• Smart Structures and Systems
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• 제21권3호
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• pp.257-262
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• 2018

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.

• 한국안전학회지
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• 제19권4호
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• pp.1-7
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• 2004

This study investigated the effects of aging on the transformation behavior of $Ti-50.1at\%$ Ni alloy by means of differential scanning calorimetry. It was found that aging in the temperature range of $350^{\circ}C\~550^{\circ}C$ induced complex transformation behavior, involving the R-phase and multiple-stage martensitic transformation. Usually aged Ni-rich NiTi alloys undergo martensitic transformation on cooling from high temperatures in two step : B2 to R and then R to Bl9'(normal behavior). But under certain ageing conditions, the transformation can also occur in three or more step(unusual multiple step behavior). In the present study we use differential seaming calorimetry(DSC) for a systematic investigation of the evolution of transformation behavior with ageing temperature and time.

• 항공우주시스템공학회지
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• 제18권4호
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• pp.81-88
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• 2024

차세대 중형위성 3호의 탑재체 중 바이오캐비넷은 우주공간에서 바이오 3D프린팅 기법을 이용한 3차원 줄기세포 분화, 배양 및 분석 임무를 수행한다. 상기 3D 프린팅 기법은 궤도환경에서 사용을 목적으로 개발되었으나, 극심한 발사환경에 대한 별도의 검증이 이루어지지 않아 탑재체에 전달되는 발사하중을 저감 시키는 설계가 필수적이다. 본 논문에서는 바이오캐비넷에 전달되는 발사하중 저감을 위해 저강성 탄성 지지구조 적용 및 고댐핑 특성을 부여한 수동형 진동절연기를 제안하였으며, 고댐핑 특성을 부여하기 위해서 초탄성 형상기억합금의 초탄성 효과와 점탄성 테이프를 이용한 적층형 구조에 주목하였다. 제안한 진동절연기 인증모델에 대한 발사진동시험을 통해 설계유효성을 검증하였다.