Deformation Behavior of Nanoscale Material Systems with Applications to Tensile, Flexural and Crack Propagation

R Mohan and Y Purohit and Y Liang, JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE, 9, 649-661 (2012).

DOI: 10.1166/jctn.2012.2075

Computational nanomechanics is an evolving field that investigates the deformation behavior of nanoscale structures. Due to the smaller lengths at the nano level, principles of mechanics are employed in conjunction with inter-atomic potentials, molecular forces and molecular dynamics. This paper highlights the underlying principles and discusses the tensile and flexural deformation of Nickel nanowires; and dynamic crack propagation in nanoscale Nickel (Ni) and Nickel-Aluminum (Al) bimetal interface. The tensile deformation behavior analysis indicates that Young's Modulus was independent of the cross sectional area of the nanowire, and the strain rate. The flexural deformation and vibration behavior indicates that the frequency of the vibrations of the Nickel nanowire beams is independent of the magnitude of external loading and is consistent with classical beam theory. The dynamic crack propagation behavior in a Nickel single crystal and a Nickel Aluminum bimetal interface are investigated. Our results for Ni show an initial brittle crack propagation followed by a roughening of the crack surfaces at one- third of the Rayleigh wave speed. In Ni Al, the crack surfaces initially grow brittle. Two regimes of crack propagation velocities were observed with crack getting decelerated as it nears the interface. Further dynamic analysis of the crack propagation indicated a cease in the crack propagation in Ni due to a brittle to ductile transition. In Ni Al bimetal interface system, as the crack approaches the interface, a process zone representing local disorder at the crack tip was observed to start growing and interacting with interfacial defects.

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