PRIMER 22.1

(DEFINE_) COORDINATE: Defining Coordinate Systems

The * DEFINE_COORDINATE keyword is used to create local coordinate systems. Three points in space, which form two vectors are required. The coordinate system is then computed from the cross product of these vectors. They are used when a system is required that is not orthogonal to the global axes. For example boundary conditions, orthtropic materials and beam orientations.

Coordinate systems use unique labels and, although part of the * DEFINE keyword, their labels do not clash with other * DEFINE_xxx entities. For example it is legal to have ( * DEFINE_ )BOX#1 and (* DEFINE_ )COORDINATE #1 .

This figure shows the main menu for the editing of co-ordinate systems.

define-curvetable

All functions have their standard meanings as given in Standard Keyword Top Level Menu Options

CREATE Making a coordinate definition

This figure shows the basic CREATE/UPDATE COORDINATE_SYSTEM panel.

There are three ways in Ansys LS-Dyna of defining a coordinate system:

DEFINE_COORDINATE	_NODES
	_SYSTEM
	_VECTORS

The popup menu gives these options:

The detailed layout of the panels and definition methods vary slightly as shown below.

DEFINE_COORDINATE_NODES

Is defined by three nodes:

N1 : origin
N2 : Gives local X axis from N1N2
N3 : forms the local XY plane N1N2N3

Methods of defining the nodes:

3 NODES

Instead of defining each node separately, all nodes can be screen-picked together. Simply screen pick three nodes in the order:

N1 (origin)
N2 (local X vector)
N3 (lies on local XY plane)

Alternatively use the individual popup menus to select nodes, or simply type in their labels.

DEFINE_COORDINATE_SYSTEM

Is defined by three points:

P1 : origin
P2 : Gives local X axis from P1P2
P3 : forms the local XY plane P1P2P3

Methods of defining the points:

3 NODES

(Only their coordinates are used)

Instead of defining each node separately, all nodes can be screen-picked together. Simply screen pick three nodes in the order:

N1 (origin)
N2 (local X vector)
N3 (lies on local XY plane)

Alternatively use the individual popup menus to select nodes, or simply type in their labels.

Or simply type in the coordinates explicitly.

DEFINE_COORDINATE_VECTORS

Is defined by the origin and 2 points:

Or : origin
P1 : Gives local X axis from OrP1
P2 : forms the local XY plane OrP1P2

Methods of defining the points:

2 NODES

(Only their coordinates are used)

Instead of defining each node separately, both nodes can be screen-picked together. Simply screen pick three nodes in the order:

N1 (local X vector)
N2 (lies on local XY plane)

Alternatively use the individual popup menus to select nodes, or simply type in their labels.

Or simply type in the coordinates explicitly.

COPY Copy existing coordinate(s) to make a new coordinate

The selected coordinates are copied. (Coordinates do not "own" anything, so the concept of recursive copying does not apply.)

MODIFY Modifying the attributes of an existing coordinate

MODIFY functions in the same way as CREATE , except that an initial definition will be present.

Any modifications made to the section definition will not be made permanent until the UPDATE_CSYS button is pressed. At this point a the local copy which has been updated is used to overwrite the version in the model.

DELETE Delete existing coordinate definitions

The selected coordinates are deleted.

Coordinate definitions do not "own" anything, so the concept of recursive deletion does not apply, however a coordinate that is referred to (ie "owned") by some higher order item will not be deletable unless that item is deleted too, or its reference to the coordinate removed.

They may also be drawn in other contexts (for example contacts) if their display as "associated data" in the ENT ity Viewing box is selected.

Previous | Next

(DEFINE_) COORDINATE: Defining Coordinate Systems