Computational and experimental analyses of martensitic transformation propagation in shape memory alloys

This study investigates the creation of heterogeneous martensitic transformation field in shape memory alloy structures with geometrical nonuniformity through experiments and finite element computational analysis. Geometrically graded superelastic NiTi thin plates with series and parallel design configurations with respect to the loading direction have been created. The nonuniform transformation evolutions within these structures are presented by thermal images captured by an infrared camera during tensile experimentation. It is found that the transformation propagation is along the loading direction in a sample with the series design configuration unlike that in a sample with the parallel design configuration. Also, the geometrically graded structures exhibit stress gradient over stress-induced transformation. The transformation propagation and the deformation behaviour of these structures are presented by numerical modelling which is in good agreement with experimental data.