A discontinuous lattice support structure design method to inhibit heat distortion in additive manufacturing

Abstract

The present application relates to the technical field of metal additive manufacturing, and particularly relates to a non-continuous lattice support structure design method for inhibiting additive manufacturing thermal deformation, which comprises determining a non-continuous lattice filling area of a wing, and determining a design density of the filling area and an outline accuracy index of the wing additive manufacturing; determining an L-D curve of a cell size and a cell diameter of the filling area; constructing a three-dimensional geometric model of the wing structure based on the L-D curve, performing additive manufacturing thermal deformation analysis, and determining a distance interval of a body-centered cubic lattice by combining the difference between the maximum deformation of a wing surface feature point and the outline accuracy index of the wing additive manufacturing; and obtaining an optimal non-continuous distance according to the distance interval of the body-centered cubic lattice. The non-continuous lattice support structure satisfying the wing outline accuracy requirement and the lightweight requirement is obtained through non-continuous lattice structure size design and distance design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal additive manufacturing, in particular to a non-continuous dot array support structure design method for inhibiting additive manufacturing thermal deformation. BACKGROUND

[0002] Additive manufacturing technology brings greater freedom to the structural design of the wing, but in the additive manufacturing process, the molten pool solidification shrinkage and uneven temperature field caused by the laser heat source melting the material lead to deformation such as concave and crack on the outer surface of the structure, which affects the surface precision. For small wings with large aspect ratio, the thin skin area is large, and the deformation problem caused by thermal stress is particularly prominent.

[0003] Currently, from the design point of view, the main method to inhibit the thermal stress deformation of additive manufacturing is to increase the support structure, which has two structural forms of external support and internal support. Since the external support needs to be removed after manufacturing, it will cause material waste, so increasing the internal support structure becomes an effective way to inhibit deformation. The arrangement of the internal support structure of the wing is too compact, which does not meet the requirements of lightweight design of the structure; the arrangement is too sparse, which cannot effectively inhibit the thermal stress deformation of the thin skin. Therefore, designing a reasonable internal support structure is the key to ensuring the shape precision of the thin-walled structure of the wing and realizing the lightweight structure. SUMMARY

[0004] In order to solve the above technical problems, the present application mainly aims at the thermal deformation problem caused by thermal stress in the additive manufacturing process of the thin skin of the wing, and provides a non-continuous dot array support structure design method for inhibiting additive manufacturing thermal deformation. The load-bearing structure of the wing has been designed by topological optimization and other design methods in the early stage, and on this basis, the non-continuous dot array support structure meeting the shape precision requirements and lightweight requirements of the wing is obtained through the size design and spacing design of the non-continuous dot array structure.

[0005] The first object of the present application is to provide a non-continuous dot array support structure design method for inhibiting additive manufacturing thermal deformation, which is used for optimizing the support structure inside the wing, comprising:

[0006] determining the non-continuous dot array filling area of the wing, and determining the design density of the filling area and the shape precision index of the additive manufacturing of the wing;

[0007] based on the body-centered cubic dot array type, according to the design density of the filling area, using equal density design, determining the L-D curve of the cell size and cell diameter of the filling area;

[0008] based on the L-D curve, constructing a three-dimensional geometric model of the wing structure, performing additive manufacturing thermal deformation analysis, and combining the difference between the maximum deformation of the feature points on the outer surface of the wing and the shape precision index of the additive manufacturing of the wing, to determine the spacing interval of the body-centered cubic dot array;

[0009] The optimal non-continuous interval is obtained according to the interval of the body-centered cubic lattice.

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

[0011] The cell density is obtained based on the type of the body-centered cubic lattice.

[0012] The diameter under the minimum size and the diameter under the maximum size of the lattice cell are obtained by using the equal-density design, taking the cell density as the design density of the filling area.

[0013] The minimum size and the maximum size of the lattice cell are determined based on the height of the filling area.

[0014] The L-D curve of the cell size of the filling area and the cell diameter is obtained according to the minimum size and the maximum size of the lattice cell, and the diameter under the minimum size and the diameter under the maximum size of the lattice cell.

[0015] Preferably, after the L-D curve of the cell size of the filling area and the cell diameter is determined, the method further comprises:

[0016] When the interval of the body-centered cubic lattice is equal to zero, a three-dimensional geometric model of the body-centered cubic lattice filling of the wing structure of the missile is established, and thermal deformation simulation of the additive manufacturing process is performed to extract the maximum deformation of the feature points on the outer surface of the wing.

[0017] According to the size between the maximum deformation of the feature points on the outer surface of the wing and the shape accuracy index of the additive manufacturing of the wing, it is determined whether the interval is optimized.

[0018] Preferably, the optimal non-continuous interval is obtained according to the interval of the body-centered cubic lattice by using the golden section method.

[0019] Preferably, the design density of the filling area is the ratio of the maximum mass allowed by the non-continuous lattice support structure to the volume of the filling area.

[0020] The shape accuracy index of the additive manufacturing of the wing refers to the deviation of the actual shape of the wing after additive manufacturing relative to the theoretical shape when the non-continuous lattice is applied to the wing structure.

[0021] The second object of the application is to provide a non-continuous lattice support structure design system for suppressing thermal deformation of additive manufacturing, characterized in that it comprises:

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

[0023] A curve fitting module is configured to determine an L-D curve of the cell size and the cell diameter of the filling area based on the equal-density design according to the design density of the filling area and the body-centered cubic lattice type;

[0024] A spacing optimization module is configured to determine the spacing interval of the body-centered cubic lattice based on the L-D curve, construct a three-dimensional geometric model of the wing structure, perform additive manufacturing thermal deformation analysis, and determine the optimal non-continuous spacing according to the spacing interval of the body-centered cubic lattice.

[0025] A third object of the present application is to provide an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the computer program implementing the steps of the above method when executed by the processor.

[0026] A fourth object of the present application is to provide a storage medium having stored thereon a computer program for executing the steps of the above method when executed.

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

[0028] The present application provides a non-continuous lattice support structure design method for suppressing additive manufacturing thermal deformation, which determines the optimal non-continuous spacing of the lattice through an optimization algorithm, and can ensure the shape accuracy of the structure under the requirement of lightweight design of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The flow chart for the non-continuous lattice support structure design of the wing;

[0030] Figure 2 The non-continuous lattice filling area (gray area) of the wing;

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

[0032] Figure 4 The relationship diagram of the cell size and the diameter;

[0033] Figure 5 The non-continuous lattice spacing diagram;

[0034] Figure 6 The thermal deformation schematic diagram of the surface feature points of the wing. DETAILED DESCRIPTION

[0035] In order to illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following will be described in detail in combination with embodiments.

[0036] The present application aims at the thermal deformation caused by thermal stress in the thin skin additive manufacturing process of the wing, and provides a non-continuous lattice support structure optimization design method for inhibiting thermal deformation. The load bearing structure design of the wing has been completed through topological optimization and other design methods in the early stage, and on this basis, the non-continuous lattice support structure meeting the shape accuracy requirement and lightweight requirement of the wing is obtained through the size design and spacing design of the non-continuous lattice structure.

[0037] In order to achieve the above purpose, the present application provides a non-continuous lattice support structure design method for inhibiting thermal deformation in additive manufacturing, which is used for optimizing the support structure inside the wing, comprising:

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

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

[0040] The shape accuracy index of the additive manufacturing of the wing refers to the deviation of the actual shape of the wing after additive manufacturing relative to the theoretical shape when the non-continuous lattice is applied to the wing structure.

[0041] For example, the determination of the non-continuous lattice filling area Omega is based on the completion of the early wing main load bearing structure, the wing has a clear load transmission path, and the area without the support of the skin stiffener is the non-continuous lattice filling area Omega. According to the overall design index requirement, the design density p and the shape accuracy index d of the filling area are determined. The design density requirement p refers to the ratio of the maximum mass allowed by the non-continuous lattice support structure to the volume of the filling area; the shape accuracy requirement d refers to the deviation of the actual shape of the wing after additive manufacturing relative to the theoretical shape when the non-continuous lattice is applied to the wing structure.

[0042] S2, based on the body-centered cubic lattice type, according to the design density of the filling area, the L-D curve of the filling area unit cell size and unit cell diameter is determined by using equal density design;

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

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

[0045] The equal density design is adopted, the unit cell density is taken as the design density of the filling area, and the diameter under the minimum size of the lattice unit cell and the diameter under the maximum size are obtained;

[0046] Based on the height of the filling area, the minimum size and the maximum size of the lattice unit cell are determined;

[0047] According to the minimum size and the maximum size of the lattice cell, and the diameter under the minimum size and the diameter under the maximum size, the L-D curve of the cell size and the cell diameter of the filling area is obtained.

[0048] For example, based on the design density of the filling area * , the cell diameter D of the filling area is determined by using the equal-density design, and the specific implementation process is as follows:

[0049] S2.1 Select the Body Centered Cubic (BCC) lattice structure form with the lightest mass, good bending resistance and stability. The characteristic parameters of the BCC lattice cell include: cell size L and rod diameter D. The angle between the rod and the additive manufacturing substrate is θ=45°, which meets the manufacturability.

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

[0051]

[0052] Where, ρ M is the density of the additive manufacturing raw material.

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

[0054] After determining the L-D curve of the cell size and the cell diameter of the filling area, the following steps are further included:

[0055] When the spacing of the Body Centered Cubic lattice is equal to zero, a three-dimensional geometric model of the Body Centered Cubic lattice filled elastic wing structure is established, and a thermal deformation simulation of the additive manufacturing process is performed to extract the maximum deformation of the characteristic points on the outer surface of the elastic wing;

[0056] According to the size between the maximum deformation of the characteristic points on the outer surface of the elastic wing and the shape accuracy index of the elastic wing additive manufacturing, it is determined whether the spacing is optimized.

[0057] For example, when the spacing a = 0 mm, a three-dimensional geometric model of the wing structure filled with a body-centered cubic (BCC) lattice is established. The commercial software Simufact Additive is used to simulate the thermal deformation of the additive manufacturing process. The maximum deformation δ of the feature points on the outer surface of the wing is extracted. If δ ≥ δ*, the optimization is terminated, indicating that the design density ρ* index is too stringent; 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, perform additive manufacturing thermal deformation analysis, and determine the spacing range of the body-centered cubic lattice by combining the difference between the maximum deformation of the feature 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 range of the body-centered cubic lattice.

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

[0061] For example, when the maximum deformation of the feature points on the outer surface of the wing is less than the shape accuracy index of the wing additive manufacturing, the spacing is determined and optimized to obtain the spacing range of the body-centered cubic lattice, specifically including:

[0062] Using the forward and backward method, a three-dimensional geometric model of the missile wing structure was reconstructed based on the LD curve, and thermal deformation simulation of the additive manufacturing process was performed. The maximum deformation δ of the feature points on the outer surface of the missile wing was compared with the shape accuracy index δ. * If δ < δ*, increase the spacing a; if δ > δ*, decrease the spacing a; if δ = δ*, obtain the boundary value of a, and continuously search to obtain the interval of spacing a (a min a max );

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

[0064] To further illustrate the design method of 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 Figure 1 As shown, a design method for a discontinuous lattice support structure to suppress thermal deformation in additive manufacturing includes:

[0066] S1. Determine the discontinuous lattice filling region of the missile wing and define the design density ρ of the filling region. * The dimensional accuracy index δ of the additive manufacturing of missile wings* The filling area of the elastic wing is determined as Figure 2 The design density of the filling area is determined as * ≤0.15g / cm 3 The outer surface precision of the elastic wing after additive manufacturing is * ≤0.5mm;

[0067] S2. Select a body-centered cubic BCC lattice type, and a BCC lattice structure diagram is shown in Figure 3 Based on the height of the filling area, the minimum size of the lattice unit cell is determined as the diameter D min and the maximum size of the lattice unit cell is determined as the diameter D max and the L-D curve of the cell size and the cell diameter is obtained. The specific process is as follows:

[0068] S2.1 The additive manufacturing raw material is selected as AlSi 10 Mg, and the expression of the lattice unit cell density is obtained according to formula (1);

[0069] S2.2 According to the filling area of the elastic wing, the minimum size L min of the unit cell is 4mm, the maximum size L max of the unit cell is 14mm, and then D min =0.4mm and D max =1.4mm are obtained. The L-D curve of the cell size and the cell diameter is shown in Figure 4 .

[0070] S3. Based on the L-D curve, the three-dimensional geometric model of the elastic wing structure is reconstructed, the cell spacing a is shown in Figure 5 , and the thermal deformation simulation of the additive manufacturing process is performed by using the Simufact Additive software. The step length h=1mm and the magnification factor γ=1 are set by using the advance and retreat method, and the interval (5mm, 6mm) of the spacing a is searched. The spacing a=5.2mm and 5.8mm are selected respectively, the three-dimensional geometric model of the elastic wing structure is reconstructed, the maximum deformation of the additive manufacturing feature points is obtained respectively, and the golden section method is used to determine the optimal non-continuous spacing a opt =5.4mm.

[0071] The non-continuous lattice support structure of the elastic wing obtained by the optimal non-continuous spacing a opt =5.4mm has the thermal deformation of the elastic wing surface feature points as shown in Figure 6 , and the maximum thermal deformation is within 0.5mm.

[0072] The present application provides a non-continuous lattice support structure design system for inhibiting thermal deformation of additive manufacturing, comprising:

[0073] A data determination module is configured to determine a non-continuous point array filling area of the wing, and determine a design density of the filling area and an outline precision index of the wing additive manufacturing;

[0074] A curve fitting module is configured to determine an L-D curve of the cell size and the cell diameter of the filling area based on the equal density design according to the design density of the filling area based on the body-centered cubic point array type;

[0075] A spacing optimization module is configured to construct a three-dimensional geometric model of the wing structure based on the L-D curve, perform additive manufacturing thermal deformation analysis, and determine a spacing interval of the body-centered cubic point array by combining the difference between the maximum deformation of the wing surface feature point and the outline precision index of the wing additive manufacturing, and obtain an optimal non-continuous spacing according to the spacing interval of the body-centered cubic point array.

[0076] The application provides an electronic device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the computer program is executed by the processor to implement the steps of the above method.

[0077] The application provides a storage medium, which stores a computer program, wherein the computer program is executed to implement the steps of the above method.

[0078] The above description is only the preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement, improvement, etc. within the principle of the application should be included in the protection scope of the application.

Claims

1. A design method for a discontinuous lattice support structure to suppress thermal deformation in additive manufacturing, characterized in that, Support structures used to optimize the internal structure of the missile wing include: Determine the discontinuous 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; Based on the body-centered cubic lattice type, and according to the design density of the filled region, an isodense design is adopted to determine the unit cell size and unit cell diameter of the filled region. LD curve; based on LD A three-dimensional geometric model of the wing structure is constructed using curves. Additive manufacturing thermal deformation analysis is performed, and the spacing range of the body-centered cubic lattice is determined by combining the difference between the maximum deformation of the feature 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 range of the body-centered cubic lattice. The unit cell size and unit cell diameter of the filling region LD The curve is determined according to the following steps: Unit cell density is obtained based on body-centered cubic lattice type; An isodense design was adopted, with the unit cell density used as the design density of the filling area, to obtain the diameter of the lattice unit cell at its minimum size and the diameter at its maximum size. Based on the height of the filled region, determine the minimum and maximum size of the lattice unit cell; Based on the minimum and maximum dimensions of the lattice unit cell, and the diameters at the minimum and maximum dimensions of the lattice unit cell, obtain the unit cell size and diameter of the filled region. L - D curve; The optimal discontinuous spacing is obtained by using the golden section method on the spacing interval of the body-centered cubic lattice. The design density of the filling region refers to the ratio of the maximum allowable mass of the discontinuous lattice support structure to the volume of the filling region. The shape accuracy index of the missile wing additive manufacturing refers to the deviation between the actual shape of the missile wing and the theoretical shape after additive manufacturing when a discontinuous dot matrix is ​​applied to the missile wing structure.

2. The method for designing a discontinuous lattice support structure to suppress thermal deformation in additive manufacturing according to claim 1, characterized in that, Determine the unit cell size and unit cell diameter of the filled region. LD Following the curve, it also includes: When the spacing of the body-centered cubic lattice is zero, a three-dimensional geometric model of the wing structure filled with body-centered cubic lattice is established, and the thermal deformation simulation of the additive manufacturing process is performed to extract the maximum deformation of the feature points on the outer surface of the wing. The spacing is determined based on the relationship between the maximum deformation of feature points on the outer surface of the wing and the shape accuracy index of the wing additive manufacturing.

3. A system for designing a discontinuous lattice support structure to suppress thermal deformation in additive manufacturing as described in claim 1, characterized in that, include: The data determination module is used to determine the discontinuous dot matrix filling area of ​​the missile wing, and to 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 unit cell size and diameter of the filled region based on the body-centered cubic lattice type and the designed density of the filled region, using an isodense design. LD curve; Spacing optimization module, used for... LD A three-dimensional geometric model of the missile wing structure is constructed using curves. Additive manufacturing thermal deformation analysis is performed, and the spacing range of the body-centered cubic lattice is determined by combining the difference between the maximum deformation of the feature points on the outer surface of the missile wing and the shape accuracy index of the missile wing additive manufacturing. The optimal discontinuous spacing is obtained based on the spacing range of the body-centered cubic lattice.

4. 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 computer program, when executed by the processor, implements the steps of the method as described in claim 1 or 2.

5. A storage medium, characterized in that, It stores a computer program that, when run, performs the steps of the method described in claim 1 or 2.

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