#SEU12 - 507 an introduction to fea via solid edge and femap - mark sherman

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This session will cover the basics of Finite Element Analysis with an emphasis on how to use FEA tools to effectively influence the design process and increase product quality and performance. Proper application of the tools provided in both Solid Edge and FEMAP will be discussed. This session should be useful to designers and engineers who want to more fully understand the structural, dynamic, and thermal performance of individual parts and complex systems.

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#SEU12 - 507 an introduction to fea via solid edge and femap - mark sherman

  1. 1. An Introduction to FEA via SolidEdge and FEMAPMark ShermanSiemens PLM SoftwareFEMAP #SEU12
  2. 2. IntroductionMark Shermansherman.mark@siemens.com610-458-6502BS Aerospace and Ocean Engineering –Virginia TechBoeing HelicopterGE Astro SpaceJoined FEMAP (Enterprise SoftwareProducts, Inc. – 1992 ) © Siemens AG 2012. All Rights Reserved.Page 2 Siemens PLM Software
  3. 3. FEMAP History• Founded by George Rudy, 1985• Mission – PC-based dedicated Pre- and Post-Processor for Engineering Finite Element Analysis• Originally a Pre-Processor Only for MSC/PAL and MSC/NASTRAN on 64k RAM IBM PCDOS to Windows Transition 1990- 1992• Rapid Growth from 1992 on• Significant strength in Aerospace accounts• Laboratory Module of the ISS (Boeing)• OEM Partnership – MSC/Nastran for Windows• Tens of thousands of licenses worldwide © Siemens AG 2012. All Rights Reserved. Page 3 Siemens PLM Software
  4. 4. FEMAP Continuous development with the same core team! Since 1985 there have been more than 30 releases of FEMAP with only one major architecture change (DOS to Windows) FEMAP Development Team is all engineers turned programmers – FEA By Engineers for Engineers Product development has been driven by FEA Analyst input © Siemens AG 2012. All Rights Reserved.Page 4 Siemens PLM Software
  5. 5. Why use Finite Element AnalysisUnderstand the behavior of engineered parts and assemblies Structural Behavior  Static – Stress, Deflection, Load Distribution - Linear  Dynamic  Natural Frequency – Normal Modes  Frequency Response (Sinusoidal) – Accel., Disp., Stresses  Transient Response (General Time-Varying Loads) Accel., Disp. Stresses  Non-Linear  Contact  Geometric Nonlinearity  Material Nonlinearity• Thermal  Steady-State  Transient © Siemens AG 2012. All Rights Reserved.Page 5 Siemens PLM Software
  6. 6. Why use Finite Element Analysis Quality Material Cost Weight Reduce requirement for physical testing Maximize these benefits - Important to integrate FEA into the Design Process © Siemens AG 2012. All Rights Reserved.Page 6 Siemens PLM Software
  7. 7. Customer Success Stories - DuracastCustomer was driven to seek a CAE solution Rising cost of materials – need to optimize their current designs to save material use and cost (use petroleum based products) To reduce the level of physical prototyping to save time and cost Maintain integrity of product – advanced solutions required including nonlinear analysis A single seat of FEMAP with NX/Nastran saves this company hundreds of thousands of dollars per year in material cost © Siemens AG 2012. All Rights Reserved.Page 7 Siemens PLM Software
  8. 8. Space Exploration TechnologiesLaunch Vehicle DeveloperChallenge: Develop rockets thatreduce the cost of space access by afactor of 10Approach: Create virtual mockups ofentire rockets using Femap and NXsoftwareResults: More effective collaboration "On the analysis front Femap andbetween design groups, and a 50% NX Nastran were the clear winners, not only due to wideproductivity improvement helped industry acceptance but also fromsuccessfully launch two Falcon 1 an ease of use and support standpoint.”rockets Chris Thompson, vice president of Development Operations © Siemens AG 2012. All Rights Reserved.Page 8 Siemens PLM Software
  9. 9. A Brief History of FEA and FEM The concept of a “Finite Element” was introduced by Prof. R.W. Clough of UC Berkeley in 1960 at an ASCE Conference. NASTRAN (NASA STRuctural ANalysis) was developed for NASA by a consortium of several companies for the analysis of the Saturn V rocket.  Siemens PLM Software acquired MSC.Nastran source code in 2003 and has greatly improved the performance and capabilities of NX Nastran through the latest release of NX Nastran 8.1  Finite Element Modelers(Pre/Post Processors), the tools used to generate Finite Element meshes and view results, were first commercialized in the 1970s.  Siemens PLM Software began the first commercial offering of FEM software with the introduction of SDRC SuperTab in the 1970’s.  Siemens continues to support the analysis community with Femap and NX CAE pre/post-processors. © Siemens AG 2012. All Rights Reserved. Page 9 Siemens PLM Software
  10. 10. The SolutionConsider a single degree of freedom system – a simple spring: Apply the following conditions to generate a system of simultaneous equations where displacements are the unknowns: Equilibrium of forces and moments  ?  Strain- displacement relations Ku=P (static analysis) Stress-strain relations K: spring stiffness P: applied load u: displacement © Siemens AG 2012. All Rights Reserved. Page 10 Siemens PLM Software
  11. 11. Solution for Multiple DOFsAny real structure can be modeled as a collection of elements connected at nodesWith many elements and nodal dof’s, a matrix approach to the solution is adopted Element stiffness matrix ka kb k11 k12 1 2 3 ka = k21 k22  All element matrices are assembled into a global stiffness matrix ka11 ka12 Kgg = ka21 ka22 + kb22 kb23 kb32 kb33 © Siemens AG 2012. All Rights Reserved. Page 11 Siemens PLM Software
  12. 12. Modeling of Real Structures• The behavior of the real structure is obtained by considering the collective behavior of the discrete elements.• The user is responsible for the subdivision or discretization of real-world structures.• Element choice has significant influence on the behavior• A graphic preprocessor such as FEMAP/SE Simulation is the key tool for generating a model that accurately simulates real world structures • Contributions from all other elements ka -ka -ka ka + kb -kb Kgg = -kb kb nxn © Siemens AG 2012. All Rights Reserved. Page 12 Siemens PLM Software
  13. 13. Why use Finite Element AnalysisUnderstand the behavior of engineered parts and assemblies Structural Behavior  Static – Stress, Deflection, Load Distribution - Linear  Dynamic  Natural Frequency – Normal Modes  Frequency Response (Sinusoidal)  Transient Response (General Time-Varying Loads)  Non-Linear  Contact  Geometric Nonlinearity  Material Nonlinearity• Thermal  Steady-State  Transient © Siemens AG 2012. All Rights Reserved.Page 13 Siemens PLM Software
  14. 14. Linear Static Analysis 90%+ of all FEA projects 100% Linear – if you double the loads, you get double the response Material stays in the elastic range – return to original shape Small Deformation Maximum Displacement much smaller than characteristic dimensions of the part being studied, i.e. displacement much less than the thickness of the part Loads are applied slow and gradually, i.e. not Dynamic or Shock Loading © Siemens AG 2012. All Rights Reserved.Page 14 Siemens PLM Software
  15. 15. FEA Building Blocks Numerous Element Types This makes it possible to accurately model the real-world performance of your engineered structure Element selection helps balance model size vs.  Solution accuracy  Hardware resources  Solution time  Results interpretation time Another consideration for solids is time to mesh the model if a hex mesh is desired © Siemens AG 2012. All Rights Reserved. Page 15 Siemens PLM Software
  16. 16. Element BasicsChoose elements to represent the real structure behavior Rod Element: Axial and Torsion Stiffness only (pin connected truss) Beam : Classic Euler-Bernoulli Beam depending on property options used Shear effects, shear center offset, etc can be included, user must understand the defaults and options to ensure proper behavior is included Plate/Shell : Started with Kirchhoff and Mindlin theories but now many different “tweaks” and modifications included to improve accuracy. When elements of different types connect, user must be aware of potential compatibility problems and use special modeling techniques as needed. Examples: beams connecting normal to plates, plates connecting to solids © Siemens AG 2012. All Rights Reserved.Page 16 Siemens PLM Software
  17. 17. Finite Elements – 0D Scalar Elements Springs Node to node axial or torsional Dampers Node to node axial or torsional Mass Point masses can be used to represent additional mass and inertia in the structure that is non-structural or where modeling detail is not required Rigid Elements Can be used to represent rigid connections within the model © Siemens AG 2012. All Rights Reserved. 17 Page 17 Siemens PLM Software
  18. 18. Finite Elements – 1D Line Elements Rod Uniaxial tension compression and torsion – no bending or shear loads Used to model pin-ended truss structures Bar/Beam A regular beam that carries axial, torsion, bending and shear loads Very versatile – offsets and tapers can be included © Siemens AG 2012. All Rights Reserved. 18 Page 18 Siemens PLM Software
  19. 19. Finite Elements – 2D Plate and Shell Elements Used to represent “thin” structures like sheet metal structures. Additional features for shear-only, membrane-only, composite laminate etc. Quad4 / Tria3 Isoparametric 3/4 noded triangular/quadrilateral Quad8 / Tria6 Higher order isoparametric 6/8 noded triangular/quadrilateral © Siemens AG 2012. All Rights Reserved. 19 Page 19 Siemens PLM Software
  20. 20. Finite Elements – 3D Solid Elements Used to fill and model solid volumes Hexa Regular hexahedral elements Penta Pentrahedral used to mesh transitions Tetra Tetrahedral elements can be generated fully automatically on solids © Siemens AG 2012. All Rights Reserved. 20 Page 20 Siemens PLM Software
  21. 21. Linear Static Analysis What can you expect to learn from a linear static Finite Element Analysis Displacements Load Paths Stress* © Siemens AG 2012. All Rights Reserved.Page 21 Siemens PLM Software
  22. 22. Linear Static Analysis – Modeling Guidelines Use the Displacements Load Paths Stress* © Siemens AG 2012. All Rights Reserved.Page 22 Siemens PLM Software
  23. 23. Important GuidelinesLinear Analysis is small displacement, small angle theory Must use nonlinear analysis if the displacement changes the stiffness or loads Pressure loads on flat surfaces, have no membrane component unless nonlinear large displacement solution performed.(load carried by bending stiffness only) Linear contact is a misnomer, contact condition is iterative solution, but no other nonlinear effects are considered.Mesh density required is a function of the desired answers Must have enough nodes so model can deform smoothly like the real structure. In general, accurate stresses require more elements than accurate displacements. Goal is for a small stress gradient across any individual elementNormal modes should always be run before any dynamic solution Confirm model behavior, stiffness and mass properties are correct © Siemens AG 2012. All Rights Reserved.Page 23 Siemens PLM Software
  24. 24. Important GuidelinesFinite Element Analysis is an Approximate Solution to a ComplicatedProblem :Therefore, Sound Engineering Judgment is RequiredOur Answers are only as good as the assumptions we makeCommon sources for analysis uncertainty: Numerical round off (usually small) FEM : mesh density, element formulation, element connections Boundary conditions Loads and environments seen by the structure © Siemens AG 2012. All Rights Reserved.Page 24 Siemens PLM Software
  25. 25. Linear Statics - StressesTo accurately recover stresses in shell and solid elements, the mesh mustbe very dense in areas of high stress gradients Stress Changing TooFast Across One Element © Siemens AG 2012. All Rights Reserved.Page 25 Siemens PLM Software
  26. 26. Stresses from the Web © Siemens AG 2012. All Rights Reserved.Page 26 Siemens PLM Software
  27. 27. Linear Statics - StressesTo accurately recover stresses in shell and solid elements, the mesh mustbe very dense in areas of high stress gradients Stress Changing Less Across an Element – More Accurate © Siemens AG 2012. All Rights Reserved.Page 27 Siemens PLM Software
  28. 28. Linear Statics - StressesKeeping Model Size “Reasonable”Increase the Mesh Density where you need it, decrease it where you don’t © Siemens AG 2012. All Rights Reserved.Page 28 Siemens PLM Software
  29. 29. Linear Statics - Stresses © Siemens AG 2012. All Rights Reserved.Page 29 Siemens PLM Software
  30. 30. Guidelines for Good Stress Interpretation -Singularities © Siemens AG 2012. All Rights Reserved.Page 30 Siemens PLM Software
  31. 31. Guidelines for Linear Static Analysis - Stresses• Remember the limitations of “Linear” analysis• Increase Mesh Density in High Stress Regions• Ignore Stress Answers at Singularities • Zero Radius Fillets • Inside Corners • Loaded and Constrained Nodes © Siemens AG 2012. All Rights Reserved.Page 31 Siemens PLM Software
  32. 32. When you need FEMAPMonaco CoachSolid Mesh ImpracticalShells alone, not enoughBeam – Lumped Mass requiredTransient Dynamic Analysis arequirement Courtesy of Predictive Engineering © Siemens AG 2012. All Rights Reserved.Page 32 Siemens PLM Software
  33. 33. Real FEA - ExamplesBechtel River ProjectSolid Mesh ImpracticalShells alone, not enoughBeam – Rigid, and Lumped Mass requiredTransient Dynamic Analysis a requirementPost-processing Data Processing Required © Siemens AG 2012. All Rights Reserved. Page 33 Siemens PLM Software
  34. 34. Real FEA - ExamplesBoeing - International Space StationLaboratory Module © Siemens AG 2012. All Rights Reserved. Page 34 Siemens PLM Software
  35. 35. Real FEA - Examples Why can’t we just tetra-mesh this? Just this little section is 565,405 Nodes – 275,558 Elements and there’s only one element through the thickness Full Model would be billions © Siemens AG 2012. All Rights Reserved.Page 35 Siemens PLM Software
  36. 36. SE Simulation  FEMAP Model Size Limitations – when one has to idealize a structure beyond the Solid, Shell and Beam Elements available in SE Simulation Modeling Limitations • Composite Laminates • Nonlinear Geometry - Large Displacements • Nonlinear Materials - outside the elastic range, or non-elastic materials (rubber). • Time or Temperature Dependent Loading • Specialty Elements like CBUSH where you can have displacement dependent stiffness and damping • CWELD - CFAST © Siemens AG 2012. All Rights Reserved.Page 36 Siemens PLM Software
  37. 37. SE Simulation Continues to Dive Deeper into FEAFunctionalityWithout Pre-Load/Contact – First Mode 1.472608 Hz © Siemens AG 2012. All Rights Reserved. Page 37 Siemens PLM Software
  38. 38. SE Simulation Continues to Dive Deeper into FEAFunctionalityWith Pre-Load/Contact – First Mode 7.586033 Hz © Siemens AG 2012. All Rights Reserved. Page 38 Siemens PLM Software
  39. 39. SE Simulation Continues to Dive Deeper into FEAFunctionalityFirst Mode 415% Higher!!! © Siemens AG 2012. All Rights Reserved. Page 39 Siemens PLM Software
  40. 40. Why use Finite Element AnalysisUnderstand the behavior of engineered parts and assemblies Structural Behavior  Static – Stress, Deflection, Load Distribution – Linear  Linear Contact  Dynamic  Natural Frequency – Normal Modes  Frequency Response (Sinusoidal)  Transient Response (General Time-Varying Loads)  Non-Linear  Contact  Geometric Nonlinearity  Material Nonlinearity• Thermal  Steady-State  Transient © Siemens AG 2012. All Rights Reserved.Page 40 Siemens PLM Software
  41. 41. Advanced Dynamics Examples Sample Model Tubular Structure Supports Offset Payload/Mass Subject to Lateral +/- X Forces © Siemens AG 2012. All Rights Reserved.Page 41 Siemens PLM Software
  42. 42. Advanced Dynamics ExamplesIdealized Model – beam elements for tubes and lugs, shell mesh at base © Siemens AG 2012. All Rights Reserved.Page 42 Siemens PLM Software
  43. 43. Advanced Dynamics ExamplesAlways do a modal run first and make sure everything makes senseEvaluate basic modes/natural frequencies © Siemens AG 2012. All Rights Reserved.Page 43 Siemens PLM Software
  44. 44. Advanced Dynamics ExamplesFrequency Response – Check Response at the end of the support arm tofrequencies between 0 and 30 Hz. Request responses between 0.0 and 30.0, every 0.2 Hz © Siemens AG 2012. All Rights Reserved.Page 44 Siemens PLM Software
  45. 45. Advanced Dynamics ExampleFrequency Response – Limit Output, in this sweep, we are asking for 150sets of Output, recover responses where they matter most, in this case, outat the end of the arm. © Siemens AG 2012. All Rights Reserved.Page 45 Siemens PLM Software
  46. 46. Advanced Dynamics ExampleUse Stick and Plate model for preliminary design/sanity checkUpdate design as necessaryCreate detailed Shell or Solid model of final design, run FrequencyResponse at actual operating frequencies for final validation © Siemens AG 2012. All Rights Reserved.Page 46 Siemens PLM Software
  47. 47. Advanced Dynamics Example Stick and Plate Model – 2104 Nodes All Shell Model – 18,115 Nodes © Siemens AG 2012. All Rights Reserved.Page 47 Siemens PLM Software
  48. 48. Frequency Response Results © Siemens AG 2012. All Rights Reserved.Page 48 Siemens PLM Software
  49. 49. Overview - DiscussionTo get good results, accurately model your structure• Material Properties, linear, non-linear• Linear or nonlinear overall behavior• Boundary Conditions• Loads• Structure – Does your mesh accurately reflect the structure• Most Critical Stress condition may not be covered by linear static analysis © Siemens AG 2012. All Rights Reserved. Page 49 Siemens PLM Software
  50. 50. Contact InformationMark A. Shermansherman.mark@siemens.com610-458-6502 © Siemens AG 2012. All Rights Reserved.Page 50 Siemens PLM Software
  51. 51. Thank You!Questions? #SEU12

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