Processing method based on gradient multi-cell lattice structure
Technical Field
The invention belongs to the field of energy absorption structures for automobiles, and particularly relates to a processing method based on a gradient multi-cell lattice structure.
Background
When the multi-cell structure bears external load, the multi-cell structure can generate large plastic deformation due to the existence of a large number of holes, and has strong energy absorption capacity. When the deformation range is smaller, linear elastic deformation which is mainly caused by cell wall bending or cell surface stretching occurs, and with the increase of deformation, the cell collapses through a deformation mechanism corresponding to elastic bending, plastic hinge formation and even brittle fracture, but the bearing capacity is not obviously lost due to the damage of the cell, and a large strain range is maintained under a more stable stress value. When the cells are almost completely collapsed and the cell walls are in contact with each other, the mechanical behavior of the compacted material is exhibited.
According to the existing research, when the lattice structure is subjected to load, the load born by the parts of the lattice structure is not completely the same, and particularly the lattice structure is influenced by the processing technology, so that the parts firstly fail, and finally the whole lattice structure fails in various modes. Common structures are shown in fig. 1, and the common structures are all made of the same wall thickness, so that the mechanical properties of the structures are not fully exerted, and the wall thickness between the regions is changed, so that the wall thickness between the regions presents a gradient change trend. Under the axial and small-angle collision, the energy absorption capacities of the gradient structure and the uniform structure are not greatly different, but the energy absorption of the gradient structure is obviously higher than that of the uniform structure along with the increase of the collision angle, and the gradient structure has better energy absorption characteristic in the oblique collision;
but conventional processes are difficult to implement. Chinese patent CN112248956A discloses a "mixed gradient cage energy absorption structure based on multiple working conditions and its processing method", which adopts powder laser sintering to process layer by layer, but the premise of this technology is that the three-dimensional data of the object is available, and the laser beam concentration and penetration ability is small, which can be limited by the conditions of small area and thin slice product, the application range is narrow, and is not suitable for the requirement of mass production.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a processing method based on a gradient multi-cell lattice structure.
The technical scheme of the invention is as follows:
a processing method based on a gradient multi-cell lattice structure comprises the following steps:
step S1: firstly, determining a cell structure in a multi-cell lattice structure and whether connecting arms exist among cell bodies, and if the connecting arms exist, determining the form of the connecting arms, and further designing a multi-cell lattice structure model with equal thickness;
step S2: determining a gradient area for dividing the thickness of a cell body according to the stress distribution condition of the multi-cell lattice structure with the thickness when different loads are applied, and further designing a gradient multi-cell lattice structure model;
step S3: the required types and the quantity of various types of plug-in board sheets are split according to the quantity of different gradient areas of the gradient multi-cell lattice structure model, and notches in opposite directions are respectively machined on the two plug-in board sheets for assembly;
step S4: selecting materials to prepare a splicing plate sheet;
step S5: assembling the splicing plates according to the gradient multi-cell lattice structure model, and fixing the splicing plates at the positions of the notches.
Preferably, the gradient multi-cell lattice structure model is divided into N areas in the transverse direction and the longitudinal direction, the wall thickness of the cell elements in each area is the same, the wall thicknesses of the cell elements in two adjacent areas are distributed in a gradient manner, and if connecting arms are arranged, the connecting arms between the two adjacent areas are in a step shape.
Preferably, the depth of the notch is half of the width of the plug sheet.
Preferably, the width of the notch is the maximum thickness of the cell walls in the column direction area.
Preferably, the material in step S4 may be steel or a composite material.
In the present invention, when the material in step S4 is steel, brazing may be selected for the fixing process; when the material in step S4 is a composite material, the fixing treatment with a resin adhesive may be selected.
The invention has the following beneficial effects:
the invention provides a processing method based on a gradient multi-cell lattice structure, which can quickly, simply and feasibly realize the processing of the gradient multi-cell lattice structure and is beneficial to the application of the gradient multi-cell lattice structure of different base materials; the production period is short, and compared with other processing methods, the method is suitable for mass production.
Drawings
Other objects and results of the present invention will become more apparent and more readily appreciated as the same becomes better understood by reference to the following description taken in conjunction with the accompanying drawings. In the drawings:
FIG. 1 is a diagram of a conventional uniform-thickness multi-cell lattice structure model;
FIG. 2 is a diagram showing a structure of a cell body in the embodiment;
FIG. 3 is a cross-sectional view of a cell body in an embodiment;
FIG. 4 is a diagram showing a model of the multi-cell lattice structure in the example;
FIG. 5 is a schematic diagram of a 3X 3 gradient multi-cell lattice structure in example;
FIG. 6 is a reference structure of steel;
FIG. 7 is a partial structure view of the socket plate A in the embodiment;
FIG. 8 is a partial view of three other types of connector strips according to the exemplary embodiment;
fig. 9 is an assembly diagram of the plug sheet a and the plug sheet B in the embodiment;
fig. 10 is an assembly diagram of the plug sheet a and the plug sheet C in the embodiment;
fig. 11 is an assembly diagram of the plug sheet a and the plug sheet D in the embodiment;
FIG. 12 is a partial block diagram of FIG. 9;
FIG. 13 is a second partial block diagram of FIG. 9;
FIG. 14 is an isometric view of a 3X 3 gradient multicellular lattice structure in an example;
FIG. 15 is a front view of FIG. 14;
fig. 16 is a top view of fig. 14.
Detailed Description
In order to make the technical solutions and advantages thereof better understood by those skilled in the art, the present application is described in detail below with reference to the accompanying drawings, but the present application is not limited to the scope of the present invention.
Example (b):
referring to the energy absorbing structure of CN112248956A, it was determined that the cell structure of the multi-cell lattice structure of the present embodiment is shown in fig. 2, the cross-sectional view of the cell structure is shown in fig. 3, and the cross-sectional geometry of the cell structure is shown in table 1 below;
TABLE 1
The front view of the uniform-thickness multi-cell lattice structure model is shown in fig. 4, and is divided into three layers in the Z direction, each layer comprises three regions, and is divided into nine regions in total, and the gradient division condition is as follows: taking the upper left cell body of the Z-direction forming surface and the X-direction forming surface as a starting point, changing along the X-direction negative gradient, changing along the Z-direction positive gradient, and obtaining a gradient multi-cell lattice structure model, wherein the thickness difference of the cell body is equal between areas;
in this embodiment, four kinds of the plug sheet A, B, C, D are required (if there are N regions in the transverse direction and the longitudinal direction, N +1 kinds of the plug sheet are required), wherein the plug sheet a has nine different gradient regions, and the other three kinds of the plug sheet have three different gradient regions;
processing by taking a 3 x 3 gradient multi-cell lattice structure model (see fig. 5) as an example, selecting a steel plate as a preparation material, and preparing a splicing plate sheet in a linear cutting machining mode (if a composite material is selected, adopting an engraving machine, and matching a special engraving tool bit for the composite material on the engraving machine);
when cutting is carried out, the joint of the bottom surface of the top layer cell body and the top surface of the middle layer cell body is designed to take the thickness of the top surface of the middle layer cell body as the connecting thickness; similarly, the joint between the bottom surface of the middle layer cell body and the top surface of the bottom layer cell body is designed to use the thickness of the top surface of the bottom layer cell body as the connection thickness (see fig. 12); the central lines of the two connecting arms with different wall thicknesses are a horizontal line in the transverse direction; in the longitudinal direction, the bottoms of the connecting arms of two different wall thicknesses lie in the same plane (see fig. 13).
Referring to FIG. 6: determining geometric parameters for designing by taking the face formed by the Z direction and the X direction in the figure 5 to face upwards, selecting proper quantity of steel plates with consistent cutting specifications or welding the steel plates as a group according to types to be clamped on a perforating machine for perforating, so that regular hexagonal holes are alternately distributed on the steel plates in rows, processing notches penetrating through the regular hexagons from the middle position of the upper ends of the long rows of the regular hexagons, wherein the depth of each notch is half of the width of each splicing plate piece, the width of each notch of the splicing plate piece A is in a descending trend from left to right (shown in figure 7), then fixing the steel plate group on a wire cutting machine, drawing by using drawing software, and guiding a drawing result into a wire cutting controller for cutting;
the method comprises the steps of determining geometric parameters to design by facing upwards in the Z direction and the Y direction in fig. 5, selecting proper number of steel plates with consistent cutting specifications or welding the steel plates as a group according to types to clamp the steel plates on a perforating machine for perforating, so that regular hexagonal holes are alternately distributed on the steel plates in rows, and the wall thickness of an inserting plate B, C, D is increased from top to bottom in the Z direction, wherein a notch penetrating through the regular hexagon is formed in the middle position of the lower end of a long row of regular hexagons, the depth of the notch is half of the width of the inserting plate (see fig. 8), and the width of the notch is the same as the maximum wall thickness in the corresponding area of the inserting plate A, so that the notch can be cut with the notch of the inserting plate A;
the plug sheet B, C, D corresponds to three large areas of the plug sheet a in the row direction (if the a plates have N large areas in the row direction, N plates are needed to correspond to the large areas), and the sizes of the single cell bodies in the plug sheet a are different except for the width of the notch, and the sizes of the cell bodies correspond to the sizes of the cell bodies in the areas of the plug sheet a in the row direction;
because the molybdenum wire of the wire cutting machine generates heat in the cutting process, the molybdenum wire needs to be cooled by working fluid, so that oil stains are left on the surface of the splicing plate after the cutting is finished, and the machined splicing plate needs to be cleaned to remove the oil stains;
referring to FIGS. 9-11: the connection of the notches between the plug-in plates is realized by adopting a brazing process (the notches of the composite material plates are bonded by adopting liquid resin adhesive): firstly, smearing brazing filler metal to the notch of the plug board piece a (namely, including nine areas), after even smearing, respectively assembling the plug board piece B, C, D and the plug board piece a at corresponding positions (note that the direction of the notch is opposite during assembly), and finishing the assembly as shown in fig. 14-16;
then, selecting proper temperature for heat preservation treatment in a high-temperature high-pressure gas quenching furnace according to requirements; and finally, cooling along with the furnace to obtain the gradient multi-cell lattice structure (after the composite material plate is assembled and put into an insulation can, adjusting the temperature, preserving the heat, and naturally cooling to obtain the composite material gradient multi-cell lattice structure).
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.