FEA Using Ansys

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FEA Using Ansys

  1. 1. By ANSYS INC ANSYS
  2. 2. • Engineering simulation software founded by software engineer John Swanson. • Developed a range of computer-aided engineering (CAE) Products, it is perhaps best known for its ANSYS mechanical and ANSYS multiphysics products. • Ansys mechanical and ANSYS multiphysics software are non exportable analysis tools. • These are general purpose finite element modeling packages for numerically solving mechanical problems, including static/dynamic structural analysis both linear/non linear), heat transfer and fluid problems contd... ABOUT ANSYS
  3. 3. About Analysis Process of analyzing a structure to the externally applied loads( Pressure, Force, Temperature)
  4. 4. Basic Terminologies-Structural analysis • Stress • Strain • Poisson ratio • Hook's law • Young's modulus • Bending moment • Shear force • Stress strain curve for various materials • Linear • Nonlinear • Isotropic vs. anisotropic vs. orthotropic
  5. 5. Stress When some external system of forces or loads act on a body, the internal forces (equal and opposite) are set up at various sections of the body, which resist the external forces. This internal force per unit area at any section of the body is known as unit stress or simply stress Stress, =σ P/A
  6. 6. Strain When a system of forces or loads act on a body, it undergoes some deformation. This deformation per unit length is known as unit strain or simply a strain. It is denoted by a Greek letter epsilon (ε). Strain, ε = δl / l δl = ε.l
  7. 7. Displacement A change in the configuration of a continuum body results in a Displacement. The displacement of a body has two components: a rigid-body displacement and a deformation. A rigid-body displacement consists of a simultaneous translation and rotation of the body without changing its shape or size. Deformation implies the change in shape and/or size of the body from an initial or undeformed configuration to a current or deformed configuration
  8. 8. Shear Stress When a body is subjected to two equal and opposite forces acting tangentially across the resisting section, as a result of which the body tends to shear off the section, then the stress induced is called shear stress. Shear stress, τ = Tangential force Resisting area
  9. 9. Shear Strain When a body is subjected to two equal and opposite forces acting tangentially across the resisting section, as a result of which the body tends to shear off the section corresponding strain is known as shear strain.
  10. 10. Shear Force In static equilibrium, the internal force has a magnitude equal to opposite in direction and parallel to the cross-section. is called the shear force. F-Shear Force
  11. 11. BENDING MOMENT • The bending moment at the cross section of a beam may be defined as the algebric sum of the moment of the forces to the right or left of the section • The bending moment at the cross section of a beam may be defined as the algebric sum of the moment of the forces to the right or left of the section
  12. 12. DEGRESS OF FREEDOM • Minimum no of independent co ordinates required to determine completely the positions of all parts of a system at a given instant time • Minimum no of independent co ordinates required to determine completely the positions of all parts of a system at a given instant time
  13. 13. Young’s modulus And Poisson’s Ratio For Some Materials Materials Young’s Modulus Poisson’s Ratio Steel 2.1e5 0.3 Cast Iron 1.20e5 0.28 Wrought Iron 1.90e5 0.3 Aluminium 0.70e5 0.35 Aluminium Alloy 0.75e5 0.33 Brass 1.10e5 0.34 Bronze 1.20e5 0.34 Copper 1.20e5 0.34 Copper Alloy 1.25e5 0.33 Magnesium 0.45e5 0.35 Titanium 1.10e5 0.33 Glass 0.60e5 0.22 Rubber 50 0.49 Concrete 0.25e5 0.15
  14. 14. Truss element • The truss elements are the part of a truss structure linked together by point joints, which transmit only axial force to the element • The truss elements are the part of a truss structure linked together by point joints, which transmit only axial force to the element
  15. 15. GLOBAL & LOCAL AXES GLOBAL : Global axes are defined for the entire system. They are same in direction for all the elements even though the elements are differently oriented LOCAL : Local axes are established in an element. Since it is the element level, they change with the change in orientation of the element. The direction differs from element to element
  16. 16. Need for Analysis •To reduce product development cycle time •To reduce the cost of product •Idle time reduction •Better design and Alternate materials •To reduce material wastage
  17. 17. Types of Methods • Mathematical approach • Physical model • Numerical method
  18. 18. Introduction to FEM & FEA • FEM-Finite element method • FEA –Finite element analysis
  19. 19. FEM • Finite element method of structural analysis was created by academic and industrial researches during 1959’s and 1960’s • Theoretical approach. • Examples Euler's rule, LaGrange method, Newton raphson method, Fourier series
  20. 20. Nature of FEM • Force method (Forces unknown) Strain energy method Consistent deformation method Matrix flexibility method Clayperons theorem of 3 moments • Displacement method (Displacements unknown) Kanis method Slope deflection method Matrix stiffness method Moment distribution method FEM
  21. 21. FEA FEA- simulate loading conditions on design & determine design response to these conditions The design is modeled using discrete elements called elements The sum of response of all elements in the model gives the response of design
  22. 22. Problem types in FEA • Boundary value problem-static and steady state analysis • Initial value problem-fluid flow • Eigen value problem-Modal analysis, vibration and natural frequency • Boundary initial value problem-forced vibration, transient and dynamic analysis
  23. 23. Linear vs. Non linear • What is linear analysis? • What is non linear analysis? • Types of non linearity • When should we do a non linear analysis?
  24. 24. 24/50 16.1.1 What is a Nonlinear Structure Displacements Forces Displacements Forces
  25. 25. 25/50 16.1.2 Causes of Nonlinearities • Geometric Nonlinearity • Material Nonlinearity • Status Nonlinearity
  26. 26. 26/50 Geometric Nonlinearity Force Displacement Moment arm Forces Displacements
  27. 27. 27/50 Material Nonlinearity Strain StrainStress Stress Mild Steel Rubber
  28. 28. 28/50 Status Nonlinearity The contact area depends on the applied force Force
  29. 29. 29/50 16.1.3 Consequences of Nonlinearities • Principle of superposition no longer applicable • Solution may depend on loading history
  30. 30. 30/50 16.2.1 Equations for a Nonlinear Structure ( ) FDDK =× D K(D) F(D)
  31. 31. 31/50 16.2.2 Incremental Method ( ) FDDK =× F Error Calculated Response Actual Response 1 2 3 D
  32. 32. 32/50 16.2.3 Newton-Raphson Method D = D4 F = F4 Actual response 1 2 3 4 D1 D2 D3 F1 F2 F3
  33. 33. 33/50 16.2.4 Convergence Criteria in ANSYS D = D4 F = F4 Actual respons e 1 2 3 4 D1 D2 D3 F1 F2 F3 max max 005.0 05.0 FF DD ≤∆ ≤∆
  34. 34. 34/50 16.3.1 Radius of Convergence D F Actual response Do Do Radius of convergence
  35. 35. 35/50 16.3.2 Consistent Stiffness Matrix • Tangent stiffness • Additional stiffness due to deformation (geometric change) • Additional stiffness due to stress stiffening • Additional stiffness due to change of loading direction. aσuinc KKKKK +++=
  36. 36. 36/50 16.3.3 Load Steps, Substeps, and Equilibrium Iterations Substeps Time Load Load step 2 Load step 1 D = D4 F = F4 Actual respons e 1 2 3 4 D1 D2 D3 F1 F2 F3
  37. 37. 37/50 16.3.4 Concepts of Time • The ends of load steps or substeps can be identified by time. • For dynamic problem, time is used as a real-world clock. • For static problem, time is used as a counter.
  38. 38. 38/50 16.3.5 Automatic Time Stepping • For nonlinear problem, the user-input ∆t is used as initial incremental time. • ANSYS adjusts ∆t automatically according to the convergence behavior of the solution.
  39. 39. 39/50 16.3.6 Text Output Information 1 2 3 45
  40. 40. 40/50 16.3.7 Graphical Output Information
  41. 41. 41/50 16.3.8 Automatic Nonlinear Solution Control • SOLCONTROL command can be used to activate automatic nonlinear solution control algorithm. • The default is ON.
  42. 42. 42/50 Basic Solution Options 01 02 03 04 05 06 07 08 09 10 SOLCONTROL, Key ANTYPE, Antype NLGEOM, Key TIME, TIME NSUBST, NSBSTP, NSBMX, NSBMN, Carry DELTIM, DTIME, DTMIN, DTMAX, Carry AUTOTS, Key KBC, KEY OUTRES, Item, FREQ, Cname MONITOR, VAR, Node, Lab
  43. 43. 43/50 16.4.1 Analysis Type (ANTYPE) • For nonlinear analysis, only two analysis types applicable: STATIC and TRANS.
  44. 44. 44/50 16.4.2 Nonlinear Geometry (NLGEOM) • NLGEOM turns ON/OFF the effects of geometric nonlinearity.
  45. 45. 45/50 16.4.3 Load Step Time (TIME) • TIME specifies the time at the end of the following load step.
  46. 46. 46/50 16.4.4 Number of Substeps (NSUBST, DELTIM) • NSUBST specifies number of substeps for the following load step. • DELTIM specifies time for each substep for the following load step. • The two commands are equivalent, i.e., NSUBSTDELTIMTIME ×= NSUBST, NSBSTP, NSBMX, NSBMN, Carry DELTIM, DTIME, DTMIN, DTMAX, Carry
  47. 47. 47/50 16.4.5 Automatic Time Stepping (AUTOTS) • AUTOTS turns ON/OFF the functions of auto time stepping.
  48. 48. 48/50 16.4.6 Ramped/Stepped Loading (KBC) 0 Time Load Stepped load Substeps
  49. 49. 49/50 16.4.7 Output Controls (OUTRES) • OUTRES controls the amount of data stored in Jobname.RST. OUTRES, Item, FREQ, Cname
  50. 50. 50/50 16.4.8 Monitor File (MONTOR)
  51. 51. 51/50 Advanced Solution Options 01 02 03 04 05 06 07 08 09 10 11 12 13 EQSLV, Lab, TOLER, MULT SOLCONTROL, Key1, Key2 NEQIT, NEQIT CNVTOL, Lab, VALUE, TOLER, NORM, MINREF NROPT, Option,, Adptky LNSRCH, Key PRED, Sskey, --, Lskey SSTIF, Key PSTRES, Key CUTCONTROL, Lab, VALUE, Option TIMINT, Key, Lab TINTP, GAMMA, ... NCNV, KSTOP, DLIM, ITLIM, ETLIM, CPLIM
  52. 52. 52/50 16.5.1 Equation Solver (EQSLV) • EQSLV lets you choose the algorithm solving the equations.
  53. 53. 53/50 16.5.2 Time Step Prediction Based on Contact Status (SOLCONTROL) • The second key of SOLCONTROL command is to ask ANSYS to adjust time steps according to contact status. SOLCONTROL, Key1, Key2
  54. 54. 54/50 16.5.3 Number of Equilibrium Iterations (NEQIT) • NEQIT specifies the number of iterations beyond which ANSYS would start another “attempt”.
  55. 55. 55/50 16.5.4 Convergence Criteria (CNVTOL) • CNVTOL overrides the default convergence criteria.
  56. 56. 56/50 16.5.5 Newton-Raphson Option (NROPT) (a) Full Method (b) Modified Method (c) Initial Method NROPT, Option,, Adptky
  57. 57. 57/50 16.5.6 Line Search (LNSRCH) • LNSRCH turns ON/OFF the “line search” algorithm in ANSYS.
  58. 58. 58/50 16.5.7 Predictor (PRED)
  59. 59. 59/50 16.5.8 Adaptive Descent (NROPT) NROPT, Option,, Adptky
  60. 60. 60/50 16.5.9 Stress Stiffening (SSTIF, PSTRES) • SSTIF/PSTRES turns ON/OFF the computation of stress stiffness (Kσ ) and storing on file.
  61. 61. 61/50 16.5.10 Cutback Control (CUTCONTROL) • CUTCONTROL specifies the conditions in which ANSYS would decrease time step during auto time stepping.
  62. 62. 62/50 16.5.11 Time Integration Effects (TIMINT, TINTP) • TIMINT turns ON/OFF transient effects. • The parameter GAMMA of TINTP command can be used to introduce a “numerical damping”. TIMINT, Key, Lab TINTP, GAMMA, ...
  63. 63. 63/50 16.5.12 Stop Control (NCNV) • NCNV specifies the stop (failure) conditions of the computation. NCNV, KSTOP, DLIM, ITLIM, ETLIM, CPLIM
  64. 64. 64/50 16.5.13 Terminating an Analysis
  65. 65. 65/50 16.5.14 Restarting an Analysis • An analysis terminated normally can be restarted.
  66. 66. 66/50 16.6 Exercise: Hyperelastic Planar Seal
  67. 67. ANSYS- TOPICS
  68. 68. Static analysis • Analysis of a structure for various loads under static condition i.e. component under rest when loads are applied Examples Holding devices-Clamp or fixture analysis Types Linear analysis Non linear analysis
  69. 69. Dynamic analysis • Analysis of a structure for various loads under Dynamic condition i.e. component is in motion when loads are applied or time varying loads Examples Suspension systems of a vehicle Types Linear analysis Non linear analysis
  70. 70. Structural analysis-Design consideration • Change design • Alternate material
  71. 71. Thermal analysis • To determine the temperature distribution occurring in the model Modes of heat transfer Conduction Convection Radiation
  72. 72. Basic terminologies-thermal analysis • Coeff of thermal expansion • Heat transfer coefficient • Thermal conductivity • Heat generation (Q) • Thermal flux
  73. 73. Structure Idealization • Process of discritization of a structure into element and nodes • Infinite no of D.O.F to Finite D.O.F Types of discritization Natural Artificial
  74. 74. FEM • Nodes • Elements Types of elements 1D-Line element(Min 2 nodes) 2D-Plane element (Area-Min 4 node) 3D-Solid element (Volume-min 8 nodes)
  75. 75. EXAMPLES FOR FINITE ELEMENT ONE DIMENSIONAL ELEMENTS : TRUSS ELEMENTS BAR, BEAM ELEMENTS TWO DIMENSIONAL ELEMENTS : TRIANGULAR ELEMENTS RECTANGULAR ELEMENTS THREE DIMENSIONAL ELEMENTS TETRAHEDRAL ELEMENTS HEXAHEDRAL ELEMENTS
  76. 76. Stages • Preprocessing • Solution • Postprocessing
  77. 77. Meshing-Importance & drawbacks • Why should we mesh • Element quality • Problems associated with meshing
  78. 78. Basic terminologies meshing • Aspect ratio • Skewing • Warp age Types of refinement H refinement P refinement
  79. 79. H and P versions H and P improve the accuracy of the fem In h versions the order of polynominal approximation for all elements kept constant and the no of elements increased. In P version the no of elements are maintained constant and the order of polynominal approximation of element is increased
  80. 80. FEM/ANSYS Section1: Structural By completing this section you will learn basic structural analysis using ANSYS.
  81. 81. Section 3: Fluid Mechanics By completing this section you will learn basic structural analysis using ANSYS.
  82. 82. Section 4: Vibration By completing this section you will learn basic vibration analysis using ANSYS.
  83. 83. List of other CAE softwares • Msc Nastran • Patran • Ls dyana • Addams • Comsol • Fluent • gambit • Star CD • Hyper form • Pam crash • Mat lab • ANSA

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