本論文主要是使用霍普金森桿撞擊試驗機，於常溫(25℃)下以極高應變速率撞擊下，利用帽型試件(Hat-Shaped Specimen)測試不同晶粒尺寸之奈米結構316LVM不銹鋼之絕熱剪切變形行為。各於應變速率6 ×105s-1、8 ×105s-1和1 ×106s-1下進行試驗，藉由實驗所得之巨觀機械性質與和微觀破壞機制，以了解在極高應變速率下的動態剪切特性及剪切帶微觀組織(OM、SEM)之變化，以及晶粒尺寸對材料剪切變形行為有何影響。
實驗結果指出，應變速率及應變量對316LVM不銹鋼的巨觀機械性質影響甚鉅。試件遭受撞擊時，其塑流應力值隨著應變速率的增加而上升；然當塑流應力值達到最大值後，因為熱軟化之影響，會隨著應變量的增加而下降。316LVM不銹鋼的應變速率敏感性係數會隨應變速率之增加而上升，隨應變量之增加而下降。熱活化體積則隨著應變速率之增加而下降，隨應變量增加而增加。
在微觀方面，晶粒尺寸效應對316LVM不銹鋼剪切帶的生成及其剪切行為影響甚大。由光學顯微鏡之觀測，發現兩種晶粒尺寸之316LVM不銹鋼的絕熱剪切帶均為變態剪切帶，且剪切帶寬度隨應變速率增加而減小。剪切帶中心的局部應變量最大，隨著離開剪切帶的距離增加，局部應變量迅速減小。剪切帶鄰近區域的晶粒最小，隨著離開剪切帶的距離增加，晶粒尺寸也明顯增大。SEM破斷面分析發現兩種晶粒尺寸之316LVM不銹鋼破壞特徵為韌窩組織形貌，隨著應變速率增加，韌窩深度亦隨之增加。此外，破斷面上也觀察到節瘤狀形貌的存在，代表材料在塑性變的過程中曾發生熔化的現象。在兩種晶粒尺寸之316LVM不銹鋼的破斷面上並沒有觀察到任何的脆性劈裂形貌，顯示出這兩種晶粒尺寸之316LVM不銹鋼在極高速剪切荷載下仍然保持良好的塑變能力。

Adiabatic shearing behaviors under extremely high shear loading and microstructural characteristics of nanostructured 316LVM stainless steel with two different grain sizes are investigated under shear strain rates ranging from 6x105s−1 to 1x106s−1, using a compressive split-Hopkinson pressure bar. The results indicate that mechanical properties of 316LVM stainless steel are sensitive to strain rate. As strain rate increases, both flow stress and strain rate sensitivity rise first and then fall, while thermal activation volume decreases. However, at a constant strain rate, flow stress and strain rate sensitivity increase, yet thermal activation volume decreases with increasing grain size. Optical Microscope(OM) observations reveal that the width of adiabatic shear band decreases as strain rate increases. Size of grains nearby adiabatic shear bands is conspicuously smaller than that farther away from adiabatic shear bands, indicating the occurrence of recrystallzation. Cracks and voids are observed around and inside of the adiabatic shear bands. Furthermore, Scanning Electron Microscopy(SEM) observations show the existence of dimple and knobbly tissues, respectively suggesting ductile fracture and occurrence of melting of the material.

[1] M. A. Meyers, Dynamic behavior of materials. John wiley & sons, 1994.
[2] F. W. Metals, "World-class solutions in medical grade materials.."
[3] A. R. H. Bidhendi and M. Pouranvari, "Corrosion study of metallic biomaterials in simulated body fluid," Metalurgija, vol. 17, no. 1, pp. 13-22, 2011.
[4] A. Shahryari, S. Omanovic, and J. A. Szpunar, "Electrochemical formation of highly pitting resistant passive films on a biomedical grade 316LVM stainless steel surface," Materials Science and Engineering: C, vol. 28, no. 1, pp. 94-106, 2008.
[5] A. Shahryari, S. Omanovic, and J. A. Szpunar, "Enhancement of biocompatibility of 316LVM stainless steel by cyclic potentiodynamic passivation," Journal of Biomedical Materials Research Part A, vol. 89, no. 4, pp. 1049-1062, 2009.
[6] Z. Bou-Saleh, A. Shahryari, and S. Omanovic, "Enhancement of corrosion resistance of a biomedical grade 316LVM stainless steel by potentiodynamic cyclic polarization," Thin Solid Films, vol. 515, no. 11, pp. 4727-4737, 2007.
[7] Q. Pan, W. Huang, R. Song, Y. Zhou, and G. Zhang, "The improvement of localized corrosion resistance in sensitized stainless steel by laser surface remelting," Surface and Coatings Technology, vol. 102, no. 3, pp. 245-255, 1998.
[8] A. Shahryari and S. Omanovic, "Improvement of pitting corrosion resistance of a biomedical grade 316LVM stainless steel by electrochemical modification of the passive film semiconducting properties," Electrochemistry communications, vol. 9, no. 1, pp. 76-82, 2007.
[9] H. Kolsky, "An investigation of the mechanical properties of materials at very high rates of loading," Proceedings of the Physical Society. Section B, vol. 62, no. 11, p. 676, 1949.
[10] B. Butcher and C. Karnes, "Strain‐Rate Effects in Metals," Journal of Applied Physics, vol. 37, no. 1, pp. 402-411, 1966.
[11] F. E. Hauser, "Techniques for measuring stress-strain relations at high strain rates," Experimental Mechanics, vol. 6, no. 8, pp. 395-402, 1966.
[12] D. Steinberg, S. Cochran, and M. Guinan, "A constitutive model for metals applicable at high‐strain rate," Journal of Applied Physics, vol. 51, no. 3, pp. 1498-1504, 1980.
[13] C. Chiem and J. Duffy, "Strain rate history effects and observations of dislocation substructure in aluminum single crystals following dynamic deformation," Materials Science and Engineering, vol. 57, no. 2, pp. 233-247, 1983.
[14] J. Klepaczko, "Discussion of microstructural effects and their modelling at high rates of strain," in Conference series-Institute of physics, 1989, no. 102, pp. 283-298: Institute of Physics.
[15] T. Hong, T. Ogushi, and M. Nagumo, "The effect of chromium enrichment in the film formed by surface treatments on the corrosion resistance of type 430 stainless steel," Corrosion science, vol. 38, no. 6, pp. 881-888, 1996.
[16] C. Li and T. Bell, "Corrosion properties of active screen plasma nitrided 316 austenitic stainless steel," Corrosion Science, vol. 46, no. 6, pp. 1527-1547, 2004.
[17] R. R. Maller, "Passivation of stainless steel," Trends in Food Science & Technology, vol. 9, no. 1, pp. 28-32, 1998.
[18] J. Noh, N. Laycock, W. Gao, and D. Wells, "Effects of nitric acid passivation on the pitting resistance of 316 stainless steel," Corrosion science, vol. 42, no. 12, pp. 2069-2084, 2000.
[19] C.-C. Shih, C.-M. Shih, Y.-Y. Su, L. H. J. Su, M.-S. Chang, and S.-J. Lin, "Effect of surface oxide properties on corrosion resistance of 316L stainless steel for biomedical applications," Corrosion Science, vol. 46, no. 2, pp. 427-441, 2004.
[20] J. Polo, E. Cano, and J. Bastidas, "An impedance study on the influence of molybdenum in stainless steel pitting corrosion," Journal of Electroanalytical Chemistry, vol. 537, no. 1, pp. 183-187, 2002.
[21] U. Lindholm and L. Yeakley, "High strain-rate testing: tension and compression," Experimental Mechanics, vol. 8, no. 1, pp. 1-9, 1968.
[22] J. Achenbach, Wave propagation in elastic solids. Elsevier, 2012.
[23] B. Dodd, Adiabatic shear localization: occurrence, theories, and applications. Pergamon Press, 1992.
[24] W.-S. Lee and C.-F. Lin, "Plastic deformation and fracture behaviour of Ti–6Al–4V alloy loaded with high strain rate under various temperatures," Materials Science and Engineering: A, vol. 241, no. 1, pp. 48-59, 1998.
[25] M. Meyers, Shock waves and high-strain-rate phenomena in metals: concepts and applications. Springer Science & Business Media, 2012.
[26] U. Andrade, M. Meyers, K. Vecchio, and A. Chokshi, "Dynamic recrystallization in high-strain, high-strain-rate plastic deformation of copper," Acta metallurgica et materialia, vol. 42, no. 9, pp. 3183-3195, 1994.
[27] S. Nemat-Nasser, J. B. Isaacs, and M. Liu, "Microstructure of high-strain, high-strain-rate deformed tantalum," Acta Materialia, vol. 46, no. 4, pp. 1307-1325, 1998.
[28] M. A. Meyers, V. F. Nesterenko, J. C. LaSalvia, and Q. Xue, "Shear localization in dynamic deformation of materials: microstructural evolution and self-organization," Materials Science and Engineering: A, vol. 317, no. 1, pp. 204-225, 2001.
[29] A. Kumar, F. Hauser, and J. Dorn, "Viscous drag on dislocations in aluminum at high strain rates," Acta Metallurgica, vol. 16, no. 9, pp. 1189-1197, 1968.
[30] G. Leibfried, "Dislocations and mechanical properties of crystals," 1957.
[31] A. Seeger, "CXXXII. The generation of lattice defects by moving dislocations, and its application to the temperature dependence of the flow-stress of fcc crystals," The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, vol. 46, no. 382, pp. 1194-1217, 1955.
[32] H. Conrad, "Thermally activated deformation of metals," JOM, vol. 16, no. 7, pp. 582-588, 1964.
[33] W. Ferguson, A. Kumar, and J. Dorn, "Dislocation damping in aluminum at high strain rates," Journal of Applied Physics, vol. 38, no. 4, pp. 1863-1869, 1967.
[34] J. Campbell, "Dynamic plasticity: macroscopic and microscopic aspects," Materials Science and Engineering, vol. 12, no. 1, pp. 3-21, 1973.
[35] J. Campbell and A. Dowling, "The behaviour of materials subjected to dynamic incremental shear loading," Journal of the Mechanics and Physics of Solids, vol. 18, no. 1, pp. 43-63, 1970.
[36] D. Kim, S. Nemat-Nasser, J. Isaacs, and D. Lischer, "Adiabatic shearband in WHA in high-strain-rate compression," Mechanics of Materials, vol. 28, no. 1, pp. 227-236, 1998.
[37] D.-K. Kim, S. Lee, and W. H. Baek, "Microstructural study of adiabatic shear bands formed by high-speed impact in a tungsten heavy alloy penetrator," Materials Science and Engineering: A, vol. 249, no. 1, pp. 197-205, 1998.
[38] D. Shockey, "Materials aspects of the adiabatic shear phenomenon," in International Conference on Metallurgical Applications of Shock-Wave and High-Strain-Rate Phenomena(EXPLOMET85), 1985, pp. 633-656.
[39] C. Zener and J. H. Hollomon, "Effect of strain rate upon plastic flow of steel," Journal of Applied physics, vol. 15, no. 1, pp. 22-32, 1944.
[40] X. Teng, T. Wierzbicki, and H. Couque, "On the transition from adiabatic shear banding to fracture," Mechanics of Materials, vol. 39, no. 2, pp. 107-125, 2007.
[41] S. Timothy, "The structure of adiabatic shear bands in metals: a critical review," Acta metallurgica, vol. 35, no. 2, pp. 301-306, 1987.
[42] R. Batra and C. Kim, "Effect of thermal conductivity on the initiation, growth and bandwidth of adiabatic shear bands," International Journal of Engineering Science, vol. 29, no. 8, pp. 949-960, 1991.
[43] A. K. Zurek, "The study of adiabatic shear band instability in a pearlitic 4340 steel using a dynamic punch test," Metallurgical and Materials Transactions A, vol. 25, no. 11, pp. 2483-2489, 1994.
[44] Y. Xu, Y. Bai, Q. Xue, and L. Shen, "Formation, microstructure and development of the localized shear deformation in low-carbon steels," Acta materialia, vol. 44, no. 5, pp. 1917-1926, 1996.
[45] B. Dodd and Y. Bai, "Width of adiabatic shear bands," Materials Science and Technology, vol. 1, no. 1, pp. 38-40, 1985.
[46] D. Klahn, A. Mukherjee, and J. Dorn, "STRAIN-RATE EFFECTS," California Univ., Berkeley. Lawrence Radiation Lab.1970.
[47] A. T. Krawczynska, M. Lewandowska, and K. J. Kurzydłowski, "Recrystallization in nanostructured austenitic stainless steel," in Materials Science Forum, 2008, vol. 584, pp. 966-970: Trans Tech Publ.
[48] A. T. Krawczynska, M. Lewandowska, and K. J. Kurzydłowski, "Nanostructure formation in austenitic stainless steel," in Solid State Phenomena, 2008, vol. 140, pp. 173-178: Trans Tech Publ.
[49] Y. Huang, A. Pequegnat, J. Feng, M. Khan, and Y. Zhou, "Resistance microwelding of crossed Pt–10Ir and 316 LVM stainless steel wires," Science and Technology of Welding and Joining, vol. 16, no. 7, pp. 648-656, 2011.
[50] T. W. Wright and R. C. Batra, "The initiation and growth of adiabatic shear bands," International Journal of Plasticity, vol. 1, no. 3, pp. 205-212, 1985.
[51] T. W. Wright and J. W. Walter, "On stress collapse in adiabatic shear bands," Journal of the Mechanics and Physics of Solids, vol. 35, no. 6, pp. 701-720, 1987.
[52] U. Andrade, M. Meyers, and A. Chokshi, "Constitutive description of work-and shock-hardened copper," Scripta metallurgica et materialia, vol. 30, no. 7, pp. 933-938, 1994.
[53] J. Chen, L. Lu, and K. Lu, "Hardness and strain rate sensitivity of nanocrystalline Cu," Scripta Materialia, vol. 54, no. 11, pp. 1913-1918, 2006.
[54] E. Frutos, R. Martínez-Morillas, J. L. González-Carrasco, and N. Vilaboa, "Nanomechanical properties of novel intermetallic coatings developed on austenitic stainless steels by siliconisation in liquid phase," Intermetallics, vol. 19, no. 3, pp. 260-266, 2011.
[55] A. Bedford, A. Wingrove, and K. Thompson, "The phenomenon of adiabatic shear deformation," DTIC Document1973.
[56] K. Cho, Y. Chi, and J. Duffy, "Microscopic observations of adiabatic shear bands in three different steels," Metallurgical and Materials Transactions A, vol. 21, no. 5, pp. 1161-1175, 1990.
[57] Sandvik, "Datasheet-Sandvik-Bioline-316LVM."