• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.30-33
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• 2009

본 논문에서는 형상기억합금의 특징적인 거동을 모사하기위한 구성방정식을 제안한다. 제안되는 구성방정식은 기존의 소성모델을 기초로 하는 현상학적인 모델로, 소성 경화이론에서 사용되는 항복곡면에 대응되는 상변이 곡면을 정의하여 형상기억합금의 비선형 거동을 모사한다. 단, 상변이 곡면이 1개만 존재하는 소성모델과는 다르게, 오스테나이트에서 마르텐사이트로의 정방향 상변이와 마르텐사이트에서 오스테나이트로의 역방향 상변이를 각각 해석하기위해 독립적인 2개의 상변이 곡면을 정의해주게 된다. 기계적 하중만이 아닌 열적 하중의 변화에도 비선형 거동을 보이는 형상기억합금의 특성을 반영하기위해 상변이 곡면은 응력과 온도의 함수로 정의되며, 이렇게 정의된 상변이 곡면을 바탕으로 리턴 매핑 알고리즘을 적용하여 열적하중과 기계적하중의 변화에 따른 형상기억합금의 거동을 모사하는 구성방정식을 제안하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.916-921
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• 2001

형상기억합금 선(Shape Memory Alloy Fibers ： SMA Fibers)을 삽입한 복합재료 평판의 고온 환경에서의 열적 좌굴 및 진동 해석을 유한요소법을 이용하여 수행하였다 1 차 전단변형이론을 적용하여 적층판을 모델링하였고, 온도 변화 효과는 적층판의 전 영역에서 균일한 온도 분포로 가정하였다. 형상기억합금 선의 온도에 대한 비선형 재료 성질을 고려하여 열적 좌굴 해석 수행 시 반복 계산법을 이용하였고, 자유 진동 해석에서는 시스템의 자유도를 줄이기 위하여 Guyan-Reduction(CR)을 사용하였다. 온도 변화와 형상기억합금 선의 체적비(volume fraction) 및 초기 변형률(initial strain) 변화에 따른 임계 온도와 고유 진동수의 특성을 해석하였다.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.210-215
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• 2008

This paper presents an experimental study on a bending actuator with a shape memory alloy wire. In this study, we introduced design process and experimental result of the bending actuator. The bending actuator consists of a SMA wire, springs, and a glass/epoxy strip. In the bending actuator, springs were used to restore the SMA wire to its initial shape right after actuation. To obtain properties of the SMA wire, DSC test was performed and the behavior of the SMA wire under different loadings was observed. Finally, the proposed bending actuator shows reasonable actuation behavior with relatively lower power consumption, fast response and effective efficiency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2913-2921
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• 1994

In SMA(shape memory alloy), the degradation by fatigue is one of the most important problems to be overcome, when SMA is used for robot-actuator material. The actuator is operated repeatitively for long time and its repeating operation develops the fatigue degradation of SMA. The fatigue degradation changes the transformation temperature and deformation behavior and results in inaccurate operation control of robot. Accordingly, the changing behavior of transformation temperature and deformation which results from repeating operation is to be investigated in advance and the scheme to resolve those problems have to be made for the design of actuator. In this study, the fatigue tests were carried out on SMA specimens prepared to have different condition of aging time and pre-strain with the direct-current heating-cooling method, which was a general method of operation in robot actuators. The behavior of transformation temperature and deformation were examined and analyzed in each specimen and the study was performed to establish the optimistic manufacturing condition of SMA against the fatigue degradation.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.157.2-157.2
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• 2005

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.924-927
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• 2007

In this study, adaptation of two-way shape memory effect of SMA wire to the actuator is examined. Therefore the SMA characteristics which are training, material properties, response time at different thermal cycling rates are tested. During training, permanent deformation is accumulated till a certain number of cycle and then saturated. The amount of two-way strain is unchangeable over all cycle and the slope of strain(or stress)-temperature curve is slower as the increase of applied stress. The rate effect is observed resulted from the thermal distribution which heating profile differs from cooling as thermal cycling time. Using the estimated SMA properties, an experimental test for the simple smart wing is performed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.16-20
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• 2008

This paper presents the construction of micro tool clamping device using a Ni-Ti shape memory alloy(SMA) ring. Clamping force of the device is produced by elastic force of the SMA reverted to its original shape in normal temperature. Phase transformation of the SMA was realized by temperature control using a peltier element. Prototype of the SMA tool clamping device was fabricated and examined its clamping force and clamping/unclamping operation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.9-14
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• 2007

In this paper, a rotating tool clamping device was developed based on a shape memory alloy(SMA) and its feasibility as a tool holder was experimentally explored. The SMA-based device was able to alter clamping to unclamping through temperature control within 1 second. The means and repeatability(${\sigma}$) of the tool clamping force were 185.5N and 6N respectively and its drifts were less than 3% for an hour. Considering the temperature hysteresis of the SMA-based tool clamping device, it is necessary to heat the SMA ring to around $50^{\circ}C$ after tool change to obtain more clamping force.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.1
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• pp.77-86
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• 2004

This paper introduces a shape memory alloy-restrainer-damper(SMA-RD) to protect multiple span continuous steel bridges from seismic loads. The type of bridges has only one fixed bearing condition on a pier and expansion bearings are located on the other piers and abutments. Due to this state and a big mass of the deck, these bridges are usually very vulnerable to column's damage on which fixed bearings are located and large deformation of abutments in passive action. Two types of SMA-RDs are developed, and their effect is inspected for protecting the bridges through seismic analyses. Conventional steel restrainer cables are also used to reduce the seismic vulnerability of the bridge and the results are compared to those of the SMA-RDs.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.14-20
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• 2006

In recent year, as the robot technology is developed, the researches on the artificial muscle actuator that enables robot to move dexterously like biological organ become active. Actuators are key technologies underpinning robotics. Breakthroughs in actuator technology, particular in terms of power-to-weight ratio, or energy-density, will have significant impacts upon the design and control of robotic system. In this paper, a new approach to design and control of shape memory alloy(SMA) actuator is presented to drive the robot hand. SMA wire is divided into many segments and their thermal states of the SMA are controlled individually in a binary manner. This control manner will reduce the hysteresis that the SMA material has and it becomes the fundamental technology to develop the anthropomorphic robot hand. In this paper, the mechanism In the digital step motor of the shape memory alloy that is driven by the segmented binary control, which is a new control technique, is studied. This SMA digital step actuator applies for the robot hand and the driving mechanism of the robot hand is investigated.