We propose a three-dimensional level set method for dislocation dynamics in which the dislocation lines are represented in three dimensions by the intersection of the zero levels of two level set functions. Since the level set method does not discretize nor directly track individual dislocation line segments, it easily handles topological changes occurring in the microstructure. The dislocation...

A framework for investigating plasticity phenomena and their dependence on the underlying physical and size-dependent mechanisms is developed. The framework is based on crystal plasticity and three-dimensional discrete dislocation dynamics analyses. Particularly, the mesoscale model couples continuum crystal plasticity framework with a set of spatio-temporal evolution equations for dislocation ...

Grain boundaries (GBs) provide a strengthening mechanism in engineering materials by impeding dislocation motion. In a polycrystalline material, there is a wide distribution of GB types with characteristic slip transmission and nucleation behaviors. Slip–GB reactions are not easy to establish analytically or from experiments; furthermore, there is a strong need to quantify the energy barriers o...

Using a concurrent multiscale approach we demonstrate that the local environment of transition-metal solutes in refractory bcc metals has a large effect on the mobility and slip paths of dislocation. The results reveal that solid solutes or nanoclusters of different geometries may lead to solid-solution hardening or softening, in agreement with experiment, including spontaneous dislocation glid...

We identified a strong temporal correlation between three distinct types of slow earthquakes distributed over 100 kilometers along the dip of the subducting oceanic plate at the western margin of the Nankai megathrust rupture zone, southwest Japan. In 2003 and 2010, shallow very-low-frequency earthquakes near the Nankai trough as well as nonvolcanic tremor at depths of 30 to 40 kilometers were ...

In this work, Ti–23Nb–0.7Ta–2Zr (TNTZ) and gum metal Ti–23Nb–0.7Ta–2Zr–1.2O (TNTZ-O) alloys were synthesized by cold crucible levitation melting with the objective of investigating the influence of oxygen on the deformation mechanisms. By tensile tests, electron backscatter diffraction, atomic force microscopy and transmission electron microscopy analyses, we showed that the deformation in the ...

Seismic reflection profiles, drill-hole data, and geologic maps delimit the form of normal faults and Tertiary sedimentary rocks in the southern half of the Cache Valley basin in northern Utah. Dips of faults and sedimentary rocks were estimated from time-migrated reflection profiles by using the stacking velocities for the data. At the southern end of the basin, the East Cache fault zone is li...

Transmission electron microscopy (TEM) and KOH etching have been used to study the dislocation structure of 4H SiC wafers grown by physical vapor transport. A new type of threading dislocation arrays was observed. Rows of etch pits corresponding to dislocation arrays were observed in vicinity of micropipes, misoriented grains and polytypic inclusions at the periphery of the boules and extended ...

Twinning is a fundamental deformation mode that competes against dislocation slip in crystalline solids. In metallic nanostructures, plastic deformation requires higher stresses than those needed in their bulk counterparts, resulting in the 'smaller is stronger' phenomenon. Such high stresses are thought to favour twinning over dislocation slip. Deformation twinning has been well documented in ...