Şekil hafıza alaşımlı zıt çalışan eyleyicili aktif eklemlerin geliştirilmesi

The focus of this research work is the development of an active joint antagonistically actuated by shape memory alloys (SMA). Due to their high force to mass ratio these identified as excellent actuator candidates for biomedical, robotic, aerospace and automotive applications. Specifically, NiTi alloys attract attention because of their unique features such as relatively high transformation temperature and recoverability of strain values up to 8%. This study is intended to exhibit the development of antagonistically actuated active joints supported by a thorough understanding of their behavior. Cyclic tests of the active joint have been conducted at various angle amplitudes. The results showed that number of cycles to failure considerably reduced by an increase in the target angle amplitude such that actuation ceases over 100º. It was found that higher peak temperatures of the actuator elements were needed to reach the same bending angle within the subsequent cycles. This observation was attributed to possible increased localized deformation around the martensite plates resisting phase transformation. It was also seen that in resting stages between the actuation durations of opposing elements, a reverse deformation takes place, which remarkably rose with the increase in cycle numbers. This observation was linked with elevated stress levels and the increased resistance by the antagonist actuator, resulting in the greater peak temperature in consecutive cycles. Further investigations also provide a gradually ascending trend of transformation temperatures and stress hysteresis as implication of the cyclic response.