Dr. Andres Tovar is an assistant professor at Indiana University-Purdue University Indianapolis (IUPUI), and recently won ARPA-E’s LITECAR challenge with a ribcage-inspired design. We asked him a few questions about design, 3D-printing and bones.
1. How did you become interested in vehicle design?
Every kid, at some point, dreams about making robots, spacecraft or cars. Cars were what I wanted to learn about: why they work and how they function. And that’s one of the biggest reasons I studied mechanical engineering. It was during my Ph.D. studies when I became very interested in designing vehicle structures.
I just had the idea, and that was over 10 years ago, that I could develop computational bone remodeling algorithms that can simulate the way bones adapt to the mechanical stimulus, and then use those algorithms to design vehicle structures so they would be strong and lightweight -- like bones -- and also energy absorbing.
2. What inspired your winning design?
I’ve been working on designing vehicle components for crashworthiness for several years. I’ve worked on components such as bumpers, head-shock absorbers, and knee bolsters. So my work has been focused on vehicle component design. This challenge gave me the opportunity to explore the design of a full vehicle structure, which was something that I had had in my mind but did not pursue until now.
In this design, I thought that I could use the way the human body is protected to make a safe vehicle. Actually, this is an idea that I’ve been developing for several years, but my funded research projects had to address more immediate problems at the component level.
So this contest gave me the opportunity to explore designing a full vehicle structure using a multi-scale design approach. In the vehicle scale the computer algorithm predicts the layout of the bones -- like a ribcage -- while in the component scale the computer algorithm predicts the component’s internal structure, like a bone.
The overall shape of the vehicle like a water droplet, which is known to have a low drag coefficient. The resulting structure is shaped like a water droplet with a protective ribcage-like structure.
3. How did your students help with the design?
There were four students involved in this project: three Master’s and one Ph.D. student. Prathamesh Chaudhari, a Master’s student, worked on Computer Aided Design -- or CAD -- creating an initial droplet shape and the final files to be read by the judges. Our design algorithms worked with data in the form of large matrices, so it was important to have a student with good CAD skills to generate the files that were ultimately submitted.
Nishanth Bhimireddy, another Master’s student, worked on crash simulations. We wanted to make sure that the vehicle structure could withstand standard crash tests -- frontal impact, lateral impact -- with different offsets.
Kai Liu, the Ph.D. student, worked on the design algorithms. I have been working with Kai for over two years in design for crashworthiness. He is currently supported by Honda R&D Americas and worked very closely with me on the optimization of the vehicle. Together, we maintain the in-house design algorithms used in my research group.
Fabian Lischke, the third Master’s student, worked on the Additive Manufacturing of the final design, making sure that the design was 3D-printable. We 3D-printed many of our conceptual designs just to make sure that they were manufacturable. We 3D-printed the scaled vehicle as well as some components -- the porous components that look like bones inside. We wanted to pay attention to those details.
4. How long did the design process take?
About four months. We received the first invitation to compete in November 2014. In the following four months we customized our computer algorithms, developed the conceptual design and performed crash simulations. The final design was submitted in March 2015.
5. What was the most difficult aspect of designing your entry?
There were a couple of difficult aspects. One was the crash simulations. The structures we designed are complex. The components have a solid phase, but they also have a graded porous phase. To capture those features the computational models become expensive and, in many cases, we were unable to complete the simulations before the deadline.
Another difficult aspect was translating between various format files: CAD, simulation, optimization and 3D-printed. Several hours were devoted to manually cleaning and correcting to make sure the design worked in different formats.
6. How does your work at IUPUI relate to this challenge?
A significant part of my research is in crashworthiness. More generally, I research lightweight design and energy absorption. I design algorithms so the computer can help us find the optimal material structures that are lightweight and energy absorbing. My lab has physical testing capabilities, so we can verify if our designs can absorb energy as predicted by our computer simulations.
7. What does winning the competition mean to you?
This is an outstanding recognition. To be recognized for my research is really motivating. It is rewarding to know that my research in lightweight and safety has real high societal impact and it is being recognized.
8. What advice do you have for aspiring vehicle engineers?
No limitations: when you want to design something there should, in principle, be no limitations of any kind. If it looks a little bit crazy, then good! Trust your feelings, put it together, and create the things that you’re convinced of.
Just take the risk!