Thermomechanical cyclic loading and fatigue life characterization of nickel rich NiTi shape-memory alloy actuators

Olivier W. Bertacchini; Dimitris C. Lagoudas; Frederick T. Calkins; James H. Mabe

doi:10.1117/12.776502

3 April 2008 Thermomechanical cyclic loading and fatigue life characterization of nickel rich NiTi shape-memory alloy actuators

Olivier W. Bertacchini, Dimitris C. Lagoudas, Frederick T. Calkins, James H. Mabe

Author Affiliations +

Proceedings Volume 6929, Behavior and Mechanics of Multifunctional and Composite Materials 2008; 692916 (2008) https://doi.org/10.1117/12.776502
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2008, San Diego, California, United States

Abstract

Within the last decade, the development of compact SMA actuators has led to the design of smart structures such as the Variable Geometry Chevron (VGC), designed by Boeing engineers. The chevrons are aerodynamic devices actuated by SMA beam actuators and placed along the trailing edge of a jet engine to provide noise reduction. The SMA actuators are clamped on an elastic substrate that provides a biasing force allowing repeated one-way shape memory effect under cyclic thermal actuation. In this work, a comprehensive characterization of thermally induced fatigue behavior of nickel-rich NiTi SMA actuators subject to different constant applied stresses is presented. The influence of various parameters is studied in order to assess the fatigue behavior of nickel-rich NiTi, namely: two heat treatments, two heat treatment environments, three fatigue test specimen thicknesses and four stress levels. The purpose of this thermomechanical fatigue study is to evaluate the shape recovery stability, the influence of large applied stresses, the amount of permanent deformation and the resulting failure mechanisms. Fatigue limits of ~ 5,000 to ~ 60,000 cycles were found for applied stress levels ranging from 250 MPa to 100 MPa.

Citation Download Citation

Olivier W. Bertacchini, Dimitris C. Lagoudas, Frederick T. Calkins, and James H. Mabe "Thermomechanical cyclic loading and fatigue life characterization of nickel rich NiTi shape-memory alloy actuators", Proc. SPIE 6929, Behavior and Mechanics of Multifunctional and Composite Materials 2008, 692916 (3 April 2008); https://doi.org/10.1117/12.776502

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