A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumdated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation fitnctions, by inhercEtly s e x k g a c h m ~ c ia temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic S,MAs are addressed here. First a shape memory alloy based cryogenic thermal conduction swtch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed. Shape memory alloys (SMAs) when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as the shape memory effect. Thus SLMA~ are a‘unique class of alloys that “remember” and return to their original shape due to a themally-induced phase transformation, following deformation. The strain recovery can occur against large forces, resulting in their use as actuafors [ 1-41. This principle is schematically shown in FIGURE https://ntrs.nasa.gov/search.jsp?R=20050061121 2017-09-13T23:02:45+00:00Z