Structure from shape memory alloys and stability problems
Shape memory alloys (SMA), due to their unique mechanical and thermal properties can be used to create unique designs and innovative technology. Briefly describes the known and planned uses of SMA in the medical, aerospace, energy, transportation, nuclear devices and fire safety. The necessity of adequate modeling of the thermomechanical behavior of the structural elements of the SMA.
Particular attention is paid to the experimentally observed tendency of thin-walled elements of the SMA to the loss of stability caused by phase and structural transformations, if the latter come under the action of compressive stresses. It was found that the known elastic stability analysis methods can lead to an overestimation of multiple experimental values of maximum loads items from SMA. Critically evaluate different concepts, to adequately describe this phenomenon. This concept of "fixed load" and "variable load", "ubiquitous additional phase and structural transition," "universal additional phase transition in the absence of structural transformation" and "ubiquitous additional structural transformation in the absence of an additional phase transition." Analyzed uncoupled, coupled and coupled twice statements stability problem for the elements of the SMA. The problem of influence of small temperature perturbations in the analysis of the stability elements of the SMA is considered. It is shown that the smallest critical load values that work best with the experimental data obtained in the framework of the concept of "variable load" and once connected setting that corresponds to the assumption of isothermal nature of buckling. The assumption of adiabatic nature buckling leads to some increase in the limit loads, which, however, are significantly inferior in magnitude Euler buckling loads even in the case of martensitic, i.e. the lowest values of the elastic moduli. The solutions of the problems of stability of rods, plates and shells of SMA and interpretation of these solutions in the context of real projects of practical use of these materials are considered.