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ShepherdLab LW FEA-OPT (Python)

Lightweight 2-D frame and truss finite element analysis with stress-ratio thickness optimisation. Pure Python, built on NumPy and SciPy.

Chapter	Description
1 — Introduction	Overview, installation, project layout, conventions, and differences from the MATLAB version.
2 — Theory	Element formulation, global assembly, Newton–Raphson solver, stress recovery, and the optimisation algorithm.
3 — API Reference	Full documentation of every public class, method, and function.
4 — Worked Examples	Curved beam optimisation, truss topology optimisation, and a minimal custom problem.
5 — Profile Export Pipeline	Rasterisation, morphological cleanup, contour tracing, spline fitting, and SolidWorks import workflow.
A — File Listing & Error IDs	Complete file manifest and error ID reference.

# ShepherdLab LW FEA-OPT (Python)

Lightweight 2-D frame and truss finite element analysis with stress-ratio thickness optimisation. Pure Python, built on NumPy and SciPy.

Chapter	Description
1 — Introduction	Overview, installation, project layout, conventions, and differences from the MATLAB version.
2 — Theory	Element formulation, global assembly, Newton–Raphson solver, stress recovery, and the optimisation algorithm.
3 — API Reference	Full documentation of every public class, method, and function.
4 — Worked Examples	Curved beam optimisation, truss topology optimisation, and a minimal custom problem.
5 — Profile Export Pipeline	Rasterisation, morphological cleanup, contour tracing, spline fitting, and SolidWorks import workflow.
A — File Listing & Error IDs	Complete file manifest and error ID reference.

Script	What it does
`demo_beam.py`	Imports an S-shaped beam from an IGES file, runs linear and nonlinear analysis, optimises thickness, and exports a CAD-ready profile.
`demo_truss.py`	Builds a Warren truss programmatically, subdivides into fine elements, optimises, and exports with side-by-side before/after plots.

Workflow — every analysis follows four stages: define geometry → analyse → optimise → export.

Indexing — all node, element, and DOF indices are 0-based, following Python convention.

Core classes:

Class / Function	Module	Role
`StructureGeometry`	`structure_geometry.py`	Topology, materials, constraints, DOF maps
`FEAAnalysis`	`fea_analysis.py`	Linear and nonlinear solvers
`LoadCase`	`load_case.py`	Nodal loads and load-factor stepping
`optimize_thickness`	`optimize_thickness.py`	Stress-ratio thickness optimiser
`subdivide_truss`	`subdivide_truss.py`	Refine truss members into sub-elements
`import_csv_curve`	`importers.py`	Import 2-D curves from CSV
`import_igs_curve`	`importers.py`	Import 2-D curves from IGES/IGS
`export_profile`	`export_profile.py`	Rasterise and export CAD-ready profiles
`StructurePlotter`	`structure_plotter.py`	Visualisation utilities

Dependencies:

Package	Required	Used for
NumPy	Yes	Array operations, linear algebra
SciPy	Yes	Sparse matrices, `spsolve`
matplotlib	No (recommended)	Plotting and visualisation
scikit-image	For export only	Rasterisation, morphology, contour tracing