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Shape of graphite in graphitic cast irons is the most important microstructural parameter affecting mechanical properties. The paper deals with evaluation of the shape of graphite in cast irons by shape factor (circularity). Three specimens of graphitic cast irons with different shape of graphite (lamellar, vermicular and nodular) were used for experiments. The aim of this study has been to understand the influence of microstructure (especially shape of graphitic particles) on mechanical properties of graphitic cast irons. However, the evaluation of shape factor is a subject of interest in many fields of applications such as medicine and industrial processes, not only materials engineering. The shape factor plays an important role in materials science as a way to understand the relationship between microstructure and mechanical properties of technical materials.

This paper deals with the comparison of an analytical solution of the temperature field of a steam boiler pipe membrane wall using a numerical method calculation in the COSMOS/M programme. The result analysis showed that analytical calculating methods which are limited to 1D and 2D task types can be used for the approximate calculation of temperature in the selected locations of the membrane wall. With these methods it is not possible to obtain a complex view of the heat loading of the entire membrane wall or of the stress conditions caused by the thermal and pressure effect of steam-water mixture in the wall pipes. The results of numerical simulations have provided a complex image about the temperature and pressure distribution in the entire membrane wall of a steam boiler taking into account the material properties.

Composite materials play an important role in the machine design. Laminated composites have a lot of advantages but in some cases they show different limitations that are caused by stress concentrations between layers. Discontinuous change of material properties is the reason for occurrence of interlaminar stresses that often cause delamination failure. Delaminations in layered plates and beams have been analysed by using both cohesive damage models and fracture mechanics. Modelling of composite structures by finite element (FE) codes to effectively model delamination is limited. Previous efforts to model delamination and debonding failure modes using FE codes have typically relied on ad hoc failure criteria and quasi-static fracture data. Improvements to these modelling procedures can be made by using an approach based on fracture mechanics. This approach allows us to predict the growth of a pre-existing crack or defect. A study of modelling delamination using the FE code ANSYS was conducted.

An article provides an overview of production and corresponding issues of one of the most important component of a satellite dish - a high frequency optic mirror that polarizes signals caught by a parabola into a sensor connected to computing (so-called receiver).
The article describes an issue of production of high frequency elliptic and hyperbolic optic mirrors forming one of the most important functional components of parabolic satellites designed for ALMA, the biggest and the highest located international astronomic radio telescope in the world. It is situated at a high plateau Chajnantor in Chile, South America.
Individual parts of the article are outlined in a sense of a flow of a production technological process including both theoretical and practical analyses of the given issue. A content of the article leads especially to a description and explanation of causes of individual problems during production of elliptic and hyperbolic optic mirrors.

The effect of the T62 post-weld heat treatment on the tensile strength of AA6156-T4 friction stir welded joints is studied. To this aim, the 0.2% proof stress and the tensile strength of as-welded and post-weld treated joints as function of the rotating and welding speed was analyzed performing a complete factorial design with three levels for each studied parameter. Statistical analyses were carried out to establish empirical models of the tensile properties of the joints as a function of the studied welding parameters. The obtained models were validated through statistical tools such as Mallow's CP, S, R2 and R2(adj). The developed regression models can be effectively used to predict the mechanical proprieties of the joints at 95% confidence level.

Fractographic methods derive their knowledge from Euclidean geometry, set theory, metric theory and chaos theory. In engineering technology, the fractography is primarily used for modeling of fatigue and intergranular fractures. As such defects are not smooth due the principle of their origin, they cannot be described using ordinary mathematical tools. However, if the conditions of self-similarity are met, fractal geometry means can describe various irregular, incomprehensible, crooked or fragmented geometric shapes. Fractographic description of the fracture profile allows more accurate quantification of fractures and it also enables identifying possible causes of their initiation. This study contains several examples of specific cases of Cr-Ni steel failures and a basic explanation of their fractographic description.

The article deals with the failures caused by heat treatment and their identification. The various types of tool failure are occurring from the design through to the tool application stages. Heat treatment naturally plays a major role due to its significant influence on the tool properties, and indeed most defects appear after the heat treatment stages. There are many methods how to study failures of tools and gadgets. One of the most important is metallographic investigation. Metallography is very important part of failure analysis. Thanks to microstructure analysis can be evaluated crack morphology and relationship between the failure and microstructure. Investigation can be performed using classic optical microscopy or SEM (Scanning Electron Microscopy). The aim of this paper is classifying these failures according to type and occurrence to deliver practical solution.

The article deals with the area of non-conventional technologies, specifically with the effect of concentrated radiant energy on the polymer material. There was studied the laser beam and its application to two different types of polymeric materials in details. PMMA, as a representative of the amorphous polymers and POM, which is a crystalline polymer, was used for experimental cutting as they are frequently applied in industrial practice. The input technological parameters were changed during machining followed by evaluation of their interaction with the concentrated radiant energy of the laser beam. The results were subjected to statistical evaluated by regression. The regression analysis was used as the main mathematical tool, concretely using linear regression models with confidence intervals for predictions on the confidence level 0.95.

Thermal treatment of the aluminum alloys significantly affects their final mechanical properties. However, the process of such thermal treatment is influenced by many variables and the correct choice of these technological parameters is a prerequisite for achieving their required properties in the manufactured part. This paper evaluates the effect of thermal treatment conditions on the time course of hardness for EN AW-6082 alloy during artificial aging. For the experiment, the solution annealing temperature of 520°C was chosen in combination with three different holding times at this temperature and then also 3 different initial temperature of the material before cooling in water. The effect of the thermal treatment parameters was subsequently monitored by the Brinell hardness time course at 3 selected artificial aging temperatures.

This article deals with research of replica preparation of polypropylene surfaces machined by a laser beam. For the production of replicas, we decided to test the material SILOFLEX© which is mainly used in dentistry. There we are also looking for expertise in the preparation and application of this material on the surfaces. Subsequently investigated methods of statistical evaluation. In this article the cluster analysis is primarily used, this analysis uses four basic methods: Ward's Minimum Variance, Furthest Neighbour, Weighted Pair-Group and Pair-Weighted Centroid Group. The results are there also demonstrated using Abbott Firestone curves. The result of the article is to demonstrate the similarity of the amplitude of surface roughness parameters using above mentioned four methods Cluster analysis using Cophenetic correlation coefficient and using average values of cumulative totals compiled into the Abbott Firestone curve and the replica of the original surface. Original surfaces and replicas will be scanned using a contactless 3D scanner Talysurf CLI 500.

The wear of rails and rail wheels is important problem in rail traffic. The change of the shape of the wheel profile has not only a great influence on the dynamic properties of the vehicle (like stability, safety by passing curved tracks, etc.), but also affects the ride comfort of passengers and environmental insults. In extreme cases it can cause rail derailment, which is unwanted status. For these and other reasons, great effort is brought to create a software, which would be capable to compute the wear of a rail wheel profile. The presented article demonstrates how the change of the rail profile influences the resulting contact stresses. The wheel and rail geometries were created by using the CAD software CATIA. For the creation of the rail profile, the PYTHON programming language was used, because the imported .step file caused inaccuracies during import. The contact stresses were computed by using the commercial FEM software ABAQUS, and the results were compared with other methods which are used to calculate contact stresses.

The submitted paper presents possibilities of a simulation for a real manufacturing process in a company taking the risks into consideration. The risks may result from various sources in manufacturing environment. The most significant ones include a human factor, the processes in general and environs where the manufacturing process takes place. Risk can be viewed as a state where there is a possibility of a loss but also a hope of gain since one would never jeopardize the loss if there were no chance of a win. Because of the argument that a risk is perceived differently depending on the observer's experiences and objectives, it has become increasingly important in organisations to create awareness and gain information of potential risks. The paper is aiming to present the possibilities how to avoid such risks or to decrease them to an acceptable level through simulation and modelling tools.

While down-scaling of micro milling process is similar to the conventional process, there are specific issues that differ from macro machining due to higher ratios of feed per tooth to tool radius and tool run-out to tool diameter, size-effect, minimum chip thickness, elastic-plastic deformation, microstructure effects, etc. One of the challenges in micro machining is attaining accurate and reliable machining parameters, which can reduce tool wear and breakage to achieve higher productivity and quality at a lower cost. Therefore, this paper presents a new mechanistic model for predicting the precise process parameters considering material properties and principles of micro-milling under various cutting conditions. The proposed model also takes into account the nonlinearity and dynamics of minimum chip-thickness, micro-milling cutting forces considering cutting, as well as edge and damping coefficients into. The predicted stability lobes and the stability limits from experiments are in sufficient agreement. The research of micro-scale milling parameters is significant to improve the precision of machined parts, reduce the wear and tear of the micro-milling blade and extend the life of micro-tools.

An article deals with a definition, concept, development, calculation and construction of a prototype of mechanical regulation of a turbine ventilator using a whirling turbine reducing an amount of ventilated air.
The whole mechanical regulation solution is situated at a central shaft with arms. At low air velocity, a rotation nozzle is pulled out fully from its cover and works with a maximum suction capacity. The rotation nozzle starts to pull in its cover at higher air velocity, which protects the blades from push of air, which would slow down the whole turbine. A vertical move of the turbine is provided by an inner mechanism functioning basically as a centrifugal regulator. The advantage of this concept lies in not only suction regulation, but also protection of the rotation nozzle from a damage in case of adverse weather (the rotation nozzle stays inserted). The article describes individual development stages from a concept up to construction, including the final visualisation of the prototype solution of the mechanical regulation of the turbine ventilator using the whirling turbine.
The mentioned innovative solution of the mechanical regulation is very up-to-date thanks to its simplicity and nonservice operation. It is just the matter of time when one of the producers would be interested in the turbine ventilator solution and it would be introduced into a market space.

The macroscopic structure of a casting has a direct impact on its mechanical properties. The porosity and homogeneity of a casting closely correlate with its tear strength characteristics. In order to achieve the best mechanical properties, it is necessary to eliminate internal defects in a casting. The elimination of such defects can be achieved through the suitable adjustment of the input parameters of high pressure die casting machines prior to starting the actual casting cycle. This method is useful for companies that produce castings on the basis of supplied pressure forms, whereby it is impossible to influence the design of the gating systems. A much more appropriate way to influence the homogeneity of a casting is to design the gating system so that possible shortcomings are already underpinned and excluded in the design and development phases. By adjusting various elements of the gating systems it is possible to achieve significant improvements in the properties of a casting. The construction of the gate has the biggest influence on the final homogeneity of a casting. The gate is the point at which the modulation of the melt flow rate takes place for the filling of the die cavity. The mode in which the cavity is filled and the speed of the melt flow rate are the main determinants of the final characteristics and properties of a casting. This paper presents an analysis of the macroscopic structures of castings produced under various gate construction modifications and their effect on the mechanical properties of those castings. Conclusions, which are drawn on the basis of the detailed analysis, describe the correlation between the macroscopic structures and the mechanical properties of castings with precautionary measures that are used and implemented directly in production.

The influence of the dynamic behaviour of the machine tool/workpiece system on the surface accuracy plays an important role in finish machining. In particular, the machine tool/workpiece dynamics determines the topography of the machined surface, which is crucial in determining the quality and performance of a mechanical part. A model to predict the dynamic effects of the cutting process in turning, as part of a machining simulation framework, is presented in this paper. Thermally, kinematically and dynamically induced errors can be easily implemented into the proposed model. Finally, several examples of the use of this model under different turning conditions are presented and compared to typical machined surfaces. The proposed model can effectively compute the roughness, form and dimensional accuracy of a turned surface.

Deflection of cutting tools under the action of cutting forces has a significant influence on the error of machined surface and the stability of cutting process. Considering the complex geometric structure of cutting tools lead to higher calculation accuracy of the tool deflection analysis. Therefore, CAD models of double-sided solid ball end mill and helical drill bit was created in this study. The impact of tool material and clamping of the tool under the influence of cutting forces individually in three axes was obtained via finite element analysis. An error of the numerical model was less than 7.2% and has been validated by analytical calculation. Geometric errors in the case of die and mold manufacturing are provided below or close to 0.02 mm. However, due to the force effect of the cutting process it is not recommended to use HSS tools as the analysis confirmed. Stiffness of sintered carbide tools was more than doubled.

Tool steels are a widely-used material with well-known heat treatment procedures for obtaining the desired mechanical properties. Their weakness is the presence of sharp-edged carbides which compromise the material's toughness. When produced by conventional metallurgical routes, high-alloy steels, such as X210Cr12 (1.2080) and X155CrVMo121, contain sharp-edged M7C3 carbides which remain stable even at high temperatures. As these carbides form as early as in the solidification stage, there is no practical conventional heat treatment for removing them or for converting them to more favourable carbide types. As a result, unconventional methods must be sought for these steels. One of them combines short-time conversion to semi-solid state and subsequent thermomechanical treatment. This method was used with both tool steels named above, with a great emphasis on the choice of the heating temperature. The results showed that at an appropriate heating temperature and deformation magnitude, very fine structure can be obtained in which the matrix consists of grains of the M-A constituent and carbide precipitates. In X210Cr12 steel, hardness values of up to 862 HV10 were achieved. In X155CrVMo121, the hardness level was 859 HV10.

The article describes the course of a pressure test that was made to determine the maximum force in the case of breaking the integrity of the casting. Observation of the forks arm deformation can be done with using sensors on the universal tensile testing machine. Using a high-speed camera to monitor this test will provide results in digital form that can serve to further research. Subsequently, analysis of the material properties of the AlSi7Mn0.3 casting is described, using the methods of evaluation of mechanical and structural properties. Periodic tests check the castings status to ensure recurrent quality in order to achieve the required safety in accordance with the standards for road vehicles.

The aims of the present work were focused on evaluation of the processing steps on the microstructure and mechanical properties of titanium grade 4 material. The rod was subjected to Conform SPD processing which combined multiple passes throughout the ECAP with consequential cold working which reduced the sectional area by 80%. The microstructure of the prepared material was well-refined showing presence of phases whith sub-micrometre dimensions. The mechanical properties of these materials were evaluated by hardness measurements and by compressive strees-strain tests and by tensile stress-strain tests, both performed at laboratory temperature. The highest hardness of 330 ± 6 HV 1 was achieved by the material prepared by Conform SPD process while the same material in its initial state showed hardness of only 170 ± 4 HV 1. The Conform SPS process also increased the compressive yield strength and compressive strength reaching 1033 MPa and 1608 MPa, respectively, while the tensile test resulted in yield strength and ultimate tensile strength of 1136 MPa and 1142 MPa, respectively.

Modern cutting tools with high quality attributes are very important factors for companies that want to increase their production efficiency and product quality. Cutting tool properties include high durability, endurance and cutting power. Quality shapes and surfaces of cutting edge micro and macrogeometry are also important. This article deals with cutting edge microgeometry on sintered carbide end mill tools. Drag finishing technology is used for preparation of cutting edge microgeometry. Two process media are used during the experiment. Due to the different process media, the final surface quality will also be different. Nowadays, cutting edge preparation is one of the basic but inseparable parts of development and production of cutting tools. Microgeometry quality affects the behaviour of cutting tools during the machining process. The behaviour mainly includes cutting forces, friction and vibration. The impacts of drag finishing on the functional surfaces of the cutting tool are investigated in this article. An IFM G4 microscope is used for measuring the cutting edge microgeometry.

This paper focused on axial flow pump high operation, reliability, and long service life at different frequency of rotation (DFR). The efficiency of an axial pump varies considerably depending upon the conditions under which it must operate. This article concentrates methods related to the reliability analysis of pumping system operation by a frequency converter. Initially, it is focused to analyze the behavior of individual characteristic curves of the axial pump to find how can be applied for the determination of the most efficient frequency of rotation. Axial flow pumps are often controlled by adjusting their rotational speed, which affects the resulting flow rate and output pressure of the pumped fluid. In addition, the head and flow of fluid transported at different frequencies of rotation, to produce a map of reliability characteristic curves to verify the similarity rules for pumps recommendable operating region are discussed. The results showed that the recommendable operating region for a different revolution per minute of axial pump can be determined with efficiency. If the axial flow pump is driven outside its operating region, the efficiency decreases, and the reliability and long service life may be affected.

The paper deals with design proposal of a cover part of a strength bumper, which is tasked with creating the outer design lines of an automobile without sharp edges according to legislation in force and also with protecting a vehicle against damage. The cover part serves for covering the strength part of a back strength bumper, which will be equipped with a winch and used in off-road vehicle Nissan Patrol Y61. Another aim is to perform a FEM analysis of the strength part of the bumper loaded by towing force of the winch and thus to verify a safety of the structure. The next solution of the issue will be an approach to real testing, which will verify a correctness of a numerical computations and also fulfilment of the purpose of creating the structure. Bases of FEM analysis and practical experimental verifications of the structure will be also used as a background for granting approvals, certifications and type approval by superior authorities.

The object of this article is to analyse the stability of changed three axle rail bogie structure, which is characterized below by higher axle loads combined with good operational properties. The occasion of change was the unstable behaviour of the system during prototype development. For validation of the structure design, there has been created a substitute simulation model in program Simpack, by which the computations were performed for partial system. Model represents only elasto-kinematic properties of the system. For stability analysis of the system, there have been a set of boundary conditions from different degrees of freedom to state out of balance. Simulation calculations show, that up to one oscillation in the y-direction, which is damped in real bogie by friction in suspension and dampers Lenoir, is the system after all deflections in initial condition. Substantial unstable behaviour does not show already.

Theoretical analysis has been carried out for the determination of the analytical dependences connecting various parameters of contact area between wheel cutting surface and workpiece, such as length, width and arc length in the case of flat face grinding with preliminary inclination of spindle axis. The role of factors, such as angle of preliminary inclination of the spindle axis, grinding depth and grinding wheel diameter, in this process, are established. The capability to define the above mentioned parameters permits the calculation of the contact area between wheel cutting surface and workpiece. In addition, with the proposed methodology, it is possible to correctly determine the value of cross-feed, in the case of multiple-pass processing scheme, which, as it is known, should be consistent with the value of contact width of wheel cutting surface with workpiece. It can be guaranteed that on the ground surface there will be no areas unaffected by the wheel. In the case of through-feed grinding the obtained theoretical dependences make it possible to determine the processing conditions, taking into account the allowable value of flatness deviation. Finally, the latter, contributes in improving flat face grinding process and thus expanding its technological capabilities.

Article deals with problematice of influencing mechanical properties - tensile strength and hardness - of grey cast iron by heat treatment - refinement. Refinement could be in special cases applied also for grey cast iron castings in order to achieve special parameters of hardness and tensile strength of parts for specific purposes. Hardening and tempering of casting sis commonly used for ductile cast iron, but in special cases could be applied also for grey cast iron castings. Refinement - hardening and tempering - was provided on samples from materiál EN GJL 150, EN GJL 200 and EN GJL 250. Afterwards, measured values of tensile strength, hardness and fractography of materiál in poured state and after tempering on temperatures 250, 350 and 450°C after quenching from austenitization temperature 920°C were compared. Achieved results are formulated in the evaluation part of article.

The stability of the machining process is depending on the machined materials properties. But the material properties are influence by the heat treatment process and in this case it is forging. For these study three different company made the "same" forging process and then the material properties are evaluated and their influences on the cutting process were monitored. For the tests the steel DIN 18 CrNiMo 6-7 was used. This material is typically used for the gear wheels where the cutting tools by tool steel is used for the machining. So for the tests the mills from tool steel were used and during the machining the cutting tool life and cutting forces were monitored.

Grinding is an overly used finishing technology, which can obtain very accurate surface integrity. The desirable surface quality after grinding is one of the most relevant parameters. In production, surface preparation such as chromium plating, nickel plating, etc. are more prevalent. These platings are used as protection against corrosion, erosion, abrasion and as a material for the renovation of worn parts. This paper discusses the change of nickel coating machines, which has an influence on surface integrity and microstructure after grinding. The team has built a completely unique and new technical solution for the covered equipment which had never been built in the past. The input parameters were selected based on past experience in the company, related to the area covered in this paper.

Current contribution contains of results of experimental measurements performed within the determination of initial raw feedstock materials moisture content and its influence on final properties of subsequently produced briquettes. A birch wood chips samples with five different moisture contents, specifically 5.0%, 7.6%, 16.7%, 19.0% and 27.7%, were used for experimental investigations. Investigated briquette samples were produced by hydraulic high-pressure briquetting press Briklis, type BrikStar 30-12 with cylindrical pressing chamber of 50 mm. All investigated briquette samples were produced under the same conditions with constant adjustment of all parameters of used briquetting press. A basic physical-mechanical properties of investigated briquette samples were used as a criteria of investigations evaluation. All measured values were subjected to the statistical analysis. Final evaluation of measured values indicated that best results were achieved by briquette samples produced from feedstock material with moisture content equal to 7.6%. Evaluation of current investigation also proved that if moisture content was higher or lower, the quality of produced briquette samples decreased.

Microstructure and mechanical properties of powder metallurgically prepared AlSi24Fe3 alloy are presented in this article. The alloy was prepared in form of rapidly solidified ribbons by melt spinning process. Consequently, the ribbons were crushed into powder in a ball mill and compacted by spark plasma sintering. Grain size of prepared alloy was less than 1 μm, Vickers hardness HV0.1 reached value 214, yield strength and ultimate compressive strength were 611 and 778 MPa, respectively. To obtain material with possible self-healing proprerties, it was necessary to enrich material by fine dispersed Ag2Al particles. The AlSi24Fe3 powder particles were sputtered by 5 nm layer of silver before sintering. The total amount of Ag in bulk sample was approximately 0.1 wt. %. The microstructure of Ag containing alloy was comparable to the basic one. The Ag nanoparticles were present on several particle boundaries. The influence of Ag presence on Vickers hardness of the material was not observed, as the values HV0.1 was 212. After a heat treatment (450 °C/ 1h), silver transformed to equilibrial Ag2Al phase, present in material in form of nanoparticles no more decorating strictly the particles boundaries.