In technical practice, increasing wear resistance can be done in a variety of methods. However, most of them are technologically, time, and energy intensive, and the costs incurred frequently ...outweigh the benefits received. This study aims at surface modification of the selected grades of steels (25CrMo4, 30CrMoV9, 41CrAlMo7) through the TIG (tungsten inert gas) remelting process using a CaCN
2
-based powder. TIG remelting process was conducted in the shielding atmosphere of 99.996% argon (argon 4.6) at a gas flow of 10 l·min
−1
and a welding current of 110 A. After remelting, the microstructure of the generated layers was analysed using scanning electron microscopy (SEM) and the hardness of newly formed layers was evaluated using a microhardness machine. In all of the tested steels, nitrogen had a favourable impact on the rise in hardenability, which resulted in a notable increase in hardness and resistance to abrasive wear. A significant increase in hardness and abrasive wear resistance was achieved up to a depth of 1–1.5 mm from the surface in the case of all steels through the remelting process. The effect of nitrogen on the increase in the investigated properties is documented by a comparison of samples remelted in the absence and presence of CaCN
2
-based powder. The most significant increases of both parameters under investigation were attained in 25CrMo4 steel, which had the most considerable nitrogen enrichment. This method represents a cheap, technologically available, and fast way of forming surface layers with increased hardness and wear resistance, which makes it applicable in engineering, agriculture, earthworks, etc.
The aim of the paper is to examine the requirements of producers in post-communist countries with lower economic level. The first requirement was how to overcome the limitations of conventional PFMEA ...to propose measures effectively. The second requirement solved the economic effect of failure modes. The aim of the paper was to create a new hybrid PFMEA–DEMATEL–ERPN model to manage failure modes to resolve the requirements. The DEMATEL model overcame the limitations of PFMEA. DEMATEL data were used to estimate the functionality of the proposed models. Criteria such as the occurrence of defective products and the probability of their occurrence (O and RPN) were monitored. ERPN also overcame the limitations of PFMEA. Internal and external costs arise as effects of failure modes. The costs were included in the economic evaluation of the models. We validated the models in a transfer pressing process. The estimation of models’ functionality proved to be correct. The economic evaluation refined the research results and resolved the second requirement of the manufacturers. The DEMATEL and ERPN models (compared to PFMEA) proved their validity when the use of PFMEA was limited. By using DEMATEL, we registered the lowest number of defective products and the lowest costs.
The combination of stamping and subsequent welding of components is an important area of the automotive industry. Stamping inaccuracies affect the final size of the stamping and the welded part. In ...this article, we deal with a specific component that is produced by such a procedure and is also a common part of the geometry of a car. We focused on the possibility of using a negative phenomenon—deformation during welding—on the partial elimination of inaccuracies arising during stamping. Based on the planned experiment, we created a prediction model for the selected part and its production, with the help of which it is possible to determine suitable welding parameters for a specific dimension of the stamping and the required monitored dimension of the welded part. The article also includes the results of additional experimental measurements verifying the accuracy of the model and prediction maps for practice.
The formulation of the Hall–Petch relationship in the early 1950s has raised immense interest in studying the influence of the grain size of solid materials on their properties. Grain refinement can ...be achieved through extreme deformation. In the presented study, Equal-Channel Angular Pressing (ECAP) was successfully applied to produce an ultrafine-grained microstructure in a pure commercial Cu of 99.9 wt%. Samples were processed by ECAP at 21 °C for six passes via route A. A new equation of equilibrium that allows the exact determination of the number of extrusions and other technological parameters required to achieve the desired final grain size has been developed. The presented research also deals, in a relatively detailed and comparative way, with the use of ultrasound. In this context, a very close correlation between the process functions of extrusion and the speed of longitudinal ultrasonic waves was confirmed.
The presented publication is based on the interaction of the material core and its surface during the machining process with a hydro abrasive flexible cutting tool (AWJ). In the AWJ technology, a ...cold cut is generated; therefore, there are no thermal stresses on the newly formed surface and, consequently, no significant internal and residual stresses. The cut is identifiable by directly measurable parameters: depth of cut, deviation of the cut path from the normal plane, and surface roughness. These geometric parameters are interdependent at each cut zone point and simultaneously dependent on a newly proposed, indirectly measurable material parameter,
K
plmat
. Although the deviation angle of the cutting path from the normal plane increases with increasing depth of cut, the ratio of the “material plasticity”
K
plmat
and the surface roughness
Ra
of the cutting surface remains equivalent to the ratio of the depth of cut and the deviation of the cutting path from the normal plane. Based on the proposed concept, an entirely new approach to the problem of material surface integrity is presented by the method of identification of mechanical equivalents and their functional transformation. The solution to the subject problem is based on the fact that the technological process of machined material decomposition specifically and identically “copies” the surface properties of the material, i.e. records its technological inheritance. The material properties can then be “read retrospectively” reliably and accurately using the recording.
The efficient use of municipal waste is becoming increasingly important for sustainable environmental quality. An integral part of the process of recycling waste material is its quality sorting. ...Nowadays, both manual and automated sorting methods, especially optical sorting, are used worldwide for sorting mixed waste. This article presents the application of the NIR/VIS optical sorting system through a description of this processing equipment integrated into a specific plastic waste processing line. The aim of the article was to select the optimal mode of operation generally applicable to mixed waste, and, specifically, to compare the quality of sorting of plastic waste in automated and manual sorting modes. In order to compare the efficiency of the sorting system, significant parameters of the sorting process were proposed. The measurement of the plastic waste sorting purity parameter was based on data obtained by weighing selected control samples, and the evaluation of the results of these measurements showed, in particular, the dependence of the concerned parameter not only on the sorting mode, i.e., automated and manual, but also on the conveyor belt speed/waste material flow, on the pre-sorting methods and, in the case of manual sorting, on the operating shift. The subsequent economic assessment of both sorting processes clearly declared the investment in automated sorting systems in the optical system operation mode not only as profitable, but also as extremely advantageous both for the production economy and the environment.
Residual stresses are defined as the stresses that occur in the material without the application of an external load. Their occurrence is related to the technology of production and treatment of the ...material. This article proposes the identification of residual stresses in a steel material for bearing production, specifically 100Cr
6
(1.3505) material. The identification consists in measuring the material by X-ray diffraction method, for which the Proto iXRD mobile diffractometer was chosen. The first measurement was carried out on turned bearing rings and a subsequent second measurement was carried out on the same rings after heat treatment, namely quenching and tempering. This article also proposes a measurement methodology for the bearing rings, where each ring is measured in 6 positions rotated 60° with respect to each other. The measurement results are compared with the individual manufacturing operations, i.e. turning and heat treatment. The results clearly show the expected increase in residual stresses after turning and subsequent decrease after heat treatment. The technological parameters of turning fundamentally influence the residual stresses and thus also affect the quality of the product in subsequent production operations.
Austenitic stainless steel belongs to the best oxidation-resistant alloys, which must function effectively and reliably when used in a corrosion environment. Their attractive combination of ...properties ensures their stable position in the steel industry. They belong to a group of difficult-to-cut materials, and the abrasive water jet cutting technology is often used for their processing. Samples made of stainless steel AISI 304 has been used as the experimental material. Data generated during experiments were used to study the effects of AWJ process parameters (high-pressure water volume flow rate, the diameter of the abrasive nozzle, the distance of the nozzle from the material surface, cutting head feed rate, abrasive mass flow, and material thickness) on surface roughness. Based on the analysis and interpretation of all data, a prediction model was created. The main goal of the long-term research was to create the simplest and most usable prediction model for the group of austenitic steels, based on the evaluation of the practical results obtained in the company Watting Ltd. (Budovateľská 3598/38, Prešov, Slovakia) during 20 years of operation and cooperation with customers from industrial practice. Based on specific customer requirements from practice, the publication also contains specific recommendations for practice and a proposal for the classification of the predicted cut quality.
The production of parts by pressing and subsequent welding is commonly used in the automotive industry. The disadvantage of this method of production is that inaccuracies arising during pressing ...significantly affect the final dimension of the part. However, this can be corrected by the choice of the technological parameters of the following operation—welding. Suitably designed parameters make it possible to partially eliminate inaccuracies arising during pressing and thus increase the overall applicability of this technology. The paper is focused on the upper arm geometry of a car produced in this manner. There have been two neural networks proposed in which the optimal welding parameters are determined based on the stamped dimensions and the desired final dimensions. The Levenberg–Marquardt back-propagation algorithm and the Bayesian regularised back-propagation algorithm were used as the learning algorithm for ANNs in multi-layer feed-forward networks. The outputs obtained from the neural networks were compared with a linear prediction model based on a on the design of experiment methodology. The mean absolute percentage error of the linear regression model on the entire dataset was 3 × 10−3%. A neural network with Levenberg–Marquardt back-propagation learning algorithm had a mean absolute percentage error of 4 × 10−3. Similarly, a neural network with a Bayesian regularised back-propagation learning algorithm had a mean absolute percentage error of 3 × 10−3%.
Presented paper deals with the issue of lubricating tribological systems formed by a double pair operating under mixed conditions of mixed friction before and after experimental tests, which were ...conducted in accordance with the selected methodology using Tribotestor M‘06 test machine. The lubricating media included ecological oils Plantohyd 46 S by Fuchs and EAL Hydraulic 46 manufactured by the Mobil company. Applied ecological oils can be used in agricultural mobile machines as a replacement for conventional lubricants. The tests were conducted on designated material double pairs. The shaft was made of steel 16MnCr5. The second observed friction element in terms of glide angle test was a steel plate made of S235JR, gliding surface of which was produced utilizing flame powder coating technology. The results were statistically processed and are presented in the form of graphs, tables and figures.
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