Printing structure design and parameter optimization method based on process defect tolerance coefficient

Abstract

The invention relates to the field of cement-based 3D printing structures, in particular to a process defect tolerance coefficient-based printing structure design and parameter optimization method, which comprises the following steps of: S1, acquiring initial parameters of a printing structure, and determining printing parameters in a printing process according to the initial parameters of the printing structure, the printing parameters comprise printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters and maintenance parameters; s2, calculating a process defect tolerance coefficient according to the printing parameters; and S3, structure type evaluation is conducted on the printing structure according to the process defect tolerance coefficient, whether the printing structure is qualified or not is judged, if yes, a printing scheme of the printing structure is obtained, and if not, initial parameters of the printing structure are adjusted, S1-S3 are repeated, and a qualified printing scheme is obtained through design. According to the method, quantitative evaluation of the additive manufacturing printing structure is achieved, the design and parameter optimization method for the 3D printing concrete structure is constructed, the verification difficulty of the reliability of the printing structure is effectively reduced, and the economic cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cement-based 3D printing structure, and particularly relates to a printing structure design and parameter optimization method based on a process defect tolerance coefficient. BACKGROUND

[0002] As a new construction method integrating mechatronics and additive manufacturing, building 3D printing technology realizes automatic forming of structures through layer-by-layer accumulation of cement-based materials, and has significant advantages such as high design freedom, short construction period, and high material utilization rate, and shows broad application prospects in the fields of special-shaped structure construction and emergency engineering repair. However, inherent process defects such as rheological properties of cement-based materials, cumulative errors of printing paths, and differences in interlayer bonding performance, cause the design theory of 3D printing structures to lag behind the needs of engineering practice for a long time. At present, the industry generally lacks special design specifications for printing concrete structures, and there are technical gaps in key links such as optimization of printing parameters (such as matching of extrusion rate and path planning), quality evaluation standards (such as interlayer strength detection methods), which cause problems such as poor mechanical property consistency of printed components, difficulty in quantifying structural safety reserves, and seriously restrict the standardization conversion process from material performance to structural bearing capacity.

[0003] In order to solve the above problems, the design of the printing structure adopts the following two schemes: one is to blindly enlarge the safety factor (usually by 20%-30%) according to the traditional cast-in-place concrete structure specification, which leads to waste of materials and sharp increase in construction cost; the other is to verify the structural reliability through a reduced-scale model test, but the scale effect of the printing process makes it difficult to directly extrapolate the test results, and the economic cost and time cost of full-size testing are extremely high. In addition, there is a lack of dynamic parameter adjustment mechanism in the construction process, which cannot correct the printing parameters in real time according to environmental temperature and humidity, equipment operating state and the like, further aggravating the uncertainty of the structure quality. SUMMARY

[0004] The present application aims to solve the problem that the existing lack of quantitative design methods for cement-based 3D printing structures cannot realize precise matching of printing parameters and structural performance, and provides a printing structure design and parameter optimization method based on a process defect tolerance coefficient.

[0005] In a first aspect, the present application provides a printing structure design and parameter optimization method based on a process defect tolerance coefficient, comprising the following steps: S1, obtaining initial parameters of a printing structure, determining printing parameters in a printing process according to the initial parameters of the printing structure, the printing parameters including printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters; S2, calculating a process defect tolerance coefficient according to the printing parameters, and the calculation formula of the process defect tolerance coefficient is:

[0006] In the formula is a process defect tolerance coefficient, K is an expansion coefficient, Ω is a structure safety correction parameter, composed of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, curing parameters; S3, evaluating the structure type of the printing structure according to the process defect tolerance coefficient, judging whether it is qualified, if qualified, obtaining the printing scheme of the printing structure, if not qualified, adjusting the initial parameters of the printing structure, repeating steps S1-S3, and designing a qualified printing scheme.

[0007] Preferably, the initial parameters of the printing structure include structure type and structure size, the structure type is determined according to topography and construction control elements, and the structure size includes cross-sectional size, etc.

[0008] Preferably, the printing material parameters include the strength performance and durability performance of the material in the pouring process and the printing process. The printing path parameters include printing strip spatial layout, structure cross-section neutral axis position, and printing strip size. The model parameters include overhang angle, maximum cross-section, model size, and volume. The equipment parameters include walking speed, extrusion rate, maximum printing cross-section walking time and interval, extrusion nozzle shape, material mixing time / pot number, and pumping / extrusion pressure. The printing environment parameters include temperature, humidity, and wind speed. The curing parameters include curing method and parameters.

[0009] Preferably, the expansion coefficient is related to printing environment, structure form landing, and technical maturity, and the range of the expansion coefficient is 0.8-1.8.

[0010] Preferably, the calculation formula of the structure safety correction parameter is:

[0011] In the formula , , p, , are printing material parameter factor, printing path parameter factor, equipment parameter factor, curing parameter factor, printing environment parameter factor, and model precision factor, respectively. are the weight proportions of printing material parameters, printing path parameters, equipment parameters, curing parameters, printing environment parameters, and model precision, respectively.

[0012] Preferably, the calculation formula of the printing material parameter factor is:

[0013] In the formula, is the printing test piece strength grade, is the project required pouring piece strength grade, is the printing test piece durability grade, is the project required pouring piece durability grade; and / or the calculation formula of the equipment parameter factor is as follows:

[0014] In the formula, is the minimum interlayer real bonding surface area, is the theoretical interlayer bonding surface area, is the minimum interstrip real bonding surface area, theoretical interstrip bonding surface area; and / or the calculation formula of the curing parameter factor is as follows:

[0015] In the formula, is the average value of the rebound strength of the printed structure entity after curing, is the error value of the rebound strength of the printed structure entity after curing; and / or the printing environment parameter factor is 1 at an ambient temperature of 15-25℃, is the same value as the printing material parameter factor at an ambient temperature of 5-15℃, 25-35℃, and is 0 below 5℃ or above 35℃; and / or if in-situ printing and / or mature rectangular nozzle printing process is adopted, the model accuracy factor is 1; if subsequent secondary assembly / installation is adopted, the calculation formula of the model accuracy factor is:

[0016] In the formula, is the number of key parameters; is the weight of the i-th key parameter, is the i-th model key parameter value of the printing model, is the i-th model key parameter value of the printing structure.

[0017] Preferably, the calculation formula of the printing path parameter factor is:

[0018] A is the theoretical cross-sectional area of the printing model cross-section, A' is the theoretical cross-sectional area of the printing strip cross-section; When bending / shearing, the calculation formula of the printing path parameter factor is:

[0019] is the ratio of the theoretical printing cross-sectional area to the theoretical pouring model cross-sectional area, is the ratio of the moment of inertia of the printing cross-section composed of several printing strips to the moment of inertia of the theoretical pouring model cross-section, is the moment of inertia of the printing cross-section composed of several printing strips, is the moment of inertia of the theoretical pouring model cross-section, is the number of printing strips of the printing cross-section, is the distance from an arbitrary microelement in the cross-section of the i-th printing strip to the neutral axis of the printing cross-section, is the distance from an arbitrary microelement in the cross-section of the pouring model to the neutral axis, is the area of the cross-section of the i-th printing strip, d is the microelement area in the cross-section of the i-th printing strip; When twisting, the calculation formula of the printing path parameter factor is:

[0020] is the polar moment of inertia of the printing cross-section about the center, is the polar moment of inertia of the pouring model cross-section about the center, is the number of printing strips of the printing cross-section, is the distance from an arbitrary microelement in the cross-section of the i-th printing strip to the center of the printing cross-section, is the distance from an arbitrary microelement in the cross-section of the pouring model to the center, is the area of the cross-section of the i-th printing strip.

[0021] Preferably, the value range of is 0.2-0.8, the value range of is 0.1-0.5, the value range of is 0.1-0.5, the value range of is 0-0.2, the value range of is 0-0.2, the value range of is 0.8-1.2.

[0022] Preferably, the detailed method for evaluating the structure type of the printing structure according to the process defect tolerance coefficient is: add the process defect tolerance coefficient to the structure type industry evaluation method to establish a structure type evaluation model;​ Based on the initial parameters of the printed structure and the process defect tolerance coefficient, it is determined whether the structure type evaluation model is met. If the structure type evaluation model is met, the printed structure is evaluated as qualified; otherwise, it is unqualified.

[0023] Preferably, the structure type evaluation model is as follows:

[0024] In the formula, R() is the bearing capacity function of the component; α d Design values ​​for geometric parameters; S is the structural importance coefficient; S is the design value of the combined effect. f d This refers to the design value for the material strength grade. f c打印构件回弹值 This represents the measured springback value of the printed component.

[0025] Preferably, the method further includes S4: performing an economic estimate on the printed structure that has passed the structural type evaluation, and determining whether it is qualified. If qualified, a printing scheme for the printed structure is obtained; if unqualified, the printing parameters are adjusted, and steps S2 to S4 are repeated to design a qualified printing scheme.

[0026] In a second aspect, the present invention provides a system for designing and optimizing printed structures and parameters based on process defect tolerance coefficients, for executing the above-described method for designing and optimizing printed structures and parameters, the system comprising: The parameter acquisition module is used to acquire the initial parameters of the printed structure and determine the printing parameters during the printing process based on the initial parameters of the printed structure. The printing parameters include printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. The calculation module is used to calculate the process defect tolerance coefficient based on the printing parameters. The formula for calculating the process defect tolerance coefficient is as follows:

[0027] In the formula The process defect tolerance coefficient is K, the expansion coefficient is Ω, and the structural safety correction parameter is composed of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. The judgment module is used to evaluate the structure type of the printed structure according to the process defect tolerance coefficient, and determine whether it is qualified. If it is qualified, the printing scheme of the printed structure is obtained. If it is unqualified, the initial parameters of the printed structure are adjusted and steps S1 to S3 are repeated to design a qualified printing scheme.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: 1.The present application provides a printing structure design and parameter optimization method based on process defect tolerance coefficient. By introducing the process defect tolerance coefficient, the quantitative evaluation of civil engineering additive manufacturing components / structures is realized, the design and parameter optimization for 3D printed concrete structures are constructed, and the quality evaluation system framework is formed. This innovation breaks through the technical bottleneck of traditional printing quality consistency, solves the problem of standardized conversion from printing materials to structural components, and effectively eliminates potential safety hazards and technical uncertainties in engineering applications.

[0029] 2.The present application provides a printing structure design and parameter optimization method based on process defect tolerance coefficient. By introducing the process defect tolerance coefficient, the quantitative evaluation of civil engineering additive manufacturing components / structures is realized, the design and parameter optimization for 3D printed concrete structures are constructed, and the quality evaluation system framework is formed. This innovation breaks through the technical bottleneck of traditional printing quality consistency, solves the problem of standardized conversion from printing materials to structural components, and effectively eliminates potential safety hazards and technical uncertainties in engineering applications. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flowchart of the printing structure design and parameter optimization method based on process defect tolerance coefficient of the present application; Figure 2 The schematic diagram of the reference coordinate system and XYZ sub-coordinate system in the printing model; Figure 3 The flowchart of the printing structure design and parameter optimization method based on process defect tolerance coefficient in Example 2; Figure 4 The schematic diagram of the single arch block walking path in Example 2. DETAILED DESCRIPTION

[0031] The present application will be further described in detail below in conjunction with specific embodiments. However, it should not be understood that the scope of the above-mentioned subject matter of the present application is limited to the following examples, and any technology realized based on the content of the present application falls within the scope of the present application.

[0032] Example 1 As shown in Figure 1 , the present application provides a printing structure design and parameter optimization method based on process defect tolerance coefficient, which includes the following steps: S1, obtaining the initial parameters of the printing structure, determining the printing parameters in the printing process according to the initial parameters of the printing structure, the printing parameters including printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters; S2, calculating the process defect tolerance coefficient according to the printing parameters, the calculation formula of the process defect tolerance coefficient is:

[0033] wherein is a process defect tolerance coefficient, K is an expansion coefficient, and Ω is a structure safety correction parameter, which is composed of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters; S3. Evaluating the printing structure according to the process defect tolerance coefficient to determine whether it is qualified, if yes, obtaining the printing scheme of the printing structure, if not, adjusting the initial parameters of the printing structure and repeating steps S1-S3 to obtain a qualified printing scheme.

[0034] In step S1, the initial parameters of the printing structure include a structure type and a structure size, the structure type is determined according to terrain analysis and construction control elements, and the structure size includes a cross-sectional size and the like.

[0035] In the structure type determination, the terrain analysis is performed by preliminary investigation through a scale topographic map, combined with field reconnaissance to evaluate the terrain slope, geological stability and the distribution of surrounding obstacles, and complex terrain is preferentially selected to adopt adaptive printing structures such as overhangs and arches, and flat terrain is selected to adopt standardized printing structure forms, so as to ensure that the printing structure matches the terrain conditions. The construction control follows the principle of "controlling first and then detailing", triangular or tri-lateral networks are used in areas with large terrain undulations, traverse networks are laid out in flat and difficult-to-see areas, and building square networks are set in regular sites. The control points need to meet the requirements of visibility, stability and measurement convenience, and are buried by using concrete piles or rock monuments, and plane and elevation control networks are established by using total station and GPS equipment, and the precision meets the standard requirements. According to the terrain survey data, the structure form is selected, and the structure parameters are determined in combination with the accuracy level of the construction control network. Lightweight fabricated structures are preferentially used in mountainous areas, and modular design is selected in urban dense areas, and the operation radius of the construction equipment and the distribution of the control points are considered to ensure the construction feasibility of the structure.

[0036] Based on the existing working conditions, the printing parameters used in the project are determined, including printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. The printing material parameters include the strength performance and durability performance of the material in the pouring process and the printing process. Specifically, the material's printable performance, the hardening performance of the pouring test piece, and the hardening performance of the printing test piece are included. It also includes material number, mixing water quantity, raw material state / batch, and equipment number used. The printing path parameters include the simplified printing strip spatial layout, the neutral axis position in the structural section, and the printing strip size (long, wide, and high boundaries). The printing strip size is the long, wide, and high boundaries of the printing strip. More specifically, the path interval, slice layer height, filling method, and whether the interlayer walking is continuous are included. The model parameters include the cantilever angle, maximum cross-section, model size, volume, necessary dimensions such as length, width, and height, and the maximum cantilever angle. The equipment parameters include walking speed, extrusion rate, maximum printing cross-section walking time and interval, extrusion nozzle shape, material mixing time / kettle number, pumping / extrusion pressure, and other related parameters. It also includes single size boundary, cantilever boundary, running parameters (such as turning, walking speed variation), and composite process boundary, thereby determining the real bonding area between the printing strips under the printing path of the project, including the side bonding surface and the interlayer bonding surface. The printing environment parameters include temperature, humidity, wind speed, etc. The curing parameters include curing methods and parameters, such as steam curing, temperature rise / constant / drop, static stop, and other related parameters.

[0037] For the process defect tolerance coefficient γ PDTC ( Process Defect Tolerance Coefficient, PDTC) is used to expand the load to determine the selection and size of the printing structure.

[0038]

[0039] If the calculated process defect tolerance coefficient value is less than 0.8, it proves that the material and / or structure selection is too conservative, and it is recommended to reduce the strength and / or durability grade of the printing material. If the calculated process defect tolerance coefficient value is between 0.8 and 1, it proves that the material and / or structure selection is appropriate, and the conclusion of the conventional structure budgeting method can be directly used. The process defect tolerance coefficient is defaulted to 1.

[0040] wherein the expansion coefficient is related to printing environment, structural form landing, technical maturity and other parameters, and the range of the expansion coefficient is 0.8-1.8. For general printing environment, non-first structural form landing and other conventional conditions, the expansion coefficient value is 1.2, and for first structural form landing, extreme printing environment, low technical maturity and other unconventional conditions, the expansion coefficient value is 1.5. The determination of general printing environment and extreme printing environment is based on the experience of those skilled in the art, and low technical maturity is determined based on the experience of those skilled in the art.

[0041] The calculation formula of the structural safety correction parameter is:

[0042] wherein , , p, , are printing material parameter factor, printing path parameter factor, equipment parameter factor, maintenance parameter factor, printing environment parameter factor and model precision factor, respectively. are the weight proportions of printing material parameter, printing path parameter, equipment parameter, maintenance parameter, printing environment parameter and model precision, respectively.

[0043] The printing material parameter factor, printing path parameter factor, equipment parameter factor, maintenance parameter factor, printing environment parameter factor and model precision factor are described in detail as follows.

[0044] For the printing material parameter factor, in the actual printing environment, the printing material parameter factor is the ratio product between the strength grade and the durability grade between the anisotropic printing test piece and the cast piece. If it is a conventional environment, only the steel bar corrosion performance of the material needs to be considered, and if it is an unconventional environment, it needs to be refined according to the weight and considered respectively. The calculation formula of the printing material parameter factor is:

[0045] wherein is the strength grade of the printing test piece, is the strength grade of the cast piece required by the project, is the durability grade of the printing test piece, is the durability grade of the cast piece required by the project. As for the identification of the strength grade of the printed test piece, according to the particularity of the mechanical properties of the printed test piece, the anisotropy degree is characterized by the invention patent with the publication number CN114414343B, a method for characterizing the anisotropy of cement-based 3D printed components. If the mechanical anisotropy coefficient I is less than or equal to 15%, the mechanical properties of each direction are tested in turn, the face load test results of each direction are not less than 3, and the line load test results are not less than 6. The strength grade of the printed test piece is divided according to the Concrete Strength Test and Evaluation Standard (GB / T 50107-2010). For the mechanical properties of the printed test piece of the same material and engineering parameters, and I>15%, the strength grade is divided according to the direction of the minimum ultimate load. The specific mechanical property grade evaluation method of 3D printed concrete material and test piece is determined as follows: According to the Concrete Strength Test and Evaluation Standard (GB / T 50107-2010), the compressive strength grade of 3D printed concrete material and test piece is determined. Among them, the concrete cube compressive strength f cu,o The formula is expressed as follows:

[0046] In the formula, f cu,o is the cube compressive strength, with the unit of MPa; f cu,k is the cube compressive standard strength, with the unit of MPa.

[0047] According to the Concrete Strength Test and Evaluation Standard (GB / T 50107-2010), the axial tensile strength grade of 3D printed concrete material and test piece is determined, and the specific strength grade is shown in Table 1. Among them, the formula of the axial tensile strength standard value f tk is expressed as follows:

[0048] In the formula, is the conversion axial tensile strength coefficient of the splitting tensile strength, when the test piece is a standard test piece of 150mmx150mmx150mm, then the value is 0.9; if a non-standard test piece of 100mmx100mmx100mm is used, then the value is 0.85; R t is the splitting tensile strength, with the unit of MPa; F is the ultimate load, with the unit of N; A is the area of the test piece splitting surface, with the unit of mm 2 . The strength grade of the cast piece is also determined according to the above identification of the strength grade of the printed test piece.

[0049] Table 1 Axial tensile strength standard value corresponding to concrete strength grade

[0050] Regarding the determination of the durability performance grade of the printed test piece, according to the particularity of the mechanical properties of the printed test piece, the degree of anisotropy is characterized by the method for characterizing the anisotropy of a cement-based 3D printed component according to the patent CN114414343B, if the anisotropy coefficient I of the durability performance is less than or equal to 15%, then the durability performance of each direction is tested in turn, the test results of each direction are not less than 3, the test results of the line are not less than 6, and the durability performance grade evaluation method refers to the standard JGJ / T 193-2009 for testing and evaluating the durability of concrete. For the durability performance of the printed test piece under the same material and engineering parameters, and I > 15%, the durability grade is divided according to the most unfavorable direction. The durability grade of the cast component is also determined according to the determination of the durability grade of the printed test piece.

[0051] The printing path parameter factor is based on the influence of the spatial layout of the printing strip under the printing path planning on the overall performance of the printed structure.

[0052] Since the printed structure is composed of printing strips arranged at fixed positions and weak connections, it can be divided into process defect areas and printed entities. Among them, the process defect area is divided into side defects, top defects and internal printing strip defects caused by the printing process.

[0053] After establishing the printing model of the printed structure, a reference coordinate system is established, the horizontal printing platform is defined as the LW plane, and the H direction is perpendicular to the horizontal printing platform, that is, the L direction is the length direction of the printing model, the W direction is the width direction of the printing model, and the H direction is the height direction of the printing model. Based on the reference coordinate system, an XYZ sub-coordinate system is established, the center point of which is located at the point where the printing nozzle extrudes the material, X is the direction perpendicular to the cross section of the printing strip in the horizontal plane, Y is the direction perpendicular to the side of the printing strip in the horizontal plane, and Z is the direction perpendicular to the XY plane, that is, the three directions are orthogonal to each other, as shown in Figure 2 .

[0054] Classification and calculation are performed according to the stress type of the structure, as follows: When subjected to unidirectional compression, the calculation formula of the printing path parameter factor is:

[0055] In the formula, A is the theoretical cross-sectional area of the printing model cross section, and A' is the theoretical cross-sectional area of the printing strip cross section.

[0056] Among them, when the walking direction is the same as the compression direction (i.e., the L direction is consistent with the X direction) or the compressive strength of the printed structure is isotropic (I≤15%), based on the plane section assumption, the theoretical cross-sectional area of ​​the printed model can be simplified to A=A'+B+C+D, where B, C, and D are the side defects, top defects, and internal printing strip defects caused by the printing process, respectively. Figure 2 Based on experience and prior research, it is deduced that the interlayer bonding width and height of the extruded strip under a rectangular nozzle are consistent with the theoretical width w (interlayer printing path travel interval) and theoretical height h (path slice layer height) of the printing strip. Therefore, A' = A under a rectangular nozzle. For a circular nozzle, the average width of the interlayer core bonding is assumed to be... The average height of the inter-strip core bonding is 2 / 3w. The value is 1 / 2h, and the number of columns and layers printed are c and l respectively. n = c l n is the number of printed strips within the printed cross-section. Let be the theoretical height of the cross-section of the i-th printed strip. Let be the theoretical width of the cross-section of the i-th printed strip.

[0057] Therefore, A' under the circular nozzle can be simplified to:

[0058]

[0059]

[0060]

[0061]

[0062] The formula for calculating the print path parameter factor during bending / shearing is as follows:

[0063] In the formula This is the ratio of the theoretically printed cross-sectional area to the theoretically cast cross-sectional area. This represents the ratio of the moment of inertia of the printed cross-section, composed of several printed strips, to the cross-section of the theoretical cast model. Let be the moment of inertia of the printed cross section composed of several printing strips. The moment of inertia of the cross-section of the theoretically cast model. The number of print strips for the printed cross section. Let be the distance from any infinitesimal element within the cross-section of the i-th printing strip to the neutral axis of the printing cross-section. Let be the distance from any infinitesimal element within the cross-section of the casting model to the neutral axis. A is the area of the cross section of the i-th printing strip d is the infinitesimal area in the cross section of the i-th printing strip When the walking direction is perpendicular to the bending moment direction or the tensile stress of the printed part is completely borne by the steel bars and other reinforcement measures, the calculation formula of the printing path parameter factor is:

[0064] In the formula, A is the area of the cross section of the i-th printing strip i d is the width of the cross section of the i-th printing strip parallel to the neutral axis direction of the printing cross section

[0065] When the walking direction is perpendicular to the bending moment direction or the tensile stress of the printed part is completely borne by the steel bars and other reinforcement measures, the calculation formula of the printing path parameter factor is:

[0066] I is the polar moment of inertia of the printing cross section about the center I is the polar moment of inertia of the pouring model cross section about the center N is the number of printing strips of the printing cross section d is the distance from an arbitrary infinitesimal in the cross section of the i-th printing strip to the center of the printing cross section d is the distance from an arbitrary infinitesimal in the cross section of the pouring model to the center of the cross section A is the area of the cross section of the i-th printing strip

[0067] When the walking direction is perpendicular to the bending moment direction or the tensile stress of the printed part is completely borne by the steel bars and other reinforcement measures, the calculation formula of the printing path parameter factor is:

[0068] Under the premise of fixed equipment parameters, the equipment parameter factor is the ratio between the actual bonding surface between the printing strips and the set theoretical bonding surface. Among them, it includes the side bonding between the strips and the interlayer bonding; (the actual bonding surface is obtained by the device and test method in the invention patent with the publication number CN114563345A “Cement-based 3D printing test piece interlayer bonding strength testing device and test method”), and the calculation formula of the equipment parameter factor is as follows:

[0069] In the formula, A is the area of the cross section of the i-th printing strip is the minimum value; is the minimum interlayer actual bonding surface area is the theoretical interlayer bonding surface area, that is, the printing path walking interval w x walking length in the layer is the minimum interlayer actual bonding surface area is the theoretical interlayer bonding surface area, that is, the printing path walking interval w x walking length in the layer The curing parameter factor is the difference between the average value of the rebound strength of the printed structure entity after curing and the error value, divided by the average value. The calculation formula of the curing parameter factor is as follows:

[0070] In the formula, is the average value of the rebound strength of the printed structure entity after curing, is the error value of the rebound strength of the printed structure entity after curing. The rebound strength test is performed. If a circular nozzle is used to complete printing or the flatness of the test surface does not meet the standard, the surface is polished to be flat, and the measurement is completed. If a rectangular nozzle is used to complete printing or the flatness of the test surface meets the standard, no processing is required. The rebound strength and test error are not limited to detection methods such as the rebound method and the ultrasonic-rebound comprehensive method.

[0071] For the printing environment parameter factor, the printing environment parameter factor is set to a value of 1 by default in a conventional environment between 15-25°C. In an environment temperature between 5-15°C and 25-35°C, the printing environment parameter factor takes the same value as the printing material parameter factor. If the temperature is below 5°C or above 35°C, the printing environment parameter factor is set to a value of 0 by default.

[0072] The model precision factor is the ratio of the key parameters (angle, cross-sectional size, length, etc.) between the spatial size of the printed structure entity and the printed model. If in-situ printing and / or mature rectangular nozzle printing technology is used, the default value of the model precision factor is 1. If subsequent secondary assembly / installation is used, the model precision factor is calculated by taking the weighted ratio according to the influence of the key parameters on the overall structural performance. The calculation formula of the model precision factor is as follows:

[0073] In the formula, is the number of key parameters, and the specific key parameters include angle, cross-sectional size, length, etc., is the weight of the i-th key parameter, is the i-th model key parameter value of the printed model, is the i-th model key parameter value of the printed structure.

[0074] In step S3, the goal of the structure type evaluation is to ensure that the printed structure can safely withstand various loads (such as dead load, live load, wind load, earthquake action, etc.) during construction and service life, and meet the requirements of normal use limit state (such as deformation, crack). The detailed method for structure type evaluation of the printed structure according to the process defect tolerance coefficient is as follows: Add the process defect tolerance coefficient to the structure type industry evaluation method to establish a structure type evaluation model. Establish a finite element stress analysis according to the geometric structure and boundary conditions of the structure design, According to the initial parameters of the printed structure and the process defect tolerance coefficient, it is judged whether the structure type evaluation model is satisfied. If the structure type evaluation model is satisfied, the printed structure is evaluated as qualified, otherwise it is not qualified. Specifically, according to the stress analysis calculation result, the theoretical bearing capacity design value and the limit state action combination effect value and the corresponding theoretical safety factor C1 are obtained, and the safety factor C is obtained by reducing the process defect tolerance coefficient, C=C1 / According to the requirements of the printing project, it is judged whether the safety factor is qualified.

[0075] Specifically, on the basis of the original structure type industry evaluation standard, the process defect tolerance coefficient is added to obtain the structure type evaluation model as follows:

[0076] In the formula, R() is the bearing capacity function of the component; a d is the geometric parameter design value; is the structure importance coefficient; S is the effect design value of action combination, f d is the material strength grade design value; f c打印构件回弹值 is the measured rebound value of the printed component.

[0077] For the printed structure of highway bridge and culvert, the durability design of highway bridge and culvert should meet the requirements of the bearing capacity limit state, and the bearing capacity and stability of the component should be calculated, and if necessary, the inclination and slip of the structure should be calculated. When using internal force form, the bearing capacity limit state calculation of bridge and culvert component should use the following expression:

[0078] Among them, the structure importance coefficient is taken as 1.1, 1.0 and 0.9 according to the structure design safety level of first, second and third level respectively, and the structure design safety level should meet the provisions of “General Specification for Design of Highway Bridge and Culvert” (JTG D60-2015); the effect design value of action combination should be calculated according to the provisions of “General Specification for Design of Highway Bridge and Culvert” (JTG D60-2015) for the durability design condition; the geometric parameter design value can adopt the geometric parameter standard value a k , that is, the value specified in the design file.

[0079] Through the above design and parameter optimization method, the initial parameters of the printed structure are adjusted based on the process defect tolerance coefficient, and the appropriate printing parameter interval is determined, so as to complete the parameter boundary control of material, path, model, environment, equipment and maintenance, thereby realizing the design and construction integration.

[0080] Example 2 The embodiment provides a printing structure design and parameter optimization method based on a process defect tolerance coefficient. In step S1, based on an existing working condition, initial parameters of a printing structure are acquired, that is, structure selection, size, material, path, model, equipment, maintenance, printing environment and other printing parameters are determined; in step S2, a process defect tolerance coefficient of extreme concrete printing is acquired, then structure stress and economic estimation are performed, whether it is qualified is judged, if yes, scheme comparison and selection are performed, a printing parameter interval is obtained, and if not, the initial parameters of the printing structure are adjusted. Figure 3 As shown in FIG. 12, similar to embodiment 1, the difference lies in that the method further includes S4, economic estimation is performed on the printing structure of which the structure type evaluation is qualified, whether it is qualified is judged, if yes, a printing scheme of the printing structure is obtained, and if not, the printing parameters are adjusted, and a qualified printing scheme is designed.

[0081] The target of the economic estimation is to evaluate the whole life cycle cost of the 3D printing project, cost (construction cost, time cost, energy consumption cost, safety cost and the like) constitution analysis, benefit and value analysis are performed, economic indexes are obtained, cost and investment return comparison analysis and the like are performed according to the economic indexes, whether the economy is qualified is judged according to the requirements of the printing project, if yes, a printing scheme of the printing structure is obtained, and if not, the printing parameters are adjusted, steps S2-S4 are repeated, and a qualified printing scheme is designed.

[0082] After the structure stress and economic estimation, a recommended scheme is determined, the recommended scheme is finely designed in a printing construction drawing design stage, wherein the main facilities such as bridges, culverts, tunnels and road auxiliary facilities inherit the standardization of structure forms and the individualization of cross section forms; the cultural landscape facilities inherit the individualization of structure forms and the standardization of cross section forms.

[0083] Embodiment 3 The embodiment provides a printing structure design and parameter optimization method based on a process defect tolerance coefficient. The method of embodiment 2 is adopted, and specifically, for a project of a conventional environment / high technical maturity / low special-shaped degree of a stress main structure / non-main structure stress special-shaped auxiliary facility, the structure safety correction parameters are as follows:

[0084] Since the civil engineering additive manufacturing is greatly influenced by an (printing, use) environment, process maturity, model special-shaped degree, the weights of various factors are not fixed, and weight optimization needs to be performed on the basis of the rest conditions, to meet the following inequalities

[0085]

[0086]

[0087]

[0088] A 3D-printed concrete landscape arch bridge is planned to be printed, and the cross-sectional size design has been completed. The main arch ring uses the pouring process, and the material design strength grade is C30. The material durability meets D100, fully meeting the project requirements, and the theoretical safety factor C1>1.5. Therefore, it is necessary to ensure the reliability of the 3D printing process. The main arch ring design uses a circular arc with a radius of 3.6 m, the arch ring thickness is 35 cm (with a 20 cm cavity inside), the calculated span is 6 m, the calculated rise is 1.6 m, the rise-span ratio is 1 / 3.75, and the printing structure design and parameter optimization method based on the process defect tolerance coefficient is used.

[0089] According to the current situation of the project being in a regular environment, the construction unit having high process maturity, and the model being less heterogeneous, the general formula is used to calculate K=1.2.

[0090] Material parameter factor: the mixing ratio of the printing material used is C50 普 as shown in Table 2.

[0091] Table 2 Optimal mixing ratio C50 普 (wt. %)

[0092] According to the test method, the compressive strength, splitting strength, and flexural strength of the pouring piece and the 3D-printed test piece at an age of 28 days were tested, and the test results are shown in Tables 3, 4, and 5. At the same time, the data of the splitting strength was converted into the axial tensile strength, as shown in Table 6.

[0093] Table 3 F x28 , F y28 , F z28 cube compressive strength data table

[0094] Table 4 Test data table of splitting strength under F xy , F xz , F yx , F yz , F zx , F zy six line loads

[0095] Table 5 Test data table of splitting strength under F xy , F xz , F yx , F yz , F zx , F zyTest data of flexural strength under six line loads

[0096] Table 6 F xy , F xz , F yx , F yz , F zx , F zy Table of calculation results of axial tensile strength under six line loads

[0097] From the above table, the average strength of the pouring piece with mix proportion C50 is 71.3MPa>>57.5Mpa, and the strength loss of the printed test piece is 80.33%. Based on the mechanical anisotropy coefficient formula, it can be calculated that Ic28d is 8.15%, which can be used to judge the average value of the mechanical properties of the printed test piece. At the same time, the average value of the printing strength of the mix proportion C50 普 is 57.27MPa≈57.5MPa, which basically meets the compressive strength requirements of the strength grade C50.

[0098] At the same time, based on the mechanical anisotropy coefficient formula, it can be easily known that Ip28d is much greater than 15%, and the X-Z direction can be used as the basis for strength grade evaluation. As shown in Table 6, the in this direction is 2.699MPa>2.64MPa, so it is classified as C50 according to the standard value of the axial tensile strength of concrete, and it is also proved that the mix proportion C50 普 meets the strength requirements of the strength grade C50.

[0099] In summary, the printing strength grade of the mix proportion C50 普 selected by the complex mixing basically meets the C50 strength requirements.

[0100] At the same time, the carbonation resistance, chloride ion resistance and frost resistance of the material C40 普 are in the order of T-Ⅳ (recommended opinion on durability performance level: good), RCM-V (recommended opinion on durability performance level: very good), and “D100” (F200). It shows that the material meets the material requirements of reinforced concrete buildings in fresh water environment (frozen areas, slightly frozen areas), plain concrete buildings (severely frozen areas) and other application scenarios. Therefore, the printing material parameter factor =50 / 30×100 / 100=1.67.

[0101] Printing path parameter factor: in view of the isotropic compressive strength of the printed part of the material, the stress mode is unidirectional compression, arch ring, and the single model after division is relatively simple. The model filling mode is determined as "Hanzi" type filling, that is, equidistant spiral multi-segment line type slicing. The spatial path fitting technology is adopted to carry out three-dimensional oblique spatial plane slicing printing. The extrusion tool end shape adopts a rectangle (38mm×12mm), the slicing height adopts 12mm, the plane path interval is 38mm, the plane path fitting slicing control technology is adopted to change the printing head posture. The single arch block adopts Figure 4 walking path, and the printing is completed, that is, two printing strips are parallel. The value is 1.

[0102] The device parameter factor adopts the device and test method of the "cement-based 3D printing test piece interlayer bonding strength testing device and testing method" invention patent to take the real bonding surface, and the printing parameters used in the project are used alone, that is, the extrusion tool end shape adopts a rectangle (38mm×12mm), the slicing height adopts 12mm, the plane path interval is 38mm, the pumping speed is 8r / min, and the walking speed is 12cm / s. The printing of two printing strips is completed, the printing layer number is 2 layers, the printing length is 2m, and three printing test pieces A, B and C are printed. The real bonding width and length are measured by a ruler, and the real bonding height is measured by an electronic vernier caliper. The test results are shown in Table 7.

[0103] Table 7 Test results of three printing test pieces

[0104] Therefore, the device parameter factor p=98.1%×98.2%=0.963.

[0105] Curing parameter factor: the average value and error value of the rebound strength of the printed structure entity are 45.3MPA and 5.2Mpa respectively, so =(45.3-5.2) / 45.3=0.865.

[0106] In view of the fact that the project is in a conventional environment (20℃±5℃) and a mature rectangular nozzle printing process, the printing environment parameter factor and the model precision factor are both 1.

[0107] Therefore, =1.2× =0.96≈1≥30 / 45.3=0.66 Therefore, the safety factor C=C1 / >1.5, which ensures the safety factor unchanged without modifying the original cross-sectional size in the early stage. The printing material printing process parameters used in the project are conservative, and the calculation results fully meet the engineering requirements.

[0108] Example 4 A system for designing and optimizing printed structures based on process defect tolerance coefficients, used to execute the method for designing and optimizing printed structures in Example 1, the system comprising: The parameter acquisition module is used to acquire the initial parameters of the printed structure and determine the printing parameters during the printing process based on the initial parameters of the printed structure. The printing parameters include printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. The calculation module is used to calculate the process defect tolerance coefficient based on the printing parameters. The formula for calculating the process defect tolerance coefficient is as follows:

[0109] In the formula Ω is the process defect tolerance coefficient, K is the amplification coefficient, and Ω is the structural safety correction parameter, which consists of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. The judgment module is used to evaluate the structure type of the printed structure according to the process defect tolerance coefficient, and determine whether it is qualified. If it is qualified, the printing scheme of the printed structure is obtained. If it is unqualified, the initial parameters of the printed structure are adjusted and steps S1 to S3 are repeated to design a qualified printing scheme.

[0110] This embodiment also provides an electronic device, including at least one processor, a memory communicatively connected to the at least one processor, and at least one input / output interface communicatively connected to the at least one processor. The memory stores instructions executable by the at least one processor, which, when executed, enable the at least one processor to perform the printed structure design and parameter optimization method based on process defect tolerance coefficient of Embodiment 1 described above. The input / output interface may include a display, keyboard, mouse, and USB interface for inputting and outputting data. The electronic device may be a client-side electronic device, such as a mobile phone, laptop, tablet computer, or desktop computer, to execute the printed structure design and parameter optimization method based on process defect tolerance coefficient of Embodiment 1.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for printing structure design and parameter optimization based on process defect tolerance coefficient, characterized in that, The method comprises the following steps: S1, obtaining printing structure initial parameters, determining printing parameters in a printing process according to the printing structure initial parameters, the printing parameters comprising printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters; S2, calculating a process defect tolerance coefficient according to the printing parameters, and a calculation formula of the process defect tolerance coefficient being: In the formula K is the process defect tolerance coefficient, K is the expansion coefficient, Ω is the structure safety correction parameter, which is composed of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and maintenance parameters. S3, evaluating a structure type of a printing structure according to the process defect tolerance coefficient, determining whether the printing structure is qualified, if the printing structure is qualified, obtaining a printing scheme of the printing structure, if the printing structure is not qualified, adjusting the printing structure initial parameters, and repeating steps S1-S3 to design a qualified printing scheme.

2. The method of printing structure design and parameter optimization of claim 1, wherein, The printing structure initial parameters comprise a structure type and a structure size, the structure type being determined according to a terrain and a construction control element, and the structure size comprising a cross-sectional size; The printing material parameters comprise strength performance and durability performance of a material in a pouring process and a printing process in each direction; The printing path parameters comprise a printing strip spatial layout, a structure cross-sectional neutral axis position, and a printing strip size; The model parameters comprise a cantilever angle, a maximum cross section, a model size, and a volume; The equipment parameters comprise a walking speed, an extrusion speed, a maximum printing cross-sectional walking time and interval, an extrusion nozzle shape, a material mixing time / pot number, and a pumping / extrusion pressure; The printing environment parameters comprise a temperature, a humidity, and a wind speed; The curing parameters comprise a curing mode and parameters; The expansion coefficient is related to a printing environment, a structure form landing, and a technical maturity parameter, and the expansion coefficient ranges from 0.8 to 1.

8.

3. The method of printing structure design and parameter optimization of claim 1, wherein, A calculation formula of the structure safety correction parameter is: In the formula , , p, , are a printing material parameter factor, a printing path parameter factor, a device parameter factor, a curing parameter factor, a printing environment parameter factor, a model precision factor, respectively, are weight proportions of the printing material parameter, the printing path parameter, the device parameter, the curing parameter, the printing environment parameter, and the model precision, respectively.

4. The method of printing structure design and parameter optimization of claim 3, wherein, A calculation formula of the printing material parameter factor is: In the formula is the strength grade of the printed test piece, is the strength grade of the cast piece, is the durability grade of the printed test piece, is the durability grade of the cast piece; A calculation formula of the equipment parameter factor is: wherein is the minimum interlayer real bond area, is the theoretical interlayer bond area, is the minimum interstrip real bond area, theoretical interstrip bond area; A calculation formula of the curing parameter factor is: In the formula is the average value of the rebound strength of the printed structure entity after curing, is the error value of the rebound strength of the printed structure entity after curing. If an ambient temperature is 15-25 ℃, the printing environment parameter factor is 1, if the ambient temperature is 5-15 ℃ or 25-35 ℃, the printing environment parameter factor is the same as the printing material parameter factor, and if the ambient temperature is below 5 ℃ or above 35 ℃, the printing environment parameter factor is 0; If an in-situ printing or a rectangular nozzle printing process is adopted, the model precision factor is 1, if a secondary assembly or installation is adopted subsequently, a calculation formula of the model precision factor is: wherein is the number of key parameters; is the weight of the i-th key parameter, is the i-th model key parameter value of the printing model, is the i-th model key parameter value of the printing structure.

5. The method of printing structure design and parameter optimization of claim 3, wherein, In a uniaxial compression, a calculation formula of the printing path parameter factor is: In the formula, A is a theoretical cross-sectional area of a printing model cross section, and A' is a theoretical cross-sectional area of a printing cross section; In a compression bending / shearing, a calculation formula of the printing path parameter factor is: wherein is the ratio of the theoretical print cross-sectional area to the theoretical casting model cross-sectional area, is the ratio of the print cross-sectional area composed of several print strips to the inertia moment of the theoretical casting model cross-section, is the inertia moment of the print cross-section composed of several print strips, is the inertia moment of the theoretical casting model cross-section, is the number of print strips of the print cross-section, is the distance of an arbitrary microelement within the cross-section of the ith print strip to the neutral axis of the print cross-section, is the distance of an arbitrary microelement within the cross-section of the casting model to the neutral axis, is the area of the cross-section of the ith print strip, d is the microelement area within the cross-section of the ith print strip; In a torsion, a calculation formula of the printing path parameter factor is: Jp = the polar moment of inertia of the print cross section about the center, Jm = the polar moment of inertia of the mold cross section about the center, N = the number of print strips of the print cross section, r = the distance from an arbitrary microelement in the i-th print strip cross section to the center of the print cross section, R = the distance from an arbitrary microelement in the mold cross section to the center of the mold cross section, A = the area of the i-th print strip cross section.

6. The method of printing structure design and parameter optimization of claim 3, wherein, ranging from 0.2 to 0.8, ranging from 0.1 to 0.5, ranging from 0.1 to 0.5, ranging from 0 to 0.2, ranging from 0 to 0.5, ranging from 0.8 to 1.

2.

7. The method of printing structure design and parameter optimization of claim 1, wherein, A detailed method for evaluating a structure type of a printing structure according to the process defect tolerance coefficient is: A structure type evaluation model is established by adding the process defect tolerance coefficient into a structure type industry evaluation method; Whether the structure type evaluation model is met is determined according to the printing structure initial parameters and the process defect tolerance coefficient, if the structure type evaluation model is met, the structure type evaluation of the printing structure is qualified, and otherwise, the structure type evaluation of the printing structure is not qualified.

8. The method of printing structure design and parameter optimization of claim 7, wherein, The structure type evaluation model is: where R() is the component load bearing function; a d is the geometric parameter design value; is the structural importance coefficient; S is the effect design value of the action combination, f d is the material strength grade design value; f c打印构件回弹值 is the measured resilience value of the printed component.

9. The method of printing structure design and parameter optimization according to any one of claims 1-8, wherein, The method further comprises S4, performing economic estimation on the printing structure that passes the structure type evaluation, judging whether it is qualified, if qualified, obtaining the printing scheme of the printing structure, if not qualified, adjusting the printing parameters, repeating steps S2-S4, and designing a qualified printing scheme.

10. A printing structure design and parameter optimization system based on process defect tolerance factor, characterized in that, The system is used for executing the printing structure design and parameter optimization method in any one of claims 1-9, and comprises: A parameter acquisition module is configured to acquire initial parameters of a printing structure, determine printing parameters in a printing process according to the initial parameters of the printing structure, and the printing parameters include printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and curing parameters. A calculation module is configured to calculate a process defect tolerance coefficient according to the printing parameters, and a calculation formula of the process defect tolerance coefficient is: In the formula K is the process defect tolerance coefficient, K is the expansion coefficient, Ω is the structure safety correction parameter, which is composed of printing material parameters, printing path parameters, model parameters, equipment parameters, printing environment parameters, and maintenance parameters. A judgment module is configured to perform structure type evaluation on the printing structure according to the process defect tolerance coefficient, judge whether it is qualified, if qualified, obtain the printing scheme of the printing structure, if not qualified, adjust the initial parameters of the printing structure, repeat steps S1-S3, and design a qualified printing scheme.

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