CN118504349A - Space lattice modeling method and system based on regional boundary grid model cutting - Google Patents
Space lattice modeling method and system based on regional boundary grid model cutting Download PDFInfo
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Abstract
The invention provides a space lattice modeling method and a system based on regional boundary grid model cutting, wherein the method comprises the following steps: generating an inner surface boundary grid model of the lattice filling cavity according to the target structure model; establishing a regular space region containing an inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters; extracting rays from each lattice node in the regular space region along a plurality of different vector directions, and judging the position relationship between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays extracted from each lattice node and the inner surface boundary grid model; judging the position relationship between each dot matrix rod and the inner surface boundary grid model according to the position relationship between each dot matrix node and the inner surface boundary grid model; and cutting the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model to obtain a space lattice model filled in the cavity of the target structure model. The technical scheme of the invention is applied to solve the technical problems of large model operation amount, large scale and serious limitation by geometric shapes in the prior art.
Description
Technical Field
The invention relates to the technical field of finite element simulation modeling and geometric modeling of lattice structures, in particular to a space lattice modeling method and system based on regional boundary grid model cutting.
Background
The lattice structure is a lightweight filling structure which is used for being filled in the cavity inside the bearing structure and can effectively enhance the rigidity of the structure. In combination with advanced manufacturing methods such as additive manufacturing, lattice structures have been successfully applied to thin-wall bearing and dimensional structures, and typical applications are as follows: the thin-wall airfoil structure of the aircraft fills the lattice between the upper skin and the lower skin, realizes the rapid forming of the lattice structure through the additive manufacturing process, can greatly improve the efficiency in the additive manufacturing process while realizing the improvement of the structural rigidity and strength performance, and realizes the light weight and low cost of the structure.
At present, the existing space lattice modeling method comprises two modeling methods, namely a modeling method based on geometric model Boolean operation, the method is mainly used for geometric modeling and additive manufacturing, special geometric modeling software is required to be used for Boolean operation, the operation amount and the model scale are large, and a finite element simulation model is difficult to directly generate; the other is a modeling method based on finite element body grids, which needs to generate three-dimensional body grids in a lattice filling space, then generate a rod model of the lattice according to body grid information, and the method is severely limited by geometric shapes, so that for complex engineering structures, a lattice model which is uniformly distributed is difficult to generate.
In order to solve the problem of rapid lattice modeling of complex geometric structures in engineering, the invention provides a lattice modeling method which does not depend on geometric and volume grids, the method takes an inner surface boundary grid model of a filling area in a structure as input to rapidly generate a space lattice model, the generated model can be directly applied to finite element simulation analysis and optimization design of a lattice structure, and meanwhile, the model file is further converted into a data format required by structural design and additive manufacturing, so that the method can be applied to fine modeling and additive manufacturing of the structure.
Disclosure of Invention
The invention provides a space lattice modeling method and a space lattice modeling system based on regional boundary grid model cutting, which can solve the technical problems of large model operand, large scale and serious limitation by geometric shapes in the prior art.
According to an aspect of the present invention, there is provided a space lattice modeling method based on region boundary mesh model clipping, the method comprising:
S1, generating an inner surface boundary grid model of a lattice filling cavity according to a target structure model;
S2, establishing a regular space region containing an inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
S3, extracting rays from each lattice node in the regular space area along a plurality of different vector directions, and judging the position relation between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays extracted from each lattice node and the inner surface boundary grid model;
S4, judging the position relation between each dot matrix rod and the inner surface boundary grid model according to the position relation between each dot matrix node and the inner surface boundary grid model;
S5, cutting the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model to obtain a space lattice model filled in the cavity of the target structure model.
Further, the regular space region is a hexahedron, sphere or cylinder.
Further, the preset lattice distribution parameters comprise lattice initial positions, lattice types, lattice copying directions and lattice geometric parameters.
Further, S3 includes:
S31, determining a vector direction;
s32, dividing the regular space region into a plurality of original subdomains by using a plane parallel to the determined vector direction;
S33, expanding each surface of each original subdomain outwards along the normal direction by a preset distance to obtain a plurality of corresponding expansion subdomains;
S34, traversing each face grid of the surface boundary grid model and each lattice node in the regular space region to classify the face grid and each lattice node into each expansion sub-domain;
S35, extracting rays from each lattice node in the regular space area along the determined vector direction;
S36, changing vector directions, and repeating the steps S32 to S35 to obtain the number of intersection points of rays led out by each dot matrix node in each expansion subdomain and the face grids in the corresponding expansion subdomain under each vector direction respectively;
S37, judging the position relation between each lattice node and the inner surface boundary grid model according to the number of the intersection points obtained in the S36.
Further, S37 includes:
Judging lattice nodes with 0 intersection points or even intersection points as the outside of the inner surface boundary grid model;
all lattice nodes with odd number of intersection points are judged to be inside the inner surface boundary grid model.
Further, S4 includes:
when two lattice nodes of the lattice bar are outside the inner surface boundary grid model, judging that the lattice bar is outside the inner surface boundary grid model;
when two lattice nodes of the lattice bar are both inside the inner surface boundary grid model, judging that the lattice bar is inside the inner surface boundary grid model;
When two lattice nodes of the lattice bar are respectively positioned inside and outside the inner surface boundary grid model, the lattice bar is judged to span the inner surface boundary grid model.
Further, S5 includes:
S51, when the dot matrix rod is in the inner surface boundary grid model, reserving the dot matrix rod and two dot matrix nodes of the dot matrix rod;
S52, deleting the lattice bar when the lattice bar is outside the inner surface boundary lattice model, judging whether two lattice nodes of the lattice bar are connected with other lattice bars, deleting the lattice node when the lattice node is not connected with other lattice bars, deleting the lattice node when the lattice node is connected with the lattice bar outside the inner surface boundary lattice model, and retaining the lattice node when the lattice node is connected with the lattice bar crossing the inner surface boundary lattice model;
S53, when the lattice bar crosses the inner surface boundary grid model, calculating to obtain the crossing intersection point of the directional line segment between two lattice nodes of the lattice bar and the inner surface boundary grid model, further calculating to obtain the distance between the lattice node positioned inside the inner surface boundary grid model on the lattice bar and the crossing intersection point, judging whether the distance is smaller than or equal to a preset bar length tolerance value, if so, replacing the lattice node positioned inside the inner surface boundary grid model on the lattice bar by the crossing intersection point, deleting the lattice bar and the lattice node positioned outside the inner surface boundary grid model on the lattice bar, and if not, replacing the lattice node positioned outside the inner surface boundary grid model on the lattice bar by the crossing intersection point.
Further, in S53, when the lattice bar crosses the inner surface boundary grid model, calculating to obtain a crossing point between the directional line segment between two lattice nodes of the lattice bar and the inner surface boundary grid model, and further calculating to obtain a distance between the lattice node located inside the inner surface boundary grid model on the lattice bar and the crossing point includes:
performing grid discretization on the inner surface boundary grid model to obtain a plurality of plane boundary grids;
And calculating the crossing point between the directional line segment between two lattice nodes of the lattice bar and the corresponding plane boundary grid, and further calculating the distance between the lattice node positioned in the plane boundary grid on the lattice bar and the crossing point.
Further, the cross-boundary intersection point of the directed line segment between two lattice nodes of the lattice bar and the corresponding plane boundary grid is calculated through the following formula, and then the distance between the lattice node positioned in the plane boundary grid on the lattice bar and the cross-boundary intersection point is calculated:
a(x'-x0)+b(y'-y0)+c(z'-z0)＝0，
In the above-mentioned method, the step of, A normal vector representing a plane boundary grid, (x 0,y0,z0) a spatial coordinate of any known point on the plane boundary grid, (x ', y ', z ') a spatial coordinate of any point on the plane boundary grid, (x a,ya,za) a spatial coordinate of a lattice node on the lattice bar that is located inside the plane boundary grid, (x b,yb,zb) a spatial coordinate of a lattice node on the lattice bar that is located outside the plane boundary grid, (x, y, z) a spatial coordinate of a cross-boundary point, and t a distance between (x a,ya,za) and (x, y, z).
According to another aspect of the invention, there is provided a space lattice modeling system based on region boundary grid model clipping, the system comprising an initial lattice filling module, a position relationship judging module and a clipping module;
The initial lattice filling module is used for generating an inner surface boundary grid model of the lattice filling cavity according to the target structure model; establishing a regular space region containing an inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
The position relation judging module is used for leading out rays along a plurality of different vector directions for each lattice node in the regular space area, and judging the position relation between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays led out by each lattice node and the inner surface boundary grid model; judging the position relationship between each dot matrix rod and the inner surface boundary grid model according to the position relationship between each dot matrix node and the inner surface boundary grid model;
The clipping module is used for clipping the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model so as to obtain a space lattice model filled in the cavity of the target structure model.
By applying the technical scheme of the invention, a space lattice modeling method and a system based on regional boundary lattice model cutting are provided, and the method firstly generates an inner surface boundary lattice model of a cavity region of a lattice to be filled; secondly, generating a regular area containing boundary grids of the inner surface of the cavity area and generating a lattice model, wherein the lattice model can be any required pattern; then judging the position relationship between the lattice nodes and the lattice rods in the lattice model and the boundary grids of the inner surface of the cavity area by a ray method; and finally, cutting the lattice model according to the position relation to realize the final creation of the space lattice model. The method gives consideration to the efficiency, precision and flexibility of lattice modeling, can rapidly generate a space lattice filling model in a cavity in a structure, is a novel efficient and practical modeling method, and has been successfully applied to finite element simulation analysis rapid modeling, simplified lattice geometric modeling and structure optimization design of a lattice engineering structure and subsequent lattice structure additive manufacturing.
Drawings
The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 illustrates a flow diagram of a spatial lattice modeling method based on region boundary mesh model clipping, provided in accordance with a specific embodiment of the present invention;
FIG. 2 illustrates a block flow diagram of a positional relationship determination provided in accordance with a specific embodiment of the present invention;
FIG. 3 illustrates a block flow diagram of lattice clipping provided in accordance with a specific embodiment of the present invention;
FIG. 4 is a full flow diagram of a spatial lattice modeling method based on region boundary mesh model clipping, provided in accordance with a specific embodiment of the present invention;
FIG. 5 illustrates a schematic diagram of lattice generation, classification, and clipping provided in accordance with a specific embodiment of the present invention;
FIG. 6 is a schematic diagram showing a condition for judging the positional relationship of lattice nodes according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing a condition for judging the positional relationship of a lattice bar according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a space lattice model according to a first embodiment of the present invention;
FIG. 9 shows simulation analysis results obtained by simulation using the spatial lattice model of FIG. 8;
FIG. 10 shows a partial enlarged view of the simulation analysis result in FIG. 9;
FIG. 11 is a schematic diagram of a space lattice model according to a second embodiment of the present invention;
FIG. 12 illustrates a schematic diagram of a lattice model with multiple variable thickness fill regions provided in accordance with a specific embodiment of the present invention;
FIG. 13 shows a partial enlarged view of FIG. 12;
FIG. 14 illustrates a schematic diagram of a spatial lattice modeling system based on region boundary mesh model clipping, provided in accordance with a specific embodiment of the present invention.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
As shown in fig. 1, according to an embodiment of the present invention, there is provided a spatial lattice modeling method based on region boundary mesh model clipping, the method including:
S1, generating an inner surface boundary grid model of a lattice filling cavity according to a target structure model;
S2, establishing a regular space region containing an inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
S3, extracting rays from each lattice node in the regular space area along a plurality of different vector directions, and judging the position relation between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays extracted from each lattice node and the inner surface boundary grid model;
S4, judging the position relation between each dot matrix rod and the inner surface boundary grid model according to the position relation between each dot matrix node and the inner surface boundary grid model;
S5, cutting the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model to obtain a space lattice model filled in the cavity of the target structure model.
By applying the configuration mode, a space lattice modeling method based on area boundary grid model cutting is provided, and the method firstly generates an inner surface boundary grid model of a cavity area of a lattice to be filled; secondly, generating a regular area containing boundary grids of the inner surface of the cavity area and generating a lattice model, wherein the lattice model can be any required pattern; then judging the position relationship between the lattice nodes and the lattice rods in the lattice model and the boundary grids of the inner surface of the cavity area by a ray method; and finally, cutting the lattice model according to the position relation to realize the final creation of the space lattice model. The method gives consideration to the efficiency, precision and flexibility of lattice modeling, can rapidly generate a space lattice filling model in a cavity in a structure, is a novel efficient and practical modeling method, and has been successfully applied to finite element simulation analysis rapid modeling, simplified lattice geometric modeling and structure optimization design of a lattice engineering structure and subsequent lattice structure additive manufacturing. Compared with the prior art, the technical scheme of the invention can solve the technical problems of large model operand, large scale and serious limitation by geometric shapes in the prior art.
In the embodiment of the invention, an inner surface boundary grid model is generated based on the extracted inner surface information of the lattice filling space region of the target structure model, if the target structure is divided into finite element grids, inner cavity surface information is extracted to establish a surface grid, if the structure is only provided with a geometric model, finite element surface grid division is firstly carried out on the inner surface region of the geometric model, and also a boundary grid model can be generated by carrying out format conversion on files such as STL and the like. The generated lattice fills the inner surface boundary grid model of the cavity and is used as the input of the subsequent lattice filling calculation.
In practical implementation, the inner surface boundary grid model is a closed space as much as possible, so that special situations such as generation errors and the like caused by the fact that a lattice structure is located in an unsealed area can be avoided. Meanwhile, when the target structure is complex, the target structure can be decomposed into a plurality of sub-models, then an inner surface boundary grid model is respectively established for each sub-model, and then lattice filling and cutting are carried out on the inner surface boundary grid model of each sub-model according to the steps from S2 to S5. As a specific embodiment of the present invention, for a geometric model of an implementation object (target structure), inner surface geometric models of n inner cavity regions to be filled with a lattice are extracted, a closed curved surface is formed by repairing the geometric model, surface mesh division is performed on the closed curved surface, n closed curved surface mesh models, that is, inner surface boundary mesh models, are obtained, and in a subsequent step, the n closed curved surface mesh models are processed in series or in parallel.
Further, the shape of the regular space region covering the inner surface boundary grid of the lattice filling cavity is determined according to the shape of the target structure and the lattice distribution characteristics (lattice direction, lattice density and the like), and when the method is applied practically, the space contour characteristics, such as the length, width, height and the like of the designated direction, are extracted according to the inner surface grid model information of the cavity structure of the lattice to be filled. According to the layout requirement of the required filling lattice, a regular area containing the grid model of the inner surface of the cavity is generated, and the lattice with the specified rule is filled in the area. The regular space region can be hexahedron, sphere or cylinder, for example, for periodic cyclic lattice, cuboid region can be selected, and for gradient lattice, cylinder can be used, thus facilitating automatic generation of lattice. Referring to the embodiment of fig. 5, a cuboid is used as a regular space region, and in actual operation, the cuboid may not be actually generated, but only serves as a termination boundary for periodic replication of the lattice, and in the regular cuboid, preset lattice distribution parameters including an initial position of the lattice, a lattice type, a lattice replication direction and geometric parameters of the lattice are given, so as to generate a lattice grid model covering the cuboid space. The filled lattice can be of any desired type, with the lattice filling of regular spatial regions being accomplished by a program. Since the dot matrix filling is performed in a regular area, it is very easy to realize by programming.
Referring to fig. 6, in the embodiment of the present invention, S37 includes:
Judging lattice nodes with 0 intersection points or even intersection points as the outside of the inner surface boundary grid model;
all lattice nodes with odd number of intersection points are judged to be inside the inner surface boundary grid model.
That is, the lattice nodes filled in the regular region are classified into an inner (including a boundary) type and an outer type according to the positional relationship between the lattice nodes in the lattice model and the inner surface boundary lattice model. In the embodiment of the invention, a ray method is adopted for judgment: the lattice node emits rays along a certain direction, and the lattice node has an odd number of intersection points with the inner surface boundary grid model, namely an inner point, and has 0 intersection points or an even number of intersection points, namely an outer point. In order to avoid the situation of error judgment caused by tangency and the like, rays are respectively calculated along different vector directions according to the geometric characteristics of a space region (for example, vectors in 1-3 different directions), namely, a multi-ray method is adopted, and the type of the node is finally judged according to the number of intersection points calculated each time.
Further, referring to the embodiment of fig. 2, S3 includes:
S31, determining a vector direction;
s32, dividing the regular space region into a plurality of original subdomains by using a plane parallel to the determined vector direction;
S33, expanding each surface of each original subdomain outwards along the normal direction by a preset distance to obtain a plurality of corresponding expansion subdomains;
S34, traversing each face grid of the surface boundary grid model and each lattice node in the regular space region to classify the face grid and each lattice node into each expansion sub-domain;
S35, extracting rays from each lattice node in the regular space area along the determined vector direction;
S36, changing vector directions, and repeating the steps S32 to S35 to obtain the number of intersection points of rays led out by each dot matrix node in each expansion subdomain and the face grids in the corresponding expansion subdomain under each vector direction respectively;
S37, judging the position relation between each lattice node and the inner surface boundary grid model according to the number of the intersection points obtained in the S36.
In other words, in the embodiment of the present invention, a partition search algorithm is adopted to perform a ray method, that is, a plane parallel to a ray direction is used to segment a regular space region, so as to obtain a plurality of subfields, traverse a surface grid and lattice nodes of an inner surface boundary grid model, classify the surface grid and lattice nodes into each subfield, and all or part of grids entering the subfields will be used for traversing search calculation of lattice nodes. By expanding the subfields, a certain proportion of edges between the subfields overlap, i.e. overlap edges are formed, thereby increasing robustness. The ray method calculation is carried out in each sub-domain, so that the node position judgment problem of the complex non-convex curved surface can be rapidly and effectively solved, and the calculation efficiency can be greatly improved. The expansion size of the original subdomain is determined according to practical situations, taking a cube as an example, each side of the original subdomain of the cube extends outwards by 10%, namely each face expands outwards by 10% along the normal direction of the face, and the expansion subdomain of the cube is obtained. In this method, the manner of determining the positional relationship between each lattice node and the inner surface boundary mesh model according to the number of intersection points is the same as that in S37 described above, and will not be described here again.
Referring to fig. 7 again, in the embodiment of the present invention, S4 includes:
when two lattice nodes of the lattice bar are outside the inner surface boundary grid model, judging that the lattice bar is outside the inner surface boundary grid model;
when two lattice nodes of the lattice bar are both inside the inner surface boundary grid model, judging that the lattice bar is inside the inner surface boundary grid model;
When two lattice nodes of the lattice bar are respectively positioned inside and outside the inner surface boundary grid model, the lattice bar is judged to span the inner surface boundary grid model.
That is, the lattice bars with both nodes being external points are marked as external bars, the lattice bars with both nodes being internal points are marked as internal bars, and the lattice bars with one outside and one inside of the two nodes are marked as cross-boundary bars. By the mode, the dot matrix bars are classified, and subsequent cutting operation is facilitated.
Referring to fig. 3 and 5, in an embodiment of the present invention, S5 includes:
S51, when the dot matrix rod is in the inner surface boundary grid model, reserving the dot matrix rod and two dot matrix nodes of the dot matrix rod;
S52, deleting the lattice bar when the lattice bar is outside the inner surface boundary lattice model, judging whether two lattice nodes of the lattice bar are connected with other lattice bars, deleting the lattice node when the lattice node is not connected with other lattice bars, deleting the lattice node when the lattice node is connected with the lattice bar outside the inner surface boundary lattice model, and retaining the lattice node when the lattice node is connected with the lattice bar crossing the inner surface boundary lattice model;
Through the operation steps of S51 and S52, lattice rods (inner rods) and lattice nodes located inside the lattice filling region are preserved; the lattice bars (outer bars) outside the lattice filling area are deleted, and when two nodes of the outer bars are not connected with other lattice bars or other lattice bars connected with the other lattice bars are all outer bars, the nodes connected with the boundary crossing bars are reserved when the nodes of the outer bars have the connected lattice bars belonging to the boundary crossing bars, and then the boundary crossing bars and the two lattice nodes thereof are cut.
S53, when the lattice bar crosses the inner surface boundary grid model, calculating to obtain the crossing intersection point of the directional line segment between two lattice nodes of the lattice bar and the inner surface boundary grid model, further calculating to obtain the distance between the lattice node positioned inside the inner surface boundary grid model on the lattice bar and the crossing intersection point, judging whether the distance is smaller than or equal to a preset bar length tolerance value, if so, replacing the lattice node positioned inside the inner surface boundary grid model on the lattice bar by the crossing intersection point, deleting the lattice bar and the lattice node positioned outside the inner surface boundary grid model on the lattice bar, and if not, replacing the lattice node positioned outside the inner surface boundary grid model on the lattice bar by the crossing intersection point.
That is, for the cross-boundary lattice bar, a directional line segment from the internal lattice node to the external lattice node is made along the cross-boundary bar direction, the intersection point of the directional line segment and the boundary curved surface (the internal surface boundary lattice model) is calculated, and meanwhile, the distance from the internal lattice node to the intersection point is obtained, and the process can realize rapid traversal through a partition search algorithm. In addition, the preset lever length tolerance value is determined according to practical conditions.
In order to realize the partition search calculation of the distance between the cross-boundary intersection point and the internal lattice node, in the embodiment of the present invention, in S53, when the lattice bar crosses the internal surface boundary lattice model, the calculation of the cross-boundary intersection point between the directional line segment between the two lattice nodes of the lattice bar and the internal surface boundary lattice model, and then the calculation of the distance between the lattice node located inside the internal surface boundary lattice model on the lattice bar and the cross-boundary intersection point includes:
performing grid discretization on the inner surface boundary grid model to obtain a plurality of plane boundary grids;
And calculating the crossing point between the directional line segment between two lattice nodes of the lattice bar and the corresponding plane boundary grid, and further calculating the distance between the lattice node positioned in the plane boundary grid on the lattice bar and the crossing point.
That is, the curved surface of the inner surface boundary grid model is subjected to grid discretization to obtain a plurality of facets, namely plane boundary grids, so that the calculation process is simplified into the calculation of the intersection point of the straight line of two points and the plane.
Further, in the embodiment of the invention, the cross-boundary intersection point of the directed line segment between two lattice nodes of the lattice bar and the corresponding plane boundary grid is calculated by the following formula, so that the distance between the lattice node positioned in the plane boundary grid on the lattice bar and the cross-boundary intersection point is calculated:
a(x'-x0)+b(y'-y0)+c(z'-z0)＝0 (1)
In the above-mentioned method, the step of, A normal vector representing a plane boundary grid, (x 0,y0,z0) a spatial coordinate of any known point on the plane boundary grid, (x ', y ', z ') a spatial coordinate of any point on the plane boundary grid, (x a,ya,za) a spatial coordinate of a lattice node on the lattice bar that is located inside the plane boundary grid, (x b,yb,zb) a spatial coordinate of a lattice node on the lattice bar that is located outside the plane boundary grid, (x, y, z) a spatial coordinate of a cross-boundary point, and t a distance between (x a,ya,za) and (x, y, z).
In the above formula, formula (1) is the passing point (x 0,y0,z0), and the normal vector isThe intersection coordinates (x, y, z) and the distance t can be found by combining equations (1) and (2).
In addition, the space lattice modeling method provided by the invention further comprises model checking and outputting after finishing lattice cutting, and specifically comprises the following steps: further checking and adjusting the generated space lattice models of the n closed curved surface models according to modeling requirements, such as merging coincident points, optimizing boundary node distribution or rod trend and the like; outputting the space lattice model (points and rods) into a finite element calculation model format according to the requirement, and performing model checking and subsequent lattice structure simulation analysis in finite element software. If used for geometric modeling, the space lattice model can be output into a file format required by CAD software modeling or additive manufacturing according to modeling requirements.
The effect of the present invention is described in two specific examples, example one: fig. 8 shows a structure with three lattice filling areas, lattice modeling is realized by the method, and fig. 9 and 10 show nonlinear finite element simulation analysis results of the structure, which show that the lattice model established by the method can be directly applied to nonlinear finite element simulation analysis. Example two: fig. 11,12 and 13 show a special-shaped structure with a plurality of variable-thickness lattice filling areas, and rapid modeling of lattice structures with different specifications of the plurality of areas is realized through the invention.
In summary, the overall flow of the spatial lattice modeling method based on region boundary grid model clipping provided by the present invention can refer to the flow chart of fig. 4, and the detailed implementation of each step is described in the foregoing embodiments, which will not be described in detail herein. It will be appreciated by those skilled in the art that this example is only one way to facilitate understanding the spatial lattice modeling method based on region boundary grid model clipping provided in the present invention, and is not limited in any way.
According to another aspect of the invention, there is provided a space lattice modeling system based on region boundary grid model clipping, the system comprising an initial lattice filling module, a position relationship judging module and a clipping module;
The initial lattice filling module is used for generating an inner surface boundary grid model of the lattice filling cavity according to the target structure model; establishing a regular space region containing an inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
The position relation judging module is used for leading out rays along a plurality of different vector directions for each lattice node in the regular space area, and judging the position relation between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays led out by each lattice node and the inner surface boundary grid model; judging the position relationship between each dot matrix rod and the inner surface boundary grid model according to the position relationship between each dot matrix node and the inner surface boundary grid model;
The clipping module is used for clipping the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model so as to obtain a space lattice model filled in the cavity of the target structure model.
In summary, the invention provides a space lattice modeling method and system based on region boundary grid model clipping, which comprises the steps of firstly generating an inner surface boundary grid model of a cavity region of a lattice to be filled; secondly, generating a regular area containing boundary grids of the inner surface of the cavity area and generating a lattice model, wherein the lattice model can be any required pattern; then judging the position relationship between the lattice nodes and the lattice rods in the lattice model and the boundary grids of the inner surface of the cavity area by a ray method; and finally, cutting the lattice model according to the position relation to realize the final creation of the space lattice model. The method gives consideration to the efficiency, precision and flexibility of lattice modeling, can rapidly generate a space lattice filling model in a cavity in a structure, is a novel efficient and practical modeling method, and has been successfully applied to finite element simulation analysis rapid modeling, simplified lattice geometric modeling and structure optimization design of a lattice engineering structure and subsequent lattice structure additive manufacturing. Compared with the prior art, the technical scheme of the invention can solve the technical problems of large model operand, large scale and serious limitation by geometric shapes in the prior art.
Spatially relative terms, such as "above … …," "above … …," "upper surface on … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A spatial lattice modeling method based on region boundary mesh model clipping, the method comprising:
S1, generating an inner surface boundary grid model of a lattice filling cavity according to a target structure model;
S2, establishing a regular space region containing the inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
s3, extracting rays from each lattice node in the regular space region along a plurality of different vector directions, and judging the position relationship between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays extracted from each lattice node and the inner surface boundary grid model;
S4, judging the position relation between each lattice rod and the inner surface boundary grid model according to the position relation between each lattice node and the inner surface boundary grid model;
S5, cutting the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model to obtain a space lattice model filled in the cavity of the target structure model.
2. The method of claim 1, wherein the regular spatial region is a hexahedron, sphere, or cylinder.
3. The method of claim 2, wherein the preset lattice distribution parameters include a lattice initial position, a lattice type, a lattice replication direction, and a lattice geometry.
4. A method according to claim 3, wherein S3 comprises:
S31, determining a vector direction;
S32, dividing the regular space region into a plurality of original subdomains by using a plane parallel to the determined vector direction;
S33, expanding each surface of each original subdomain outwards along the normal direction by a preset distance to obtain a plurality of corresponding expansion subdomains;
S34, traversing each face grid of the surface boundary grid model and each lattice node in the regular space region to classify the face grid and each lattice node into each expansion sub-domain;
S35, extracting rays from each lattice node in the regular space area along the determined vector direction;
S36, changing vector directions, and repeating the steps S32 to S35 to obtain the number of intersection points of rays led out by each dot matrix node in each expansion subdomain and the face grids in the corresponding expansion subdomain under each vector direction respectively;
s37, judging the position relation between each lattice node and the inner surface boundary grid model according to the number of the intersection points obtained in the S36.
5. The method of claim 4, wherein S37 comprises:
Judging lattice nodes with 0 intersection points or even intersection points as the outside of the inner surface boundary grid model;
all lattice nodes with odd number of intersection points are judged to be inside the inner surface boundary grid model.
6. The method of claim 5, wherein S4 comprises:
when two lattice nodes of the lattice bar are outside the inner surface boundary grid model, judging that the lattice bar is outside the inner surface boundary grid model;
when two lattice nodes of the lattice bar are both in the inner surface boundary grid model, judging that the lattice bar is in the inner surface boundary grid model;
when two lattice nodes of the lattice bar are respectively positioned inside and outside the inner surface boundary grid model, judging that the lattice bar spans the inner surface boundary grid model.
7. The method of claim 6, wherein S5 comprises:
S51, when the lattice bar is in the inner surface boundary grid model, reserving the lattice bar and two lattice nodes of the lattice bar;
s52, deleting the lattice bar when the lattice bar is outside the inner surface boundary lattice model, judging whether two lattice nodes of the lattice bar are connected with other lattice bars, deleting the lattice node when the lattice bar is not connected with other lattice bars, deleting the lattice node when the lattice node is connected with the lattice bar outside the inner surface boundary lattice model, and reserving the lattice node when the lattice node is connected with the lattice bar crossing the inner surface boundary lattice model;
And S53, when the lattice bar crosses the inner surface boundary grid model, calculating to obtain a crossing intersection point of a directed line segment between two lattice nodes of the lattice bar and the inner surface boundary grid model, further calculating to obtain a distance between the lattice node positioned in the inner surface boundary grid model on the lattice bar and the crossing intersection point, judging whether the distance is smaller than or equal to a preset bar length tolerance value, if so, replacing the lattice node positioned in the inner surface boundary grid model on the lattice bar by using the crossing intersection point, deleting the lattice bar and the lattice node positioned outside the inner surface boundary grid model on the lattice bar, and if not, replacing the lattice node positioned outside the inner surface boundary grid model on the lattice bar by using the crossing intersection point.
8. The method of claim 7, wherein when the lattice bar crosses the inner surface boundary mesh model, calculating a crossing point between a directional line segment between two lattice nodes of the lattice bar and the inner surface boundary mesh model, and further calculating a distance between a lattice node on the lattice bar located inside the inner surface boundary mesh model and the crossing point in S53 includes:
Performing grid discretization on the inner surface boundary grid model to obtain a plurality of plane boundary grids;
And calculating the crossing point between the directional line segment between two lattice nodes of the lattice bar and the corresponding plane boundary grid, and further calculating the distance between the lattice node positioned in the plane boundary grid on the lattice bar and the crossing point.
9. The method of claim 8, wherein the distance between the dot matrix node on the dot matrix bar located inside the plane boundary grid and the cross-boundary intersection point is calculated by calculating the cross-boundary intersection point of the directed line segment between two dot matrix nodes of the dot matrix bar and the corresponding plane boundary grid by the following formula:
a(x'-x0)+b(y'-y0)+c(z'-z0)＝0，
In the above-mentioned method, the step of, A normal vector representing a plane boundary grid, (x 0,y0,z0) a spatial coordinate of any known point on the plane boundary grid, (x ', y ', z ') a spatial coordinate of any point on the plane boundary grid, (x a,ya,za) a spatial coordinate of a lattice node on the lattice bar that is located inside the plane boundary grid, (x b,yb,zb) a spatial coordinate of a lattice node on the lattice bar that is located outside the plane boundary grid, (x, y, z) a spatial coordinate of a cross-boundary point, and t a distance between (x a,ya,za) and (x, y, z).
10. The space lattice modeling system based on the regional boundary grid model clipping is characterized by comprising an initial lattice filling module, a position relation judging module and a clipping module;
The initial lattice filling module is used for generating an inner surface boundary grid model of the lattice filling cavity according to the target structure model; establishing a regular space region containing the inner surface boundary grid model according to the shape of the target structure, and filling the regular space region with a lattice according to preset lattice distribution parameters;
The position relation judging module is used for leading out rays along a plurality of different vector directions for each lattice node in the regular space region, and judging the position relation between each lattice node and the inner surface boundary grid model according to the number of intersection points of the plurality of rays led out by each lattice node and the inner surface boundary grid model; judging the position relationship between each lattice rod and the inner surface boundary grid model according to the position relationship between each lattice node and the inner surface boundary grid model;
And the cutting module is used for cutting the lattice filled in the regular space region according to the position relation between the lattice rods between any two lattice nodes and the inner surface boundary grid model so as to obtain a space lattice model filled in the cavity of the target structure model.
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