EXPERIMENTAL TESTING BENCH FOR THE DIAGNOSTICS OF PLASMA GENERATED BY PULSED GUNS WITH THE DIELECTRIC SURFACE BREAKDOWN

The experimental testing bench “ETB-PG” was designed to study the operation of plasma guns. The constructional design of plasma guns with replaceable dielectric operating on the surface sparkover basis has been proposed. Discharge currents and voltages under atmospheric and vacuum conditions have been determined. The two types of discharges were detected in the pressure range varying from the atmospheric value to 10-5 Torr. An experimental Paschen curve has been plotted. A statistical dependence of the types of discharges on the number of pulses, the pressure in the chamber, and the breakdown voltage has been established. The results of optical studies of the plasma flow generated by plasma guns in the vacuum of 2∙10-4 to 2∙10-5 Torr have been presented. The propagation velocity of the plasma flow in axial and radial directions has been measured. The glow time of the injected plasma was determined for different types of the discharges. The spectrograms of the composition and degree of the plasma ionization have been obtained.

Quantitative Measurements of Backside Wear in Acetabular Hip Joint Replacement: Conventional Polyethylene Versus Cross-Linked Polyethylene

As shown in previous studies, the modification of conventional polyethylene (CPE) to cross-linked polyethylene (XLPE) and the contribution of antioxidants result in a reduction in total wear. The aim of this study was to evaluate XLPE inserts with vitamin E and CPE regarding their resistance to the backside wear mechanism. A cementless hip cup system (Plasmafit® Plus 7, Aesculap) was dynamically loaded using CPE and XLPE inserts. The backside wear was isolated, generated and collected using the two-chamber principle. The chambers were filled with ultrapure water. After 2 × 106 cycles, the fluids were examined for wear particles according to a particle analysis. Using XLPE inserts, the backside wear was significantly reduced by 35%. While XLPE backside wear particles are significantly larger than CPE particles, they do not differ in their morphology. This study confirms the greater resistance to backside wear of XLPE compared to CPE. It can be assumed that the improved fatigue resistance of the vitamin E-stabilized XLPE inserts demonstrates XLPE’s effectiveness against micro-motion and the resulting changing tensions in interface areas like surface breakdown, pitting and the release of very small particles.

UV-cured nanocomposite coating for surface charging mitigation and breakdown strength enhancement: exploring the combination of surface topographical structure and perfluorooctyl chain

A facile method using a nanocomposite coating is proposed to suppress surface charge accumulation and enhance the surface breakdown strength of polymeric insulating materials like epoxy resin by covering a thin modified alumina flake/UV curable resin nanocomposite coating.

Improved Performance of Silicon Rubber Insulation With Coal Fly Ash Micro Filler

This paper presents the effect of coal fly Ash filler (CFA) on the electrical properties of silicon rubber composite. The observed electrical properties are volume resistance, surface resistance, and the surface breakdown voltage. The temperature The effect on the surface breakdown voltage of silicon rubber with CFA filler also was observed. The type of silicon used is RTV 683. The filler concentrations of the matrix are 0,​​10.20,30,40 per-hundred gram of resin (phr). The test results show that the surface resistance increased significantly with the increasing of CFA loading filler. The increasing of volume resistance is nonlinear; the volume resistance tends to decrease when the CFA loading filler exceeds 30 phr. Flashover test results show that flashover inception voltage (FOIV) increases with the increasing of CFA filler concentration and the increasing of temperature.