Overview of Displacement and Rotation


Parameter Name	Formula
DISP_X, DISP_Y, DISP_Z	$u_{i}$
ROT_X, ROT_Y, ROT_Z	$θ_{i}$
DISP_X_ABS, DISP_Y_ABS, DISP_Z_ABS	$\sqrt{{u_{i}}^{2}}$
DISP_ABS	$\sqrt{{u_{x}}^{2} + {u_{y}}^{2} + {u_{z}}^{2}}$

Analysis Types: Static Linear or Nonlinear Analysis


$K u = F$

where K might be linear or nonlinear.

For displacements and rotations, the following table shows the allowed combinations between the strategy and the items OBJ_FUNC and CONSTRAINT with C for controller and S for sensitivity based optimization. Tosca sensitivities support nonlinear contact, but material and large displacement theory are only supported by Tosca sensitivities for Topology optimization. Sizing, Shape and Bead optimization only allow linear material and small displacement theory.


	TOPO	SHAPE	BEAD	SIZING
OBJ_FUNC	S	S	S	S
CONSTRAINT	S	S	S	S

Displacements and rotations are the primary variables in the FEM solution. They are also very often the main interest of the FEM-analyst, for example, the maximal displacement. Displacements and rotations should be defined using a nodal id, although node groups might also be referenced. Large node groups can lead to major performance issues, see Group Operations for Design Responses.

Displacements and rotations can also be referenced in a local coordinate system.

Important:

It is always strongly recommended that the user defines design elements attached to nodes used in displacement definitions or reaction definitions (DRESP) as frozen elements. This stabilizes the optimization iterations and often leads to a significant lower number of optimization iterations.
When using solver sensitivities, all types of nonlinear analysis are supported. See Remarks for Sensitivity-Based Optimizations