Discontinuous dot matrix supporting structure design method for inhibiting thermal deformation of additive manufacturing

Abstract

The invention relates to the technical field of metal additive manufacturing, in particular to a discontinuous dot matrix supporting structure design method for restraining additive manufacturing thermal deformation, and the method comprises the steps that a missile wing discontinuous dot matrix filling area is determined, and the design density of the filling area and the appearance precision index of missile wing additive manufacturing are determined; determining an L-D curve of the unit cell size and the unit cell diameter of the filling area; constructing a three-dimensional geometric model of the missile wing structure on the basis of an L-D curve, performing additive manufacturing thermal deformation analysis, and determining a spacing interval of a body-centered cubic dot matrix by combining the difference between the maximum deformation of the feature points on the outer surface of the missile wing and the appearance precision index of the additive manufacturing of the missile wing; and obtaining the optimal discontinuous spacing according to the spacing interval of the body-centered cubic dot matrix. Through the size design and the spacing design of the discontinuous dot matrix structure, the discontinuous dot matrix supporting structure meeting the missile wing appearance precision requirement and the lightweight requirement is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of metal additive manufacturing, and in particular to a method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing. Background Art

[0002] Additive manufacturing technology brings greater freedom to the design of missile wing structures. However, in the additive manufacturing process, the shrinkage of the molten pool caused by the laser heat source melting the material and the uneven temperature field lead to deformations such as dents and cracks on the outer surface of the structural parts, affecting the surface accuracy. For small missile wings with large aspect ratios, the thin skin area is large, and the deformation problem caused by thermal stress is particularly prominent.

[0003] At present, from a design perspective, the main way to suppress thermal stress deformation in additive manufacturing is to add support structures, which have two structural forms: external support and internal support. Since the external support needs to be removed after manufacturing, it will cause material waste, so adding internal support structures becomes an effective way to suppress deformation. The internal support structure of the wing is arranged too compactly and does not meet the requirements of lightweight structure design; if it is arranged too sparsely, it cannot effectively suppress the thermal stress deformation of the thin skin. Therefore, a reasonable design of the internal support structure is the key to ensuring the shape accuracy of the thin-walled structural parts of the wing and achieving lightweight structure. Summary of the invention

[0004] In order to solve the above technical problems, the present invention mainly aims at the thermal deformation problem caused by thermal stress in the additive manufacturing process of the thin skin of the missile wing, and provides a design method for a non-continuous lattice support structure to suppress the thermal deformation of additive manufacturing. The load-bearing structure design of the missile wing has been completed in the early stage through design means such as topology optimization. On this basis, the non-continuous lattice structure size design and spacing design are used to obtain a non-continuous lattice support structure that meets the requirements of missile wing shape accuracy and lightweight requirements.

[0005] The first object of the present invention is to provide a method for designing a discontinuous lattice support structure for suppressing thermal deformation of additive manufacturing, which is used to optimize the support structure inside the wing, comprising:

[0006] Determine the non-continuous lattice filling area of ​​the wing, and determine the design density of the filling area and the shape accuracy index of the wing additive manufacturing;

[0007] Based on the body-centered cubic lattice type, according to the design density of the filling area, an equal-density design is adopted to determine the LD curve of the unit cell size and unit cell diameter of the filling area;

[0008] Based on the LD curve, a three-dimensional geometric model of the wing structure is constructed to perform thermal deformation analysis of additive manufacturing. The spacing range of the body-centered cubic lattice is determined by combining the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing.

[0009] The optimal discontinuous spacing is obtained based on the spacing interval of the body-centered cubic lattice.

[0010] Preferably, the LD curve of the unit cell size and the unit cell diameter of the filling area is determined according to the following steps:

[0011] Get the unit cell density based on body-centered cubic lattice type;

[0012] The equal-density design is adopted, and the unit cell density is used as the design density of the filling area to obtain the diameter of the minimum size and the diameter of the maximum size of the lattice unit cell;

[0013] Based on the height of the filled area, determine the minimum and maximum sizes of the lattice unit cell;

[0014] According to the minimum size and maximum size of the lattice unit cell, and the diameter of the lattice unit cell at the minimum size and the diameter of the lattice unit cell at the maximum size, the LD curve of the unit cell size and the unit cell diameter of the filling area is obtained.

[0015] Preferably, after determining the LD curve of the unit cell size and the unit cell diameter of the filling area, the method further includes:

[0016] When the spacing of the body-centered cubic lattice is equal to zero, a three-dimensional geometric model of the missile wing structure filled with the body-centered cubic lattice is established, and the thermal deformation simulation of the additive manufacturing process is carried out to extract the maximum deformation of the characteristic points on the outer surface of the missile wing;

[0017] Whether the spacing is optimized is determined based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing.

[0018] Preferably, the optimal discontinuous spacing is obtained by using the golden section method based on the spacing interval of the body-centered cubic lattice.

[0019] Preferably, the design density of the filling area refers to the ratio of the maximum mass allowed by the discontinuous lattice support structure to the volume of the filling area;

[0020] The shape accuracy index of the missile wing additive manufacturing refers to the deviation of the actual shape of the missile wing relative to the theoretical shape after additive manufacturing by applying a non-continuous dot matrix to the missile wing structure.

[0021] The second object of the present invention is to provide a discontinuous lattice support structure design system for suppressing thermal deformation of additive manufacturing, characterized in that it includes:

[0022] A data determination module is used to determine the non-continuous lattice filling area of ​​the missile wing, and determine the design density of the filling area and the shape accuracy index of the missile wing additive manufacturing;

[0023] The curve fitting module is used to determine the LD curve of the unit cell size and unit cell diameter of the filling area based on the body-centered cubic lattice type and the design density of the filling area by adopting equal density design;

[0024] The spacing optimization module is used to construct a three-dimensional geometric model of the wing structure based on the LD curve, perform thermal deformation analysis of additive manufacturing, and determine the spacing interval of the body-centered cubic lattice based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing; and obtain the optimal discontinuous spacing based on the spacing interval of the body-centered cubic lattice.

[0025] The third object of the present invention is to provide an electronic device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the steps of the above method are implemented when the computer program is executed by the processor.

[0026] A fourth object of the present invention is to provide a storage medium having a computer program stored thereon, which is used to execute the steps of the above method when the computer program is executed.

[0027] The present invention has at least the following beneficial effects:

[0028] The present invention provides a method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing. The method determines the optimal discontinuous spacing of the lattice through an optimization algorithm, and can ensure the shape accuracy of the structural parts while meeting the requirements of lightweight structure design. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Design a flow chart for the non-continuous lattice support structure of the missile wing;

[0030] Figure 2 It is the non-continuous dot-matrix filling area of ​​the wing (gray area);

[0031] Figure 3 are the main characteristic parameters of the BCC lattice unit cell structure;

[0032] Figure 4 is the relationship between unit cell size and diameter;

[0033] Figure 5 It is a non-continuous dot spacing diagram;

[0034] Figure 6 Schematic diagram of thermal deformation at characteristic points on the wing surface. DETAILED DESCRIPTION

[0035] In order to illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description in conjunction with embodiments.

[0036] The present invention aims at the problem of thermal deformation caused by thermal stress in the additive manufacturing process of the thin skin of the wing, and provides a method for optimizing the design of a discontinuous lattice support structure that suppresses thermal deformation. The load-bearing structure design of the wing has been completed in the early stage through design methods such as topological optimization. On this basis, the discontinuous lattice structure size design and spacing design are used to obtain a discontinuous lattice support structure that meets the requirements of wing shape accuracy and lightweight.

[0037] In order to achieve the above object, the present invention provides a method for designing a discontinuous lattice support structure for suppressing thermal deformation of additive manufacturing, which is used to optimize the support structure inside the wing, comprising:

[0038] S1. Determine the non-continuous lattice filling area of ​​the wing, and determine the design density of the filling area and the shape accuracy index of the wing additive manufacturing;

[0039] The design density of the filling area refers to the ratio of the maximum mass allowed by the discontinuous lattice support structure to the volume of the filling area;

[0040] The shape accuracy index of the missile wing additive manufacturing refers to the deviation of the actual shape of the missile wing relative to the theoretical shape after additive manufacturing by applying a non-continuous dot matrix to the missile wing structure.

[0041] For example, the determination of the discontinuous lattice filling area Ω is based on the completion of the main load-bearing structure of the wing in the early stage. The wing already has a clear force transmission path, and the area of ​​the skin without the support of the reinforcement ribs is the discontinuous lattice filling area Ω. According to the overall design index requirements, the design density ρ of the filling area and the shape accuracy index δ of the additive manufacturing of the wing are clarified. Among them, the design density requirement ρ refers to the ratio of the maximum mass allowed by the discontinuous lattice support structure to the volume of the filling area; the shape accuracy requirement δ refers to the deviation of the actual shape of the wing relative to the theoretical shape after the non-continuous lattice is applied to the wing structure and additive manufacturing.

[0042] S2. Based on the body-centered cubic lattice type and the design density of the filling area, an equal-density design is adopted to determine the LD curve of the unit cell size and the unit cell diameter of the filling area;

[0043] The LD curve of the unit cell size and unit cell diameter of the filling area is determined according to the following steps:

[0044] Get the unit cell density based on body-centered cubic lattice type;

[0045] The equal-density design is adopted, and the unit cell density is used as the design density of the filling area to obtain the diameter of the minimum size and the diameter of the maximum size of the lattice unit cell;

[0046] Based on the height of the filled area, determine the minimum and maximum sizes of the lattice unit cell;

[0047] According to the minimum size and maximum size of the lattice unit cell, and the diameter of the lattice unit cell at the minimum size and the diameter of the lattice unit cell at the maximum size, the LD curve of the unit cell size and the unit cell diameter of the filling area is obtained.

[0048] For example, based on the design density of the filling area, * According to the requirements, equal density design is adopted to determine the unit cell diameter D of the filling area; the specific implementation process is as follows:

[0049] S2.1 Select the body-centered cubic (BCC) lattice structure with the lightest weight, good bending resistance and stability. The characteristic parameters of the BCC lattice unit cell include: unit cell size L and rod diameter D. The angle θ between the rod and the additive manufacturing substrate is 45°, which meets the manufacturability.

[0050] Therefore, the unit cell density ρ is the ratio of the total mass M of the BCC lattice unit cell to the unit cell volume V, written as:

[0051]

[0052] Among them, ρ M The density of the raw material for additive manufacturing.

[0053] S2.2 Based on the height of the filled area, the minimum size L of the lattice unit cell can be determined min and maximum size L max . Based on the design density of the filling area ρ * The requirement is to adopt equal density design, that is, ρ = ρ * , determine the minimum diameter D of the lattice unit cell min and the maximum diameter D max . In (L min ,L max ) interval, according to formula (1), the LD curve of unit cell size and unit cell diameter is obtained;

[0054] After determining the LD curve of the unit cell size and unit cell diameter of the filling area, it also includes:

[0055] When the spacing of the body-centered cubic lattice is equal to zero, a three-dimensional geometric model of the missile wing structure filled with the body-centered cubic lattice is established, and the thermal deformation simulation of the additive manufacturing process is carried out to extract the maximum deformation of the characteristic points on the outer surface of the missile wing;

[0056] Whether the spacing is optimized is determined based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing.

[0057] For example, when the spacing a = 0 mm, a three-dimensional geometric model of the wing structure filled with body-centered cubic BCC lattice is established, and the thermal deformation simulation of the additive manufacturing process is performed using the commercial software Simufact Additive. The maximum deformation δ of the characteristic points on the outer surface of the wing is extracted. If δ ≥ δ *, the optimization is exited, indicating that the design density ρ * index is too harsh; if δ < δ *, it indicates that there is room for optimization of the spacing a. The specific optimization process is as follows.

[0058] S3. Construct a three-dimensional geometric model of the wing structure based on the LD curve, conduct thermal deformation analysis of additive manufacturing, and determine the spacing range of the body-centered cubic lattice based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing;

[0059] The optimal discontinuous spacing is obtained based on the spacing interval of the body-centered cubic lattice.

[0060] The optimal discontinuous spacing is obtained by using the golden section method based on the spacing interval of the body-centered cubic lattice.

[0061] Exemplarily, when the maximum deformation of the characteristic points on the outer surface of the wing is less than the shape accuracy index of the wing additive manufacturing, the spacing is determined for optimization to obtain the spacing interval of the body-centered cubic lattice, specifically including:

[0062] The advance and retreat method is used to reconstruct the 3D geometric model of the wing structure based on the LD curve to simulate the thermal deformation of the additive manufacturing process. The maximum deformation δ of the characteristic points on the outer surface of the wing is compared with the shape accuracy index δ * If δ<δ*, increase the spacing a; if δ>δ*, reduce the spacing a; if δ=δ*, get the boundary value of a, and keep searching to get the interval of spacing a (a min , a max );

[0063] The interval of spacing a is determined (a min , a max ) based on the golden section method to determine the optimal discontinuous spacing a opt .

[0064] In order to further illustrate a method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing provided by the present invention, it is described in conjunction with the accompanying drawings.

[0065] See also Figure 1 As shown, a method for designing a discontinuous lattice support structure for suppressing thermal deformation of additive manufacturing comprises:

[0066] S1. Determine the non-continuous lattice filling area of ​​the wing and clarify the design density ρ of the filling area * and the shape accuracy index δ of missile wing additive manufacturing* . Determine the wing fill area as Figure 2 Medium gray area, design density ρ of the filled area * ≤0.15g / cm 3 , the outer surface accuracy of the wing after additive manufacturing is δ * ≤0.5mm;

[0067] S2. Select the body-centered cubic BCC lattice type. The schematic diagram of the BCC lattice structure is as follows Figure 3 As shown, based on the height of the filled area, the diameter D of the minimum size of the lattice unit cell is determined min and the maximum diameter D max And the LD curve of unit cell size and unit cell diameter. The specific process is as follows:

[0068] S2.1 Additive manufacturing raw materials use AlSi 10 Mg, according to formula (1), the expression of lattice unit cell density ρ is obtained;

[0069] S2.2 Obtain the minimum size L of the unit cell based on the wing filling area min =4mm, maximum dimension L max =14mm, and then D min =0.4mm, D max =1.4mm. The LD curve of unit cell size and unit cell diameter is as follows Figure 4 shown.

[0070] S3. Reconstruct the 3D geometric model of the wing structure based on the LD curve. The unit cell spacing a is as follows Figure 5 As shown. The thermal deformation simulation of the additive manufacturing process was performed using Simufact Additive software. The advance and retreat method was used, the step length h = 1mm, the magnification factor γ = 1, and the interval of spacing a (5mm, 6mm) was searched. a = 5.2mm and 5.8mm were selected respectively, and the three-dimensional geometric model of the wing structure was reconstructed to obtain the maximum deformation of the additive manufacturing feature points respectively. The golden section method was used to determine the optimal discontinuous spacing a opt =5.4mm.

[0071] By the optimal discontinuous spacing a opt =5.4mm, the thermal deformation of the wing's discontinuous lattice support structure at the characteristic points on the wing surface is as follows: Figure 6 As shown, the maximum thermal deformation is within 0.5 mm.

[0072] The present invention provides a discontinuous lattice support structure design system for suppressing thermal deformation of additive manufacturing, comprising:

[0073] A data determination module is used to determine the non-continuous lattice filling area of ​​the missile wing, and determine the design density of the filling area and the shape accuracy index of the missile wing additive manufacturing;

[0074] The curve fitting module is used to determine the LD curve of the unit cell size and unit cell diameter of the filling area based on the body-centered cubic lattice type and the design density of the filling area by adopting equal density design;

[0075] The spacing optimization module is used to construct a three-dimensional geometric model of the wing structure based on the LD curve, perform thermal deformation analysis of additive manufacturing, and determine the spacing interval of the body-centered cubic lattice based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing; and obtain the optimal discontinuous spacing based on the spacing interval of the body-centered cubic lattice.

[0076] The present invention provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the steps of the above method are implemented when the computer program is executed by the processor.

[0077] The present invention provides a storage medium on which a computer program is stored. When the computer program is run, it is used to execute the steps of the above method.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing, characterized in that: Used to optimize the support structure inside the wing, including: Determine the non-continuous lattice filling area of ​​the wing, and determine the design density of the filling area and the shape accuracy index of the wing additive manufacturing; Based on the body-centered cubic lattice type, according to the design density of the filling area, an equal-density design is adopted to determine the LD curve of the unit cell size and unit cell diameter of the filling area; Based on the LD curve, a three-dimensional geometric model of the wing structure is constructed to perform thermal deformation analysis of additive manufacturing. The spacing range of the body-centered cubic lattice is determined by combining the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing. The optimal discontinuous spacing is obtained based on the spacing interval of the body-centered cubic lattice.

2. The method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing according to claim 1, characterized in that: The LD curve of the unit cell size and unit cell diameter of the filling area is determined according to the following steps: Get the unit cell density based on body-centered cubic lattice type; The equal-density design is adopted, and the unit cell density is used as the design density of the filling area to obtain the diameter of the minimum size and the diameter of the maximum size of the lattice unit cell; Based on the height of the filled area, determine the minimum and maximum sizes of the lattice unit cell; According to the minimum size and maximum size of the lattice unit cell, and the diameter of the lattice unit cell at the minimum size and the diameter of the lattice unit cell at the maximum size, the LD curve of the unit cell size and the unit cell diameter of the filling area is obtained.

3. The method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing according to claim 1, characterized in that: After determining the LD curve of the unit cell size and unit cell diameter of the filling area, it also includes: When the spacing of the body-centered cubic lattice is equal to zero, a three-dimensional geometric model of the missile wing structure filled with the body-centered cubic lattice is established, and the thermal deformation simulation of the additive manufacturing process is carried out to extract the maximum deformation of the characteristic points on the outer surface of the missile wing; Whether the spacing is optimized is determined based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing.

4. The method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing according to claim 1, characterized in that: The optimal discontinuous spacing is obtained by using the golden section method based on the spacing interval of the body-centered cubic lattice.

5. The method for designing a discontinuous lattice support structure for suppressing thermal deformation in additive manufacturing according to claim 1, characterized in that: The design density of the filling area refers to the ratio of the maximum mass allowed by the discontinuous lattice support structure to the volume of the filling area; The shape accuracy index of the missile wing additive manufacturing refers to the deviation of the actual shape of the missile wing relative to the theoretical shape after additive manufacturing by applying a non-continuous dot matrix to the missile wing structure.

6. A discontinuous lattice support structure design system for suppressing thermal deformation of additive manufacturing, characterized in that: include: A data determination module is used to determine the non-continuous lattice filling area of ​​the missile wing, and determine the design density of the filling area and the shape accuracy index of the missile wing additive manufacturing; The curve fitting module is used to determine the LD curve of the unit cell size and unit cell diameter of the filling area based on the body-centered cubic lattice type and the design density of the filling area by adopting equal density design; The spacing optimization module is used to construct a three-dimensional geometric model of the wing structure based on the LD curve, perform thermal deformation analysis of additive manufacturing, and determine the spacing interval of the body-centered cubic lattice based on the difference between the maximum deformation of the characteristic points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing; and obtain the optimal discontinuous spacing based on the spacing interval of the body-centered cubic lattice.

7. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the computer program implements the steps of the method according to any one of claims 1 to 5 when executed by the processor.

8. A storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, it is used to execute the steps of the method according to any one of claims 1 to 5.

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