Thermomechanical characterization of high temperature SMA actuators

Kumar, Pradeep; Lagoudas, Dimitris C.; Zanca, Kevin J.; Lagoudas, Magdalini Z.

doi:10.1117/12.658960

Cited by 10 publications

(9 citation statements)

References 25 publications

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“…As demonstrated in this investigation and generally well known from the literature (i.e., Figure 6), additions of Pd greater than about 10 at. pct increase the transformation temperature of NiTi alloys, but with few exceptions, [12][13][14] the shape-memory behavior (strain recovery) of these high-temperature alloys has been determined only under stress-free conditions. Consequently, given the limited amount of basic mechanical test data and general lack of information regarding the work attributes of these materials, the focus of this investigation was on the load-biased shapememory response of ternary NiTiPd alloys as a function of Pd content.…”

Section: Discussionmentioning

confidence: 99%

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Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Bigelow

Padula

Garg

et al. 2010

Metall Mater Trans A

130

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While NiTiPd alloys have been extensively studied for proposed use in high-temperature shapememory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd) 49.5 Ti 50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

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Section: Discussionmentioning

confidence: 99%

“…The most notable exceptions are more recent studies by Cai et al [12] on Ni 19.4 Ti 50.6 Pd 30 , Noebe et al [13] on Ni 19.5 Ti 50. 5 Pd 30 , and Kumar et al [14] on Ni 10 Ti 50 Pd 40 . These studies were predominantly limited to higher Pd containing alloys.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Bigelow

Padula

Garg

et al. 2010

Metall Mater Trans A

130

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“…Recent efforts have focused on studying the work characteristics of these materials in detail. Previous study on the compressive behavior of Ti 50 Pd 40 Ni 10 [16] had shown a strong dependence of actuation strain on applied strain and actuation stress level. Following the work on studying the work characteristics in compression, the focus of this effort is to study in detail the effect of the transformation behavior in TiPdNi under tensile stress.…”

Section: Introductionmentioning

confidence: 99%

“…Until recently, most efforts studied the recoverable behavior of the material under zeros stress conditions. Recent efforts on HTSMAs have focused on studying and improving the work characteristics of the TiPdNi and TiPtNi alloys by increasing the critical stress for slip [16][17][18][19]. Improved techniques have also been developed to process the material in different forms [20].…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical characterization of a TiPdNi high temperature SMA under tension

Kumar

Lagoudas

2007

Behavior and Mechanics of Multifunctional and Composite Materials 2007

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The focus of this paper is the study of tensile work characteristics and the transformation behavior of a High Temperature Shape Memory Alloy (HTSMA) by thermomechanical characterization at temperatures ranging from 200 to 500°C. In order to investigate the above issues, a nominal composition of Ti 50 Pd 40 Ni 10 HTSMA was used. The alloy was fabricated using a vacuum arc melting technique. The melt was cast and hot rolled followed by cutting of tensile specimen using Electrode Discharge Machining (EDM). A high temperature experimental setup was developed on a load frame to test the material at high temperatures under constrained actuation conditions. The stability of the material response under cyclic actuation was also investigated. The observations from the tests are presented in this paper. Microprobe analysis was performed on the as-cast and rolled material to study the composition. The material was also studied by X-ray diffraction (XRD) and optical microscopy before and after testing. Certain key observations about the material response are discussed specifically, in terms of transformation behavior, recoverable strains under various applied total strains, and cyclic thermomechanical behavior.

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“…Most recent studies on HTSMAs have focussed on studying and improving the actuation characteristics and processing methods for the alloy [3][4][5]. Newer alloys with higher transformation temperatures are constantly being developed [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Interaction of creep with the martensitic transformation in TiPdNi High Temp erature Shape Memory Alloys

Lagoudas

Kumar

2009

ESOMAT 2009 - 8th European Symposium on Martensitic Transformations

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Abstract. High Temperature Shape Memory Alloys represent a class of Shape Memory Alloys with transformation temperatures greater than 100 • C. However, as a consequence of their high transformation temperatures, these alloys can be exposed to a temperature regime where creep behavior can occur simultaneously during the phase transformation. Depending on the transformation temperatures of a shape memory alloy, the rate dependent plastic strain generated at the high operating temperatures, can significantly impact the actuators performance. The present effort focuses on understanding the interaction between the phase transformation and creep occurring simultaneously in shape memory alloys. For this purpose two alloys with transformation temperatures that overlap with the creep regime of the material are selected and fabricated by hot rolling/extrusion. Compression specimens are machined from the rolled material and standard isothermal creep tests are conducted at specific stress levels. In addition transformation induced thermal cycling is conducted to study the simultaneous transformation/viscoplastic behavior. Optical microscopy and TEM studies are conducted on the tested specimen to observe the changes in the microstructure. Based on the thermomechanical tests and the microstructural observations suitable conclusions are drawn to explain the interaction between the two mechanisms.

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Thermomechanical characterization of high temperature SMA actuators

Cited by 10 publications

References 25 publications

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Thermomechanical characterization of a TiPdNi high temperature SMA under tension

Interaction of creep with the martensitic transformation in TiPdNi High Temp erature Shape Memory Alloys

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