Temperature dependence of a NiTi shape memory alloy's superelastic behavior at a high strain rate

Chen, Weinong; Song, Bo

doi:10.2140/jomms.2006.1.339

Cited by 29 publications

(15 citation statements)

References 30 publications

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“…Earlier studies indicate that temperature and loading-rate have a significant influence on the superelasticity of SMAs [39,40]. In order to illustrate the temperature and loading-rate dependent behavior of SMAs, Figure 1 shows strain-stress curves of superelastic NiTi wires with a diameter of 1.5 mm at various conditions.…”

Section: A Neuro-fuzzy Model For Smasmentioning

confidence: 99%

Optimal design of superelastic‐friction base isolators for seismic protection of highway bridges against near‐field earthquakes

Ozbulut

Hurlebaus

2011

Earthq Engng Struct Dyn

108

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The seismic response of a multi-span continuous bridge isolated with novel superelastic-friction base isolator (S-FBI) is investigated under near-field earthquakes. The isolation system consists of a flat steel-Teflon sliding bearing and a superelastic NiTi shape memory alloy (SMA) device. The key design parameters of an S-FBI system are the natural period of the isolated bridge, the yielding displacement of the SMA device, and the friction coefficient of the sliding bearings. The goal of this study is to obtain optimal values for each design parameter by performing sensitivity analysis of a bridge isolated by an S-FBI system. First, a three-span continuous bridge is modeled as two-degrees-of-freedom with the S-FBI system. A neuro-fuzzy model is used to capture rate-and temperature-dependent nonlinear behavior of the SMA device. Then, a set of nonlinear time history analyses of the isolated bridge is performed. The variation of the peak response quantities of interest is shown as a function of design parameters of the S-FBI system and the optimal values for each parameter are evaluated. Next, in order to assess the effectiveness of the S-FBI system, the response of the bridge isolated by the S-FBI system is compared with the response of the non-isolated bridge and the same bridge isolated by pure-friction (P-F) sliding isolation system. Finally, the influence of temperature variations on the performance of the S-FBI system is evaluated. The results show that the optimum design of a bridge with the S-FBI system can be achieved by a judicious specification of design parameters.

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Section: A Neuro-fuzzy Model For Smasmentioning

confidence: 99%

Optimal design of superelastic‐friction base isolators for seismic protection of highway bridges against near‐field earthquakes

Ozbulut

Hurlebaus

2011

Earthq Engng Struct Dyn

108

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“…Instead of a conventional stressstrain curve for most metals, a stress-strain loop that includes both loading and unloading portions must be characterized at a common constant strain rate. In this example, we present the design of a set of such experiments where both the loading and unloading portions of the loading pulses are controlled by pulse shaping [9]. In addition to the pulse shaping for the loading portion of the incident pulse, a reverse pulse-shaping technique was used to generate an unloading profile at deforms the specimen at the same constant strain rate as the loading strain rate under dynamic stress equilibrium.…”

Section: Experiments On Shape Memory Alloysmentioning

confidence: 99%

“…Using this technique, the dynamic stress-strain loop at a deformation, whereas the main reflected signal corresponds to the dynamic plastic flow in the specimen. During strain rate of 420 s -1 for a NiTi shape memory alloy was determined [9]. The shape memory alloy studied in these experiments is composed of nominal 55.8% nickel by weight and the balance is titanium.…”

Section: Experiments On Shape Memory Alloysmentioning

confidence: 99%

“…The cylindrical specimens had a dimension of 4.76-mm diameter by 4.76-mm long. Figure 5 shows the incident, reflected, and transmitted pulses at the strain rate of 420 s -1 obtained with the modified Kolsky bar during both loading and unloading phases [9]. The strain-rate history, which is proportional to the reflected pulse in Fig.…”

Section: Experiments On Shape Memory Alloysmentioning

confidence: 99%

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Dynamic Material Property Characterization with Kolsky Bars

Chen

2011

Dynamic Behavior of Materials, Volume 1

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Split Hopkinson pressure bars (SHPB), also called Kolsky bars, have been widely used to determine the stressstrain response of materials in the strain-rate range 10 2 -10 4 /s. Unlike quasi-static testing methods for material properties, the high-rate Kolsky bar technique does not have a closed-loop control system to monitor and adjust testing conditions on the specimen to specified levels. There are no standards to guide the experimental design either. This presentation briefly reviews the physical nature of Kolsky bar experiments and recent modifications in the attempt to conduct experiments for more accurate results. The main approach for obtaining improved results is to deform the specimen uniformly under an equilibrated stress state at a constant strain rate. Examples of experiment design to achieve the desired testing conditions are presented. KOLSKY BARS (SHPB)Most material properties such as yield stress and ultimate strength are obtained under quasi-static loading product quality and reliability under impact conditions such as those encountered in the drop of personal electronic devices, vehicle collision, and sports impact, the mechanical responses of materials under such loading conditions must be characterized accurately. To obtain dynamic response of materials under laboratory controlled conditions, Kolsky [1] placed two elastic rods on both sides of the specimen and then stuck one of the rods with an explosive blast. This concept is schematically shown in Fig. 1, where the elastic rod between the external impact and the specimen is called the incident bar and that rod on the other side the transmission bar. With this arrangement, when the incident bar is loaded by external impact, a compressive stress wave is generated and then propagates towards the specimen, moving the bar material towards the specimen as it sweeps by. When the wave arrives at the interface between the incident bar and the specimen, part of the wave is reflected back into the incident bar and the rest transmits through the specimen into the transmission bar. Laboratory instrumentation can record the stress waves in the incident bar propagating towards the specimen and being reflected back from the specimen and the wave in the transmission bar. Under this arrangement the impact event is controllable and quantitative. Analysis on the recorded waves results in information regarding the loading conditions and deformation states in the specimen. This system has been called the Kolsky bar or a split-Hopkinson pressure bar (SHPB).

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“…Nevertheless, an evaluation of its order of magnitude can be obtained by considering the rate of stress-induced martensitic (SIM) transformation. The latter has been intensively investigated under impact loading conditions [3][4][5][6][7][8], and experimental results demonstrate that almost complete transformation can occur within less than 0.1 msec [6]. This indicates that SMA actuators can, in theory, exhibit frequency bandwidth at the 10 kHz range, if the rate of heat transfer is sufficiently high.…”

Section: Introductionmentioning

confidence: 99%

The Mechanical Response of Shape Memory Alloys Under a Rapid Heating Pulse

Vollach¹,

Shilo²

2009

Exp Mech

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Shape memory alloy (SMA) actuators are very promising due to their large strain and work-output, but are considered to be very slow due to their cooling rate. In this article, we explore the capabilities of a fast one-directional actuation mode based on one-occasional rapid Joule heating of SMA elements. For this purpose, a unique experimental system has been developed that applies a high-voltage electric pulse to a detwined NiTi wire and measures the resulting displacement due to the martensite to austenite phase transformation. The electric pulse is tuned to produce variable temperature jump of up to 160°C within a risetime of few microseconds. One end of the wire is clamped while the displacement of the other end is monitored both by a laser doppler vibrometer and by an optical encoder that measures the displacement of a grating device. Analysis of experimental results reveals a dead time delay between the electric pulse and the wire's response, which is attributed to the austenite nucleation time and which determines the limit on the fastest possible shape memory actuation. Further analysis reveals relations between the dead weight used and the average acceleration and maximal velocity obtained. In particular, the maximal velocity correlates to a constant kinetic energy delivered by the wire, which suggests a constant integrand over the stress-strain curve regardless of the dead-weight used. A comparison of actuation performances demonstrates that our actuation experiments are significantly advantageous over other fast actuation methods in almost every actuation aspect reviewed. This demonstrates the great potential of SMA for applications that require high speeds and large displacements oneoccasional actuation.

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Temperature dependence of a NiTi shape memory alloy's superelastic behavior at a high strain rate

Cited by 29 publications

References 30 publications

Optimal design of superelastic‐friction base isolators for seismic protection of highway bridges against near‐field earthquakes

Optimal design of superelastic‐friction base isolators for seismic protection of highway bridges against near‐field earthquakes

Dynamic Material Property Characterization with Kolsky Bars

The Mechanical Response of Shape Memory Alloys Under a Rapid Heating Pulse

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