• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.439-440
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• 2006

This research proposes a novel method of shape display to present 3-dimensional objects. Shape displays allow us to feel the actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wire frame structure to present 3D objects. The wire frame is composed of small units driven by shape memory alloy(SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wire frame structure. By controlling the current into the SMA actuator and locking mechanism, we call control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.82-88
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• 2008

This paper proposes a novel method of 2 dimensional shape display. Shape displays allow us to feel tile actual volume of the object, unlike conventional 2D visual displays of 3D objects. The proposed method employs a wireframe structure to present 2D or 3D objects. The wireframe is composed of small units driven by shape memory alloy (SMA) actuators. The drive unit is analogous to the agonist-antagonist system of animal musculoskeletal systems, where the SMA actuators serve as agonist and antagonist muscles. The force in the SMA actuator is controlled by electrical current. The drive unit is equipped with the locking mechanism so that it can sustain the external force exerted by the user as well as the own weight of the wireframe structure. By controlling the current into the SMA actuator and locking mechanism, we can control the angle of the drive unit. A chain of drive units enables presentation of 2 dimensional objects. 3 dimensional presentations are possible by collecting the chains of drive units.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.72-78
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• 2002

Thermomechanical behavior and mechanical properties of A16061 matrix composite with shape memory alloy(SMA) fiber are studied by using fnite element analysis(FEA). The smartness of the SMA is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when healed after being prestrained. In this paper, an analytical model is assumed two dimentional axisymetric model of one fiber and around the matrix. To evaluate the strength of composite usig FEM, the concept of smart composite was simulated on computer. The Shape memory effect(SME) simulation is very difficult using FEM because of the nonlinear analysis and the elastic plastic analysis. Thus, in this paper, the FEA was carried out at two critical temperature conditions; room temperature and high temperature(363K). The analysis is compare the finite element analysis result with the test result for the analysis validity.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.186-191
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• 2001

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi alloy fiber was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 shape memory alloy(SMA) composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation and volume fraction of TiNi alloy. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 SMA composite. In addition, two dimensional AE source location technique was applied to inspect the crack initiation and propagation in composite.

• Transactions of Materials Processing
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• v.22 no.8
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• pp.470-476
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• 2013

The aim of the current study was to predict shape recovery behavior of Ni-Ti shape memory alloy (SMA) wire after loading-unloading and after wire drawing. The superelasticity of SMA was analyzed by a hyper-elastic model for the Mullins effect using ABAQUS. Firstly, tensile tests and loading-unloading tests of the Ni-Ti SMA wire with a diameter 1.0 mm were performed using an MTS servo-hydraulic tester. The parameters for the Mullins effect were computed by ABAQUS based on curve-fitting of the loading-unloading test data. The proposed FE-model predicted the shape recovery of Ni-Ti SMA after wire drawing. Finally, the effectiveness of the model was verified by drawing experiments. The wire drawing experiments using the Ni-Ti SMA were conducted on a drawing machine(1ton, 50mm/s). In order to evaluate the shape recovery of Ni-Ti SMA, the drawn wires are annealed for 30min at $450^{\circ}C$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1812-1818
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• 2005

Even though SMA actuators have high power to volume ratio, there exist disadvantages such as hysteresis and saturation. So the model identification for SMA actuators is very difficult. For the qualitative model identification, we described the behavior of SMA actuators using a so-called diagonal model, which can readily expect the turning point of an incomplete phase transformation. For the quantitative model identification, we developed the general dynamics of SMA actuators using the modified Liang's model. Using this dynamics we can describe the hysteresis and the saturation very well. It is also very important to notice that the modified Liang's model maintains a continuous martensite fraction at the change of the phase transformation but the original model cannot.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.6-11
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• 2010

For the purpose of reducing the energy consumption in the house heating, the various devices have been developed. One of these is to control the flow in the heat pipe and the flow control valve using shape memory alloy(SMA) spring is proposed in our study. The proposed house heating system is to save the gas consumption and the remote control system is designed for the convenience of using the proposed valve. The developed valve consists of SMA spring, disk, return spring, and regulation handle. The regulation handle is for supplying the additional hot water and is controlled by remote-control-motor. In order to design the remote control system, the Zigbee wireless communication protocol is used. The performance of the proposed valve structure is shown through the experimental result.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.129-130
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• 2010

Lap splice of longitudinal reinforcing steels was located in the plastic hinge region of most bridge piers that had been designed and constructed before the adoption of the 1992 seismic design provision of Korea Highway Design Specification. This research aims at improving the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal steels, of which the plastic hinge region was wrapped by the shape memory alloy (SMA) wires. Quasi-static test was used to investigate the seismic behaviours of RC test specimens.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.145-148
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• 2005

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 amow1t 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 Mechanical Engineers A
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• v.27 no.4
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• pp.515-523
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• 2003

Shape memory is physical phenomenon which a platically metal is restored to its original shape by a solid state phase change by heating. TiNi alloy the most effective material in the shape memory alloy(SMA). To study(measure) recovery stress of intelligent composite. Ti50-Ni50 shape memory matrix with prestrain SMA fiber. When SMA fiber of the intelligent composite is heated over austenite starting temperature(As) by electric heating. a recovery stress are generated. The recovery stress of the intelligent composite was measured by strain gage or photoelastic experiment. Measuring method of recovery stress by photoelastic experiment was developed in this research. It was certified that photoelastic experiment was more effective and more precise than strain gage method in the measurement of recovery stress.