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The analysis of EDM electrodes wear in corners and edges

Mouralova K., Bednar J., Benes L., Hrabec P., Kalivoda M., Fries J.

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

484--497

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear.

Formation of micelles by hydrophobically modified poly(allylamine hydrochloride)

Wytrwal M., Sarna M., Bednar J., Kozik B., Nowakowska M., Kepczyński M

Polish Journal of Applied Chemistry

2011

Vol. 55, nr 1

11-17

The aim of this study was to transform commercially available poly(allylamine hydrochloride) (PAH) into hydrophobically modified strong polyelectrolytes. It was accomplished by reductive amination using hexanal or octanal followed by exhaustive methylation with methyl iodide leading to quaternary ammonium salts. Chemical structures of the obtained polycations and the degrees of substitution with hydrophobic chains were confirmed using spectroscopic methods and an elemental analysis. The structures formed by the modified polymers in aqueous solution were determined using zeta potential measurements, dynamic light scattering (DLS) technique and cryogenic transmission electron microscopy (cryo-TEM). The morphology of the polymer films deposited on a silicon surface was studied using atomic force microscopy (AFM). The microscopic observation confirmed the formation of polymeric micelles with sizes dependent on length of alkyl chains attached to the polycation backbone.