Statistical evaluation of hard-to-measure surfaces

The main goal of this article will be to find ways to evaluate hard-to-measure surfaces statistically. First, the basic characteristics and rules of surface quality will be described according to the standards ČSN EN 4287, ČSN EN 4288 and ČSN EN ISO 2517-2. Subsequently, the measured values of the roughness parameter Sa (arithmetic average of the height of the measured surface) and Sz (the maximum height of the measured surface) will be compared and evaluated which is the best. These parameters will be described and measured on aluminium plates on which the test surfaces were laser engraved. To evaluate the best surface, statistical methods will be used, such as the EDA methodology (exploratory data analysis), hypothesis testing with normality and outlier tests, and last but not least, cluster or cluster analysis, which compares the similarity of the measured data. This article aims to show the possibilities of surface quality assessment using 3D surface roughness parameters, which are not often used in practice

The effect of laser beam on the width of the cut

Conventional methods of dividing material due to their limitation to straight cuts have largely been replaced by non-conventional cutting methods, which include laser cutting. Laser cutting of polymer materials has become a priority for the manufacturing industry, mainly due to the constantly growing demand for these materials. The article discusses the effect of the laser beam on the width of the cut using lenses with different focal lengths, under different working conditions, on samples made of PMMA polymer material plates. For the experiment, the samples were produced using an ILS 3NM laser device, a CO2, with a wavelength of 10.6 μm and with maximum power 100 W, maximum feed speed 1524 mm · s-1. For the selected samples, it was studied how the dimension defined by the machining software differ from the dimension created by the machining

Optimization of REBCO Tapes through Division and Striation for Use in Superconducting Cables with Low AC Losses

This study aimed to enhance the performance of Ag-stabilized high-temperature superconducting (HTS) tapes with a focus on reducing magnetization losses. Two approaches were employed: dividing the tapes into narrower widths and introducing striation at the level of the superconducting layer. The process of laser ablation proved to be an effective method for implementing these modifications. The quality of the cut edges and grooves was assessed using scanning electron microscopy. To evaluate the electrical properties, measurements were conducted on the critical current and magnetization loss in samples at different stages: in their initial state, after cutting, and after the striation process. Of the two modifications, the striation process more effectively reduced the AC losses in the HTS tapes, approximately by one order of magnitude. The retention of critical current remained high after cutting, but varied with the number of created filaments after the striation process. Subsequently, a short cable was wound from the cut and striated HTS tape. This cable demonstrated a remarkable sixfold reduction in AC losses compared to the initial HTS tape