Plastic deformation of crystalline materials is a complex nonhomogeneous process characterized by avalanches in the motion of dislocations. We study the evolution of dislocation loops using an analytically solvable phase-field model of dislocations for ductile single crystals during monotonic loading. The distribution of dislocation loop sizes is given by P(A) approximately A-sigma, with sigma=...

Numerical models of deformation, damage and fracture in particle-reinforced composite materials, based on the method of multiphase ®nite elements (MPFE) and element elimination technique (EET), are presented in this paper. The applicability of these techniques for di€erent materials and di€erent levels of simulation was studied. The simulation of damage and crack growth was conducted for severa...

B. Ahn*, S. R. Nutt 1. Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089-0241, USA *[email protected] Abstract: Al–Mg alloy powder was mechanically milled in liquid N2 (cryomilling) to produce thermally stable powder with nanocrystalline (NC) microstructure for the manufacture of highstrength alloys. A multi-scale microstructure w...

ANALYSIS of the deformation field consistent with a Prandtl stress distribution travelling with an advancing plane-strain crack reveals the functional form of the near tip crack profile in an elastic-plastic solid. The crack opening 6 is shown to have the form 6 N r In (const./r) at a distance r from the tip. This observation coupled with data generated from finite element investigations of gro...

[1] We demonstrate that deformation of partially molten ductile rocks can produce melt segregation by two-phase flow. In simple shear experiments on several melt-rock systems at high temperature and pressure, melt segregates into distinct melt-rich layers oriented 20 to the shear plane. Melt segregates in samples in which pressure gradients can develop at length scales less than the sample thic...

As part of this continuing DMI-funded NSF project, a novel, efficient and mathematically rigorous continuum based sensitivity method is being developed that can be used to accurately evaluate the gradients of the objective function and constraints in the design optimization of multi-stage deformation processes. The sensitivity methods developed allow for a unified treatment of both shape and pa...

Deep in the Hellas basin on Mars, wind has exhumed layered terrain showing ductile deformation. A kilometer-scale cellular pattern is identified, consistent with thermal and/or compositional (diapiric) convection. ‘Frozen-in’ convection within an impact melt sheet is consistent with observations, but overturn(s) within an evaporitic layer cannot be excluded. Spectrometer follow-up will be compl...

Earlier [ 1] we described an experimental procedure aimed at exarnining the spatial and temporal distribution of energy dissipation during crack initiation and propagation in a ductile polymer. The experiment combines a table-top tensile tester and an infrared imaging system. Because of the intense heating of the crack tip region, direct observation of the temperature rise not only provides an ...

Metallic glasses are commonly brittle, as they generally fail catastrophically under uniaxial tension. Here we show pronounced macroscopic tensile plasticity achieved in a La-based metallic glass which possesses strong β relaxations and nanoscale heterogeneous structures. We demonstrate that the β relaxation is closely correlated with the activation of the structural units of plastic deformatio...

_Abstract. Two major hypotheses have been advanced for the formation of the long wavelength (100-300 km) undulations of oceanic basement and overlying sediments developed in the central Indian Ocean basin: whole layer folding (buckling) and local thickening (inverse boudinage). Using appropriately scaled two-layer analogue models for the oceanic lithosphere comprising a brittle layer above a du...