A. Schaefer, Ruhr-University Bochum, Bochum, Germany; G. Eggeler, M. F. -. X. Wagner, Ruhr University Bochum, Bochum, Germany
Pseudoelastic NiTi exhibits a localized, stress-induced martensitic transformation. Austenitic and martensitic regions are separated by narrow interfaces with a finite width, which propagate through the specimen upon uniaxial straining. All deformation occurs exclusively in the interface region. In the present study, in-situ digital image correlation is used to investigate the local strain- and strain rate-fields in the vicinity of propagating interfaces. The effect of specimen geometry on interface shape (i.e., characteristic angle of inclination with respect to the tensile axis, width of the interface) and strain states is investigated by comparing wire and ribbon specimens (with circular and rectangular cross section, respectively). Furthermore, the relation between the enforced displacement rate, interface velocity, release of latent heat and critical transformation stress is highlighted, providing a full picture of the local thermo-mechanical loading conditions.
Summary: We investigated the influence of specimen geometry on the shapes of the martensite/austenite interfaces and the strain states in pseudoelastic NiTi using digital image correlation. Furthermore, the relation between the enforced displacement rate, interface velocity, release of latent heat and critical transformation stress is highlighted, providing a full picture of the local thermo-mechanical loading condition.
