Univerzitná knižnica - Vedecké odborné časopisy

This paper deals with surface integrity and the corresponding Barkhausen noise after shot peening of duplex steel AlSi 318 under variable shot-peening conditions such as number of passes and applied air pressure. Surface state is investigated from the point of view of surface roughness and surface plastic deformation. Barkhausen noise is decreasing along with increasing surface coverage as well as increasing air pressure. The duplex matrix is considered being stable with respect of volume fraction between austenite and ferrite and the whole Barkhausen noise signal originates from ferromagnetic ferrite. Progressively developed plastic deformation increases dislocation density in the surface as a result of surface bombardment by shots which in turn shift Barkhausen envelopes into higher magnetic fields.

The present paper deals with Barkhausen noise emission in Gd. Barkhausen noise emission was investigated in the temperature range mainly below the Gd Curie temperature when the spontaneous magnetization in Gd occurs. Barkhausen noise from the heavy rare-earth Gd is compared with Barkhausen noise emission from the transition metal Co measured at the same magnetizing and other conditions. This study demonstrates that Barkhausen noise emitted from Gd is much weaker than that originating from Co. This is a consequence of different spin exchange interaction among the neighbouring atoms, domain wall thickness as a well as domain wall energies. Moreover, Barkhausen noise is temperature sensitive especially for Gd sample as a result of the altering magneto-crystalline anisotropy.

This paper deals with surface integrity after hard milling of bearing steel 100Cr6. Surface integrity is expressed in terms of shape deviation as well as Barkhausen noise emission. Furthermore, components of cutting forces are also measured as a function of tool wear. Non homogeneity of cutting force distribution within the contact between the milling cutter and workpiece is discussed. The results of measurements indicate that the shape as well as structure remarkable non homogeneity should be expected after hard milling due to missing full contact between milling cutter and workpiece. This non homogeneity can be monitored via Barkhausen noise technique. On the other hand, the competitive grinding cycles produced more homogenous surface and surface state is a function of infeed speed.

Abstract: This paper deals with surface integrity after shot peening of AlSi 304 under variable conditions expressed in term of shot-peening cycles and corresponding Almen intensities. Surface state is investigated from the point of view of surface topography, surface roughness and microhardness. Also phase transformation of paramagnetic austenite into strain induced martensite is investigated as well by the use of Barkhausen noise technique. It was found that the fraction of strain induced martensite grows with the number of shot-peening cycles and its extent penetrates deeper beneath the free surface. Furthermore, surface roughness decreases along with increasing number of cycles. Surface microcracking occurs after prolonged shot-peening cycles. Abstract: Paper was devoted to new methods coming to wide use in design engineering. These methods contained of topology optimization and generative design. Although topology optimization is practiced for some time, the generative design is its biggest contender. Both methods were described in a way of how they work and what methodology needs to be abided. At the end, a comparison between advantages and disadvantages as well was done, taking into account use of both of them in gear wheel body optimization. Abstract: The paper focuses on the manufacturability optimization of the of case made of aluminium by the rubber forming process. Al6016 aluminium was considered as the material for the cover and its constitutive equations were defined by Hill 48 and Hollomon models. The Mooney-Rivlin hyperelastic material model described the material properties of the rubber-made punch. Simulation model was built in Pam stamp software and the results were evaluated as well. The results were optimized in terms of thickness thinning and punch stroke, for two different rubber hardness. Abstract: The article describes the method of boriding sintered carbides type H1 (K10) and G1 (K20) and tool steel Cr-Mo-V. The aim of this work is to analyze the knowledge about boriding of steels with the focus on the technological assumptions of the use of boriding in the production process of forming tools in order to increase the resistance to friction, abrasive and adhesive wear. Interestingly, boriding is still an unconventional method of surface treatment. The presented work deals with the structural analysis of borided layers. Steel samples of 1.2365 material and sintered carbides H1 (K10), G1 (K20) borided with EKabor 2 powder were monitored. For the testing of metallographic samples, the methodology developed for the study of the microstructure of sintered carbides was developed. The monitored samples, borided at 900 °C for 240 min, obtained a uniform layer 5 μm thick. An increase in microhardness of more than 700 HVM was measured for carbide H1 (K10) and almost 1500 HVM for G1 (K20). The increase in hardness is due to the formation of dispersed cobalt borides Co2B and CoB. Abstract: Submitted paper aims to further analyse the possibilities of melt velocity reduction in the gating system. In this work was designed the naturally pressurized gating system. Proposed design appears to be a suitable solution for reoxidation processes reduction. Disadvantage of this system is that the melt velocity is supercritical, which leads to splashes of the melt when entering gates. Main focus of experimental part is to find a proper way to reduce the melt velocity, which will consequently decrease the reoxidation processes. For the purpose of the melt velocity reduction, labyrinth filters, flat filters and foam filters effect were investigated and visualized by simulation software ProCAST. Experimental casts were carried out, to be able to verify the results of the simulations. Mechanical properties and porosity evaluation was investigated on casted samples. Flat and foam filter appeared to be a suitable to melt velocity reduction and it was associated with increasing mechanical properties of castings. Construction with foam filter achieved the best results. Abstract: The aim of this paper was to analyze the impact of different zirconium addition (0.05; 0.10; 0.15 and 0.20 wt. % Zr) on selected properties of AlSi5Cu2Mg aluminum alloy. It is a new alloy for cylinder head castings and has only been used for a relatively short time. The specificity of this alloy is its chemical composition - specifically the low permitted Ti content, which makes it impossible to refine the grain structure of this alloy using standard Al-Ti-B grain refiners. The results of our research showed that increasing zirconium content had no effect on the increase in ultimate tensile strength, yield strength and hardness of as-cast samples. After T7 heat treatment, a more significant increase in UTS, YS and thermal conductivity occurred due to the precipitation of Cu- and Mg rich strengthening precipitates. Zirconium-rich intermetallic phases were observed in the shape of separate thick needles or as a cluster of two crossed thinner needles. These phases were not affected even after heat treatment, indicating their high thermal stability. Increasing the Zr content was accompanied by an increase in liquidus temperature and area fraction of porosity values. Abstract: International Standard EN ISO 22081 sets out rules for the definition and interpretation of general geometric specifications and general dimensional specifications according to Article 5.12 of ISO 8015: 2011). The general GPS specifications apply individually to each characteristic of a geometric element or to a relationship between geometric elements for which no individual GPS specification of the same type is defined. The general GPS specifications, which prescribe general dimensional and geometric tolerances, make it possible to simplify the indications and thus the reading of the drawing documentation, while at the same time facilitating the selection of tolerances. The new standard EN ISO 22081 replaces the standard ISO 2768 and gives rules for the application of the general geometric and general dimensional specification. Abstract: The paper deals with the limitations of testing ferromagnetic materials by the magnetic particle method. It focuses mainly on the influence of orientation and depth of materiál defects on the reliability of identification of surface and volume defects when using color and UV methods. The results obtained using unidirectional and alternating pole magnetization in manual control with a magnetic yoke are compared. Abstract: The article deals with the historical development and analysis of the current state of handling machines used in the entertainment industry. It points in particular to the material aspect, i.e. materials used for the production of amusement park equipment components. The article represents an important aspect that precedes the design of such a device, respecting the currently valid legislative requirements based on the standard STN EN 13814 so as to ensure protection against injuries or potentially dangerous situations (ejection, falling out, hitting, etc.). Abstract: The growing trend of using and processing big data brings space to study, analyze and understand the performance aspects of the monitored advanced technologies. In general, benchmarking is a well-known tool in the world of software systems that is commonly used to identify companies' strengths and weaknesses. The article presents the use of the benchmarking tool as a tool for evaluating the application of advanced technologies supporting the management of the production process. Abstract: The strength of fine-grained HSLA steels is mainly based on the grain boundary strengthening, which as the only strengthening mechanism allows the yield strength to increase without a decrease in ductility. Therefore, any change in grain size leads to irreversible changes in the properties of the material. Such changes also occur in the coarse-grain heat affected zone (CGHAZ) of welded joints, where there is an increase in austenitic grain size, which leads to a decrease in yield strength, or decrease of fatigue strength. The paper experimentally determines the growth kinetics of austenitic grain for S960MC steel. Based on the measured data, it will be possible to predict the grain growth kinetics in the CGHAZ and FGHAZ. The acquired knowledge will help to set the welding processes of fine-grained steels. The measured data will also provide a basis for numerical simulations of metallurgical processes in high-temperature HAZ during welding. Abstract: One of the basic requirements of the current industrial production is to extend the life time of thermal aggregates while taking into consideration the maximum economic effectiveness. The use of non-shaped refractory mixtures for manufacturing of monolithic linings represents a progressive trend that replaces traditional brick linings. Non-shaped materials enable to create linings of different shapes and sizes, their firing takes place at the consumer and their repair is much simpler. These aspects increase the productivity and save energy. The paper covers practical applications of castables from the production of the company RMS Košice s.r.o. in the foundry industry. Abstract: The article is a continuation of research dealing with the construction of entertainment facilities. The main goal of the authors is therefore to design such an entertainment device according to their own design. This goal was preceded by a historical overview of the development of transport and handling technology used in the entertainment industry. The current work aims to analyse the main components used in the construction of these devices such as nacelles, seats, restraints or drives and fasteners according to STN EN 13814 so that the design meets all requirements. Abstract: The paper is supplemented by a discussion of the results and in the end an evaluation of the experiments is made. The paper presents basic theoretical knowledge about the cutting process. The experimental part describes the cutting, forming and evaluation of the obtained cylindrical samples for rolling elements. Abstract: Residual stress plays an important role in welded structures, which are stressed not only by cyclic loading. The work deals with the creation of a butt weld joint made of HSLA steel S960MC with a thickness of 3 mm and its subsequent analysis for residual stresses. The result of the work is the evaluation of the residual stresses of the welded joint. Abstract: In addition to the mechanical properties, the formability and appearance after painting of the coated sheets depends on the surface texture. The surface roughness characteristics of the sheet, the mean arithmetic deviation Ra and the number of peaks per centimetre Pc, depend on the surface texture of the finishing rolls of the rolling mill, their wear and the removal on the rolling mill. This paper presents the results of an investigation of surface-finished sheet metal, the surface of which was textured by changing the electrodischarge texturing (EDT) parameters of the finishing rolls of a rolling mill. The optimization of current Ip, voltage Up, pulse duration POnT and pulse off time POffT on the target values of roughness RaT,FR and number of peaks PcT,FR of finishing rolls was carried out by response surface methodology (RSM). The obtained regression models describe with a high degree of accuracy the relationships between the input electrodischarge texturing parameters of the finishing rolls and the output texture characteristics RaT,FR and PcT,F Abstract: The issue of the conditions and suitability of the supply of glass to the dispenser head can be precisely solved only with the use of knowledge of fluid mechanics. The paper presents the used calculation methods of finite parameters and also makes their mutual comparison in terms of suitability of the solution. Abstract: In the hot metal and steel production the thermal equipment used for their production is essential with respect to the associated costs. The lining of torpedoes, blast oxygen furnaces, hot metal and steel ladles must withstand challenging manufacturing conditions. The working lining, that gets in contact with hot metal, wears out since it is affected by molten metal. The permanent lining on the other hand fulfills the safety and insulation function. The permanent lining is supposed to collect molten metal if the working lining is worn out and keep the metal temperature on the level of processing. When emptying a ladle, the lining protective layer (scab) is created if the temperature on the working lining surface is lower than the metal melting temperature. When designing the lining composition, the emphasis is given to material properties, as well as to its life time at the lowest costs per ton of steel. The paper evaluates permanent linings of metallurgical aggregates based on their thermal shock resistance and level of penetration into the brick volume. Abstract: The paper deals with an overview of selected additive technologies used in the automotive industry. The emphasis is mainly on technologies that use metal powders. Furthermore, the work focuses on machine improvements and also presents a possible breakthrough in series additive production thanks to new production systems. Abstract: The paper presents the application of one-way analysis of variance (ANOVA) and Tukey's HSD method of multiple comparison, which can be used in the experiment, which determined the effect of cutting speed on the perpendicularity deviation of the cutting surface when cutting stainless steel X5 Cr Ni 1810 using laser. The details and technological parameters of laser cutting steel are mentioned. Based on the results obtained using ANOVA and Tukey's HSD method, it can be argued that different cutting speeds have a statistically significant effect on the perpendicularity deviation of the cutting surface. Abstract: The solution of electromagnetic compatibility and resistance of equipment to atmospheric discharges is a very important issue in the development and testing of electrotechnical and electronic equipment. The paper presents a numerical calculation of the parameters of a simplified mathematical model of a trial current and voltage pulse, which is defined by the IEC 61000-4-5 standard. The simplification consists in replacing the current pulse leading time, which is determined by said standard as 1.25 times the time from reaching 10% of the maximum amplitude to reaching 90% of the maximum amplitude, by a time from 0% to 100% of the maximum amplitude. For the solution of the equations for the calculation of the parameters of the simplified model by the numerical Newton - Raphson method, the initial approximation of the solution is determined and the cases when the solution does not exist are determined. Abstract: The paper discusses that the filtration of castings influences the deformed resistance. The article describes the change in toughness in castings using filtration during casting and subsequent changes in mechanical properties after forming these castings. Subsequently, the volumetric compressibility of samples of the same material was monitored. The chosen material is aluminium alloy due to good formability. The mechanical properties after forming on the filtered casting were compared with the casting without filtration. The essence of the tests is to ensure the behaviour of the material in two mutually different environments and to compare the size of the barrel and the susceptibility to cracking on the circumference of the samples. The experiment confirmed the effectiveness of filtering and its effect on the forming force. Abstract: The results of a survey of the reliability of automobile trains in the composition of MERCEDES-BENZ 1844 ACTROS LS trucks and semi-trailers KÖGEL, KRONE, SCHMITZ at different stages of operation are presented. The malfunctions of units and assemblies are revealed, regularities are established, the causes of malfunctions and failures are determined.

Univerzitná knižnica - Vedecké odborné časopisy

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