Autori: Marius-Gabriel SURU, Adrian-Liviu Paraschiv, Nicoleta Monica Lohan, Bogdan Pricop, Burak Ozkal, and Leandru-Gheorghe Bujoreanu
Editorial: Journal of Materials Engineering and Performance, Vol. 23, no. 7, p.2669-2676, 2014.
The present work reports the influence of the loading mode provided during training under constant stress,
in bending, applied to lamellar specimens of Cu-Zn-Al shape memory alloys (SMAs). During training, the
specimens were bent by a load fastened at their free end, while being martensitic at room temperature and
they lifted the load by one-way effect (1WE), during heating up to austenitic field. On cooling to martensite
field, the lower concave surface of bent specimens was compressed, and during heating it was elongated,
being subjected to a series of tension-compression cycles, during heating-cooling, respectively. Conversely,
the upper convex surface of bent specimens was elongated during cooling and compressed during heating,
being subjected to compression-tension cycles. Furthermore, 2WE-trained actuators were tested by means
of a hydraulic installation where, this time heating-cooling cycles were performed in oil conditions. Considering
that the lower concave surface of the specimens was kept in compressed state, while the upper
convex surface was kept in elongated state, the study reveals the influence of the two loading modes and
environments on the width of martensite plates of the specimens trained under various numbers of cycles.
In this purpose, Cu-Zn-Al specimens, trained under 100-300-500 cycles, were prepared and analyzed by
atomic force microscopy (AFM) as well as optical and scanning electron microscopy (OM and SEM,
respectively). The analysis also included AFM micrographs corroborated with statistical evaluations in
order to reveal the effects of loading mode (tension or compression) in different environmental conditions of
the specimens, on the surface profile characteristics of martensite plates, revealed by electropolishing.
Cuvinte cheie: cycling environment, loading mode, martensite plates, shape memory alloys, surface profile characteristics