Laser powder bed composite powder spreading simulation analysis model construction method and system

Abstract

The invention discloses a laser powder bed composite powder spreading simulation analysis model construction method and system, and relates to the technical field of metal additive manufacturing computer numerical simulation. Comprising the following steps: acquiring surface profile data of a formed test piece and reconstructing surface topography; measuring and calibrating physical contact parameters between the composite powder; constructing a spreading model considering the surface topography and the action between the powders; the spreading behavior of the composite powder is verified and analyzed through experiments. According to the method, contour scanning, point cloud data denoising and filtering and surface three-dimensional reconstruction are carried out on the surface of a formed sample, a substrate model with the same appearance as the real surface of the formed sample is constructed, then a corresponding powder laying platform is constructed based on discrete element software, and the physical characteristics of composite powder are comprehensively considered; and a high-fidelity composite powder spreading dynamics simulation model is established. A substrate model with a more real deposition surface is established, and the powder deposition phenomenon in the laser powder bed melting forming process can be more truly represented.

Description

Technical Field

[0001] The present invention relates to the technical field of computer numerical simulation of metal additive manufacturing, and in particular to a method and system for constructing a simulation analysis model of laser powder bed composite powder spreading. Background Art

[0002] Laser powder bed fusion (LPBF) technology is a special rapid prototyping and 3D printing technology. It usually uses metal, ceramic and polymer materials to manufacture near-net-shape and good surface quality parts. This technology has been proven to produce parts with a relative density of up to 99.9%, and is widely used in aerospace, automobile manufacturing and other fields. LPBF technology uses a laser beam to selectively melt and fuse powders in and between layers based on the idea of ​​layered superposition to build parts. Factors such as powder layer thickness, scanning speed, and roughness of the powder surface will cause different powder quality, directly affecting the interaction between the laser and particles or adhesives, and thus have a key impact on the quality of the final parts. Generally speaking, the surface of the part formed by 3D printing is not a smooth plane. The powder quality on the formed surface is affected by factors such as the surface roughness of the specimen, resulting in different powder quality on a smooth substrate. In order to better study the actual powder spreading situation, it is often necessary to undergo multiple rounds of printing experiments and combine them with equipment such as high-speed cameras for research, but it takes a lot of time and materials. Therefore, many studies have begun to focus on the numerical simulation technology of the LPBF powder spreading process.

[0003] In order to intuitively analyze the impact of powder spreading quality on formed specimens, researchers can usually first simulate the powder spreading process through finite element software, and then analyze the powder bed quality and particle movement data after powder spreading. For a long time, many scholars at home and abroad have conducted extensive research on the powder spreading behavior in the LPBF process, but most of them are based on smooth substrates with flat surfaces for powder spreading simulation. The obtained spreading characteristics are often quite different from the powder spreading effect in real printing conditions. It is difficult to establish an effective mapping relationship between powder spreading parameters, powder spreading quality and metallurgical defects, and it is even more difficult to achieve accurate prediction of powder spreading quality. At the same time, the currently constructed powder spreading model is mainly oriented to the spreading of single-component powders, and does not consider or less considers the powder spreading complexity brought by multiple powder components, which is difficult to meet the needs of multi-material forming. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is how to achieve accurate prediction of the actual surface powder spreading quality of the printed specimen.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In the first aspect, an embodiment of the present invention provides a method for constructing a laser powder bed composite powder spreading simulation analysis model, which includes obtaining surface contour data of a formed specimen and reconstructing the surface morphology; measuring and calibrating the physical contact parameters between composite powders; constructing a spreading model that takes into account the surface morphology and the interaction between powders; and verifying and analyzing the spreading behavior of the composite powder through experiments.

[0008] As a preferred scheme for the method of constructing a laser powder bed composite powder spreading simulation analysis model of the present invention, wherein: obtaining surface contour data includes obtaining point cloud data through three-dimensional scanning, denoising and filtering the point cloud data, and reconstructing the processed data into a three-dimensional surface model.

[0009] As a preferred scheme for the method of constructing a laser powder bed composite powder spreading simulation analysis model of the present invention, the physical contact parameters include: the static friction coefficient between the composite powder particles; the dynamic friction coefficient between the composite powder particles; the surface energy between the composite powder particles; and the friction coefficient between the particles and the reconstructed surface.

[0010] As a preferred scheme for the method of constructing a laser powder bed composite powder spreading simulation analysis model of the present invention, constructing a spreading model includes building a model including a scraper, a powder supply area and a powder spreading area, setting the physical parameters and contact parameters of the powder, including the static friction coefficient and the normal contact force; defining the scraper motion parameters and boundary conditions.

[0011] As a preferred scheme for the method of constructing a simulation analysis model of laser powder bed composite powder spreading of the present invention, the analysis of spreading behavior includes evaluating the powder bed packing density and powder height change, analyzing the motion trajectory and speed of composite powder particles, and comparing the dynamic repose angles of simulated and experimental powder beds.

[0012] As a preferred solution of the method for constructing a simulation analysis model for the spreading of composite powders in a laser powder bed of the present invention, the method for measuring the static friction coefficient includes adhering particles to a glass slide and stacking them face to face; adjusting the tilt arm until the upper layer slides; and calculating the static friction coefficient based on the tilt angle;

[0013] The surface energy is measured by the sessile drop method, including using ultrapure deionized water and glycerol as test liquids; measuring the contact angle between the liquid and the particles; considering the effect of surface roughness based on the Wenzel model; and calculating the surface energy value according to Young's equation.

[0014] As a preferred solution of the method for constructing a simulation analysis model of laser powder bed composite powder spreading of the present invention, the calculation method of the normal contact force includes:

[0015] The normal contact force between particles is expressed as:

[0016]

[0017] In the simulation, the particle Young's modulus is set three orders of magnitude lower than the actual Young's modulus (which reduces the simulation time and has little effect on the simulation results), and the surface energy between particles is corrected accordingly according to the following criteria:

[0018]

[0019] Where γ is the surface energy between powder particles, E is the equivalent Young's modulus of the particles, DEM and exp are the data of simulation settings and experimental measurements, respectively;

[0020] According to the powder SEM morphology, single-sphere and multi-sphere models were used for the composite powders, respectively. The high-entropy alloy was set as a single-sphere model with a diameter of 15 to 53 μm. The diamond particles were approximated with a three-sphere model to simulate the polygonal structure so that its equivalent diameter was 20 μm.

[0021] In a second aspect, an embodiment of the present invention provides a laser powder bed composite powder spreading simulation analysis model construction system, which includes a surface reconstruction module, a parameter measurement module, a model construction module and a verification analysis module;

[0022] The surface reconstruction module is used to obtain the three-dimensional scanning data of the surface of the formed specimen, and process and reconstruct the data to obtain the surface morphology;

[0023] The parameter measurement module is used to measure the physical contact parameters such as static friction coefficient and surface energy between composite powders, and perform parameter calibration;

[0024] The model building module is used to establish a spreading model that takes into account the surface morphology and the interaction between powders, and to set the corresponding physical parameters and boundary conditions;

[0025] The verification and analysis module is used to perform powder laying simulation calculations, obtain powder bed quality characteristic parameters, and verify the accuracy of the model through experimental comparison.

[0026] In a third aspect, an embodiment of the present invention provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, the steps of the method for constructing a laser powder bed composite powder spreading simulation analysis model as in the first aspect of the present invention are implemented.

[0027] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of the method for constructing a laser powder bed composite powder spreading simulation analysis model as in the first aspect of the present invention are implemented.

[0028] The beneficial effects of the present invention are as follows: the present invention proposes a method and system for constructing a simulation analysis model for the spreading of composite powders in a laser powder bed. First, the surface of the formed sample is subjected to contour scanning, point cloud data denoising and filtering, and surface three-dimensional reconstruction to construct a substrate model with the same surface morphology as the formed sample. Subsequently, a corresponding powder spreading platform is built based on discrete element software, and the physical properties of the composite powder (morphological characteristics, friction coefficient, repose coefficient, surface energy, etc.) are comprehensively considered to establish a high-fidelity composite powder spreading dynamics simulation model. Compared with the traditional powder spreading model based on a smooth flat plate and a single ball setting, the present invention establishes a substrate model with a more realistic deposition surface, which can more realistically reproduce the powder deposition phenomenon in the laser powder bed melting forming process, and also provides a practical idea and technical path for the subsequent study of continuous multi-layer deposition powder spreading behavior; on the other hand, the present invention is further oriented to composite powders with a mixture of multiple materials, comprehensively considering the interaction parameters and morphological differences between different powders, and providing an effective model for the study of the powder spreading behavior of multi-phase materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 The overall flow chart of the composite powder spreading model construction based on the forming surface reconstruction is provided for the method and system for constructing the simulation analysis model of composite powder spreading in laser powder bed;

[0031] Figure 2 A method and system for building a simulation analysis model for composite powder spreading in a laser powder bed, using point cloud data to reconstruct a three-dimensional model of the surface in Comsol;

[0032] Figure 3 The three-dimensional model diagram of the powder spreading device is used for the simulation analysis model construction method and system of laser powder bed composite powder spreading;

[0033] Figure 4 The construction method of the simulation analysis model for the laser powder bed composite powder spreading and the measurement mechanism diagram of the static friction coefficient between particles of the system;

[0034] Figure 5 , Figure 6 This is a graph showing the construction method of the laser powder bed composite powder spreading simulation analysis model and the particle surface energy measurement experiment of the system;

[0035] Figure 7A method and system for building a simulation analysis model for composite powder spreading in a laser powder bed; Axial and longitudinal velocity distribution diagrams obtained by tracing the composite powder particles on a reconstructed surface and a smooth substrate;

[0036] Figure 8 A method and system for constructing a simulation analysis model for laser powder bed composite powder spreading, including the powder bed particle distribution map obtained by powder spreading simulation on a reconstructed surface and a smooth substrate, and the powder bed morphology map obtained by the actual powder spreading experiment. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0040] Example 1

[0041] Reference Figures 1 to 8 , which is the first embodiment of the present invention, provides a method for constructing a simulation analysis model for spreading composite powders in a laser powder bed, comprising:

[0042] S1, obtaining the surface profile data of the formed specimen and reconstructing the surface morphology;

[0043] In one embodiment, the surface of a laser powder bed fusion formed specimen is scanned by a three-dimensional contour scanner to obtain point cloud data of the surface contour; the point cloud data is denoised, filtered, and reduced to obtain a streamlined point cloud data set; the processed point cloud data set is surface constructed in Comsol software to obtain a reconstructed surface with the same surface morphology as the actual specimen, and then fine meshing is performed in Comsol to export the surface in STL file format.

[0044] Furthermore, the obtaining of surface contour data includes obtaining point cloud data through three-dimensional scanning, performing denoising and filtering processing on the point cloud data, and reconstructing the processed data into a three-dimensional surface model.

[0045] S2, measuring and calibrating the physical contact parameters between composite powders;

[0046] In one embodiment, a scraper, a powder supply area, and a powder spreading area model are constructed in the EDEM software, wherein the powder spreading area is composed of a reconstructed rough surface and a smooth surface, and post-processing analysis is performed on the reconstructed surface; the static friction coefficient between the composite powder particles and between the particles and the reconstructed surface is obtained by a static friction angle experiment; wherein the static friction angle experiment is to glue the particles to a glass slide by glue, and then stack the two groups of glass slides with particles face to face and place them on an adjustable tilt arm, and gradually adjust the tilt arm upward so that the upper glass slide begins to slide downward, and the tilt angle at this time is recorded, and the corresponding static friction coefficient is calculated based on the angle; the surface energy between the composite powder particles is measured by the sessile drop method, and considering that the existence of the rough surface has an effect on the solid-liquid contact surface, the Wenzel model is adopted to correct the calculated value;

[0047] The sessile drop method is based on Young's equation, and the surface energy is calculated by measuring the contact angle between the liquid and the particles through a contact angle meter. The Young's equation is expressed as follows:

[0048] γ sl =γ s -γ l ·cosθ

[0049] Among them, γ s and γ l are the surface energies of the solid and liquid, γ sl is the interface surface energy between the solid and the liquid, and θ is the contact angle. According to the OWRK model, the surface energy is the nonpolar part (γ d ) and the polar part (γ p ), this definition can handle the unknown variable γ in Young's equation sl The mathematical expression of the OWRK model is as follows: To determine γ s p and γ s d , at least two liquids with known polar and non-polar parts are needed, and then the adhesion work and solid surface energy can be calculated based on these data. The liquids used in the present invention are ultrapure deionized water and glycerol, and their preferred droplet volumes are 8μl and 4μl respectively.

[0050] Since the rolling friction coefficient of micro-sized particles is difficult to quantify experimentally, the rolling friction coefficient and repose coefficient between particles are calibrated by the angle of repose experiment.

[0051] Furthermore, the physical contact parameters include the static friction coefficient between the composite powder particles; the dynamic friction coefficient between the composite powder particles; the surface energy between the composite powder particles; and the friction coefficient between the particles and the reconstructed surface.

[0052] In one embodiment,

[0053] S3, constructing a spreading model that takes into account the surface morphology and the interaction between powders;

[0054] Import the 3D model of the reconstructed surface and scraper, and build the powder spreading model in EDEM: including the scraper, reconstructed surface, front and back substrates, and particle factory;

[0055] In one embodiment, according to the powder particle shape obtained by SEM, the composite powder is modeled using single-sphere and multi-sphere particle models respectively to make it similar to the electron microscope photo morphology, and then the particle size and position are randomly generated based on a random function;

[0056] The material parameters of the composite powder are defined in EDEM, including the physical parameters of the powder particles (density, Young's modulus, Poisson's ratio) and contact parameters (friction coefficient, coefficient of repose and surface energy between particles and between particles and the reconstructed surface). The influence of van der Waals force on particle motion is considered between particles. The normal contact force between particles is expressed as:

[0057]

[0058] In the simulation, the particle Young's modulus is set three orders of magnitude lower than the actual Young's modulus (which reduces the simulation time and has little effect on the simulation results), and the surface energy between particles is corrected accordingly according to the following criteria:

[0059]

[0060] Where γ is the surface energy between powder particles, E is the equivalent Young's modulus of the particles, DEM and exp are the data of simulation settings and experimental measurements, respectively;

[0061] The distance between the scraper and the smooth part of the substrate in the powder spreading model is set, the scraper performs translational motion, and the corresponding motion parameters are set; periodic boundary conditions are set for the particles so that the particles are constrained along the Y axis, and the particles exceeding the boundary are automatically deleted; the total simulation time, time step, data saving time interval, grid division and number of CPUs used are set.

[0062] Furthermore, the construction of the spreading model includes building a model including a scraper, a powder supply area and a powder spreading area, setting the physical parameters and contact parameters of the powder, including the static friction coefficient and the normal contact force; and defining the scraper motion parameters and boundary conditions.

[0063] S4, experimentally verify and analyze the spreading behavior of composite powders;

[0064] In one embodiment, EDEM is started to perform powder spreading simulation, and the same powder spreading experiment is carried out on a 3D printing device. The dynamic angle of repose of the powder in the simulation process is compared with the angle of repose obtained in the experimental process to determine the correctness of the model; the packing density of the powder bed deposited on the reconstructed surface, the height change of the powder, the coordination number, shear force, mass flow, and the tracked motion trajectories of different particles in the composite powder, the relationship curve between the average velocity and time, etc. are systematically evaluated to reveal the dynamic behavior of the actual forming sample surface during the powder spreading process.

[0065] Furthermore, the analysis of spreading behavior includes evaluating the packing density of the powder bed and the change in powder height, analyzing the motion trajectory and speed of the composite powder particles, and comparing the dynamic repose angle of the powder bed between simulation and experiment.

[0066] Furthermore, this embodiment also provides a laser powder bed composite powder spreading simulation analysis model construction system, including:

[0067] Surface reconstruction module, parameter measurement module, model building module and verification analysis module;

[0068] The surface reconstruction module is used to obtain three-dimensional scanning data of the surface of the formed specimen, and process and reconstruct the data to obtain the surface morphology;

[0069] The parameter measurement module is used to measure the physical contact parameters such as static friction coefficient and surface energy between composite powders, and perform parameter calibration;

[0070] The model building module is used to establish a spreading model that takes into account the surface morphology and the interaction between powders, and to set corresponding physical parameters and boundary conditions;

[0071] The verification and analysis module is used to perform powder laying simulation calculations, obtain powder bed quality characteristic parameters, and verify the accuracy of the model through experimental comparison.

[0072] This embodiment also provides a computer device, which is suitable for the case of a method for constructing a laser powder bed composite powder spreading simulation analysis model, and includes a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the method for constructing a laser powder bed composite powder spreading simulation analysis model as proposed in the above embodiment.

[0073] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0074] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for constructing a simulation analysis model for laser powder bed composite powder spreading proposed in the above embodiment is implemented.

[0075] In summary, the present invention proposes a method and system for constructing a simulation analysis model for the spreading of composite powders in a laser powder bed. First, the surface of the formed sample is subjected to contour scanning, point cloud data denoising and filtering, and surface three-dimensional reconstruction to construct a substrate model with the same surface morphology as the formed sample. Then, the corresponding powder spreading platform is built based on discrete element software, and the physical properties of the composite powder (morphological characteristics, friction coefficient, repose coefficient, surface energy, etc.) are comprehensively considered to establish a high-fidelity composite powder spreading dynamics simulation model. Compared with the traditional powder spreading model based on a smooth flat plate and a single ball setting, the present invention establishes a substrate model with a more realistic deposition surface, which can more realistically reproduce the powder deposition phenomenon in the laser powder bed melting forming process, and also provides a practical idea and technical path for the subsequent study of continuous multi-layer deposition powder spreading behavior; on the other hand, the present invention is further oriented to composite powders with a mixture of multiple materials, and comprehensively considers the interaction parameters and morphological differences between different powders, providing an effective model for the study of the powder spreading behavior of multi-phase materials.

[0076] Example 2

[0077] Reference Figure 2 to Figure 6 , which is the second embodiment of the present invention, provides a method for constructing a simulation analysis model for spreading composite powders in a laser powder bed, and provides a detailed implementation method and a specific operation process, including:

[0078] Use a 3D scanning profiler to obtain the surface profile point cloud data of the specimen and perform data processing;

[0079] Figure 2 The obtained point cloud data is used to reconstruct the specimen surface using Comsol software, the reconstructed surface model is finely meshed, and the STL model file is exported;

[0080] Figure 3 A 3D printing powder spreading model was built in EDEM, including a scraper, a powder supply area and a powder spreading area. The powder spreading area consisted of a reconstructed surface and a smooth substrate, and the post-processing area was mainly aimed at the quality of the powder bed on the reconstructed surface.

[0081] The static friction between the powder particles and the reconstructed surface was experimentally measured ( Figure 4 ), it can be obtained that the coefficient of kinetic friction between high entropy alloy powders is 0.462, between diamond particles is 0.606, between high entropy alloy and diamond is 0.499, between high entropy alloy and reconstructed surface is 0.414, and between diamond and reconstructed surface is 0.482. Since the dynamic friction between particles is difficult to measure, the dynamic friction coefficient between powder particles can be further determined by EDEM repose angle experiment, which can be obtained that the coefficient of kinetic friction between high entropy alloy powders is 0.02, between diamond particles is 0.08, and between high entropy alloy and diamond is 0.04;

[0082] A composite powder particle processing plant was established. According to the powder SEM morphology, the high entropy alloy powder particles have good sphericity, so they are set as a single-ball model with a diameter of 15 to 53 μm. Diamond particles are mostly hexagonal and octagonal, so a three-ball model is used to approximate the polygonal structure, making its equivalent diameter 20 μm.

[0083] Figure 5 and Figure 6 The surface energy between powder particles and between particles and substrate was measured by sessile drop method. In the simulation, Young's modulus was reduced by three orders of magnitude, so the corresponding surface energy measured experimentally was also corrected according to specific criteria, namely 0.52mJ / m2 between high entropy alloy powders, 0.68mJ / m2 between diamond particles, and 0.56mJ / m2 between high entropy alloy and diamond.

[0084] Set the motion parameters of the scraper in the powder spreading model and the distance between the scraper and the substrate. The motion parameters of the scraper include translation speed, translation direction and movement time, which are 10 mm / s, from left to right ( Figure 3 ) and 0.488s; the distance between the scraper and the substrate was set to 30μm;

[0085] The simulation model to be simulated by EDEM was started, and the dynamic repose angle of the model after simulation was compared with the dynamic repose angle obtained from the corresponding experiment. The results showed that the dynamic repose angles formed by the experiment and simulation were 26.9° and 27.1°, respectively, which were basically consistent. The morphology of the powder pile was also basically similar, verifying the reliability of the model.

[0086] Example 3

[0087] Reference Figure 7-Figure 8 , which is the second embodiment of the present invention, provides a method for constructing a simulation analysis model for spreading of composite powders in a laser powder bed. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0088] The prior art usually simulates the powder spreading on a smooth substrate and uses the Hertz-Mindlin with JKR contact model to restore the contact relationship between particles. In order to verify the advantages of the present invention, the control variable method is used to simulate the powder spreading on the reconstructed surface and the smooth substrate under the same conditions. Particle tracking shows that the motion trajectory of the composite powder particles on the smooth substrate is relatively regular, but there is a large deviation from the actual powder spreading process.

[0089] Compared with the embodiment of the powder spreading simulation on the reconstructed surface, the present invention constructs a comparative example of the powder spreading simulation on the smooth substrate, and the Hertz-Mindlin with JKR contact model is used between the particles to restore the contact relationship between the material particles in the actual powder spreading process as much as possible; and the control variable method is used to perform powder spreading simulation on the smooth substrate and the reconstructed surface respectively, and the horizontal and vertical speeds of the composite powder particles on the powder bed are recorded ( Figure 7 ), we can see that the movement trajectories of the particles show significant differences.

[0090] In addition, in order to verify the accuracy of powder spreading on the reconstructed surface and on the smooth substrate, actual powder spreading experiments were further carried out to obtain the corresponding powder bed morphology and quality. Figure 8 In order to compare the particle distribution of powder beds obtained by spreading powder on two different substrates with the experimental data, it is found that the powder bed quality and defects obtained by simulating the powder spreading on the reconstructed surface are more consistent with the actual powder bed quality. The powder bed quality obtained by the traditional simulation of spreading powder on a smooth substrate has a large error compared with the actual powder bed quality. Therefore, the discrete element model analysis based on forming surface reconstruction proposed in the present invention has higher fidelity and more accurate prediction of powder bed quality.

[0091] The specific differences are:

[0092] Velocity distribution: The velocity distribution of powder particles in the horizontal and vertical directions on the smooth substrate is uniform, lacking the local fluctuation characteristics in the actual powder spreading process;

[0093] Deposition state: The powder bed surface simulated by the smooth substrate has a high flatness and fails to reflect the local defects of the actual powder bed;

[0094] Particle distribution: The particle distribution on a smooth substrate tends to be idealized, and it is difficult to reflect the particle size segregation phenomenon in actual powder spreading.

[0095] The technical effects of the present invention are as follows: high fidelity, the reconstructed surface model takes into account the actual surface morphology characteristics, so that the simulation results are closer to experimental observations; accurate prediction, verified by comparative experiments, the powder bed quality deviation predicted by the model of the present invention is less than 5%, while the deviation of the traditional smooth substrate model can reach more than 20%; defect reproduction, can accurately simulate and predict defects such as pores and segregation in the powder bed, and provide a basis for process optimization; strong universality, the method is suitable for composite powder systems with different particle size distributions, and has wide application value.

[0096] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for constructing a simulation analysis model for laser powder bed composite powder spreading, characterized in that: include, Obtaining the surface profile data of the formed specimen and reconstructing the surface morphology; Measure and calibrate physical contact parameters between composite powders; Construct a spreading model that takes into account surface morphology and interactions between powders; The spreading behavior of composite powders was verified and analyzed through experiments.

2. The method for constructing a laser powder bed composite powder spreading simulation analysis model according to claim 1, characterized in that: The obtaining of the surface contour data includes obtaining point cloud data through three-dimensional scanning, performing denoising and filtering processing on the point cloud data, and reconstructing the processed data into a three-dimensional surface model.

3. The method for constructing a simulation analysis model for laser powder bed composite powder spreading according to claim 2, characterized in that: The physical contact parameters include: static friction coefficient between composite powder particles; dynamic friction coefficient between composite powder particles; surface energy between composite powder particles; and friction coefficient between particles and the reconstructed surface.

4. The method for constructing a laser powder bed composite powder spreading simulation analysis model according to claim 3, characterized in that: The construction of the spreading model includes building a model including a scraper, a powder supply area and a powder spreading area, setting the physical parameters and contact parameters of the powder, including the static friction coefficient and the normal contact force; and defining the scraper motion parameters and boundary conditions.

5. The method for constructing a laser powder bed composite powder spreading simulation analysis model according to claim 4, characterized in that: The analysis of spreading behavior includes evaluating the packing density of the powder bed and the change in powder height, analyzing the movement trajectory and speed of the composite powder particles, and comparing the dynamic repose angle of the powder bed between simulation and experiment.

6. The method for constructing a laser powder bed composite powder spreading simulation analysis model according to claim 5, characterized in that: The method for measuring the static friction coefficient includes adhering particles to a glass slide and stacking them face to face; adjusting the tilt arm until the upper layer slides; Calculate the coefficient of static friction based on the tilt angle; The surface energy is measured by the sessile drop method, including using ultrapure deionized water and glycerol as test liquids; measuring the contact angle between the liquid and the particles; considering the effect of surface roughness based on the Wenzel model; and calculating the surface energy value according to Young's equation.

7. The method for constructing a laser powder bed composite powder spreading simulation analysis model according to claim 6, characterized in that: The calculation method of the normal contact force includes: The normal contact force between particles is expressed as: In the simulation, the particle Young's modulus is set three orders of magnitude lower than the actual Young's modulus (which reduces the simulation time and has little effect on the simulation results), and the surface energy between particles is corrected accordingly according to the following criteria: Where γ is the surface energy between powder particles, E is the equivalent Young's modulus of the particles, DEM and exp are the data of simulation settings and experimental measurements, respectively; According to the powder SEM morphology, single-sphere and multi-sphere models were used for the composite powders, respectively. The high-entropy alloy was set as a single-sphere model with a diameter of 15 to 53 μm. The diamond particles were approximated with a three-sphere model to simulate the polygonal structure so that its equivalent diameter was 20 μm.

8. A laser powder bed composite powder spreading simulation analysis model construction system, based on the laser powder bed composite powder spreading simulation analysis model construction method according to any one of claims 1 to 7, characterized in that: It also includes a surface reconstruction module, a parameter measurement module, a model building module and a verification analysis module; The surface reconstruction module is used to obtain three-dimensional scanning data of the surface of the formed specimen, and process and reconstruct the data to obtain the surface morphology; The parameter measurement module is used to measure the physical contact parameters such as static friction coefficient and surface energy between composite powders, and perform parameter calibration; The model building module is used to establish a spreading model that takes into account the surface morphology and the interaction between powders, and to set corresponding physical parameters and boundary conditions; The verification and analysis module is used to perform powder laying simulation calculations, obtain powder bed quality characteristic parameters, and verify the accuracy of the model through experimental comparison.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for constructing a laser powder bed composite powder spreading simulation analysis model according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for constructing a laser powder bed composite powder spreading simulation analysis model according to any one of claims 1 to 7 are implemented.

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