The DC electropolishing process has been applied to the sharpening of tungsten wires in 2 M KOH aqueous solution. Necking of tungsten anodes takes place in the vicinity of the electrolyte-air interface. This results in the creation of two separate wire parts with nanosharp tips. Using image analysis, we demonstrate that the products of electrochemical reactions on the wire surface form a film w...

In Incremental Sheet Forming (ISF) strains can be obtained well above the Forming Limit Curve (FLC) that is applicable to common sheet forming operations like deep drawing and stretching. This paper presents an overview of mechanisms that have been suggested to explain the enhanced formability. The difference between fracture limit and necking limit in sheet metal forming is discussed. The neck...

Periodic bifurcation modes that occur in ductile multilayered plates or sheets stretched in plane strain tension are analyzed to reveal whether necks are likely to localize at the scale of the thickness of individual layers or at the scale of the full thickness of the multilayer. The energy dissipated in tearing a ductile multilayer scales with the extent of the localized thinning region in the...

In this paper instability of planar anisotropic sheet metal during a few forming processes is investigated for the first time. For this reason components of the constitutive tangent tensor for planar anisotropic sheets are developed. By using the above tensor location of necking is predicted. Direction of the shear band is also predicted using the acoustic tensor. A finite element program is pr...

Abstract The purpose of the experiment described herein is the study of material deformation (here a cylinder) induced by explosives. During its expansion, the cylinder (initially 3 mm thick) is thinning until fracture appears. Some tens of microseconds before destruction, strain localizations occur and induce mechanical necking. To characterize the time of first localizations, 25 stereoscopic ...

We apply continuum mechanical based, numerical modeling to study the dynamics of extended monodisperse polymer melts during the relaxation. The computations are within the ideas of the microstructural "interchain pressure" theory. The computations show a delayed necking resulting in a rupture, as a result of small initial sample imperfections. These ruptures agree with experimental observations.

The failure process ahead of a mode I crack advancing in a ductile thin metal plate or sheet produces plastic dissipation through a sequence of deformation steps that include necking well ahead of the crack tip and shear localization followed by a slant fracture in the necked region somewhat closer to the tip. The objective of this paper is to analyze this sequential process to characterize the...