Student Post: Project Timeline for Structural Refinement to Counter Application of Forces

Dear Reader,

The sphere packing software currently generates 3D internal structural meshes for hollow 3D objects. However, our current usage of sphere packing does not provide a major improvement over simple manual generation of uniform truss structures. The true advantage to using sphere packing is actually the ability to selectively manipulate local regions of the internal structure. Of course, a human engineer could manually design a complex structure with desirable properties in specific parts of a 3D object, but this is time consuming. My current goal is to create software that can automate or aid a human in this process.

In order to take advantage of sphere packing’s capability, I am moving the project to the next phase. I’ve been doing research on stress in mechanical engineering to gain a better understanding of how structures are designed to counter or use stress. Unfortunately as far as my novice eyes can see, it seems that the structures generally do not involve complex 3D graphs. Also there’s a large amount of information on how to calculate stresses on objects, but there is much less information on how to augment structures to counter stress besides using varying materials.

Regardless, I am going to perform an experiment to determine if I can structurally augment 3D meshes to resist stress forces, specifically compression, tension, and shear.

Image result for stress mechanics

In the first phase, the inputs are the STL file of a 3D object and the sphere packing parameters. The output was a 3D graph that served as the internal mesh of the object. In the second phase, the input will be the 3D graph and data describing forces applied to each vertex of the graph. The output will be an altered graph that should resist the forces better.

To obtain the forces applied to each vertex of the graph, I will convert the graph to solid form as a STL file and use a finite element analysis tool that will enable a user to selectively apply forces to the entire object. I am thinking of using an FEM module for FreeCAD; although I have yet to explore the capabilities of the module.

Image result for finite element analysis freecad

Next, I will add functionality to the sphere packing software where the vertex forces data can be used to refine the graph. The specific refinement scheme still needs to be resolved, but I do have an idea that I am going to implement. I will explain in greater details once the implementation is complete, but the general idea is based off of cell growth in biology where in my case the cells are spheres. This is based on the assumption that a dense graph can withstand more stress than a sparse graph. Think of osteoporosis for example:

Image result for osteoporosis

Once the refined graph for the original object has been generated, I will conduct physical tests to determine its structural limits. I will conduct the same tests on the unrefined graph, the full solid object, and a hollow shell of the object as controls.

To keep myself on track I present my Timeline:

March 27th, 2017 – Find and utilize suitable software for simulation of forces on 3D objects to calculate forces on specific nodes of a graph.

April 7th, 2017 – Finish implementation of refinement functionality in sphere packing.

April 14th, 2017 – Finish designing experimental structures and print as objects for testing.

April 21st, 2017 – Complete physical stress tests on objects.

April 24th, 2017 – Write up report on experiment.

I shall keep you posted on progress.

Thanks for reading,

-Xiang

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