Fulltext search in archive

The paper deals with heat affection of selected armoured ultra-high strength steels after their cutting by plasma and laser and their welding with using MAG welding method where critical degradation of mechanical properties could occur in heat affected zone after application of these technologies. Armox steels are armoured ultra-high strength martensitic steels with the usage in special technology. The steels are produced in the form of forged semiproducts as sheets and plates. These sheets are cut and most commonly welded in a way to made the final product. Experimental samples made of Armox 500 steel with using of aforesaid thermal based technologies are studied in the paper to evaluate selected heat affected zone parameters.

Presented article deals about the experimental investigation of PVD coated cutting inserts of type SNHF 120408EN-SR-M1while hard face milling of steel Armox 500. This study was supported by the Slovak Research and Development Agency under the contract No. APVV-15-0710". All realized measurements and tests have been performed at Department of Engineering in Trencin. It also includes support and cooperation with the University of Defence in Brno, Department of mechanical engineering. The main aim of this experimental work is to focus measurement on the influence of the various values of feed rates per tooth during the hard machining experiments of steel Armox 500. All tested workpiece material is investigated with variable cutting conditions of feed rate per tooth, whereas the cutting speed and depth of cut were specified as the constant cutting parameters. Practical part of presented work also includes some figures of worn flank faces of carbide cutting inserts, microstructure of workpiece material and graphical dependences of tool wear and tool life curve in logarithm graph as the results of these realized experimental investigation.

Mapping surface quality changes during modification of the cutting tool microgeometry and reflecting on overall quality is the main purpose of this article. A complex view of microgeometry brings together the effects of indvidual stages in the processes which increase the cutting tool properties. The main objective is to increase the durability of the cutting tool. Grinding, microgeometry modification and deposition of a thin resistant layer on the cutting tool are the basic stages during the experiment. These stages have a significant effect on microgeometry parameters. Cutting edge radius, cutting edge symmetry (K factor), roughness of chipping and clearance surfaces are parameters affected by modification processes. Changing individual microgeometry parameters determines not only the surface quality of the cutting tool, but also affects the durability and stability of the cuting process. Appropriate microgeometry modification can make the cutting process more efficient. The combination of process stages and their influence on the quality of the microgeometry of the cutting tool is the primary objective in this article.

The article describes the possibilities of pre-treatment of hot-dip galvanized parts and their influence on the adhesion of organic coating. The main objective of this work was to compare the current possibilities of pre-treatment of hot-dip galvanized parts, this means phosphating, chromating and mechanical pre-treatment by light blasting and compare these technologies with today's alternative pre-treatment technologies based on chemical substances containing fluorozirconates. The basic function of these pre-treatments is to increase the adhesion of the organic coatings and to increase the lifetime of the entire corrosion protection. Another objective is to reduce the environmental impact of these pre-treatments, reduce energy for the technological process of pre-treatment and many other aspects. Last but no least to compare the different types of organic coating systems with using these pre-treatments on the hot-dip galvanized surface.

This constribution presents the engineering design of the non-conventional shearing device, which uses for the operation the magnetic field. There is a prototype of the device designed and constructed in laboratory conditions. There are presented all relevant and necessary data of this shearing device supported by figures and scheme. The principle of the device operation consists in the fact that a sheet passes through feed rollers into the shearing position, i.e. into the position between two blades. Lower is fixed and the upper is guided in rails and controlled by means of springs. After the material dividing the electric circuit is interrupted and the moving blade returns into the starting position due to spring's action. This process of metal shearing can be quite simply automated. We have performed same experimental works using this device. There were sheared same sheet samples and the comparision of surfaces are shown. The use of our our device has proven to be appropriate for shearing sheets made of aluminium alloys with the thickness of 0.3 mm.

In order to successfully acquire knowledge in area of machinery safety for engineering students it is necessary to adopt elementary principles associated with risk assessment. Identification of possible hazards is an important part of risk assessment and engineering students need to take part also in hands-on training to supplement their learning process. It is clear that one major obstacle to improve safety training is the problem of allowing learners to work directly with hazardous equipment. Traditional approach is based on the use of slide show presentations enhanced by animations or videos. This training method is passive in nature and does not allow for an actual realization of consequences resulting from ignoring safety practices during interaction between the student and the machine. In order to improve the educational practice in this context, the Virtual Reality (VR) technologies could be used. The purpose of this study was to conduct a preliminary investigation to determine whether training through VR simulator is comparable to traditional training in developing the skills necessary for performing identification of possible hazards related to lathe operation. The results of this preliminary study suggest that VR based training has the potential to constitute a valid alternative to the traditional training approach.

The paper focuses on the issue of microprocessing of polymer materials by laser. Specifically, the task is solved by changing the technological parameters, namely the cutting speed, the power and a change of DPI and their impact on the resulting surface quality and depth of cut. During machining, the input technological parameters were changed and followed by evaluation of their interaction with the concentrated radiant energy of the laser beam PMMA, as and representative of the amorphous polymers, was selected for experimental machining. It is one of the best machinable polymer materials regarding this unconventional technology, and it is also frequently applied in industrial practice.

The aim of this paper is an analysis of dependability of an injection press. Collected data - operating times between failures and times to restoration for a year of the use of the press were processed using the Weibull distribution, for which the following basic steps were applied in compliance with ČSN EN 61649:2009 standard. The output includes Weibull distribution parameters and basic functions of reliability and maintainability, i.e. probability of failure and of reliability, density and intensity of failures, then also probability of restoration and restoration probability density. Last but not least, mean time between failures and mean time to restoration including steady-state availability were calculated. The results obtained can be useful for internal benchmarking in an organization with a higher number of presses and for developing a maintenance strategy.

The abrasive wear of pulley surfaces at winding of the ropes causes changes of the shape and quality surface of the groove and has influenced lifetime of the skidding machine. The pulley is made of steel C45E without heat treatment and its structure is not suitable for the abrasive wear of the pair metal-metal. Contribution describes a research aimed to changes in material structure by the heat treatment. The pulleys (first one in original state and second one after heat treatment) were tested in operating load at skidding during 320 hours. After experimental test, measurable properties as weight loss, groove dimensions of the pulleys were compared. On the samples from the pulleys, material resistence to wear was tested too. Another alternative for change of material properties would be an aplication of various types of weld deposits on the steel C45E. We have examined the quality of weld deposits and compared their hardness and microstructure. The results of experimental tests resulted to recommendations for practice.

The paper is part of the publication series, which describe the most significant and innovative research and development design solutions and computational procedures as part of European structural funds project. The object of this article is strength conditions assessment of a new structure of railway tank wagon. For validation of the new construction assemblies, there has been created a substitute simulation model. Results of calculations and prototype tests prove, that new structure of the construction satisfies strength assessments according to valid requirements and standards.

In the article the issue of perspective running parts for freight cars of new generation is considered and additions to the outdated existing classification of bogie are developed, namely introduction of such types of suspension is suggested.The results of theoretical studies are presented by means of modeling the movement of the car in the software "Universal Mechanism" to determine the influence of the first stage of spring suspension in Barber type bogie (type 18-100 and analogues) on energy efficiency (resistance to movement) and the estimated value of the decrease in resistance to movement.A concept for a fundamentally new design of a freight car bogie for high-speed traffic has been prepared, based on fundamentally new technical solutions with elastic-dissipative bearing elements, as well as a concept for the modernization of the Barber-type bogie (type 18-100 and analogues) by introducing axle suspension on the 1520 mm gauge.

Titanium aluminides represent a class of materials with unique mechanical and physical properties. This is reason why they are often used in aerospace or automotive industries. These materials form lamellar or nearly lamellar TiAl and Ti3Al phases. There are few methods how to synthesize Ti-Al based alloys, but they are often very difficult and expensive. In present work, a mechanical alloying which is probably best choice for synthesizing of Ti-Al intermetallic phases was used. Further, the most promising conditions of mechanical alloying allowing to create intermetallic phases were determined. It was shown, that by mechanical alloying allows to synthesize desired alloys with grains sizes of several tens of nanometres.

The article discusses the effect of heat treatment on the microstructure of the aluminum alloy AlSi7CrMnCu2.5. Heat treatment of aluminum alloys can be defined as a technological process by which products or components in solid state are exposed to one or more annealing cycles in order to achieve the desired structure. Thanks to these structural changes it is possible to affect the mechanical properties by the hardenable alloy. Samples where the research was conducted were cast from AlSi7CrMnCu2.5 alloy produced by gravity casting technology in metal mold. Subsequently, the castings were subjected to a heat treatment. The microstructure changes of the alloy was investigated by methods of light and electron microscopy.

The article deals with the research of the measuring probe signal of roundness machine Roundscan of Jenoptik IM producer. The probe of this machine scans geometric form as well as surface structure. The probe signal dependence on the probe arm elevation is not perfect linear and this influences the precision of evaluated form characteristics, roughness parameters as well as drall parameters. A quantification of calibration way influence on the signal characteristic was main research task. A calibration process simulator was designed and built in MATLAB for this. This article describes a way of obtaining of real probe signal. Metrological filters according current standards ISO 16610-21 and ISO 16610-22 were built in MATLAB for obtained signal filtering. The calibrating simulator simulated various master standard values, various probe arm starting positions before the calibration, various probe arm starting positions before subsequent common measurement, and tolerance limit utilisation during a master standard value transmission to the probe signal. An efficiency of signal linearization procedure was explored, as well. Obtained results are presented as signal zones, which delimit assigned signal deviations from perfect signal characteristic.

In this work, the microstructure and mechanical properties of three types of high-speed tool steels (Vanadis 60, ASP 2052 and S 705) were studied. The steel S 705 was made by conventional ingot metallurgy technology, and other types of steels were manufactured by powder metallurgy technology. The studied steels were examined both in the soft state and further in the hardened condition with subsequent tempering. Microstructure of metallographic cuts and fracture areas was studied by electron microscopy. Hardness, tensile properties and notch toughness were determined. Significant differences in the properties of steels in both studied states have been documented.

Coating of the tools for metal machining has been used for a long time, application of the coating to wood machining tools is not so explored. The aim of research in this area is to expand the possibilities of the using of PVD coatings in untraditional field at wood wool production in company, that thermo isolation and sound isolation plates manufactures. In the production of wood fibers by technology like planning, during the work the cutting edge of the knife is worn-down and the resulting product loses quality. Often grinding is required, knife dimensions are changed and lose its functional surface. The article is focused on the choose of the coating type on the base of input analysis of the tool material. Analysis is aimed to detection of the chemical content of elements, evaluation of the microstructure and mechanical properties. On the basis of the results, we proposed the type of coating applied to the sample and the tool. Coated sample was evaluated in terms of coating properties namely the thickness, tribological properties, chemical composition (EDX analysis) and microhardness. After the experiment, we have evaluated the state of cutting edge and compared it with the uncoated tool. The positive effect of the coating on the change of the cutting properties of the knife and the quality of the wood wool have been recorded.

Surface roughness is one of the most significant evaluation factor in metal machining operations. Despite the small descriptiveness is usually quantified as the arithmetical mean roughness Ra especially in the automotive industry. In order to maintain the desired surface roughness, the appropriate setting of machining parameters is important to be set before the actual cutting process. The objective of this research is to analyse the effect of machining parameters on surface roughness of stainless steel X153CrMoV12-1 in CNC milling of slope surfaces with sintered carbide tool. The data were processed using multiparametric statistical methods to find optimal results. Linear regression models and probability dendrograms of similarities were determined for cutting conditions, cutting tools and slope of machined surfaces.

The presented work was focused on the use of Ti6Al4V alloy with nanostructured surface and deposited silver nanoparticles as a material with antibacterial surface. Thanks to the electrochemically formed nanotubular oxide structure, a large area was available for silver deposition. Silver was photo-reduced from the silver nitrate solution. The ultrasonic treatment allowed the penetration of a silver source electrolyte into the whole depth of the tubes. Transmission electron microscopy images confirmed the presence of silver nanoparticles with size from units of nanometers up to 15 nm. Nanosilver was present throughout the length of the nanotubes. Samples with photo-reduced silver will be able to provide antibacterial activity not only in critical hours after implantation but also in the longer term due to the subsequent release of silver from the volume of nanotubes. The prolonged antibacterial effect has been demonstrated against Staphylococcus aureus.

Reliable method to detect relative machinability is based on constructing Taylor relation of tool durability on cutting speed for both observed materials. Optimal cutting speed for the observed material at constant durability can be detected from the relation. However, longterm test requires longer time of machining and consumption of material. Therefore a number of authors have observed the possibility of shortening the tests. There is a widespread opinion that shortened methods posses low reliability. On the other hand, those methods cannot be replaced in the conditions of actual operation. Some of them are analysed and modified as follows.

An intensive abrasive wear of agricultural machines and their parts occurs at the soil processing. An undesirable change of a tool surface occurs owing to the wear. Namely ploughshares of a plough are intensively abrasive worn. This undesirable change leads to a function loss. The paper deals with an evaluation of the ploughshare service life. The aim of the research was to evaluate the wear of the ploughshare with a layer of a carbide hardfacing OK Tubrodur 15.82 deposited on a bottom side of the ploughshare. The research was performed within a laboratory testing (a hardness HV30 and a wear) and field tests. Laboratory experiment results proved that the overlay material showed a significant increase of the wear resistance and the hardness. These conclusions of the laboratory testing were certified at the field tests. The research results certified this procedure as an efficient solution at the decreasing of the ploughshare wear at the ploughing.

The research described in this contribution is focuses on fractographic analysis of the fracture area of AlSi7Mg0.3 alloy with modified strontium. Modification is an effective tool for improving the mechanical properties of aluminum alloys and affecting the microstructure of the material. The aim of the paper is to revise the microstructure of the modified AlSi7Mg0.3 alloy and to determine its strength properties. Within the experiment, the character of the refraction was evaluated and the presence of foreign particles and elements in the material fracture was monitored. Optical microscopy identified structural parameters of the castings just below the fracture surface as well as the course of the fracture line. Using a scanning electron microscope, the fracture area of the sample was analyzed, the EDS analysis was performed and the results of these analyzes were evaluated. An increased number of O, C and F elements occurred on the surface of the samples. The occurrence of these elements most likely results in a material breakage, which also confirms the results achieved by the static tensile test. On the basis of the obtained results from the analyzes carried out, the mechanisms of the breach were determined.

The article deals with an experimental investigation tool life of the thread making tools. During long-time tests, the uncoated taps for M12 threads making were used. They were produced from high speed steel with cone type C. Three helix angles ω = 0°, 15° and 35° of taps have been investigated at the cutting speeds of 10 mmin-1 (within the first experimental phase) and 20, 30, 40 mmin-1 (during the second phase). The holes for threads making were pre-drilled into workpieces that were bars (with a cross-section of 30 x 60 mm). They were produced from C45 steel that is a standard material used at long-term tests of tool durability. Microhardness of the workpiece bars was checked within preliminary tests as well as a rank angle of tools to be ensured the same conditions of experiments. The changes in a size of the M12 thread outside the tolerance field 6H, the visible changes in tool wear and the brittle fractures of the tools have been selected as the criteria for tool life evaluation. Achieved results were statistically processed and the dependencies of thread length (m) and tool life (min) respectively on the cutting speed were plotted. The types of tool wear have been also analysed at individual cutting speeds.

Several models of FDM machines, characterized by different architecture and hardware components, have flooded the market in the last 5 years. As a result, given the high sensitivity of FDM to the specific machine characteristics, the search for optimal printing parameters is a renown problem. This two-parts paper proposes an easy-to-follow and low-cost procedure for the characterization of any given FDM machine. The method allows the evaluation of the effects of a wide selection of FDM process parameters on the quality of 3D printed parts. The first part focused on the definition of a series of metrics to be measured on a series of test prints to evaluate the quality of the produced parts. The evaluation of seven quality parameters on a single print is made possible thanks to: i) a specifically designed specimen that is made available to the user and ii) a rigorous and repeatable measurement procedure, which are both discussed in the first part of the paper. This second part presents the characterization procedure, the statistical tools used in the experimentation (DOE tools and principles are adopted throughout the experimentation) and provides guidelines to be used for the characterization of any FDM machine. The whole procedure is tested on a desktop FDM machine to demonstrate obtainable results, proving the efficacy of the proposed methodology and highlight strengths and drawbacks of the approach.

In this work, the microstructure and properties of the first-Republic Czechoslovak circulation coins were studied. The variety of the coins at that time was shown. Significant differences in microstructure in the direction of forming and in the normal direction to the surface direction have been confirmed. For some coins, visible features of recrystallization were shown, which suggests the coinage at higher temperatures. The chemical composition of coin alloys was also studied. In most cases, it was consistent with the declared chemical composition by mint. Significant differences in the hardness of the coins were found, which confirmed the different experience of numismatics with the abrasive resistance and the preservation of different coins. The quality of the design and the material composition of the coins confirm the long-standing experience with coinage in the Czech lands, despite the fact that, after the Austro-Hungarian Empire, the mining industry was struggling with big problems (eg stolen raking machines, lack of Czech mining experts). The first-Republic circulation coins represent the best in the history of the Czech and Czechoslovak coinage industry.

The aim of the article is to verify dimensions of the hydraulic arm column (the necessary cross-sectional area) by analytical dimensional calculation and thus to design a lifting rotary arm which will be located on the pick-up car body (Figure 1). After the analysis of dimensions, the next step is creation of the structure in FEM program and then a numerical analysis will be carried out for verification of stress in the structure already with the values that are not available for the preliminary design (e.g. the structure weight). The next step in the solution will be to import the proposed and by strength calculations checked geometry into the multibody system program, where the dynamic response of the structure will be monitored, depending on the size of the load and the movement possibilities of this mechanism.

The usage of the high-energy electron beam source enables repeated surface quenching of chosen areas of an engineering part surface. Different techniques of electron beam deflection allow creating of hardened layers of different shapes and thicknesses. Experiments were carried out with 42CrMo4 (1.7225) steel. The deflection modes tested were one-point, 6-point, 11-point, line, field and meander. The influence of process speed and defocusing of the electron beam was also taken into account. The electron beam surface quenching resulted in a very fine martensitic microstructure with a hardness of over 700 HV0.5. The thickness of the hardened layers depends on the deflection mode and is affected directly (except field deflection) by process speed. The maximum hardened depth (NCHD) was 1.49 mm. Electron beam defocusing affects the width of the hardened track and can cause extension of the trace up to 40%. The hardness values continuously decrease from the surface to the material core.

The experiment described herein focused on quantitative evaluation of carbides in the martensitic microstructure of X105CrMo17 steel. Carbides form as a result of the varying solubility of carbon and alloying elements during solidification and cooling. They possess high strength and hardness and their morphology plays a major role in mechanical properties of steel. In order to determine the relationship between carbide morphology and mechanical properties, several characteristics must be measured accurately. In this case, quantitative evaluation of carbides by means of optical microscopy and image analysis software were employed. Samples of the above-identified steel were quenched from various temperatures in order to obtain various levels of chromium and carbon dissolved in the martensitic matrix. They were then tempered at various temperatures to provide secondary hardening through precipitation. Furthermore, volume fractions and equivalent diameters of particles and the surface area density of particles were measured by metallographic techniques. Hardness was measured to assess the impact of heat treatment on strength. From the values collected in this manner, relationships between heat treatment and hardness were derived and an optimal heat treatment sequence was proposed for obtaining maximum hardness.

The give paper is closely connected with the analysis of the normal force relating to the winding mechanism referring to production or manufacturing of raw tyres. The attention is mainly paid to the calculation of normal force during the manufacturing process when the individual constituents of raw tyre are pressed-in. The dynamic analysis as well as the calculation of the given normal force was done for raw truck tyre. The simulation of the movement and dynamic analysis for the given kinematic conditions as well as appropriate input values were solved in Solid Works - modeling computer program. Courses of normal forces for the first one set and the second one set of winding arms in dependence on lever position are in graphitic form. Based on the dynamical analysis, it can be concluded that, the second one set of winding arms does not have any influence on the quality of the produced car tyre.

Paper is focused on the area of the energy devices working under the higher temperatures and pressures. It deals with repair of new and operational-loaded components of steam and gas turbines (valve and turbine chamber, transmitters, vane carriers, flap-lockable valve bodies and so on). Generally, there occur different types of defects at production and operating of these parts. Many defects are caused by casting (shrinkage cavities, pores, cracks) and fatigue defects. Eventually, there can occur also production defects. Moreover, most of the defects in the mentioned parts generally take effect not until during the subsequent technological operations. However, in such phase of production, only welding technology can be used to repair the given part. That's why as a goal of this paper there was to find such repair welding procedures which ensure the serviceability of mentioned devices in the standard mode indeed at application of the lower tempering temperatures in comparison to the commonly requirements for material GX12CrMoVNb9-1. Lower tempering temperatures have a strong influence on elimination the deformation as well as on the surface oxidation of the machined components.

The article deals with the monitoring of wear of truck oils in order to determine their wear. The research part is focused on engine oils, tribology and analytical methods for evaluation of oil degradation by abrasion particles. Thanks to these non-invasive technologies for monitoring and analyzing engine wear trends, an optimum oil change interval can be effectively set. The experiment analyzes engine oil samples from trucks and found the values of metal particles. Reference values for oil degradation levels are determined based on trend analysis. Metal abrasion particles and total impurities are determined and the state of the oils is evaluated experimentally.
Optimal oil exchange iterval must be adjusted based on experiments. Wear of the truck engines is very individual with respect to the service life of the oil. The shortening of the interval is suggested with respect to the evaluation of the experiment. The aim of the article is to minimize the negative effects of abrasion during truck operation.