A CASMART Review of Multifunctional Shape Memory Alloy Elements

Shape memory alloys (SMA) are having a significant impact on numerous fields, such as biomedical, aerospace, electronical, robotics, industrial, construction, automotive, and many others. Applications such as actuators, stents, solar panels, dampers, jet engine parts, valves, dental implants and others take advantage of the materials ability to undergo a reversible phase transformation that results in a wide range of controllable material properties. These controllable material properties enable SMA elements to have unique capabilities, identified as functions, that they perform as part of a system supporting the application requirements. Some of the well-known functions include shape change motion, sensing, structural support, mechanical energy dissipation, energy transfer, and surface tribology.  SMA elements are uniquely multifunctional in the sense that one element can fill multiple functions required by the system.  While a conventional system combines multiple elements to perform these functions, taking advantage of multifunctional capabilities inherent in SMA leads to increased value through reduced parts, weight, complexity, and improved integration.  This paper classifies the multifunctional capabilities of shape memory alloys useful for a broad range of applications and provides example case studies showing where and how the multifunctionality of SMAs has been utilized.