A lightweight structure design and forming method using laser selective melting

Abstract

The present invention relates to the technical field of laser selective melting, and specifically to a laser selective melting forming lightweight structure design and forming method, including: S1, analyzing the working condition characteristics and functional characteristics of parts; S2, simulating the load capacity of various lattice structures, and testing the maximum stress value under the same load and boundary conditions; S3, simulating and analyzing the flow capacity of various lattice structures, comprehensively analyzing the load capacity and flow capacity, and selecting a specific lattice structure as the basic unit cell of lattice lightweight for subsequent design of parts; S4, analyzing the influence of the structural parameters of the basic unit cell on the strength; S5, overall structural design of lattice lightweight parts; S6, laser selective melting forming process design of unit cell structure; S7, laser selective melting forming verification of lattice lightweight parts. The lightweight design of the structure is realized, the use of materials is reduced, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of laser selective melting, and in particular to a laser selective melting forming lightweight structure design and forming method. Background Art

[0002] Radiators are important and basic components in hot water (or steam) heating systems. Hot water cools down in the radiator (or steam condenses in the radiator) and supplies heat to the room to achieve the purpose of heating. The metal consumption and cost of radiators account for a considerable proportion in the heating system. Therefore, the correct selection of radiators involves the economic indicators and operating effects of the system.

[0003] With the increasing demand for lightweight and high-strength materials in industrial manufacturing, traditional manufacturing methods can no longer meet the manufacturing requirements of complex structural parts. As an advanced additive manufacturing technology, laser selective melting technology can produce parts with complex internal structures, but its application in lightweight design still needs further research and development. Summary of the invention

[0004] Therefore, the present invention provides a laser selective melting forming lightweight structure design and forming method.

[0005] In order to solve the above technical problems, the present invention provides a laser selective melting forming lightweight structure design and forming method, including: S1, analyzing the working characteristics and functional features of parts; S2, simulating the load capacity of various lattice structures, and testing the maximum stress value under the same load and boundary conditions; S3, simulating and analyzing the flow capacity of various lattice structures, comprehensively analyzing the load-bearing capacity and flow capacity, and selecting a specific lattice structure as the basic unit cell for lattice lightweighting for subsequent design of parts; S4, analyzing the influence of the structural parameters of the basic unit cell on the strength; S5, overall structural design of lattice lightweight parts; S6, laser selective melting forming process design of unit cell structure; S7, laser selective melting forming verification of lattice lightweight parts.

[0006] Further, in step S1, pyramidal, hexahedral, and eggshell cell structures are selected for analysis.

[0007] Further, step S1 includes: S11, discretizing the unit cell into a finite number of units, and establishing a unit stiffness matrix based on the constitutive relationship of the material, the elastic modulus is 110 GPa, the Poisson's ratio is 0.34; S12, applying a specific load, applying a load of 10 MPa in three directions on the node sphere, and obtaining the node displacement by solving the equilibrium equation; S13, calculating the unit stress based on the geometric equation and the physical equation, and determining the maximum stress value in the unit cell, and repeating the above calculation process when the diameter of the load-bearing column changes, and observing the changing trend of the maximum stress.

[0008] Furthermore, in step S2, finite element strength analysis was performed on the pyramid-type, hexahedral, and eggshell-type unit cell structures respectively through simulation. By taking three orthogonal faces as symmetry planes and applying a three-dimensional load of 10 MPa on each node sphere, the bearing capacity of different lattices was obtained.

[0009] Further, in step S3, the lattice structure is regarded as a porous medium, and according to Darcy's law Q=-K*A*(ΔP / L), where: Q is the flow rate, K is the permeability, A is the cross-sectional area, ΔP is the pressure difference, and L is the flow path length, the pressure loss is calculated by simulating the flow of the working fluid in the lattice.

[0010] Furthermore, in step S3, during the simulation process, the physical properties and boundary conditions of the working fluid are set, and simulations are performed under the same boundary conditions for different lattice structures to obtain pressure loss data and compare flow capacities.

[0011] Further, in step S4, under the same load conditions, the smaller the volume of the unit cell, the smaller the maximum stress of the unit cell and the stronger the bearing capacity; when the unit cell is a square, the bearing capacity of the unit cell is the strongest; when the diameter of the bearing sphere is equal to twice the diameter of the bearing cylinder, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases; when the characteristic size of the cube unit cell is equal to twice the diameter of the bearing sphere, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases.

[0012] Further, in step S5, the unit cell of the lattice lightweight structure is selected as a pyramid unit cell, the unit cell is a cube structure, the side length is 4 mm, the bearing ball diameter is 2 mm, and the bearing column diameter is 1 mm; the structure of the selected unit cell is modeled and analyzed, and the solid volume of the unit cell is determined to be 184m 3 , the space volume is 64m 3 , a single unit cell can reduce weight by 71.25%.

[0013] Furthermore, in step S6, the laser selective melting forming process of titanium alloy powder is verified by characterizing microstructure, density and mechanical properties tests, so as to determine the key process parameters affecting the quality of laser selective melting forming of titanium alloy, and finally select the best laser selective melting forming process parameters.

[0014] Furthermore, in step S7, the forming process verification is carried out through laser selective melting of the heat sink frame parts. Through the main steps of three-dimensional model processing, laser selective melting, stress relief annealing, wire cutting, sandblasting, and mechanical processing, the overall processing of the parts is completed, realizing the laser selective melting process verification.

[0015] The technical solution of the present invention has the following advantages:

[0016] The laser selective melting forming lightweight structure design and forming method provided by the present invention includes: S1, analyzing the working conditions and functional characteristics of parts; S2, simulating the load capacity of various lattice structures, and testing the maximum stress value under the same load and boundary conditions; S3, simulating and analyzing the flow capacity of various lattice structures, comprehensively analyzing the load-bearing capacity and flow capacity, and selecting a specific lattice structure as the basic unit cell of lattice lightweight for subsequent design of parts; S4, analyzing the influence of the structural parameters of the basic unit cell on the strength; S5, overall structural design of lattice lightweight parts; S6, laser selective melting forming process design of unit cell structure; S7, laser selective melting forming verification of lattice lightweight parts.

[0017] The laser selective melting forming lightweight structure design and forming method realizes the lightweight design of the structure, reduces the use of materials, and reduces the manufacturing cost. At the same time, through the laser selective melting forming technology, it is possible to manufacture lightweight parts with complex internal structures while ensuring the strength and functional requirements of the parts, which has important engineering application value and meets the strength and functional performance of the parts.

[0018] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the disclosure, nor is it intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart of the design and forming method of a lightweight structure formed by laser selective melting provided by the present invention;

[0021] Figure 2 A schematic structural diagram of a pyramid-shaped unit cell structure of a lightweight structure design and forming method for selective laser melting provided by the present invention;

[0022] Figure 3 A schematic structural diagram of a hexahedral unit cell structure of a laser selective melting forming lightweight structure design and forming method provided by the present invention;

[0023] Figure 4A structural schematic diagram of an eggshell-shaped unit cell structure of the laser selective melting lightweight structure design and forming method provided by the present invention. DETAILED DESCRIPTION

[0024] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0025] In the description of the present disclosure, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0026] In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0027] In the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0028] The disclosure below provides many different embodiments or examples to realize different structures of the present disclosure. In order to simplify the disclosure of the present disclosure, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present disclosure. In addition, the present disclosure can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present disclosure provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0029] The preferred embodiments of the present disclosure are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0030] See also Figures 1 to 4 As shown, the present invention provides a laser selective melting forming lightweight structure design and forming method, including: S1, analyzing the working conditions and functional characteristics of parts; S2, simulating the load capacity of various lattice structures, and testing the maximum stress value under the same load and boundary conditions; S3, simulating and analyzing the flow capacity of various lattice structures, comprehensively analyzing the load-bearing capacity and flow capacity, and selecting a specific lattice structure as the basic unit cell of lattice lightweight for subsequent design of parts; S4, analyzing the influence of the structural parameters of the basic unit cell on the strength; S5, overall structural design of lattice lightweight parts; S6, laser selective melting forming process design of unit cell structure; S7, laser selective melting forming verification of lattice lightweight parts.

[0031] The radiator frame parts are lightweight for the purpose of weight reduction, but they still need a certain strength to ensure the use of the parts. As a heat exchange product, a certain flow area in the unit cell must be guaranteed to enhance the heat exchange effect. Therefore, in step S1, pyramidal, hexahedral and eggshell unit cell structures are initially selected for analysis.

[0032] When analyzing the influence of basic unit cell structure parameters on strength, for a given unit cell structure, its stress calculation is based on the finite element analysis method. Step S1 includes: S11, discretizing the unit cell into a finite number of units, and establishing a unit stiffness matrix based on the constitutive relationship of the material, with an elastic modulus of 110GPa and a Poisson's ratio of 0.34; S12, applying a specific load, applying a load of 10MPa in three directions on the node sphere, and obtaining the node displacement by solving the equilibrium equation; S13, calculating the unit stress based on the geometric equation and the physical equation, and determining the maximum stress value in the unit cell, repeating the above calculation process when the diameter of the load-bearing cylinder changes, and observing the change trend of the maximum stress.

[0033] In step S2, after selecting the pyramid, hexahedron and eggshell cell structures, finite element strength analysis was performed on the pyramid, hexahedron and eggshell cell structures respectively through simulation. By taking three orthogonal faces as symmetry planes and applying a three-dimensional load of 10 MPa on each node sphere, the bearing capacity of different lattices was obtained.

[0034] Under the same load and boundary conditions, the maximum stress of the pyramidal cell lattice is 61.55MPa, the maximum stress of the hexahedral cell lattice is 133.86MPa, and the maximum stress of the eggshell cell lattice, which is a combination of the two, is 41.6MPa. It can be seen that in terms of bearing capacity, the eggshell cell lattice > pyramid cell lattice > hexahedral cell lattice.

[0035] For the flow capacity analysis of the lattice, the computational fluid dynamics (CFD) method is used. In step S3, the lattice structure is regarded as a porous medium. According to Darcy's law Q = -K*A*(ΔP / L), where Q is the flow rate, K is the permeability, A is the cross-sectional area, ΔP is the pressure difference, and L is the flow path length, the pressure loss is calculated by simulating the flow of the working fluid in the lattice. During the simulation process, the physical properties and boundary conditions of the working fluid are set. For different lattice structures, simulations are performed under the same boundary conditions to obtain pressure loss data and compare the flow capacity.

[0036] Among them, the physical properties are set as water, and the density is about 1000kg / m 3 , viscosity is about 0.001Pa·s, boundary conditions, such as inlet velocity, outlet pressure, etc.

[0037] The periodic cellular lattice structure needs to be completely immersed in the phase change working fluid. The fluidity of the working fluid in the lattice also has a certain influence on the heat transfer effect. A unidirectional flow analysis is performed on the lattice.

[0038] Under the same boundary conditions, the pressure loss of the pyramidal cell lattice is 44.6 KPa, the maximum stress of the hexahedral cell lattice is 9.6 KPa, and the maximum stress of the eggshell cell lattice, which is a combination of the two, is 71.5 KPa. It can be seen that in terms of flow capacity, the eggshell cell lattice < the pyramid cell lattice < the hexahedral cell lattice.

[0039] Based on the above analysis of load-bearing capacity and flow capacity, the pyramid-shaped cellular lattice with relatively strong load-bearing capacity and flow capacity is selected as the basic crystal package of the lattice lightweight parts for subsequent design.

[0040] The pyramid-shaped cell lattice is a hexahedral structure, mainly including a body-centered spherical carrier, spherical carriers on eight orthogonal planes, and supporting columns between the body-centered spherical carriers and the eight intersection spherical carriers. Its parameterized structure can be characterized by: the diameter of the supporting sphere, the diameter of the supporting column, the lattice length, the lattice width, and the lattice height.

[0041] As the diameter of the supporting column increases, the maximum stress in the unit cell gradually decreases, and when the diameter of the supporting column is equal to half the diameter of the supporting sphere, the change trend of the maximum stress in the unit cell slows down significantly; at the same time, as the unit cell approaches a cube, the maximum stress in the unit cell gradually decreases.

[0042] As the diameter of the bearing cylinder increases, the overall change trend of the maximum stress in the unit cell is gradually increasing. The reason for this is that as the ratio of the diameter of the bearing sphere to the diameter of the bearing cylinder gradually increases, the radius of curvature near the boundary between the two gradually decreases, making it easier to produce stress concentration. This law is the same as the change trend of the maximum stress of the unit cell under different bearing cylinder diameter conditions. On the other hand, given that a pressure load is applied to the force-bearing surface of the unit cell, as the bearing sphere increases, the external force on the unit cell increases rapidly, but the maximum stress of the unit cell does not change much, especially when the bearing sphere diameter is 4mm and 5mm, the maximum stress corresponding to the bearing sphere is almost the same, indicating that when the bearing sphere diameter is 5mm, which is half the characteristic size of the unit cell, the bearing capacity of the unit cell is relatively good. At the same time, as the lattice unit gradually deviates from the cube, the angular direction of the bearing cylinder changes, and the interface between the bearing cylinder and the bearing sphere gradually distorts, which will lead to more obvious stress concentration.

[0043] On the premise that the structure of the load-bearing sphere and the load-bearing column remains unchanged, as the unit cell gradually deviates from the cube, the maximum stress in the unit cell gradually increases due to the gradual decrease in the characteristic dimensions of the load-bearing sphere and the load-bearing column relative to the lattice volume. However, as the lattice structure gradually approaches a small square, the maximum stress in the lattice still gradually increases with the increase in the lattice volume, but the rate of change of the maximum stress significantly decreases.

[0044] As the unit cell volume gradually increases, the characteristic dimensions of the load-bearing spheres and load-bearing columns gradually become smaller relative to the lattice volume, resulting in the overall increase in the maximum stress in the unit cell. When the unit cell width reaches the geometric mean of the unit cell length and the unit cell height, the unit cell deviates from the square to the greatest extent, and the stress of the unit cell also reaches the maximum. As the unit cell width continues to increase, the unit cell structure approaches the square, and the maximum stress in the unit cell decreases. However, under the action of volume, the maximum stress continues to increase.

[0045] Based on the above analysis, the following conclusions can be drawn: under the same load conditions, the smaller the volume of the unit cell, the smaller the maximum stress of the unit cell and the stronger the bearing capacity; when the unit cell is a square, the unit cell has the strongest bearing capacity; when the diameter of the bearing sphere is equal to twice the diameter of the bearing cylinder, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases; when the characteristic size of the cube unit cell is equal to twice the diameter of the bearing sphere, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases.

[0046] In step S5, according to the overall design requirements of the parts, in order to maximize the comprehensive performance of the parts, the parts are lightweight designed while ensuring the overall structural strength.

[0047] The unit cell of the selected lattice lightweight structure is a pyramid unit cell, which is a cubic structure with a side length of 4mm, a load-bearing ball diameter of 2mm, and a load-bearing column diameter of 1mm. The structure of the selected unit cell is modeled and analyzed, and the solid volume of the unit cell is determined to be 184m 3 , the space volume is 64m 3 , a single unit cell can reduce weight by 71.25%. The final mounting base can reduce weight by 33.94%. At the same time, the three space areas within the frame surrounded by the mounting base with a lattice structure can realize the circulation and diffusion of the working fluid because the two main beams are lattice porous structures.

[0048] In step S6, the laser selective melting forming process of titanium alloy powder is verified by characterizing microstructure, density and mechanical properties tests, the key process parameters affecting the quality of laser selective melting forming of titanium alloy are determined, and finally the optimal laser selective melting forming process parameters are selected.

[0049] The process parameters include laser power, scanning speed, scanning spacing, layer thickness and other process parameters. Through the optimization of process parameters, precise control of the microstructure and mechanical properties of titanium alloy parts is achieved, and the forming accuracy and surface quality of the parts are improved.

[0050] The forming process is verified by electron beam selective melting of the heat sink frame parts. The overall processing of the parts is completed through main processes such as 3D model processing, electron beam powder rapid forming, powder-part separation, sandblasting, and mechanical processing, realizing the verification of electron beam selective melting forming.

[0051] In step S7, the forming process verification is carried out through laser selective melting of the heat sink frame parts. Through the main steps of three-dimensional model processing, laser selective melting, stress relief annealing, wire cutting, sandblasting, and mechanical processing, the overall processing of the parts is completed, realizing the laser selective melting process verification.

[0052] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A laser selective melting forming lightweight structure design and forming method, characterized in that: include: S1. Analyze the working conditions and functional characteristics of parts; S2. Simulate the load capacity of various lattice structures and test the maximum stress value under the same load and boundary conditions; S3. Conduct flow capacity simulation analysis on various lattice structures, conduct comprehensive load-bearing capacity and flow capacity analysis, and select a specific lattice structure as the basic unit cell for lattice lightweighting for subsequent design of parts; S4. Analyze the influence of structural parameters of basic unit cell on strength; S5. Overall structural design of lattice lightweight parts; S6. Design of laser selective melting forming process for unit cell structure; S7. Verification of laser selective melting forming of lattice lightweight parts.

2. A laser selective melting lightweight structure design and forming method according to claim 1, characterized in that: In step S1, pyramidal, hexahedral, and eggshell cell structures are selected for analysis.

3. A laser selective melting lightweight structure design and forming method according to claim 2, characterized in that: Step S1 includes: S11. Discretize the unit cell into a finite number of units. According to the constitutive relationship of the material, the elastic modulus is 110 GPa, the Poisson's ratio is 0.34, and the unit stiffness matrix is ​​established; S12. Under the condition of applying a specific load and applying a load of 10 MPa in three directions on the node sphere, the node displacement is obtained by solving the equilibrium equation; S13. Calculate the unit stress according to the geometric equation and the physical equation, and determine the maximum stress value in the unit cell. When the diameter of the load-bearing column changes, repeat the above calculation process and observe the change trend of the maximum stress.

4. A laser selective melting lightweight structure design and forming method according to claim 3, characterized in that: In step S2, finite element strength analysis is performed on the pyramid-type, hexahedral, and eggshell-type unit cell structures respectively through simulation. By taking three orthogonal faces as symmetry planes and applying a three-dimensional load of 10 MPa on each node sphere, the bearing capacity of different lattices is obtained.

5. A laser selective melting lightweight structure design and forming method according to any one of claims 1 to 4, characterized in that: In step S3, the lattice structure is regarded as a porous medium, and according to Darcy's law Q=-K*A*(ΔP / L), where: Q is the flow rate, K is the permeability, A is the cross-sectional area, ΔP is the pressure difference, and L is the flow path length, the pressure loss is calculated by simulating the flow of the working fluid in the lattice.

6. A laser selective melting lightweight structure design and forming method according to claim 5, characterized in that: In step S3, during the simulation process, the physical properties and boundary conditions of the working fluid are set, and simulations are performed under the same boundary conditions for different lattice structures to obtain pressure loss data and compare flow capacities.

7. A laser selective melting lightweight structure design and forming method according to claim 6, characterized in that: In step S4, under the same load conditions, the smaller the volume of the unit cell, the smaller the maximum stress of the unit cell and the stronger the bearing capacity; when the unit cell is a square, the bearing capacity of the unit cell is the strongest; when the diameter of the bearing sphere is equal to twice the diameter of the bearing cylinder, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases; when the characteristic size of the cube unit cell is equal to twice the diameter of the bearing sphere, the comprehensive mechanical properties of the unit cell are optimal, and the maximum stress does not change much as the ratio decreases.

8. The method for designing and forming a lightweight structure by selective laser melting according to claim 7, characterized in that: In step S5, the unit cell of the lattice lightweight structure is selected as a pyramid unit cell, the unit cell is a cube structure, the side length is 4 mm, the bearing ball diameter is 2 mm, and the bearing column diameter is 1 mm; the structure of the selected unit cell is modeled and analyzed, and the solid volume of the unit cell is determined to be 184m 3 , the space volume is 64m 3 , a single unit cell can reduce weight by 71.25%.

9. The method for designing and forming a lightweight structure by selective laser melting according to claim 1, characterized in that: In step S6, the laser selective melting forming process of titanium alloy powder is verified by characterizing microstructure, density and mechanical properties tests, the key process parameters affecting the quality of laser selective melting forming of titanium alloy are determined, and finally the optimal laser selective melting forming process parameters are selected.

10. The method for designing and forming a lightweight structure by selective laser melting according to claim 1, characterized in that: In step S7, the forming process verification is carried out through laser selective melting of the heat sink frame parts. Through the main steps of three-dimensional model processing, laser selective melting, stress relief annealing, wire cutting, sandblasting, and mechanical processing, the overall processing of the parts is completed, realizing the laser selective melting process verification.

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