Method and system for improving buildability of inclined 3D printed concrete based on finite element simulation

Abstract

This invention relates to a method and system for improving the constructability of inclined 3D printed concrete based on finite element simulation. The method includes: modeling the inclined 3D printed structure, performing strip division, segment division, and mesh division to obtain the target model, constructing a set of elements and nodes for each segment, and setting the model parameters of the target model; activating the element set, nozzle constraints, and extrusion pressure of the corresponding segment segment by segment, assigning age variables to the activated nodes, and applying gravity to the activated parts; performing finite element calculations on the segment-by-segment activation process until the structure is significantly damaged, obtaining the maximum printable height and corresponding deformation before damage; adjusting the process parameters, remodeling if the initial inclined 3D printed geometry changes, otherwise resetting the process parameters until the maximum printable height is maximized and the corresponding deformation is minimized. Compared with the prior art, this invention improves the current situation where existing models have insufficient fidelity in reproducing the inclined 3D printed concrete process and low prediction accuracy.

Description

Technical Field

[0001] This invention relates to the field of intelligent manufacturing technology, and in particular to a method and system for improving the constructability of inclined 3D printed concrete based on finite element simulation. Background Technology

[0002] 3D printing concrete technology, as an emerging intelligent construction method, boasts the advantage of enabling the free forming of complex geometries, showing great promise in overcoming the constraints of traditional formwork engineering on structural forms. However, in practical engineering applications, when printing complex structures with spatial tilting or cantilever characteristics, the newly deposited concrete material, not yet fully hardened in its early stages, exhibits weak load-bearing and deformation resistance. This leads to structural instability, deformation, and even collapse during the printing process, severely limiting the application of 3D printing concrete technology in complex structural forms. Currently, common approaches to address the stability issues of tilted printing include using temporary or permanent supports, assembling after segmented printing, and optimizing the printing path. However, these methods are often complex and costly, and fail to fundamentally solve the problem of predicting and controlling the mechanical behavior during tilted printing.

[0003] In recent years, the finite element method (FEM) numerical simulation has been introduced into the constructability research of 3D printed concrete to predict structural response and failure behavior during the printing process. Existing models mostly employ a segmented activation strategy to simulate the continuous extrusion and deposition process of materials, achieving a certain level of accuracy in vertical printing scenarios. For example, Chinese patent application CN120387395A provides a CFD-based in-situ 3D printed shield secondary lining constructability optimization method. This method utilizes a CFD-based in-situ 3D printed shield secondary lining method, constructing a co-simulation platform to establish CFD simulation geometry, mesh generation, print path generation, and physical field boundary condition settings. Combined with user-defined functions, it simulates the layer-by-layer stacking of concrete, optimizing construction process parameters. This addresses the problems of excessive trial and error, high cost, and significant safety hazards in existing technologies. This method is mainly suitable for small, simple 3D printed concrete components; however, its computational efficiency limitations make it difficult to simulate the layer-by-layer stacking process at the full structural scale.

[0004] To simulate 3D printed concrete at the full structural scale, existing methods incorporate the finite element method. However, this method generally suffers from insufficient fidelity in replicating the printing process: 1) In actual printing, the moving nozzle provides spatial positioning constraints on the newly extruded material, preventing it from deviating from the preset printing path due to deformation of the underlying structure. Existing models generally ignore the spatial positioning effect of the nozzle on the newly extruded material during segment activation, causing segments to deviate from the printing path during activation, which is significantly different from the actual printing process. 2) Existing finite element models do not fully consider the influence of extrusion pressure during simulated printing: Extrusion pressure has a significant effect on local areas of the structure during material extrusion and deposition, especially in inclined structures, where it can induce additional bending moments, exacerbating the risk of structural instability.

[0005] Therefore, the technical problem that needs to be solved is to provide a method that can accurately simulate the tilted 3D printing process of concrete, integrate the influence of nozzle constraints and extrusion pressure in segmented activation, and support the optimization analysis of process parameters. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a method and system for improving the constructability of inclined 3D printed concrete based on finite element simulation. This improves the current situation where existing models have insufficient reproduction of the inclined 3D printed concrete process and low prediction accuracy, thereby improving the constructability of inclined 3D printed concrete by adjusting the process parameters.

[0007] The objective of this invention can be achieved through the following technical solutions: According to a first aspect of the present invention, a method for improving the constructability of inclined 3D printed concrete based on finite element simulation is provided, the method comprising: S1. Model the tilted 3D printed structure and divide it according to the preset strip size. Then, divide each strip into multiple segments to obtain the initial tilted 3D printed geometric model. S2. Mesh the initial tilted 3D printing geometric model to obtain the target tilted 3D printing model, and construct a set of units and a set of nodes for each segment after meshing. S3. Set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to the segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model. S4. In the initial analysis step, the target tilted 3D printing model is set to an inactive state. Then, in each analysis step, according to the spatial-temporal logic of the preset printing path, the unit set representing each segment and its corresponding nozzle constraint and extrusion pressure are activated segment by segment. An age variable is assigned to the node set of the activated segment, and gravity is applied to the activated part of the target tilted 3D printing model. S5. Calculate the segmented activation process in the finite element calculation software until the tilted 3D printed structure is significantly damaged, and obtain the maximum printable height and corresponding deformation before the damage. S6. Adjust the process parameters. If the initial tilted 3D printing geometry changes, return to execute S1; otherwise, execute S3 until the maximum printable height meets the maximum value and its corresponding deformation meets the minimum value.

[0008] As a preferred technical solution, the material parameters include the parameters of the inclined 3D printed concrete material, which satisfy nonlinearity and time-varying properties; The nonlinearity refers to the yield stress state of the inclined 3D printed concrete material satisfying: ; in, This is the equivalent compressive stress; for The slope of the linear yield surface on the stress plane; It is the cohesive force of the material; The equivalent measure of the deviatoric stress component is given by: ; It is the ratio of triaxial tensile yield stress to triaxial compressive yield stress; Equivalent Mises stress; It is the third invariant of the deviatoric stress tensor; The time-varying nature refers to the evolution of key material parameters in the target tilted 3D printed model as the concrete ages. These key material parameters include the evolution of the material's elastic modulus, compressive strength, stress-strain curve, and Poisson's ratio over time.

[0009] As a preferred technical solution, the bottom boundary condition is determined based on the relative slippage of the strip at the bottom of the target tilted 3D printing model to the printing platform during the actual printing process. If the relative slippage is less than a preset value, the bottom boundary condition is set to rough; otherwise, the bottom boundary condition is set to fixed, that is, the strip at the bottom of the target tilted 3D printing model does not shift.

[0010] As a preferred technical solution, the interface between adjacent strip layers is a surface-to-surface contact model. The surface-to-surface contact model satisfies the normal behavior based on hard contact in the vertical direction, which means that pressure transmission is allowed but penetration is not allowed in the normal direction of the contact; in the tangential direction, it satisfies the tangential behavior based on the penalty method, which means that a friction coefficient of 0.6 is satisfied in the tangential direction of the contact; and the surface-to-surface contact model satisfies that separation is not allowed after contact.

[0011] As a preferred technical solution, each segment is associated with a unique nozzle constraint, which is only effective within the analysis step in which the current segment is activated. The nozzle constraint is as follows: when a segment is activated, a planar displacement constraint is applied to the free end of the newly activated segment, allowing vertical movement; the free end is the end connected to the nozzle in actual printing.

[0012] As a preferred technical solution, the planar displacement constraint is as follows: when the segment is activated, its free end is restricted from displacement in the X and Y directions.

[0013] As a preferred technical solution, the extrusion pressure refers to the equivalent uniformly distributed pressure applied to the lower contact surface of the activated segment during segment activation. Each segment is associated with a unique equivalent uniformly distributed pressure, and the equivalent uniformly distributed pressure is determined to be a multiple of the weight of a strip layer, and it only takes effect when the corresponding segment is activated.

[0014] As a preferred technical solution, the age variable represents the change of the material's time-varying properties with age; and the initial value of the age variable is 0 during segmented activation, and gradually increases with subsequent segmented activation processes.

[0015] As a preferred technical solution, the method for adjusting the process parameters is as follows: Based on the maximum printable height and the corresponding deformation, the starting point and failure mode of structural instability are identified; Based on the aforementioned starting position and failure mode, a parametric analysis is performed, and at least one process parameter is adjusted sequentially based on the analysis results. The process parameters include printing speed, strip height, and tilt angle.

[0016] According to a second aspect of the present invention, a system is provided for implementing the method as described in any one of claims 1 to 9, comprising: The geometric modeling module is used to model the tilted 3D printing structure and divide it according to the preset strip size. Each strip is then evenly divided into multiple segments to obtain the initial tilted 3D printing geometric model. The mesh generation module is used to divide the initial tilted 3D printing geometric model into a mesh to obtain the target tilted 3D printing model, and to build a set of units and a set of nodes for each segment after mesh generation. The parameter setting module is used to set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to the segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model. The segmented activation module is used to activate the set of units representing each segment and its corresponding nozzle constraints and extrusion pressure segment by segment according to the spatial-temporal logic of the preset printing path; and to assign an age variable to the set of nodes of the activated segment, and to apply gravity to the activated part of the target tilted 3D printing model. The finite element calculation module is used to calculate the segmented activation process until the tilted 3D printed structure is significantly damaged, and to obtain the maximum printable height and corresponding deformation before the damage. The parameter optimization module is used to adjust the process parameters until the maximum printable height meets the maximum value and the corresponding deformation meets the minimum value.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention addresses the deficiency of existing models that neglect the spatial positioning effect of the nozzle on the newly extruded material. It introduces dynamic nozzle constraints during the segmented activation process. Specifically, by applying planar displacement constraints to the end connected to the nozzle during segmented activation and allowing it to dynamically migrate with the printing process, the spatial positioning effect of the real nozzle on the extruded material is accurately simulated. This effectively prevents the newly activated segments from deviating from the preset printing path due to deformation of the lower structure, fundamentally ensuring the consistency between the simulated printing process and the actual printing process. It solves the key problem of difficulty in accurately modeling inclined structures due to path offset in numerical simulation.

[0018] 2) To address the issue that existing models do not fully consider the impact of extrusion pressure on the additional bending moment and instability risk of inclined structures, this invention models the extrusion pressure as an equivalent uniformly distributed pressure acting on the contact surface below the newly activated segment. Its magnitude is then parametrically analyzed in relation to the material's self-weight, and it is set to activate with the corresponding segment activation, thus realizing the migration of extrusion pressure. This effectively simulates the movement of the nozzle extrusion action during actual printing, quantifies the characterization of key process loads, and more accurately reflects the real mechanical environment of the material extrusion and deposition stages in inclined printing. This significantly improves the accuracy of predicting the printable height of the structure and the reliability of simulating deformation development before instability and the final failure morphology.

[0019] 3) This invention transforms the complex problem of tilt printing into a calculable and analyzable numerical model, and constructs a closed-loop constructability improvement process. By quantitatively analyzing the maximum printable height and corresponding deformation of the 3D printed model, it can intuitively diagnose the weak links in the design or process parameters. Then, by adjusting key variables such as printing speed, layer height, and tilt angle and resimulating, the optimal combination of process parameters can be quickly selected. This transforms traditional trial-and-error printing into simulation-driven precision process design, which not only provides a high-precision simulation tool, but also significantly reduces experimental costs and improves the success rate and quality of tilted structure construction. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the initial tilted 3D printing geometric model of the present invention; Figure 3 This is a schematic diagram of the mesh division of the present invention; Figure 4 This is a schematic diagram of the simulated printing process of the present invention; Figure 5 The graph shows the results of the constructability optimization of the tilted printing structure of the present invention.

[0021] Reference numerals: 1-Segment; 2-Tilted structure in simulated printing; 3-Connection between the newly activated segment and the previously activated segment; 4-Newly activated segment; 5-Nozzle constraint surface; 6-Extrusion pressure surface. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] To address the problems existing in the prior art, this invention provides a method for improving the constructability of tilted 3D printed concrete based on finite element simulation. By integrating segmented activation strategies, nozzle constraints, and extrusion pressure, it achieves accurate simulation of the continuous construction process of tilted 3D printed concrete. In particular, by incorporating the spatial positioning and local extrusion effects of the printing nozzle on the extruded material into the finite element model, it overcomes the problem of insufficient consideration of the process characteristics of tilted printing in existing simulation methods, effectively improving the prediction accuracy of the model. Specifically, the process is as follows: Figure 1As shown, the process includes establishing a geometric model, mesh generation, setting model parameters, constructing a segmented activation framework, calculating the segmented activation process in finite element analysis software, and optimizing process parameters based on simulation results. Each step is as follows: S1. Model the tilted 3D printing structure and divide it according to the preset strip size. Then, divide each strip into multiple segments to obtain the initial tilted 3D printing geometric model.

[0024] S11. Use 3D modeling software to create an inclined hollow cylinder with an inner diameter of 140mm, an outer diameter of 180mm, a structural height of 200mm, and an inclination angle of 15°.

[0025] S12. Divide the model into 20 independent stripes with a strip width of 40mm and a strip thickness of 10mm. For each stripe, further divide it into m (m=20) segments along its printing path. Figure 2 As shown.

[0026] S13. Number each segment according to the spatiotemporal order of the actual printhead movement, and set the logical order for subsequent segment-by-segment activation.

[0027] S2. Mesh the initial tilted 3D printing geometric model to obtain the target tilted 3D printing model, and construct a set of units and a set of nodes for each segment after meshing.

[0028] S21. Import the initial tilted 3D printing geometric model into the finite element preprocessing software for mesh generation. The mesh type used is hexahedral element C3D8R. 160 elements are used in the perimeter direction of the strips, 6 elements in the width direction, and 2 elements in the thickness direction, resulting in 1920 elements per strip layer. Figure 3 As shown.

[0029] S22. Create a unit set and a node set for each of the 400 segments (20 layers × 20 segments / layer).

[0030] S3. Set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to the segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model.

[0031] Details: 1) Material parameters.

[0032] The material parameters include those for tilted 3D printed concrete, which satisfy both nonlinearity and time-varying properties. The nonlinearity refers to the yield stress state of the tilted 3D printed concrete satisfying the following: ; in, This is the equivalent compressive stress; for The slope of the linear yield surface on the stress plane; It is the cohesive force of the material; The equivalent measure of the deviatoric stress component is given by: ; It is the ratio of triaxial tensile yield stress to triaxial compressive yield stress; Equivalent Mises stress; It is the third invariant of the deviatoric stress tensor.

[0033] Time-varying properties refer to the evolution of key material parameters in the target tilted 3D printed model as the concrete ages. These key material parameters include the evolution of the material's elastic modulus, compressive strength, stress-strain curve, and Poisson's ratio over time. In this embodiment, the material density is set as... Material elastic modulus compressive strength ,in, Indicates time, in minutes; and The unit is kilopascal (kPa).

[0034] In addition, Poisson's ratio is set. Friction angle expansion angle .

[0035] 2) Bottom boundary conditions.

[0036] The bottom boundary condition is determined based on the relative slippage of the strip at the bottom of the target tilted 3D printing model to the printing platform during the actual printing process. If the relative slippage is less than the preset value, the bottom boundary condition is set to rough; otherwise, the bottom boundary condition is set to fixed, that is, the strip at the bottom of the target tilted 3D printing model does not move.

[0037] In this embodiment, the bottom boundary condition is set to fixed, and the preset value is half the width of the printed strip.

[0038] 3) Interfacial zone between adjacent strips.

[0039] The interface between adjacent strip layers is a surface-to-surface contact model. The surface-to-surface contact model satisfies the normal behavior based on hard contact in the vertical direction. The normal behavior based on hard contact means that pressure transmission is allowed but penetration is not allowed in the normal direction of the contact.

[0040] The tangential behavior, based on a penalty method, is satisfied in the tangential direction. This penalty-based tangential behavior refers to a friction model with a friction coefficient of 0.6 in the tangential direction of contact, where gravitational acceleration... Based on the actual local value, take as .

[0041] The surface-to-surface contact model is set to ensure that separation is not allowed after contact.

[0042] 4) Nozzle constraint.

[0043] Each segment is associated with a unique nozzle constraint, which is only effective within the analysis step in which the current segment is active. The nozzle constraint is as follows: when a segment is active, a planar displacement constraint is applied to the free end of the newly active segment (the end connected to the nozzle in actual printing) and vertical movement is allowed.

[0044] Planar displacement constraints are defined as follows: when a segment is activated, its free ends are restricted from displacement in the X and Y directions, which can be expressed as follows: , , These represent displacements in the X and Y directions, respectively.

[0045] Because the nozzle constraint is activated synchronously with the corresponding segment and only takes effect within the analysis step where the current segment is activated, the nozzle constraint migration can be achieved, simulating the movement of the nozzle during the actual printing process.

[0046] 5) Extrusion pressure.

[0047] Extrusion pressure refers to the equivalent uniformly distributed pressure applied to the lower contact surface of the activated segment during segment activation. Each segment is associated with a unique equivalent uniformly distributed pressure, which is determined to be a multiple of the self-weight of one strip. It only takes effect when the corresponding segment is activated, where, Indicates the multiple factor. Indicates the density of the material. Indicates the strip thickness.

[0048] The equivalent uniform pressure is activated synchronously with the activation of the corresponding segment and only takes effect within the analysis step where the current segment is activated. When the next segment is activated, its corresponding equivalent uniform pressure is activated and takes effect, thereby realizing the migration of extrusion pressure and simulating the movement of the nozzle extrusion action in the actual printing process.

[0049] S4. In the initial analysis step, the target tilted 3D printing model is set to an inactive state. Then, in each analysis step, according to the spatial-temporal logic of the preset printing path, the unit set representing each segment and its corresponding nozzle constraint and extrusion pressure are activated segment by segment. Age variables are assigned to the node set of the activated segment, and gravity is applied to the activated part of the target tilted 3D printing model.

[0050] In the initial analysis step, the overall printed structure is set to an inactive state using the "Model Change" module in the finite element software.

[0051] Create 400 dynamic implicit analysis steps to simulate the continuous printing process. The geometric nonlinearity option (NLGEOM=ON) must be enabled for the analysis steps.

[0052] Run the analysis steps continuously. Within each analysis step, perform the following operations on the tilted structure 2 in the simulated printing, according to the segment numbering order set in S1: S41. Activate the unit, changing the current segment's unit set from the "inactive" state to the "activated" state, such as... Figure 4 The newly activated segment 4 is connected to the free end of the previously activated segment, as shown below. Figure 4 3. The connection point between the newly activated segment and the previously activated segment.

[0053] S42. Synchronously activate the nozzle constraint applied to this segment, such as Figure 4 The nozzle constraint surface 5 and the extrusion pressure on the contact surface below this segment, such as Figure 4 The surface under the extrusion pressure is 6.

[0054] S43. Assign time-varying properties to the material. Assign an age variable to the set of segmented nodes. The age variable represents the change of the material’s time-varying properties with age. The initial value of the age variable is 0 when the segment is activated. It gradually increases with subsequent segment activation processes and is calculated based on the printing speed and the length of each strip. In ABAQUS, it is implemented through field variables and represents the age of the material.

[0055] In this embodiment, the strip length is set. for Printing speed for The time to print one strip is: The age variable corresponding to this segment can be calculated using the following formula: .

[0056] S44. Migration Scope: When the analysis step progresses to the next segment activation moment, the nozzle constraints and extrusion pressure of the current segment automatically become invalid, while the nozzle constraints and extrusion pressure corresponding to the newly activated segment automatically become effective. Throughout the analysis process, gravity load is continuously applied to all activated elements. The gravity load here is the product of mass and gravitational acceleration.

[0057] S5. Calculate the segmented activation process in the finite element calculation software until the tilted 3D printed structure is significantly damaged, and obtain the maximum printable height and corresponding deformation before the damage.

[0058] In this embodiment, the calculation fails to converge when the simulated 3D printed structure tilts and is significantly damaged at 15.6 layers. This indicates that under the current parameters ( , Under these conditions, the maximum number of printable layers in the structure is 15.6, the maximum printable height before the simulated printed structure is destroyed is 136.74 mm, and the maximum lateral deformation is 13.2 mm.

[0059] S6. Adjust the process parameters. If the initial tilted 3D printing geometry changes, return to execute S1; otherwise, execute S3 until the maximum printable height meets the maximum value and its corresponding deformation meets the minimum value.

[0060] S61. Based on the maximum printable height and corresponding deformation, identify the starting location and failure mode of structural instability.

[0061] S62. Perform parametric analysis based on the starting position and failure mode, and adjust at least one process parameter sequentially based on the analysis results. The process parameters include printing speed, strip height, and tilt angle. Specifically, for printing speed, the material hardening time can be extended by reducing the printing speed, thereby improving the load-bearing capacity of the printed part; for strip height, the self-weight of the newly activated section and the extrusion pressure can be reduced by decreasing the thickness of a single strip layer, thereby extending the material hardening time of the overall structure; for tilt angle, the tilt angle can be optimized or the internal support structure design can be increased.

[0062] In this embodiment, to optimize the constructability of inclined 3D printed concrete, 1) firstly, the printing speed is optimized. To extend the material hardening time, the printing speed is increased. from Reduce to After re-executing steps S1-S5, the maximum printable height is increased to The maximum lateral deformation decreased to The instability was slightly delayed, proving that reducing the printing speed is beneficial to stability. 2) Further optimize the strip height to fundamentally reduce the weight of each layer and the extrusion pressure. ), to increase the strip thickness from Halved to ,Keep Resimulation showed that the maximum printable height increased significantly to 177.1 mm, and the maximum lateral deformation decreased significantly to 7.84 mm. The corresponding deformation contour plot is shown below. Figure 5 As shown, the overall deformation of the structure is more uniform, with no abrupt changes.

[0063] By optimizing the parameters in the two steps described above, the optimal parameter combination can be obtained. , Compared to the original design, the maximum printable height is increased, and when the same theoretical height is achieved, the deformation of the optimized structure is reduced by about 37%, significantly enhancing its constructability.

[0064] This embodiment demonstrates that evaluating printing results through simulation and making targeted adjustments to process parameters (such as layer height) that affect stability is an effective way to improve the constructability of tilted 3D printing.

[0065] Furthermore, the present invention also provides a system for implementing the above-described method, comprising: The geometric modeling module is used to model the tilted 3D printing structure and divide it according to the preset strip size. Each divided strip is then evenly divided into multiple segments to obtain the initial tilted 3D printing geometric model.

[0066] The mesh generation module is used to generate a target tilted 3D printing model by meshing the initial tilted 3D printing geometric model, and to build a set of cells and nodes for each segment after mesh generation.

[0067] The parameter setting module is used to set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model.

[0068] The segmented activation module is used to activate the set of units representing each segment and its corresponding nozzle constraints and extrusion pressure segment by segment according to the spatial-temporal logic of the preset printing path; and to assign age variables to the node set of the activated segment, and apply gravity to the activated part of the target tilted 3D printing model.

[0069] The finite element calculation module is used to calculate the segmented activation process until the tilted 3D printed structure is significantly damaged, and to obtain the maximum printable height and corresponding deformation before the damage.

[0070] The parameter optimization module is used to adjust process parameters until the maximum printable height meets the maximum value and its corresponding deformation meets the minimum value.

[0071] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the described module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the constructability of inclined 3D printed concrete based on finite element simulation, characterized in that, The method includes: S1. Model the tilted 3D printed structure and divide it according to the preset strip size. Then, divide each strip into multiple segments to obtain the initial tilted 3D printed geometric model. S2. Mesh the initial tilted 3D printing geometric model to obtain the target tilted 3D printing model, and construct a set of units and a set of nodes for each segment after meshing. S3. Set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to the segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model. S4. In the initial analysis step, the target tilted 3D printing model is set to an inactive state. Then, in each analysis step, according to the spatial-temporal logic of the preset printing path, the unit set representing each segment and its corresponding nozzle constraint and extrusion pressure are activated segment by segment. An age variable is assigned to the node set of the activated segment, and gravity is applied to the activated part of the target tilted 3D printing model. S5. Calculate the segmented activation process in the finite element calculation software until the tilted 3D printed structure is significantly damaged, and obtain the maximum printable height and corresponding deformation before the damage. S6. Adjust the process parameters. If the initial tilted 3D printing geometry changes, return to execute S1; otherwise, execute S3 until the maximum printable height meets the maximum value and its corresponding deformation meets the minimum value.

2. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The material parameters mentioned include those for inclined 3D printed concrete materials, which satisfy nonlinearity and time-varying characteristics; The nonlinearity refers to the yield stress state of the inclined 3D printed concrete material satisfying: ； in, This is the equivalent compressive stress; for The slope of the linear yield surface on the stress plane; It is the cohesive force of the material; The equivalent measure of the deviatoric stress component is given by: ； It is the ratio of triaxial tensile yield stress to triaxial compressive yield stress; Equivalent Mises stress; It is the third invariant of the deviatoric stress tensor; The time-varying nature refers to the evolution of key material parameters in the target tilted 3D printed model as the concrete ages. These key material parameters include the evolution of the material's elastic modulus, compressive strength, stress-strain curve, and Poisson's ratio over time.

3. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The bottom boundary condition is determined based on the relative slippage of the strip at the bottom of the target tilted 3D printing model to the printing platform during the actual printing process. If the relative slippage is less than a preset value, the bottom boundary condition is set to rough; otherwise, the bottom boundary condition is set to fixed, that is, the strip at the bottom of the target tilted 3D printing model does not move.

4. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The interface between adjacent strip layers is a surface-to-surface contact model. This surface-to-surface contact model satisfies the normal behavior based on hard contact in the vertical direction, which means that pressure transmission is allowed but penetration is not allowed in the normal direction of the contact. In the tangential direction, it satisfies the tangential behavior based on the penalty method, which means that a friction coefficient of 0.6 is satisfied in the tangential direction of the contact. Furthermore, the surface-to-surface contact model ensures that separation is not allowed after contact.

5. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, Each segment is associated with a unique nozzle constraint, which is only effective within the analysis step in which the current segment is active. The nozzle constraint is as follows: when a segment is activated, a planar displacement constraint is applied to the free end of the newly activated segment, allowing vertical movement; the free end is the end connected to the nozzle in actual printing.

6. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 5, characterized in that, The planar displacement constraint is as follows: when the segment is activated, its free end is restricted from displacement in the X and Y directions.

7. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The extrusion pressure refers to the equivalent uniformly distributed pressure applied to the lower contact surface of the activated segment during segment activation. Each segment is associated with a unique equivalent uniformly distributed pressure, and the equivalent uniformly distributed pressure is determined to be a multiple of the weight of a strip layer, and it only takes effect when the corresponding segment is activated.

8. The method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The age variable represents the change of the material's time-varying properties with age; and the initial value of the age variable is 0 during segmented activation, and gradually increases with subsequent segmented activation processes.

9. A method for improving the constructability of inclined 3D printed concrete based on finite element simulation according to claim 1, characterized in that, The method for adjusting the aforementioned process parameters is as follows: Based on the maximum printable height and the corresponding deformation, the starting point and failure mode of structural instability are identified; Based on the aforementioned starting position and failure mode, a parametric analysis is performed, and at least one process parameter is adjusted sequentially based on the analysis results. The process parameters include printing speed, strip height, and tilt angle.

10. A system, characterized in that, The system is used to implement the method as described in any one of claims 1 to 9, comprising: The geometric modeling module is used to model the tilted 3D printing structure and divide it according to the preset strip size. Each strip is then evenly divided into multiple segments to obtain the initial tilted 3D printing geometric model. The mesh generation module is used to divide the initial tilted 3D printing geometric model into a mesh to obtain the target tilted 3D printing model, and to build a set of units and a set of nodes for each segment after mesh generation. The parameter setting module is used to set the model parameters of the target tilted 3D printing model. The model parameters include material parameters, field variables, bottom boundary conditions, interlayer interfaces between adjacent strips, nozzle constraints applied to the segments, extrusion pressure, and gravity applied to the entire target tilted 3D printing model. The segmented activation module is used to activate the set of units representing each segment and its corresponding nozzle constraints and extrusion pressure segment by segment according to the spatial-temporal logic of the preset printing path; and to assign an age variable to the set of nodes of the activated segment, and to apply gravity to the activated part of the target tilted 3D printing model. The finite element calculation module is used to calculate the segmented activation process until the tilted 3D printed structure is significantly damaged, and to obtain the maximum printable height and corresponding deformation before the damage. The parameter optimization module is used to adjust the process parameters until the maximum printable height meets the maximum value and the corresponding deformation meets the minimum value.

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