Fatigue life characterization of shape memory alloys undergoing thermomechanical cyclic loading
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This paper presents a study on the fatigue life of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation under various stress levels. A microstructural study characterizing specific damage patterns is conducted. Formation of different types of microcracks has been observed, showing a superficial micro cracking, at the origin of the growth of circular cracks which are finally responsible for localizing the failure of the specimens. Interactions between the micro cracking pattern and the corrosion occurrence are also studied. A spallation oxidation occurring at the surface of the actuator, which damages its properties, is put to evidence. The failure pattern observed provides information necessary to introduce a correction to the classical Wohler curve for fatigue life of a SMA material undergoing cyclic loading.
name of conference
Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics