DESC:FIELD OF THE INVENTION

[001] The present invention relates generally to finite element analysis, and more particularly, to systems and methods for modeling fasteners in a structure for finite element analysis.

BACKGROUND OF THE INVENTION

[002] Finite element analysis (FEA) is a computerized method widely used in used in industry to model and solve engineering problems relating to complex systems. With the advent of the modern digital computer, FEA has been implemented as FEA software. Basically, the FEA software is provided with a model of the geometric description and the associated material properties at each point within the model. In this model, the geometry of the system under analysisis represented by solids, shells and beams of various sizes, which are called elements. The vertices of the elements are referred to as nodes. The model is comprised of a finite number of elements, which are assigned a material name to associate with material properties. The model thus represents the physical space occupied by the object under analysis along with its immediate surroundings. The FEA software then refers to a table in which the properties (e.g., stress-strain constitutive equation, Young's modulus, Poisson's ratio, thermo-conductivity) of each material type are tabulated. Additionally, the conditions at the boundary of the object (i.e., loadings, physical constraints, etc.) are specified. In this fashion a model of the object and its environment is created.

[003] Finite element analysis is used in a variety of applications including solid mechanics, fluid mechanics, biomechanics, heat transfer, geomechanics, aeromechanics, coupled systems, chemical reactions, acoustics, and electric and magnetic fields.

[004] Finite element analysis software adapted for use with solid mechanics is available from a wide variety of commercial suppliers. FEA begins by using finite element software to generate a finite element model of the system. In this model, the component is reduced into a number of finite elements. A simulated load or other influence is applied to the system and the resulting effect is analyzed using conventional mathematical methodologies.

[005] Finite analysis programs that provide solutions to specific problems are commercially available. For example, ABAQUS® is available from Hibbitt, Karlsson and Sorenson, Inc., of Pawtucket, R.I. to model structural mechanics and nonlinear heat transfer. ANSYS® is available from Ansys, Inc., of Canonsburg, Pa. to model structural mechanics and heat transfer. ASTMA is public domain software available from the National Aeronautics and Space Administration (NASA) that models heat transfer and ablation. I-DEAS is available from Structural Dynamics Research Corporation of Milford, Ohio to provide pre and post-processing images of the model. SINDA from Network Analysis, Inc., of Chandler, Arizona models heat transfer. TEX CHEM models chemical reactions and chemical equilibrium. RECESS is a program developed by Thiokol Propulsion of Brigham City, Utah to model internal ballistics. CDCA is a computational fluid dynamics program developed by Pennsylvania State University to model crack combustion where a fracture in a propellant affects burn condition. CCM is a similar computational fluid dynamics program available in the public domain, and is available from the Air Force Research Laboratory (AFRL).

[006] FEA is becoming increasingly popular with automobile manufacturers for optimizing both the aerodynamic performance and structural integrity of vehicles. Similarly, aircraft manufacturers rely upon FEA to predict airplane performance long before the first prototype is ever developed.

[007] During the design of new components like aircraft, train, heavy engineering objects today’s Finite Element Simulations are used for studying the alternative configurations of design. Typically a conceptual geometry is created in a Computer Aided Design tool and further analysed for strength under various load cases. Meshing is major Time and Effort consuming process performed using hyper mesh, Patron, etc which essential to make the components into infinitesimal finite element.

[008] Modern aircrafts can include several fasteners, such as rivets, bolts etc. General purpose of a fastener such as a bolted joint is to clamp two or more parts together. The clamping force is achieved by applying torque to the bolt head and the nut; the mechanical advantage of the wrench and threads allows one to actually stretch the section of the bolt between the head and the nut (an area known as the grip), creating tension in the bolt. This tension is known as pretension because it exists before any other forces are applied to the joint. It squeezes the mating parts together, and if the joint is designed, assembled, and maintained properly, prevents the mating parts from separating or sliding under normal loads.

[009] In the scenario of a high velocity impact of the aircraft such as a bird strike the fasteners are expected to take both shear and tensile loads. Similarly the failure of aircraft structures will be mainly expected at fastener locations.

[0010] So we have to define connectors (fastener) with coupled behaviour i.e. fastener can fail due to shear load or tensile load or both shear and tensile load .To do this we had to define both tensile and shear damages, stiffness for all connectors with respect to their orientation. For example in the shear plane (if shear plane is X-Y) the software calculates derived component of shear load (resultant of shear FX and FY) and compare it with allowable shear to define whether connector has damaged or not.

[0011] FIG. 1 shows an aircraft wing which has large number of fasteners. In most cases the aircraft wings fail at the fastener and due to which the whole structure fails. In this model the more than 1800 fasteners have to be assigned defining the stiffness, damages to fasteners with respect to their orientation accurately for such large number of fasteners.

[0012] In the FEA the modeling of fasteners is overlooked and in most cases they are not made on the model. Some FEA tools also allow modeling the fasteners, but the complexity involved in modeling the fasteners makes it very difficult and time consuming. This is one of the main reasons of overlooking the fasteners in the FEA.

[0013] In view of the disadvantages inherent in the available systems and methods for modeling fasteners in a structure for finite element analysis, there exists need for a system and method for creating fasteners in a structure for finite element analysis which overcomes the problems in the prior art in an easy and effective way which is inexpensive, compact and capable of overcoming disadvantages inherent in prior art in a cost effective, secure, and environmental friendly manner. The present invention fulfils this need and provides further advantages as described in the following summary.

SUMMARY OF THE INVENTION

[0014] In view of the foregoing disadvantages inherent in the prior arts, the general purpose of the present invention is to provide an improved combination of convenience and utility, to include the advantages of the prior art, and to overcome the drawbacks inherent therein.

[0015] A primary objective of the present invention is to provide a system and method for modelling a fastener in a structure for finite element analysis having advantages not taught by the prior art.

[0016] In one aspect, the present invention provides a method of modeling a fastener in a structure for finite element analysis. The method comprises collecting and storing a property information about a plurality of fasteners, providing a structure finite element input file including a finite element model of the structure along with location of each of the fastener of the plurality of fasteners, creating node ID for each of the fasteners at the fastener location in the finite element model, creating fastener element at each of the fastener location in the finite element model, writing a input file including the node ID and an element ID of each of the fastener elements, compiling the property information, the node ID, the element ID for each of the plurality of fasteners into a fastener file, generating a fastener finite element input file by grouping the information from the fastener file into a required format for the finite element analysis and combining the fastener finite element input file with the structure finite element input file for conducting the finite element analysis.

[0017] In another aspect of the present invention the the property information includes a type, a diameter, a length, a orientation, a material, a stiffness, a Young’s Modulus of Elasticity, a thickness or a combination thereof.

[0018] In yet another aspect of the present invention the steps of creating the node ID and creating the fastener elements are performed by a finite element mesh creating software.

[0019] In another aspect of the present invention the step of compiling is performed by using a spreadsheet application. In a preferred embodiment, the spreadsheet application is Microsoft Excel.

[0020] In another aspect of the present invention, the step of generating the fastener finite element input file is performed using a Macro programming. In one preferred embodiment, the Macro programming is done using Visual Basic for Applications (VBA) in Microsoft Excel.

[0021] In yet another aspect of the present invention, further includes grouping of the plurality of fasteners based on the property information.

[0022] In yet another aspect, the present invention provides a system for modeling a fastener in a structure for finite element analysis using the method of the present invention.

[0023] These together with other aspects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The advantages and features of the present invention will become better understood with reference to the following more detailed description taken in conjunction with the accompanying drawings in which:

[0025] FIG. 1 illustrates an aircraft wing having large number of fasteners;

[0026] FIG. 2 illustrates a flowchart of the method of modeling a fastener in a structure for finite element analysis, according to one embodiment of the present invention;

[0027] FIG. 3 illustrates the orthodontic bracket assembly used in an orthodontic appliance, according to one embodiment of the present invention;

[0028] FIG. 4 illustrates the lower tube in different position, according to one embodiment of the present invention; and

[0029] FIG. 5 illustrates the closed and open lower tubes, according to one embodiment of the present invention.

[0030] Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

[0031] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details.

[0032] As used herein, the term ‘plurality’ refers to the presence of more than one of the referenced item and the terms ‘a’, ‘an’, and ‘at least’ do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

[0033] In an exemplary embodiment, the present invention provides an orthodontic bracket assembly. The orthodontic bracket assembly of the present invention may be used for mass production in an easy, cost effective, environment friendly and productive way.

[0034] It is to be understood that the improvements of the present invention are applicable to any of a number of orthodontic brackets, other than those which are specifically described below. Such orthodontic brackets will be readily understood by the person of ordinary skill in the art, and are achievable by causing various changes that are themselves known in state of the art.

[0035] Reference herein to “one embodiment” or “another embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

[0036] Referring to FIG. 2 that illustrates a flowchart of the method 100 of modeling a fastener in a structure for finite element analysis, according to one embodiment of the present invention. The structure may be an object with fasteners which has to be subjected to FE analysis. The structure may be a mechanical component or a machine part. In one embodiment the structure is a wing of an aircraft with large number of fasteners as shown in FIG. 1. The fastener may include nuts bolts, threaded screws, rivets or similar fasteners which mechanically joins or affixes two or more objects together.

[0037] The method 100 starts with step 110 of collecting and storing property information about a plurality of fasteners. The information related to different types of fasteners which are used for joining most of mechanical objects together are collected and saved in a database. In one embodiment of the present invention, the property information includes type of fastener such as rivet, bolt, nut, threaded bolt etc. Information like the diameter, length, orientation, material, stiffness, shape, stack thickness, Young’s Modulus of Elasticity, thickness of each of the fasteners. The property information may be collected from a wide variety of fastened parts in different structures and their properties are identified which will be helpful in finite element analysis of a structure. These properties are then saved for using in cases where similar fasteners are used.

[0038] In one embodiment of the present invention, the property information is stored in a database. The database may be a simple file or a database in cloud from where the property information for fasteners may be pulled as per the requirement.

[0039] Now in step 120 a structure finite element input file including a finite element model of the structure along with location of each of the fastener of the plurality of fasteners is provided. The structure finite element input file may be an input for finite element analysis software such as Hypermesh or ANSYS or ABAQUS or any similar software. The FE Model of the structure may be made and the locations of the fasteners are known. In an alternative embodiment the location information of the fasteners may be provided as a separate file. This separate file along with the FE model provided a FE model of the structure whose FE analysis is to be done and the location information provides the details about the location and orientation of the fasteners on the structure.

[0040] Now node ID for each of the fasteners at the fastener location in the finite element model of the structure is created in step 130. Nodes are created at each of the fastener locations and node IDs are created as shown in FIG. 3. And in step 140 fastener elements at each of the fastener location in the finite element model of the structure is created as shown in FIG. 4. In one embodiment of the present invention, the steps of creating the node ID and creating the fastener elements are performed by a finite element mesh creating software such as HYPERMESH.

[0041] In step 150 an input file is created which includes the node ID and an element ID of each of the fastener elements. The fastener elements in the FE model of the structure may have Node IDs and element IDs each. This data is extracted from the FE mesh and then saved in the input file.

[0042] Now at step 160 the property information, the node ID and the element ID for each of the plurality of fasteners is compiled into a fastener file. The information about fastener elements from the database of property information, location information of the fasteners, node ID, element ID for all of the fasteners in the structure are compiled at one place in the fastener file.

[0043] In one embodiment of the present invention, the step of compiling is performed by using a spreadsheet application such as Microsoft Excel. The fastener file may a Microsoft Excel file which includes the property information about the fasteners, location of fasteners, node ID, element ID at one place.

[0044] Now at step 170 a fastener finite element input file is generated by grouping the information from the fastener file into a required format for the finite element analysis. The information from the fastener file is processed to prepare the fastener finite element input file which is a file which can be used as input to perform the finite element analysis.

[0045] The fastener finite element input file is combined with the structure finite element input file for conducting the finite element analysis in step 180. Both the files are combined into a single finite element input file containing the structure with the fasteners modeled with its orientation and property information for FE analysis.

[0046] In one embodiment of the present invention, the step of generating the fastener finite element input file is performed using a Macro programming such as Visual Basic for Applications (VBA) in Microsoft Excel. Now after running the macro with the details of the fasteners the excel file is used to prepare input file and fed to the FEA software tool to generate the structure along with the fasteners. Final structure with correctly oriented fasteners along with their damage properties is as shown in FIG. 5.

[0047] The generated FE model may then be used in the FEA to show the correct results considering the fastener behaviors.

[0048] In one embodiment of the present invention, the method 100 further further includes grouping of the plurality of fasteners based on the property information. Fasteners groups according to orientation, diameter and material using excel based macro may be defined in a format as shown below:

[0049] In another embodiment, the present invention further provides a system for modeling a fastener in a structure for finite element analysis using method 100 of the present invention.

[0050] In one embodiment of the present invention the system and method may be implemented using macro of Excel and this is used to generate the input file of standard FEA software ready to run the FEA.

[0051] In another alterative embodiment the system and method of the present invention may be implemented as a module of FEA software or as standalone software.

[0052] The system and method of the present invention includes the following advantages:
• Eliminates the need to model each and every fastener manually
• Groups similar fastener type
• Groups same fastener type having same dimensions and properties
• Reduce human participation for meshing of the fasteners
• Simplifies the FE modelling by supplies fastener information using a file generated by the present system and method
• Any addition of fasteners can be automatically taken care
• Re adjust the mesh due to fastener points,
• Now this method can be used again and again whenever there is change in design saving a lot of time and would help in modeling accurate fastener behaviour for large number of fasteners
• Same method can be used for any software by changing the syntax for creation for fastener and damage of fastener available in that particular software.
• By using this tool 70 % of working time may be saved as compared to convention method

[0053] Although a particular exemplary embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized to those skilled in the art that variations or modifications of the disclosed invention, including the rearrangement in the configurations of the parts, changes in sizes and dimensions, variances in terms of shape may be possible. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as may fall within the spirit and scope of the present invention.

[0054] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions, substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but is intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:We Claim:

1. A method for modeling a fastener in a structure for finite element analysis, comprising the steps of:
- collecting and storing a property information about a plurality of fasteners;
- providing a structure finite element input file including a finite element model of the structure along with location of each of the fastener of the plurality of fasteners;
- creating a node ID for each of the fasteners at the fastener location in the finite element model of the structure;
- creating a fastener element at each of the fastener location in the finite element model of the structure;
- writing a input file including the node ID and an element ID of each of the fastener elements;
- compiling the property information, the node ID, the element ID for each of the plurality of fasteners into a fastener file;
- generating a fastener finite element input file by grouping the information from the fastener file into a required format for the finite element analysis; and
- combining the fastener finite element input file with the structure finite element input file for conducting the finite element analysis.

2. The method for modeling a fastener according to claim 1, wherein the property information includes a type, a diameter, a length, a orientation, a material, a stiffness, a Young’s Modulus of Elasticity, a thickness or a combination thereof.

3. The method for modeling a fastener according to claim 1, wherein the steps of creating the node ID and creating the fastener elements are performed by a finite element mesh creating software.

4. The method for modeling a fastener according to claim 1, wherein the step of compiling is performed by using a spreadsheet application.

5. The method for modeling a fastener according to claim 4, wherein the spreadsheet application is Microsoft Excel.

6. The method for modeling a fastener according to claim 1, wherein the step of generating the fastener finite element input file is performed using a Macro programming.

7. The method for modeling a fastener according to claim 6, wherein the Macro programming is done using Visual Basic for Applications (VBA) in Microsoft Excel.

8. The method for modeling a fastener according to claim 1, wherein the collecting and storing of the property information is done in a database.

9. The method for modeling a fastener according to claim 1, further includes grouping of the plurality of fasteners based on the property information.

10. A system for modeling a fastener in a structure for finite element analysis using method of any of the preceding claims.