Non-Explosive Venting Devices based on a Novel Shape Memory Alloy Reverse Tension-to-Compression Mechanism

A non-explosive (or non-pyrotechnic) device for venting applications was developed using a Shape Memory Alloy Reverse Tensile Rod Actuation Mechanism (SMART-RAM). The actuating elements consist of helical machined springs trained in tension, which compress under thermal loading, and result in the release of a puncture pin to perforate or impart a crack on a contacting surface. The use of machined helical springs allows for large actuation displacement and large blocking force output to penetrate hard metal objects or other materials. To help direct the force towards the article, an SMA shrink ring was used to hold the device and act as a backing constraint during actuation. The device employed an SMA based on a NiTiHf formulation with Hf content between 15 and 18 at.% Hf. The alloy was precipitate hardened to increase stability and strength and was designed with aid from NASA’s Shape Memory Materials Analysis and Research Tool (SM²ART) to significantly reduce alloy selection time while adhering to specific constraints. In its current form, a single device is capable of blocking forces over 2000 N and actuations in excess of 12 mm, which could be scaled further to provide additional blocking forces and actuation displacements. An overview of the device development, SMA property tuning, and prototype implementation is presented.