Background

In ProTOp the shape optimization process is considered to be a continuous process which can be either in a

• running (active) or
• interrupted (inactive)

█ Important notes

The shape optimization procedure implemented in ProTOp is a specialized procedure designed to achieve certain benefits. In order understand properly its purpose, usability, and limitations, the following notes should always be kept in mind:

• This procedure runs exclusively on stripped surfaces. Note that all stripped surfaces of the model are always affected.
• Mesh adjustments are done exclusively by moving the surface nodes in the outer normal direction.
• The amount of nodal movement is determined by the nodal sensitivity value; a larger sensitivity number results in a larger node movement.
• Although the sensitivity fields are available for both stress and eigenfrequency analyses, the only really useful purpose of this procedure is to reduce stress concentrations observed in stress FEA.
• Note that moving a FE node in the outer normal direction typically reduces the stress concentration observed at this node. However, this is not guaranteed to be always true. There are special situations, where such a nodal movement increases the stress concentration, especially, if the previous topology optimization included technological constraints.
• This procedure is designed to make rather minor adjustments of nodal positions. Therefore, technological constraints and configurators are not considered in this process.

█ Operation parameters

The optimization process can be controlled by a set of basic and a set of advanced parameters. The advanced parameters can be accessed via the Optimization parameters dialog by selecting the Parameters ... command from the Advanced controls drop-down menu. In a typical optimization task, these parameters do not require any adjustments.

The set of basic parameters is accessible directly from the optimization dialog. The following parameters are available:

Number of cycles to run
Range: [1, 50]
This parameter defines the number of shape optimization cycles to run. Each cycle performs the needed FEA which is then used for all subsequent steps within this cycle.

Number of steps per cycle
Range: [1, 5]
This parameter defines the number of steps per one optimization cycle. Each step contains one obligatory sensitivity-related shape improvement, one optional mesh improvement, and one optional mesh smoothing.

Process intensity factor
Range: [0.0, 1.0]
This parameter defines the extent of adjustments made to the model. Low intensity means that only small adjustments are performed and the required processing time is also relatively low. Note that a value of ZERO means that the shape improvement procedure is not run at all. This might be useful if the model contains semi-contact materials. In such cases, a few successive FEAs are needed to get proper stress state. Once the FEA results stabilize, the optimization can be run normally.

Localization factor
Range: [0.0, 5.0]
This parameter determines whether shape changes are more or less evenly distributed. A higher value close to 5 means that only the regions with higher sensitivity values are significantly changed. On the other hand, lower values close to 0 mean that all regions are changed more evenly and proportional to their respective sensitivity values.

Volume centering factor
Range: [-0.5, +0.5]
This parameter influences the size and sign of volume variations of the model. The implemented shape optimization procedure typically results in slight model volume increase. This parameter can be used to tune the volume changes of the model to some extent.

█ Additional automatically tuned parameters

Both, mesh improvement and mesh smoothing processes may be included into each cycle of the shape optimization procedure. It is recommended that both of these processes are always included.

█ Run FEA and pause options

Several run FEA and pause commands are available from the Run cycles drop-down menu:

Run FEA only
This runs the FEA of unsuppressed static (stress) and modal (eigenfrequency) load cases and pauses without doing any optimization step. This might be useful for checking the structural response without doing any optimization.

Run ALL stress FEA cases
This runs the FEA of all (suppressed and unsuppressed) static (stress) load cases and pauses without doing any optimization step. This might be useful for checking the structural response of all stress load cases, including the disabled ones.

Run ALL eigenfrequency FEA cases
This runs the FEA of all (suppressed and unsuppressed) modal (eigenfrequency) load cases and pauses without doing any optimization step. This might be useful for checking the structural response of all eigenfrequency load cases, including the disabled ones.

█ Other commands and options

Several other commands and options are available from the Additional controls drop-down menu:

Parameters ...
This command opens the Optimization parameters dialog, which provides access to advanced optimization parameters.

Load cases ...
This command opens the Optimization load cases dialog, which enables monitoring and management of currently active load cases.