PSI - Issue 2_A

Takashi Sumigawa et al. / Procedia Structural Integrity 2 (2016) 1375–1382 Author name / Structural Integrity Procedia 00 (2016) 000–000

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constants of each grain were determined on the basis of the elastic constants in a single crystal ( C 11 = 168.0 GPa, C 12 = 75.4 GPa, C 44 = 121.0 GPa). On the basis of the displacement amplitude at the generation of slip bands, the critical resolved shear stress amplitude Δτ crss /2 to generate slip bands was evaluated to be approximately 300-400 MPa, which was much higher than that of PSB formation in Cu bulk single crystal (27 MPa [Melisova et al. (1997)]). 4. Conclusion A resonance fatigue experiment was conducted using a Si/Ti/Cu/SiN cantilever nano-material to examine the fatigue damage in nano-polycrystalline Cu under fully reverse loading. The results are summarized as follows. 1. The resonance frequency of the cantilever specimen was successfully reduced by attaching a Au weight to the test part end. 2. At an input voltage amplitude of Δ V in /2≤1.0 V, Δ δ 1 /2 and f 0 were unchanged until 10 7 cycles. However, Δ δ 1 /2 dropped significantly before 10 7 cycles at Δ V in /2 = 1.60 V. The sudden drop is due to the change in f 0 associated with the formation of fatigue damage. 3. Slip bands with a width of a few tens of nanometers were generated in a grain in the nano-polycrystalline Cu layer after the sudden drop of Δ δ /2. Although extrusions/intrusions were observed in the slip bands, the sizes were significantly smaller. 4. The stress concentration induced by the collision of an extrusion with a grain boundary generated a crack along the grain boundary. Acknowledgements This work was supported in part by Grants-in-Aid for Young Scientists (A) (No. 24686018), Scientific Research (A) (No. 15H02210), Specially Promoted Research (No. 25000012), and Challenging Exploratory Research (No. 26630009) from the Japan Society for the Promotion of Science (JSPS). References Basinski, Z.S., Korbel A.S., Basinski S.J., 1980. The temperature dependence of the saturation stress and dislocation substructure in fatigued copper single crystals. Acta Metallurgica 28, 191-207. Basinski, Z.S., Pascual, R., Basinski, S.J., 1983. Low Amplitude Fatigue of Copper Single Crystals-I. The Role of the Surface in Fatigue Failure. Acta Metallurgica 31(4), 591-602. Basinski, Z.S., Basinski, S.J., 1992. Fundamental aspects of low amplitude cyclic deformation in face-centered cubic crystals. Progress in Materials Science 36, 89-148. Budiman, A.S., Han, S.M., Greer, J.R., Tamura, N., Patel, J.R., Nix, W.D., 2008. A search for evidence of strain gradient hardening in Au submicron pillars under uniaxial compression using synchrotron X-ray microdiffraction. Acta Materialia 56, 602-608. Greer, J.R., Oliver, W.C., Nix, W.D., 2005. Size dependence of mechanical properties of gold at the micron scale in the absence of strain gradients. Acta Materialia 53, 1821-1830. Greer, J.R., Nix, W.D., 2006. Nanoscale gold pillars strengthened through dislocation starvation. Physical Review B 73, 245410. Grosskreutz, J.C., Mughrabi H., 1975. in “ Constitutive equations in plasticity ”. In: Argon, A.S. (Ed.). Cambridge, MA: MIT Press. Kraft, O., Schwaiger, R., Wellner, P., 2001. Fatigue in thin films: lifetime and damage formation. Materials Science and Engineering A 319-321, 919-923. Laird, C., 1986. Low energy dislocation structures produced by cyclic deformation. Materials Science and Engineering 81(1), 433-450. Laufer, E.E., Roberts, W.N., 1966. Dislocations and Persistent Slip Bands in Fatigued Copper. Philosophical Magazine 14(127), 65-78. Lukas, P, Klesnil M, Krejci J., 1968. Dislocations and Persistent Slip Bands in Copper Single Crystals Fatigued at Low Stress Amplitude. Physica Status Solidi 27, 545-558. Melisova, D., Weiss, B., Stickler, R., 1997. Nucleation of persistent slip bands in Cu single crystals under stress controlled cycling. Scripta Metallurgica 36, 1061-1066. Mughrabi, H., 1983. Dislocation wall and cell structures and long-range internal stresses in deformed metal crystals. Acta Metallurgica 31(9), 1367-1379. Mughrabi, H., 1978. The Cyclic Hardening and Saturation Behaviour of Copper Single Crystals. Materials Science and Engineering 33, 207-223. Mughrabi, H., 1980. in “ Strength of metals and alloys ”. In: Haasen, P., Gerold, V., Kostorz, G. (Eds.). Oxford: Pergamon Press. Read, D.T., 1998. Tension-tension fatigue of copper thin films. International Journal of Fatigue 20(3), 203-209. Schwaiger, R., Dehm, G., Kraft, O., 2003a. Cyclic deformation of polycrystalline Cu films. Philosophical Magazine 83(6), 693-710.