On the viscous and strain rate dependent behavior of polycrystalline NiTi

The viscous and rate dependent behavior of binary, pseudoelastic NiTi is investigated. The main focus is on the decoupling of thermal and viscous effects on the transformation stress level as the specimen material is subject to heating and cooling due to latent heat generation and absorption during phase transition. On this account, an active temperature control is proposed to account for swift temperature variations. In addition to uniaxial testing of the shape memory sample, two-dimensional tension/torsion experiments are conducted in order to generalize the uniaxial findings. Therefore, a two-dimensional strain measuring device is realized, which is capable of measuring large angle strains. Furthermore, the relaxation behavior of the examined NiTi alloy is explored as well. (c) 2007 Elsevier Ltd. All rights reserved.