CN-121997639-A - Lightweight double-layer cylinder structure design method for additive manufacturing

CN121997639ACN 121997639 ACN121997639 ACN 121997639ACN-121997639-A

Abstract

The invention relates to a design method of a lightweight double-layer cylinder structure for additive manufacturing, belongs to the field of additive manufacturing, and solves the problems that the traditional double-layer cylinder structure has a large number of parts, is difficult to assemble, cannot consider the lightweight and additive manufacturing manufacturability, and has large calculation amount of overall topology optimization and difficult manufacturing result. The method comprises the steps of setting an additive manufacturing direction, dividing a design domain and a non-design domain, dividing the design domain in the axial direction and the radial direction to obtain a plurality of periodically arranged minimum design units, performing topology optimization by taking a minimum volume method as an objective function in each minimum design unit, applying functional load constraint, additive manufacturing self-forming constraint and symmetry constraint, combining the optimized minimum design unit array and the optimized minimum design unit array to obtain an integral double-layer cylinder structure, processing a closed cavity, and finally performing strength check and iterative optimization. The invention realizes the integrated and lightweight design of the double-layer cylinder structure, ensures the structural performance and ensures the feasibility of the additive manufacturing process.

Inventors

SU JIANGZHOU
HAN WEIQUN
WANG ZHIMIN
WANG YIMENG
CHE LEI
WANG YUJIAN
YANG CHENG
ZHAO WENZHENG
JIA XU
LI PENG

Assignees

北京航星机器制造有限公司

Dates

Publication Date: 20260508
Application Date: 20251229

Claims (10)

1. The design method of the lightweight double-layer cylinder structure for additive manufacturing is characterized by comprising the following steps of: S1, setting the manufacturing direction of the additive as the axial direction of a cylinder, dividing a structure which is in contact with an external structure and is assembled or kept functional into a non-design domain, and dividing the rest of the structure into design domains; S2, dividing the design domain in the axial direction and the radial direction to obtain a plurality of minimum design units which are periodically arranged; s3, in each minimum design unit, performing topological optimization by taking a minimum volume method as an objective function, and applying constraint conditions in the optimization process, wherein the constraint conditions at least comprise functional load constraint, additive manufacturing self-formability constraint and symmetry constraint; S4, performing array and Boolean addition operation on the design domain part in the minimum design unit after topology optimization to obtain a double-layer cylinder design domain structure, combining the double-layer cylinder design domain structure with a non-design domain structure to obtain an integral double-layer cylinder structure, and checking and processing a closed cavity; s5, performing strength check on the integral double-layer cylinder structure, if the technical index is met, completing design, otherwise, returning to the step S2 to adjust the structure of the minimum design unit and performing iterative optimization.
2. The design method according to claim 1, wherein in step S2, the minimum design unit is a sector block whose dimensions are determined by an inner radius R, an outer radius R, a length d, an axial division number a, and a radial division number b of the double-layered cylinder, a difference between the thicknesses R and R, a height d/b, an arc length of the sector inner diameter of 2rr/a, and an arc length of the sector outer diameter of 2rr/a.
3. The method of claim 2, wherein the minimum design unit is sized to satisfy a self-formability constraint of d/b≥2πR/a.
4. The design method according to claim 1, wherein in step S3, the objective function of the topology optimization is minV (x) = ≡ Ω x i (ζ) dζ; Where ζ represents a spatial coordinate vector in the design domain Ω, x i (ζ) is a function using the spatial coordinate ζ as an argument, representing a relative density of the material at the coordinate, and a continuous variable whose value range is [0,1], when x i (ζ) =0, representing no material at the coordinate ζ, and when x i (ζ) =1, representing a full material at the coordinate ζ.
5. The design method according to claim 1, wherein in step S3, the functional load constraint includes an input load and a corresponding constraint result; The input load includes at least one of a concentrated force, pressure, and temperature load; the constraint results include at least one of a structural maximum stress less than a material allowable stress, and a structural maximum displacement less than an allowable maximum displacement.
6. The design method according to claim 1, wherein in the step S3, the additive manufacturing self-formability constraint is that an included angle θ between a normal vector n of any point on a surface of the structure and an additive manufacturing direction e Z is satisfied, wherein θ is equal to or greater than θ min , θ min is a minimum self-forming angle, and the additive manufacturing direction e Z is a vertically upward direction.
7. The design method according to claim 1, wherein in step S3, the symmetry constraint is that the minimum design unit is geometrically symmetric in both axial and radial directions, specifically that the coordinate ζ i ＝[x i ,y i ,z i ] T of any point i within the minimum design unit, the coordinate of the symmetry point i' about the XZ plane is [ x i ,-y i ,z i ] T ], and the coordinate of the symmetry point i "about the XY plane is [ x i ,y i ,-z i ] T ".
8. The method according to claim 1, wherein in step S4, the checking and processing the closed cavity means that if the combined whole double-layer cylinder structure has a closed cavity, a powder cleaning hole or a clear liquid hole is formed in the closed cavity.
9. The design method according to claim 1, wherein in step S5, the technical indexes include structural bearing capacity and weight requirements, and the iterative optimization includes returning to step S2 to perform topology optimization model adjustment on the structure of the minimum design unit based on the overall check result to further remove materials.
10. A double-layer cartridge lightweight structure suitable for additive manufacturing, characterized in that the structure is obtained according to the design method of any one of claims 1 to 9.

Description

Lightweight double-layer cylinder structure design method for additive manufacturing Technical Field The invention relates to the technical field of additive manufacturing, in particular to a lightweight double-layer cylinder structure design method for additive manufacturing. Background The double-layer cylinder structure is taken as a typical engineering structure and has wide application in the fields of aerospace, energy chemical industry and the like, and is generally composed of an inner-layer cylinder, an outer-layer cylinder and a sandwich structure in the middle. With the development of additive manufacturing technology, a new process path is provided for the integrated formation of a complex structure, and a new opportunity is brought for the innovative design of the structure. However, there are still many disadvantages in the design and manufacturing methods for the dual-layer cartridge structure. Based on the design of the traditional manufacturing process, the inner cylinder, the outer cylinder and the sandwich structure (such as reinforcing ribs and filling materials) are usually manufactured separately and then assembled by welding, bolting and the like. The mode has the problems of a large number of parts, complex connection process, long production period and high cost, is limited by the traditional process, has a single sandwich structure form, and is insufficient in design space utilization. If the integral topology optimization method facing additive manufacturing is directly adopted, a lightweight structure with excellent performance can be obtained, but the optimization calculation amount is huge, the optimization result is geometrically complex and possibly contains a large number of suspension structures which are difficult to form, so that manufacturability and design expectation are not matched. Disclosure of Invention In view of the above analysis, the present invention aims to provide a design method of a lightweight dual-layer cylinder structure for additive manufacturing, which is used for solving at least one of the disadvantages of the existing design and manufacturing methods for dual-layer cylinder structures, such as difficulty in assembling parts, long design period, low overall topology optimization calculation efficiency, poor manufacturability, and the like. In one aspect, the embodiment of the invention provides a method for designing a lightweight double-layer cylinder structure for additive manufacturing, which comprises the following steps: S1, setting the manufacturing direction of the additive as the axial direction of a cylinder, dividing a structure which is in contact with an external structure and is assembled or kept functional into a non-design domain, and dividing the rest of the structure into design domains; S2, dividing the design domain in the axial direction and the radial direction to obtain a plurality of minimum design units which are periodically arranged; s3, in each minimum design unit, performing topological optimization by taking a minimum volume method as an objective function, and applying constraint conditions in the optimization process, wherein the constraint conditions at least comprise functional load constraint, additive manufacturing self-formability constraint and symmetry constraint; S4, performing array and Boolean addition operation on the design domain part in the minimum design unit after topology optimization to obtain a double-layer cylinder design domain structure, combining the double-layer cylinder design domain structure with a non-design domain structure to obtain an integral double-layer cylinder structure, and checking and processing a closed cavity; s5, performing strength check on the integral double-layer cylinder structure, if the technical index is met, completing design, otherwise, returning to the step S2 to adjust the structure of the minimum design unit and performing iterative optimization. Further, in step S2, the minimum design unit is a sector block, the dimensions of which are determined by the inner radius R, the outer radius R, the length d, the axial division number a and the radial division number b of the double-layer cylinder, the thickness is the difference between R and R, the height is d/b, the arc length of the sector inner diameter is 2rr/a, and the arc length of the sector outer diameter is 2rr/a. Further, the size of the minimum design unit is required to meet the self-formability constraint that d/b is not less than 2 pi R/a. Further, in step S3, the topological optimization objective function is minV (x) = ≡Ω xi (ζ) dζ; Wherein xi represents a space coordinate vector in a design domain omega, xi (xi) is a function taking the space coordinate xi as an independent variable, represents the relative density of materials at the coordinate, has continuous variable with the value range of [0,1], represents no materials at the coordinate xi when xi (xi) =0, and represents full materials at the coor