Design for Brain Spatula Made by Precision-Cast Shape Memory Alloy

In order to develop a brain spatula made of a shape memory alloy (SMA), this paper discusses the bending characteristics of a new brain spatula precision-cast in a TiNi SMA. The results obtained can be summed up as follows. (1) Based on the yield stress and the modulus of elasticity of the copper and the TiNi SMAs, the bending deformation properties of the SMA-brain spatula were estimated. With respect to the SMA-brain spatula for the same length and width as the existing copper one, if the thickness of the conventional rolled-SMA spatula is 1.3 times as large as that of the existing copper-brain spatula, the SMA spatula can hold the same bending rigidity and can be bent by smaller force than the existing copper one. If the thickness of the new cast-SMA spatula is 1.2 times as large as that of the existing-copper spatula, the SMA spatula can hold the same bending rigidity and can be bent by the same force as the existing copper one. (2) With respect to the alternating- and pulsating-plane bending fatigue, the fatigue life of both the copper and the SMAs in the region of low-cycle fatigue is expressed by a power function of the maximum bending strain. The fatigue life of the conventional rolled SMA and the new cast SMA is longer than that of the existing copper. The fatigue life of the rolled SMA is longer than that of the cast SMA. The fatigue life of the new cast and rolled SMAs in the pulsating-plane bending is longer than that in the alternating-plane bending. The fatigue life of the rolled SMA and cast SMA for alternating- and pulsating-plane bendings can be expressed by the unified relationship with a power function of the dissipated work.