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The damping behaviour of superelastic NiTi components

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Bibliographic Details
Title: The damping behaviour of superelastic NiTi components
Authors: Schmidt, Ina ina.schmidt@unibw-hamburg.de, Lammering, Rolf1
Source: Materials Science & Engineering: A. Jul2004, Vol. 378 Issue 1/2, p70-75. 6p.
Subjects: Alloys, Damping (Mechanics), Elasticity, Steel
Abstract: A set of experimental investigations on the transformation behavior of superelastic NiTi components has been undertaken with respect to damping. Tensile tests have shown, that the beginning of the transformation is shifted to lower stresses with increasing frequency. Therefore dynamic loads can give rise to considerable damping even if the load is below the level of the transformation–stress plateau in the quasistatic case. However it has to be taken into consideration that the amount of transformed material is much lower than in the plateau-region and the dissipated energy decreases with increasing frequency. For an estimation of the attainable damping capacity, experiments on a pre-strained string were performed to enable a comparison of the damping ratios of NiTi elements at different stages of transformation. An increase of amplitudes leads to higher damping values for NiTi in the plateau-region, while in the completely transformed stage NiTi exhibits an amplitude-independent damping behaviour with values that are smaller than those observed in experiments with steel. Further experiments have been performed with coil springs made from NiTi. Again increasing pre-stress as well as an increasing vibration amplitude lead to a stronger damping of the NiTi springs and the vibrating system. The calculated damping values from the performed experiments are result of a linear analysis. [Copyright &y& Elsevier]
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Database: Engineering Source
Description
Abstract:A set of experimental investigations on the transformation behavior of superelastic NiTi components has been undertaken with respect to damping. Tensile tests have shown, that the beginning of the transformation is shifted to lower stresses with increasing frequency. Therefore dynamic loads can give rise to considerable damping even if the load is below the level of the transformation–stress plateau in the quasistatic case. However it has to be taken into consideration that the amount of transformed material is much lower than in the plateau-region and the dissipated energy decreases with increasing frequency. For an estimation of the attainable damping capacity, experiments on a pre-strained string were performed to enable a comparison of the damping ratios of NiTi elements at different stages of transformation. An increase of amplitudes leads to higher damping values for NiTi in the plateau-region, while in the completely transformed stage NiTi exhibits an amplitude-independent damping behaviour with values that are smaller than those observed in experiments with steel. Further experiments have been performed with coil springs made from NiTi. Again increasing pre-stress as well as an increasing vibration amplitude lead to a stronger damping of the NiTi springs and the vibrating system. The calculated damping values from the performed experiments are result of a linear analysis. [Copyright &y& Elsevier]
ISSN:09215093
DOI:10.1016/j.msea.2003.09.106