Shape optimization process
Active surface

In ProTOp the shape optimizer operates on the so called active surface. The FE nodes belonging to this surface are physically moved with the aim to improve the design. This active surface can be either

• the stripped surface, generated by mesh stripping (typically, after topology optimization), or
• the high-stress surface, defined by all outer surface patches of the free domain that exceed some stress level threshold.

In either case the active surface can be expanded by a desired bandwidth of elements (more precisely, element faces). It is important to note, however, that the shape optimizer operating within ProTOp is primarily intended to be used on stripped surfaces as a supplemental tool to improve the design after topology optimization.

NOTE. In ProTOp the shape optimizer is primarily intended to be used on stripped surfaces as a supplemental tool to improve the design after topology optimization.

Stripped surface

A stripped surface is typically generated by stripping the mesh by removing the void elements after topology optimization. The figure below shows an example structure with the stripped surface colored in light green.

Figure. Stripped surface (light green color): typically generated after topology optimization.

High-stress surface

A high-stress surface is defined by outer surface patches that fulfill the following two conditions:

• the patch belongs to a free domain of the model and
• the stress levels are higher than some specified threshold.

Note that fixed domain surface patches can not belong to this surface, even if the stresses are above the specified threshold value.

Figure. High-stress surface (scale colors; stress threshold is 50 MPa): can be easily identified by proper custom stress scale setup.

NOTE. Using the shape optimizer on high-stress surfaces should only be used in special situations, for example, to get some insight how the stresses would change if the structural domain would be adjusted. But after such information is available, it is recommended to go back and adjust the structural domain within the used CAD modeler.