GE & GRABCAD Challenge
Introduction (qui per la versione Italiana)
BONE 414 is a project conceived for the GE Jet Engine Bracket Challenge.
The component that has been redesigned is a bracket used during some specific moments of the maintenance of the jet engine, but it is a component that stays on the airplane at all times.
For this reason the challenge was focused on lightness. The results had to pass several FEA tests, to ensure that the bracket was able to hold up the weight of the engine. Constraints and forces were given, and the bracket had to fit in the original part envelope, using the same anchor points. (Picture 1)
The project starts form an idea, an intuition, that forces should shape the bracket to optimize resistance and weight. From this principle we started to work on a concept called mesh relaxation (Grasshopper and Kangaroo) which allowed us to get a first design that has been modified afterwards.
The basic principle of mesh relaxation systems is to simulate the behavior of springs. Relating every mesh edge to a spring, and applying a stress, the system will try to distribute the forces, creating a balance in the design. In other words, every spring will react with the nearly springs, with an opposite and equal strength, pulling the all system into balance.
This basic principle is able to generate geometries which optimize the distribution and spacing of the faces, creating very natural, organic and very performing shapes.
The first step is realized with the mesh tools of Rhino3D. (Picture 2)
In this part we want to create a mesh that comes close to the final object. The mesh must have enough faces to allow to get a smooth result. This subdivision is critical, as it defines the ability of the mesh to relax. (Picture 3)
In this specific project we started form the anchor rings of the original part. This choice was dictated from the necessity to have precise references to which we had to anchor the bracket, so we could stick to the original part envelope
Switching to Grasshopper and Kangaroo
Inside Grasshopper we need to have a plug-in called Kangaroo, which allows you to simulate physics and also elastic systems.
In picture 5 you can see the simple algorithm that allows you to relax the meshes. It is composed form 3 main parts:
- The physics engine
- The mesh to be relaxed
- The edges of the mesh to be kept fixed
The physics engine, a component of Kangaroo, is the heart of the system, that needs to know the forces that will act during the simulation. The physic engine is an iterative component, which acts in function of time, and generates a solution that updates and improves until the best result.
La mesh da rilassare that needs to be relaxed is the item on which we will work but, before to be processed, we need to extract all the edges that compose the mesh. Every edge will be converted to a line, and every line to a spring.
Some edges of the mesh, mostly the ones that are open, can be maintained fixed, and they will act as anchor edges which will not be relaxed, but they have great influence on the final result.
The mesh before relaxation:
The mesh after relaxation:
The mesh relaxation creates a contraction of the geometry which tends to reach the tangent lines of anchor points. This shape will probably able to distribute the stress with the lower volume and therefor material.
The optimization techniques are still at their beginnings, but this system promise to give reasonable results with a good accuracy and in short time. Down here you can see the final mesh. (Picture 8)
T-Splines, or form Mesh to Nurbs in just a click.
The mesh that has been obtained could already be fit for production, but to get a smoother and better result we have decided to edit the mesh using T-splines for Rhino.
La mesh può essere convertita da T_Splines in una polisuperficie nurbs in due semplici passaggi: da mesh a TS e poi da TS a nurbs.
The mesh can be converted from T-splines to Rhino Nurbs in two simple steps: from mesh to TS and from TS to a Nurbs polysurface. Through T-Splines is possible to generate a very smooth surface and it is also possible to edit the mesh in order to create rims, holes or any other feature without breaking the tangency of the surface.
Once you have the Rhino3D polisurface, it is possible to generate other features, like holes and extrusion to get planar surfaces. (Picture 9)
More information about the challenge: