3D printing rock-like material similarity optimization method

Abstract

The application discloses a 3D printing rock-like material similarity optimization method. The 3D printing technology is introduced in the preparation of rock-soil engineering rock-like similar materials, which has the advantages of flexibility, high efficiency, short cycle, high precision and good repeatability, and can quickly batch copy rock-like materials with complex defects or internal structures. Based on the similarity principle, the similarity of the 3D printing rock-like material is quantitatively calculated, and the accuracy of the 3D printing rock-like material simulation instead of natural rock is further explored. The similarity quantitative parameters of the rock-like materials with different physical and mechanical properties prepared by different printing schemes are calculated, so that the difference between the rock-like material and the natural rock is more accurately and reliably evaluated, and the best printing scheme of the similar material is quickly determined, and the rapid optimization and regulation of the rock-like material similarity are realized.

Description

Technical Field

[0001] This invention relates to a method for optimizing rock-like materials in the field of indoor rock mechanics testing, specifically a method for optimizing the similarity of 3D printed rock-like materials. Background Technology

[0002] In nature, rock masses develop numerous random defects of varying scales, such as microcracks, pores, joints, bedding planes, faults, and dikes, forming complex rock mass structures. This results in significant heterogeneity, discontinuity, anisotropy, and nonlinear elastic deformation characteristics. Currently, the main research methods for the macroscopic mechanical properties of complex rock masses include theoretical analysis, numerical simulation, and physical simulation experiments. Among these, physical simulation experiments, based on the principle of similarity, use rock-like materials that replicate the structure and properties of the original rock in a certain proportion. This allows for a comprehensive and realistic simulation of the mechanical behavior and interaction between rock masses and engineering structures, making it one of the effective methods to improve the accuracy and repeatability of research on the macroscopic mechanical properties of complex rock masses.

[0003] Traditional physical simulation methods typically involve mixing various aggregates and cementing materials in a specific ratio and sequence, followed by a series of steps including stirring, vibration, tamping, and compaction to create specific rock mass-like materials. This approach has solved the problem of preparing engineering model materials for hydropower station slopes and dams, underground reservoir caverns, underground mining tunnels, and undersea tunnels. However, the traditional physical simulation method suffers from low automation, is time-consuming and labor-intensive, and has a cumbersome process. The resulting similar materials often lack uniformity, accuracy, and repeatability, especially when preparing rock-like materials with complex structures or internal defects. 3D printing technology (additive manufacturing technology) offers advantages such as flexibility, efficiency, short cycle time, high accuracy, and good repeatability, providing a new technological path for the rapid, accurate, and mass production of rock-like materials and solving the challenge of replicating complex rock mass engineering structures.

[0004] Rock-like material similarity is fundamental to the physical simulation of rock mass structures, but current research suffers from two shortcomings. Firstly, most studies on rock-like material similarity are phenomenological and qualitative analyses; whether these materials can simulate and replace natural rocks remains insufficiently demonstrated, and quantitative similarity parameters are lacking. Secondly, common rock-like materials typically only satisfy similarity in a few physical and mechanical parameters within a certain range, exhibiting significant differences from natural rocks in physical properties and mechanical responses. Furthermore, efficient methods for optimizing and controlling the similarity of rock-like materials are lacking. Therefore, there is an urgent need to develop efficient and refined methods for the preparation and optimization of rock-like materials. Summary of the Invention

[0005] To address the problems and needs existing in the background technology, this invention proposes a similarity optimization method for 3D printed rock-like materials. This invention can rapidly, accurately, and in batches replicate rock-like materials whose structure and properties meet similarity requirements, realizing quantitative calculation and optimization control of the similarity of rock-like materials, and providing a reference for physical simulation experimental research on rock mass engineering structures.

[0006] The present invention adopts the following technical solution:

[0007] 1) Design multiple printing schemes based on natural rocks, and use 3D printing methods to obtain several initial types of rock printing materials based on these schemes;

[0008] 2) Determine the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials through indoor experiments, and then establish a database of the correspondence between the printing parameters of several types of current rock printing materials and the basic physical and mechanical parameters;

[0009] 3) Fit the database of correspondence between printing parameters and basic physical and mechanical parameters of several types of rock printing materials to obtain a correlation model of "printing parameters - mechanical parameters";

[0010] 4) Based on the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials, the similarity between natural rocks and several types of current rock printing materials is quantified using a similarity calculation method for similar rock materials, and the similarity quantification parameters of several types of current rock printing materials are obtained.

[0011] 5) After fitting the printing parameters and similarity quantification parameters of several types of rock printing materials to the model, obtain the correlation model of "printing parameters - similarity quantification parameters"; combine the correlation model of "printing parameters - mechanical parameters" and the correlation model of "printing parameters - similarity quantification parameters" to optimize the current printing scheme. If there is an optimal printing scheme, the corresponding rock-like printing material is taken as the final rock-like material. Otherwise, the printing scheme is adjusted and several types of rock printing materials are printed. Then, the correlation models of "printing parameters - mechanical parameters" and "printing parameters - similarity quantification parameters" are updated until the optimal printing scheme is obtained.

[0012] In the first part, when the natural rock is brittle, powder layer nozzle 3D printing technology, stereolithography technology or multi-nozzle inkjet technology are selected; when the natural rock has elastic-plastic characteristics, fused deposition modeling technology or selective laser sintering technology are selected.

[0013] In the second part, the basic physical and mechanical parameters include density, porosity, uniaxial compressive strength, elastic modulus, Poisson's ratio, and shear strength.

[0014] In the above (2), the basic physical and mechanical parameters also include one or more of the following: tensile strength, permeability coefficient, point load strength, sound wave velocity, and energy parameters.

[0015] In section 4), the similarity quantification parameter between natural rocks and several current types of rock printing materials is calculated using the following formula:

[0016]

[0017] Where M represents the difference in the shape and area of ​​the stress-strain curve between natural rock and rock-like printing materials, σ sm For rock-like printing materials, σ pm For the stress of natural rock, C σ The stress similarity scale for rock-like printing materials is given by N, which represents the difference between the dimensionless number of the rock-like printing material and the dimensionless number of natural rock, and P is the number of dimensionless numbers. π′ i Let π be the dimensionless number of the rock-like printing material. i Let be the dimensionless number of the natural rock, and Q represent the similarity quantification parameter between the natural rock and the rock-like printing material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. This invention utilizes 3D printing technology to prepare rock-like materials, offering advantages such as flexibility, high efficiency, short cycle time, high precision, and good repeatability. It can quickly, accurately, and in batches replicate rock-like materials with complex defects or internal structures. It overcomes the disadvantages of existing rock-like material preparation technologies, such as low automation, time-consuming and labor-intensive processes, and cumbersome procedures. The resulting 3D-printed rock-like materials exhibit good uniformity, high precision, and good repeatability, especially in the more refined and accurate simulation of rock defects or structures.

[0020] 2. This invention enables quantitative calculation of the similarity of 3D-printed rock-like materials, further demonstrating the accuracy of 3D-printed rock-like materials in simulating and replacing natural rocks. The similarity quantification of various batches of rock-like materials produced using different printing schemes was calculated, thereby more accurately and reliably assessing the differences between rock-like materials with various physical and mechanical properties and natural rocks.

[0021] 3. This invention enables rapid optimization and control of the similarity between rock-like materials. It replaces the trial-and-error process of physical experiments with a model that establishes the correspondence between 3D printing parameters and similarity, thus significantly saving research costs and time. Simultaneously, it can quickly determine the optimal printing scheme for similar materials, achieving optimized adjustments to various physical and mechanical parameters and mechanical responses of rock-like materials. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a flowchart of the implementation steps of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] like Figure 1 As shown, the present invention includes the following steps:

[0028] 1) Design multiple printing schemes based on natural rocks. Using these schemes, 3D printing methods are employed to obtain initial rock-like printing materials. In practice, appropriate 3D printing processes are selected based on the simulated natural rocks, and suitable experimental design methods are used to initially design the 3D printing schemes. Printing parameters are used as independent variables to determine the category or value range of each parameter. Based on the combinations of different printing parameters, multiple printing schemes are designed to complete the batch preparation of rock-like printing materials.

[0029] 1) When the natural rock is brittle, choose powder layer printhead 3D printing technology (3DP / PP), stereolithography (SLA) technology or multi-nozzle inkjet technology (MJP / PolyJet); when the natural rock has elastic-plastic characteristics, choose fused deposition modeling (FDM) technology or selective laser sintering (SLS) technology.

[0030] Design a printing scheme based on the selected 3D printing process. Different printing processes have slightly different printing parameters, generally including printing materials, curing temperature, and the type and content of additives. Based on the number and range of adjustable printing parameters, select an appropriate experimental design method, such as a full factorial design (when the number of printing parameters is ≤4), an orthogonal design (when the number of printing parameters is >4 and the parameter range is small), or a uniform design (when the number of printing parameters is >4 and the parameter range is large).

[0031] In practice, the geometry of the 3D rock-like printing material and the natural rock sample is designed as a standard cylindrical sample with a diameter of 50 mm and a height of 100 mm, according to the recommendations of the International Society for Rock Mechanics (ISRM). Information on the internal structure of the natural rock is obtained through CT scanning technology, and then a corresponding 3D printing digital model is created and printed.

[0032] 2) Determine the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials through indoor experiments, and then establish a database of the correspondence between the printing parameters of several types of current rock printing materials and the basic physical and mechanical parameters;

[0033] In section 2), the basic physical and mechanical parameters include density, porosity, uniaxial compressive strength, elastic modulus, Poisson's ratio, and shear strength.

[0034] In 2), the basic physical and mechanical parameters also include one or more of the following: tensile strength, permeability coefficient, point load strength, sound wave velocity, and energy parameters.

[0035] The basic physical parameters of the specimen, including density and porosity, can be tested according to the "Test Procedure for Physical and Mechanical Properties of Rocks" (DZ / T 0276-2015). Basic mechanical parameters should include at least uniaxial compressive strength, elastic modulus, Poisson's ratio, and shear strength parameters (cohesion, angle of internal friction). In addition, tensile strength, permeability coefficient, point load strength, acoustic velocity, brittleness index, and energy parameters may also be considered depending on the test conditions. Energy parameters include total strain energy, elastic strain energy, and plastic strain energy. It should be noted that total strain energy is the total input energy of the external load during the uniaxial compression deformation test, and elastic strain energy is the reversible elastic strain energy during the uniaxial compression deformation test. Both total strain energy and elastic strain energy can be obtained by integrating the area enclosed by the stress-strain curve and the horizontal axis; the brittleness index is the ratio of elastic strain energy to total strain energy during the rock loading process.

[0036] In section 2), the methods for obtaining basic mechanical parameters, including uniaxial compression deformation test, triaxial compression strength test, tensile strength test, point load strength test, and acoustic velocity test, can be based on the "Test Procedure for Physical and Mechanical Properties of Rocks" (DZ / T0276-2015). Steady-state / transient seepage tests can be performed according to the "Methods for Determining Permeability Coefficient of Coal and Rock" (MT / T 224-1990).

[0037] 3) Fit the database of correspondence between printing parameters and basic physical and mechanical parameters of several types of rock printing materials to obtain a "printing parameter-mechanical parameter" correlation model, which is used to analyze the correlation between different printing parameters and various mechanical parameters. This correlation model can show the influence law of any printing parameter on a mechanical parameter in the form of a cloud map, and can also show the interactive influence of any two printing parameters on a mechanical parameter.

[0038] 4) Based on the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials, the similarity between natural rocks and several types of current rock printing materials is quantified by using a similarity calculation method for rock-like materials. This method is used to represent the difference between the stress-strain curves obtained by rock-like printing materials and natural rocks in uniaxial compression mechanical tests, and to obtain the similarity quantification parameters of several types of current rock printing materials.

[0039] In section 4), the similarity quantification parameters between natural rocks and several current types of rock printing materials are calculated using the following formula:

[0040]

[0041] Where M represents the difference in the shape and area of ​​the stress-strain curve between natural rock and rock-like printing materials, σ sm For rock-like printing materials, σ pm For the stress of natural rock, C σ The stress similarity scale for rock-like printing materials is given by N, which represents the difference between the dimensionless number of the rock-like printing material and the dimensionless number of natural rock, and P is the number of dimensionless numbers. π′ i Let π be the dimensionless number of the rock-like printing material. i Let M be the dimensionless number of the natural rock, and Q represent the similarity quantification parameter between the natural rock and the rock-like printing material. Q takes into account both the degree of distortion of the stress-strain curve and the dimensionless mechanical parameters. The smaller the values ​​of M, N, and Q, the smaller the difference. If they are equal to 0, it means that the two are completely identical.

[0042] 5) After fitting the printing parameters and similarity quantification parameters of several types of rock printing materials to a model, a correlation model of "printing parameters - similarity quantification parameters" is obtained. This correlation model can display the combined influence or interactive influence of any one or two printing parameters on the similarity quantification parameters in the form of a cloud map. Combining the correlation models of "printing parameters - mechanical parameters" and "printing parameters - similarity quantification parameters", the current printing scheme is optimized. In specific implementation, the optimization steps are as follows: First, the printing schemes are initially screened according to the correlation model of "printing parameters - mechanical parameters", and printing schemes that do not meet the requirements are eliminated. For example, if the model material is required to meet the following requirements: uniaxial compressive strength greater than 7.5 MPa and Poisson's ratio in the range of 0.16 to 0.2, then only printing schemes whose uniaxial compressive strength and Poisson's ratio meet these requirements are retained. Second, according to the correlation model of "printing parameters - similarity quantification parameters", the printing scheme with the smallest similarity quantification parameter among the remaining printing schemes is selected as the optimal scheme. If an optimal printing scheme exists, the corresponding rock-like printing material is used as the final rock-like material. Otherwise, the printing scheme is adjusted and several rock-like printing materials are obtained. The correlation models of "printing parameters-mechanical parameters" and "printing parameters-similarity quantification parameters" are then updated until the optimal printing scheme is obtained.

[0043] Example

[0044] (1) Taking feldspar white sandstone from Sichuan, China as an example, the 3D printing process was selected to prepare rock-like materials. The printing parameters, sand type, additive content, and curing temperature were used as independent variables. The sand types included 70 / 140 mesh sand and 100 / 200 mesh sand. The mass ratio of additives to sand ranged from 1.8:1000 to 2.5:1000, and the curing temperature was 70℃ to 90℃. Since there were three printing parameters, a full factorial design method was used to design the printing scheme. The designed rock-like material printing sample was a standard cylindrical sample with a height of 100mm and a diameter of 50mm. The internal structure information of the white sandstone was obtained by CT scanning technology, and then a 3D printing digital model was established accordingly and the printing sample was prepared.

[0045] (2) Conduct indoor basic physical parameter tests, uniaxial compression deformation tests, and triaxial compression strength tests. Determine the density, porosity, uniaxial compressive strength, elastic modulus, Poisson's ratio, cohesion, and internal friction angle of the rock-like material. Table 1 shows the parameters of the printed sample 3DP-1 with 100 / 200 mesh sand, an additive-to-sand mass ratio of 2.2:1000, and a curing temperature of 80℃.

[0046] Table 1 shows the physical and mechanical parameters of the printed sample 3DP-1.

[0047]

[0048] (3) Obtain a database of the correspondence between printing parameters and mechanical parameters, wherein the printing parameters include the printing sand type, additive content and curing temperature, and the mechanical parameters include uniaxial compressive strength, elastic modulus, Poisson's ratio, cohesion and internal friction angle;

[0049] (4) Using the experimental design analysis software Design-Expert, a model of the correspondence between printing parameters and mechanical parameters of rock-like materials was fitted using the full factorial design method, denoted as the parameter correlation model. The correlation between each printing parameter and each mechanical parameter was analyzed. In this embodiment, with the increase of additive content, the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle of the printed sample all showed an upward trend. With the increase of curing temperature, the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle of the sand sample showed a trend of first increasing and then decreasing.

[0050] (5) A quantitative calculation method for the mechanical similarity of rock materials based on stress-strain relationship was adopted to quantitatively calculate the similarity of rock-like materials, and to obtain the similarity between natural rocks and several types of rock printing materials. The similarity parameters M, N and Q of printed sample 1 were 0.054, 0.564 and 0.567, respectively;

[0051] (6) Using the experimental design analysis software Design-Expert, a model of the correspondence between printing parameters and similarity of rock-like materials was fitted and denoted as the "printing parameters-similarity quantification parameters" correlation model. The trend and correlation of the model were analyzed.

[0052] (7) Optimize the similarity of the printing materials. First, screen the printing schemes and identify those that do not meet the requirements. In this embodiment, the white sandstone-like material is required to have good permeability, and the permeability coefficient of the rock-like material is specified to be within 1×10⁻⁶. -7 m / s and above. Referring to the correlation model of "printing parameters - mechanical parameters", all permeability coefficients below 1×10 were excluded. -7 The printing scheme is m / s. Among the remaining schemes, observe whether there is a minimum value in the correlation model of "printing parameters - similarity quantification parameters" (i.e., there is a minimum similarity quantification parameter). If there is, and the minimum value is not at the boundary of the model, then the printing scheme corresponding to that point is the best printing scheme; otherwise, adjust the range of printing parameters and prepare a new rock-like material, repeat (2)-(7) until the best printing scheme is obtained, and the similarity of the rock-like material is optimized. In this embodiment, the final best printing scheme for the rock-like material is: 70 / 140 mesh sand, the mass ratio of additive to sand is 2.5:1000, and the curing temperature is 81.6℃. The permeability coefficient of the printing material prepared by this scheme is 3×10 -6 m / s, which meets the requirements.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0054] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for optimizing the similarity of 3D printed rock-like materials, characterized in that, Includes the following steps: 1) Design multiple printing schemes based on natural rocks, and use 3D printing methods to obtain several initial types of rock printing materials based on these schemes; 2) Determine the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials through indoor experiments, and then establish a database of the correspondence between the printing parameters of several types of current rock printing materials and the basic physical and mechanical parameters; 3) Fit the database of correspondence between printing parameters and basic physical and mechanical parameters of several types of rock printing materials to obtain a correlation model of "printing parameters - mechanical parameters"; 4) Based on the basic physical and mechanical parameters of natural rocks and several types of current rock printing materials, the similarity between natural rocks and several types of current rock printing materials is quantified using a similarity calculation method for similar rock materials, and the similarity quantification parameters of several types of current rock printing materials are obtained. In section 4), the similarity quantification parameter between natural rocks and several current types of rock printing materials is calculated using the following formula: Where M represents the degree of difference in the shape and area of ​​the stress-strain curve between natural rock and rock-like printing materials. For rock-like printing materials, stress For the stress of natural rocks, The stress similarity scale for rock-like printing materials is given by N, where N represents the degree of difference between the dimensionless number of the rock-like printing material and the dimensionless number of natural rock, and P is the number of dimensionless numbers. Let i be the dimensionless number of the rock-like printing material. Let be the dimensionless number of the natural rock, and Q represent the similarity quantification parameter between the natural rock and the rock-like printing material; 5) After fitting the printing parameters and similarity quantification parameters of several types of rock printing materials to the model, obtain the "printing parameter-similarity quantification parameter" correlation model; combine the "printing parameter-mechanical parameter" correlation model and the "printing parameter-similarity quantification parameter" correlation model to optimize the current printing scheme. If there is an optimal printing scheme, the corresponding rock-like printing material is taken as the final rock-like material. Otherwise, the printing scheme is adjusted and several types of rock printing materials are printed. Then, the "printing parameter-mechanical parameter" correlation model and the "printing parameter-similarity quantification parameter" correlation model are updated until the optimal printing scheme is obtained.

2. The method for optimizing the similarity of 3D printed rock-like materials according to claim 1, characterized in that, In the first part, when the natural rock is brittle, powder layer nozzle 3D printing technology, stereolithography technology or multi-nozzle inkjet technology are selected; when the natural rock has elastic-plastic characteristics, fused deposition modeling technology or selective laser sintering technology are selected.

3. The method for optimizing the similarity of 3D printed rock-like materials according to claim 1, characterized in that, In the second part, the basic physical and mechanical parameters include density, porosity, uniaxial compressive strength, elastic modulus, Poisson's ratio, and shear strength.

4. The method for optimizing the similarity of 3D printed rock-like materials according to claim 1, characterized in that, In the above (2), the basic physical and mechanical parameters also include one or more of the following: tensile strength, permeability coefficient, point load strength, sound wave velocity, and energy parameters.

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