Abstract
Relatively recent discovery of shape memory alloys (SMA) justifies ongoing research on their properties and an attempt to explain the physical phenomenon responsible for the characteristic behaviour of SMA. Moreover, there have been reported many successful commercial SMA applications to medical cases, mostly based on superelasticity. Even though a wide application range is confirmed, its further contribution growth is currently not seen - mostly due to deficiency of reliable modelling techniques. Recently, lively discussion in the SMA academic community is observed, which deals with modelling issues and numerical implementation.Considering the current trends, the authors of the work make an attempt at qualitative analysis of the material properties for superelasticity. The material characteristics – found using static stretching tests – are sensitive to the variation of local stresses induced in the area where a SMA sample is mounted in a fatigue testing machine. As shown, the phenomena present at the clamping area seem to initiate and govern the process of the solid phase transformation within the entire SMA body. The overall objective of the presented research is to assess the influence of the above stated boundary conditions on the properties of selected types of SMA, using both experimental and numerical results.
Highlights
Shape memory alloys (SMA) belong to smart materials
The values of the mentioned characteristic temperatures rise along with greater stress generation in the material. This phenomenon has a significant impact on the SMA behaviour at specified temperature range, for which only austenite exists in a non-loaded element: Md > T > Af
Before the details regarding carried out experiments are shown, the authors wish to introduce the background for SMA model validation issues, highlighting their specificity
Summary
Shape memory alloys (SMA) belong to smart materials Their unique mechanical properties reveal through the two-way martensitic phase transition activated by force and thermal excitations [1,2,3]. This nanoscale phenomenon introduces the specific macroscale behaviour of SMA, namely one- and two-way shape memory effects, and superelasticity. The values of the mentioned characteristic temperatures rise along with greater stress generation in the material This phenomenon has a significant impact on the SMA behaviour at specified temperature range, for which only austenite exists in a non-loaded element: Md > T > Af. the values of the characteristic temperatures rise after applied mechanical constraints to a SMA element.
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