With Abaqus/CAE it is now possible to author, run and postprocess optimizations powered by the SIMULIA Tosca Structure technology. In this section you will find some helpful tips related to key functionalities of the Optimization Module.

How to Set Up an Optimization Task Taking Multiple Nonlinear Load Scenarios into Accounts

The great power of Tosca optimization technology is its capability to find optimal designs for structures with nonlinear behavior. To achieve realistic and valuable optimization results it’s necessary to consider all relevant critical load scenarios, which therefore have to be incorporated into a single optimization. The simulation of independent nonlinear load scenarios has to be done across multiple separate input decks instead of based on each other sequential STEP definitions in a single input deck.

Here’s What You Do:

1. Create multiple copies of your model, containing the same geometrical data (mesh, section and material definitions, etc.) and in each copy define a specific nonlinear analysis step with its particular boundary conditions and loads.
2. Import all models in Abaqus/CAE. This makes all step definitions visible within a single Abaqus/CAE database and allows their use in one optimization setup.
3. Attached to one of the models, create an optimization task of the desired type (topology, sizing, or shape optimization).
4. Create several design responses, each associated with a particular nonlinear step inherited by the imported models.
5. All design responses are now available in the optimization tree and can be used in a single optimization as constraints or combined in an objective function.
6. When an optimization process is launched, the engine automatically submits all models in the database for analysis and extracts the structural responses of the different nonlinear load scenarios.

Unified Approach for Global Stiffness Optimizations

A common approach for global stiffness optimizations is to use the strain energy of the whole structure as a performance measure. However, the direction of the objective (minimize or maximize) depends on whether the deformations are force, displacement or thermally driven. In mixed scenarios selecting to minimize or maximize the strain energy does not guarantee a stiffer structure. Tosca optimization technology now offers a unified measure, called “Energy Stiffness Measure” that can be used in all situations for sensitivity optimizations without having to differentiate between the deformation types.

Here’s What You Do:

1. Create a design response of type Energy stiffness measure over all elements.
2. Always use in the objective function the target minimize.

Postprocessing of Optimization Results in Abaqus/CAE

Two native Abaqus/CAE functionalities help to intuitively post process the results of Tosca Structure optimizations.

View Cut

When you open an output database from a topology optimization task you’re usually interested in visualizing the optimized material distribution, called MAT_PROP_ NORMALIZED. A View Cut based on the density isosurfaces is already automatically created and activated to hide areas where structural elements have relative densities below a defined threshold. Additionally, the animation of the optimization design cycles shows dynamically the redistribution of the material during the optimization process.

Link Viewports

Typically, the mechanical behavior of the original (reference) structure needs to be compared to the optimized design. Loading both models into two separate viewports and linking them enables synchronized motion and intelligible snapshots for comprehensive analysis of the results.

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This article was originally published in the October 2014 issue of SIMULIA Community News magazine.