Influence of Grain Shape in Grinding Wheels on the Machining Quality of Bearing Rings

The quality of grinding of bearing races is related to their performance and durability. The aim of this work is to establish how the machining quality of bearing rings depends on the characteristics of grinding wheels, in particular, on such a parameter as the shape of abrasive grains. Several batches of experimental grinding wheels were made, containing grains of different shapes (from isometric to lamellar varieties). Quantitatively, the shape of the grains was estimated by the shape factor parameter (SF), which is equal to the ratio of the diameters of inscribed and circumscribed circles in the contours of the used grains. The shape factor was determined using a scanner or a digital microscope and a special computer program. The tests were carried out on circular, plunge, and finishing grinding, using coolant, on a SIW 4E machine in a bearing factory. The machining quality of the bearing rings was assessed by studying the microstructure, microhardness and roughness of their bearing races. The durability of grinding wheels was determined by the number of machined rings before maximum tool wear. It has been established that by a differentiated approach to the choice of grain shapes in the wheel, it is possible to significantly increase its operational capabilities: increase the microhardness of the ground surfaces, reduce the roughness of processing, and increase the durability of grinding wheels.

THE USE OF A DIGITAL MICROSCOPE FOR THE DEVELOPMENT OF YOUNG SCHOOLCHILDREN'S IDEAS ABOUT PLANTS, ANIMALS AND FUNGI

At present the use of technical teaching aids based on digital technologies in the educational process in primary schools is gaining special relevance, and the digital microscope is indicated in a number of syllabi for the course "Nature study" in primary schools in the section “Material and technical support”. The teacher is free to decide on what topics, in the study of what objects or natural phenomena, with the use of what methods to use this teaching tool. The aim of the study is to identify the influence of the use of the digital microscope on the development of children’s ideas about plants, animals and fungi in primary school. The pedagogical experiment was carried out for 2 years on the basis of two secondary schools in the city of Kirov, Russian Federation. 140 third grade students (72 students in the experimental group and 68 students in the control group) took part in the experiment. For the development of ideas about plants, animals and fungi in primary school children at Nature study lessons two methods were implemented: with the use of the digital microscope (in the experimental group) and without its use (in the control group). The results of testing third-graders before and after the teaching experiment showed that the use of the digital microscope in the classroom contributed to students’ better assimilation of knowledge about the diversity of plants, their respiration, nutrition, reproduction and development, the diversity of animals, their reproduction and development, and the diversity of fungi than in the lessons which did not use the microscope. This is proved by statistically significant differences in the test results of the experimental and control groups after the experiment. The findings of the study can provide a starting point for subject curriculum developers and teachers interested in using the digital microscope in primary school education.

Microplastic in Water and Sediments at the Confluence of the Elbe and Mulde Rivers in Germany

Accumulation of microplastics in aquatic environments is an issue of emerging concern. Initially, research focused on marine systems. However, recent studies also investigate the abundance of microplastics in freshwater environments. Rivers connect terrestrial with marine ecosystems and contribute a considerable share of macro- and microplastics to the oceans. A previous study found a large amount of micro-spheres in Dessau downstream the river mouth of the Mulde. Therefore, the objective of this research was to examine whether the Mulde river with its highly industrialized catchment contributes to the microplastic pollution of the Elbe. Sediment (Van Veen grab sampler) and water samples (filter cascade with the smallest mesh size 50 μm and nets with the smallest mesh size 150 μm) were taken from the Elbe river up- and downstream the confluence with the Mulde. After extensive sample preparation, we examined the samples under a digital microscope and determined polymer types by pyrolysis Gas Chromatography/Mass Spectrometry (pyr-GC-MS). The amount of primary microplastics increased in sediment and water samples just downstream the confluence. Those microplastics originate probably from the Mulde. We measured larger amounts and different shapes of microplastics in filter cascades that have a smaller mesh size compared to the nets.

Modification of Surface Structure by Diffusion Processes

In the paper an effect of a diffusion technology such as gaseous ferritic nitrocarburizing on the surface properties of selected alloyed case-hardening steel was tested. The steel 18CrNiMo7-6, primarily predetermined for carburizing and frequently utilized in manufacturing of highly strained components, where high core tensile strength as well as hard surface is demanded, was exposed to gaseous ferritic nitrocarburizing. Such treated surface was subjected to experimental methods. The microstructure observation and the determination of the white layer thickness was performed on the Opto-digital microscope Olympus DSX500i. The nitriding hardness depth of the surface layer from the microhardness profiles obtained by the microhardness tester LM247 AT LECO was deduced. The wear resistance was assessed by utilizing the Scratch test method performed on the tribometer Bruker UMT-3 TriboLab. Results of the measurements present an effect of gaseous ferritic nitrocarburizing on the surface properties of the steel 18CrNiMo7-6 and provide a perception of possibility to substitute the frequently utilized carburizing by the gaseous ferritic nitrocarburizing.

Analytical Study and Conservation of New Kingdom Period Pottery Jars from Saqqara Excavation, Egypt

Ancient archaeological sites contain numerous pottery objects that suffered from different deterioration factors. This study aims to use different analytical methods to study the chemical and mineralogical composition and identification of deterioration aspects of some ancient Egyptian pottery jars from Saqqara excavation. Thus, to explain the deterioration factors' mechanisms and apply the proper conservation methods to the deteriorated pottery jars. AutoCAD, digital microscope, scanning electron microscope (SEM-EDX), and x-ray diffraction (XRD) were used to clarify the preservation states of pottery jars. The results of the investigation revealed that the selected jars suffered from different cracks, salts crystallization, some surface black spots, separation of the slip layer, and heterogeneity in the grains size. XRD analysis revealed that quartz, diopside, illite, muscovite, orthoclase, anorthite, and hematite are the main components of the jars. SEM-EDX analysis showed high concentrations of chlorides and sulfate salts, besides the presence of manganese oxide. Different treatments were performed for the pottery jars include mechanical and chemical cleaning. Additionally, the completion process was done by using a mixture of dental gypsum with grog. Moreover, the consolidation process was achieved by using paraloid B-72.

Mechanism of Cavitation Wear of a Low-Friction Composite Coating CrN+WC/C Deposed on Ferritic-Pearlitic P265GH and Austenitic X2CrNi18-9 (304L) Steels

In order to meet the expectations of the global industry in areas such as: energy, heating, aviation, automotive, railway, chemical, petrochemical, oil, gas, river and marine sectors, where material wear processes may occur due to the flow of water gas and steam or their mixtures with various degree of saturation at different pressures, the authors of this article have conducted research on the resistance to cavitation wear of a low-friction composite anti-wear PVD coating in the form of chromium nitride and tungsten carbide (CrN+WC/C) deposited by a physical method on the surface of structural elements in the form of cavitation generators operating in extreme conditions of cavitation wear. Structural elements were examined made of steel with the ferritic-perlitic structure of the P265GH grade and with the austenitic chromium-nickel structure of the X2CrNi18-9 (304L) grade with a protective composite low-friction coating applied onto their surfaces by the Physical Vapour Deposition (PVD) technique, intended for operation in the cavitation wear environment. In order to obtain the results, the investigations of mass loss and roughness profile changes were conducted and the analysis of structural-metallographic morphology changes on the surfaces of structural elements was performed using a scanning electron microscope at voltages accelerating from 5 to 20kV using secondary electrons detection. The results of cavitation wear on the surface of structural elements were obtained using a digital microscope operating in 4K technology with a progressive scanning system.

Bioactivity of Neem Seed Oil mixed with Pyroligneous Acid from Rice Husks against Spodoptera litura

Biopesticides are environmentally friendly solutions used for pest control management. This is a feature of Neem (Azadirachta indica) seed oil and tar, which provides a synergistic effect on the bioactivity of pyroligneous acid, and both are known to have bioactive compounds. Therefore, the purpose of this study was to evaluate the effect of neem seed oil and tar on pyroligneous acid from rice husks in conventional emulsion form, and their efficacy on the polyphagous insect Spodoptera litura. Neem seed oil was added at concentrations of 10, 20, 30, and 40%, while the concentration of tar was 0.5, 1.0, and 2.0%. The conventional emulsion formed was then characterized using a digital microscope. The addition of neem seed oil and tar were able to increase the antifeedant activity of pyroligneous acid by 63.6 % while both neem oil and tar by 72.6 %. The 2.0% tar formulation (N4PT2) showed the highest antifeedant activity against S.litura (97.9 %) and had the smallest droplets size ranges (2.90 - 24.16 µm). The addition of tar tends to reduce the droplet size of neem oil and increase antifeedant activity.