Design methods and systems for finite element boundary load models

Abstract

The present invention belongs to the technical field of establishing finite element physical models, and specifically relates to a design method and system for a finite element boundary load model. The design method of the finite element boundary load model of the present invention can decouple the original geometric model and the boundary load, maximize the use of pure geometric model data for finite element calculations, reduce the necessity of repeated modeling, and provide a prerequisite for quickly solving the finite element model; for solving problems at different times in a continuous time period, a geometric intersection body can be constructed for the current moment based on the calculation results of the previous moment and combined with the actual situation, and then an equivalent load is set based on the mesh model after the geometric intersection body and the geometric model are divided to perform finite element solution at the current moment, thereby solving the finite element problem of solving different boundary domains at continuous moments.

Description

Technical Field

[0001] The invention belongs to the technical field of establishing finite element physical models, and in particular relates to a design method and system for a finite element boundary load model. Background Art

[0002] In the process of finite element model solution analysis, the loading of boundary loads is a relatively complicated process. In the current technical solution, in order to facilitate the loading of boundary loads (especially surface loads) in the later stage, the early geometric model needs to be artificially divided. The role of this division is to produce two parts that are easy to select, namely, the part with boundary loads and the part without boundary loads. This processing method increases the coupling between the geometric model and the finite element solution model, and has two disadvantages:

[0003] (1) In the actual geometric modeling process, the initial model is usually not conducive to the setting of finite element boundary loads because the subsequent use requirements are not considered. In order to solve the loading of finite element boundary loads in the later stage, finite element simulation users need to re-perform geometric modeling (the early modeling cannot be used, resulting in a waste of resources).

[0004] (2) The boundary area of ​​the finite element model may change over time, resulting in different boundary areas at different times. Therefore, the same geometric model cannot be used to handle this situation. Summary of the invention

[0005] The purpose of the present invention is to provide a design method and system for a finite element boundary load model.

[0006] A first aspect of the present invention provides a design method for a finite element boundary load model, comprising the following steps:

[0007] S1: Create a three-dimensional geometric entity based on the shape of the actual engineering object;

[0008] S2: Design one or more virtual geometric intersection bodies for boundary loads according to the instantaneous load conditions;

[0009] S3: Set node loads, body loads and element material property parameters for the load case;

[0010] S4: Mesh the entire three-dimensional geometric entity, take the vertex displacement of the mesh unit as the unknown quantity, and obtain the overall stiffness matrix in combination with the material properties;

[0011] S5: Determine and calculate the equivalent load of each mesh vertex based on the intersection of the three-dimensional geometric entity and the virtual geometric entity, and integrate it into the overall equivalent load vector to obtain the equilibrium equation group;

[0012] S6: Solve the equilibrium equation to obtain the calculation results of the unknown quantities of each grid unit;

[0013] S7: Perform post-processing analysis based on the unvectorized calculation results;

[0014] S8: If the boundary area needs to be modified, return to S2 to repeat the design and calculation.

[0015] A second aspect of the present invention provides a design system for a finite element boundary load model, comprising:

[0016] A three-dimensional geometric entity creation module is used to create a three-dimensional geometric entity for its shape according to the actual engineering object;

[0017] A virtual geometric intersection design module is used to design one or more virtual geometric intersections for boundary loads based on instantaneous load conditions;

[0018] Parameter setting module, used to set node loads, body loads and unit material property parameters for the working condition;

[0019] The overall stiffness matrix acquisition module is used to mesh the entire three-dimensional geometric entity, taking the vertex displacement of the mesh unit as the unknown quantity and combining the material properties to obtain the overall stiffness matrix;

[0020] The equilibrium equation group acquisition module is used to determine and calculate the equivalent load of each grid vertex based on the intersection of the three-dimensional space geometric entity and the virtual geometric body, and integrate it into the overall equivalent load vector to obtain the equilibrium equation group;

[0021] The solution module is used to solve the equilibrium equation to obtain the calculation results of the unknown quantities of each grid unit;

[0022] The processing and analysis module is used to perform post-processing analysis based on the unvectorized calculation results.

[0023] A third aspect of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, the design method according to the finite element boundary load model as described above is implemented.

[0024] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements a design method according to the finite element boundary load model as described above.

[0025] The beneficial effect of the present invention is that the design method of the finite element boundary load model of the present invention can decouple the original geometric model and the boundary load, maximize the use of pure geometric model data for finite element calculations, reduce the necessity of repeated modeling, and provide a prerequisite for quickly solving the finite element model; for solving problems at different times in a continuous time period, a geometric intersection body can be constructed for the current moment based on the calculation results of the previous moment and combined with the actual situation, and then an equivalent load is set based on the mesh model after the geometric intersection body and the geometric model are divided to perform finite element solution at the current moment, thereby solving the finite element problem of solving different boundary domains at continuous moments.

[0026] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 The flowchart of the design method of the finite element boundary load model of the present invention is shown in FIG. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Since the original geometric model is mostly modeled from the perspective of shape. However, when setting up the finite element model, the boundary load usually cannot completely cover a complete face in the geometric shape. In order to solve this contradiction, the current finite element software provides two solutions: (1) Abaqus, ANSYS, etc. provide a face segmentation tool (hereinafter referred to as the face segmentation solution) to allow users to re-split the faces related to the boundary surface load in the model to ensure that each face can only have a boundary surface load or no boundary surface load; (2) No processing is required, and third-party software is needed to rebuild the geometric model after face segmentation, so as to facilitate the setting of boundary surface loads.

[0032] No matter which of the above two solutions is adopted, the original geometric model and the boundary load setting are bound. This leads to the necessity to create (or design) different geometric models for different boundary domains, although the corresponding geometric physical models are the same.

[0033] In the above-mentioned Abaqus face segmentation scheme, the segmentation boundary line set by the user is essentially the intersection boundary line of the external boundary body and the geometric body of the computational model. Usually, in reality, the external boundary body is an infinite geometric body. For example, during the sea trial of a large ship, the hull is used as the computational model, and the intersection line between the hull and the sea surface is the load boundary line that needs to be set. The hull bears the buoyancy of the sea level. During the sea trial, due to various conditions such as the speed, the intersection position of the hull and the sea surface will be different at different times: if the entire hull is divided into two parts according to the sea level during the modeling process, each different state will inevitably correspond to a geometric model, resulting in countless modeling requirements, which is obviously unreasonable.

[0034] However, it is more practical to regard the seawater below the sea level as a geometric intersection body. At the same time, since the seawater below the sea level is an "infinite" geometric body, it is not very realistic to use this geometric body directly for modeling in the software desktop display. In combination with actual needs, the geometric intersection body (seawater here) constructed by the present invention should meet the following two conditions: (1) The geometric intersection body has a simple structure, and a finite rectangular parallelepiped can be used here (in other cases, a stretched body obtained by stretching any plane contour along the spatial axis, a rotating body obtained by rotating any plane contour along the spatial axis, a lofted body formed by lofting any plane contour along the spatial curve, and a lofted fusion body formed by lofting and fusion of multiple cross-section contours along the spatial curve can also be used. These geometric bodies can exist in one or more in the same calculation model); (2) The intersection line obtained by intersecting the geometric intersection body with the original model is consistent with the actual intersection line. Under the premise of these two conditions, we can design different intersection bodies for each moment of the large hull sea trial, so as to perform non-state buoyancy calculation at each moment. Thereby, the original geometric model does not need to change with the change of the boundary line, that is, the relationship between the original geometric model and the boundary load is decoupled.

[0035] From the perspective of the correlation of things, the original geometric model and the actual boundary load are two relatively independent things. Based on this, the present invention constructs a virtual geometric intersection body, and obtains the scope (boundary load surface set) of the actual boundary load by intersecting the virtual geometric intersection body with the original geometric model, which is convenient for later load setting.

[0036] See also Figure 1 In one embodiment of the present invention, the design method of the finite element boundary load model includes the following steps:

[0037] S1: Create a three-dimensional geometric entity based on the shape of the actual engineering object;

[0038] S2: Design one or more virtual geometric intersection bodies for boundary loads according to the instantaneous load conditions;

[0039] S3: Set node loads, body loads and element material property parameters for the load case;

[0040] S4: Mesh the entire three-dimensional geometric entity, take the vertex displacement of the mesh unit as the unknown quantity, and obtain the overall stiffness matrix in combination with the material properties;

[0041] S5: Determine and calculate the equivalent load of each mesh vertex based on the intersection of the three-dimensional geometric entity and the virtual geometric entity, and integrate it into the overall equivalent load vector to obtain the equilibrium equation group;

[0042] S6: Solve the equilibrium equation to obtain the calculation results of the unknown quantities of each grid unit;

[0043] S7: Perform post-processing analysis based on the unvectorized calculation results;

[0044] S8: If the boundary area needs to be modified, return to S2 to repeat the design and calculation.

[0045] In this embodiment, optionally, the virtual geometric intersection body in S2 includes: a finite cuboid, a stretched body obtained by stretching an arbitrary plane contour along a spatial axis, a rotated body obtained by rotating an arbitrary plane contour along a spatial axis, a lofted body formed by lofting an arbitrary plane contour along a spatial curve, and a lofted fusion body formed by lofting and fusion of multiple cross-section contours along a spatial curve.

[0046] Specifically, in some application scenarios, common forms of geometric intersection in practical applications are:

[0047] (1) In two-dimensional / three-dimensional space, the software defines the geometric intersection volume in the form of {A*x+B*y+C*z+D≥0 or A*x+B*y+C*z+D>0, where A, B, C, D are arbitrary constants}. This form essentially uses the infinite geometric intersection volume constructed in the present invention;

[0048] (2) A geometric intersecting body obtained by intersecting multiple infinite geometric intersecting bodies obtained from (1);

[0049] (3) A body of rotation obtained by rotating any plane contour along the spatial axis;

[0050] (4) A stretched body formed by any plane contour along a straight line in space;

[0051] (5) Lofted bodies formed by arbitrary plane contours along space curves;

[0052] (6) A lofted fusion body formed by lofting and fusion of multiple plane contours along a space curve;

[0053] (7) During the use of the software, the virtual geometric intersection body can be expressed in the form of a mathematical geometric expression or an actual spatial geometric entity.

[0054] In step S2, specifically, the steps of designing a virtual geometric intersection body for the boundary load include:

[0055] S2-1: Establish the minimum projection rectangular bounding box of the three-dimensional geometric entity in the coordinate axis XOY plane. The long side and wide side of the rectangle are parallel to the coordinate axis. The minimum coordinate point A in the bounding box is (x min ,y min ), coordinate maximum point B(x max ,y max ), the bounding box is recorded as Box AB ;

[0056] S2-2: After the spatial entity and all virtual geometric entities intersect, the projection area of ​​the boundary surface shared by both entities on the Z axis is obtained [z min , z max ];

[0057] S2-3: Box AB Decompose into several small rectangular areas Box according to requirements n ;

[0058] S2-4: For each small area Box n Then the Z-axis area [z min ,z max ] is decomposed into several adjacent regions [z mini ,z maxi ];

[0059] S2-5: For XOY plane area Box n With Z-axis area [z mini ,z maxi ], which is the smallest unit of the virtual geometric intersection body;

[0060] S2-6: For the minimum unit in S2-5, in order to simplify the design, only the design of the upper surface Z = f1 (x, y) and the lower surface Z = f2 (x, y) of the intersection body is considered. Any point (x, y) ∈ Box n ;

[0061] S2-7: For Z=f(x,y), f can be taken as an algebraic expression related to x and y.

[0062] In this embodiment, the decoupling of the original geometric model and the boundary loads is significant for finite element solution in that: the pure geometric model data is used to the maximum extent for finite element calculation, the necessity of repeated modeling is reduced, and the premise for rapid solution of the finite element model is provided; in the process of sea trials of large hulls, in order to solve the problems at different times in a continuous time period, a geometric intersection body can be constructed for the current time according to the calculation results of the previous time, combined with the actual situation, and then an equivalent load is set based on the mesh model after the geometric intersection body and the geometric model are divided to perform finite element solution at the current time. In this way, the finite element problem of solving different boundary domains at continuous times is solved, that is, the purpose of continuous cyclic solution is achieved.

[0063] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0064] In addition, the functional modules in the various embodiments of the present invention may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0065] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0066] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A design method for a finite element boundary load model, characterized in that: The steps include: S1: Create a three-dimensional geometric entity based on the shape of the actual engineering object; S2: Design one or more virtual geometric intersection bodies for boundary loads according to the instantaneous load conditions; S3: Set node loads, body loads and element material property parameters for the load case; S4: Mesh the entire three-dimensional geometric entity, take the vertex displacement of the mesh unit as the unknown quantity, and obtain the overall stiffness matrix in combination with the material properties; S5: Determine and calculate the equivalent load of each mesh vertex based on the intersection of the three-dimensional geometric entity and the virtual geometric entity, and integrate it into the overall equivalent load vector to obtain the equilibrium equation group; S6: Solve the equilibrium equations to obtain the calculation results of the unknown quantities of each grid unit; S7: Perform post-processing analysis based on the calculation results of unknown quantities; S8: If the boundary area needs to be modified, return to S2 to repeat the design and calculation; The step of designing a virtual geometric intersection body for the boundary load in S2 includes: S2-1: Establish the minimum projection rectangular bounding box of the three-dimensional geometric entity in the coordinate axis XOY plane. The long side and wide side of the rectangle are parallel to the coordinate axis. The minimum coordinate point A in the bounding box is (x min , y min ), coordinates of the maximum point B (x max , y max ), the bounding box is denoted as Box AB ; S2-2: After the spatial entity and all virtual geometric intersection bodies are intersected, the projection area of ​​the boundary surface shared by both entities on the Z axis is obtained [z min , z max ]; S2-3: Box AB Decompose into several small rectangular areas Box according to requirements i ; S2-4: For each small area Box i Then the Z-axis area [z min , z max ] is decomposed into several adjacent regions [z mini ,z maxi ]; S2-5: For XOY plane area Box i With Z-axis area [z mini , z maxi ], which is the smallest unit of the virtual geometric intersection body; S2-6: For the minimum unit in S2-5, in order to simplify the design, only the design of the upper surface Z=f1(x,y) and the lower surface Z=f2(x,y) of the intersection body is considered. Any point (x,y)∈Box i ; S2-7: For Z=f(x,y), let f be an algebraic expression related to x and y.

2. The design method of the finite element boundary load model according to claim 1, characterized in that: The virtual geometric intersection body in S2 includes: a finite cuboid, a stretched body obtained by stretching an arbitrary plane contour along the spatial axis, a rotated body obtained by rotating an arbitrary plane contour along the spatial axis, a lofted body formed by lofting an arbitrary plane contour along a spatial curve, and a lofted fused body formed by lofting and fusion of multiple cross-section contours along a spatial curve.

3. A design system for a finite element boundary load model, characterized in that: include: A three-dimensional geometric entity creation module is used to create a three-dimensional geometric entity for its shape according to the actual engineering object; A virtual geometric intersection design module is used to design one or more virtual geometric intersections for boundary loads based on instantaneous load conditions; Parameter setting module, used to set node loads, body loads and unit material property parameters for the working condition; The overall stiffness matrix acquisition module is used to mesh the entire three-dimensional geometric entity, taking the vertex displacement of the mesh unit as the unknown quantity and combining the material properties to obtain the overall stiffness matrix; The equilibrium equation group acquisition module is used to determine and calculate the equivalent load of each grid vertex based on the intersection of the three-dimensional space geometric entity and the virtual geometric body, and integrate it into the overall equivalent load vector to obtain the equilibrium equation group; The solution module is used to solve the equilibrium equations to obtain the calculation results of the unknown quantities of each grid unit; The processing and analysis module is used to perform post-processing analysis based on the calculation results of unknown quantities; in The steps to design virtual geometry intersections for boundary loads include: S2-1: Establish the minimum projection rectangular bounding box of the three-dimensional geometric entity in the coordinate axis XOY plane. The long side and wide side of the rectangle are parallel to the coordinate axis. The minimum coordinate point A in the bounding box is (x min , y min ), coordinates of the maximum point B (x max , y max ), and the bounding box is recorded as Box AB ; S2-2: After the spatial entity and all virtual geometric intersection bodies are intersected, the projection area of ​​the boundary surface shared by both entities on the Z axis is obtained [z min , z max ]; S2-3: Box AB Decompose into several small rectangular areas Box according to requirements i ; S2-4: For each small area Box i Then the Z-axis area [z min , z max ] is decomposed into several adjacent regions [z mini ,z maxi ]; S2-5: For XOY plane area Box i With Z-axis area [z mini , z maxi ], which is the smallest unit of the virtual geometric intersection body; S2-6: For the minimum unit in S2-5, in order to simplify the design, only the design of the upper surface Z=f1(x,y) and the lower surface Z=f2(x,y) of the intersection body is considered. Any point (x,y)∈Box i ; S2-7: For Z=f(x,y), let f be an algebraic expression related to x and y.

4. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, the design method of the finite element boundary load model according to any one of claims 1 or 2 is implemented.

5. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the design method of the finite element boundary load model according to any one of claims 1 or 2 is implemented.

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