intro to ansys

8/13/2019 Intro to ANSYS

1/19

Getting Started with ANSYS


2/19

Performing a Typical ANSYSAnalysis

The ANSYS program has many finite element analysis capabilities,ranging from a simple, linear, static analysis to a complex, nonlinear,transient dynamic analysis. The analysis guide manuals in the ANSYSdocumentation set describe specific procedures for performing analyses

for different engineering disciplines.

A typical ANSYS analysis has three distinct steps:

Build the model.

Apply loads and obtain the solution.

Review the results.


3/19

Basic Modelling Steps inANSYS

Decide on the dimensionality of the model Try avoiding complications

Select the appropriate elementtypes

real constants

material properties


4/19

Definitions

Elementtypesdefine the mathematics

Truss

Beam

Shell Solid,...

Real constantsmay be needed for properties that cant becalculated from the geometry

Shell thickness

Layer info,...

Material propertiesare the engineering properties

Youngs modulus

Poissons ratio

...


5/19

Definitions

GEOMETRY 1D, 2D or 3D geometric model of the actual design to be

analysed

by itself has no solution capabilities

has almost all the dimensional properties

is used as the skeleton to the FE

FE Mesh contains the mathematics of the assumptions

DOF per node

interpolation functions


6/19

Definitions

BOUNDARY CONDITIONS (BCs) Constraints

Loads

Initial conditions

Pre-stressed

Initial velocity

Load Steps progressive loading

non-linear analysis


7/19

Definitions

KEYPOINTS smallest building blocks of a geometry

a line has 2 keypoints

LINES 2 keypoints are joined to make up a line

AREAS

An area is made of at least 3 straight lines, or 2 curved lines.

VOLUMES Volumes are made of areas


8/19

Hierarchy in ANSYS

Volume Areas

Lines

Keypoints

Mesh Element

Geometry(Volume, Area, Line, Keypoint)


9/19

Dependence in ANSYS

All objects in the hierarchy are dependentupon their underling objects:

ex: a LINE cannotbe deleted if it is part of an AREA ex: an AREA cannotbe deleted if it is part of a VOLUME

ex: a GEOMETRIC object cannotbe deleted if it is alreadyMESHED.


10/19

Defining the Geometry

Bottom-up Modeling

In bottom-up modeling, first keypoints are defined,

then keypoints are joined to form lines, lines are joined to form areas

and finally areas are joined to form volumes.

Since all the entities are hierarchically related, a lowerdimensional entity cannot be deleted if it is connected to a

higher dimensional entity.

The modelling commands are available underPreprocessor|Modelling. All commands are categorically andlogically ordered, they all use dialog boxes to accept dataand most of them have a HELPbutton to access the on-line

manual pages.


11/19

Defining the Geometry

Top-to-bottom Modelling

In top-to-bottom modelling, higher dimensional entitiessuch as lines, areas and volumes can be directly createdwhile their lower dimensional building blocks areautomatically created, i.e. , when a volume is createdthrough dimensions, all the areas, lines and keypointsnecessary to represent it are automatically created.


12/19

Modifying the Geometry

The actual geometry of the model is usuallymuch more complex than the available solid

primitives. Boolean operationsare used to put

together simple building blocks. some of thecommands are Add

Glue

Intersect

Subtract

Selecting operations are used to apply these commands.


13/19

Selecting Objects

Selection Operations

Almost all modelling operations are based around selecting thecorrect entity. Some basic selection concepts should beunderstood. By default all entities created are in the current

selection set unless otherwise instructed.

All selected entities are visible when plotted.

When selecting any entity, the source of the selection should bespecified. When starting a new selection the source should beFrom Full, where every entities are available for selection.

Reselectis used to start a new selection from the already selectedset, i.e. the entities other than the previously selected ones areinvisible to the next selection.

Also Selectwill expand the existing selection set.

Unselectwill remove the next selected entities from the selection

set.


14/19

Grouping Objects

Components

Componentsare a convenient way of referring to aselection.

Selectionsets can be saved using the CMcommand forlater recall.

All selections can be saved as a component classifiedaccording to its nature.


15/19

Meshing

Setting the Meshing Parameters

The accuracy of the solution is directly related to the densityof the mesh.

The size of the elements should be specified prior to themeshing of the model.

A denser mesh is desired around loads and critical locations

A coarser mesh can be used around regions of lesser

importance. The LESIZE command can be used for setting element size

or subdivision on the geometry with the help of variousselection filters.


16/19


17/19


18/19


19/19

intro to ansys

Documents