Design by Volume, Mass and Load

Published 2013-11-25
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"Topology Optimization" is the formal term for the technology that allows you to say to the computer: "Take this chunk of material, with all these different loads and take all the unnecessary material away".

Optimization image_2

(image courtesy of MSC Software)

Have you ever wondered how car manufacturers manage, with every new car model, to make the cars lighter and yet stronger? Topology Optimization! Lighter cars means less unnecessary mass to transport which means less fuel to burn and more power available to accelerate you.

To use topology optimization is a very simple process if you are familiar with Finite Element Analysis (FEA) and have access to Nastran with it's optimization capabilities.

In this video tutorial: http://www.youtube.com/watch?v=IxqV2bFM6bU, detailed steps are provided to use Patran and Nastran to use topology optimization to do exactly this.

Let me give you an example: If you need to design a bridge, but have certain height, width and depth restrictions, Nastran is the perfect tool to help you design the actual framework within those constraints.

The following image shows the design domain of the potential new bridge:

Topo_1

This image (above) shows the allowable areas of where structural members may be without any regard to their shape or design (within that space). Furthermore it is important to add all the possible loads that may be applied to this brige. This include loads due to traffic and even own weight and wind loads. You can also include seismic loads if required. Nastran can take all these requirements into account. It could be devastating if you neglect any single load case that is important.

The next image shows the end result after specifying that a large percentage of mass (you specify how much) needs to be removed.

Topo_2Topo_3

The dark coloured elements shows the most important elements and give you an idea of the ideal shape for the main structural members. No elements are actually removed from the analysis but their importance are displayed by the darkness of their colour and elements below a certain importance can be hidden from view as was done in these images.

Now in reality, large structures or components can't (yet) be 3D printed which means we might need to consider additional constraints such as minimum member size, symmetry requirements, extrusion (constant through section) constraints etc.

In the following images the same analysis was simplified by specifying three different manufacturing constraints for various areas of the design domain which resulted in a more feasible design from a manufacturing point of view:

Topo_5 Topo_4

The next step is to use this information and create a new design following the gained knowledge and complete a normal analysis of the structure under the various loads to ensure it is still capable of fulfilling its function.

The use of this technology holds huge potential for mass producers and end users alike.

Savings in construction material means cheaper products which means higher revenue and/or larger market share.

Lighter products means lower running costs for end users and in the case of the transport industry, means more loading capacity for the same axle loads. Imagine a truck, trailer or rail wagon weighing 1 ton less? It equates to lower fuel consumption when running empty and an extra ton of material/goods that it can carry under the same legal limits.

Other applications are crates for transporting smaller goods or automotive parts like this example where a given design space was used and only the required material remained:

Optimization process

(image courtesy of MSC Software)

You can read more about Topology Optimization here.

There are other similar technologies available such as Topography optimization and Topometry optimization. Topography optimization takes a plate and move nodes out of plane to create punch patterns that stiffens the plate (without adding or removing material) and Topometry optimization changes the thickness of individual elements on a shell structure.

This presentation shows how these various optimization techniques are used at AUDI to continually reduce mass and reduce vibration in their new passenger vehicles.

Are you a MSC Masterkey client? Then you already have access to these optimization technologies. To know more, contact us at support@simteq.co.za and use "Patran Topology Optimization" in your subject line to have your question routed quickly to the correct person.

You may also be interested in reading the follow up article Doing Topology Optimization right which links to 7 new "How to" pages related to topology optimization.

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