Modeling of rate-dependent damping capacity of one-dimensional superelastic shape memory alloys

Entire or partial loss of function in the shoulder, elbow or wrist represent an increasingly common ailment connected to a wide range of injuries or other conditions including sports, occupational, spinal cord injuries or strokes. A general treatment of these problems relies on physiotherapy procedures. An increasing number of metallic materials are continuously being developed to expect the requirements for different engineering applications including biomedical field. Few constructive models that can involve intelligent materials are analyzed to establish the advantages in usage of shape memory elements mechanical implementation. The shape memory effect, superelasticity and damping capacity are unique characteristics at metallic alloys which demand careful consideration in both design and manufacturing processes. The actual rehabilitation systems can be improved using smart elements in motorized equipments like robotic systems. Shape memory alloys, especially NiTi (nitinol), represent a very good alternative for actuation in equipments with moving dispositive based on very good actuation properties, low mass, small size, safety and user friendliness. In this article the actuation and the force characteristics were analyzed to investigate a relationship between the bending angle and the actuation real value.

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Rate-Dependent Damping Capacity of NiTi Shape Memory Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.37 ◽

2011 ◽

Vol 172-174 ◽

pp. 37-42 ◽

Cited By ~ 2

Author(s):

Yong Jun He ◽

Qing Ping Sun

Keyword(s):

Shape Memory Alloy ◽

Strain Rate ◽

Shape Memory ◽

Strain Curve ◽

Tensile Loading ◽

Niti Shape Memory Alloy ◽

Damping Capacity ◽

Environmental Condition ◽

Mechanical Coupling ◽

Rate Dependent

High damping capacity is one of the prominent properties of NiTi shape memory alloy (SMA), having applications in many engineering devices to reduce unwanted vibrations. Recent experiments demonstrated that, the hysteresis loop of the stress-strain curve of a NiTi strip/wire under a tensile loading-unloading cycle changed non-monotonically with the loading rate, i.e., a maximum damping capacity was obtained at an intermediate strain rate (ε.critical). This rate dependence is due to the coupling between the temperature dependence of material’s transformation stresses, latent-heat release/absorption in the forward/reverse phase transition and the associated heat exchange between the specimen and the environment. In this paper, a simple analytical model was developed to quantify these thermo-mechanical coupling effects on the damping capacity of the NiTi strips/wires under the tensile loading-unloading cycle. We found that, besides the material thermal/mechanical properties and specimen geometry, environmental condition also affects the damping capacity; and the critical strain rate ε.criticalfor achieving a maximum damping capacity can be changed by varying the environmental condition. The theoretical predictions agree quantitatively with the experiments.

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Shape memory alloy–actuated prestressed composites with application to morphing automotive fender skirts

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x18812702 ◽

2018 ◽

Vol 30 (3) ◽

pp. 479-494 ◽

Cited By ~ 6

Author(s):

Venkata Siva C Chillara ◽

Leon M Headings ◽

Ryohei Tsuruta ◽

Eiji Itakura ◽

Umesh Gandhi ◽

...

Keyword(s):

Shape Memory Alloy ◽

Shape Memory Alloys ◽

Shape Memory ◽

Smart Materials ◽

Design Procedure ◽

Building Blocks ◽

Smart Composite ◽

Thermally Induced ◽

One Dimensional ◽

Flat Shape

This work presents smart laminated composites that enable morphing vehicle structures. Morphing panels can be effective for drag reduction, for example, adaptive fender skirts. Mechanical prestress provides tailored curvature in composites without the drawbacks of thermally induced residual stress. When driven by smart materials such as shape memory alloys, mechanically-prestressed composites can serve as building blocks for morphing structures. An analytical energy-based model is presented to calculate the curved shape of a composite as a function of force applied by an embedded actuator. Shape transition is modeled by providing the actuation force as an input to a one-dimensional thermomechanical constitutive model of a shape memory alloy wire. A design procedure, based on the analytical model, is presented for morphing fender skirts comprising radially configured smart composite elements. A half-scale fender skirt for a compact passenger car is designed, fabricated, and tested. The demonstrator has a domed unactuated shape and morphs to a flat shape when actuated using shape memory alloys. Rapid actuation is demonstrated by coupling shape memory alloys with integrated quick-release latches; the latches reduce actuation time by 95%. The demonstrator is 62% lighter than an equivalent dome-shaped steel fender skirt.

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Effect of Heat Treatments on the Damping Characteristics of TiNi-Based Shape Memory Alloys

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.319.33 ◽

2006 ◽

Vol 319 ◽

pp. 33-38 ◽

Cited By ~ 4

Author(s):

I. Yoshida ◽

Kazuhiro Otsuka

Keyword(s):

Internal Friction ◽

Shape Memory Alloys ◽

Shape Memory ◽

Low Frequency ◽

Heat Treatments ◽

Damping Capacity ◽

Temperature Hysteresis ◽

Temperature Spectrum ◽

Two Peaks ◽

Very High

Low frequency internal friction of Ti49Ni51 binary and Ti50Ni40Cu10 ternary shape memory alloys has been measured. The effect of solution and aging heat treatments on the damping property was examined. The temperature spectrum of internal friction for TiNi binary alloy consists, in general, of two peaks; one is a transition peak which is associated with the parent-martensite transformation and is rather unstable in a sense that it strongly depends on the frequency and decreases considerably when held at a constant temperature. The other one is a very high peak of the order of 10-2, which appears at around 200K. It appears both on cooling and on heating with no temperature hysteresis, and is very stable. The behavior of the peak is strongly influenced by the heat treatments. The trial of two-stage aging with a purpose of improving the damping capacity has been proved unsatisfactory. TiNiCu has a very high damping, the highest internal friction reaching 0.2, but by quenching from very high temperature, say 1373K, the damping is remarkably lowered. For the realization of high damping the quenching from a certain temperature range around 1173K seems the most preferable condition.

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Design of Shape Memory Alloy Springs With Applications in Vibration Control

Journal of Vibration and Acoustics ◽

10.1115/1.2930305 ◽

1993 ◽

Vol 115 (1) ◽

pp. 129-135 ◽

Cited By ~ 44

Author(s):

C. Liang ◽

C. A. Rogers

Keyword(s):

Shape Memory Alloy ◽

Shape Memory Alloys ◽

Shape Memory ◽

Vibration Control ◽

Young’S Modulus ◽

Young's Modulus ◽

Design Method ◽

Control Area ◽

Spring Constant ◽

Damping Capacity

Shape memory alloys (SMAs) have several unique characteristics, including their Young’s modulus-temperature relations, shape memory effects, and damping characteristics. The Young’s modulus of the high-temperature austenite of SMAs is about three to four times as large as that of low-temperature martensite. Therefore, a spring made of shape memory alloy can change its spring constant by a factor of three to four. Since a shape memory alloy spring can vary its spring constant, provide recovery stress (shape memory effect), or be designed with a high damping capacity, it may be useful in adaptive vibration control. Some vibration control concepts utilizing the unique characteristics of SMAs will be presented in this paper. Shape memory alloy springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some design approaches based upon linear theory have been proposed for shape memory alloy springs. A more accurate design method for SMA springs based on a new nonlinear thermomechanical constitutive relation of SMA is also presented in this paper.

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