A major objective of the theory of defects is to relate the mechanical behaviour of macroscopic materials to the spatio-temporal evolution of the microstructure. The present paper deals with the dislocation-dynamical foundations of plastic instabilities and the propagation of slip in coherent plastic deformation modes (solitary plastic waves). Solitary waves arise from a proper balance between ...

A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a “small deformation” setting, a suite of simplified and interesting models consisting of a nonlocal Ginzburg Landau equation, a nonlocal level set equation, and a nonlocal generalized Burgers equation is derived. In the finite deformation setting, it is shown th...

A systematic study of the influence of plastic deformation and low temperature ageing on the carbon Dislocation Enhanced Finkelshtain Rosin Effect (DEFREIC) in austenitic alloys of Fe-Ni, Fe-Ni-MO, Fe-Mn-A1 and Fe-Cr-Ni systems with different carbon content is reported. The experiments prove that after plastic deformation at room temperature the FR effect is transformed into DEFREIC. nith both ...

The importance of fibre reinforced plastics continually increases due to the excellent mechanical properties, low material and manufacturing costs combined with significant weight reduction. Today, components are usually designed and calculated numerically by using finite element methods (FEM) to avoid expensive laboratory tests. These programs are based on material models including material sp...

In this paper, a methodology is presented for obtaining the plastic anisotropy of bulk metallic materials using cross-sectional indentation. This method relies on spherical indentation on the free edge of a specimen, and examining the out-of-plane residual deformation contour persisting on the cross-section after unloading. Results obtained from numerical simulation revealed that some important...

A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a ‘small deformation’ setting, a suite of simplified, but interesting, models, namely a nonlocal Ginzburg Landau, a nonlocal level set, and a nonlocal generalized Burgers equation are derived. In the finite deformation setting, it is shown that an additive decomp...

The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline Pd x Au1- x thin films. This combination enables direct imaging of...

Plastic deformation of materials occurs by the motion of defects known as dislocations and disclinations. High-resolution transmission electron microscopy was used to directly reveal the individual dislocations that constitute partial disclination dipoles in nanocrystalline, body-centered cubic iron that had undergone severe plastic deformation by mechanical milling. The mechanisms by which the...

We report in situ electron microscopy observations of the plastic deformation of individual nanometer-sized Au, Pt, W, and Mo crystals. Specifically designed graphitic cages that contract under electron irradiation are used as nanoscopic deformation cells. The correlation with atomistic simulations shows that the observed slow plastic deformation is due to dislocation activity. Our results also...

It is generally known that severe plastic deformation processes with back pressure not only apply higher hydrostatic stress and more deformation compared to what a regular process can apply to a workpiece but also prevent surface defects in the workpiece during the process. Hydrostatic cyclic expansion extrusion (HCEE) was developed recently for processing long ultrafine-grained metals and allo...