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Configuring a dynamic, explicit procedure

An explicit, dynamic analysis is computationally efficient for the

analysis of large models with relatively short dynamic response times

and for the analysis of extremely discontinuous events or processes.

This type of analysis allows for the definition of very general contact

conditions and uses a consistent, large-deformation theory. For more

information, see

?

Explicit dynamic analysis,

?

Section 6.3.3 of the

Abaqus Analysis User's Manual

.

To create or edit a dynamic, explicit procedure:

1.

Display the

Edit Step

dialog box following the procedure outlined

in

?

Creating a step,

?

Section 14.9.2

(

Procedure type:

General;

Dynamic, Explicit

), or

?

Editing a step,

?

Section 14.9.3

.

2.

On the

Basic

,

Incrementation

,

Mass scaling

, and

Other

tabbed

pages, configure settings such as the time period for the step, the

maximum time increment, the increment size, mass scaling definitions,

and bulk viscosity parameters as described in the following procedures.

To configure settings on the Basic tabbed page:

1.

In the

Edit Step

dialog box, display the

Basic

tabbed page.

2.

In the

Description

field, enter a short description of the analysis step.

Abaqus stores the text that you enter in the output database, and the

text is displayed in the state block by the Visualization module.

3.

In the

Time period

field, enter the time period of the step.

4.

Select an

Nlgeom

option:

?

Toggle

Nlgeom

Off

to perform a geometrically linear analysis

during the current step.

?

Toggle

Nlgeom

On

to indicate that Abaqus/Explicit should

account for geometric nonlinearity during the step. Once you

have toggled

Nlgeom

on, it will be active during all subsequent

steps in the analysis.

For more information, see

?

Linear and nonlinear

procedures,

?

Section 14.3.2

.

5.

Toggle on

Include adiabatic heating effects

if you are performing an

adiabatic stress analysis. This option is relevant only for metal plasticity.

For more information, see

?

Adiabatic analysis,

?

Section 6.5.5 of the

Abaqus Analysis User's Manual

.

To configure settings on the Incrementation tabbed page:

1.

In the

Edit Step

dialog box, display the

Incrementation

tabbed page.

(For information on displaying the

Edit Step

dialog box, see

?

Creating

a step,

?

Section 14.9.2

, or

?

Editing a step,

?

Section 14.9.3

.)

2.

Choose a

Type

option:

?

Choose

Automatic

to allow Abaqus/Explicit to determine the

time incrementation automatically. For more information,

see

?

Automatic time incrementation” in “Explicit dynamic

analysis,

?

Section 6.3.3 of the Abaqus Analysis User's Manual

.

?

Choose

Fixed

to use a fixed time incrementation scheme. The

fixed time increment size is determined either by the initial

element stability estimate for the step or by a user-specified time

increment. For more information, see

?

Fixed time

incrementation” in “Explicit dynamic analysis,

?

Section 6.3.3 of

the Abaqus Analysis User's Manual

.

3.

If you selected

Automatic

time incrementation, perform the following

steps:

a.

Choose a

Stable increment estimator

option:

?

Choose

Global

to allow the global estimator to determine

the stability limit as the step proceeds. The adaptive,

global estimation algorithm determines the maximum

frequency of the entire model using the current dilatational

wave speed. This algorithm continuously updates the

estimate for the maximum frequency. The global estimator

will usually allow time increments that exceed the

element-by-element values.

?

Choose

Element-by-element

to allow Abaqus/Explicit to

determine an element-by-element estimate using the

current dilatational wave speed in each element.

The element-by-element estimate is conservative; it will

give a smaller stable time increment than the true stability

limit that is based upon the maximum frequency of the

entire model. In general, constraints such as boundary

conditions and kinematic contact have the effect of

compressing the eigenvalue spectrum, and the

element- by-element estimates do not take this into

account.

b.

Choose a

Max. time increment

option:

?

Choose

Unlimited

if you do not want to impose an upper

limit to time incrementation.

?

Choose

Value

to enter a value for the maximum time

increment allowed. Enter the value in the field provided.

For more information, see

?

Automatic time incrementation” in “Explicit

dynamic analysis,

?

Section 6.3.3 of the Abaqus Analysis User's

Manual

.

If you selected

Fixed

time incrementation, choose an option for

determining increment size:

?

Choose

User-defined time increment

to specify a time

increment size directly. Enter that time increment size in the field

provided.

?

Choose

Use element-by- element time increment estimator

to

use time increments the size of the initial element-by-element

stability limit throughout the step. The dilatational wave speed in

each element at the beginning of the step is used to compute the

fixed time increment size.

For more information, see

?

Fixed time incrementation” in “Explicit

dynamic analysis,

?

Section 6.3.3 of the Abaqus Analysis User's

Manual

.

If desired, enter a

Time scaling factor

to adjust the stable time increment

computed by Abaqus/Explicit. (This option is unavailable if you have specified

a

User- defined time increment

for the

Fixed

time incrementation scheme.)

For more information, see

?

Scaling the time increment” in “Explicit dynamic

analysis,

?

Section 6.3.3 of the Abaqus Analysis User's Manual

.

To configure settings on the Mass scaling tabbed page:

1.

In the

Edit Step

dialog box, display the

Mass scaling

tabbed page. For

background information on mass scaling, see

?

Mass

scaling,

?

Section 11.6.1 of the Abaqus Analysis User's Manual

.

(For information on displaying the

Edit Step

dialog box, see

?

Creating

a step,

?

Section 14.9.2

, or

?

Editing a step,

?

Section 14.9.3

.)

2.

Choose one of the following options for specifying mass scaling:

?

Choose

Use scaled mass and “throughout step” definitions

from the previous step

if you want mass scaling definitions

from the previous step to propagate through the current step. If

you choose this option, you can skip the remaining steps in this

procedure.