Finite Element Analysis (FEA in Mechanica)

1、FCAL NPI Finite Element Analysis (FEA) Standard Work DocumentRev 1.0FCAL NPI Finite Element Analysis (FEA)Contents1.GENERAL31.1Basic Introduce for Mechanica31.2References / Training Material for Mechanica42.FEA PROCESS IN MECHANICA42.1Develop Models52.1.1Simplify Models52.1.2Assign Materials52.1.3Mo

2、dels Idealizations52.1.4Create Constraints/Loads62.1.5Create Connections62.1.6Generate Meshes72.2Run Solvers72.2.1Define Analyses72.2.2Run Analyses82.2.3Review Results82.3Optimize Models92.4.1Standard Design Study92.4.2Sensitivity Design Study92.4.3Optimization Design Study92.4.4Upgrade Models103.FE

3、A REPORT10FCAL MGET Finite Element Analysis (FEA)1. GENERAL Finite Element Analysis (FEA) is a method to computationally model reality in a mathematical form to better understand a highly complex problem. By using FEA, you can find fault points within your designs, simulate ideas as you think of the

4、m, and even quantize and optimize them without spending money or effort actually building anything.There are many software used for FEA, such as ANSYS, LS-DYNA, DYNAFORM, ABAQUS, Cosmosworks in Solidworks, and Creo Elements/Pro Mechanica in Pro/E etc. But here FEA in this document is only based on C

5、reo Elements/Pro Mechanica. 1.1 Basic Introduce for MechanicaCreo Elements/Pro Mechanica is a multi-discipline CAE (Computer Aided Engineering) tool that enables to simulate the physical behavior of a model and to understand and improve the mechanical performance of the design. It directly calculate

6、 stresses, deflections, frequencies, heat transfer paths, and other factors, showing how the model under analysis will behave in a test lab or in the real world.The Creo Elements/Pro Mechanica product line features two modules, Structure and Thermal, each of which solves for a different family of me

7、chanical behaviors. Structure focuses on the structural integrity, while Thermal evaluates heat-transfer characteristics.There are 2 Basic operating modes are available in Creo Elements/Pro Mechanica, a) Integrated ModeThe product offers the convenience and power of Creo Elements/Pros parametric fea

8、ture-creation technology coupled with the full range of Mechanicas solution software. Mechanica Lite (Not common application)It is the limited functionality, trial version of Mechanica. Mechanica Lite for part or assembly only models with upto 200 surfaces. Be ability to access Creo Elements/Pro Mec

9、hanica Lite with a Creo Elements/Pro license. Native Mode It enables to run integrated mode using Mechanicas adaptive P-code functionality. Native mode allow to create modeling entities like loads, constraints, idealizations, connections, properties, and measures. In this mode, Mechanica meshes anal

10、ysis model with P-code elements and uses its own adaptive solvers to find a solution.It is default mode in Mechanica. FEM Mode (Not common application)It enables to run integrated mode using Mechanicas finite element modeling functionality instead of its P-code functionality. It enables to create FE

11、M modeling entities like loads, constraints, and idealizations. It also enables to mesh the analysis model with H-code elements, run various types of finite element analyses including NASTRAN, ANSYS, and so forth, and review the results of the run. Activate FEM mode by selecting the FEM Mode toggle

12、on the Model Type dialog box before you enter Structure or Thermal in integrated mode.b) Independent Mode (Not common application)Work in a separate user interface, developing the analysis model from imported geometry or geometry created by using Mechanicas geometry-creation facilities.Note: This st

13、andard work document contains the application of 2 modules, Structure and Thermal, but limit to base on Native Mode.Above all as shown in the following figures. 1.2 References / Training Material for Mechanicaa) This document refer to the on-line training material about application of Creo Elements/

14、Pro Mechanica, see the following site: b) This document also refers to Help Center of Creo Elements/Pro Engineer 5.0.2. FEA PROCESS IN MECHANICA Create Constraints/LoadsDevelop ModelsSimplify ModelsAssign MaterialsModels IdealizationsCreate ConnectionsGenerate MeshesRun SolversDefine AnalysesRun Ana

15、lysesReview ResultsUpgrade ModelsOptimize ModelsStandard Design StudySensitivity Design StudyOptimization Design Study The common process includes structural and thermal see below figure.2.1 Develop Models2.1.1 Simplify ModelsIf a feature in the analysis models is not necessary for an analysis or de

16、sign study and has no anticipated effect on the results, omit it for the time being. Also, if possible, omit areas of your design that cannot be changed. After finish Mechanica optimization, add these items back into the design. This approach offers several advantages. a) Mechanica design studies ru

17、n more quickly for simpler parts. b) Omit unnecessary portions of the design from the design part, do not risk setting up relationships that may artificially restrict the changing of the design variables. c) Use analysis results from a partly-developed model to answer questions about how to build th

18、e remainder of the model.Common solution methods as below,a) Modeling thin features with beams and shells rather than as solids. This simplifies the model from the solvers perspective, greatly reducing model size, disk usage, RAM requirements, and analysis times.b) Suppressing features that are not

19、germane to the analysis, such as very small chamfer, fillet radius, holes and grooves etc.c) Using cut features to reduce the analysis model to its symmetric section for models that exhibit both geometric symmetry and modeling symmetry (But need create symmetric loads and constraints).d) Using cut f

20、eatures to remove portions of the analysis model that are not pertinent to the analysis, such as thread.e) Aligning edges and surfaces that are nearly aligned in the part or assembly.2.1.2 Assign MaterialsMechanica allow to define materials for analysis models in Structure or Thermal. If work with t

21、he model in both Structure and Thermal, Mechanica assigns the same material for both products. For example, if you assign the material for your Structure model as Aluminum 2014, Mechanica assumes Aluminum 2014 for Thermal as well. However, several of the material properties available in Structure ar

22、e different from those available in Thermal. For instance, Structure enables to define such properties as Youngs modulus and Poissons ratio, whereas Thermal enables to define conductivity and specific heat.For Structure analysis, when apply new material, should note “Failure Criteria” as below,a) Is

23、otropic: Modified Mohr, Tresca and von Mises. Von Mises is common used for plastic yielding.b) Transversely Isotropic: Tsai-Wu, Maximum Stress, and Maximum Strain.2.1.3 Models Idealizationsa) Create ShellIf the thickness is much smaller than the length and width of the analysis model, usually the le

24、ngth and width = 10* thickness, using “shell” to simplify the model. Here need input the thickness.b) Create Shell Pair Mechanica allows define shell pairs for both part and assembly models. Mechanica uses the shell pairs that user define to form a network of compressed surfaces called the midsurfac

25、e. Mechanica places elements only on the midsurface, using the thickness associated with each portion of the shell to determine the depth of the elements. So, here dont need to input the thickness value.c) Create BeamsIf the axial length is much larger than other dimensions, using “beam” to simplify

26、 the 3d model.d) Create Spring (Structure Module only)A Spring Idealization adds translational or torsional resistance between two points in a Structure model. e) Create Masses (Structure Module only. Not common application)A masses idealization use to represent a concentrated mass without a specifi

27、ed shape. The mass of an object determines how that object resists translation and rotation. If Structure model behaves with mass at a given location, but not in the geometry or other features of that mass, use mass idealization. For example, you can represent the mass of an engine on a car frame wi

28、thout specifying the engine geometry. 2.1.4 Create Constraints/LoadsNote: Constraints and loads should defined the real-world environment the models encounter.a) Structure AnalysisAny unconstrained portion of the model is free to move in all directions, so here need apply constraints and loads.Creat

29、e the following types of Structure loads to a portion of Structure models. Force and moment loads Bearing loads (not available in FEM mode) Centrifugal loads Gravity loads Pressure loads Temperature loadsCreate the following types of Structure constraints to a portion of Structure model. Displacemen

30、t constraint Planar, Pin, and Ball Constraints Symmetry constraint (Not available in FEM mode)Note: If have simplified the models by modeling symmetry, this constraint must be used.b) Thermal Analysis, Create heat loads to a portion of Thermal models. Heat load is available only in Thermal modelsCre

31、ate the following types of Thermal Boundary Conditions to a portion of Thermal model. Prescribed Temperatures Convection Conditions Symmetry Constraint (Native mode only)Note: If have simplified the models by modeling symmetry, this constraint must be used.2.1.5 Create ConnectionsA connection is the

32、 mating area between two or more parts or assembly components.a) Structure AnalysisAny unconstrained portion of the model is free to move in all directions, so here need apply constraints and loads.Create the following types of Structure connections to a portion of Structure models. Interfaces Welds

33、 Fasteners (Native mode only, for FEM mode. It is Gaps) Rigid Links Weighted Links (Not common application)After create connections in the model, it enables to preview the different types of connections using the Mesh Review Geometry command in FEM mode or the AutoGEM Review Geometry command in nati

34、ve mode.b) Thermal Analysis, Create the following types of Structure connections to a portion of Thermal models. Interfaces WeldsAfter create connections in the model, it enables to preview the different types of connections using the Mesh Review Geometry command in FEM mode or the AutoGEM Review Ge

35、ometry command in native mode.2.1.6 Generate MeshesAutoGEM is the Mechanica Automatic Geometric Element Mesher.The AutoGEM menu includes the following commands:a) ControlCreate AutoGEM mesh controls for your model. b) CreateCreate an AutoGEM mesh for your model. c) SettingsReview and alter AutoGEMs

36、basic settings and limits. d) Review GeometryIt allows to view the different types of connections and simulation geometry for analysis models before meshing. e) Geometry ToleranceRefine geometry tolerance settings for analysis models to improve the geometry prior to meshing. f) Mesh treatment option

37、sThere are three model treatment optionsSolid, Midsurface, and Solid / Midsurface. These options enable to specify whether Mechanica will treat analysis models as a solid, midsurface shell, or a mixture of both during meshing and analysis.2.2 Run Solvers2.2.1 Define AnalysesUse Analyses and Design S

38、tudies dialog box to create the following types of analyses in Native Mode.Note: This section do not involve FEM mode. a) Structure Analysis Static Large Deformation Static Contact Buckling (Not common application) Modal (Not common application) Fatigue (Not common application) Prestress (Not common

39、 application) Prestress Static Prestress Modal Dynamic (Not common application) Dynamic Time Response Dynamic Frequency Response Dynamic Random Response Dynamic Shock ResponseNote: Fatigue analysis requires a separate software license. If do not have a license, use Mechanica in demo mode.b) Thermal

40、Analysis, Steady-State Thermal Transient Thermal2.2.2 Run AnalysesTo run an analysis or design study, select it from the list in the dialog box and use the following options to set up and manage the run. a) Run menu Start Stop Batch Settingsb) Info menu Status Open the Run Status window that enables

41、 you to view the status of a run. Check ModelPerform error checks in analysis models to determine whether there are problems such as missing properties, problems with constraints or boundary conditions, invalid analysis definitions, and so forth that would prevent an analysis or study run from start

42、ing. Optimize HistoryReview the shape change history of analysis models for an optimization study and to overwrite the Creo Elements/Pro part with the optimized shape developed in Creo Elements/Pro Mechanica. 2.2.3 Review ResultsHere is a step-by-step overview of the suggested workflow:a) Viewing re

43、sultsDefine result windows, display and hide the result, and control how appear on-screen and in the reports. b) Evaluating resultsStudy the defined result windows, probe specific areas of analysis models, and compare the findings for one model, design study, result quantity, or set of conditions wi

44、th the findings for another. c) Saving result windowsSave the set of created result windows to review or re-use them later. d) Generating reports2.3 Optimize ModelsAfter performed a baseline analysis, the next step is to begin improving models design. The most common method of defining design variab

45、les is to use driving dimensions from the model geometry. Mechanica has 3 tools as following.Note: if need to remove or add some new parts especially in assembly models, a brand new analysis should perform.2.4.1 Standard Design StudyIn a standard design study, Mechanica calculates results for an ana

46、lysis or analyses. Specify different design variable settings for the analysis. Be able to select New Standard Design Study in the Analyses and Design Studies dialog box. 2.4.2 Sensitivity Design Studya) Global Sensitivity Design StudyIn a global sensitivity study, Mechanica calculates values for al

47、l measures that are valid for the analyses included in the study. The software specifically calculates the changes in the models measures if varied a design variable over a specified range. Mechanica does this by calculating measure values at regular intervals within a variable range. User can vary

48、more than one variable simultaneously and also examine the results for a global sensitivity study as a graph of a measure for a selected design variable.Note: Mechanica does not calculate dynamic step measures when using dynamic time, frequency, or random response analyses in a global sensitivity st

49、udy.b) Local Sensitivity Design StudyA local sensitivity study calculates the effect of slight changes in one or more design variables on the models measures. Mechanica calculates the slope of the sensitivity curve between two sample points. The result is a graph of the linear approximation of a mea

50、sure over a variables range. The sensitivity slopes are also reported in the run summary file. Mechanica computes local sensitivity by first performing a base analysis followed by a perturbation analysis for each design variable. A base analysis is the same as a standard analysis. In a perturbation

51、analysis, Mechanica changes the design variable by an incremental amount and then performs a new analysis. Mechanica uses the results of the perturbation analysis and base analysis to compute a slope. This value is the same as the slope of the global sensitivity curve at a given value of the variables. By compa