3. The elongation and reduction of area increased markedly with increasing strain rate, and these dependencies were linear. Although strain rate dependencies in the elongation and reduction of area were negligible up to the strain rate of approximately 100s-1, the degree of rate sensitivity appears to increase rapidly for the higher strain rates. 4. Although the fracture surfaces mainly exhibited the shear type dimple pattern under the low strain rates, ordinary equiaxed dimple fracture surfaces were observed under the high strain rates. The specimen was remarkably necked at the high strain rate. In both materials, the dimple size and depth increased as the strain rate increased. REFERENCES 1. Nicholas, T. (1981) Exp. Mech., 21, 177. 2. Lindholm, U. S. (1964) J. Mech, Phys. Solids, 12, 317. 3. Perzyna, P. (1974). In: Mechanical Properties at High Rates of Strain, pp. 138-153, Harding, J.(Ed). Inst. Phys., Oxford. 4. Sugiura, N., Kobayashi, T., Yamamoto, I., Nishido, S. and Hayashi, K. (1995) J. J. Inst. Light Met., 45, 633. 5. Sun, Z. M., Kobayashi, T., Fukunasu, H., Yamanoto, I. and Shibue, K. (1998) Metall. Mater. Trans. A, 29A, 263. 6. Masuda, T., Kobayashi, T. and Toda, H., Submitted to J. J. Inst. Light Met.. 7. Yokoyama, T. (1996) J. Soc. Mat. Sci., 7, 785. 8. Mukai, T., Higashi, K., Tuchida, S. and Tanimura, S. (1993) J. Inst. Light Met., 43, 252.
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