CN115681382A

CN115681382A - Mechanical property adjustable high-ratio energy-absorbing lattice structure based on additive manufacturing

Info

Publication number: CN115681382A
Application number: CN202211376439.5A
Authority: CN
Inventors: 杨先锋; 张桥; 李博; 罗敏; 田政
Original assignee: Beihang University; Beijing Institute of Spacecraft System Engineering
Current assignee: Beihang University; Beijing Institute of Spacecraft System Engineering
Priority date: 2022-11-04
Filing date: 2022-11-04
Publication date: 2023-02-03

Abstract

The invention discloses a mechanical property adjustable high-ratio energy-absorbing lattice structure based on additive manufacturing, which is obtained by spatial array continuation arrangement of a plurality of representative cell structures. The representative cell structure is formed by connecting hollow rod elements between the angular points of a body-centered cube and a central point through nodes, the diameter and the wall thickness of each hollow rod element can be designed along the axial direction of the rod element, the lattice cell element belongs to a bending dominant energy absorption structure, and the lattice structure can be obtained by copying a certain number of arrays from the lattice cell elements along 3 spatial directions according to actual working requirements to form a better pressure-bearing and energy-absorbing structure with high specific stiffness and high specific energy absorption. The invention has good bending resistance, overcomes the disadvantage of smaller resistance load of the traditional lattice structure of the same type under the action of compressive load, can convert more borne impact energy into plastic deformation energy of the structure, and increases the platform force and the specific energy absorption of the structure when the structure is crushed.

Description

Mechanical property adjustable high-ratio energy-absorbing lattice structure based on additive manufacturing

Technical Field

The invention belongs to the technical field of energy absorption structures, and particularly relates to a mechanical property adjustable high-ratio energy absorption lattice structure based on additive manufacturing.

Background

When an accident such as impact, explosion or collision occurs, strong impact load is generated and acts on structures such as an aircraft, a naval vessel and the like, and then the structures generate strong impact vibration, so that the structures are seriously plastically deformed and damaged, and further the aircraft, the naval vessel or a vehicle loses the normal operation capability and even causes great life and property loss. How to ensure that the structure does not have serious accidents after being impacted by strong dynamic load becomes a subject of great attention in the field of structural safety protection. Therefore, structures such as honeycomb structures, light sandwich plates, porous foam material filling pipes, lattice materials and the like are produced. When the energy-absorbing structure is under the action of impact load, the impact energy can be effectively converted into the plastic deformation energy of the structure by utilizing the plastic deformation of the energy-absorbing structure, so that the personal safety of the structure and passengers is protected.

The lattice material is a porous material consisting of nodes and connecting rods, has the characteristics of light weight, high strength, energy absorption and the like, and has common topological configurations such as tetrahedrons, pyramids, body-centered cubes and the like. Aiming at a specific application background, the multifunctional characteristics of the dot matrix can be adjusted by controlling the structure of the dot matrix material, so that the dot matrix structure is widely applied to the fields of light-weight industrial components, bone scaffolds, buffers, aerospace, tissue engineering and the like.

However, in the process of impact load action, other types of stretching leading type lattice structures can generate larger peak load in the crushing process, and initial damage is generated to important precision equipment or human body safety; in addition, the platform load of the traditional body-centered cubic solid rod element lattice structure in the crushing process is often lower, and the direct result is that the kinetic energy cannot be fully absorbed to cause serious damage to the structure or human body, or the weight of the structure is increased by violating the lightweight design principle.

Therefore, on the basis of inheriting the traditional bending-dominant body-centered cubic lattice configuration, how to improve the energy absorption capacity of the lattice structure in the early stage without increasing the weight of the structure is a very challenging task. The method has important significance for the development of a novel energy absorption device, the construction of an anti-impact protection system and the reduction of life and property loss.

Disclosure of Invention

The invention aims to provide a mechanical property adjustable high-ratio energy-absorbing lattice structure based on additive manufacturing, aiming at the problems of the traditional body-centered cubic lattice structure in the process of bearing impact. When the structure bears the working conditions of explosion, impact or collision and the like, the impact energy can be effectively converted into structural plastic strain energy, meanwhile, the damage caused by large initial peak load is avoided, and more convenient, economic and safe guarantee is provided for impact resistance safety protection.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

a high-ratio energy-absorbing lattice structure with adjustable mechanical properties based on additive manufacturing is characterized in that hollow rod elements with variable rod diameters and variable wall thicknesses are connected through end nodes to form basic cells, and the cells are arranged in a periodic array mode to form a lattice structure with high-ratio rigidity and high-ratio energy absorption; the diameter and the wall thickness of the hollow rod element are in smooth transition change so as to avoid the stress concentration phenomenon.

Further, the hollow rod element with the variable rod diameter is continuously and smoothly changed along the axial direction of the hollow rod element, and the changing function obeys a spline function or sine-cosine distribution.

Further, for a variable diameter hollow element, the diameter is greatest at the two ends of the hollow element and smallest at the midpoint.

Further, the wall thickness of the hollow rod element is adjustable along the axial direction of the hollow rod element.

Furthermore, the wall thickness of the hollow rod element is the largest at the connecting section of the hollow rod element, the wall thickness is the smallest at the central point, and the change rule accords with a spline function.

Further, the basic structure of the variable-rod-diameter variable-thickness hollow rod element can be used in a bending-dominated energy absorption structure with a rhombohedral, face-centered cubic or body-centered cubic configuration.

Furthermore, according to the actual use requirement, the cell elements are replicated in the array along the x, y and z axial directions of the space to form a body-centered cubic lattice structure with adjustable and controllable mechanical properties.

Further, the hollow rod element is divided into a constant rod diameter hollow rod element for replacing the variable rod diameter hollow rod element, wherein the constant rod diameter is that the diameter of the hollow rod element is kept constant along the length direction of the hollow rod element.

Compared with the prior art, the invention has the beneficial effects that:

1. the body-centered cubic lattice structure can be used as a safety protection system for bearing explosion, impact, strong collision and the like as a lattice structure with high specific strength, specific rigidity and impact resistance, and is widely applied to impact-resistant energy absorption systems in the engineering protection fields of aerospace, ships, automobiles and the like or explosion-resistant safety protection devices of nuclear energy equipment and naval vessel structures.

2. The body-centered cubic lattice structure can avoid the initial peak load generated when other traditional lattice structures bear impact load, and reduce the serious initial damage to the protected structure. Compared with the traditional body-centered cubic lattice structure, the body-centered cubic lattice structure disclosed by the invention can greatly improve the energy absorption capacity of the structure on the premise of equal quality, and provides a safer guarantee for the structure and the safety protection of a human body.

3. The body-centered cubic lattice structure can be independently used as a supporting structure for bearing force and absorbing energy, and can also be used as a porous filling material to be filled into an energy absorbing device. Meanwhile, the distribution of the transverse cells can be adjusted according to the impact load, the expansion number of the longitudinal cells can be adjusted according to the impact energy, so that different energy absorption requirements can be met, and the adjustable and flexible vertical type solar cell array has better adjustability and flexibility.

Drawings

FIG. 1 is a perspective view of a single rod element of a representative cell of the lattice structure of the present invention;

FIG. 2 is a front view of a representative cell of the lattice structure of the present invention;

FIG. 3 is a perspective view of a representative cell of the lattice structure of the present invention;

FIG. 4 is a perspective view of the lattice structure of the present invention;

FIG. 5 is a schematic view of the thickening of the element portion of the present invention;

FIG. 6 is a graph of a finite element result analysis of a conventional body centered cube and a lattice structure of the present invention under compressive loading;

FIG. 7 is a graph of comparative analysis of load and energy absorption for a lattice structure with variable rod diameter under variable and constant thickness of rod elements;

FIG. 8 is a graph of load contrast and energy absorption contrast analysis of a constant pole diameter lattice structure at variable and constant thicknesses of the pole elements.

Detailed Description

The invention will be described in detail below with reference to the accompanying drawings and examples, which are described below with reference to the drawings and are intended to illustrate the novel hollow rod lattice structure of the present invention and should not be construed as limiting the invention.

The invention provides a high-ratio energy-absorbing lattice structure with adjustable mechanical property based on additive manufacturing, which is a body-centered cubic structure as shown in figure 4. The lattice structure of the embodiment of the present invention will be described in detail with reference to fig. 1 to 5. According to the embodiment of the invention, as shown in the attached figure 1, the rod element is the smallest repeating unit of a body-centered cubic lattice structure, namely a hollow rod element, and is divided into a constant rod diameter and a variable rod diameter. The diameter of the rod element with the constant rod diameter is unchanged along the axial direction, the diameter of the rod element with the variable rod diameter is continuously changed along the axial direction, the change trend obeys a spline curve or a trigonometric function, the diameters of the two ends of the rod element are the largest, and the diameter of the center of the rod element is the smallest. The hollow rod elements shown in fig. 1 are duplicated, symmetrical and connected to form the smallest representative unit, i.e., cell, of the lattice structure, as shown in fig. 2 and 3. The cell element is a basic unit of a body-centered cubic lattice structure, and the body-centered cubic lattice structure with adjustable mechanical properties and adopting hollow rod elements can be formed through array expansion in 3 directions according to actual impact energy and load requirements, as shown in figure 4.

Preferably, the representative cell element of the lattice structure of the body-centered cubic is formed by connecting a plurality of hollow rod elements connecting the corner points and the central point of the body-centered cubic, so as to realize light weight design. Wherein, the 8 hollow rod elements forming the representative cell element have the same size and dimension, and the wall thickness of the hollow rod elements is kept unchanged along the axial direction of the hollow rod elements.

Preferably, the wall thickness of the hollow rod element, which is the smallest repeating unit in the present invention, can be continuously and smoothly changed, the changing function follows a spline curve, the wall thickness at the two ends of the hollow rod element is the largest, the wall thickness at the center of the hollow rod element is the smallest, as shown in fig. 5, the gray contour line represents the constant thickness, and the black contour line represents the variable thickness design. The minimum wall thickness should not be too small to ensure the necessary strength requirements.

The body-centered cubic lattice structure can be copied and array-expanded along three squares of an x axis, a y axis and a z axis on the basis of a representative cell element to form a porous light lattice structure with a larger scale and adjustable performance so as to improve the strength and the energy absorption efficiency of the material structure.

The principle of the invention is as follows: the body-centered cubic lattice structure increases the bending rigidity of the whole structure by enhancing the rigidity of the single hollow rod element, and improves the energy absorption capacity of the whole structure by increasing the number of plastic hinges in the deformation process of the single hollow rod element. When the body-centered cubic lattice structure is under the action of impact load, the whole body-centered cubic lattice structure is in a uniform compression state, and external force work or kinetic energy is converted into strain energy of the body-centered cubic lattice structure through permanent plastic deformation of the material so as to reduce the impact kinetic energy and the impact load and effectively protect the life safety of compact equipment and personnel.

The energy absorption characteristics of the body-centered cubic lattice structure of the present invention when subjected to compressive loads are described below in terms of finite element software Ls-dyna software. The body-centered cubic lattice structure is positioned between two steel plates, the lower steel plate is fixed, the upper steel plate moves downwards uniformly, and the body-centered cubic lattice structure adopting the hollow rod elements in the embodiment is continuously compressed. The length, width and height of each cell element of the body-centered cubic lattice structure of the embodiment are all 25mm, the number of arrays in each direction is 3, and the size of the lattice structure is 75mm multiplied by 75mm; the wall thickness of the hollow rod elements of the body-centered cubic lattice structure is 0.6mm. When the hollow constant-pole-diameter cellular lattice structure bears low-speed impact load, the whole structure is uniformly pressed to generate a stable buckling mode, and as can be seen from a load-displacement curve shown in the attached figure 6, the energy-absorbing platform force is improved by about 50% in the hollow constant-pole-diameter cellular lattice structure compared with the traditional solid pole element under the condition of the same mass, and the energy-absorbing platform force is improved by 200-300% in the hollow variable-pole-diameter cellular lattice structure compared with the traditional solid pole element lattice structure. Therefore, compared with the traditional body-centered cubic lattice structure, the body-centered cubic lattice structure has no initial load, obviously improves the platform force, further increases the specific energy absorption of the lattice structure, and realizes better lightweight design. As shown in fig. 7 and 8, the energy-absorbing platform force and energy-absorbing effect of the hollow variable-rod-diameter lattice structure and the hollow constant-rod-diameter lattice structure under the condition that the thickness is kept constant and the thickness is continuously changed are compared and analyzed, and it can be known from the figure that the energy-absorbing platform force and specific energy absorption of the structure can be continuously improved through the reasonable distribution design of the thickness, and the capability of absorbing impact energy by plastic deformation of materials is maximally utilized.

The above examples are provided for the purpose of describing the invention only, and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications can be made without departing from the spirit and principles of the invention, and are intended to be within the scope of the invention.

Claims

1. The utility model provides a mechanical properties adjustable high ratio energy-absorbing lattice structure based on additive manufacturing which characterized in that: in order to realize lightweight design, hollow rod elements with variable rod diameters and variable wall thicknesses are connected through end nodes to form basic cells, and the cells are periodically arrayed to form a lattice structure with high specific stiffness and high specific energy absorption; the diameter and the wall thickness of the hollow rod element are in smooth transition change so as to avoid the stress concentration phenomenon.

2. The additive manufacturing-based mechanical property tunable high ratio energy absorbing lattice structure of claim 1, wherein: the diameter of the hollow rod element with the variable rod diameter is continuously and smoothly changed along the axial direction of the hollow rod element, and the changing function follows a spline function or sine and cosine distribution.

3. The mechanical property tunable high ratio energy absorbing lattice structure based on additive manufacturing of claim 2, wherein: for a variable diameter hollow rod element, the diameter is greatest at both ends of the hollow rod element and smallest at the midpoint.

4. The additive manufacturing-based mechanical property tunable high ratio energy absorbing lattice structure of claim 1, wherein: the wall thickness of the hollow rod element is adjustable along the axial direction of the hollow rod element.

5. The additive manufacturing-based mechanical property tunable high ratio energy absorbing lattice structure of claim 4, wherein: the wall thickness of the hollow rod element is the largest at the connecting section of the hollow rod element, the wall thickness is the smallest at the central point, and the change rule accords with a spline function.

6. The additive manufacturing-based mechanical property tunable high ratio energy absorbing lattice structure of claim 1, wherein: the basic structure of the variable-rod-diameter and variable-thickness hollow rod element can be used in a bending-dominant energy absorption structure with a rhombic dodecahedron, a face-centered cube and a body-centered cube configuration.

7. The additive manufacturing-based mechanical property tunable high ratio energy absorbing lattice structure of claim 1, wherein: according to practical use needs, the cell elements are duplicated in the array along the directions of x, y and z axes of the space to form a body-centered cubic lattice structure with adjustable mechanical properties.

8. The mechanical property tunable high ratio energy absorbing lattice structure based on additive manufacturing of claim 1, wherein: the hollow rod element is divided into constant rod diameter and used for replacing the hollow rod element with the variable rod diameter, wherein the constant rod diameter is that the diameter of the hollow rod element is kept constant along the length direction of the hollow rod element.