• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.2
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• pp.147-152
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• 2016

Shape Memory Alloys (SMAs) undergo changes in shape and hardness when heated or cooled, and do so with great force. Since wire-type SMAs contract in length when heated and pull with a surprisingly large force and move silently, they can be used as actuactors which replace motors. These SMA actuators can be heated directly with electricity and can be used to create a wide range of motions. This paper presents the mechanical design and control for a three fingered, six degree-of-freedom robotic hand actuated by SMA actuators. Each finger has two joints and each joint is actuated with two tendons in the antagonistic manner. In order to create the sufficient force to make the smooth motion, the tendon is composed of two SMA actuators in parallel. For controlling the current to heat the SMA actuators, PWM drivers are used. In experiments, the antagonistic interaction of fingers are evaluated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.1-6
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• 2005

In this research, the thermomechanical responses of shape memory alloy(SMA) actuators and their applications in the structures combining strip SMA actuators are investigated. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is developed using user material(UMAT) subroutine written by FORTRAN. For the numerical results, the ABAQUS finite element program has been utilized with UMAT subroutine of the numerical algorithm of SMAs. The interactions between the host structure and SMA strip actuator are numerically investigated.

• Smart Structures and Systems
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• v.11 no.3
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• pp.283-297
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• 2013

An innovative cage for spinal fusion surgery is presented within this work. The cage utilizes shape memory alloy for its hinge actuation. Because of the use of SMA, a smaller incision is needed which makes the cage deployment minimally invasive. In the development of the cage, a model for predicting the torsional behavior of SMAs was developed and verified experimentally. The prototype design of the cage was developed and manufactured. The prototype was subjected to static tests per ASTM specifications. The cage survived all of the tests, alluding to its safety within the body.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.53-61
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• 2020

This paper presents a systematic numerical analysis to obtain the re-centering and energy dissipation capacities of Chevron braced steel frames subjected to seismic loadings. In order to develop a recentering seismic resistance system excluding a residual deformation, the chevron braced steel frames are assembled using super-elastic SMA (Shape Memory Alloy) braces. The three-dimensional nonlinear finite element models are constructed to investigate the horizontal stiffness, hysteretic behaviors, and failure modes of the re-centering Chevron bracing system.

• Coupled systems mechanics
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• v.5 no.4
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• pp.329-340
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• 2016

The trigonal shape memory alloys (SMAs) have a great potential to be utilized as the applications with special purposes, such as actuators with high operation frequency. Most studies on the trigonal microstructures typically focus on the well-known classic herringbone pattern, but many other patterns are also possible, such as non-classic herringbone, toothbrush and checkerboard patterns. In the current work, a systematic procedure is developed to find all possible laminate twin microstructures by using geometrically linear compatibility theory. The procedure is verified by SEM images with the information of crystallographic axes of unitcells obtained by EBSD, showing good agreement. Many interesting trigonal R-phase patterns are found in the specimen. Then, their incompatibility are analyzed with nonlinear compatibility theory. The relationship between such incompatibility and the likelihood of occurrence of the microstructures is revealed. The current procedure is rapid, computationally efficient and sufficiently general to allow further extension to other crystal systems and materials.

• Architectural research
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• v.20 no.3
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• pp.75-82
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• 2018

The aim of the study is to evaluate the concrete shear strength and structural behavior of two general beams and eight shape memory alloys (SMAs)-reinforced beams under the flexural test. This work compares the existing reference formula for concrete shear strength with test result to provide the basic data for the design of highly intelligent reinforced concrete (hereinafter, HIRC) beams. The evaluation of the concrete shear strength was performed with effective depth (d=65, 70, 80), SMA diameter change (ø=2.0, 2.5) as the main variables of the specimens. For the relationship between the effective depth and the $V_{\exp}/V_{cal}$, the test result shows that the concrete shear strength gradually approaches 1.0 as the effective depth length increase. For the AIJ formula, the specimens are approached evenly for comparison between $V_{\exp}/V_{cal}$ and the by-product (garnet, fly-ash) reinforced specimen; however, other formulas indicate a deviation.

• Journal of Korean Association for Spatial Structures
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• v.18 no.2
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• pp.109-119
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• 2018

In this paper a systematic numerical analysis is performed to obtain the energy dissipation and re-centering capacities of diagonal steel braced frames subjected to cyclic loading. This diagonal steel bracing systems are fabricated with super-elastic SMA (Shape Memory Alloy) braces in order to develop a recentering seismic resistance system without residual deformation. The three-dimensional nonlinear finite element models are constructed to investigate the horizontal stiffness, drifts and failure modes of the re-centering bracing systems.

• Smart Structures and Systems
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• v.9 no.4
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• pp.313-333
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• 2012

Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic Shape Memory Alloys (SMAs) can recover inelastic strains by stress removal. Since SMA is a costly material, this paper defines the required locations of SMA bars in a typical RC frame to optimize its seismic performance in terms of damage scheme and seismic residual deformations. The intensities of five earthquakes causing failure to a typical RC six-storey building are defined and used to evaluate seven SMA design alternatives.

• Steel and Composite Structures
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• v.48 no.3
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• pp.353-365
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• 2023

Shape memory alloys (SMAs) have emerged as a novel functional material that is being increasingly applied in diverse fields including medical, aeronautical and structural engineering to be used in the active, passive and semi-active structural control devices. This paper is mainly aimed at evaluating the ductility and response modification factor of the steel plate shear wall (SPSW) frames with and without the Ni-Ti shape memory alloys. To this end, different configurations were utilized, in which the walls were used in the first, third, middle, and all stories. The models were numerically analyzed using OpenSees Software. The obtained results indicate that improving the shape memory properties of alloys can greatly enhance the ductility and response modification factor. Furthermore, the model whose first and third stories are equipped with the SMA shear wall was found to be 290% more ductile, with a greater response modification factor compared to the unequipped frame.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.875-888
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• 2013

The researches have recently progressed toward the use of the superelastic shape memory alloys (SMAs) to develop new smart control systems that reduce permanent deformation occurring due to severe earthquake events and that automatically recover original configuration. The superelastic SMA materials are unique metallic alloys that can return to undeformed shape without additional heat treatments only after the removal of applied loads. Once the superelastic SMA materials are thus installed at the place where large deformations are likely to intensively occur, the structural system can make the best use of recentering capabilities. Therefore, this study is intended to propose new buckling-restrained braced frames (BRBFs) with superelastic SMA bracing systems. In order to verify the performance of such bracing systems, 6-story braced frame buildings were designed in accordance with the current design specifications and then nonlinear dynamic analyses were performed at 2D frame model by using seismic hazard ground motions. Based on the analysis results, BRBFs with innovative SMA bracing systems are compared to those with conventional steel bracing systems in terms of peak and residual inter-story drifts. Finally, the analysis results show that new SMA bracing systems are very effective to reduce the residual inter-story drifts.