By ANSYS INC

ANSYS

• 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

About Analysis

Process of analyzing a structure to the externally applied loads( Pressure, Force, Temperature)

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

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

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

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

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

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.

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

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

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

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

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

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

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

Types of Methods

• Mathematical approach• Physical model• Numerical method

Introduction to FEM & FEA

• FEM-Finite element method• FEA –Finite element analysis

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

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

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

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

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?

24/50

16.1.1 What is a Nonlinear Structure

Displacements

Forces

Displacements

Forces

25/50

16.1.2 Causes of Nonlinearities

• Geometric Nonlinearity• Material Nonlinearity• Status Nonlinearity

26/50

Geometric Nonlinearity

Force

Displacement

Moment arm

Forces

Displacements

27/50

Material Nonlinearity

Strain Strain

Stress

Stress

Mild Steel Rubber

28/50

Status Nonlinearity

The contact area depends on the applied force

Force

29/50

16.1.3 Consequences of Nonlinearities

• Principle of superposition no longer applicable

• Solution may depend on loading history

30/50

16.2.1 Equations for a Nonlinear Structure

FDDK

D

K(D)F(D)

31/50

16.2.2 Incremental Method

FDDK

F

Error

Calculated Response

ActualResponse

1

2

3

D

32/50

16.2.3 Newton-Raphson Method

D = D4

F = F4

Actualresponse

1

23

4

D1 D2 D3

F1

F2

F3

33/50

16.2.4 Convergence Criteria in ANSYS

D = D4

F = F4

Actualrespons

e

1

23

4

D1 D2 D3

F1

F2

F3

max

max

005.0

05.0

FF

DD

34/50

16.3.1 Radius of Convergence

D

F

Actualresponse

Do Do

Radius of convergence

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

36/50

16.3.3 Load Steps, Substeps, and Equilibrium Iterations

Substeps

Time

Load

Load step 2

Load step 1

D = D4

F = F4

Actualrespons

e

1

23

4

D1 D2 D3

F1

F2

F3

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.

38/50

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.

39/50

16.3.6 Text Output Information

1

2

3

45

40/50

16.3.7 Graphical Output Information

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.

42/50

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

43/50

16.4.1 Analysis Type (ANTYPE)

• For nonlinear analysis, only two analysis types applicable: STATIC and TRANS.

44/50

16.4.2 Nonlinear Geometry (NLGEOM)

• NLGEOM turns ON/OFF the effects of geometric nonlinearity.

45/50

16.4.3 Load Step Time (TIME)

• TIME specifies the time at the end of the following load step.

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

47/50

16.4.5 Automatic Time Stepping (AUTOTS)

• AUTOTS turns ON/OFF the functions of auto time stepping.

48/50

16.4.6 Ramped/Stepped Loading (KBC)

0Time

Load

Stepped load

Substeps

49/50

16.4.7 Output Controls (OUTRES)

• OUTRES controls the amount of data stored in Jobname.RST.

OUTRES, Item, FREQ, Cname

50/50

16.4.8 Monitor File (MONTOR)

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

52/50

16.5.1 Equation Solver (EQSLV)

• EQSLV lets you choose the algorithm solving the equations.

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

54/50

16.5.3 Number of Equilibrium Iterations (NEQIT)

• NEQIT specifies the number of iterations beyond which ANSYS would start another “attempt”.

55/50

16.5.4 Convergence Criteria (CNVTOL)

• CNVTOL overrides the default convergence criteria.

56/50

16.5.5 Newton-Raphson Option (NROPT)

(a) Full Method (b) Modified Method (c) Initial Method

NROPT, Option,, Adptky

57/50

16.5.6 Line Search (LNSRCH)

• LNSRCH turns ON/OFF the “line search” algorithm in ANSYS.

58/50

16.5.7 Predictor (PRED)

59/50

16.5.8 Adaptive Descent (NROPT)

NROPT, Option,, Adptky

60/50

16.5.9 Stress Stiffening (SSTIF, PSTRES)

• SSTIF/PSTRES turns ON/OFF the computation of stress stiffness (K) and storing on file.

61/50

16.5.10 Cutback Control (CUTCONTROL)

• CUTCONTROL specifies the conditions in which ANSYS would decrease time step during auto time stepping.

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, ...

63/50

16.5.12 Stop Control (NCNV)

• NCNV specifies the stop (failure) conditions of the computation.

NCNV, KSTOP, DLIM, ITLIM, ETLIM, CPLIM

64/50

16.5.13 Terminating an Analysis

65/50

16.5.14 Restarting an Analysis

• An analysis terminated normally can be restarted.

66/50

16.6 Exercise: Hyperelastic Planar Seal

ANSYS- TOPICS

Static analysis• Analysis of a structure for various loads under static condition i.e.

component under rest when loads are applied

ExamplesHolding devices-Clamp or fixture analysis

Types Linear analysis Non linear analysis

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

ExamplesSuspension systems of a vehicle

Types Linear analysis Non linear analysis

Structural analysis-Design consideration

• Change design• Alternate material

Thermal analysis

• To determine the temperature distribution occurring in the model

Modes of heat transferConductionConvectionRadiation

Basic terminologies-thermal analysis

• Coeff of thermal expansion• Heat transfer coefficient• Thermal conductivity• Heat generation (Q)• Thermal flux

Structure Idealization

• Process of discritization of a structure into element and nodes

• Infinite no of D.O.F to Finite D.O.FTypes of discritization Natural Artificial

FEM

• Nodes• ElementsTypes of elements1D-Line element(Min 2 nodes)2D-Plane element (Area-Min 4 node)3D-Solid element (Volume-min 8 nodes)

EXAMPLES FOR FINITE ELEMENT

ONE DIMENSIONAL ELEMENTS :TRUSS ELEMENTSBAR, BEAM ELEMENTS

TWO DIMENSIONAL ELEMENTS :TRIANGULAR ELEMENTSRECTANGULAR ELEMENTS

THREE DIMENSIONAL ELEMENTSTETRAHEDRAL ELEMENTSHEXAHEDRAL ELEMENTS

Stages

• Preprocessing• Solution• Postprocessing

Meshing-Importance & drawbacks

• Why should we mesh• Element quality• Problems associated with meshing

Basic terminologies meshing

• Aspect ratio• Skewing• Warp ageTypes of refinementH refinementP refinement

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

FEM/ANSYS

Section1:StructuralBy completing this section you will learn basic structural analysis using ANSYS.

Section 3:Fluid MechanicsBy completing this section you will learn basic structural analysis using ANSYS.  

Section 4: VibrationBy completing this section you will learn basic vibration analysis using ANSYS.

List of other CAE softwares• Msc Nastran• Patran• Ls dyana• Addams• Comsol• Fluent• gambit• Star CD• Hyper form• Pam crash• Mat lab• ANSA