Fulltext search in archive

An article deals with a realization and a statistical evaluation of a pressure test using a hydraulic testing machine ZD 40 in order to determine a strength of a designed implant prototype of a femoral component, more precisely a maximal force F that breaks a material and creates a crack. It is needed to make real testing samples of the new implant prototype of the femoral component for this purpose. Four pieces of testing samples are made in cooperation with the company in Velka Bites. Because of a price and availability in a range of offered cast materials testing samples are made of a bio tolerated cobalt alloy Co-Cr-Mo that is frequently implanted to a live organism. The implant prototype of the femoral component is designed from evaluated CT data of a patient's affected knee-joint (a femur distal part, a proximal tibia part). An individual 3D model of the implant prototype of the femoral component is created on the basis of editing of gained data in software CATIA.
The created 3D model is converted to *.stl format with a high resolution. Subsequently, the shell implant of the femoral component (a master model) is made using an additive method FDM (Fused Deposition Modelling). The next production method follows - production of a ceramic mould and casting of the real implant prototype of the femoral component from the bio tolerated cobalt alloy Co-Cr-Mo.

To describe the machining process and information of mechanical parts in petroleum engineering, the paper defines MBD machining process model from the perspective of process parts; analyzes evolutionary law of geometric features information in the course of part machining process and creates the concept of procedure machining cell; makes clear description about machining process based on procedure machining cell sequence to achieve the expression of machining process information; analyzes geometric features of procedure machining cell, proposes extended AAG based on AAG by combing with examples and links with attribute information table to complete the modeling of geometric and non-geometric features information about procedure machining cell. The research made in this paper provides a basic framework for integration of process information in 3D CAPP system.

The article presents the results of Technical University in Košice Faculty of Manufacturing Technologies Department of production processes operation and Technical University in Ostrava Physics Institute Liquid jet workplace cooperation in the area of operational states diagnosis of manufacturing systems with abrasive water jet technology (AWJ). Within the operational states diagnostics is the impact of selected technological parameters on technological head vibrations studied. Based on an extensive set of experiments are original graphical dependences determined of the abrasive mass flow and abrasive sieving impact on the vibrations parameter - technological head vibrations acceleration amplitude of manufacturing system with AWJ technology. In addition to the original graphical dependences are in article new knowledge formulated in the area of science and research and recommendations for companies that operates manufacturing systems with AWJ technology.

This work summarizes recent results in the field of intermetallics achieved during the research in our department. The research was focused on high temperature materials, shape memory alloys and hydrogen storage materials. In the case of high-temperature intermetallics, the development of TiAl-Ti5Si3 and NiAl-Al2O3 composites and Fe-Al-Si based alloys is described. During this research, powder metallurgy using reactive sintering has been established as an innovative and promising method for easy preparation of these materials. This method is also currently being tested and optimized for NiTi shape memory alloy. Another important property of several intermetallics (as LaNi5 or Mg2Ni) is the ability to store hydrogen reversibly.

The article deals with numerical simulation of induction heating process as a coupling of electromagnetism and heat transfer with the scope to surface temperature optimization. The article presents how the position of the inductors used in the induction heating process influence the resulting temperature of heated surface. The scope of the article is to show methodology to optimize surface temperature by numerical approach.

The properties of plasma nitride layer are determined except technological parameters by chemical compositon and structure of steel. Experiments were carried out on ARMOX 500T steel. Firstly, the samples of steel were carburized and isothermal hardened. After quenching the course of microhardness was measured from surface to the core of material. Samples were cutted off on metallographic saw and subsequently grinded from the surface to the core of material. All depths of grinded surface from surface to the core were exactly defined. The chemical composition was verified in each prepared samples. Samples with changeable content of carbon were nitrided by plasma nitriding technology. All properties of plasma nitriding layers were evaluated.

The paper describes specific phenomena of semi-solid casting process, especially rheo-casting method SEED, which uses mechanical swirling for reaching proper structure in semi-solid state. The eutectic segregation during processing of semi-solid slurry can cause specific casting defects. Heat treated alloy AlSi7Mg0.3 was applied for producing castings. For observing structure, metallographic observation by light and SEM microscopy was used as well as spectral analysis.

The article deals with influence of chemical etching and polishing on some roughness parameters of titanium parts surface, designed for implantation into human organism. Titanium alloy Ti-6Al-4V was used for the experiment. Analysed samples were created by conventional mechanical machining methods as milling, grinding and polishing. Influence on surface and quantity of removed material by acid solution was analysed. Three methods of sample surface finishing were used, each resulting in variety of surface quality, and then two methods of chemical polishing, differed by reaction time of acid with samples surface. The samples surface was analysed optically, using stereo-microscope and evaluated roughness parameters as arithmetic average roughness Ra, ten-point mean roughness Rz, profile skewness Rsk and kurtosis Rku were measured. The modification of these parameters after the reaction was measured and analysed.

Aluminium alloys are widely used materials and their properties are constantly being improved. The enhanced properties can be achieved, for instance by alternation of chemical composition or processing route. Severe plastic deformation leads to an increase of strength due to a grain size reduction. Two Al-Mn-Fe-Si alloys differing in Zr content were subjected to four passes of equal channel angular pressing. Grain size was re-duced from 100 μm to 0.5 μm. In the course of subsequent annealing to 400 ◦C the grain size rose moderate-ly; at 450 °C both materials recrystallized and new defect free grains were formed; with fraction of high angle grain boundaries nearly 1. The recrystallized grain size was comparable with the grain size after cast-ing. Moreover, high density of α-Al(Mn,Fe)Si particles precipitated during annealing in both alloys.

The contribution contains results of bonded joints strength tests. The tests were carried out according to the modified standard CSN EN 1465 (66 8510). For bonding the spruce three-ply wood of 4 mm thickness was used (according to CSN EN 636). The test samples of 100 x 25 mm size were cut out from a semi-product of 2440 x 1220 mm size in the direction of its longer side (angle 0°), in the oblique direction (angle 45°) and in the direction of its shorter side (crosswise - angle 90°). The bonding was carried out using eight different domestic as well as foreign adhesives according to the technology prescribed by the producer. All used adhesives were designated for wood bonding. At the bonding the consumption of the adhesive was determined. After curing the bonded assemblies were loaded using a universal tensile-strength testing machine up to the rupture. The rupture force and the rupture type were registered. Finally the technical-economical evaluation of the experiments was carried out.

This paper focuses on the structural design of screw tools in briquetting presses used for the production of solid, high quality, bio fuels. The primary objective is to analyse the screw tool geometry and determine a procedure for its design, specifically the theory involved with the pressing tool and force relations which are necessary for the verification of the proposed tool geometry and its strength analysis. In designing the main drive of the press, procedures for determining frictional performance of the screw press are used. Familiarity with the above mentioned procedures forms the basis for research into new tools in screw briquetting presses that will improve the service life and competitiveness of the technology.

At logging and at the subsequent wood and wood semi-products treatment and also at fruit trees treatment the fine grained loose waste is arising, e.g. wood dust, saw dust, shavings, chips, bark etc. One of possibilities of its meaningful utilization is the briquetting technology, which product are briquettes determined for energetic utilization (combustion). In the paper the experimental results are published. The briquettes quality evaluation was their aim. For the tests pine bark chips, fir chips, spruce shavings, spruce sawdust, apple chips and cherry chips were used The basic physical-mechanical properties were the evaluation criteria. Following properties were determined: ash amount, gross calorific value, total moisture content, density, rupture force, length, diameter, weight and mechanical durability.

The analysis of non-metallic initiating inclusions in fatigue live field is studied. The testing material for experiments is CSN 41 5340 steel (corresponds to 41CrAlMo7-10 or 1.8509). This steel is suitable for plasma nitriding process. The samples were heat treated and subsequently plasma nitrided, then subjected to the fatigue bending rotation tests. According to the principle of the tests are the conditions set to constant speed and decreasd load to 107 cycles if does not the fatigue fracture of the sample happens. The thickness of the diffusional nitride layer has been won using the microhardness measuring from the surface to the core of the samples. Using the fractographic analysis the nucleation point of fatigue crack has been evaluated. In the case of initiating inclusions the size and the chemical composition was measured. Comparing the won data to the plasma nitriding proces new results have been obtained.

Approximately equiatomic alloy Ni-Ti is commercially most successful member of shape memory material group. This paper concludes basic knowledge about properties, ways of preparation and possible applications of this unique material in medicine, industry, construction or everyday life.

The solution of the aerodynamic task is a very complex issue. An accurate description of the aerodynamic field is used for the specification and the solution of an aero-acoustic task. With the numerical modelling onset the possibilities of investigation of the flow around body are still expanding. The aim is to establish basic parameters by which the flow field around the body is described. This paper deals with the numerical modelling of the flow around a cylinder and a sphere and with the evaluation of the parameters (coefficients) for these bodies. The modelling is performed using the software tools Ansys Fluent and OpenFOAM. The basic setting of the numerical simulation is described and test of the calculation stability and mesh quality for a given task is done. The calculation setup is briefly shown for the computational tool OpenFOAM. At the same time, the experimental result is shown in this paper to verify the results of the numerical simulations. The experimental equipment - a wind tunnel is specified by its basic parameters and possibilities for the aerodynamic task measuring. Experimental data are obtained using by hot-wire anemometry - one-wire and two-wire probe.

This study deals with a numerical simulation of CO2 dispersion after combustion of Ethanol. Numerical simulations were carried out with Reynolds averaged Navier-Stokes (RANS) approach. The mixture fraction theory was used for modeling of combustion. There were tested k-ε and k-ω turbulent models. Results obtained from numerical simulations were compared with results from an experiment.

The paper analyses the possibilities of modification of cutting tool geometry in order to preserve a protective plastic zone of material at a cutting tool. Based on the results of model experiment as well as practical verification, a rapid increase in tool life has been achieved. The tool life is dependent on the size of the shortened rake face. Optimization of the tool face size enables to achieve multiplied tool life when comparing with a classical cutting tool. A uniqueness of this processes is the formation of the two chips, one of which is a created plastic layer along the edge of the cutting tool. The application of the tool is possible only with the plastic material cutting. Experimental tests were realized with usually used steels.

This paper deals with evaluation of ground surface of Ti6Al4V alloy according to surface roughness. This titanium alloy has large scale of utilization, it is used for implants and surgical instruments. Significant problem during grinding of titanium alloys is generation of large amount of heat which can cause surface cracks, increase hardness of surface and increase of tool wear. Each specimen was ground on surface grinding machine by diferent cutting conditions. The roughness parameters Ra, Rq, Rz and Rt were measured five times on each specimen in each axis (axis y - direction of feed rate, axis x - perpendicular to the feed rate). The values of the roughness parameters (Ra, Rq, Rt and Rz) are presentated in the graphs where we can see the influence of the cutting conditions on these roughness parameters.

Biodegradation properties of magnesium and its alloys that can be used for implants are not satisfactory and cause serious problems. These problems can be solved by biodegradable surface coatings. Evaluation of biodegradation process of Mg-RE-Zr alloy surfaces after grinding and grinding followed by potential controlled electrodeposition of octacalcium phosphate (OCP) was investigated by electrochemical impedance spectroscopy measurements in this study. The potentiostatic electrodeposition treatment process was performed in water solution of 0.167 M CaCl2 and 0.1 M NH4H2PO4. The corrosion process on treated and nontreated samples after various exposure times was evaluated in 0.9% NaCl solution simulating body fluid environment at 37 °C. The significant increase of polarization resistance and time resistance against corrosion were found after electrochemical surface treatment.

The translation in this article analyses the technology of laser cutting, describes properties of laser cutting equipment the oxidation process of melting and sublimation laser cutting. In the article chemical composition of cutted material in the interaction with the quality of cutting edges from cut-outs is analysed. The measurement was performed on experimental samples made from steel grade S355 however the composition of chemical elements in each sample varied. On these experimental samples the cutting edges was examined for the purpose to find out the influence of chemical purity of material on the quality of components which were cut by using laser technology.

This paper deals with analysis of surface integrity of steel after laser beam machining (LBM). The paper discusses surface integrity expressed in term of rms values of Barkhausen noise and reports about variables affecting Barkhausen noise emission such as laser power, gas pressure, thickness of machined surface, focus distance and feed speed. The paper demonstrates variable degree of surface hardening due to elevated temperatures and the following rapid cooling. Except magnetic investigation of surface also stress state and structure observation are reported. This study demonstrates that thickness samples takes major role from the point of surface integrity expressed in structure transformations as well as stress state whereas influence of focus distance and gas pressure are only minor. Medium degree of surface integrity transformation can be driven by variation of laser power and feed speed.

The article presents the measurement results of the relaxation of long-term loaded compression springs manufactured out of non-alloy steel. The goal was to determine the differences between the interrupted and uninterrupted tests. During the relaxation test that lasted 5000 hr in a laboratory with a temperature of 22ºC, initial shear stress set at a value of 30% of the ultimate tensile strength of the material, decreased the strength of the springs with a wire diameter of 1 mm by 3.6%, springs with a wire diameter of 3.15 mm by 2.5%, and springs with a wire diameter of 5 mm by 1.3%. The difference in the results was found in tests 16 times and 4 times interrupted to measure the current relaxation. The results of intermittent tests cannot be considered as relaxation values for statically loaded springs. Conversely, when determining the maximum tension of quasi-statically loaded springs with respect to the relaxation, the uninterrupted relaxation tests cannot be used.

Regarding effects of environment factors on adhesive bonds belongs among key requirements influencing the adhesive bond strength. The aim of experiments was to set an influence of liquid contaminants on changes of the adhesive bond strength and to set whether a degradation process is an irreversible change that means whether degradation adhesives will restore their strength characteristics depending on the time. The adhesive bonds were placed into three liquid contaminants for the time 1, 2 and 3 months. The testing process was performed after removing specimens from the liquid contaminant (marked as 0), then after 24, 72 and 163 h. A considerable fall of the adhesive bond strength has already occurred in the first phase of the testing that means after 1 month of the contamination. The rate of the adhesive bond strength fall caused by the degradation process is in the interval 10 till 92 %. This undesirable process can be subsequently suppressed by a drying process of the liquid contaminant. The experiment results certified in most cases a positive influence of the drying process of the liquid contaminants on the adhesive bond strength.

Different powder metallurgical techniques have been intensively studied as candidates of methods suitable for fabrication of metallic biomaterials intended for orthopedic applications. The main advantage of powder metallurgical products is that they contain porosity which compromises their mechanical properties closer to those of human bone and allows transport of bodily fluid and growth of ne tissue through the implant. This enhances the healing process; moreover, the pores may be also impregnated by drugs or growth factors, which are eluted during healing and support the healing process. Recently, Ti-based and Mg-based materials have been the most investigated metallic biomaterials; therefore, the powder metallurgical methods are usually studied on those materials. In this paper, the most investigated methods will be summarized and briefly described.

Ammunition projectiles disposal armored facilities used hard core as the main effect. The hard core has a smaller diameter than the calibre of gun. The core of the projectile is made of tungsten carbide, titanium, molybdenum or depleted uranium with a hardness of 80 to 120 measures by the Rockwell hardness test. The core must be not only hard but also tough and have a high bending strength. Knowledge of the hard core chemical composition, which the attacker uses, is important in relation to provide ballistic protection, minimization of radioactive risk and optimization of conditions for disposing of old ammunition. The basic tool for detection of the necessary data is material analysis. This analysis provides information about the weight, chemical composition and material microstructure of the hard core.

The article describes main possible usage of results of dynamic loading simulation with using of computational simulating system MSC. ADAMS. AVT and simulating computational model of track vehicle undercarriage. Main contens of article is the descripton of using of results for design value make-up file of changes of vehicle chassis parts and its new operating settings. The second described possibility of results simulation calculations usage is making - up of aproximate relations for transaction of fast orientation calculations. The next possibility of usage of simulation results is the possibility to verificate of mathematic model. The optimalization of influence changes of several design value together is last mentioned possibility of usage of simulation calculations results in the contens of this article.

This paper focuses on verification of experiment of thermoelastic stress analysis by using numerical solution. Thermoelastic stress analysis is noncontact technique to obtain thermograms, thermographic images of the stress fields, by using an infrared camera. In the elastic part experimental results can be used to determine the value of the first stress invariant under adiabatic conditions. The experimental part is dedicated to the postprocessing of the measured data. Numerical solution was performed by finite element method in two softwares: ANSYS and ABAQUS.

The research into root causes of defects in cylinder head castings are described in the paper. Chemical composition of castings, evaluation of casting microstructure before and after the heat treatment and final inspection of casting quality from various points of view are parts of the research. The list of the most common defects in case of using five selected products is the result of the experiment. The objective of the research was to identify causes of defects in the process of cylinder head casting as well as to identify root causes of discrepancy using the quality management tool.

Adhesive bonding technology is among the basic methods of joining. Treatment of bonded surface is seen as an essential technology for improving the strength of the bond. Improper treatment of bonded surface reduces the bonding strength and at the same time may increase the cost of manufacturing the bond. The aim of the research was to evaluate the treatment of AlCu4Mg surface bonded by using single-component epoxy, which is commonly used in the transportation industry. This article describes the effect of bonded surface treatment (mechanical treatment of Al2O3 blasting, chemical treatment by degreasing, without modification). Evaluation of individual bonded surface modification was performed according to ČSN EN 1465. From the results of the experiments it can be concluded that all tested adhesives did not confirm the hypothesis H0 (p ˂ 0.05). It follows that there is a difference in the treatment of the bonded surface. The influence of the treatment of bonded surface on adhesive bond strength and elongation of adhesive bond was statistically proved at significance level of 0.05.

Self-hardening aluminium alloy AlZn10Si8Mg represents an innovative class of light aluminium alloys and they present high mechanical properties, which make them suitable for many applications in different industrial fields, especially in transport industry. The most important and relevant feature of the self-hardening alloys is related to their good performance, without the need of any heat treatment: they are subjected to a natural ageing phenomenon at room temperature after a storage period of about 7-10 days. The possibility to avoid the heat treatment represents an important benefit, contributing to considerably reduce both the production cost of some components and the amount of energy. Furthermore, without heat treatment the risk of component's deformation during the production is eliminated.
The Charpy impact energy of experimental cast alloy was measured at -196°C, -20°C, 20°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C and 400°C in terms of the total absorbed energy. Effect of temperature to microstructural changes and fracture surface on the impact toughness was investigated. A combination different analytical techniques (light microscopy upon black-white etching, scanning electron microscopy (SEM) upon deep etching) were therefore been used for the identification of the various phases.