Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
  • G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F30/00—Computer-aided design [CAD]
  • G06F30/20—Design optimisation, verification or simulation
  • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]

Definitions

• the present invention relates to the production of finite element models and, more particularly, to a method and a device making it possible to make the application of property data of the granularity of a finite element model independent.
• Finite element modeling is a proven technique today. It can numerically compute the behavior of objects that are often very complex. Finite element modeling is based on a division of space according to a mesh composed of finite elements. In addition, when creating a finite element model, a set of property data of the modeled entity is usually attached directly to the elements of the finite element model. These property data may be, by way of example, physical properties of the modeled entity. Such attachment of the property data with the finite element model makes the property data dependent on the granularity of the finite element model.
• finite element models is common for the design of complex assemblies, such as aircraft. Such sets require manipulating complex finite element models.
• the finite element model of an aircraft section such as the central fuselage, can have more than 33,000 finite elements. Given that a set of property data is generally associated with each of the finite elements, it follows that a large volume of property data is to be manipulated for the whole finite element model.
• the design of complex assemblies, such as aircraft is iterative, by the successive increase of the finite element model granularity. In other words, the number of finite elements of the finite element model is modified at each stage of the design.
• the granularity of the finite element model is modified as a function of the calculation (s) to be carried out, the materials and the constructive principles used.
• the property data directly dependent on a particular granularity of the finite element model, must be fully recreated with each change in the granularity of the finite element model.
• This creation of the set of property data must be done even if the new property data attached to a new finite element model is identical to the property data attached to a finite element model from which the new finite element model is derived.
• This constraint comes from the fact that the property data is attached to the finite element model by a number. Since this number is different if the granularity of the element model changes, there is no possibility of linking different sets of property data.
• the present invention solves at least one of the problems discussed above.
• the invention thus relates to a method for producing a finite element model by means of a computer, the model comprising at least one element and modeling a geometrical entity, characterized in that the method comprises the steps of: at. acquiring at least one property data and at least one positioning identifier by means of an interface of the computer in order to store the at least one property data and the at least one positioning identifier in a memory of the computer, the at least one positioning identifier for identifying a position of the at least one property data on the geometric entity; and b) establishing a correspondence between the at least one positioning identifier and at least one element of the finite element model in the computer memory.
• Such a method makes it possible to make the creation of property data independent of the granularity of a finite element model.
• the method also allows the retention of property data information throughout a finite element model enhancement process.
• the method further comprises the step of attaching the at least one property data element with the at least one element of the finite element model for which a correspondence with the positioning identifier of the at least one a property data has been set in the memory of the computer.
• the method further comprises the step of modifying by means of the computer the at least one property data item and / or the positioning identifier according to a correspondence rule.
• the method further comprises the step of generating by means of the computer at least one property data item and / or a positioning identifier according to a correspondence rule.
• the matching rule is determined by a user through the computer interface.
• the correspondence rule is selected from the group consisting of a linear interpolation, a logarithmic interpolation, an average, a weighted average, a thickness calculation based on a volume expression of a predetermined area and an average of the distances between two values.
• a modification of the at least one element of the finite element model modifies the at least one property datum and / or the positioning identifier according to a correspondence rule.
• a modification of the at least one element of the finite element model generates at least one property data and / or a positioning identifier according to a correspondence rule.
• a creation of an element of the finite element model generates at least one property data and / or a positioning identifier.
• the step of acquiring the at least one property data by means of the computer interface is performed from a finite element model.
• the geometric entity is selected from the group consisting of a one-dimensional element and a two-dimensional element.
• the at least one property data item is selected from the group consisting of a normal section, an inertia, a shear section, a torsor, a thickness and a surface value.
• the invention also relates to a method for a device comprising means adapted to the implementation of each of the steps of the method described above.
• the invention also relates to a computer program comprising program code instructions for performing the steps of the method described above, when said program is executed on a computer.
• the program is in the form of a product recorded on a support readable by a computer system, comprising programmed code elements.
• FIG. 1 schematically illustrates an example of apparatus for implementing the invention
• FIG. 2 schematically illustrates an example of attachment of the property data of a geometric entity to a finite element model
• FIG. 3 schematically illustrates an example of different modules for the use of the invention
• FIG. 4 schematically illustrates a first example of the application of the invention to a one-dimensional element
• FIG. 5 schematically illustrates a second example of the application of the invention on a one-dimensional element
• FIG. 6 schematically illustrates a third example of the application of the invention to a one-dimensional element
• FIG. 8 schematically illustrates a first example of the application of the invention on a two-dimensional element
• FIG. 9 schematically illustrates a second example of the application of the invention to a two-dimensional element
• FIG. 10 schematically illustrates a third example of the application of the invention on a two-dimensional element.
• the invention relates to the realization of finite element models and, more particularly, to a method making it possible to make the creation of property data independent of the granularity of a finite element model.
• Figure 1 illustrates an example of apparatus 100 adapted to implement the invention, such as a microcomputer or a workstation.
• the apparatus 100 comprises a communication bus 102 to which are connected: a central processing unit 112 such as a microprocessor; a ROM 104 or Read OnIy Memory ROM (ROM), which may include one or more programs "Prog", “Progi” and “Prog2”; a Random Access Memory (RAM) memory 106, comprising registers adapted to memorize variables and parameters created and modified during the execution of the aforementioned programs; and, a communication interface 108 connected to a distributed communication network 110, for example the Internet or an intranet network, the interface being able to transmit and receive data.
• a central processing unit 112 such as a microprocessor
• ROM 104 or Read OnIy Memory ROM (ROM) which may include one or more programs "Prog", “Progi” and “Prog2”
• RAM Random Access Memory
• a communication interface 108 connected to a distributed communication network 110, for example the Internet or an intranet network, the interface being able to transmit and receive data.
• the apparatus 100 may optionally have one, more or all of the following devices: a screen 116 for displaying data and / or serving as a graphical interface with the user who can interact with the programs according to the invention, using a keyboard 118 or any other device, as for example a mouse 114; a hard disk 120 may include programs and / or data, including data processed or to be processed according to the invention; a removable storage media reader 122 adapted to receive a removable storage medium 124 and to read or write to it data processed or to be processed according to the invention.
• the communication bus allows communication and interoperability between the various elements included in the apparatus 100 or connected to it.
• the representation of the bus is not limiting and, in particular, the central unit is able to communicate instructions to any element of the apparatus 100, directly or via another element of the apparatus 100.
• the executable code of the program or programs enabling the apparatus 100 to implement the processes according to the invention may be stored, for example, in the hard disk 120 or in the read-only memory 104.
• the removable storage medium 124 may contain data as well as the executable code of the aforementioned programs which, once read by the apparatus 100, can be stored in the hard disk 120.
• the executable code of the programs can be received via the communication network 110, via the interface 108, to be stored identically to that described above.
• the removable storage medium may be, for example, a floppy disk, a compact disc (CD-ROM) or a memory card.
• program or programs may be loaded into one of the storage means of the device 100 before being executed.
• the central unit 112 controls the execution of the instructions or portions of software code of the program or programs according to the invention, instructions which are stored in the hard disk 120, in the read-only memory 104 or in the other aforementioned storage elements.
• the program or programs stored in a non-volatile memory for example the hard disk 120 or the read-only memory 104, are transferred to the random access memory 106 (RAM), which then contains the executable code of the one or more programs according to the invention, as well as registers for storing the variables and the parameters necessary for the implementation of the invention.
• RAM random access memory
• the apparatus comprising the device according to the invention may also be a programmed apparatus.
• the instructions of the program or programs implementing the invention may, for example, be implemented in a programmable or specific integrated circuit (Application-
• ASIC Specific Integrated Circuit
• FIG. 2 illustrates certain steps implemented by the invention to obtain a finite element model 204 modeling a geometrical entity 200, to which property data 208 is attached while rendering the property data 208 independent of the finite element model. .
• the property data 208 is attached to the geometric entity 200 by means of at least one property data positioning identifier 206.
• Positioning identifier 206 identifies the position of at least one property data item 208 on geometric entity 200.
• property data item 208 is a set of values representing the normal section of an item. to one dimension.
• the property data 208 may include information relating to the physical characteristics of an element, or even data useful for the creation of a mesh, for example, data facilitating the implementation of a topological numbering or facilitating the study by any trade (optimization, vibration, thermal, etc.) or traceability (source of the physical data: section in solid, interpolation, specific study, hypothesis, validation plane, etc.) .
• Such information may be, by way of example, the normal section, the inertia, the sheared section, a torsor or a thickness.
• the geometrical entity 200 can be any entity that can be modeled, in particular by geometric coordinates.
• the geometrical entity 200 can represent a simple complexity element, with one or two dimensions, such as a beam or a surface, or even an element of greater complexity, composed for example of a combination of elements of simple complexity, such as an aircraft section.
• a property data acquisition 208 and a positioning identifier 206 of these data is performed.
• the positioning identifiers 206 identify the position property data 208 on the geometrical entity 200 on the basis of which a finite element model 204 is realized.
• the property data 208 is independent of the finite element model 204, insofar as the positioning of the property data 208 is established with respect to the geometric entity 200, by means of at least one positioning identifier 206 .
• the property data 208 is attached to the elements of the finite element model 204 by using the positioning identifier 206 to identify the elements of the finite element model 204 to which the property data 208 is to be attached.
• a correspondence is established between the positioning identifier 206 of the geometrical entity 200 and the element or elements of the finite element model 204 modeling the geometrical entity 200.
• the property data 208 is attached with the elements of the finite element model 204 for which a correspondence with the positioning identifiers 206 of the property data 208 has been established.
• a matching rule 212 may be used.
• the matching rule is used to modify or create a new property data value which is then attached with the finite element model 204.
• the matching rule 212 also makes it possible to modify or create a positioning identifier of the property. property data value changed or created.
• the correspondence rule 212 can modify or create one or more new property data values using the already known property data values 208. Different calculation methods can be applied to the property data values 208 already known to modify or create the new property data value (s). For example, these calculation methods can be linear interpolation, logarithmic interpolation, average or weighted average.
• the property data 208 is constituted by three values representing the normal section of an element and an identifier of positioning 206 to identify the portion of the geometric entity 200 to which the property data 208 is attached. A correspondence between the positioning identifier 206 and the elements of the finite element model 204 is then established to identify to which elements of the finite element model 204 the property data 208 is to be attached.
• the three values of the normal section of the geometrical entity 200 respectively 0, 0.5 and 1 are attached to elements at the positions P1, P6 and P10, respectively, of the finite element model 204.
• the positions of the elements P1 to P10 are positions resulting from a mesh refinement.
• the matching rule 212 is used to generate property data that is attached to elements at positions P2, P3, P4, and P5 of the finite element model 204.
• FIG. 3 schematically illustrates an example of different modules for the use of the invention.
• the property data module 300 manages the property data to be attached to a finite element model 318 generated, for example, via computer-aided design (CAD) software or software.
• CAD computer-aided design
• CAE computer-aided engineering
• the property data module 300 enables the implementation of the present invention in a commercially available CAD or CAE software such as, for example, CATIA, developed by Dassault Systdiags, coupled to software such as SIMXpert, developed by the company MSC. Software.
• Property data can be stored directly in the CAD or CAE software or on an external database. It may be easier to use the property data if it is stored in an external database, especially if the volume of property data is important. Such an external database may be accessible, for example, via an API (Application Programming Interface in English) thus relying on an open computing architecture.
• Property data can also be attached to a real geometry or an image of the geometry.
• Some CAD or CAE software includes a module for reading a geometry and thus creating an intermediate geometry image.
• the recovery of the property data can be carried out by a first recovery method 306 or a second recovery method 332.
• the first recovery method 306 allows the importation 304 of property data contained in an XML file 302.
• the use of the XML format allows to rely on a data organization standard, however other file formats could be used, such as, for example, the CVS format.
• the second recovery method 332 allows the retrieval of property data from an existing finite element model.
• a previous property data set 338 is then captured by a property data capture module 336. Once captured, the property data is then constructed by a property data building module 334.
• the modification of the property data can be carried out, according to a first alternative, by a property data modification module via graphic interface 316.
• the modified property data is then provided to the property data module 300.
• a method of using an external file 314 can be used.
• the method of using an external file 314 makes it possible to provide the property data module 300 with property data created by a property data creation module.
• this module can be an optimization module, a sizing module or a CAD-calculation link module or a CAE-caicui link module.
• the interaction between the property data creation module and the property data module 300 is via an XML file 312 which can be modified by an export module 310.
• An update module 308 updates the property data module 300 to reflect the changes made to the modified XML file 312 by a property data creation module.
• the application of the property data 322 to a finite element model 318 is performed by the property data matching and attachment module 320.
• the property data matching and attachment module 320 attaches the property data. of the property data module 300 with the finite element model 318.
• the property data matching and attachment module 320 may use at least one matching rule, for example, the granularity of the data.
• property data module property 300 is different from the granularity of the finite element model 318.
• the finite element model 318 on which the property data has been attached is modifiable through a finite element model 324 element modification module.
• a new property data set 326 is then created. Further, the changes are captured by the property data capture module 336.
• the new property data is constructed by the property data building module 334 which updates the property data module 300. Moreover, the capture of the property data by the module 336 can be performed from a patch construction module 330 on the basis of 328 patch definition. The notion of patch will be detailed later in this document.
• Figure 4 schematically illustrates a first example of the application of the invention to a one-dimensional element, in particular the attachment of property data with a finite element model.
• a one-dimensional element may be a bar or a beam.
• the behavior of the geometric line in finite element model is a bar.
• the bar is characterized, in this example, by a normal section.
• the property data attached to the geometric entity contains normal section values positioned at different locations of the geometric entity. In this example, two normal section values form the property data.
• the value of the normal section is represented by a vertical bar whose length is proportional to the value.
• a correspondence rule 402 is used to generate new values of geometry data to be attached to the finite element model 404.
• the five bars, positioned between the two bars positioned at each end, represent normal section values interpolated according to a correspondence rule 402 using linear interpolation.
• a normal section value is attached to each element of the finite element model 404.
• creating the new item also changes the values attached to related items.
• a matching rule is used to generate the new data value of the new item.
• An update of the property data values attached to the related items, modified as a result of the creation of the new item, is also performed.
• the property data are, at each modification or creation of elements of the finite element model, updated.
• FIG. 5 schematically illustrates a second example of the application of the invention to a one-dimensional element, in particular the bijective updating of the property data between the geometrical entity and the finite element model.
• the behavior of the geometric line in finite element model is a bar.
• the bar is characterized, in this example, by a normal section.
• the property data attached to the geometric entity contains normal section values positioned at different locations of the geometric entity. In this example, three normal section values form the property data.
• the The value of the normal section is represented by a vertical bar whose length is proportional to the value.
• a property data modification 516 is performed resulting in the modification of a property data value attached to an element of the finite element model 514. Moreover, the updating of property data 520 results in the creation of a new value of property data and a positioning identifier of the new value on the geometric entity 522. Thus, the property data, at each modification or creation of property data value, can be updated by relation to the geometric entity.
• FIG. 6 schematically illustrates a third example of the application of the invention to a one-dimensional element, in particular a property data positioning identifier on the geometrical entity not depending solely on a curvilinear abscissa on a line geometric.
• one of the positioning identifiers depends on the positioning of an outer element.
• the outer member may be a stiffener positioned in the transverse direction of the geometric line.
• the behavior of the geometric line in finite element model is a bar.
• the bar is characterized, in this example, by a normal section.
• the property data attached to the geometric entity contains normal section values positioned at different places of the geometric entity.
• four normal section values form the property data.
• the value of the normal section is represented by a vertical bar whose length is proportional to the value.
• the intersection of the outer element with the geometric line can model, for example, the intersection between a vertical stiffener and a horizontal stiffener of a stiffened panel.
• a matching rule 628 is used when establishing a correspondence between the positioning identifiers and the elements of a finite element model 630, according to the application example described previously in FIG. 5.
• a modification of the geometrical entity 632 results in a modification of the length of the geometric line and leads to the geometric entity 634.
• a finite element model 638 is then generated, on which the update of the property data 636 is reflected.
• the modification of the geometrical entity 632 relates to the modification of the length of the geometric line.
• the Property data 636 would be updated similarly if the modification of the geometrical entity 632 concerned a modification of the positioning of the outer element.
• Fig. 7 schematically illustrates a geometrical entity representing a surface or, in other words, a geometric surface on which property data can be attached.
• the identification of the property data positioning of a geometric surface can be performed in two levels, by first and second property data positioning identifiers.
• a first property data positioning identifier is based on the cutting of a geometrical surface by a first series of lines GEa identified by an index "i", each line then being identifiable according to the GEa 2 terminology, and than by a second set of lines
• each line then being identifiable according to the GEb terminology,. It then becomes possible to use a surface bounded by the lines GEa and GEb as positioning identifier to identify the positioning of property data on each portion of the geometric surface 702.
• a second property data positioning identifier also called property value localization, making it possible to locate on each portion of the geometric surface 702, identified by an intersection 700, the property data. from a point on the surface 704.
• the positioning of the property data of the point of the surface 704 is then established on this surface portion via a two-dimensional coordinate system (u, v), where 0 ⁇ u ⁇ 1 and 0 ⁇ v ⁇ 1 in this example.
• FIG. 8 schematically illustrates a first example of the application of the invention to a two-dimensional element, in particular the attachment of 18 property data with a finite element model.
• a two-dimensional element can be a panel or a shell.
• a geometrical entity 800 is a geometric oriented surface.
• the property data, in this example of the surface values 804 of the geometrical entity 800, are positioned by a surface value positioning identifier.
• a plurality of one-dimensional elements 802, for example stiffeners, is arranged on the geometrical entity 800.
• the behavior of the geometric surface as a finite element model is a plate.
• the plate is characterized, in this example, by a thickness.
• the surface value 804 attached to the geometric entity contains the thickness value positioned on the geometric entity.
• the position of the surface value 804 on the geometric entity is identified by an identifier of the surface.
• a correspondence between the surface and the elements of finite element model 806 is established.
• the surface value 804 of the geometrical entity 800 is then attached to the finite element model 806.
• FIG. schematically a second example of the application of the invention to a two-dimensional element, in particular the use of patches for associating several property data to a geometric entity.
• This example also illustrates the attachment of patches to a finite element model.
• a geometrical entity 900 is a geometric oriented surface.
• the surface values 904 of the geometrical entity 900 are positioned by a surface value positioning identifier.
• a plurality of one-dimensional elements 902, for example stiffeners, is disposed on the geometrical entity 900.
• patches of which there are three in this example, PATCH 1, PATCH2 and PATCHS, are positioned on the geometrical entity 900.
• Each patch includes at least one property data associated with a portion of the geometrical entity 900.
• Property data may differ from patch to patch.
• the property data of each of the patches are contained in separate files, the files being in a format structured data, for example the XML format. The positions of these three patches are identified by patch placement identifiers.
• the position of the PATCH 1 is identified by the positioning identifiers of a zone, the zone being the closed contour composed of the joined edges of the lines GEa ; , GEb y , GEa and GEb; the position of the PATCH2 is identified by the positioning identifiers of a second zone; and the position of the PATCH3 is identified by the positioning identifiers of a third zone.
• a correspondence between the patch placement identifiers on the geometrical entity 900 and the elements of the finite element model 906 is established.
• the property data of each of the patches of the geometrical entity 900 are then attached to the finite element model 906.
• a correspondence between the surface value positioning identifiers and the elements of the finite element model 906 is established.
• the surface values 904 of the geometrical entity 900 are then attached to the finite element model 906.
• FIG. schematically a third example of the application of the invention to a two-dimensional element, in particular the use of patches and property value locations for associating several property data to a geometric entity.
• This example also illustrates the attachment of property value patches and locations to a finite element model.
• a geometric entity 1000 is a geometric oriented surface.
• the surface values 1004 of the geometrical entity 1000 are positioned by a surface value positioning identifier.
• a plurality of one-dimensional elements 1002, for example stiffeners, is disposed on the geometrical entity 1000.
• PATCH2 and PATCH3 are positioned on the geometric entity 1000.
• Each patch has at least one property data associated with a portion of the geometric entity 1000.
• the property data may differ from a patch to the other.
• the property data of each of the patches are contained in separate files, the files being in a structured data format, for example the XML format.
• the positions of these three patches are identified by patch placement identifiers.
• the position of the PATCH 1 1016 is identified by the positioning identifiers of a zone; the position of the PATCH2 is identified by the positioning identifiers of a second zone; and the position of the PATCH3 is identified by the positioning identifiers of a third zone.
• the PATCH 1 1016 is composed of several property value locations.
• each of the property value locations has its own thickness value, the value of the property value location may depend on one or more characteristics of the geometric entity 1000, for example the center of gravity, a calculation point localization, a composite fold release evolution, or any other criterion allowing a user to retain data essential to his activity.
• the positions of property value locations in a patch are identified by property value location positioning identifiers.
• a correspondence between the property value location positioning identifiers and the elements of the finite element model 1006 is established.
• the values of the property value locations are then attached to the finite element model 1006.
• a correspondence between the patch placement identifiers on the geometrical entity 1000 and the elements of the finite element model 1006 is established.
• the property data of each of the patches of the geometrical entity 1000 are then attached to the finite element model 1006.
• a correspondence between the surface value positioning identifiers and the elements of the finite element model 1006 is established.
• the surface values 1004 of the geometrical entity 1000 are then attached to the finite element model 1006.
• the mapping and the attachment of the property data of the plurality of one-dimensional elements 1002 to the model by finite elements 1006 is performed according to the application described in Figures 4 to 6.
• a match rule may be used to generate new property value location values to be attached to the finite element model 1006.
• An example of a matching rule could be a thickness calculation based on a volume expression of a predetermined area.
• a choice is then proposed to the user, for example by proposing the value of the property value location. the closest or even one of the patch property data in which the property value location is set.
• This choice can also be made automatically by a matching rule.
• An example of a matching rule could be a prorated average of the distances between two property value locations.
• a new property value location value attached to an element of the finite element model 1006 can then be created.

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