The influence of “counter-body” stiffness on working parameters of niti actuator

Abstract The influence of the counter-body stiffness on the recovery stress, recoverable strain and work output variations during the thermal cycling of NiTi cylindrical samples in the actuator regime has been studied. Pre-deformed samples were connected by one side to a pendulum dynamometer with variable stiffness, which played the role of elastic counter-body, and the other sample side was fixed. Two schemes of pre-deformation under torsion mode were used: active deformation in martensite state, or cooling under constant stress. It was shown that the shape memory effect and recovery stress value depended non-linearly on stiffness values. Work output was calculated for all samples. The optimal interval of stiffness, which provided maximum output, was found in both preliminary deformation schemes used. It was shown that for samples deformed by cooling under constant stress, the values of shape memory effect, maximum recovery stress and work output were higher than for the samples pre-deformed in the martensite state. The shape memory effect, maximum recovery stress and work output values decreased on thermal cycling.