# Presentation: 320533

## OOF Project Update

- Rhonald Lua, Andrew Reid,
- Stephen Langer, Valerie Coffman

## Outline

- Automatic Skeleton construction
- One-dimensional interfaces
- 3D Viewer mock-up
- Plasticity overview

## I. Automatic Skeleton(Stephen Langer)

- Encapsulates an effective strategy for combining and tuning skeleton modification methods to yield a good mesh.
- Accessible as a single button in oof2’s Skeleton page.

## Auto-Skeleton Components

- Initial skeleton with resolution at *maxscale*
- Refine elements to resolution *minscale*
- SnapRefine (1x)
- Rationalize (2x) – to fix badly-shaped elements.
- Smooth (1x)

- Supply a few parameters:

- Important: *maxscale,*
*minscale, threshold*

- Recipe:

## Auto-skeleton example

- Start: 1. Microstructure/image

- 2. Initial skeleton

*maxscale*

*minscale*

- 3. Refine skeleton

- Homogeneity index = 0.846
- 81 elements

- Homogeneity index = 0.890

## ...example continued

- 4. SnapRefine skeleton
- (place new edges and nodes at material boundaries)

- Homogeneity index = 0.890

- Homogeneity index = 0.981

- 3.

## ...example continued

- Homogeneity index = 0.981

- Homogeneity index = 0.981

- Homogeneity index = 0.982

- 5. Rationalize skeleton
- (fix badly-shaped elements)

- Finish: 6. Smooth skeleton
- (move a node to the average position of its neighbors. Improves element quality and/or shape.)

- 4.

## ...example continued

- 6. Final mesh

- Homogeneity index = 0.982
- 1842 elements

## II. One-dimensional Interfaces: goals

- Define one dimensional interfaces and create associated 1-D elements within 2-D mesh.
- Incorporate physics of surface (line) tension, heat source/line charge. Define cracks (insulation) and jumps or discontinuities in field values across an interface.
- Attach materials and properties to 1-D elements. Specify constitutive rules.

## “Cracks”

- Initial skeleton

- Deformed mesh

- User-defined interfaces
- (skeleton boundaries)

- Displacement

## ...continued

- Stress (trace) field

## Field Jump/Discontinuity

- Solved mesh (thermal)

- 0

- T=2

- T=0

- Skeleton with interface

- 2

- T(upper)-T(lower) = 1

## Heat Source/Line Charge

- (Demo implemented using neumann boundary condition mechanism in oof2.)

## Line Tension

- Skeleton with zig-zag interface

- Deformed mesh

- (Demo implemented using force boundary conditions on the nodes.)

## III. OOF 3D Viewer

- (Actual VTK app embedded in this document, based on ActiViz example.)

- Rely on the Visualization ToolKit (VTK) from KitWare Inc. for the visualization and graphics pipelines.

- vtkRenderWindow control

## Mock-up(Valerie Coffman)

- Written in Python, VTK, PyGTK and PyGTKGLExt.
- GTK provides GUI controls. PyGTKGLExt provides drawing area.

- 3D microstructure constructed from 2D image slices.
- Has (some) capabilities in common with MayaVi, ParaView, and VolView, which are also based on VTK.

## Features of the Viewer

- View object from different perspectives (tumble, pan, zoom, etc.)
- View sections of the object (clipping, cross sections on arbitrary planes, etc.)
- Vary transparency or opacity (depth-dependent, etc.)
- Pick or select voxels.

## IV. (Contributed by Andrew Reid)

## Slide 19

## Slide 20

## The end. Thank you.