  We report on experiments aimed at comparing the hysteretic response of a
Cu-Zn-Al single crystal undergoing a martensitic transition under strain-driven
and stress-driven conditions. Strain-driven experiments were performed using a
conventional tensile machine while a special device was designed to perform
stress-driven experiments. Significant differences in the hysteresis loops were
found. The strain-driven curves show re-entrant behaviour (yield point) which
is not observed in the stress-driven case. The dissipated energy in the
stress-driven curves is larger than in the strain-driven ones. Results from
recently proposed models qualitatively agree with experiments.
