Browsing by Author "Wehmeyer, Geoffrey"

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    Passive Magnetic Heat Switch for Thermal Management of Lunar Spacecraft
    (2022-12-01) Garg, Ajay A; Wehmeyer, Geoffrey
    This thesis discusses our design of the Passive Magnetic Heat Switch (PMHS). This project, funded by NASA, looks for new, low TRL heat switches for Lunar Rover applications. The novelty of the PMHS is its ability to switch near room temperature by using temperature dependent magnets. The PMHS is a gap closure heat switch where the ON state mates highly polished copper surfaces and the OFF state de-mates the surfaces. We use commercial neodymium magnets to close the gap in the ON state and gadolinium, which has a Curie temperature of 20 °C, to achieve the OFF state. All experiments were performed under high vacuum and reasonably agree with our FEA models. The PMHS turns ON at 28.5 °C and turns OFF at 15.5 °C. The ON and OFF state conductances, are 0.153 WK-1 and 0.0099 WK-1 respectively. The switch ratio, which is the figure of merit for all heat switches, is 15.5:1.
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    Programmable failure of heat-sealable textiles for soft robotics
    (2024-04-19) Broshkevitch, Adam Teofil; Preston, Daniel J; Wehmeyer, Geoffrey
    While mechanisms are often designed for compliance or controllability, heat-sealable textiles (HSTs) can be bonded to form fluidic networks which operate within both constraints. I examined failure in HST systems, clarifying the effects of processing parameters on seal strength and relating pouch geometry to burst pressure. My findings can be leveraged to ensure a HST soft robot or device is sufficiently robust for a given use case. I also present a soft fluidic component, analogous to an electrical crowbar circuit, into which failure is deliberately programmed. When integrated into a fluidic network, the component can be used to limit damage in cases of overpressure or to achieve multiple modes of actuation with a single pressure input. Operation is triggered by signals on the order of 1 to 3 bars. In summary, my findings enable the design of more intelligent and resilient HST systems, broadening their application space.