WO2004109413A2

WO2004109413A2 - Method for recognizing connectable surfaces

Info

Publication number: WO2004109413A2
Application number: PCT/EP2004/005777
Authority: WO
Inventors: Christophe Ageorges; Reiner Jost; Matthias Martin
Original assignee: Daimlerchrysler Ag
Priority date: 2003-06-11
Filing date: 2004-05-28
Publication date: 2004-12-16
Also published as: EP1631866A2; WO2004109413A3; DE10326228A1

Abstract

The invention relates to a method for automatically recognizing connectable surfaces in a technical system. Said system comprises bodies that can be connected to each other in pairs by using a joining technique. A computer-accessible structure of the system, which encompasses at least one surface (F.1, F.6) that is part of a body for each body of the system, and a joining technique, e.g. a specific gluing method, are predefined, the joining technique creating a layer between two respective bodies of the system. According to the invention, the surfaces or partial areas (F.1a, F.6a) of surfaces (F.1, F.6) of the system, which can be joined by means of the predefined joining technique, are automatically recognized. In order to do so, the intermediate spaces (ZW) between two surfaces of the structure, which can be filled with a layer created by means of the joining technique, are automatically recognized, pairs of connectable finite elements being determined. A decision criterion that can be evaluated with the aid of a computer and compares the positions and/or alignments of the two finite elements to predefined upper and/or lower thresholds is used for determining said pairs of connectable finite elements.

Description

Method for recognizing connectable areas

The invention relates to a method for the automatic detection of connectable surfaces in a technical system. The system comprises bodies which can be connected in pairs using a joining technology. A computer-available construction of the system is specified, which comprises at least one surface belonging to the body for each body of the system.

An important joining technology is the creation of adhesive bonds. These are e.g. B. increasingly used in automotive engineering because a welded connection is not technically feasible, the surfaces to be connected are difficult to access for welders or welding machines or because the welded connection cannot withstand the loads and forces that occur. A welded joint, in particular, is often not possible or uneconomical if the two bodies are made of different materials, e.g. B. made of aluminum and steel or aluminum and magnesium, or if at least one of the boundary surfaces of the body consists of plastic.

In the following, the term “joint connection” also includes seals between two bodies, which, for example, have the task of ensuring a minimum distance between two bodies and to have certain elastic properties or to provide noise damping or insulation.

The connectable surfaces and the layers between the connectable surfaces are preferably broken down into finite elements. Finite element simulations are then carried out. The mechanical behavior of the system is predicted by evaluating the simulation results.

The method of finite elements is from "Dubbel - Taschenbuch für den Maschinenbau", 20th edition, Springer-Verlag, 2001, C 48 to C 50, and from TR Chandrupalta & AD Documentation: "Introduction to Finite Element in Engineering" , Prentice-Hall, 1991. Through simulation with the help of finite elements, strength tasks of all kinds, e.g. B. for stress distribution or stability, numerically solved. For example, it is determined how a system consisting of several solid bodies deforms and bends under external loads and how the bodies move relative to one another. There is a computer-available design of a system to be examined. A certain number of points are called in the construction, which are called nodes. "Finite elements" are the surface or volume elements that are formed with the help of the nodes as their corners. Curved surfaces or bodies that are treated approximately as surfaces, for example sheets of a body of a motor vehicle, are often broken down into shell elements. The nodes form a network in the construction, which is why the process of defining nodes and generating finite elements is called "meshing" of the construction. Depending on the task, the displacements of these nodes and / or rotations of the finite elements in these nodes are called or the stresses in these finite elements are introduced as unknowns. Equations are set up that approximately describe the displacements, rotations or stresses within a finite element. Further equations result from dependencies between various finite elements, e.g. B. from the fact that the principle of virtual work in the nodes must be fulfilled and the calculated displacements must be constant and must meet the boundary condition that in reality there are no gaps or penetrations.

In many cases, such equations are linear in the unknown. The finite element method can also be used in the case of nonlinear equations, e.g. B. for equations in the form of polynomials. Overall, an often very extensive system of equations with the node displacements, node rotations, element stresses or other quantities as unknowns is set up and solved numerically. The solution describes, for example, the state of deformation of the system under specified loads. From this mechanical solution z. B. Derive stress distributions, vibration behavior, buckling behavior or prediction of the service life. Are z. B. determines the displacements and rotations of all nodes of a finite element, the stress in the element can be derived.

Different bodies in a system are often networked independently of one another. For example, the system is part of the body of a motor vehicle to be constructed, and the bodies are subsystems that are constructed in parallel by different suppliers without the networks being adapted to one another. Because the bodies are networked independently of one another, the nodes on adjoining surfaces of the bodies often do not lie on one another, but are e.g. B. shifted against each other or belong to finite elements of different sizes and different orientations in space. Such cross-links of adjoining bodies are referred to as incompatible cross-links.

A realistic finite element simulation must take into account the interactions and interdependencies between the bodies, which are caused by the adjacent surfaces. Finite Element simulations that take these interactions and dependencies into account even with independent and therefore usually incompatible networking of the bodies. Because if a compatible network would be necessary to set up the system of equations and carry out the simulations, the bodies cannot be networked independently of one another.

A method for finite element simulation of an adhesive connection is known from G. Tokar: "Spot welding adhesive - properties and calculation method for linear body stiffness", VDI reports No. 1559, pp. 549-575, 2000. Finite element simulations are known carried out for a system that comprises two sheets that are connected by an adhesive seam. Due to external loads, shifts occur between and within the sheets that are predicted by the simulations. For the simulations, finite elements in the sheets and in the connecting adhesive layer generated .

The method disclosed in G. Tokar, op. Cit. Requires a lot of manual work in the event that the system to be examined comprises many bodies with connectable surfaces or surfaces with complicated geometry. This is the case, for example, when the body is a motor vehicle to be constructed. An operator must manually mark the glued seams in a construction of the system.

The invention has for its object to provide a method that facilitates and accelerates the networking for finite element simulations of a system with a plurality of bodies with a given joining technology, by the use of which a layer can be generated between two bodies of the system.

The object is achieved by a method according to claim 1. Advantageous refinements are specified in the subclaims.

According to the inventive method according to claim 1, the computer-available construction of the system comprises several areas chen. Each of these surfaces belongs to a body of the system. For example, the surfaces are surfaces of the bodies or surfaces that approximate the respective bodies. In the case of thin sheet metal as a body, the approximating surfaces are preferably their central surfaces. The construction does not necessarily include voluminous models of the bodies.

A joining technology is specified, for example a certain adhesive process. The joining technology creates a layer between two bodies, for example an adhesive seam or a seal. Finite elements for the surfaces are created. According to the invention, those areas or partial areas of areas of the system that can be connected by the specified joining technology are automatically recognized. For this purpose, the spaces between two surfaces of the construction that can be filled with a layer created by the joining technology are automatically recognized. For example, those spaces between two surfaces are recognized that can be filled with a glued seam when using the gluing process.

When recognizing the spaces, all surface pairs are determined, which consists of two different surfaces of the construction. Connectable pairs of finite elements in these surface pairs are then automatically determined. The method steps described below are carried out for each surface pair which consists of two surfaces of different bodies. The surfaces of such a pair of surfaces are candidates for being completely or partially connected with a given joining technology. All element pairs of a surface pair with the following properties are selected:

- The element pair consists of a finite element of one surface and a finite element of the other surface of the surface pair. - The two finite elements of the element pair are at a distance from each other that is less than or equal to a predetermined upper bound.

An element pair consisting of two finite elements of the same area is not selected. An element pair consisting of two finite elements, the distance between which is greater than the specified limit, is also not selected. If, for example, the system comprises three bodies and the construction comprises four surfaces and if each of these surfaces is broken down into 100 finite elements, there are 4 * 3/2 = 6 surface pairs and 100 * 100 element pairs per surface pair. If each finite element of one surface has a distance less or equal to the upper bound than four finite elements of the other surface, 100 * 4 element pairs are selected for each surface pair.

This selection is carried out in such a way that all pairs of connectable finite elements are among the selected pairs, that is to say all the non-selected pairs cannot be connected. A computer-available and quickly executable selection rule is used for the selection. The selected pairs of finite elements are examined in more detail. It is decided for each selected element pair whether the two finite elements of the element pair can be connected by the joining technology or not. A computer-evaluable decision criterion is used to automatically make the decision, which compares the positions and / or orientations of the two finite elements with predetermined upper and / or lower bounds. These barriers are preferably specified depending on the technical properties of the joining technology. For example, a glue seam in the gluing process must be at most 1 mm thick and must be at least 0.2 mm thick.

The selected element pairs identified as connectable delimit gaps between surfaces or partial areas of surfaces of the construction. Further finite elements for these spaces are created. With the help of the node Equations for the mechanical behavior of the layers in the interspaces as well as for mechanical dependencies between the layers and the adjacent surfaces can be created for these additional finite elements.

Without additional process steps, the invention takes into account the possibility that only parts of two surfaces can be connected to one another by the joining technology, while other parts are not. For example, one body is a flat sheet and another body is a V-shaped sheet. An area of the flat sheet can be connected to one leg of the folded sheet, but not to the other. Both sheets are approximated by their central planes. Connectable finite elements of surfaces are determined according to the method according to the invention. Only finite elements are determined in the one connectable leg of the V-shaped sheet.

Because the connectivity tests are applied to finite elements of surfaces, fewer comparative operations are to be carried out than if the tests were carried out on finite elements in bodies. Finite elements in surfaces are usually described by fewer parameters. The advantage of using fewer comparison operations is particularly significant if thousands or even hundreds of thousands of finite elements are generated for the surfaces, which is the case, for example, with constructions with many surfaces or with a fine division of the surfaces into many small finite elements can be.

For the implementation of the method according to the invention, a computer-available construction of the system with surfaces for the body is specified. It is not necessary that the construction include voluminous models of the bodies. The method can therefore be used early in the product creation process, namely at a point in time at which only the boundary surfaces or approximating surfaces of the bodies are fixed, but no details of the bodies yet. The use of surfaces and finite elements in the form of surface elements elements also saves considerable computing time as well as computing and storage capacity compared to the use of voluminous models and volume elements as finite elements.

Because the pairs of connectable finite elements and thus connectable surfaces are determined automatically, the errors that a processor, for example a calculation engineer, can make when manually defining connectable surfaces cannot occur. Especially with an extensive system, e.g. B. a motor vehicle, many pairs of surfaces are considered to be connected by the predetermined joining technology. The manual specification of the actually connectable pairs is a time-consuming and error-prone routine work and sometimes not at all within a reasonable time.

The decision criterion that is used in accordance with claim 1 to determine connectable element pairs is a computer-available, automatically evaluable criterion. It provides the connectable surfaces or areas of surfaces much faster than the processor by manual specification. The determination of connectable areas is therefore objective, comprehensible and can be repeated as often as required. It is not necessary to ask the expert knowledge of experienced designers or calculation engineers again for each application. Subjective factors as well as errors and mistakes that often occur in manual specification are excluded. Furthermore, it is not necessary to specify which areas are to be considered adjacent or overlapping.

The method according to the invention can also be used if the system comprises many bodies with connectable surfaces or surfaces with complicated geometries. It is often impossible for such a system to manually determine gaps between connectable surfaces in a reasonable amount of time.

The advantage of automatic detection is even more significant if the prediction of the mechanical behavior has to be carried out several times. This is e.g. B. then Required if different constructions of a technical system are to be compared or if different construction stages are run through and the positions and / or orientations of surfaces are changed. For each finite element simulation of a construction or a construction status, the generation of finite elements is required again.

It is possible that pairs of connectable surfaces are automatically determined by the method according to the invention that were not discovered by the processors as applications of the specified joining technology. This is the case when finite elements in the areas meet the decision criterion and are determined to be connectable. If, for example, the joining technology that is specified for the method according to the invention is less expensive than other joining technologies, the method according to the invention shows potential for savings. For example, bonding is specified as the joining technology, and individual bodies can be made from plastic instead of steel. Bodies made of plastic can only be connected by gluing.

The method according to the invention can also be used when surfaces of the structure have been crosslinked independently of one another and therefore have incompatible crosslinks. Because the networks were carried out independently and can be incompatible, the system bodies can be constructed in parallel, e.g. B. from different agents who do not have to coordinate the networking. Because parallel design and parallel networking are made possible and no coordination about the networking is required, time is saved and a simultaneous product design is made possible. It is possible to network the surfaces independently of one another and to first carry out finite element simulations for each body independently of other bodies. The networks of the individual Areas can be reused for various finite element simulations of the entire system.

The mechanical behavior of a layer can only be predicted realistically if the layer appears as a spatial, ie three-dimensional object, and not as a surface in the simulation. Therefore, further finite elements are created for the layer. According to claim 12, the spaces between the pairs of finite elements determined according to the invention are automatically networked. This creates finite elements with nodes for these gaps. This networking does not necessarily depend on the networking of the approximating surfaces. Therefore, the networking of the layers can be adapted well to the particular task that is to be dealt with using the solution of the system of equations generated according to the invention. For example, depending on the task, the connecting layer is broken down into many small or a few large further finite elements. The thickness of the connecting layer is taken into account - even if the layer has different thicknesses at different points. The layer is treated mechanically in the system of equations. For example, one body is a flat sheet and another body is a V-shaped sheet. According to the method according to the invention, only finite elements in one connectable leg of the V-shaped sheet and finite elements in the adjacent part of the other sheet are determined as connectable finite elements. Further finite elements are only generated in the space between the connectable leg and the opposite area of the flat sheet.

Furthermore, mechanical parameters of the layer can be taken into account in equations of the system of equations. B. an adhesive seam, mechanical parameters of the adhesive used can be taken into account. The mechanical behavior of the connecting layer when the respective surfaces are shifted parallel to the layer can be predicted. Claim 2 specifies refinements of how the selection of element pairs is carried out quickly on account of their spacing. The quickly executable selection is made according to claim 2 with the help of the nodes of the two surfaces of a surface pair. First, all pairs of nodes are determined, each consisting of a node on one surface and a node on the other surface. If one surface comprises N_l nodes and the other surface N_2 nodes, N_l * N_2 node pairs are determined. The distance between the two nodes of the pair of nodes is determined for each pair of nodes. A selection is made from the N_l * N_2 pairs of nodes. Those node pairs are selected whose two nodes have a distance that is less than or equal to a predetermined upper bound.

It is possible to determine all element pairs which each consist of a finite element of one surface and a finite element of the other surface of the surface pair. Many pairs of elements are often determined here. Instead, claim 2 provides for a preselection: Each element pair is determined and thus selected, one of which has a finite element as one node of a selected node pair and its other finite element as the other node of the pair as a node. Further calculations are carried out only for these element pairs determined and thus selected. Those element pairs that were not selected according to the procedure just described are classified as non-connectable. These additional calculations usually require more time-consuming calculations. On the other hand, because distances from nodes can be calculated quickly, the preselection based on distances from nodes can be carried out quickly. For example, the distance is only determined between selected element pairs, and among the determined element pairs, the element pairs with a distance that is not too great are selected. Claim 3 and claim 4 further develop the embodiment according to claim 2. An additional preselection is carried out from the determined element pairs on the basis of the distances between nodes.

According to claim 3, it is checked for each determined element pair whether each node of the one finite element of the element pair has a distance from at least one node of the other finite element that is less than or equal to a predetermined upper limit. If a node of one finite element is too far apart from all nodes of the other finite element, the test is terminated and the element pair is not preselected and therefore not selected and subjected to further tests. The previously determined element pairs are preselected for which the test delivers a positive result.

According to claim 4, on the other hand, it is checked for each element pair determined whether each node of the one finite element of the element pair is at a distance from all nodes of the other finite element which is less than or equal to a predetermined upper limit. If a node of one finite element is too far apart from a node of the other finite element, the test is terminated and the pair of elements is not preselected and therefore not selected and subjected to further tests. The previously determined element pairs are preselected for which the test delivers a positive result.

Claim 5 provides that the distance between two finite elements of a pair of elements is not only compared with the upper, but also with a predetermined lower bound. If the distance is smaller than the lower bound, the element pair is not selected. This means that a selection among the element pairs is made based on the distance. If the distance is larger than an upper or smaller a lower bound, it is decided that the finite elements cannot be connected. Claim 6 specifies refinements of how the selection of element pairs is carried out quickly on account of their spacing. Approximations for the distance are determined by various processes and compared with upper and / or lower bounds. At least one of these processes is preferably carried out in the distance determination. It is also possible to carry out several processes and to compare the respectively determined distance with an upper and / or lower barrier. If all processes and comparisons lead to a positive result, further tests are carried out to decide that the two finite elements can be connected. If a comparison at the end of a process leads to a negative result, it will decide that the two finite elements cannot be connected.

The embodiment according to claim 7 lays down a series of further tests which are incorporated into the decision criterion which can be evaluated by the computer. If a decision is made as to whether the finite elements of a selected element pair can be connected or not, at least one of these tests is carried out. The decision criterion preferably uses a logical combination of the results of these tests. For example, finite elements of a pair are classified as connectable if all tests or if at least one test is met. The individual tests are preferably carried out in a predetermined sequence, so that the individual tests are carried out first with the least computing effort. For a pair of elements, the execution of the individual tests is terminated if, based on the individual tests already carried out, it is already clear whether the finite elements of the pair can be connected or not.

According to claim 7, at least one of the following individual tests is carried out:

- Do the finite elements belong to surfaces of different bodies? It is possible that the two finite elements of a pair of elements belong to two different surfaces of the same body and are connectable.

The angle between the two finite elements of the element pair is determined, e.g. B. as an angle between two normals on the finite elements. It is checked whether the angle is less than or equal to an upper bound - then the test gives a positive result - or not.

One finite element of the pair of elements is projected along a projection vector. This projection vector is generated, for example, by generating two normals of the same length on the two finite elements and the projection vector being the sum vector from these two (claim 8). It is checked whether the projected finite element overlaps with the other finite element - then the test delivers a positive result - or not.

The midpoints of the two finite elements of the element pair are determined. One finite element of the pair of elements is projected along a projection vector. The distance between the center of the projected finite element and the center of the other finite element is determined. It is checked whether the distance is less than or equal to an upper bound - then the test gives a positive result - or not.

As just described, the distance between the center of the projected finite element and the center of the other finite element is determined. The length of the longest edge of the two finite elements of the pair is determined. The quotient of distance and longest edge length is calculated. It is checked whether the quotient is less than or equal to an upper bound - then the test gives a positive result - or not.

At least one barrier depends on at least one of the following parameters: a technological parameter of the specified joining technology,

- The nature of a surface of a body, the material intended for the production of a body, a specification that applies to all bodies in the system.

In the case of an adhesive bond, the maximum and the minimum achievable thickness of the adhesive layer and the material used for adhesive bonding are two such technological parameters. The specification valid for all bodies results e.g. B. from aesthetic requirements or from company standards.

The term joining technology includes according to claim 10 many possible technologies, e.g. B. gluing, welding or that of a sealing or insulating or spacing layer. For example, a spacer layer of rubber is inserted to a predetermined minimum distance between different parts of the body, for. B. planking and interior parts of a motor vehicle to comply.

The embodiment according to claim 11 takes into account the possibility that different joining technologies come into question for the connection of boundary surfaces. These different joining technologies each have an evaluation, e.g. B. depends on the cost and / or the reliability of the respective technology. The joining technologies that can be used to connect this pair are determined for each pair of boundary surfaces. It is possible that no or only one joining technology is determined. If, on the other hand, several are determined, one is selected using the ratings. It is possible that different joining technologies are selected for a system.

The mechanical behavior of the layer can then be predicted more realistically if the dependencies and interactions between a layer in one of the gaps and the areas connected by the layer are taken into account. be done. There are mechanical dependencies between nodes of further finite elements of the layer and adjacent points of a boundary surface of a body connected to the layer, e.g. B. the principle of virtual work, according to which the forces and moments between the nodes and the adjacent points are in balance. These dependencies are taken into account by equations between the nodes in the layer and adjacent points.

Claim 16 provides an advantageous embodiment of how these dependencies are taken into account. Claim 17 shows a further embodiment that saves nodes and thus reduces the number of unknowns in the system of equations to be solved.

In the following an embodiment of the invention will be described with reference to the accompanying drawings. Show:

1 shows a body and two approximating central surfaces of the system to be examined;

Fig. 2. surface elements for the body and middle surfaces of Fig. 1;

3. the determination of the minimum and maximum distance between two surface elements (first and second test);

4. the establishment of an upper bound for the distance between two nodes; 5. the determination of the distance between the center and the intersection of a normal (first test);

6. the determination of the distance between the node and the intersection of a normal (second test);

7. the determination of the maximum angle between two surface elements (third test);

8 shows the determination of the maximum angle between two surface elements in another embodiment (modification of the third test);

9 shows the determination of the distance between the center point and the intersection point of a normal (fourth test);

10 shows the determination of the distance between the center point and the point of intersection of a normal and comparison with an edge length (modification of the fourth test);

Fig. 11. the fifth test;

Fig. 12. connectable areas of the areas F.l and F.2;

13 shows an intermediate space which can be connected by an adhesive layer;

14 shows an example of two connectable surfaces of the same body; The embodiment described below relates to a body of a motor vehicle as the system. The body comprises various sheets and other bodies, and it is automatically determined which of these sheets can be connected to one another in which areas by adhesive bonds.

A computer-available design of the body was created using a computer-aided design (CAD) tool and is available in the form of a CAD model. For example, the CAD tool CATIA was used. A description of CATIA is e.g. B. at http: // www. catia. com, queried on February 5, 2003, available. The entire body, including the sheets, is constructed in volume, so that the thicknesses of the sheets are fixed.

Because the sheets are very thin compared to their expansion, they are approximated in the finite element simulations by their central surfaces. All middle surfaces are broken down into two-dimensional finite elements in the form of shell elements.

A preprocessor is used to generate the data required for a finite element simulation from the CAD model for the body. The networking of the CAD model of the body is carried out automatically with the help of this preprocessor. The method according to the invention and described below is carried out during the crosslinking, namely after the finite elements for the approximating sheets have been produced.

An example of such a preprocessor is the MEDINA software tool. A description of MEDINA is available at http .- // www, c3pdm.com/des/products/medina/documentation/medina -DINA4 e.pdf, queried on February 5, 2003. The "MEDINA / PreProcessing" module automatically imports a CAD model that is saved in the CATIA data format or in the standardized STEP or VDA data formats. After the import, MEDINA automatically meshes the CAD model of the body based on the specifications of a user. The finite elements and the nodes are generated in MEDINA and saved in a computer-available form in the MEDINA data format.

A tool for carrying out a simulation according to the finite element method (FEM tool) imports this description in the data format from MEDINA or another data format and carries out the finite element simulations. The expert knows various FEM tools, e.g. B.

- MSC.NASTRAN and MSC.PATRAN, both described at http: //www.mscsoftware. com / products /, queried on February 5, 2003,

- ABAQUS, described at http: //www.hks. com / products / products overview.html, queried on February 5, 2003,

- PAMCRASH for finite element simulations of collisions, described at http: //www.esi- group.com/products/crash/index.php, queried on February 5, 2003.

In this example the construction of the system comprises two sheets and a voluminous body K.I. In this example, the sheets are both 2 mm thick and are approximated in the middle by two surfaces F.l and F.2. The body K.l is represented by two delimiting surfaces F.6 and F.7. Fig. 1 shows the body K.l and four surfaces F.l, F.2 of the two sheets and F.6, F.7 of the body K.I. The areas F.l, F.6 and F.2 are folded and comprise two levels. The distances and the different orientations of the surfaces and the body in the room are exaggerated for clarity. The area F.6 of the body K_l points to the area F.l and is hidden in FIG. 1.

All pairs of surfaces that belong to two different bodies are determined. There are a total of 4 areas and therefore 4 * 3/2 = 6 pairs, each consisting of two areas stand. Because the construction comprises a body with two surfaces, one of these six surface pairs consists of two surfaces of the same body, namely the pair (F.6, F.7). The surface pair (F.6, F.7) is not examined for connectivity in this embodiment. The remaining five surface pairs are examined.

A network of all surfaces is created. In this example, the finite elements all have the shape of triangular or square surface elements. In this example, all four nodes of a square surface element lie in one plane. Square surface elements, for which this is not the case, are preferably broken down into two triangular surface elements for the test for connectivity. An alternative to this is to replace a square surface element whose nodes are not in one plane for the connectivity tests with an approximating square surface element whose four nodes are all in one plane.

FIG. 2 shows some surface elements for the bodies and for the middle surfaces of FIG. 1. The square surface elements preferably have the shape of rectangular ones, but other shapes are also possible. In this example, the edge lengths of the surface elements are 10 mm and 5 mm.

The method according to the invention is explained using the example of the two middle surfaces F.l and F.6, which approximate two different sheets. The pair of surfaces F.l, F.6 is automatically examined to determine which pairs of surface elements of the surfaces F.l, F.6 can be connected to one another by an adhesive connection. For each element pair, a decision is made as to whether or not the two surface elements of the element pair can be connected by an adhesive connection.

3 illustrates an example of the selection of element pairs for the surface pair, which consists of the two surfaces F1 and F.6. First, the nodes of all Surface elements are determined and their coordinates are saved in a vector. With five pairs of surfaces, five vectors with three coordinates of node points are stored. The nodes 200.1, 200.2, 200.3, 200.4, 200.5 and 200.6 belong to the nodes of the area F1. The nodes of area F.6 include nodes 201.1, 201.2, 201.3, 201.4, 201.5 and 201.6.

In this example it is specified that an adhesive connection may be a maximum of 1 mm thick. An upper bound for the maximum distance between the nodes of two connectable surface elements is derived from this. This derivation is illustrated in FIG. 4.

To simplify matters, it is assumed in the example in FIG. 4 that the two surface elements 100.2 and 101.2 are parallel to one another. The length of the route from node 201.1 of area F.6 to the nearest point 230.23 of area F.l may not exceed 1 mm. The closest point 230.23 is the base point of a normal on F.6 through the node 201.1. The edge lengths of both surface elements are 5 mm and 10 mm. The distance 260.1 between the node 201.1 and the nearest node 200.7 is therefore less than or equal

Va ² + b ² + c ² = / l ² + (10/2) ² + (5/2) ² = 5.67 mm

In order to be on the safe side, Δ_l is set as the upper limit for the distance between two nodes Δ_l = 6 mm.

The surface elements of the area Fl have a total of N_l nodes, those of the area F.6 have a total of N_2 nodes. Every distance between a node of Fl and a node of F.6 is determined. This requires N__l * N_2 distance calculations. The calculation of the distance between two points requires considerably less computing time than other tests of finite elements, therefore distance calculations are carried out first, and depending on the result of these distance calculations, element pairs are selected and further, more computational tests carried out only for the selected element pairs. The calculated distances are temporarily stored in an N_1 * N_2 matrix because each distance value is used several times. In an alternative embodiment, a 1 or a 0 is stored in each of the N_l * N_2 fields of an N_l * N_2 matrix A. A (i, j) is 1 if the distance between node no. I of one surface and node no. J of the other surface is less than or equal to 6 mm, otherwise it is 0.

In the example of Fig. 3 u. a. the following pairs of nodes a distance of at most Δ_l = 6 mm from each other: 200.1 and 201.1, 200.1 and 201.2, 200.1 and 201.3, 200.1 and 201.4, 200.1 and 201.5, 200.1 and 201.6. Have a larger distance z. B. 200.6 and 201.2, 200.5 and 201.3.

Each element pair is determined, one finite element of which has one node of a selected node pair as a node and the other finite element of which has the other node of the same node pair as a node. A selected pair of nodes in FIG. 3 is pair 200.1 and 201.1. The following 4 * 4 element pairs are therefore determined, one finite element having point 200.1 and the other finite element having point 201.1 as nodes: 100.1 and 101.1, 100.1 and 101.2, 100.1 and 101.3, 100.1 and 101.4, 100.2 and 101.1, ..., 100.4 and 101.1, 100.4 and 101.2, 100.4 and 101.3, 100.4 and 101.4.

A preselection is made from these ascertained element pairs on the basis of the distances between nodes. One of the following two embodiments is used for this:

In one embodiment, it is checked for each element pair determined whether or not each node of one finite element of the element pair is at a distance from at least one node of the other finite element that is less than or equal to an upper bound Δ_2 , The bound Δ_2 is determined so that the element pair (100.2, 101.2) are preselected in the example of FIG. 4, however the element pair (100.1, 101.2) is not. All three finite elements have edge lengths of 10 mm and 5 mm. As explained above, each node from 101.2 is therefore at a distance from at least one node from 100.2 that is less than 5.67 mm. Therefore, the upper limit is set to Δ_2 = 6 mm.

The surface element 100.1 has the nodes 200.1, 200.2, 200.3 and 200.4. The surface element 101.2 has the nodes 201.1, 201.2, 201.3 and 201.4. Read access to the N_1 * N_2 matrix determines that node 200.1 from 100.1 to node 201.2 from 101.2 has a distance of less than Δ_2 = 6 mm. It is also found that the distances between 200.2 and 201.2, between 200.4 and 201.4 and between 200.3 to 201.3 are less than Δ_2 = 6 mm. The element pair (100.1, 101.2) is therefore preselected. In contrast, the distances between the node 201.3 of 101.2 and the nodes 200.1, 200.4, 200.5 and 200.6 of 100.4 are all greater than Δ_2 = 6 mm, which is why the element pair (100.4, 101.2) is not preselected.

In the other embodiment, it is checked for each determined element pair whether or not each node of one finite element of the element pair is at a distance from each node of the other finite element that is less than or equal to an upper bound Δ_2. The limit Δ_2 is determined so that in the example of FIG. 4 the element pair (100.2, 101.2) are preselected, but the element pair (100.1, 101.2) is not. All three finite elements have edge lengths of 10 mm and 5 mm. The distance between a node of 100.2 and 101.2 is at most a ² + b ² + c ² = _Λ / 1 ² + 10 ² + 5 ² = 11, 22 mm.

In contrast, the distance between 201.1 and 200.3 is more than 12 mm. In this embodiment, therefore, Δ_2 = 12 mm is set. In this embodiment, the preselection is carried out as follows: The surface element 100.1 has the nodes

200.1, 200.2, 200.3 and 200.4. The surface element 101.2 has the nodes 201.1, 201.2, 201.3 and 201.4. Read access to the N_1 * N_2 matrix determines that the node 200.1 has a distance of 10 mm or less from 100.1 to 201.1, 201.2, 201.3 and 201.4. It is also found that the distance between 200.2 and 201.1, between 200.2 and 201.2, between 200.2 and 201.3 and between 200.2 and 201.4 is less than Δ_2 = 12 mm, that the distance between 200.3 and 201.1, between 200.3 and 201.2, between 200.3 and 201.3 and between

200.3 and 201.4 each is less than Δ_2 = 12 mm and that the distance between 200.4 and 201.1, between 200.4 and

201.2, between 200.4 and 201.3 and between 200.4 and

201.4 is less than Δ_2 = 12 mm. The element pair (100.1, 101.2) is therefore preselected. In contrast, the node 201.2 from 101.2 to the node 200.5 from 100.4 has a distance greater than Δ_2. The element pair (100.4, 101.2) is therefore not preselected.

This procedure is carried out for all determined element pairs. This selects pairs of elements. The further tests are only carried out for these selected element pairs.

The first test, which is illustrated in FIG. 5, determines the distance between the two surface elements 100.1 and 101.2. For the test, a normal is determined on the surface element 100.1 and another normal on the surface element 101.2. A straight line 211.4 through the center point 240.2 of 100.1 is generated. The center point 240.2 is determined as the intersection of the two diagonals in the surface element 100.1. The line 211.4 has the same direction as the sum of the two normals on 100.1 and 101.2. The intersection 230.1 between the straight line 211.4 and the surface element 101.2 is determined. If there is no such intersection, the test gives a negative result. Otherwise it will the distance between the center point 240.2 and the intersection point 230.1 is compared with a predetermined upper limit Δ_5 = 1.8 mm. The distance is preferably additionally compared with a lower bound Δ_6 = 0.8 mm. If this distance is less than or equal to Δ_5 and greater than or equal to Δ_6, the test returns a positive result. Otherwise it is automatically decided that 100.1 and 101.2 cannot be connected by an adhesive connection.

A modification of the first test, not illustrated by a figure, provides for the two center points of the two surface elements 100.1 and 101.2 to be determined. The distance between the two center points is determined and used as the distance between the two surface elements.

6 illustrates a second test for the element pair with the surface elements 100.4 and 101.1. In the four nodes 200.1, 200.4, 200.5 and 200.6 of the surface element

100.4 a normal to 100.1 is generated. The four intersections of these four normals with the surface F.6 are determined. Such an intersection can also lie outside the surface element 101.1. 6 are the normals

210.5 represented by the node 200.4 and its intersection 230.4 with the area F.6. 230.4 is outside the surface element 101.1. The distance between the node

200.4 and the intersection 230.4 of the normals 210.5 running through 200.3 is determined and compared with an upper bound Δ_7 and a lower bound Δ_8. Furthermore, the distance between 200.1 and the intersection of the normals passing through 200.1 with F.6, the distance between 200.5 and the intersection of the normals passing through 200.5 with F.6

- and the distance between 200.6 and the intersection of the normals running through 200.6 is determined with F.6 and compared in each case with Δ_7 and Δ_8. Furthermore, four normals are generated on 101.1, which are defined by 201.1, 201.4, 201.5 and 201.6. Your intersections with Fl are determined. 6 shows the normal 210.6 through the node 201.1 and its intersection 230.5 with the surface F1. The four distances between the four intersections of the four normals on F.6 with the respective nodes through 201.1, 201.4, 201.5 and 201.6 are also determined and compared in each case with Δ_7 and Δ_8.

FIG. 7 illustrates the third test carried out next, by means of which the angle 220.1 between the two surface elements 100.1 and 101.2 is determined. A normal 210.1 to the surface element 100.1, which intersects 100.1 at a base point 230.10, is generated. In the case of flat surface elements, the result of the test does not depend on the choice of base point 230.10. If a surface element with four nodes is not flat, it is broken down into two triangular surface elements and the following procedure is performed for each of these two triangles. The normal preferably has a length of 1. Furthermore, a normal 210.2 is generated on the surface element 101.2, which also has a length of 1. This normal is moved to footnote 230.10. The position of these shifted normals is illustrated by the dashed line 210.3. The angle α between 210.1 and 210.2, which is equal to the angle 220.1 between 210.1 and 210.3, is determined according to the following relationship:

210.1 * 210.2 = || 210.l || * || 210.2 || * cos α = cos α = cos (220.1)

Here 210.1 * 210.2 denotes the dot product of the two vectors 210.1 and 210.2 and || 210.l || the Euclidean length of the vector 210.1. The angle α determined in this way is compared with a predetermined upper limit Δ_4 = 10 degrees. If the angle 220.1 is less than or equal to Δ_4, the test gives a positive result. Otherwise it is automatically decided that 100.1 and 101.2 cannot be connected by an adhesive connection. A modification of the third test just described is illustrated in FIG. The center point 240.2 of the surface element 100.1 is determined. A normal 210.4 to the surface element 100.1, which intersects 100.1 at the center 240.2, is generated. The intersection 230.1 of the normal 210.4 with the other surface element 101.2 is determined. If there is no such intersection, the test gives a negative result and it is decided that 100.1 and 101.2 cannot be connected by an adhesive connection. If there is an intersection 230.1, a normal 210.5 is generated by the intersection 230.1 on the other surface element 101.2. The angle 220.2 between 210.4 and 210.5 is compared with the predetermined upper limit Δ_4. If the angle 220.2 is less than or equal to Δ_4, the test gives a positive result. Otherwise it is automatically decided that 100.1 and 101.2 cannot be connected by an adhesive connection.

The fourth test is illustrated by FIG. 9. The center point 240.2 of 100.1 is determined or reused from a previous test. A normal 210.4 to 100.1 through the center point 240.2 is generated. The intersection 230.1 of these normals with the surface element 101.2 is determined. If there is no such intersection, the test gives a negative result. Otherwise, the center point 240.1 of the surface element 101.2 and the distance between 230.1 and 240.1 are determined. This distance is compared with a predetermined upper limit Δ_9 = 4 mm. If this distance is less than or equal to Δ_9, the test gives a positive result. Otherwise it is automatically decided that 100.1 and 101.2 cannot be connected by an adhesive connection.

A modification of this fourth test is illustrated by FIG. 10. As just described, the distance between the intersection 230.1 and the center 240.1 of 101.2 is determined. In addition, the length of the longest edge of the two surface elements 100.1 and 101.2 is determined. For this purpose which determines the lengths of eight edges, namely the following edges: the edge from 200.1 to 200.2, the edge from 200.1 to 200.4, the edge from 200.3 to 200.2, the edge from 200.3 to 200.4, the edge from 201.1 to 201.2, the edge from 201.1 to 201.4, the edge from 201.3 to 201.2, the edge from 201.3 to 201.4.

In this case, the edge from 200.1 to 200.4 and the edge from 200.3 to 200.2 are the longest edges of 100.1 and are the same length. The quotient of the distance between the intersection 230.1 and the center 240.1 (in the numerator) and the length of the edge from 200.1 to 200.4 (in the denominator) is calculated. The numerator can be 0, the denominator cannot. This distance is compared with a predetermined upper limit Δ_10 = 0.9 mm. If this distance is less than or equal to Δ_10, the test gives a positive result. Otherwise it is automatically decided that 100.1 and 101.2 cannot be connected by an adhesive connection.

The fifth test is illustrated by FIG. 11. Two normals 210.1 on the surface element 100.1 and 210.2 on the surface element 101.2 are formed. The two base points of the normals can be selected as desired. Two normal vectors of the same length are generated on these two standards. These two normal vectors are not shown in FIG. 11. The sum vector 250.1 of these two normal vectors is generated. It begins at base 230.10 of normal 210.1. In this example, a straight line 210.8 is first generated, which runs through the node 200.4 of the one surface element 100.1 and has the direction of the sum vector 250.1. This line 210.8 intersects the surface F.6 at point 200.13. In In the same way, a straight line 210.9 is generated in the direction of 250.1, which goes through the node 200.1. F.6 intersects this straight line 210.9 in 200.12. The same is done for the other two nodes of 100.1. This creates a square with corners 200.12, 200.13, 200.14 and 200.15. It is checked whether this square has an overlap area with the surface element 101.2 or not. If there is an overlap area, it is clear that the fifth test gives a positive result. In the example of FIG. 11 there is an overlap area.

The following tests are preferably carried out for a determined element pair: the modification of the first test (distance between the center points) if these produced a positive result, the third test if this produced a positive result, the modification of the fourth test,

- If this gave a positive result, the fifth test, if it also gave a positive result, it is decided that the two surface elements of the element pair can be connected to one another.

The following decisions are made in the example of FIGS. 3 to 11:

- 100.1 can be connected to 101.2,

- 100.2 can be connected to 101.3,

- 100.3 can be connected to 101.4,

- 100.4 can be connected to 101.1.

FIG. 12 illustrates which areas of the areas shown in FIG. 1 can be connected to one another. These areas are automatically determined by the method described above. It is determined which surface elements of Fl with each a surface element of F.6 can be connected. The set of these surface elements of Fl provides the partial area of Fl that can be connected to F.6. The corresponding steps are carried out for F.6. FIG. 12 shows a partial area F.la of the area F1 and two partial areas F.6a and F .6b of the area F.6. F.la has the two corner points 201.15 and 201.16 and two other corner points, not shown. F.6a has the four corner points 201.11, 201.12, 201.13 and 201.14. The method according to the invention provides, inter alia, the result that the two partial areas F.la and F.6a can be connected to one another. The sub-area F.6b cannot be connected to a sub-area of F .1.

13 shows the two partial areas F.la and F.6a of the areas F.l and F.6 which can be connected to one another. Due to the computer-available design, the thicknesses of all sheets in the system are specified. For this reason, the two thicknesses d_l and d_3 of those two sheets are given which are approximated by the areas F.l and F.6. Two areas F.lk and F.6k are created. F.lk lies in the surface of the sheet which is approximated by the area F.l, and thus also in the boundary surface of the connecting adhesive layer. F.6k is congruent with F.6a, but belongs to the adhesive layer. F.lk and F.6k have the same dimensions and orientations as F.la and F.6a. F.lk is parallel to F.la, F.6k parallel to F.6a. The distance between F.la and F.lk is 0.5 * d_l (thus half the thickness of the sheet. FIG. 13 shows the two partial areas F.lk and F.6k, and also the intermediate space ZW between these two partial areas.

In this embodiment, the two surfaces of a pair of surfaces always belong to two different bodies of the system. However, it is also possible to examine two surfaces of the same body for connectivity. 14 shows an example of two connectable surfaces F.10 and F.11 of the same body. According to the invention, it is determined that an adhesive connection can be produced which fills the intermediate space. In the next step, the spaces between the connectable sub-areas are preferably automatically networked. The thickness of the sheet is taken into account, and only spaces in layers between sheets are cross-linked. The meshing of a gap that connects two sheets of the system is carried out automatically. The following information is taken from the computer-available construction of the system: the spatial position of the two approximating surfaces Fl and F .6 and the thickness of the two sheets - in this example, each sheet has a constant thickness over the entire extent, the two thicknesses can vary differentiate from each other.

In this example, the thickness of the space ZW is 0.8 mm. The thickness and the spatial extent of the intermediate space are automatically obtained from this geometric information about the sheets. It is also possible to specify the thickness of the space and the spatial position of the two approximating surfaces instead.

It is possible to divide the spaces in the transverse direction into several volume elements. If e.g. B. an intermediate space is 0.8 mm thick and it is specified that an intermediate space is to be broken down into two volume elements in the transverse direction, so volume elements are generated which have an edge length of 0 in the transverse direction of the intermediate space, i.e. perpendicular to the boundary surfaces of the layer , 4 mm. The networking of the gaps is controlled by a few, clear parameters. These parameters can be selected so that networking provides the best results for the respective task. The volume elements are preferably cuboids, but hexadecimal or other shapes of volume elements are also possible.

The following specified parameters are still used for networking: a lower and / or upper bound for the edge length of a volume element in each longitudinal direction of a space, the shape of the volume elements and a crosslinking method, e.g. B. "paving" or "free messing".

Instead of an edge length in the longitudinal direction, it is also possible to specify the number of volume elements into which the intermediate space is to be divided in the transverse direction.

All volume elements preferably have the shape of cuboids or at least hexahedra. In this example, the number of volume elements in the transverse direction is 2. In the transverse direction, two volume elements lying next to each other are to be generated. By default, both volume elements have the same edge length in the transverse direction, so that all edges in the transverse direction are 0.8 mm: 2 = 0.4 mm long. Furthermore, in this example, an edge length in the longitudinal direction of 5 mm in flat areas of the space and 4 mm in curved areas is specified.

As an alternative to this, it is not the edge length in the longitudinal direction that is specified, but a lower and / or an upper limit for the ratio of the longest to the shortest edge of a volume element. For example, a ratio of 10 in curved and 12.5 in flat areas of a space is specified. As just explained, the shortest edge length is 0.4 mm. From this, the length of the remaining edges of a volume element is automatically derived from 0.4 mm * 12.5 = 5 mm in curved and 0.4 mm * 10 = 4 mm in flat areas of the layer.

After the networking of the construction is complete, the physical relationships and boundary conditions are added. This step is carried out, for example, with "MEDINA / PostProcessing". An example of such a relationship describes the stress in a finite element depending on the displacement of its nodes. Depending on the displacement of the nodes, an elongation tensor ε of the finite element is determined. A stiffness matrix (“compliance matrix”) D is specified. Between the stress tensor σ of the finite element and the strain tensor ε there is a relationship σ = D * ε.

It is possible that the deformations result from a temperature change ΔT. Let α be the expansion coefficient of the material used for the production of the respective body. Then there is the relationship σ = D * (ε - α * ΔT).

Furthermore, the relationship between the acting force F and the deformation U is determined. From properties of the materials used for the manufacture of the respective body, e.g. B. modulus of elasticity and Poisson number, and a stiffness matrix K of the body is derived from the geometry of the body. The relationship U = K * F exists between the deformation and the acting force. It is possible that some components of U are known, e.g. B. must be zero, and some components of F are known and others are unknown.

After determining the connectable subareas and the gaps between them, the gaps are preferably networked. The networking is not necessarily carried out. It is possible, for. B. also that instead the spaces in the construction are highlighted. A processor can decide whether exactly these gaps should actually become part of an adhesive connection or should be filled with sealing material, and can, if necessary, add further connectable sub-areas or mark sub-areas identified as connectable as non-connectable.

It is also possible that the total volume of the gaps is automatically determined and derived from how a lot of material, e.g. B. adhesive or sealing material, must be filled in these spaces overall. If a sheet is approximated by a surface, the thickness of this sheet is taken into account so that only the volume of the space between this sheet is taken into account, but not the volume of the sheet itself.

After the meshing of the boundary surface F.6 of the body Kl, the central surface Fl of the sheet and the connecting adhesive connection Kl has been completed and the system of equations has been generated, the system of equations is created using a commercial software tool for the finite element method (FEM -Tool) solved.

The expert knows various FEM tools, e.g. B.

- MSC.NASTRAN and MSC.PATRAN, both described at http: // www. mscsoftware. com / products /, queried on February 5, 2003,

For each node of the construction, the solution delivers the value that the physical size assumes in this node. By inserting the function, the values of the physical quantity are calculated in the closest points determined. The solution is evaluated to analyze the construction of the system.

Claims

claims

Method for the automatic detection of connectable surfaces in a technical system, the system comprising several bodies, a joining technology being specified by the use of which a layer can be produced between every two bodies of the system, a computer-available construction of the system which is given for each body of the system comprises at least one surface belonging to the body (Fl, F.2, F.6, F.7), with the steps

- generation of finite elements (100.1, 100.2, 101.1, 101.2, ...) for the surfaces, for each surface pair consisting of two different surfaces (Fl, F.6) of the construction, selection of all element pairs, which each consist of a finite element of one surface and a finite element of the other surface of the surface pair, the distance from one another of which is less than or equal to a predetermined upper limit, - and for each selected element pair decide whether the two finite elements of the element pair can be connected by the joining technology,

- A decision-evaluable decision criterion is used for the decision making, which compares the distances, positions and / or orientations of the two finite elements with given limits.

A method according to claim 1, d a d u r c h g e k e n n z e i c h n e t that when selecting the element pairs of a surface pair

- all nodes (200.1, 200.2, ...) of the finite elements (100.1, 100.2, 101.1, 101.2, ...) of the two surfaces (Fl, F.6) are determined, all node pairs, each consisting of one Node of one surface and a node of the other surface are determined, for each node pair the distance between the two nodes of the pair of nodes is calculated, those node pairs are selected whose nodes have a distance that is less than or equal to is the barrier, and each element pair is determined, one finite element of which has one node of a selected node pair as a node and the other finite element of which has the other node of the same node pair as a node, and

- Determined element pairs can be used as selected element pairs.

Method according to claim 2, characterized in that each determined element pair is preselected when each node (200.1, 200.2, ...) of the one finite element (100.1, 100.2, ...) of the element pair of at least one node (201.1, 201.2, ...) of the other finite element (101.1, 101.2, ...) has a distance that is less than or equal to a predetermined upper limit, each preselected element pair is selected when the distance between the two finite elements of the element pair is less than or equal to the upper bound, and for each unselected element pair it is decided that the two finite elements of the element pair cannot be connected.

Method according to Claim 2, characterized in that each determined element pair is preselected when each node (200.1, 200.2, ...) of the one finite element (100.1, 100.2, ...) of the element pair from all nodes (201.1 , 201.2, ...) of the other finite element (101.1, 101.2, ...) has a distance which is less than or equal to a predetermined upper limit, each preselected element pair is selected when the distance between the two finites Elements of the element pair is less than or equal to the upper bound,

- and it is decided for each unselected element pair that the two finite elements of the element pair cannot be connected. Method according to one of claims 1 to 4, characterized in that when selecting the element pairs

If the distance between the two finite elements of a pair of elements is greater than a predetermined limit, the pair of elements is not selected.

Method according to one of claims 1 to 5, so that when comparing the distance between two finite elements of a pair of elements with a predetermined upper and / or lower bound at least one of the following processes is carried out:

Determining the intersection (240.1) of the two diagonals of one finite element (101.2), determining the intersection (240.2) of the two diagonals of the other finite element (100.1), determining the distance between the two intersections,

Generate a normal (210.1. 210.2, ...) on the one finite element of the element pair, determine the base point (230.23) of the normal in the finite element, determine the intersection (230.1, 230.2, ...) of the Normals with the other finite element, comparing the distance between the base point and the intersection with a predetermined upper and / or lower bound,

Generate a normal (210.1) on one finite element (100.1) and a normal (210.2) on the other finite element (101.1) of the element pair, determine the sum vector (250.1) of the two normals, determine the intersection of a straight line in the direction the sum vector with the other finite element, calculating the distance between the intersection of the straight line with the one and the intersection of the straight line with the other finite element, comparing the distance with a predetermined upper and / or lower bound, for each node (200.4) of the one finite element Elements (100.1) of the pair generating a normal (210.5) through the node (200.4) on the finite element, determining the intersection (230.4) of the normal (210.5) with the other finite element (101.2), comparing the distance between the node (200.4 ) and intersection (230.4) with a given upper and / or lower bound.

Method according to one of claims 5 to 6, so that at least one of the following tests is carried out when deciding on a selected element pair:

Check whether the finite elements of the element pair belong to surfaces of different bodies,

Determining the angle (220.1, 220.2) between the two finite elements of the element pair and comparing the angle with a predetermined upper bound,

Projecting the one finite element (100.1) of the element pair along a projection vector (250.1) and checking whether the projected finite element overlaps with the other finite element (101.1, 101.2) or not,

- Determining the center points (240.1, 240.2, ...) of the two finite elements of the pair of elements, projecting the one finite element along a projection vector (250.1), determining the distance between the center of the projected finite element and the center of the other finite element, comparing the distance with a predetermined upper bound,

Determining the center points (240.1, 240.2, ...) of the two finite elements of the pair of elements, projecting one finite element (100.1) along a projection vector (250.1), determining the distance between the center of the projected finite element and the Center of the other finite element (101.2), determine the length of the longest edge of the two finite elements of the pair, compare the quotient of the distance and the longest edge length with a predetermined upper bound.

8. The method according to claim 7, d a d u r c h g e k e n n z e i c h n e t that

- The projection vector (250.1) as a sum vector from a normal (210.1) on one finite element

(100.1) and a normal (210.2) of the same length on the other finite element (101.1)

- And the angle (220.1, 220.2) between the two finite elements as an angle between a normal

(210.4, 210.3) on one finite element (100.1) and a normal (210.5, 210.2) on the other finite element (101.2).

9. The method according to any one of claims 1 to 8, characterized in that the predetermined limits depend on at least one of the following parameters: a technological parameter of the specified joining technology, the quality of a surface of a body, a technological parameter of a material intended for the production of a body,

- a requirement that applies to all bodies in the system.

10. The method according to any one of claims 1 to 9, d a d u r c h g e k e n n z e i c h n e t that the predetermined joining technology comprises one of the following methods:

- structural gluing,

- assembly glue,

- fold gluing,

- gluing with flanging, spot welding,

- seam welding,

Inserting a sealing layer,

- inserting an insulating layer,

- Insert a spacing layer.

11. The method according to any one of claims 1 to 10, characterized in that different possible joining technologies are specified, for each possible joining technology a decision criterion is specified, which the positions and / or orientations of two finite E- compares elements with specified barriers depending on the joining technology,

and an evaluation of the joining technology is specified, those pairs of finite elements are determined for each joining technology that can be connected by the joining technology, the decision criterion specified for this joining technology being applied to the finite elements of the pair during the determination, an evaluation of the joining technology with respect to the system is determined using an evaluation function which is calculated from the predefined evaluation of the joining technology and the pairs of elements which can be connected to the joining technology, the joining technology is selected for which the highest rating was determined with regard to the system, and the further finite elements are generated in the spaces, which are limited by those element pairs that can be connected with the selected joining technology.

12. The method according to any one of claims 1 to 11, so that further finite elements are automatically generated in the spaces (ZW) which are delimited by the finite elements identified as being connectable.

13. The method according to claim 12, characterized in that the other finite elements in the spaces (ZW) are volume elements, the volume elements are generated in such a way that all spaces (ZW) are completely meshed by volume elements and the meshing is generated using geometric information about the spaces and specifications for the meshing.

14. The method according to claim 12, so that at least one further finite element in an intermediate space (ZW) is a surface element that is perpendicular to an adjacent surface of the construction.

15. The method according to any one of claims 12 to 14, d a d u r c h g e k e n n z e i c h n e t that

a system of equations is set up according to the finite element method, in which the values appear as unknowns, which assume a spatially variable physical size in the nodes of the generated finite elements,

- and the values of the size in the nodes are determined by numerically solving the system of equations.

16. The method according to claim 15, characterized in that for a set of nodes of further finite elements in the interstices (ZW) a closest surface of the construction, a closest finite element of this surface and a closest point on this finite element are determined and equations for physical relationships between the values, which takes the physical size in the set of nodes,

- and the values which the physical quantity generates in the closest points of the surfaces determined for the set and which are used when setting up the equation system.

17. The method according to claim 15 or claim 16, characterized in that for at least one node of the set a function for a physical relationship between the value that the physical quantity takes on the closest point and the values that this size in the nodes of the closest Finite element assumes is generated

- And when setting up the system of equations, the value of the physical quantity in the determined point is eliminated by using the function.

18. The method according to any one of claims 1 to 17, characterized in that the total volume in the spaces (ZW) between all connectable element pairs is determined.

19. Computer program product which can be loaded directly into the internal memory of a computer and comprises software sections with which a method according to one of claims 1 to 18 can be carried out when the product is running on a computer.

20. Computer program product which is stored on a computer-readable medium and which has computer-readable program means which cause the computer to carry out a method according to one of claims 1 to 18.