Octet Truss for Topology Optimization

Random Octet Truss Array (on shapeways)

This post demonstrate a work-flow for topology optimization using open source tools (with mixed success). The approach uses an unpenalized method (see wiki) that maps the material density output from the optimizer to unit-cells based on the octet truss (inspired by this white paper, see pp10). As some further motivation for this approach, the students working on the record-setting human powered helicopter demonstrated that multi-scale trusses (trusses with elements made of smaller trusses) were a very efficient structural concept (see the comments for further references on multi-scale structures). One of the benefits of not penalizing (using variable density solutions rather than trying to achieve predominantly solid-void solutions) is that we don't need to spend time doing parameter continuation on the penalization exponent.

Interesting Developments in the Numerical Python World

From Travis Oliphant by way of the Planet Scipy feed:

Hello all,

There is a lot happening in my life right now and I am spread quite thin among the various projects that I take an interest in. In particular, I am thrilled to publicly announce on this list that Continuum Analytics has received DARPA funding (to the tune of at least $3 million) for Blaze, Numba, and Bokeh which we are writing to take NumPy, SciPy, and visualization into the domain of very large data sets. This is part of the XDATA program, and I will be taking an active role in it. You can read more about Blaze here: http://blaze.pydata.org. You can read more about XDATA here: http://www.darpa.mil/Our_Work/I2O/Programs/XDATA.aspx

I personally think Blaze is the future of array-oriented computing in Python...

Passing the torch of NumPy and moving on to Blaze

Open Source Topology Optimization for 3D Printing

Rough Hex Output & Smooth Surface Reconstruction for Dogleg

This post describes a set of open source tools for simple topology optimization for parts destined for 3D printing. The two Matlab codes (both are plain vanilla Matlab, so they work successfully in Octave too) are good introductions to topology optimization. The papers that go along with the codes provide great documentation and examples of tweaking and changing the scripts to treat various problems. The python implementation is more capable (and a few more lines of code).

Fedora BRL-CAD Compile Notes

I have not had good luck with the Boolean operations in FreeCAD as I had hoped (seems to be a problem with the underlying OpenCascade libraries) so I am compiling BRL-CAD.

F-35A GBU-31 Safe Sep Video

Nice separation video near the end; bearably cheesy at the beginning.

OpenFoam on Google Compute Engine

I signed up for the free preview of Google Compute Engine. The project I described in their questionaire was basically just some hobby-level CFD stuff, so I am surprised they sent me an invite. This post provides links to the initial setup documentation and getting started tutorials, and describes getting OpenFoam up and running on an instance.

• GCE Hello World
  
• gcutil Tool Install
  
• Overview
• Instances
• Networking, Firewall
• Disks
• Images

Falcon 9 Flight 4, CRS-1

Congratulations to SpaceX on their successful launch of the first commercial resupply mission to the International Space Station!

DMLS Wind Tunnel Models

Additive manufacturing, sometimes called direct digital fabrication or rapid prototyping, has been in the news quite a bit lately. I wrote a post recently for Dayton Diode about the many additive manufacturing options available for fabricating functional parts or tooling in response to comments on a piece in the Economist, and commented recently on Armed and Dangerous in a discussion about 3D printed handguns. There are just so many exciting processes and materials available for direct digital parts production today. Some of the work I've been doing recently to qualify one particular additive process for fabricating high-speed wind-tunnel models (abstract) was accepted for presentation at next year's Aerospace Sciences Meeting.

We used Direct Metal Laser Sintering (DMLS) to fabricate some proof-of-concept models in 17-4 stainless steel. DMLS is a trade name for the selective laser melting process developed by EOS. The neat thing about DMLS (and additive processes in general) is that complicated internal features like pressure tap lines can be printed in a single-piece model. Being able to reduce the parts count on a model to one while incorporating 20 or so instrumentation lines (limited only by the base area of our particular model) is really great, because one part is much faster and less expensive to design and fabricate than a multi-component model with complicated internal plumbing. The folks down at AEDC are also exploring the use of DMLS to fabricate tunnel force and moment balances for much the same reason we like it for models and others like it for injection mold tooling: intricate internal passages, in their case, for instrumentation cooling and wiring.

FreeCAD on Fedora

UpAerospace 10 inch Payload Can (PTS10)

There seems to be a great deal of difficulty (brlcad, opencascade) in getting any of the open source CAD programs incorporated into the Linux distributions that maintain high standards on acceptable license terms and packaging guidelines (Fedora). Luckily, for a pragmatic guy like me I can now install FreeCAD from the RPMFusion non-free repos.

yum install freecad

I'm excited to see if I can get better Boolean operation results (less manual mesh fixing) with FreeCAD for 3D printing than I've had with Blender.