Coordinate Systems

In Abaqus, different coordinate systems can be defined using the commands *SYSTEM, *TRANSFORM and *ORIENTATION.

The *SYSTEM option is used to determine the axes of the nodes in the local coordinate system. The coordinate systems (rectangular Cartesian, cylindrical, or spherical) are each set with the option *NODE with the parameter SYSTEM during the node definition.

The *TRANSFORM option is used to define a local displacement coordinate system of a node group. For example, this can be used to define boundary conditions.

The *ORIENTATION command is used to define a local coordinate system for the definition of material or element properties.

SIMULIA Tosca Structure requires that coordinate systems are applied for selecting and defining restrictions. As the same coordinate system is usually used in both the definition of the model and in the definition of the optimization task, the coordinate systems are loaded from the optimization preprocessor and are therefore available in the parameter definition. However not all types available in Abaqus are supported by SIMULIA Tosca Structure. Which combinations can be used in the parameter file is shown in the following table:

	*SYSTEM	*TRANSFORM	*ORIENTATION
Cartesian	Supported	Supported	Not supported
Cylindrical	Supported	Not supported	Not supported
Spherical	Supported	Not supported	Not supported

This concerns only coordinate systems, which are referenced in the parameter file. As long as they are not used in the optimization definition, all types can be present in the model.

No ID or name is assigned to coordinate systems in Abaqus. Therefore, SIMULIA Tosca Structure numbers them consecutively according to their order of appearance and labels them as CS_<nr>. The numeration begins with 1 as the name CS_0 is reserved for the standard global Cartesian coordinate system provided by SIMULIA Tosca Structure. Therefore, the first coordinate system from the input file has the name CS_1. All defined coordinate systems (with the command *SYSTEM) are first considered in the numeration and afterward the displacement coordinate systems (with the command *TRANSFORM) are considered.

The importance of the name allocation of the coordinate systems must be considered when defining a separate coordinate system in the parameter file. The numbered prefix CS_ should not be used at the start of the separate coordinate system to prevent the redefinition (and therefore invalid definition) of a name.