Deformation and Fracture at the Micron and Nano Scales

The progressively increasing demands of new science and technology to understand the behavior of materials/components and processes at the micrometer and nanometer regimes has led in the mid seventies to the development of

micromechanics

. In the mid nineties a new term

nanomechanics

was used by the author to indicate the forthcoming excessive activity in this field and point out to the need for new constitutive equations and mechanics tools to be developed in relation to the emerging fields of

nanotechnology

. In fact, it was only a few years earlier, that the first

carbon nanotubes

were produced in Japan - a unique example for the use of elasticity theory at the nanoscale - and the first bulk

nanopolycrystals

were produced in Russia. At the same time the first experimental observations on deformation and fracture mechanisms of nanopolycrystalline thin films were reported by the author and his co-workers in US. It was reported, among other things, that plastic deformation at the nanoscale does not take place through lattice dislocation activity but through grain boundary processes including material rotation and mass diffusion. Moreover, fracture processes occur through nanovoid nucleation and coalescence. Some of these experimental observations were numerically verified a few years later through molecular dynamics (MD) multimillion atom simulations.