kul-49 4100 abaqus instructions

Kul-49.4100 Computer exercise Janne Ranta - 2010

Some instructions related to use of Abaqus FE-code

General

In Abaqus/CAE, models are constructed by operating in different modules.

1) PART Module:

Create part or multiple parts to be used in your model.

2) PROPERTY Module:

Define materials, cross sectional properties, point masses etc.

3) ASSEMBLY Module:

Select and assemble parts you want to include in your model. Simply, what you see here is

your model geometry.

4) STEP Module:

Define analysis step(s) (problem type) and set-up solver parameters. In here, you can also

have control over on what and how much Abaqus solver writes in output database (i.e. result

file with odb-extension).

5) INTERACTION Module:

Set-up contacts and different kind of constraints.

6) LOAD Module:

Define initial conditions, boundary conditions and loadings etc.

7) MESH Module:

Mesh your model (= create finite element model) here. Choose appropriate element type(s)

and mesh density.

8) JOB Module:

Create a job from your model. Basically, in here you choose a prefix for your model input

and result files. Abaqus writes your model input file automatically and submits it to solver

for analysis. Complete input files can also be submitted for analysis manually from the

command prompt (e.g. c:\temp\Abaqus job=example input=some_input.inp).

9) VISUALIZATION Module:

View results related to your model. As an alternative, you can use separate program called

Abaqus viewer to open and visualize output database (odb) files.


Orphan mesh parts

In some cases, it’s easier to create model geometry outside Abaqus/CAE GUI. For example, in

Abaqus, beam elements are meshed on wire features (paths) that can be modeled only as planar (see

Figure 1). Therefore, out of plane paths to be meshed with beam elements (e.g. coil springs) cannot

be directly modeled by using Abaqus/CAE GUI.

Figure 1. In Abaqus, it’s not possible to create other than planar wire features.

Instead of GUI modelling, one can create orphan mesh parts (orphan mesh is not based on any

geometrical feature). To illustrate this, a simple Abaqus input file (say example.inp ) that

defines a part geometry as an orphan mesh is shown below.

** Abaqus input file

*Part, name = Example

*Node

1, 0. , 0. , 0.

2, 0.5 , 0. , 0.

3, 1. , 0. , 0.

4, 1. , 0. , 0.5

5, 1. , 0. , 1.

*Element, Type = B32

1, 1, 2, 3

2, 3, 4, 5

*End part

*Assembly, name = Assembly

*Instance, name = Example-1, part= Example

*End Instance

*End Assembly


The first row “** Abaqus input file ” is actually a comment line. Thus, to add comments in

input file, type “** ” at the beginning of a line. All meaningful commands or keywords are given by

using single asterisk “* ” character at the beginning of a line. Keywords are explained more

carefully in Abaqus documentation (Abaqus Keywords Reference Manual). Keywords “*Part ” and

“*End part ” are telling that all commands between corresponding lines do something in the Part

module. Especially, the keyword “*Part, name = Example ” defines a part named “Example ”.

After the keyword “*Node ” five nodes are defined (pattern: node number, x-coord., y-coord., z-

coord.). To create more nodes, one can simply add lines by following the same pattern. Next, the

keyword “*Element, type=B32 ” is used to define two beam elements (pattern: element number,

node 1, node 2, node 3). In here B32 refers to three noded beam element (beam with end nodes and

mid-node). In all cases, it’s important to know what kind of elements are used (see Abaqus analysis

user’s manual, 25.3.8 Beam element library). Finally, an instance created from the part “Example ”

is placed in an assembly by utilizing keywords “*Assembly ”, “*Instance ”, “*End instance ” and

“*End assembly ”.

Actually, the previous code defines the geometry familiar from Kul-49.4100 exercise 1, problem

4P. The code says nothing about materials and beam orientations (the directions of local y - and z -

coordinate axes). Therefore, many other inputs are needed to have a complete Abaqus model.

Anyway, the previous code can be opened in Abaqus/CAE by choosing File > Import > Model >

example.inp . All other definitions and additional parts (if any) can be defined by using

Abaqus/CAE GUI (see. http://users.tkk.fi/jpranta3/4100_2010/example.html)

In the case of spring geometry, a proper model is defined by hundreds of nodes and elements.

Therefore it’s recommended to use some spread sheet computation program or other solution to

automatize the orphan mesh (input file) generation. Of course, all other techniques to construct the

model are accepted too. Note! Abaqus student edition allows 1000 nodes per model. This limitation

should not be a problem in the case when the model is constructed by using beam elements.

CAE = Complete Abaqus Environment

GUI = Graphical user interface


Modeling point masses in Abaqus:

In part module, create a new point part by choosing

[Part] → [Create…]→ Modeling space = 3D, Type = Deformable, Base

feature = Point → Enter the coordinates of the point (e.g. 0.0, 0.0, 0.0)

In property module, define mass properties for the point just created:

Make the point part visible by choosing correct part from the part drop

down menu. Choose [Special] → [Inertia] → [Create…] → Point

mass/inertia → Select point to assign point mass/inertia → Make all

necessary mass and rotary inertia inputs and click OK

In assembly module, assemble the point part into correct position by commanding

1) [Instance] → [Create…] → Choose correct part and click OK

2) [Instance] → [Translate] → Select the point part → Input

coordinates for the start and end points of the translation vector

In interaction module, create a connection between the point part and some other part of

the model (e.g. the end point of the spring)

1) Define two sets; one for the point mass (say Set-B) and another for the

point on which the point mass will be connected (say Set-A). Choose

[Tools] → [Set] → [Create…] → Geometry → Select the geometry or

nodes for the set

2) Constraint equations can be used to connect different parts of the model.

Go to [Constraint] → [Create…] → [Equation] → Input constraint

equation (see figure 2) and click OK.

Equations for rigid link are useful here (see Kul-49.4100 lecture notes L1-

32): B A A ABu u θ ρ= + ×

�

��

& B Aθ θ=� �

All together 6 equations need to be defined (i.e. components of above two

vector equations). In addition, equations need to be given in “standard”

form

B A A AB 0u u θ ρ− − × =�

��

& B A 0θ θ− =� �


Figure 2. The input of the first constraint equation A B A A A A 0B B

x x z y y zu u θ ρ θ ρ− + + − = (in

case where A 0.25B

yρ = and A 0.50B

zρ = )

For more information, see “31.2.1 Linear Constraint Equations” from Abaqus Analysis

User’s Manual.

kul-49 4100 abaqus instructions

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