Optimization

When risk and issue areas are identified, and their root cause (mode shapes and frequency), one can setup an optimization solver deck to get solution proposals. In the squeak and rattle world, problems are categorized as follows:
  • Systematic Issues
  • Non-systematic Issues

Systematic Issues

  • Problems that will appear consistently across the population of products, independently of tolerance variations or small changes in the structure.
  • Identified to be profound Design issues that require change of mounting strategy
The advantages of choosing topology or Systematic optimization are as follows:
  • OptiStruct's design-synthesis technology uses the topology optimization approach to generate innovative concept design proposals. OptiStruct generates an optimal design proposal for the connectors layout of the design based on user-defined design space and design targets.
  • In SnRD Modal Frequency Response analysis is used as the optimization load case with an objective of minimizing the modal relative displacement across the selected E-Line.
  • SnRD Optimization module, automatically converts the time domain excitations to frequency domain for creating the MFREQ loadcase. Amplitude and phase are considered.
  • The design variable for Topology optimization is the CBAR element connecting the Master and Slave components.
  • Optimization can be done for the response at single frequency or for a band of frequencies.

Non-systematic Issues

  • Problems that will appear in a portion of the population of products. They highly depend on tolerances and variations, and are often not detected during physical validation due to a lack of representative tested population
  • Typical root cause is a lack of local stiffness

On the Analysis side, the optimization input deck is generated automatically with all required solver cards. The solution type is a Modal Frequency Analysis, where the objective is to minimize Relative Modal displacement at one or multiple locations for a specific frequency, or a frequency range defined by the user. In the case of the 2D free-size optimization, the analyst can define the allowable thickness range for the selected parts.

The advantages of choosing free size or Non Systematic optimization are as follows:
  • Free-size optimization (targeting Non-Systematic issues) in OptiStruct optimizes the thickness of every element in the design space to generate an optimized thickness distribution in the structure, for the given objective under given constraints.
  • In SnRD Modal Frequency Response analysis is used as the optimization load case with an objective of minimizing the modal relative displacement across the selected E-Line.
  • SnRD Optimization module automatically converts the time domain excitations to frequency domain for creating the Modal Frequency (MFREQ) loadcase. Amplitude and phase are considered.
  • The design variable for free-size optimization is the thickness of the shell elements on the surfaces.
  • Optimization can be done for the response at single frequency or for a band of frequencies.