A fast pre-processing method for geometric features of frame structure tooling rigidity calculation

Abstract

The present invention discloses a method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling. In order to solve the problems of multiple grids and huge calculation amount in the solid grid division method during the finite element calculation of the rigidity and strength of frame structure tooling, and the problem of manual extraction of geometric structures of components and low parameter efficiency in the neutral layer method, the API interface provided by the CAD system is used for program design and development, and the functions of the native CAD software are expanded to automatically clean and remove small-volume connectors of the frame structure tooling, automatically distinguish the types of components, and automatically identify and classify parameters such as the thickness of tooling parts, and automatically classify and establish a surface model of the standard interface for calculating the rigidity and strength of the frame structure tooling. By performing the common node operation of the surface model in ABAQUS, the rapid pre-processing of the rigidity and strength model of the frame structure tooling is realized, a large number of repetitive manual operations are avoided, and the efficiency of pre-processing of geometric features for calculating the rigidity and strength of the frame structure tooling is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of digital aircraft manufacturing, and in particular relates to a fast pre-processing method for geometric features of frame structure tooling rigidity calculation. Background Art

[0002] Frame structure tooling is mainly composed of gaskets, angle pieces and square steel, and is widely used in aircraft development, such as aircraft assembly jigs, work ladders, etc. With the rapid growth in the number and complexity of aircraft development models, designers need to undertake multiple times the work tasks of the past, including the strength and reliability calculation of frame structure tooling. Pre-processing in CAE software is a tedious and laborious task, which may require thousands of interactive operations to complete. Pre-processing will take up more than half of the energy in the entire simulation process, requiring enterprises to invest huge manpower and time costs.

[0003] There are two commonly used finite element calculation pre-processing methods: (1) Frame entity method: directly divide the frame entity into grids. To ensure the reliability of the simulation results, at least three layers of grids need to be divided in the thickness direction of the frame entity parts. The thickness of the frame parts is generally distributed between 6mm and 15mm, so the grid size is generally in the range of 2mm to 5mm. For large frame structures, it is necessary to divide tens of millions or even hundreds of millions of grid units. However, the performance of current personal work computers cannot bear such a large amount of calculation. This method is only applicable to ultra-small frame structures and has a very small scope of application. (2) Neutral layer method: extract the neutral plane of all frame parts, extend the boundary of the neutral plane of the frame parts that are in contact with each other to the center plane of another part, manually measure the thickness of all frame parts, and assign the thickness to their corresponding neutral planes. This method has the following disadvantages: there are a large number of frame parts in the frame structure, and the manual extraction of neutral planes, extension of boundaries, measurement of part thickness, and assignment of section thickness are repetitive behaviors, which are time-consuming and labor-intensive, and inefficient. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a fast pre-processing method for geometric characteristics of frame structure tooling stiffness calculation, which improves the efficiency of the pre-processing method of finite element calculation of frame structure stiffness, reduces production costs, and has a wide range of applications.

[0005] A fast pre-processing method for geometric features of frame structure tooling stiffness calculation includes the following steps:

[0006] Step 1: Open the solid model of the frame structure tooling in the CAD system. The solid model contains all geometric entities that make up the frame structure tooling, including square steel, angle pieces, gaskets, and connectors.

[0007] Step 2: Batch remove the connectors of all geometric entities:

[0008] Use the API interface provided by the CAD system to traverse all geometric entities, measure the volume of each geometric entity, set the volume threshold of the connectors that need to be cleared, and delete the connectors in batches.

[0009] Step 3: Identify all geometric entity types:

[0010] 3.1 Write a program to traverse each geometric entity in the part document. For each geometric entity, define the interactive selection set Selection1, write the "Search" Topology.CGMFace, sel" statement to search for the surface of the geometric entity, add all the surfaces of the geometric entity to the interactive selection set Selection1, write Sur_Num = Selection1.Count to obtain the number of surfaces on the geometric entity surface, where Sur_Num is the number of surfaces on the geometric entity surface, traverse and measure the area of ​​the surfaces on the geometric entity surface, sort the surfaces on the geometric entity surface from large to small according to the area, define the surface of the sorted geometric entity surface as Sur(i), and define the area of ​​Sur(i) as Area(i), i = 1, 2...Sur_Num;

[0011] 3.2 The geometric entity type is determined by using the surface Sur(i) of the sorted geometric entity surface in step 3.1 and the geometric entity type recognition algorithm. The geometric entity type recognition algorithm is as follows:

[0012] 3.2.1 Gasket geometric entity type recognition algorithm

[0013] 1)Sur_Num>=8;

[0014] 2)Area(1) / Area(2)<=1.001;

[0015] 3) Area(1) / Area(3)>=4;

[0016] 4)Area(1) / Area(4)>=4.

[0017] 3.2.2 Algorithm for identifying geometric entity types of corner pieces

[0018] 1)Sur_Num>=8;

[0019] 2)1<=Area(1) / Area(2)<=1.5;

[0020] 3)1.02<=Area(3) / Area(4)<=2;

[0021] 4)Area(1) / Area(5)>=4.

[0022] 3.2.3 Square steel geometric entity type recognition algorithm

[0023] 1) 9 <= Sur_Num <= 25;

[0024] 2) Area(1) / Area(2)≤2;

[0025] 3) Area(1) / Area(3)≤2;

[0026] 4) Area(1) / Area(4)≤2;

[0027] 5) Area(3) / Area(4)≤2;

[0028] 6) Area(1) / Area(9)>=5;

[0029] Step 4: Calculate the thickness of the geometric entity:

[0030] For each geometric entity, according to the geometric entity type identified in step 3, the corresponding geometric entity thickness calculation method is used to obtain the geometric entity thickness. The geometric entity thickness calculation method is as follows:

[0031] 4.1 Calculation method of thickness of gasket-like geometric entities

[0032] Measure the distance between Sur(1) and Sur(2), which is the gasket thickness T1;

[0033] 4.2 Calculation method of thickness of geometric entities such as corner pieces

[0034] Measure the angles between Sur(1) and Sur(2), Sur(3), and Sur(4) respectively. If any of the angles is 0, measure the distance between the surface corresponding to the angle 0 and Sur(1), which is the thickness T2 of the corner piece.

[0035] 4.3 Calculation method for thickness of square steel geometric entities

[0036] Measure the angles between Sur(1) and Sur(2), Sur(3) ... Sur(8) respectively, record the surface with angle 0, measure the distance between Sur(1) and the surface with angle 0, record the surface Sur_Min corresponding to the minimum distance and the surface Sur_Max corresponding to the maximum distance, measure the distance between Sur_Min and Sur(1), which is the thickness T3 of the square steel.

[0037] Step 5: Construct the finite element calculation pre-processing surface of the geometric entity:

[0038] For each geometric entity, according to the geometric entity type identified in step 3, the corresponding geometric entity finite element calculation pre-processing surface construction method is used to obtain the finite element calculation pre-processing surface of the geometric entity. The geometric entity finite element calculation pre-processing surface construction method is as follows:

[0039] 5.1 Surface construction method for pre-processing finite element calculation of gasket-like geometric entities

[0040] Sur(1) is offset by a distance of T1 / 2, and the distance T_P between the offset surface Sur_P and Sur(2) is measured. If T_P = T1 / 2, then Sur_P is the neutral surface of the gasket; if T_P = 3*T1 / 2, then Sur(1) is offset in the reverse direction, and the offset distance is T1 / 2 to obtain the gasket-like geometric entity pre-processing surface for finite element calculation.

[0041] 5.2 Surface construction method for pre-processing finite element calculation of corner-type geometric entities

[0042] The distances between Sur(1) and Sur(2), Sur(3), and Sur(4) are measured respectively. If any of the distances is 0, the surface corresponding to the distance 0 is combined with Sur(1) into one surface, which is the pre-processing surface for finite element calculation of the corner piece geometric entity.

[0043] 5.3 Surface construction method for pre-processing finite element calculation of square steel geometric entities

[0044] Measure the distances between Sur(1), Sur_Max and the remaining faces respectively, record the faces whose distances to Sur(1) and Sur_Max are both 0, and combine the faces with distances to Sur(1) and Sur_Max into one face, which is the pre-processing surface for finite element calculation of square steel geometric entities.

[0045] Step 6: Assign the corresponding geometric entity thickness value to the finite element calculation pre-processing surface of each geometric entity in batches:

[0046] According to the thickness of the geometric entity calculated in step 4, traverse the pre-processing surfaces of the geometric entities with the same thickness, and combine the pre-processing surfaces of the geometric entities with the same thickness into a face set. The name of the face set is named and identified with the thickness value; open ABAQUS software, import all face sets, and assign thickness values ​​to the corresponding face sets with the thickness values ​​identified by the name of the face set.

[0047] Step 7: Pre-processing of common nodes of the surface of the geometric entity by finite element calculation:

[0048] All face sets are assembled in ABAQUS software, and the "Merge" command is used in the assembly to realize the automatic division of common node parameter lines of common nodes of the surface before finite element calculation of geometric entities.

[0049] The beneficial effects of the present invention are as follows: through a fast pre-processing method for calculating geometric features of rigidity of frame structure tooling based on secondary development of CAD system, the neutral and outer planes of parts of different types and thicknesses are automatically identified, classified and output, the common node process of fast finite element model is optimized, a large number of human-computer interaction operations are reduced, and the pre-processing efficiency is improved by 70%. The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of frame structure tooling.

[0051] Figure 2 Partial view of the frame structure tooling.

[0052] Figure 3 Schematic diagram of the pre-processing surface of gasket-type geometric entities based on finite element calculation.

[0053] Figure 4 Schematic diagram of the pre-processing surface of finite element calculation of corner-type geometric entities.

[0054] Figure 5 Schematic diagram of the pre-processing surface of finite element calculation of square steel geometric entities.

[0055] Figure 6 Schematic diagram of the outer surfaces of two square steels that are welded.

[0056] Figure 7 No common node parameter line diagram is generated.

[0057] Figure 8 Generate a common node parameter line diagram.

[0058] Explanation of the numbers in the figure: 1-gasket, 2-angle piece, 3-square steel, 4-gasket-like geometric solid pre-finite element calculation surface, 5-angle piece-like geometric solid pre-finite element calculation surface, 6-square steel-like geometric solid pre-finite element calculation surface, 7-square steel A, 8-square steel B, 9-common node parameter line DETAILED DESCRIPTION

[0059] like Figure 1 As shown in FIG. 8 , a method for rapid pre-processing of geometric features for calculating the rigidity and strength of a frame structure tooling comprises the following steps:

[0060] Step 1: Open the solid model of the frame structure tooling in the CAD system. The solid model contains all geometric entities that constitute the frame structure tooling, including gaskets 1, angle pieces 2, square steels 3, and connectors.

[0061] Step 2: Batch remove the connectors of all geometric entities:

[0062] Use the API interface provided by the CAD system to traverse all geometric entities, measure the volume of each geometric entity, set the volume threshold of the connectors that need to be cleared, and delete the connectors in batches.

[0063] Step 3: Identify all geometric entity types:

[0064] 3.1 Write a program to traverse each geometric entity in the part document. For each geometric entity, define the interactive selection set Selection1, write the "Search" Topology.CGMFace, sel" statement to search for the surface of the geometric entity, add all the surfaces of the geometric entity to the interactive selection set Selection1, write Sur_Num = Selection1.Count to obtain the number of surfaces on the geometric entity surface, where Sur_Num is the number of surfaces on the geometric entity surface, traverse and measure the area of ​​the surfaces on the geometric entity surface, sort the surfaces on the geometric entity surface from large to small according to the area, define the surface of the sorted geometric entity surface as Sur(i), and define the area of ​​Sur(i) as Area(i), i = 1, 2...Sur_Num;

[0065] 3.2 The geometric entity type is determined by using the surface Sur(i) of the sorted geometric entity surface in step 3.1 and the geometric entity type recognition algorithm. The geometric entity type recognition algorithm is as follows:

[0066] 3.2.1 Gasket 1 geometric entity type recognition algorithm

[0067] 1)Sur_Num>=8;

[0068] 2)Area(1) / Area(2)<=1.001;

[0069] 3) Area(1) / Area(3)>=4;

[0070] 4)Area(1) / Area(4)>=4.

[0071] 3.2.2 Algorithm for identifying two types of geometric entities based on corner pieces

[0072] 1)Sur_Num>=8;

[0073] 2)1<=Area(1) / Area(2)<=1.5;

[0074] 3)1.02<=Area(3) / Area(4)<=2;

[0075] 4)Area(1) / Area(5)>=4.

[0076] 3.2.3 Recognition algorithm for three types of geometric entities of square steel

[0077] 1) 9 <= Sur_Num <= 25;

[0078] 2) Area(1) / Area(2)≤2;

[0079] 3) Area(1) / Area(3)≤2;

[0080] 4) Area(1) / Area(4)≤2;

[0081] 5) Area(3) / Area(4)≤2;

[0082] 6) Area(1) / Area(9)>=5;

[0083] Step 4: Calculate the thickness of the geometric entity:

[0084] For each geometric entity, according to the geometric entity type identified in step 3, the corresponding geometric entity thickness calculation method is used to obtain the geometric entity thickness. The geometric entity thickness calculation method is as follows:

[0085] 4.1 Calculation method of thickness of gasket type 1 geometric entity

[0086] Measure the distance between Sur(1) and Sur(2), which is the thickness T1 of gasket 1;

[0087] 4.2 Calculation method of thickness of two types of geometric entities of corner pieces

[0088] Measure the angles between Sur(1) and Sur(2), Sur(3), and Sur(4) respectively. If any of the angles is 0, measure the distance between the surface corresponding to the angle 0 and Sur(1), which is the thickness T2 of corner piece 2.

[0089] 4.3 Calculation method for thickness of three types of geometric entities of square steel

[0090] Measure the angles between Sur(1) and Sur(2), Sur(3) ... Sur(8) respectively, record the surface with angle 0, measure the distance between Sur(1) and the surface with angle 0, record the surface Sur_Min corresponding to the minimum distance and the surface Sur_Max corresponding to the maximum distance, measure the distance between Sur_Min and Sur(1), which is the thickness T3 of square steel 3.

[0091] Step 5: Construct the finite element calculation pre-processing surface of the geometric entity:

[0092] For each geometric entity, according to the geometric entity type identified in step 3, the corresponding geometric entity finite element calculation pre-processing surface construction method is used to obtain the finite element calculation pre-processing surface of the geometric entity. The geometric entity finite element calculation pre-processing surface construction method is as follows:

[0093] 5.1 Construction method of surface 4 for gasket-like geometric entities before finite element calculation

[0094] Sur(1) is offset by a distance of T1 / 2, and the distance T_P between the offset surface Sur_P and Sur(2) is measured. If T_P = T1 / 2, then Sur_P is the neutral surface of the gasket; if T_P = 3*T1 / 2, then Sur(1) is offset in the reverse direction, and the offset distance is T1 / 2, so as to obtain the gasket-like geometric entity finite element calculation pre-processing surface 4.

[0095] 5.2 Construction method of surface 5 for pre-processing finite element calculation of corner-type geometric entities

[0096] The distances between Sur(1) and Sur(2), Sur(3), and Sur(4) are measured respectively. If any of the distances is 0, the surface corresponding to the distance 0 is combined with Sur(1) into one surface, which is the pre-processing surface 5 of the finite element calculation of the corner piece geometric entity.

[0097] 5.3 Construction method of surface 6 for pre-processing finite element calculation of square steel geometric entities

[0098] The distances between Sur(1), Sur_Max and the remaining surfaces are measured respectively, and the surfaces whose distances to Sur(1) and Sur_Max are both 0 are recorded. The surfaces whose distances to Sur(1) and Sur_Max are combined into one surface, which is the pre-processing surface 6 of the finite element calculation of the square steel geometric entity.

[0099] Step 6: Assign the corresponding geometric entity thickness value to the finite element calculation pre-processing surface of each geometric entity in batches:

[0100] According to the thickness of the geometric entity calculated in step 4, traverse the pre-processing surfaces of the geometric entities with the same thickness, and combine the pre-processing surfaces of the geometric entities with the same thickness into a face set. The name of the face set is named and identified with the thickness value; open ABAQUS software, import all face sets, and assign thickness values ​​to the corresponding face sets with the thickness values ​​identified by the name of the face set.

[0101] Step 7: Pre-processing of common nodes of the surface of the geometric entity by finite element calculation:

[0102] For the finite element calculation pre-processing surface 6 of two square steel geometric entities, square steel A7 and square steel B8, which are in a welding relationship, if square steel A7 does not form a common node parameter line 9 at the intersection, the finite element software defaults to square steel A7 and square steel B8 being unconnected and in a free state, which is inconsistent with the actual working conditions and affects the calculation results.

[0103] All face sets are assembled in ABAQUS software, and the “Merge” command is used in the assembly to realize the finite element calculation pre-processing of geometric entities and automatically divide the common node parameter lines 9.

Claims

1. A fast pre-processing method for geometric features of frame structure tooling stiffness calculation, characterized in that: It includes the following steps: Step 1: Open the solid model of the frame structure tooling in the CAD system. The solid model contains all geometric entities that constitute the frame structure tooling, including square steel, angle pieces, gaskets, and connectors. Step 2: Batch remove the connectors of all geometric entities; Step 3: Identify all geometric entity types; Step 4: Calculate the thickness of the geometric entity; Step 5: construct the finite element calculation pre-processing surface of the geometric entity; Step 6: batch assign corresponding geometric entity thickness values ​​to the finite element calculation pre-processing surfaces of each geometric entity; Step 7: Pre-processing of common nodes of the surface of the finite element calculation of geometric entities; The surface of the geometric entity is Sur(i), and the area of ​​Sur(i) is defined as Area(i), i=1, 2...Sur_Num. When the geometric entity type is a gasket, the method for constructing the pre-processing surface of the geometric entity for finite element calculation is as follows: offset Sur(1) by a distance of T1 / 2, and measure the distance T_P between the offset surface Sur_P and Sur(2). If T_P=T1 / 2, then Sur_P is the neutral surface of the gasket; if T_P=3*T1 / 2, then reversely offset Sur(1) with an offset distance of T1 / 2 to obtain the pre-processing surface of the gasket-type geometric entity for finite element calculation; when the geometric entity type is an angle piece, the pre-processing surface of the geometric entity for finite element calculation The construction method is: measure the distances between Sur(1) and Sur(2), Sur(3), and Sur(4) respectively. If any of the distances is 0, then combine the face corresponding to the distance of 0 with Sur(1) to form a face, which is the pre-processing surface for finite element calculation of the corner piece geometric entity. When the geometric entity type is square steel, the construction method of the pre-processing surface for finite element calculation of the geometric entity is: measure the distances between Sur(1), Sur_Max and the remaining faces respectively, record the faces whose distances to Sur(1) and Sur_Max are all 0, and combine the faces whose distances to Sur(1) and Sur_Max are all 0 to form a face, which is the pre-processing surface for finite element calculation of the square steel geometric entity.

2. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The specific process of the step 2 is: traverse all geometric entities using the API interface provided by the CAD system, measure the volume of each geometric entity, set the volume threshold of the connectors to be cleared, and delete the connectors in batches.

3. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The specific process of step three is as follows: 3.1 Write a program to traverse each geometric entity in the part document. For each geometric entity, define the interactive selection set Selection1, write the "Search" Topology.CGMFace, sel" statement to search for the surface of the geometric entity, add all the surfaces of the geometric entity to the interactive selection set Selection1, write Sur_Num = Selection1.Count to obtain the number of surfaces on the geometric entity surface, where Sur_Num is the number of surfaces on the geometric entity surface, traverse and measure the area of ​​the surfaces on the geometric entity surface, sort the surfaces on the geometric entity surface from large to small according to the area, define the surface of the sorted geometric entity surface as Sur(i), and define the area of ​​Sur(i) as Area(i), i = 1, 2...Sur_Num; 3.2 Use the surface Sur(i) of the sorted geometric entity surface in step 3.1 and the geometric entity type recognition algorithm to determine the type of geometric entity.

4. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 3, characterized in that When the geometric entity type is a gasket, the geometric entity type identification algorithm is: 1)Sur_Num>=8; 2)Area(1) / Area(2)<=1.001; 3) Area(1) / Area(3)>=4; 4)Area(1) / Area(4)>=4.

5. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 3, characterized in that When the geometric entity type is a corner piece, the geometric entity type identification algorithm is: 1)Sur_Num>=8; 2)1<=Area(1) / Area(2)<=1.5; 3)1.02<=Area(3) / Area(4)<=2; 4)Area(1) / Area(5)>=4.

6. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 3, characterized in that When the geometric entity type is square steel, the geometric entity type identification algorithm is: 1) 9 <= Sur_Num <= 25; 2) Area(1) / Area(2)≤2; 3) Area(1) / Area(3)≤2; 4) Area(1) / Area(4)≤2; 5) Area(3) / Area(4)≤2; 6) Area(1) / Area(9)>=5; 7. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The step 4 calculates the thickness of the geometric entity. The specific process is: for each geometric entity, according to the geometric entity type identified in step 3, the thickness of the geometric entity gasket, angle piece and square steel is obtained using the corresponding geometric entity thickness calculation method.

8. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 7, characterized in that When the geometric entity is a gasket, the thickness of the geometric entity is calculated as follows: measure the distance between Sur(1) and Sur(2), which is the gasket thickness T1; 9. A method for rapid pre-processing of geometric features for calculating rigidity and strength of frame structure tooling according to claim 7, characterized in that When the geometric entity is an angle piece, the thickness of the geometric entity is calculated as follows: measure the angles between Sur(1) and Sur(2), Sur(3), and Sur(4) respectively. If any of the angles is 0, measure the distance between the face corresponding to the angle 0 and Sur(1), which is the thickness T2 of the angle piece.

10. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 7, characterized in that When the geometric entity is a square steel, the method for calculating the thickness of the geometric entity is as follows: measure the angles between Sur(1) and Sur(2), Sur(3) ... Sur(8) respectively, record the face with an angle of 0, measure the distance between Sur(1) and the face with an angle of 0, record the face Sur_Min corresponding to the minimum distance and the face Sur_Max corresponding to the maximum distance, measure the distance between Sur_Min and Sur(1), which is the thickness T3 of the square steel.

11. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The step five constructs the finite element calculation pre-processing surface of the geometric entity. The specific process is: for each geometric entity, according to the geometric entity type identified in step three, including gaskets, angle pieces and square steels, the finite element calculation pre-processing surface of the geometric entity is obtained by using the corresponding geometric entity finite element calculation pre-processing surface construction method.

12. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The step 6 batches the corresponding geometric entity thickness value to the finite element calculation pre-processing surface of each geometric entity. The specific process is: according to the geometric entity thickness calculated in step 4, the geometric entity finite element calculation pre-processing surfaces of the same geometric entity thickness are traversed, and the geometric entity finite element calculation pre-processing surfaces corresponding to the geometric entities of the same thickness are combined into a face set, and the name of the face set is named and identified by the thickness value; Open the ABAQUS software, import all face sets, and assign thickness values ​​to the corresponding face sets using the thickness values ​​identified by the face set names.

13. A method for rapid pre-processing of geometric features for calculating the rigidity and strength of frame structure tooling according to claim 1, characterized in that The step seven of the finite element calculation pre-processing surface common nodes of the geometric entity is specifically as follows: assembling all face sets in ABAQUS software, and using the "Merge" command under the assembly to realize the automatic division of common node parameter lines of the common nodes of the finite element calculation pre-processing surface of the geometric entity.

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