Dr. V. Prieb
Dilatometry of Shape Memory Alloys
by Viktor Prieb,
"MRS-Office Dr. Prieb"
at the TU-Berlin, Berlin, Germany, 2009
in the cooperation with
Andreas Zilly and Norbert Jost,
"Materials Development and Test Laboratory"
of the University Pforzheim, Pforzheim, Germany
Abstract: Three kind of shape memory-alloys (SMA?s) - single crystals Cu-Al-X
(X=Zn, Mn, Ni), and MnCu as well as TiNi-polycristals -
are investigated dilatometrically in the temperature interval of martensitic
Mechanisms of the dilatation effects in shape memory alloys are analyzed.
On that basis is an accommodation degree introduced. Its
values were calculated for all investigated SMA-samples: they lie in an interval
from 75% up to 99%.
Interrelation between thermal expansion of SMA's and
their physical (elasticity modulus), thermodynamical (entropy) and crystallographical (shear systems) characteristics
is treated theoretically and discussed.
The width extension of the thermal
hysteresis loops depending on the scanning rate is also investigated dilatometrically,
and a physical limiting of the work-frequency of SMA-actuators is proved and discussed.
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