Fulltext search in archive

MicroScan 600-1 is a digital Barkhausen noise analyzer. It is designed for fast nondestructive surface quality control and subsurface layers of machine parts from ferromagnetic materials and for evaluating of defects which are caused by changes of residual stresses. By the instrument based on an analysis of the Barkhausen noise is determined the value of magnetoelastic parameter. Experiments which evaluated the influence of different types of process fluids to the machining process and technological properties of the machined parts from constructional steel 16MnCr (ČSN 14 220) were carried out in the laboratory of the Department of Machining and Assembly at TU in Liberec. Turned, milled and grinded test samples by using five different types of process fluids were evaluated using the analyzer. For The comparison was machining carried out also without inlet process fluid, i.e. "dry" and with the process fluid - water. Measurements of magnetoelastic parameter were performed repeatedly and measured values were statistically processed. The paper presents the resulting values of this parameter showing the influence of process fluids on the properties of the surface layer of the machined parts.

This article describes the determination of geometric, mass and stiffness parameters of the individual part of plateau wagon. After measurements were taken the position change of the chassis of the vehicle body and wheel when driving the vehicle over obstacles was observed. The obstacles were formed by wedges. Experimental detection of parameter has been used in the analytical investigation of kinematically excited system of three-body space flexibly stored and linked.

The main object of this research was the influence of plastic deformation on magnesium alloy AZ61 with 0.5 wt. % of Ca. Tested specimens were loaded by three - point bending test and by pressure deformation. Hardeing and softening were measured also. Specimens were studied in two structural states: as - cast state and in state after heat treatment. During three - point bending test specimens were plastically deformed by dislocation slip and twinning. The compression loading of experimental specimens after heat treatment led to slip and twinning plastic deformation. Cracks were created in the surrounding area of the indentation and there was also cracking of intermetallic phases present in the microstructure. Changes in the intensity and distribution of plastic deformation were caused by deformation strengthening and shifting of grain boundaries. Grain reorientation and strengthening of neighbouring grains occurred during the growth of plastic deformation and the hardness was increased. After reaching annealing temperature of 300 °C, decrease of the material hardness was observed.

The Ni-Ti alloy (Nitinol, approx. 50 at. % Ni) is a biomaterial showing the shape memory and superelasticity effects. These characteristics make this material of interest for biomedical applications, especially for manufacture of stents, i.e., tubular implants for restoring damaged blood vessels, oesophageus etc. The corrosion resistance in the human body environment is a very important factor determining the life time of implants. An insufficient corrosion resistence may lead to fractures of implants, formation of dangerous fragments and to serious health problems for patients. The corrosion behavior is influenced mainly by the surface structure and chemistry of a material. But the surface state is strongly modified by chemical and heat treatment processes used in the implant manufacture. Therefore, in this study the relationships between chemical treatment and heat treatment regimes, surface state of Nitinol and its corrosion resistance in simulated physiological solution are demonstrated. It is shown that, unlike chemical pre-treatment, heat treatment used in the manufacture of stents generally negatively influences the corrosion resistance. The findings are discussed in relation to the surface state and chemistry of the material.

Introduction into problems - This article is focused on the area of virtual reality, in the concrete to the creation of application and its using. The applications are usually used with the expensive display devices and expensive motion tracking devices. For the application of virtual reality technology is currently available the several motion tracking devices, which have different prices. This contribution describes the using of application with the Kinect device, which is affordably priced. Kinect is a device that needn't for control any physical controller, because uses only the user's movements, which are transferred to the application. By using of virtual reality technology is very simply to compare the different versions of a solution and simply eliminate the found mistakes. And if the whole product design is proposed, controlled and simulated by using VR, in the production process should be no bigger problems.

Satisfactory tensile properties, even at elevated temperatures, are very important for thermally stressed parts in car structures (e.g. cylinder heads and engine blocks). This condition is satisfied also by magnesium-based alloys containing strontium and rare earth metals, which are very expensive, though. The presented paper deals with study of Mg-Sr-type magnesium alloy. To be specific, this is AJ62 alloy which belongs among developmentally new magnesium-based alloys. This alloy combines very good castability and heat resistance, moreover, this is cost-effectively available material. This paper is focused on this alloy structure refinement. Analysis of the acquired structure after an inoculant addition and its effect upon thermomechanical properties was performed. In term of safety of the use of this alloy for thermally stressed automotive parts, thermal dilatation tests of prepared specimens were carried out as well.

With the development of the automotive and aerospace industry and also biomedicine, exotic alloys are more and more used from all machined materials, especially titanium and nickel alloys, but which are hard-machined materials. Therefore it is necessary to know their behavior when machining, thoroughly. Processes occurring in the cutting zone when machining, are so complicated and dynamic, that their definition is carried out by certain specified models. Because the models have errors and deviations, it is needed to improve their observation so, that these deviations will manifest minimally or not. Based on the scientific research of the cutting zone, the multifunction measuring system was designed, which allows simultaneous measuring of components force of cutting, heat distribution and deformation processes in cutting zone during machining without its interruption.

The paper deals with modelling and optimization of a working machine seat suspension system parameters. Experimental work in the past shown that it is possible to replace even more complicated, for example parallelogram or scissor mechanisms, with simpler dynamic models of 1 or 1.5 degree of freedom (Zener model). The optimization of stiffness and damping parameters is realized using multiobjective function. The first component of the function expresses the acceleration of the seat squab, this points on the comfort of the seat, the second one expresses the relative displacement of the seat squab in regard to the working machine cabin, points on the better operator's sightedness and safe handling of the machine. This optimization process allows to propose so called "soft", "medium", or "hard" seat suspensions according to the value of the weighting coefficient. The paper also points on the possibility of improving the dynamic characteritics of the seat with the use of a vibration absorber. The expediency of its application is especially in working machines without significant changes in the seat excitation frequency spectrum.

The paper deals with the lead-free soldering and influence of germanium amount in lead-free secondary solder Sn99. Lead-free soldering is an emerging area in the metallurgy of non-ferrous metals with a non-harmful effect on the environment. This method of soldering is very important for connecting materials in precision electrical engineering. In the experimental part of the paper are evaluated properties of lead-free solder Sn99 with graduated amount of Ge, compared with lead-free solder with the addition of nickel and silver. The goal was to provide knowledge on the impact of germanium on microstructure change, solderability and formation of oxides on the surface. From the results it can be concluded that germanium in lead-free solders reduces the formation of oxides on the surface by the addition of 0.01 wt. % Ge to the batch. With the amount of 0.01 wt. % also the grain is refined in the microstructure, resulting in improved castability. In terms of solderability experiments confirmed that germanium improves the flowability of solder on the PCB substrate.

Al-Si Alloys are a leading casting alloys based on aluminum. Machining of aluminum alloys is currently frequently used and it is an important area of production. The paper deals with an experiment, that was realized at the Faculty of Production Technology and Management, University of Jan Evangelista Purkyne in Ústí nad Labem, where was machined alloy AlSi7Mg0.3. Samples were made for machining because of the master alloys of AlSi7Mg0.3, where part of the castings was left in its original condition and part of the castings was modified by strontium. This paper describes the evaluation of surface roughness obtained after machining of these castings in terms of how the modification by strontium can affect this.

Precision machining and especially hard machining is a topic of high interest at present. Surface integrity requirements increase. Precision machining (mostly turning and milling) may substitute some abrasive operations. There are some advantages of precision machining over the abrasive machining. Abrasive machining has traditionally performed the finishing process of hardened steel. But, the availability of hard and super hard cutting tools enable the machine tools to reach surface quality of hard machining like to those obtained in grinding processes. But, precision machining is possible to apply also in machining common materials, not only hard materials. A surface is not only a geometric entity but also a layer with its own structure and properties. These properties are affected by many factors, e. g. by cutting temperatures, friction, deformations in the primary deformation zone and the surface layer of the transient (machined) surface, by cutting tool geometry, work hardening, cutting environment, etc.

This research investigates the influence of repeated use of the Al-Cu-based alloy. In our case we used the alloy RR.350. Specimens for the tensile test were cast into a metallic mould, to which a protective coating was applied. Altogether 15 specimens were prepared from each melt in order to obtain more accurate results. During casting the temperature of metal and mould was controlled from the viewpoint of ensuring constant conditions of the experiment. Test bars were prepared from the cast specimens for measurement of tensile strength at normal (20°C) and elevated temperatures (up to 350°C). Furthermore parts were taken from the cast specimens for measurement of hardness (HB) and for metallographic analysis. Thermo-mechanical properties of the investigated alloy were determined at the working site of the authors - Department of Metallurgy and Foundry at the Faculty of Metallurgy and Materials Engineering, VŠB - Technical University of Ostrava. This experiment has unequivocally confirmed the negative effect of repeated use of the investigated alloy on its thermo-mechanical and structural properties.

Machinability of materials is evaluated by different criteria. The basic evaluative criteria are based on tool wear. However, there are other criteria, for instance chip formation, cutting temperature, forces of cutting, etc. Machinability for different criteria depends on many factors, of which the most important is the chemical composition of the material. It is possible to divide machinability tests into two groups: Long-term tests and short-term tests. Short-term machinability tests are less objective than long-term ones, but they have the advantage of short duration and lower material consumption. This paper is focused on the experimental determination of the effect of chemical composition on the machinability of aluminium alloys. For testing three different short-term tests were used. The results were evaluated by correlation coefficients. All used tests led to the same results.

Each construction of cutting machine tool activates geometric inaccuracies of the workpieces as a result of different stiffness of its joints. The acting of cutting force and the moving of its position leads to the deformation of the elastic joints of cutting machine tool and the elastic deformation of the workpiece appears. The aim is to maintain geometric modifications of the workpiece in required tolerances. The paper tries to identify these inaccuracies for case of a centre lathe.

The microstructure evolution and the tensile strength changes of hypoeutectic AlSi6Cu4 cast alloy modified by AlSb10 (0 - 10 000 ppm) was systematically investigated. The samples were study without and after T6 heat treatment. Several types of etching were used, which includes standard black and white etching (0.5 % HF), colour etching by Weck-Al (for documentation the eutectic cells) and deep etching by HCl (for eutectic Si morphology study). The results show that the addition of Sb into AlSi6Cu4 cast alloy should act as a modifier, so it supposes to change the eutectic Si morphology. However, its effect as a modifier is not as significant as we have expected. Its effect was more inoculation and caused refinement of microstructure what has led to mechanical properties increasing. Refinement of microstructure could obviously improve the size and distribution of eutectic cells. The eutectic cells are refined significantly in a fully modified eutectic microstructure (more than 1 000 ppm Sb). It can be speculated that the stick-fibrous transition of eutectic Si morphology involving in impurity modification may be independent of the frequency and mode of eutectic nucleation.

In production practice, it is important to know the machinability of new constructional materials. This is related to the selection of adequate cutting tools and machining conditions. One of such relatively new materials is Duplex Stainless Steel (DSS). Manufacturing machine parts of hard-to-machine material is very troublesome. It is still more difficult when high quality requirements are to be met. Duplex stainless steel is used in applications for very severe working conditions, e.g. for modern deep-well pump bodies for mining industry or the shafts of electric mixer motors in food industry. This paper discusses the effect of cutting conditions on the machinability of DSS. The advantages and disadvantages of various tool materials with regard to machining of DSS are highlighted. Problems associated with the machining of DSS as well as tool wear and the mechanisms responsible for tool failure are identified and discussed. However, the machinability of DSS is an area that needs to be studied more deeply to cut the production cost.

The paper dealt with the influence of geometric asymmetry on the vertical vibration of symmetrically or asymmetrically loaded mechanical system. The system is composed of rigid flexibly linked elements. Kinematic excitation was carried out by a unit jump (jump of the springs), excitation of system was symmetric and asymmetric. The system of elements was examined experimentally and numerically. The numerical model was verified by experimental solution. Numerical solutions were carried out by finite element method (FEM) applied to model that respected the design and conditions of the laboratory model for experimental investigations. The aim of the work was to create a numerical model based on the finite element method and to verify the results of the model. The obtained results can be applied to flexible storage machines.

Milling is one of the most universal operations in machining processes because it can remove the redundant part of material efficiently, and moreover, it can produce almost all kinds of contour surfaces with a high quality finish. Surface roughness plays an important role in determining the product quality since it strongly influences the performance of mechanical parts as well as production cost. Many types of cutting materials are used as tool materials in today's metalworking industry. Selecting the proper cutting tool material for a specific machining application can provide substantial advantages including increased productivity, improved quality and ultimately reduced costs. This article is aimed at determining the influence of different tool materials on surface roughness of AlMgSi aluminium alloy after side milling with using of the analysis of variance (ANOVA).

Worldwide increasing energy demand is today permanently covered by a majority of non-renewable energy sources, namely by coal, crude oil and natural gas. This causes the rapid decline of their reserves and the time gets near when they will be run out. Therefore in last years the exploitation of renewable energy sources is permanently preferred. One of alternative fuel forms is the fuel on the basis of paper waste. In this paper the results of tests are published, which were carried out using five sorts of paper waste, pressed in form of briquettes. During the tests following briquettes parameters were watched: moisture content, ash amount, length and diameter, weight, density, rupture force and mechanical durability. The results are presented in form of tables and graphs. It was proved that briquettes made from recovered paper and board are compared with briquettes from wood waste of high density, high mechanical durability and for their rupture the relatively high force is necessary. But at the same time they have high ash amount and low combustion heat.

Introduction into problems - Rapid Prototyping (RP) presents the automatic production of physical parts using by additive manufacturing technology. The start techniques for Rapid Prototyping became available in the late 1980s and were used to produce models and prototype parts. Today they are used for a much wider range of applications and are even used to manufacture production-quality parts in relatively small numbers. Rapid Prototyping is widely used in the automotive, aerospace, medical, and consumer products industries. In this paper are presented selected experimental test of materials used in different Rapid Prototyping Technologies. Main part of the paper is oriented on presentation of materials test of Fused Deposition Technology realized by authors on Department of Manufacturing Technology of Faculty of Manufacturing Technology in Presov (Slovakia).

First, in this paper, a brief review of theoretical aspects of weld simulation and residual stress modelling using the finite element method (FEM) is presented. Thermo-elastic-plastic formulations using a von Mises yield criterion with nonlinear isotropic hardening has been employed. Residual stresses obtained from the analysis have been shown. The commercial FEM code ANSYS and a user created code were used for uncoupled thermal-mechanical analysis. Second, the aim of this paper is to compare ANSYS capabilities extended by authors to model weld phenomena versus well known SYSWELD code. Element birth and death FEM technique was used to simulate the weld metal added to base metal due the welding process and to reset plastic history for molten portion of material. Goldak's double ellipsoid heat source was used to model welding heat source. The Leblond's model was used to simulate ferritic and bainitic phase transformations and Koistinen - Marburger model was used to simulate martensitic transformation.

In each industrial entrepreneur organization around the globe a three dimensional objective well known under the abbreviation QCD (Quality, Costs, and Delivery) is examined, pursued, and evaluated on daily basis. The nowadays crucial philosophy pertaining to process improvement in terms of quality assurance and significant cost reduction is that: "The quality must be manufactured and not controlled up". In order to be successful on the market place it is necessary to orchestrate, implement and carry out an advanced production quality assurance system with appropriate tools of course accompanying with previously precisely organized prototype and pre-serial stages of production. The article deals with a proposal of adequate methodology and the experimental implementation of quality matrix into manufacturing process assurance in order to improve a quality level and the whole QCD.

The paper deals with modelling and optimization of dynamic characteristics of a semiactive suspension of the working machine seat with a vibration absorber. The suspension is composed of a spring paralelly ordered with a semiactive damper controled by the sky-hook control algorithm. For the improvement of the dynamic characteritics of the semiactive suspension there is also analysed the effect of a vibration absorber. The dynamic characteritics of the suspensions are optimized by the multiobjective optimization, where besides the component respecting the effect of the effective accleration of the seat also the effect of the effective relative displacement between the seat and fhe floor of the working machine cabin is considered.

Presence of iron is a common problem in Al-Si based alloys. Due to iron influence, mechanical and foundry properties of alloys are decreasing, so it is necessary to balance the influence in a certain way. One of possible solutions is addition of alloying elements, also called correctors of iron, into the melt. In this paper, the influence of vanadium on decreasing negative effect of iron in secondary alloy AlSi6Cu4 is assessed. In experimental part, properties of alloy with various addition of vanadium are evaluated. Microstructural and EDX analysis of selected structural parts are also a part of the experimental measurements. Based on statements from realised measurements can be stated that vanadium is an element, which can be used to correct negative effect of iron in secondary alloy AlSi6Cu4.

This paper describes the methods that are applicable for the preparation of aluminium-based quasicrystals. Application of rapid solidification of the melt, mechanical alloying and reactive sintering of metallic powders are presented. Based on the conducted experiments, mechanical alloying seems to be the most promising technology, since it enables to yield nearly pure quasicrystalline powder in Al-Fe-Cu alloy system.

Article deals with design of appropriate artificial neural network for prediction of surface roughness as one of the very important indicators of machined surface quality. The drilling of nickel based super alloy UDIMET 720, was applied as test material. This type of material is most frequently used for jet engines components such as discs etc. Experimental data collected from tests were used as input parameters into neural network to identify the sensitivity among cutting conditions, tool wear and monitoring parameters and surface roughness. Selected parameters were used to design a suitable algorithm for control and monitoring of the drilling process with respect on surface roughness. The accuracy of predicted and measured values are compared and discussed.

With increasing tendency of die castings production, also the possibility to produce castings with maximum usage of molten metal grows. Residual of non-used molten metal, e.g. sprues, feeders, splashes and saw-dusts are used in next production as returning material. With returning material a lot of non-suitable elements is brought into the melting process, but with decreasing of input costs it creates inseparable part of production process. Usage of returning material in melt production has negative influence on final quality of produced castings, because of bringing of inheritable properties into produced melt. Important factor in melt production with the amount of returning material is to know to set its optimal amount and the way of melt treatment to achieve the same results in casting quality in comparison to the casting production from clean materials.

This article describes the principle of Green Machining technologies and experimental tracking of moisture of ceramic granulate during the drying process. Green machining involves the machining of metal or ceramic bodies in the "green" state prior to sintering. Typically these bodies are comprised of ceramic or metal powder held together by an organic binder. In this state they are far easier to machine than monolithic blocks of the corresponding metal and ceramic. One of the materials that can be used in the green machining is silicon carbide. This material is produced in the process of spraying the emulsion in drying kiln. This process is very important considering the quality of ceramic powder with respect to its further use. One of the most important parameters to be monitored during the spraying is the moisture of the ceramic powder (granulate). [8][2]

Metal foams belong thanks to their unique properties into the group of new and perspective materials. The paper deals with foundry procedures used for production of cast metal foams based on non-ferrous metals alloys. Individual procedures of production in lab and pilot conditions are described, which result in casting with certain structural regularity. Attention is paid also to the obtained microstructure of these cast materials and to evaluation of their properties. The experimental part summarises the existing research works in this area, including future possibilities of their use. Cast metal foams are not yet produced in Czech Republic on industrial scale.

Nanocrystalline metals are advanced materials with structural constituents smaller than 100 nm. With respect to structure, they are characterized by high strength and hardness, gas absorption capability, high specific surface area, catalytic activity or magnetic properties. These properties predispose them for using in wide spectrum of possible applications, namely advanced structural and functional applications, biomedicine, catalysis or electronics. Many methods have been developed for producing nanocrystalline metals or nanocrystalline metallic powders including precipitation from supersaturated liquids, severe plastic deformation, cryo-melting, or inert gas condensation. In this work, another promising method - selective dissolving of aluminium alloy was successfully appliedfor preparation of nanocrystalline copper powder and this powder was consequently used for producing of bulk nanocrystalline material with enhanced hardness and strength.