of one of the intelligent concrete substrates, and printing two low-resistivity intelligent concrete point electrodes and an intelligent concrete ring-shaped strip on the top and bottom of the other intelligent concrete substrate; S3. Before the intelligent concrete straight-line strips, intelligent concrete point electrodes and intelligent concrete ring-shaped strip in S2 solidify, respectively inserting copper wires and making marks; S4. Stacking the two intelligent concrete substrates in S3, and setting the side of the intelligent concrete straight-line strips opposite to the side of the intelligent concrete ring-shaped strip; S5. Pouring ordinary concrete encapsulation layers on the side of the intelligent concrete straight-line strips and the side of the intelligent concrete ring-shaped strip respectively, and obtaining an intelligent concrete detection device after solidification, keeping the leading ends of the copper wires exposed on the surface of the intelligent concrete detection device; S6. Applying external force to the intelligent concrete detection device, respectively measuring the resistivity change rules of the copper wires between the three intelligent concrete straight-line strips under different external forces, and calibrating the initial parameters of the relationship between the resistance of the intelligent concrete straight-line strips and the external force; measuring the initial values of the resistivity of the intelligent concrete point electrodes and the intelligent concrete ring-shaped strip, and obtaining the sensitivity value of the intelligent concrete detection device; S7. Pouring the concrete member to be detected, and placing the intelligent concrete detection device obtained in S5 in the concrete member to be detected, keeping the leading ends of the copper wires exposed on the surface of the concrete member to be detected; S8. Calculating the actual stress size of the whole concrete member to be detected in X, Y and Z directions through the initial parameters and sensitivity value of the intelligent concrete straight-line strips; By applying external forces of different directions and sizes to the concrete member to be detected, measuring the resistivity change rules of the intelligent concrete point electrodes under different external forces, analyzing the damage state of the intelligent concrete substrate, and further obtaining the damage state of the whole concrete member to be detected; By applying external forces of different directions and sizes to the concrete member to be detected, measuring the resistivity change rules of the intelligent concrete ring-shaped strip under different external forces, analyzing the volume deformation of the area inside the intelligent concrete ring-shaped strip, and further obtaining the volume deformation of the whole concrete member to be detected; S9. Collecting measurement parameters and data according to the measurement results obtained in S8, and timely making early warning and taking structure maintenance measures. 2.The method of claim 1, wherein, The high-resistivity value range is >10000Ω·m; and the low-resistivity value range is ≤10000Ω·m. 3.The method of claim 1, wherein, The material ratio of the intelligent concrete substrate in S1 is cement: sand: water: graphene: superplasticizer = 1-1.5: 2.5-3: 0.4-0.6: 0.0025-0.01: 0.0025-0.01; The material ratio of the intelligent concrete straight-line strips, intelligent concrete point electrodes and intelligent concrete ring-shaped strip in S2 is cement: sand: water: graphene: superplasticizer = 1-1.5: 2.5-3: 0.4-0.6: 0.03-0.08: 0.03-0.

08. 4.The method for detecting damage of smart concrete under stress using 3D printing technology according to claim 1, characterized in that, The specific insertion position of the copper conductor in S3 is as follows: Take six copper conductors, insert one copper conductor at each end of each intelligent concrete straight strip, and lead out the other end of the copper conductor; regard the two copper conductors on each intelligent concrete straight strip as a group, and number the three groups of copper conductors as A, B and C respectively; Take two more copper conductors, insert one copper conductor on each of the two intelligent concrete point electrodes respectively, and lead out the other end of the copper conductor; regard the two copper conductors on the two intelligent concrete point electrodes as a group, and number it as D; Take two more copper conductors, take two points at any diameter and circular arc intersection position on the intelligent concrete ring-shaped strip, insert one copper conductor on each point respectively, and lead out the other end of the copper conductor; regard the two copper conductors on the intelligent concrete ring-shaped strip as a group, and number it as E. 5.The method for detecting stress damage of smart concrete using 3D printing technology according to claim 4, characterized in that, The measurement method of the resistivity change rule between the copper conductors on the intelligent concrete straight strip in S6 is as follows: By applying different directions and different sizes of external force to the intelligent concrete detector device through the press, the resistance values between the paired copper conductors in groups A, B and C corresponding to different external forces are measured respectively, and the change rule of the intelligent concrete straight strip resistivity with the change of external force in three directions is obtained, and then the initial parameter value of the relationship between the resistance of each intelligent concrete straight strip and the external force it bears is calculated. 6.The method for detecting stress damage of smart concrete using 3D printing technology according to claim 5, characterized in that, The specific conversion method of the actual stress size of the whole to-be-detected concrete member in X, Y and Z directions in S8 is as follows: According to the relationship between resistance and stress size: S=aR+b; Wherein, R is the resistance value of the to-be-detected concrete member, a and b are the initial parameter values obtained in S6, and S is the stress; Combined with the sensitivity value obtained in S6, the specific numerical value of the actual stress of the to-be-detected concrete member along X, Y and Z directions can be calculated. 7.The method of claim 4, wherein, The measurement method of the resistivity change rule between the copper conductors on the intelligent concrete point electrode in S8 is as follows: By applying different directions and different sizes of external force to the to-be-detected concrete member in S7 through the press, the resistance values between the paired copper conductors in group D corresponding to different external forces are measured, and then the change rule of the intelligent concrete point electrode resistivity with the change of external force is obtained. 8.The method of claim 7, wherein the method further comprises: determining a stress distribution of the smart concrete based on the stress distribution of the 3D printed object. The damage state of the whole to-be-detected concrete member in S8 is divided into the following three cases: If the change range between the resistivity between the two copper conductors on the intelligent concrete point electrode and the initial value of the intelligent concrete point electrode resistivity obtained in S6 is within ±0.1%, it indicates that the intelligent concrete substrate is undamaged, i.e. the to-be-detected concrete member is in the undamaged stage; If the change range between the resistivity between the two copper conductors on the intelligent concrete point electrode and the initial value of the intelligent concrete point electrode resistivity obtained in S6 is greater than 0.1% and less than or equal to 5%, it indicates that the intelligent concrete substrate appears small damage, i.e. the to-be-detected concrete member is in the damage stage; If the change range between the resistivity between the two copper conductors on the intelligent concrete point electrode and the initial value of the intelligent concrete point electrode resistivity obtained in S6 is greater than 5%, it indicates that the intelligent concrete substrate appears serious damage or even cracks, i.e. the to-be-detected concrete member is in the destruction stage. 9.The method of claim 4, wherein, The resistivity change rule measuring method between the copper conductors on the intelligent concrete annular strip in S8 is as follows: By applying different directions and different sizes of external force to the concrete component to be detected in S7 through the press, the resistance values between the paired copper conductors in E corresponding to different external forces are measured, and then the change rule of the resistivity of the intelligent concrete annular strip with the change of the external force is obtained. 10.The method of claim 9, wherein the method further comprises: determining a stress distribution of the smart concrete based on the stress distribution of the 3D printed object. The volume deformation state of the whole concrete component to be detected in S8 is divided into the following three cases: Case one: if the resistivity between the two copper conductors on the intelligent concrete annular strip gradually decreases with the change of the external force, it indicates that the volume of the region inside the intelligent concrete annular strip shrinks, and then it indicates that the volume of the concrete component to be detected shrinks; Case two: if the resistivity between the two copper conductors on the intelligent concrete annular strip gradually increases with the change of the external force, it indicates that the volume of the region inside the intelligent concrete annular strip expands, and then it indicates that the volume of the concrete component to be detected expands; Case three: if the change range between the resistivity between the two copper conductors on the intelligent concrete annular strip and the initial resistivity of the intelligent concrete annular strip obtained in S6 is greater than 5%, it indicates that cracks appear in the region inside the intelligent concrete annular strip, and then it indicates that the volume of the concrete component to be detected further expands compared with the state in case two.

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