II. PHENOMENOLOGY OF PLASTIC DEFORMATION When a body is exposed to external stress, it responds either by moving, or by deforming. Depending on the magnitude of the stresses applied, there are two types of possible deformations 1) For low stresses, the strain is proportional to the applied stress (Hooke’s law) and comes back to its original position when the stress is removed. This is called el...

Design of structures needs to cater to key requirements of safety and weight. To achieve these requirements, smooth flow of stresses and optimum factor of safety at all points in the structure are necessary. However, presence of cut outs becomes a necessary feature in the structures which obstruct the flow of stresses and there will be local concentration of stresses near the cut outs which nee...

A new physical mechanism of plastic deformation in nanowires is suggested and theoretically described. This mechanism represents formation of near-surface nanodisturbances-nanoscopic areas of plastic shear with tiny shear vectors-in deformed nanowires. We calculated the energy characteristics for nanodisturbance formation and compared them with those for conventional dislocation generation. It ...

The elastic coupling between plastic events is generally invoked to interpret plastic properties and the failure of amorphous soft glassy materials. We report an experiment where the emergence of a self-organized plastic flow is observed well before the failure. For this we impose an homogeneous stress on a granular material, and measure local deformations for very small strain increments using...

A method of measuring biaxial stress-strain curves for sheet metal samples subjected to large plastic strains is described for one example aluminum alloy (AA 5754-O). The method uses a portable X-ray diffraction (XRD) system to measure in situ stresses during tensile deformations. Calibration of X-ray elastic constants and the effects of texture and intergranular stresses are discussed. Uniaxia...

Pattern transformation in periodic microporous elastoplastic solid coatings is caused by a buckling of the struts and a rotation of the nodes under compressive stresses. The results of a nonlinear numerical investigation confirm the critical role of the bifurcation of the periodic solid under compressive stresses. In striking contrast to the earlier observations of elastic instabilities in poro...