Numerical analysis of NiTi actuators with stress risers: The role of bias load and actuation temperature

Shayanfard, Pejman; Heller, Luděk; Šandera, Pavel; Šittner, Petr

doi:10.1016/j.engfracmech.2021.107551

Cited by 9 publications

(3 citation statements)

References 32 publications

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“…The temperatures used to study its effect on our simulated equiatomic NiTi actuator were (5,10,15,20,25,30,35,40,45,50 For every (force-deformation) hysteresis loop, the points of transformation increased primarily during the loading cycle (upper plateau) and decreased during the unloading cycle (lower plateau). At 5℃: for the upper plateau, the point transformation starts with deformation equal to 2.02 mm and spring force equal to 2.40 6 N; these values increase along the upper plateau to become 𝑓 which has deformation equal to 19.8mm and spring force 6.007 N, respectively.…”

Section: Figure 4: (A) Represents the Effect Of Spring Height On The ...mentioning

confidence: 99%

“…Actuators are used as thermal switch-control coolants in automobiles, as a flap control for controlling airflow in air conditioners, as air dampers for multi-function electric ovens, and as a thermal mixing valve in faucets. Also, they are used in various aerospace applications and microrobots [30][31][32][33][34][35]. Actuators work with a large force generated by a constrained shape memory alloy with element recovery.…”

Section: Introductionmentioning

confidence: 99%

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Influence of NiTi Spring Dimensions and Temperature on the Actuator Properties

Al Shadidi,

Falih,

Suhail

et al. 2023

IJP

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Nitinol (NiTi) is used in many medical applications, including hard tissue replacements, because of its suitable characteristics, including a close elastic modulus to that of bones. Due to the great importance of the mechanical properties of this material in tissue replacements, this work aims to study the hysteresis response in an attempt to explore the ability of the material to remember its previous mechanical state in addition to its ability to withstand stress and to obtain the optimal dimensions and specifications for the manufacturer of NiTi actuators. Stress-strain examination is done in a computational way using a mutable Lagoudas MATLAB code for various coil radii, environment temperatures, and coil lengths. The computational methodology was done by varying the dimensions and the ambient temperature of the simulated NiTi spring actuator. The hysteresis loop is studied by increasing the external stress for a reversible martensitic transformation. The coil radius, spring height, and wire radius affect the spring force and deformations. In the same way, these parameters affect the strain and stress point values. These changes are shown through the martensite and austenite start and finish values. The NiTi hysteresis loop narrows with increasing ambient temperature or initial spring height. At a higher temperature, the force supplied to the actuator must be less for the same deformation; therefore, a higher ambient temperature provides more efficiency for the shape memory devices and a longer lifetime for the actuator.

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Section: Figure 4: (A) Represents the Effect Of Spring Height On The ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of NiTi Spring Dimensions and Temperature on the Actuator Properties

Al Shadidi,

Falih,

Suhail

et al. 2023

IJP

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show abstract

“…The research is mainly focused on the stress-induced martensitic transormation or superelasticity of SMA. The role of the transformation temperature became a topic later on and is still subject for researchers [47,48]. Still, the influence of the fatigue over the whole lifespan of an SMA component on the applicability of the mentioned approaches is not yet known.…”

Section: Goal Of Research Work/motivationmentioning

confidence: 99%

The Development and Verification of a Simulation Model of Shape-Memory Alloy Wires for Strain Prediction

et al. 2022

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One of the greatest challenges in the design of shape-memory elements (mostly binary Nickel-Titanium wires) is to ensure that the required travel (stroke) is achieved, as this is subject to variation due to various influencing factors. One way of predicting the stroke is to use a suitable energy model. In the past, for example, a model was developed by Oelschläger with which the stroke can be calculated on the basis of the electrical energy. However, so far no model takes into account the change of the phase transformation temperature. In this study, the model of Oelschläger is extended and verified to consider the degradation behavior over the whole lifetime. For this purpose, fatigue tests of 52 wires (2 different load scenarios) were performed. Based on these tests and the application of statistical methods (distribution models, goodnes-of-fit tests etc.), a target model was developed for each load scenario, which is used to verify the extended energy model. The energy model was applied to wires of both load scenarios to simulate the stroke progression. The verification of the extended simulation model shows that it is possible to simulate the longterm behavior of the stroke for one of the two load scenarios. The second load scenario shows deviations between the target model and the simulation, which is due to problems in the area of measurement equipment, convection, and temperature distribution in the wire. Nevertheless, a decisive modeling approach could be developed, which can be used to consider the long-term behavior of the phase transformation temperature of wires in simulations.

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