日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 2 (1990),
pp. 237-243

Influence of Elastic Anisotropy and Grain Size on Stress Distribution in β Phase Shape Memory Alloys

Hiroshi Nakamura1, Masashi Yokoyama2, Akikazu Nakagiri3 and Haruoki Maeda3

1Graduate Student, Kansai University, Osaka. Present address: Sumitomo Electric Industries Co., Ltd. Osaka
2Graduate Student, Kansai University, Osaka. Present address: Sumitomo Special Metals Co., Ltd., Osaka
3Department of Mechanical Engineering, Faculty of Engineering, Kansai University, Osaka

Abstract:

The influence of elastic anisotropy and grain size on the stress distribution in β phase shape memory alloys has been analyzed by the FEM (Finite Element Method) stress analysis.
Results of the analysis for the single crystals showed that the largest strains appeared upon deformation along <100> directions, while the smallest along <110> directions. This means that the strains depend on the orientation of deformation. The ratios of the maximum strain/the minimum strain for the single crystals increased with increasing anisotropy factor A =2 × C44/(C11-C12).
For the case of the bicrystals, consisting of grains with orientations φ1, and φ2, the calculated stress concentration factors α for the grain boundaries showed the maxima at {φ1, φ2) = (0, π/4) or (π/4, 0). The maximum values of stress concentration factor increased with increasing anisotropy factor.
For the case of the polycrystals, the variation coefficients (=the standard deviation/the average) for the Young's moduli and the stress concentration factors increased with increasing anisotropy factor. While the average of the Young's moduli and the stress concentration factors did not show clear dependence on grain size, their scatter increased with increasing grain size. This implies the existance of the large stress concentration along grain boundaries in the coarse-grained alloys.


(Received 1989/8/28)

Keywords:

shape memory alloys, elastic anisotropy, grain size, finite element method, stress analysis


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