Is Stress Concentration Relevant for Nanocrystalline Metals?

• DOI: 10.1021/nl201083t
• Publication Date: 2011-05-18T20:39:19Z
• Authors: Sandeep Kumar; Xiaoyan Li; Aman Haque; Huajian Gao
• Keywords: Nanocrystalline material

Classical fracture mechanics as well modern strain gradient plasticity theories assert the existence of stress concentration (or gradient) ahead a notch tip, albeit somewhat relaxed in ductile materials. In this study, we present experimental evidence extreme homogenization nanocrystalline metals that result immeasurable amount at tip. We performed situ uniaxial tension tests 80 nm thick (50 average grain size) freestanding, single edge notched aluminum specimens inside transmission electron microscope. The theoretical for given geometry was high 8, yet diffraction patterns unambiguously showed absence any measurable To identify possible mechanisms behind such an anomaly, molecular dynamics simulations on scaled down samples. Extensive rotation driven by boundary diffusion, exemplified Ashby–Verrall type switching process, observed tip to relieve concentration. conclude dislocations, realignment or may have played critical role accommodating externally applied and neutralizes during process.