Chassis - Fluid Structure Interaction

One of the initial iterations of the chassis design is shown above. It has 4 longerons with ribs placed in the front, middle and the back of the pod. Supports are adequately provided on the front and back as well. The weight of this design was 70.23 kg.

Stresses generated in the chassis due to pressure distribution of fluid on the pod and uniformly distributed load of different systems of the pod are calculated through ANSYS Workbench. The resultant deformation is shown in the figure above.

The analysis of the frame yields a maximum deformation of 1.8 mm. The factor of safety achieved is 3.5, which is very promising. The weight of the chassis is high and could be reduced without compromising structural integrity. Additionally, it was necessary to add more support elements at certain locations and remove support elements from others to obtain a more optimized chassis design.

The new design had a weight of 57 kg which is a reduction of 20% from first design shown.

Design 2 gave us a factor of safety of 2.68 and a maximum deformation of 2.4 mm. Weight could further be reduced by strategically reducing material from certain locations.

The new design had material removed at strategic locations in the base plate. The weight of the new chassis frame was 40 kg which was 43% weight reduction from the 1st design and 30% when compared to design 2.

The factor of safety of this design turned out to be 2.26. This was still a good factor of safety and it had the added benefit of being very light in weight. The next step would be to conduct stress analysis due to acceleration and deceleration of the pod on this frame.

Under an initial acceleration of 18.62 m/s2, the pod’s frame experiences a maximum Von Mises Stress of 55.18 MPa, resulting in a factor of safety of 5 relative to the yield strength of Al6061-T6. Whereas under a nominal deceleration of 21.19 m/s2, the pod’s primary structure experiences a maximum Von Mises Stress of 62.79 MPa, resulting in a factor of safety of 4.4 relative to the yield strength of Al6061-T6.

Some advantage of this design:

• Strong frame with factor of safety of 2.26 and anoptimized low weight design of 40 kg

• Provides support for the carbon fiber shell at strategic locations

• Designed in a way that makes it very easy to inspect, replace or repair components

• Modular design

• Easy and economical to manufacture