Papers by Keyword: Grinding

Abstract: The work addresses the issues of increasing processing accuracy and productivity by controlling technological connections that act during the formation of shaped surfaces by grinding and plastic deformation, presents the main indicators of the quality of teeth on the working surface, provided by the developed technology, with a decrease in the maximum value of the actual cutting depth by more than 1.5 times when grinding toothed surfaces by copying, determined influence of the position of the workpiece on the accuracy of the pitch and half-angles of the profile for rolling threads of high precision by radial feed, the purpose of which is movement and measurement, design features determined of rollers for thread rolling on workpieces with low rigidity with tangential feed, the parameters of their threads, including the functional and structural relationship of the helix angles with the dimensions of the rolled thread.

Abstract: In the field of manufacturing and machining, the optimization of grinding cycle is of paramount importance, with the goal of optimizing efficiency to the fullest extent. This article will delve into the various utilization of dynamic programming as a potent methodology to achieve this objective. By applying the principles of complex mathematical modeling, aim is to minimize grinding cycle times while maintaining the standards of quality, durability and mechanical properties of the treated metals. The results of our research confirm the high potential of improving the mechanical treatment of metals in grinding operations through the mathematical use of dynamic programming.

Abstract: The grinding technologies are widely used for finishing operations of various types of parts to provide better surface roughness and accuracy for the selected surfaces. Those technologies are expensive and take a lot of time to execute them consequently they are used when it is reasoned. The goal of this research is to compare the manufacturing design process for horizontal and vertical grinding where the arrangement distinction between them is just the position of the tool axis compared to the machined surface of the workpiece. All of the necessary manufacturing parameters are determined to ease the design process. After the manufacturing design CAM design and CNC program writing are possible if CNC controlled machine is applied. Using of the same manufacturing parameters a comparative manufacturing analysis is done to determine the differences between the two processes.

Abstract: Cement production is currently very energy-intensive, with the grinding process consuming the majority of the total energy in cement production. Therefore, there is a constant search for ways to reduce this amount of energy while maintaining the same grinding efficiency. The main goal of the article is to investigate the effect of grinding intensifiers, which should reduce the energy needed to grind raw materials. Potentially usable technologies in the field of mechanochemical activation are investigated, i.e., high-speed grinding through grinding in a laboratory planetary mill and disintegrator. High-speed disintegrator grinding technology is much more efficient than planetary grinding technology. Already during the first passage through the disintegrator, an increase in the specific surface area from 200 m²/kg to 280 m²/kg was recorded, with an estimated stay of the particle in the grinding space for 3-5 seconds. Using a planetary mill, the particles would have to remain in the grinding chamber for approximately 2 minutes to achieve such an increase in specific surface area. However, with further drops, the efficiency decreases, which is due to the high tendency to aggregation and agglomeration in this milling technology.

Abstract: The methods of influence on the material using different energy sources are considered. The role of friction in several technological processes is emphasized. The technological process of heat treatment is proposed, which allowed to restore the properties of rolled rolls that were lost due to incorrect grinding conditions. Application of the proposed technological process has shown that: 40X steel can be hardened to martensite in oil, water, and in a 10 % aqueous solution of NaCI salt, but with different results (i); the most effective hardening mode for 40X steel rolls is quenching with cooling in a 10 % aqueous solution of NaCI salt and subsequent high-temperature tempering, which is necessary to remove dangerous residual stresses (ii); the structure of the surface working layer of 40X steel rolls, after the selected optimal heat treatment regime, consists of fine-needle martensite and a small amount of Cr carbides (iii); closer to the core of the rolls, in addition to martensite, there are areas of troostite-bainite structure (iv); the resulting structure of the rolled rolls is capable of ensuring their efficient and long-term operation, but under optimal conditions, when the rolls' heating temperatures do not exceed 200 °C, and the proposed temperature conditions are recommended for both operation and routine maintenance associated with periodic restorative grinding of the working surfaces of the rolled rolls (v).

Abstract: The grinding processes of shaping materials are one of the oldest known. However, the first grinding machine tool did not appear until the beginning of the 19^th century. Industries as important as the automobile would not have been possible without its invention. One of the machine tools that made this development possible was the universal grinding machine patented by Joseph R. Brown in 1877. Unfortunately, none of these early machine tools have been preserved and only the patent remains. Therefore, in this work, a virtual model of this first universal grinding machine has been developed by applying reverse engineering techniques. For this purpose, the existing data in the patent and in some machine treatises of that time have been used. Based on this information, the functionality of each of its components have been interpreted and analyzed. Starting from a set of hypotheses, a scaled and parameterized functional 3D model has been developed. Additionally, a kinematic study of the grinding wheel drive system has been carried out. Hence, this digital model ensures the durability of an important piece of the universal industrial heritage. Furthermore, it can be used as a teaching tool for engineering students, showing the operation of a machine tool belonging to a historical context different from the current one, which does not differ substantially in its architecture of modern universal grinding machines.

Abstract: Fixed platforms employed in oil & gas shallow waters industry are subjected to dynamic loads created by winds, waves and currents. However, such loads can produce fatigue damage, like localized cracking in the weld toes of T-welded connections of the submerged structures of fixed platforms. Therefore, to repair localized cracking, a technique that combines grinding and wet welding can be applied at the weld toes of submerged structural connections. Accordingly, in the present work it is presented a methodology to restore the fatigue life of T-welded connections fabricated with A36 plate steel. Consequently, T-welded connections samples were prepared and tested under intact, grinding and grinding-wet-welding repair conditions. For the repair conditions, the weld toes were grinded 6 mm and 10 mm, and wet welding was deposited to fill the grinded material in a hyperbaric chamber, which simulated 50 m, 70 m and 100 m water depths. Afterwards, the repaired connections were subjected to fatigue loads, and the S-N curves were measured for intact and repair conditions. Fatigue results showed that the combined repair technique was able to restore the fatigue life of T-welded connections for a maximum water depth of 50 m. Nonetheless, for water depths of 70 m and 100 m the fatigue life was smaller than for 50 m, but higher compared to the only grinding repair condition.

Abstract: The article investigates the influence of the water content during grinding the raw material mixture on the formation of monoclinic phases M1 and M3 of alite using the Rietveld method. Four identical raw material mixtures were chosen, differing only in the water content for the grinding process. The milling process in a water environment in a PULVERISETTE 6 planetary mill was chosen for the preparation of the raw material mixture. Based on previous research in this area, a firing temperature of 1450 °C with soaking for 60 minutes was chosen. The results showed that the monoclinic M3 phase is predominantly formed. In contrast, the monoclinic M1 phase forms at lower firing temperatures than the M3 phase and with fewer crystallization nuclei due to less fine grinding. The results show that the amount of water used to grind the feedstock does not make any difference in the final amount of monoclinic M1 and M3 phases.

Abstract: Insufficient offer of high-temperature fly ash meeting the requirements of standard EN 4501 is becoming an increasingly significant problem for concrete technology. This trend is generally caused by relentless effort to green electricity generation and reduce the carbon footprint, leading to the decommissioning of coal-fired power plants and the greening of existing. The most often ways are combustion processes of fluidized-bed and selective non-catalytic nitrogen oxide reduction (SNCR) processes. Thanks to these processes, the demand for this raw material has significantly exceeded its supply in recent years. It is, therefore, more than current to look for ways to use the large amount of ash produced from coal combustion, which is not high-temperature fly ash, but can be classified as a bed combustion fly ash or cinder. The paper aims to show the possible processing and subsequent use of these waste materials for the production of cement composites. The possibilities of grinding these coarse-grained fly ashes and the subsequent impact of their use on the cement composite in comparison with conventional fly ash according to the standard EN 450 from the same sources were verified. The impact of their use on the properties of composites in the fresh and hardened state was analysed, and these impacts were related to, for example, their chemistry, grain morphology, loss on ignition, or fineness.

Abstract: This article aims to explain the reasons leading to the damage of a drill during its final grinding. Metallographic analysis using light and scanning electron microscopy was used to determine whether the damage was related to the structure of the material, which is given by its chemical composition, forming, and especially its heat treatment, or the grinding methodology. The drill was made of HS 2-9-1-8 tool steel. Fractographic analysis showed a cleavage fracture. In terms of the heat treatment used, the measured hardness of the analysed samples was appropriate for the requirements and possibilities of the tool steel. The metallographic analysis showed that the microstructure contained areas with clusters of primary carbides. These clumps significantly reduce the toughness of the material. In addition, there was a structural notch in the form of a white layer with a higher carbon content on the outer circumference of the samples. This layer also significantly contributed to the reduction of toughness. The hardened layer below the structural notch also contributed to the reduction in toughness. All of these microstructural defects were caused by poor grinding, which led to damage to the tool.