• Title, Summary, Keyword: Shape Memory Effect

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Experimental Study on the TWSME Characteristics using Compressive Loading Cycles (압축 하중사이클을 이용한 양방향 형상기억효과 특성 연구)

  • Yoo, Young-Ik;Kim, Hyun-Chul;Lee, Jung-Ju;Lee, Woo-Yong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.4
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    • pp.101-107
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    • 2009
  • Actuators using shape memory alloys use the one-way shape recovery stress. But when external load is applied the accumulated plastic strain induced by repeated deformation is the factor of generation of uncorrect recovery stress and unreliability. To solve this problem, two-way shape memory effect (TWSME) is considered. TWSME induced by plastic deformation have advantages including simple heating cycle without external force and enough recovery force for using actuators. but there is no research on cylinder-type or tube-type shape memory alloy actuators using two-way shape memory effect until now. Therefore in this study, characteristics of two-way shape memory effect is verified through the compression experiments using cylinder-type and tube-type specimens.

Shape Recovery and Dynamic Compression Properties of Shape Memory Foams for the Insole of Shoes (신발 인솔용 형상기억 발포체의 동적압축 및 형상회복 특성)

  • Lim, Sung-Wook;Park, Eun-Young;Park, Cha-Cheol
    • Textile Science and Engineering
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    • v.48 no.6
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    • pp.380-385
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    • 2011
  • To develop memory foams for the insole of shoes. In order to examine the effect that the types of foam plays on compression set, shape memory characteristics commercial EVA foams and shape memory foams were produced. Cross-linking agents are used in the production of the shape memory foam. The effects that the types of crosslinking agents have on the shape memory characteristics. Shape memory foams appeared to have excellent shape recovery property. They experienced less plastic deformation to compression than the regular foams. Therefore, shape memory foam proved to be more suited for the insole of shoes than the commercial EVA foam. As the percentage of sulfur increased in the cross-linking agent that is used in the production of the shape memory foam, the shape memory characteristic also improved significantly.

Effect of Training( SIM↔γ) on Shape Memory Effect of Fe-30%Mn-6%Si Alloy (Fe-30%Mn-6% Si 합금의 형상기억효과에 미치는 Training(SIM↔γ)의 영향)

  • Han, Sang Ho;Jun, Joong Hwan;Choi, Chong Sool
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.2
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    • pp.118-128
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    • 1994
  • Five alloys were selected randomly in the composition range showing the best shape memory effect in Fe-Mn-Si system reported by Murakami. The shape memory effects of those alloys were mainly investigated through the training treatment which consisted of the repetition of 2% tensile deformation at room temperature and subsequent annealing at $600^{\circ}C$ above $A_r$ temperature. At the same deformation degress in rolling $600^{\circ}C$-annealing for 1 hr. showed the best shape memory effect, and 10%-deformation degrees represented maxima of the shpae memory effects at all annealing temperatures, $500^{\circ}C$, $600^{\circ}C$ and $700^{\circ}C$. The shape memory effects of the alloys were increased by increasing training cycle up to 5 cycles. This was because a large number of dislocations introduced by training process gave rise to increase in the austenite yield stress, and acted as nucleation sites for stress induced ${\varepsilon}$ martensite. The thermal cycling treatment, repetition of cooling in nitrogen at $-196{\circ}C$ and heating to $300^{\circ}C$ for 5 min., did not improve the shape memory effect.

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Development and Application of Porous Superelastic TiNi Materials for Medical Implants

  • Gjunter, V.E.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.7-7
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    • 1998
  • Research activities of Russian Medical Engineering Center and Institute of Medical Materials of Shape Memory Alloys and Implants are presented as follows: ${\bullet}$ The direction of elaboration of porous shape memory alloys for medicine. ${\bullet}$ Medical and technical requirements and physical and mechanical criteria of porous shape memory implants elaboration. ${\bullet}$ Basic laws of heat-, stress- and strain-induced changes of mechanical properties, shape memory effect and superelasticity in porous TiNi-based alloys. ${\bullet}$ Methods of regulation of shape memory effect parameters in porous alloys and methods for controlling the regulation-induced changes of physical and mechanical properties. ${\bullet}$ Original technologies of elaboration of porous alloys In various fields of medicine. ${\bullet}$ Arrangement of serial production of shape memory porous implants and examples of their medical use.

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Thermomechanical Behaviors of Shape Memory Alloy Using Finite Element Analysis (유한요소해석을 이용한 형상기억합금의 열적/기계적 거동 연구)

  • ;Scott R. White
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.833-836
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    • 2001
  • The thermomechanical behaviors of the shape memory alloy were conducted through the finite element analysis of ABAQUS with UMAT user subroutine. The unified thermomechanical constitutive equation suggested by Lagoudas was adapted into the UMAT user subroutine to investigate the characteristics of the shape memory alloy. The three cases were solved to investigate the thermomechanical characteristics of the shape memory alloy. The material properties for the analysis were obtained by DSC and DMA techniques. According to the results, the thermomechanical characteristics, such as a shape memory effect and a pseudoelastic effect, could be obtained through the finite element analysis and the analysis results were revealed to agree well with the experimental results. Therefore, the finite element analysis using UMAT user subroutine is one of prominent analysis techniques to investigate the thermomechnical behaviors of the shape memory alloy quantitatively.

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An Analytical Study on Prestrain and Shape Memory Effect of Composite Reinforced with Shape Memory Alloy (형상기억합금 강화 복합재의 사전 변형률과 형상기억 효과에 대한 이론적 고찰)

  • 이재곤;김진곤;김기대
    • Composites Research
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    • v.17 no.5
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    • pp.54-60
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    • 2004
  • A new three-dimensional model for predicting the relationship between the prestrain of the composite and the amount of phase transformation of shape memory alloy inducing shape memory effect has been proposed by using Eshelby's equivalent inclusion method with Mori-Tanaka's mean field theory. The model composite is aluminum matrix reinforced with short TiNi fiber shape memory alloy, where the matrix is work-hardening material of power-law type. The analytical results predicted by the current model show that most of the prestrain is induced by the plastic deformation of the matrix, except the small prestrain region. The strengthening mechanism of the composite by the shape memory effect should be explained by excluding its increase of yield stress due to the work-hardening effect of the matrix.

Experimental study of NiTi shape memory alloy (NiTi 형상기억합금의 실험적 연구)

  • Yang Seung-Yong;Goo Byeong-Choon;Kim Hyung-Jin;Nam Tae-Hyun
    • Proceedings of the KSR Conference
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    • pp.611-615
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    • 2004
  • To obtain material properties of NiTi shape memory alloy showing pseudoelastic or shape memory effect, tensile test was conducted for various temperatures. Transformation temperature also was measured by using DSC(Differential Scanning Calorimeter), and crystallographic feature of transformation was observed by XRD(X-ray Diffraction).

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Development of On-Line Monitoring System using Smart material (지적복합재료를 이용한 온라인 모니터링시스템 개발)

  • Lee, Jin-Kyung;Park, Young-Chul;Lee, Sang-Pill;Park, Yi-Hyun
    • Proceedings of the KSME Conference
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    • pp.67-71
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    • 2003
  • A hot press method was used to create the optimal fabrication condition for a Shape Memory Alloy(SMA) composite. The bonding strength between the matrix and the reinforcement within the SMA composite by the hot press method was more increased by cold rolling. In this study, the objective was to develop an on-line monitoring system in order to prevent the crack initiation and propagation by shape memory effect in SMA composite. Shape memory effect was used to prevent the SMA composite from crack propagation. For this system an optimal AE parameter should be determined according to the degree of damage and crack initiation. When the SMA composite was heated by the plate heater attached at the composite, the propagating cracks could be controlled by the compressive force of SMA.

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Shape memory alloy-based smart RC bridges: overview of state-of-the-art

  • Alam, M.S.;Nehdi, M.;Youssef, M.A.
    • Smart Structures and Systems
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    • v.4 no.3
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    • pp.367-389
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    • 2008
  • Shape Memory Alloys (SMAs) are unique materials with a paramount potential for various applications in bridges. The novelty of this material lies in its ability to undergo large deformations and return to its undeformed shape through stress removal (superelasticity) or heating (shape memory effect). In particular, Ni-Ti alloys have distinct thermomechanical properties including superelasticity, shape memory effect, and hysteretic damping. SMA along with sensing devices can be effectively used to construct smart Reinforced Concrete (RC) bridges that can detect and repair damage, and adapt to changes in the loading conditions. SMA can also be used to retrofit existing deficient bridges. This includes the use of external post-tensioning, dampers, isolators and/or restrainers. This paper critically examines the fundamental characteristics of SMA and available sensing devices emphasizing the factors that control their properties. Existing SMA models are discussed and the application of one of the models to analyze a bridge pier is presented. SMA applications in the construction of smart bridge structures are discussed. Future trends and methods to achieve smart bridges are also proposed.

Manufacture and Properties of Shape Memory Polyurethane Fibers (형상기억 폴리우레탄 섬유의 제조 및 물성평가)

  • Hong, Seok-In;Youk, Ji-Ho;Yu, Woong-Ryeol
    • Textile Science and Engineering
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    • v.47 no.2
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    • pp.85-91
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    • 2010
  • A shape memory polyurethane (SMPU) with a transition temperature of $28^{\circ}C$ was synthesized to investigate its fiber formation characteristics. Based on the thermal analysis a melt spinning process was designed, from which mono- and multi-filaments of SMPU fibers were manufactured. The shape memory performance of both SMPU film and fibers was evaluated using a thermo-mechanical cyclic test. The results revealed that SMPU fibers show similar shape memory behavior to that of SMPU film. The effect of post treatments such as annealing, drawing and heat-set on the shape memory performance of SMPU fibers was investigated and their effects on the micro-structural change of SMPU fibers were analyzed using a molecular configuration model. It was demonstrated that the properties of SMPU fibers can be tailored using these post treatments, thereby shape memory woven fabrics can be developed using SMPU fibers.