Topology optimization examples

[artofscience]

Contributions to modules:

1. Allow for additional values on DOFs in assembly
2. Modules for stress calculation, vonmises stress and constraint aggregation (in ex_volume_stress.py)
3. Module for enforcing symmetry (in ex_flexure.py)
4. StaticCondensation module for use in kinetostatic formulation (ex_compliant_mechanism_kinetostatic.py)

Examples:

1. Compliant mechanism design using springs (Sigmund formulation)
2. Compliant mechanism design using kinetostatic approach (Koppen formulation)
3. Volume minimization under stress constraints
4. Compliance minimization under pure self-weight with optional stress constraints (different bc)
5. Optional stress constraints to design of flexures

Bug fixes:

1. Fixed sensitivity analysis of SoQ as to allow for Nonetype sensitivity input

Tests:

1. More tests for SoQ (test for Nonetype input sensitivity)
2. Test StaticCondensation module

Documentation:

1. Added documentation to multiple existing examples