AN INVESTIGATION OF CONCENTRATED AND DISTRIBUTED STRAIN INDUCING CONSTRAINTS FOR TRAINING SHAPE MEMORY ALLOYS

Abstract

This research explores concentrated and distributed strain inducing constraints for Two Way Shape Memory (TWSM) training of cantilevered NiTiNOL shape memory alloy strips via the constrained thermal cycling of deformed Martensite training method. The goal is to evaluate the performance of a tip-moment trained sample actuator, which is characterized by constant strain along the sample length, and compare it with the performance of tip-force trained sample actuators, which have root concentrated strain. The shape and net tip displacement of trained specimens is expected to vary with training constraint type and training load magnitude, rendering it uncertain which sample will have greater work potential. A training structure and systems for introducing thermal and mechanical loads were developed to provide the explored training constraints and induce TWSM. The work performance was evaluated by measuring vertical displacement of tip weights. The experimental results indicate that samples subject to strain distributing constraints during training have higher work potential than samples subject to concentrated strain inducing constraints.