Dr. Santo Padula II received his PhD in Materials Science and Engineering from Michigan Technological University and has worked full-time at the NASA Glenn Research Center for 18 years. Dr. Padula has focused his career on developing test techniques to support advanced material development. He has conducted research activities in a broad range of areas including fatigue of superalloys, impact behavior of lattice block structures, and metallic foam concepts and mechanical response of high temperature shape memory alloys and devices. His forte has been on incorporating novel measurement techniques to permit the determination of data under complicated thermomechanical loading conditions. His advancements in this area have contributed to the development of one-of-a-kind constitutive models for new materials with unusual behaviors. Most recently, Dr. Padula has begun utilizing his vast expertise in the field of Shape Memory Alloys (SMAs) to patent numerous technologies that are revolutionizing the field. His work has led to the receipt of 2 R&D 100 awards (Top 100 Inventions of the Year – Oscar’s of Innovation) and numerous opportunities to collaborate with outside commercial entities. His work on non-pneumatic tires using SMAs has led to a breakthrough in the field and is positioned to be the new baseline for future rover technologies for the Agency.
Shape Memory Alloy (SMA) materials are a new class of metals that are energetically different than conventional metallic compounds. This energetic difference gives them a unique deformation mode — what is referred to as a transient “twinning” process. Thus, these materials undergo a solid-state phase transformation that allows us to manipulate the atomic structure of the metal merely by manipulating the way that we either mechanically load or thermally load the material. Hence, depending on the way the material is initially fabricated, it’s possible to use mechanical loading and unloading or heating and cooling to create large deformations that are fully recoverable. This opens a new paradigm in design whereby large shape changes in the component can be achieved and used to reshape the way we think about design.
The utilization of this new processing methodology gives us the ability to very quickly produce stable materials that can be used for structural components and actuation systems. To be able to now use a simple piece of material — let’s say a tube — to completely replace an entire hydraulic system on an aircraft is revolutionary. We’ve actually done demonstrations with Boeing on its 737 aircraft. We’ve flown that plane under aero loads just by heating and cooling a tube, instead of having massive hydraulic actuators, lines, fluids, and pumps, which are very heavy and cost more fuel burn. We’re able to use technologies, like the ones being developed, to create quality and stable materials that now can begin to replace systems on aircraft that make it cheaper and more efficient to fly.
The automotive sector is already using these materials. In fact, almost every lumbar support system in vehicles now is actually SMA-driven, usually using SMA wires as the actuation component. At NASA, we are developing new adaptive technologies for large-scale aircraft in the aeronautics world in order to replace flap elements and control surfaces on wings with more lightweight, compact, and efficient systems. These materials work for pretty much anything that is actuation-based.
Shape memory alloys have been heavily used for decades in the biomedical field — everything from catheter tubes to arterial stents. These materials, because of the uniqueness of the solid-state phase transformation, allow us to do similar kinds of applications. We can send a femoral catheter from just inside your groin and snake it all the way to your heart without kinking or the risk of not being able to get it back out. We also have recently developed a new, non-pneumatic tire technology that is needed for improving the performance and durability of our space rover applications. A version of this technology has also been demonstrated on a commercial Jeep vehicle where it performed exceptionally. Hence, these unique materials look extremely promising in revolutionizing the entire terrestrial tire industry, and that’s just the tip of the iceberg.
We're trying to continue to advance the science of this area so that people can begin to see that there’s another alternative to the conventional metal systems. Once we get to that point, we'll be at a place where the design will truly be a paradigm shift.
I would like to say that this was a team effort. I have some of the best analytical minds working with me, and this application would not have been successful without my team.
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For additional information on this technology, please visit: https://technology.nasa.gov/t2media/tops/pdf/LEW-TOPS-32.pdf