The nanoscale anisotropic elastic-plastic behavior of single-crystal aragonite is studied using nanoindentation and tapping mode atomic force microscopy imaging. Force-depth curves coaxial to the axis exhibited load plateaus indicative of dislocation nucleation events. Plasticity on distinct slip systems was evident in residual topographic impressions where four pileup lobes were present after ...

Thin fi lms with microcrystalline and nanocrystalline grains are used in MEMS and thin fi lms for electronics. These systems have mechanical properties that depend on the microstructure. Grain size is frequently reported only as mean values or bounds. It has been demonstrated, however, that a mean grain size value is insuffi cient to describe the microstructure of these materials and the result...

A two-dimensional model composite with elastic reinforcements in a crystalline matrix subject to macroscopic shear is considered using both discrete dislocation plasticity and a nonlocal continuum crystal plasticity theory. Only single slip is permitted in the matrix material. The discrete dislocation results are used as numerical experiments and we explore the extent to which the nonlocal crys...

The cold compaction of an aggregate of powder is treated from the viewpoint of crystal plasticity theory. The contacts between particles are treated as compaction planes which yield under both normal and shear straining. The hardening of each plane represents both geometric and material hardening at the contacts between particles; the macroscopic tangent stiffness can be written in terms of the...

Under stress, crystals irreversibly deform through complex dislocation processes that intermittently change the microscopic material shape through isolated slip events. These underlying processes can be revealed in the statistics of the discrete changes. Through ultraprecise nanoscale measurements on nickel microcrystals, we directly determined the size of discrete slip events. The sizes ranged...

Nanoparticles in the range of 20 to 100 nm in size can be deposited, isolated, and individually probed for their mechanical properties. With a hypersonic plasma particle deposition technique, this has been successfully accomplished for silicon and titanium. We have already shown that silicon nanoparticles are superhard in the 30 to 50 GPa range after work hardening (Gerberich, W.W., Mook, W.M.,...