82215765 autodyn basics

5/21/2018 82215765 Autodyn Basics

1/32

3-1ANSYS, Inc. Proprietary

2009 ANSYS, Inc. All rights reserved.February 27, 2009

Inventory #002665

Chapter 3

AUTODYN Basics

ANSYS AUTODYN

5/21/2018 82215765 Autodyn Basics

2/32

AUTODYN Basics



Inventory #002665

Training ManualStructured and Unstructured Parts (Meshes)

An AUTODYN Part can use aStructured mesh or an Unstructuredmesh

Structured meshes can be generated inAUTODYN

Use (I,J,K) index space

Unstructured meshes must be imported(e.g. from Workbench)

Lagrange Parts (Solid, Shell, Beam)

Can be Structured or Unstructured Unstructured Parts are solved more

efficiently (speed and memory)

A Structured Part can be converted to anUnstructured Part prior to solving

Lagrange Parts (structured or

unstructured) can be used to fill regionsof Euler and SPH Parts

Euler and ALE Parts

Always Structured

Euler meshes are usually rectilinear

5/21/2018 82215765 Autodyn Basics

3/32

AUTODYN Basics



Inventory #002665

Training Manual

i

j i = 1 i = 11

j = 1

j = 6

Structured Parts - Index Space

Each Structured Part in AUTODYN has a defined index space (i,j) in 2D or(i,j,k) in 3D, where i, j and k are integer values ranging from 1 to Ni, Nj, Nk This index space is always rectangular

5/21/2018 82215765 Autodyn Basics

4/32

AUTODYN Basics



Inventory #002665

Training Manual

x

y

i = 1 i = 11

j = 1

j = 6

Structured Parts - Physical Space

Each Structured Part is also defined in a physical xyz-space, where x,y and z are real values

The mesh can have a general shape in physical space

5/21/2018 82215765 Autodyn Basics

5/32

AUTODYN Basics



Inventory #002665

Training Manual

Index Space Physical Space

Unused

Elements

Not all elements defined in the index space need to be defined inphysical space

Elements not assigned a material are Unused

Allows complicated geometries to be meshed

Structured Parts Unused Elements

5/21/2018 82215765 Autodyn Basics

6/32

AUTODYN Basics



Inventory #002665

Training Manual

Part Wizard allows automatic generation of qualitystructured Parts for predefined (Predef) geometries

2D Volume Box, Quad, Circle, Ogive, Rhombus, Triangle, Wedge

3D Volume Box, Hex, Cylinder, Sphere, Ogive, Fragments/Bricks

Shells Plate, Cylinder

Manually build quality structured meshes Nodes

Lines

Surfaces

Volumes

Import Structured Meshes

ICEM-CFD

TrueGrid

Part

Wizard

Creating Structured Parts

5/21/2018 82215765 Autodyn Basics

7/32

AUTODYN Basics



Inventory #002665

Training ManualPart Wizard

Geometry Zoning Fill

Part Wizard generates a Part in three steps

Define a Predef geometry

Define the zoning

Fill the whole Part

5/21/2018 82215765 Autodyn Basics

8/32

AUTODYN Basics



Inventory #002665

Training ManualPart Wizard 2D Box Predef

5/21/2018 82215765 Autodyn Basics

9/32

AUTODYN Basics



Inventory #002665

Training ManualPart Wizard 2D Circle Predef

5/21/2018 82215765 Autodyn Basics

10/32

AUTODYN Basics



Inventory #002665

Training Manual

Ogive

Quads

Part Wizard 2D Predefs

Wedge

Rhombus

5/21/2018 82215765 Autodyn Basics

11/32

AUTODYN Basics



Inventory #002665

Training ManualPart Wizard 3D Box Predef

5/21/2018 82215765 Autodyn Basics

12/32

AUTODYN Basics



Inventory #002665

Training ManualPart Wizard 3D Cylinder Predef

5/21/2018 82215765 Autodyn Basics

13/32

AUTODYN Basics



Inventory #002665

Training Manual

Sphere

Bricks / FragmentsHex

Ogive

Part Wizard 3D Predefs

5/21/2018 82215765 Autodyn Basics

14/32

AUTODYN Basics



Inventory #002665

Training Manual

Plane

Cylinder

Part Wizard 3D Shell Predefs

5/21/2018 82215765 Autodyn Basics

15/32

AUTODYN Basics



Inventory #002665

Training Manual

Step-by-step generation of meshesusing

Node

Line

Surface

Volume

Interpolation Extrusion

Manual Zoning

5/21/2018 82215765 Autodyn Basics

16/32

AUTODYN Basics



Inventory #002665

Training Manual

ANSYS, ICEM-CFD

Powerful 3D hex mesh

generator

Direct links to CAD

CATIA, Pro/Engineer, SDRC I-

DEAS, SolidWorks, Unigraphics, .

An interface to ICEM-CFD isprovided to allow import of

structured (mapped) meshes

into AUTODYN

ICEM multiblock meshes (.geo file)

Same import procedure as for

TrueGrid

Importing 3D Structured Parts

5/21/2018 82215765 Autodyn Basics

17/32

AUTODYN Basics



Inventory #002665

Training Manual

Materials and Initial Conditions are defined fromthe Materials and Init. Cond. Dialog Panelsrespectively

Once defined, they can be applied to Parts usingthe Part Wizard and / or the Fill options in theParts dialog panel.

Define

Apply

Apply (Part Wizard)

Materials and Init ial Conditions

5/21/2018 82215765 Autodyn Basics

18/32

AUTODYN Basics



Inventory #002665

Training ManualFill ing Parts with Materials and Initial Conditions

Additional Block Fills

The Wizard fills each Part with one material

Additional fills can be performed after the Wizard

completes

Each fill replaces materials / initial conditions of previous fills

Lagrange elements are filled if their center lies inside

the fill region (no multi-material cells are permitted)

Additional Geometry Fill

Wizard Fill

5/21/2018 82215765 Autodyn Basics

19/32

AUTODYN Basics



Inventory #002665

Training Manual

Boundary Conditions are defined from the Boundaries Dialog Panel

Once defined, Boundary Conditions can be applied to structured Partsusing index space from the Boundary option in the Parts dialog panel

Boundary Conditions

Define

Apply

5/21/2018 82215765 Autodyn Basics

20/32

AUTODYN Basics



Inventory #002665

Training Manual

Boundary Conditions can be applied the outside faces of a mesh andthe outside faces of Unused regions of the mesh

The default boundary condition is:

Lagrange: Free boundary (pressure = 0.0)

Euler : Rigid wall (no flow, velocity = 0.0)

Unused elements

Filled elements

Boundary Conditions

can be applied here

Boundary Conditions

5/21/2018 82215765 Autodyn Basics

21/32

AUTODYN Basics



Inventory #002665

Training Manual

Constant

t

Trapezoid

t

Triangular

t

ExponentPk = Pe

-kt

t

Usersubroutine

EXSTR

t

Applied to Lagrange Parts

Piecewise

t

Boundary Conditions: Stress

5/21/2018 82215765 Autodyn Basics

22/32

AUTODYN Basics



Inventory #002665

Training Manual

Applied to Lagrange, ALE, Shell, Beam andSPH Parts

X, Y, Z Velocity Constraints

Constant Fixed at a constant value

Limit Limit position between max and min coordinates

Displacement constraint in Explicit Dynamics

Piecewise Piecewise linear segments

General Velocity Constraints

Fixed constant velocities in X, Y, Z (3D) and

fixed rotational velocities about coordinate axes

User subroutine EXVEL

User Time-Dependant X, Y, Z velocity

Boundary Conditions: Velocity

5/21/2018 82215765 Autodyn Basics

23/32

AUTODYN Basics



Inventory #002665

Training Manual

Applied to Beam Parts

Nodal force boundary conditions

Constant, Piecewise, User

Subroutine EXFOR

x, y, z and general directions

Element force/unit lengthboundary conditions

Constant, Piecewise, User

Subroutine EXFOR

x, y, z and general directions

Boundary Conditions: Force

5/21/2018 82215765 Autodyn Basics

24/32

AUTODYN Basics



Inventory #002665

Training Manual

Applied to Lagrange, ALE and Euler Parts

Transmits waves through cell faces

Only the perpendicular component istransmitted

The impedance of the boundary can be

specified

If impedance is set to zero the

impedance of the adjacent cell is used

The Transmit boundary condition is only

approximate and should be placed asfar as possible from regions of interest

For air blast in Euler, Outflow boundary

with p = 0.0 is recommended

cI =

Boundary Conditions: Transmit

5/21/2018 82215765 Autodyn Basics

25/32

AUTODYN Basics



Inventory #002665

Training Manual

Applied to Euler Parts

Inflow

Specify the full state of the material flowinginto the grid (density, internal energy andvelocity)

Outflow (P = = e = 0)

Only the preferred material needs to be set

Reverse flow can be specified. If conditionsof reverse flow are reached, an externalreservoir with prescribed conditions controlsinflow

You must specify the full state of the materialflowing into the grid (density, internal energy

and velocity)

The Outflow boundary condition is onlyapproximate and should be placed as far aspossible from regions of interest

Boundary Conditions: Flow

5/21/2018 82215765 Autodyn Basics

26/32

AUTODYN Basics



Inventory #002665

Training ManualLagrange Interactions

Options are the same as those used in Explicit

Dynamics (ANSYS)

Details given in the Body Interactions section of the

Explicit Dynamics training course

Contact type

Trajectory (default)

Method (Formulation)

Penalty

Decomposion Response

Shell Thickness Factor

External Gap (Proximity Based)

Gap Size = Pinball Factor

Parts must be initially separated by the Gap Size

5/21/2018 82215765 Autodyn Basics

27/32

AUTODYN Basics



Inventory #002665

Training Manual

AUTODYN uses single precision to make optimum use of solver powerand memory, so the choice of units is important, particularly for Eulerproblems

Avoid pressures below 10-6 of a unit

Avoid cell masses less than 10-6 of a unit

The default set of units work well for virtually all problems

Length mm

Mass mg Time ms

Velocity m/s

Force mN

Stress kPa

Density g/cm3

Energy mJ

Workbench Units will be converted to the chosen AUTODYN units whenlinked

Units

5/21/2018 82215765 Autodyn Basics

28/32

AUTODYN Basics



Inventory #002665

Training Manual

Wrapup Criteria

Must specify Cycle limit and Time limit

AUTODYN will stop and give warning if

energy error exceeds Energy fraction(default 5%)

Timestep Options

Defaults are usually OK

If Initial timestep is left zero, it is computed

as half the stability timestep

If Minimum timestep is left zero, it is

computed as 1/10th of the Initial time step

Safety factor can be safely increased to 0.9

for most Lagrange calculations

Solution Controls

5/21/2018 82215765 Autodyn Basics

29/32

AUTODYN Basics



Inventory #002665

Training ManualConservation Equations

Mass and Momentumare conserved exactly

Energy is notconserved exactly

Practical numericalmethods which arefully conservative haveproblems of stabilityand can be noisy

Conservation ofenergy andmomentum can bemonitored using

history plottingfeatures. Good modelset-ups and analyseswill tend to have lowerrors

Problem

Good energy

conservation

5/21/2018 82215765 Autodyn Basics

30/32

AUTODYN Basics



Inventory #002665

Training Manual

Save Files / Results Files

Frequency specified by

Cycle increment

Time increment

Calculation can be re-started from Save files(not Results files)

Results files are significantly smaller than

Save files

Plots can be created from any Save file orResults file

Animations can be created from a sequence

of Save / Results files

More flexible than Capture image

Output Controls

5/21/2018 82215765 Autodyn Basics

31/32

AUTODYN Basics



Inventory #002665

Training Manual

Results Files (3D only)

Used to create plots

Allows post-processing of large models on

computers with limited resources

Files are stored in a sub folder, ident_adres

Base files ident_bcyc.ad_base

Stores model data required by Results files

Must be present to load Results file data

Results files ident_bcyc_ncyc.adres

bcyc - the cycle number for the Base file

ncyc - the cycle number for the Results file

Output Controls

5/21/2018 82215765 Autodyn Basics

32/32

AUTODYN Basics



Inventory #002665

Training ManualWorkshop 1: 2D Fragment Impact

Goal:

Model a multi-materialcylindrical fragmentimpacting a plate

Procedure:

Start AUTODYNstandalone

Set up the problem inusing 2D AxialSymmetry

Solve the problem

View the results

Create animations ofthe results

82215765 autodyn basics

Documents