Patent Description:
In recent years, the development of national defense and civil industry has a very urgent demand for vibration and noise reduction technology. For example, the vibration of the ship structure will not only cause fatigue damage to the hull structure, but also reduce the comfort and safety of passengers. For military submarines, excessive noise will seriously affect their stealth effect, thereby increasing their risk of exposure and reducing their combat effectiveness. During the long-term use of the aircraft, vibrations will cause problems such as cracks in the rudder and the tail cover, which will seriously affect the reliability of the flight performance and the service life of the aircraft. During a high-speed flight, the aerospace vehicle is easy to damage the empennage due to the resonance phenomenon, causing its flight direction to change, causing serious consequences of damage to the aerospace vehicle. Nowadays, vibration and noise reduction has become a key technical bottleneck restricting the high performance service of high-end equipment in the fields of ships, aerospace and other fields.

The functional structure with vibration reduction is to transform the mechanical energy of vibration into other forms of energy under the action of external excitation through the structural design and the damping performance of the material itself, to achieve the purpose of reducing vibration and noise. Common damping materials include polymer damping materials, high-damping metal materials and porous metals. Polymer damping materials have been used in the fields of aerospace and ship vibration and noise reduction to some extent, but the natural disadvantages of easy aging and low stiffness make it difficult to guarantee the long-term effective performance, which has become a huge obstacle and technical bottleneck that restricts their further application and development. High-damping metal materials and porous metals based on metal materials have obvious advantages in mechanical properties, anti-aging properties, and corrosion resistance, showing broad application prospects and scientific value.

Porous metals are mainly divided into metal foam and lattice metals. The lattice metal has the advantages of the free design of pore structure, free adjustment of porosity, and the use of existing high-damping metal materials as the base material. There is a large region for innovation of the lattice metal, but the current design of some lattice metals mainly focuses on the mechanical properties, and has not yet involved the design of variable density lattice metal pore structure based on the improvement of vibration damping performance. On the other hand, the forming process of using selective laser melting of the additively manufacturing lattice metal has the outstanding characteristics of small cross-section discontinuous scanning, which is easy to cause defects such as cracks on the surface of pore struts of the lattice metal, and the surface quality of lattice metal is poor, so that it seriously affects the actual service performance of the lattice metals.

Therefore, based on the improvement of vibration damping performance, the structure design of variable density lattice metal is driven, the variable density lattice metal is designed by a modal strain energy method, and the variable density lattice metal is prepared by a selective laser melting additive manufacturing process, and no relevant reports have been found about that.

<CIT> discloses a method of producing a three-dimensional porous tissue in-growth structure. The method includes the steps of depositing a first layer of metal powder and scanning the first layer of metal powder with a laser beam to form a portion of a plurality of predetermined unit cells. Depositing at least one additional layer of metal powder onto a previous layer and repeating the step of scanning a laser beam for at least one of the additional layers in order to continuing forming the predetermined unit cells. The method further includes continuing the depositing and scanning steps to form a medical implant.

<CIT> discloses an implant for in-vivo implantation which comprises an assembly of two or more constructive elements which are movable relative to each other. Each constructive element is partly or completely porous and comprises a porous part with a matrix of open cells. A first matrix of the first element comprises a first overlapping part with a form-closed connection to a second overlapping part of a second matrix of the second of the constructive elements through which the first overlapping part extends. The overlapping parts are movable relative to each other to change a combined shape of the overlapping parts.

<CIT> discloses a method for manufacturing an implant includes pre-selecting a designed porous microstructure having a lattice composed of cells, including selecting one or more predetermined cell topologies, selecting a predetermined porosity, cell strut thickness and packing factor of the lattice, and selecting an arrangement of the cells within the lattice to have a periodic and/or aperiodic arrangement. Additive manufacturing is used to form the designed porous lattice microstructure in at least a region of at least an external surface of the implant.

<CIT> discloses a methodology integrating multiscale analysis and design optimization to design a novel bone replacement implant made of a functionally graded cellular material that meets fatigue requirements imposed by cyclic loadings. The pore microarchitecture, described by interconnectivity, porosity, pore size as well as pore topology, is optimally designed for tissue regeneration and mechanical strength. The method can contribute to the development of a new generation of bone replacement implants with a graded cellular microstructure.

"Damping behaviours of steel-based Kelvin lattice structures fabricated by indirect additive manufacture combining investment casting" (<NPL>) discloses damping properties of lattice metal with Kelvin structure were studied by simulation and experiment, and it was prepared by indirect additive manufacturing combined with precision casting.

<CIT> discloses exemplified methods and systems facilitate manufacturing of a new class of mechanical, loading-bearing components having optimized stress/strain three-dimensional meta-structure structures as finite-element-based 3D volumetric mesh structures. The resulting three-dimensional meta-structure structures provide high strength, ultra-light connectivity, with programmable interlinkage properties (e.g., density/porosity of linkages).

"Full compression response of FG-based scaffolds with varying porosity via an effective numerical scheme" (<NPL>) discloses a full compression response of fiber-based scaffolds with different porosity based on effective numerical format. In this paper, the gradient scaffolds (bone-gyro and sheet-gyro) of gyro-based three-period minimal surface (TPMS) with different porosity in axial and radial directions were prepared by selective laser melting technology, using Ti-6Al-4V powder as raw material.

It is an object of the present invention to provide an advantageous variable density lattice metal having vibration damping characteristics, an additive manufacturing method therefor, and a use thereof. The object is achieved by the features of the respective independent claims. Further embodiments are defined by the respective dependent claims.

The advantage of the present invention and beneficial effects are as follows.

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention.

The preparation method of the present invention will be described in detail below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

This embodiment is to design and prepare a variable density lattice metal with a porosity of <NUM>% and having vibration damping properties.

The tetradecahedron structure is used as the cell structure of the lattice metal, as shown in <FIG>. The modal shape of the structure is calculated by finite element software, and the settlement results are post-processed to extract the modal strain. The modal strain energy point cloud diagram is constructed by using the MATLAB software, as shown in <FIG>. The continuous gradient change of lattice metal pore strut diameter is driven by a strain energy field function. The diameter of lattice metal pore strut is the largest in the area with large modal strain energy, which is set to be <NUM>, and the diameter of lattice metal pore strut is the smallest in the area with small modal strain energy, which is set to be <NUM>, the diameter of the metal pore strut of the variable density lattice changes continuously in the range of <NUM>-<NUM>, the step size of the gradient change is <NUM>, and the cell size is <NUM>. The above mentioned modal strain energy method is used to drive the design of variable density lattice metal cells, and expand in space to from the variable density lattice metal.

The variable density lattice metal having vibration damping characteristics is prepared by selective laser melting additive manufacturing process, including the following steps:.

The free attenuation curve of the variable density lattice metal prepared in this embodiment under vibration excitation conditions is shown in <FIG>. It can be seen that the vibration response signal decays rapidly in the variable density lattice metal, which has good vibration damping characteristics. At the same time, the variable density lattice metal in this embodiment has both a smooth compressive stress-strain curve and an obvious plastic yield platform. The compressive stress-strain curve is shown in <FIG>, and the yield platform stress is about <NUM> MPa.

This experiment is a comparative example of Example <NUM>; in the process of designing and preparing the variable density lattice metal with a porosity of <NUM>% with vibration damping characteristics, the change position of the pore strut diameter and the connection position of the pore strut of the variable density lattice metal is not smoothed, and the scanning strategy adopts the linear scanning method. Its structural design and other preparation process parameters are completely consistent with Embodiment <NUM>, and the specific preparation steps are as follows:.

The surface roughness of the variable-density lattice metal prepared in this comparative example is relatively large, and there are many microcracks on the surface of the pore strut; the compressive stress-strain curve is jagged, and there is no obvious plastic yield platform.

This embodiment is to design and prepare a variable density lattice metal with a porosity of <NUM>% and having vibration damping characteristics.

The combined structure of dodecahedron and tetradecahedron is used as the cell structure of lattice metal, as shown in <FIG>. The modal shape of the structure is calculated by the finite element software, and the calculation results are post-processed to extract the modal strain. The modal strain energy point cloud diagram is constructed by using MATLAB software, and the continuous gradient change of the lattice metal pore-strut diameter is driven by the strain energy field function. The pore strut diameter of the lattice metal in the area with large modal strain energy is the largest, which is set to be <NUM>; the pore strut diameter of the lattice metal in the area with small modal strain energy is the smallest, which is set to be <NUM>, and the pore strut diameter of variable density lattice metal is continuously changed in the range of <NUM>-<NUM>, the step size of the gradient change is <NUM>, and the cell size is <NUM>. The above mentioned modal strain energy method is used to drive the design of variable density lattice metal, and expand in space to form the variable density lattice metal.

The variable density lattice metal having vibration damping characteristics is prepared by the selective laser melting additive manufacturing process, including the following steps:.

The truncated octahedral structure is used as the cell structure of the lattice metal, as shown in <FIG>. The modal shape of the structure is calculated by the finite element software, and the calculation results are post-processed to extract the modal strain. The modal strain energy point cloud diagram is constructed by using MATLAB software, and the continuous gradient change of the pore strut diameter of the lattice metal pore is driven by the strain energy field function. The pore strut diameter of the lattice metal in the area with large modal strain energy is the largest, which is set to be <NUM>, and the pore strut diameter of the lattice metal in the area with small modal strain energy is the smallest, which is set to be <NUM>, and the pore strut diameter of the variable density lattice metal is continuously changed in the range of <NUM> to <NUM>, the step size of the gradient change is <NUM>, and the cell size is <NUM>. The above-mentioned modal strain energy method is used to drive the design of the variable density lattice metal, and expand in space to form the variable density lattice metal.

The variable density lattice metal of this embodiment has vibration damping characteristics, and simultaneously has a smooth compressive stress-strain curve and an obvious plastic yield platform, and the yield platform stress is 5MPa.

Claim 1:
A variable density lattice metal having vibration damping characteristics, characterized in that each of the cells of the lattice metal has a tetradecahedron structure, a combination structure of a dodecahedron and a tetradecahedron, or a truncated octahedron structure, and the cells are expanded to form the lattice metal;
wherein the lattice metal is based on a modal strain energy method to drive the design of pore strut diameters, and the overall structural density shows a non-homogeneous continuous gradient change, wherein the modal strain energy method is used to calculate a modal shape of the structure through a finite element software, a modal strain is extracted and a modal strain energy point cloud diagram is constructed, a continuous gradient change of the pore strut diameters of the lattice metal is driven through a strain energy field function, and the value of the pore strut diameters of the lattice metal in an area with large modal strain energy is larger than in an area of small strain energy, wherein the gradient change of the pore strut diameters of the variable-density lattice metal is not in a single direction;
wherein the variable density lattice metal is prepared by a selective laser melting additive manufacturing process;
wherein the porosity of the lattice metal is <NUM>% to <NUM>%, the pore strut diameters change continuously in the range of <NUM> to <NUM>, the step size of the continuous gradient change of the pore strut diameters of the lattice metal is <NUM>-<NUM>, and the cell size of the lattice metal is <NUM> to <NUM>.