Development of a nano-satellite micro-coupling mechanism with characterization of a shape memory alloy interference joint

Abstract

This thesis describes the design, development, and testing of an innovative nonexplosive actuator (NEA) microcoupling device. The micro-coupling is obtained through the use of a nickel titanium (NiTi), shape memory alloy (SMA) cylindrical ring that is press-fit, in its detwinned martensitic phase, into a steel bushing, creating an interference joint. This SMA interference joint can subsequently decouple upon command, by heating the SMA cylindrical ring into its smaller austenitic memory shape, freeing it from its press-fit. The micro-coupling can be engineered to very small sizes, on the order of one cubic centimeter, and achieve coupling strengths in excess of 4,000 N (900 lbf). The SMA micro coupling's concept validation, mechanization, and development into a device for satellite incorporation are explored by assembly and experimentation. Research on pseudoelastic material properties, analytical predictions, and tests of coupling strengths are examined to characterize the SMA micro-coupling. While the micro-coupling's characteristics are desirable for many applications, its small size, simple interface, and lowpower zero-shock actuation are ideal for employment on nano-satellites to effectively increase space deployable actuation reliability by eliminating reliance on motors, clasps, latches, material fracture, or explosive devices.