Fulltext search in archive

In recent years, significant success has been achieved in surface treatment research, particularly in the field of physics, which deals with the surface properties of metals and their alloys, as well as new methods of coating preparation and thin films. These coatings and layers can modify material properties, i.e. increase oxidation and corrosion resistance, and improve frictional surface characteristics and other physical properties (e.g. electronics and optics). This article focuses on the mechanical properties of the coating, in particular on the hardness of composite PTFE coatings with WC micro and nano particles. In the experiment, samples of different concentrations of WC particles in the PTFE matrix were prepared, followed by a Vickers and Nanoindentation test. The difficulty in measuring the hardness of these layers is their small thickness. It is therefore difficult to measure the hardness by conventional methods, for example, Brinell or Vickers. The applicability of the individual methods (according to Vickers, nanoindentation test) we have experimentally verified and drawn the relevant conclusions and recommendations. Part of the contribution is also SEM documentation of created coatings. An important parameter is the coating technology itself when making these composite coatings. The technology can influence the distribution of particles in the matrix, which results in the homogeneity of the coating and the associated mechanical properties or tribological properties.

This article intends to present the first results of a long-term research project, which will result in developing a validated model of a pedestrian for the simulation of crash tests involving tram fronts and, where applicable, the fronts of other urban rail vehicles. The current phase of research includes results of the pilot experiment with a crash-test dummy, and these results supplement the results from simulations, thus demonstrating how important it is to pay special attention to the individual stages of a collision event and how important the localisation of and moulding by an individual tram's front panels are for the nature of the monitored stages. In the first stage, inertia of individual body segments plays a significant role, with the primary contact taking place between the tram's bumper and dummy's thigh. The dummy subsequently " takes the shape" of the tram's front with progressive bumps to shoulders and head following. At that moment, the tram brakes, and the dummy begins to disentangle from the front panel. The friction force between the dummy's soles and the surface of the rail track is very significant for the nature of this second stage of the collision event .The dummy then hits the ground. It is an accelerated fall, and under the given conditions, it is the stage that has the most devastating impact on the dummy. The simulation made shows the way to modify this dangerous stage to be less harmful to a pedestrian involved in a tram collision.

This article deals with state-of-art in the field of handling machines intended for disabled people, which serve for disabled entry of such people and for people with delimited locomotion. It contains calculation of forces, which act in the mechanical system of an electric device during its operation in real conditions, changes of reactions depending on the load and the climbing angle as this solved handling machine will designed for negotiation of staircases. The objective is the functional calculation of a driving mechanism of a stair chair marked SA Alfa, i. e. the calculation of loading forces and their action on the driving mechanism. It will serve in the next step as an input for the calculation of a required power under conditions of occurance of maximal resistance forces, which will be determining factor for dimensioning of driving components of this device.

Laboratory fatigue testing is an important part of the fatigue design of machine components that are supposed to work under cyclic loading. These tests are used to confirm whether the tested component matches the required fatigue life and they also serve as a verification of the numerical calculations. This paper describes a fatigue life testing of a welded steel construction. The testing was carried out in the Regional Technological Institute (RTI) using an electro-hydraulic loading system, which allows realization of the tests simulating a real service. An integral part of the fatigue tests is a pre-scheduled inspection of the crack initiation and propagation. The tested construction was checked using non-destructive magnetic particle testing before the fatigue test and also during and after the performed test. Some cracks were observed, especially in the weld area. The biggest crack had the length of approximately 40 cm. This crack was cut out and underwent detailed metallographic and fractographic analysis to estimate the effect of material purity and quality of the weld on the fracture.

The development of economy can not be separated from sufficient energy supply. With the progress of technology, the distribution network gradually expands the capacity and transportation, but also brings security risks. The distribution automation system can effectively manage the power grid faults. This paper briefly introduced the calculation model of the economic cost and the reliability rate of the distribution automation, and then the assembly scheme of the distribution terminal was optimized by using the improved binary particle swarm optimization (PSO) algorithm. Next, the simulation analysis of the distribution terminal distribution on a 10KV main feeder line in Xuanwu District of Nanjing city was carried out in MATLAB software. The results showed that the improved binary PSO algorithm could optimize the assembly scheme of remote metering and remote signalling and the assembly scheme of remote metering, remote signalling and remote control rapidly; the hybrid assembly scheme needed a little more time; the power supply reliability rate of the optimized three terminal assembly schemes was over 99%; the hybrid assembly scheme had higher power supply reliability rate and the lowest economic cost.

The current mechanical engineering is inconceivable without the implementation of CAx systems in design and manufacturing process of individual components. The automotive industry is a clear evidence of how CAx systems affect the innovation cycle of its product - a car. The innovation cycle in automotive was reduced from 8-12 years to the current 4-6 years. Even in this short interval automakers make some small design modifications called a facelift. Development in the automotive industry, therefore, is closely related to news and functionality CAx systems. CAD systems at the turn of the millennium are characterized as parametric graphic systems with a history tree of product creation. Parametric design implemented into CAD systems makes the model variable and open to rapid change management. The history tree in turn enables rapid editing and modification of forming or editing functions.

The Cold-Box Amine method was developed in 1965 by Ashland. For more than 35 years, this method has been applied worldwide and has become the most important method of cold curing. The veining is characteristic defect of cast iron alloys, which accompanies the use of Cold Box-amine cores, the solution to this defect is the content of this paper. There are many factors that affect the surface of the casting and thus the formation of veining. In recent years, products have appeared on the market - additives to prevent veining. Castings using these products should have a smooth surface, no protrusions and other foundry defects. These products have their irreplaceable place on the foundry market, as it is often necessary to eliminate the castings that cannot be cleaned and therefore the veining cannot be removed on these castings. They are predominantly castings for the automotive industry, castings for the railway industry and, in the case of low-quality casting in these sectors, we can talk about gambling with human life. Therefore, it is necessary to pay attention to the occurrence of leaks on castings and to eliminate them with the use of the above-mentioned additives, but we must not forget about many other factors that support the creation of this foundry defect. The paper is devoted to the factors influencing the casting surface and, last but not least, to the used additives in foundries.

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 article deals with the optimization and modernization of assembly systems by creating models in the simulation software. The creation of digital models is a current trend in enterprise digitization called Industry 4.0. The Tecnomatix Plant Simulation environment allows you to create a virtual model of a real assembly line with the input of its basic production parameters. To perform the analysis, 8 real assembly lines were used, with an average of 15 workplaces, which were integrated into one universal line by means of simulation. The aim was to analyse the effectiveness of the proposed modernization universal assembly line using the generated statistical data.

Additive manufacturing (AM) allows printing from different materials: from wax to plastic and even metal. This paper concentrates on Direct Metal Laser Sintering (DMLS), which allows printing to create complex parts from different kinds of metal. Inconel 718 was chosen for this research. This material is used especially in the aerospace industry and in other demanding applications due to its characteristic properties, which include high strength at high temperatures, corrosion resistance, low thermal conductivity, high hardness, work hardening and low thermal conductivity. Components used in aeroplanes must be very reliable, lightweight and their mechanical stresses must be accurately described, because the components are designed with respect to these criteria. For this reason, each material must be perfectly described in terms of mechanical properties and their minimum limits must be identified. Tensile testing is the best way to find the basic set of mechanical properties of a material. The samples were printed in two different orientations on a building platform and the differences in mechanical properties were investigated. The effect of machining on mechanical properties was also investigated.

In the current world, the business faces different challenges, as it was in the 1950th. Today, most of the manufacturing companies have a very strict approach to increasing market needs of Safety, Quality, Delivery and Cost key performance indicators (KPI). To stay competitive, it is needed, that a holistic approach on the improvement of strategic KPIs is needed in order to be successful. The target of this paper is to show the application of the Value stream mapping methodology, used in a case study for a finish good assembly line in an Electronic Manufacturing Facility. The study is showing the improvement of quality, delivery and productivity KPIs over a time period of 3 consecutive years. The result is the increase of production output from 500 pcs/shift to 1050 pcs/shift, decreasing the number of quality returns from 3 to 0 and improving the delivery performance from 95 to 100% against customer requested date.

. The paper presents the results of laboratory tests intent on the study of storage place, placing manner and storage time on mechanical properties of briquettes made from poplar chips. For the briquettes production the briquetting press of the firm Briklis was used, type BrikStar 30-12, of 50 mm pressure chamber diameter. All briquettes were made at the briquetting press all parameters constant adjustment. The briquettes properties were evaluated by their density and rupture force determination. Moreover the mechanical durability, the gross calorific value, the total moisture and the ash content were determined. By the carried out tests it was univocally proved that the mode of storage influences briquettes durability at their long-term storage most of all Briquettes, deposited in the well closed plastic bag in closed heated room, changed their properties during four years only minimally. Briquettes, deposited in the same place but in plastic net bag, changed their properties much more. Briquettes, deposited in the well closed plastic bag in closed unheated room, changed their properties during four years only minimally. Briquettes, deposited in plastic net bag, changed their properties to such a degree that they were practically unusable. On the basis of the carried out tests it is possible to state that for the parameter of briquettes quality evaluation the rupture force can be recommended.

With increasing complexity of machinery and products manufacturing the strict requirements for quality and, reliability of the measurement equipment and systems plays significant role in production system and quality assurance in terms of customer satisfaction. In nowadays automotive industry in connection to ISO/TS 16949:2009 there has been observed a strong confrontation with request for proof of suitability for use of selected gauges for a specific operations. An appropriate methodology allowing to determine a gauge the most suitable for a given operation is Gauge Reproducibility and Repeatability study (GRR or R&R). The GRR takes into a consideration the variability of produced parts, operator`s approach, and whole measurement system. The article deals with a description and the adequate methodology, and the experimental implementation of GRR in manufacturing quality process assurance in order to set up and continuously improve the quality level in automotive parts production.

The paper informs readers about the latest trends in ecological production of cores for the most demanding castings made of aluminum alloys on example of cylinder heads for combustion engines of the passenger cars. Although the cores bonded with silicates are known since the 60th years of the 20th century, only in recent years the technical progress has undergone such level that the leading producers of cylinder heads are able to deploy the system in serial production. Nemak started solving inorganic systems 12 years ago and today it delivers selected products to its customers and during their production there are cores being used which are joined by ecologic systems. The contribution analyses limiting technical aspects at application of inorganic systems. They replace systems of cold-box and hot/warm-box and it presents in details the benefits of ecological solutions which may be found in final product features. At the same time, it also points at difficulties which are still necessary to be solved.

In the aerospace industry, the nickel-based superalloys are often used due to their ability to withstand extreme conditions. They find their use particularly as turbine blades in jet engines. An important example of this type of superalloy is INCONEL. This construction material must meet a wide range of complex requirements with regard to its properties and technological and operational characteristics that are required by the heavy duty in extreme conditions.
The INCONEL Superalloys represent multicomponent and multiphase materials with their complex alloying base and structure with distinct dendritic segregations. Their long life and reliability in operation are directly related to the microstructure, or to its stability in a long-term operational application, respectively.
The presented work deals with the evaluation of microstructural parameters at two variants of cast superalloy INCONEL 713LC, applying the light microscopy and electron microscopy, including the fractographic analysis.

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.

Tool steels are traditional materials whose heat treatment routes are well-established. Despite that fact, unconventional treatment methods can be used, for instance for refining chromium carbides and general strengthening of the structure. One of the methods that considerably alter microstructure is semi-solid processing. By means of passing through the semi-solid state, the X210Cr12 steel (ČSN 19436) developed a microstructure of polyhedral austenite grains embedded in a carbide network. Forming of this material at an appropriate temperature led to recrystallization of the austenitic microstructure and to uniform distribution of carbides with a size of approximately 2 μm. By varying the rate of subsequent cooling, microstructures ranging from austenite to martensite could be obtained.

This study was focused on the analysis of creep behaviour of the polymer composite with continuous phase in the form of two-part epoxies and discontinuous phase (reinforcing particles) in the form of fibres of false banana (Ensete ventricosum). The aim of the experiment was to describe the short term flexural creep behaviour, flexural strength and Charpy impact strength of polymer composite reinforced by fibres of false banana. The fibres of Ensete ventricosum, originally from Ethiopian region Hawassa, were used for this experiment. Reinforcing fibres were prepared in size of length 1-2 mm with randomly fibres arrangement in matrix. The amount of reinforcing particles in the composite material was 0.5; 2 and 30 wt.%. Moulds for casting specimens were produced from the material Lukapren N regarding to the prepared models whose shape corresponds to the technical standard CSN EN ISO 3167. Composite which was used to prepare specimens according to CSN EN ISO 3167 (Plastics - Multipurpose test specimens, English Standard Institution) was created by mixing of fixed rate of matrix and filler.

Metallic biomaterials are currently produced mainly by conventional metallurgical processes, i.e. the melting and casting used e.g. in production of cobalt alloy implants, or forming processes as cold or hot working (rolling or forging of stainless steel for surgical applications). Such processes including melting are used also in production of "smart" biomaterials - NiTi shape memory alloys. The mechanical properties are strongly dependent on the grain size. Therefore, the techniques to obtain finer structure are very desirable to enhance the mechanical properties of the biomaterials and thus to increase lifetime of the implant. This paper is devoted to the description of the possibilites of powder metallurgy not only for the structure refinement, but also for the ptoduction of clean biomedical alloys as well as the porous bioamterials. The use of powder metallurgy is described for Co-Cr-Mo surgical alloy, Ni-Ti shape memory alloy and Ti-based porous biomaterial. In addtion to known methods, new powder metallurgy processes and materials developed by the authors are presented.

This study was focused on an effect of the plasma treatment on a mechanical behaviour of false banana's fibres (Ensete Ventricosum). The aim of the experiment was to describe the tensile strength of Ensete Ventricosum fibres which were modified by the plasma surface treatment. The fibres of Ensete Ventricosum, originally from Ethiopian region Hawassa, were used for this experiment. The fibres were prepared in the length of 100 mm. The samples were modified by the plasma treatment. Plasma was generated from a plasma generator (Plasma Reactor KPR 200 mm RM 54) while supplying the reaction gas (oxygen) and maintaining the reactor's pressure at 0.1 Torr with the use of a vacuum pump. To determine the properties that depend on the discharge power and treatment time, the plasma treatment was conducted in the power range 200-350 W for 10-50 s. The maximum tensile force was measured immediately after the plasma treatment to determine the ultimate strength. The ultimate strength and the deformation were determined by destructive tests using the tensile testing equipment (Labortech, MPTest 5.050, sensing unit AST type KAF 50 N, Czech Republic) with a rate of deformation 5 mm min-1. Fracture surfaces of fibres were studied using a scanning electron microscope (Tescan Mira 3, Czech Republic). The samples were covered with a thin layer of gold using a sputter coater (Quorum Q150R ES, United Kingdom) before SEM observation.

The aim of this article is proposition of new methodology of experimental analysis of long-term monitoring of sandwich composite structures. The sandwich composite structures are, due to its properties like stiffness, high impact strength, corrosion resistance, low thermal conductivity and low acoustic conductivity and, commonly used in civil engineering in recent years. This type of structure is composed of two main parts (face sheet and core) having different material and mechanical properties. Sudden change of these properties causes interlaminar stress in structure. A good knowledge about behaviour of sandwich composite structure is important for efficient manufacture techniques, long-term prediction of structure behaviour and for economics. The experimental part has been focused on obtaining the experimental results of deformation between layers of sandwich composite structure during long-term monitoring. The long-gauge optical fibres SOFO® SMARTape Compact have been used for long-term monitoring of sandwich composite structures. Long-gauge optical fibres were placed between the foam core and an outer layer of the composite structure during manufacturing. Test specimens were loaded in three-point bending test.

The article describes experimental and numerical investigation of airflow inside the floor convector. Analysis was divided to two parts. First part was airflow visualization. This part was realized in two areas. At first the visualization was realized in the area between a fan outlet and a heat exchanger inlet using a continual laser and a video camera. Then the visualization was realized in the region above the heat exchanger outlet with a Particle image velocimetry. At last the flow behavior in domain between the fan outlet and the floor convector outlet was analyzed with a numerical simulation. Commercial software ANSYS Fluent in version 15.0 was used. Results from the numerical simulation and the experiments were compared and the flow behavior was examined.

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.

Manufactures of automotive engines and complete vehicles strive for the lowest possible fuel consumption, which also leads to the use of motor oils with lower viscosity. Lower viscosity of oil reduces internal friction and provides faster distribution of oil into lubrication points, but simultaneously reduces the size of transmitted power. The design of automotive engines use plain bearings, which are based on aluminium, brass. Further are used steels with coating based on aluminium and bronze. The paper describes the impact of viscosity of motor oil to wear of basic materials, which are used in production of plain bearing. Reichert tester M2 for evaluation the lubricity from Petrotest Company was used in order to assess ability of motor oils to create proper lubricating film. Reichert tester M2 belongs to a group of equipments simulating real frictional contact. Stabinger viscometer was also used for the precise determination of viscosity of various types of motor oils.

The paper deals with a design and construction of an implant prototype of a knee-joint femoral component with a complex shape mathematic description especially of functional (articulating) surfaces. The core of a technical solution labours under the thought of casing of femur distal part with a shell of certain thickness whereas a special area is used as a referential area defining an inner and outer shape of the shell. The area is marked, cropped and smoothed. It is the created area of the lower end of the patient femur respecting the overall curvature of the knee joint.
Within designing of the implant prototype of the femoral component of the knee-joint modern methods of getting CT data, their processing by CAD software called CATIA and subsequent post processing are applied.
The prototype implant of the femoral component of the knee joint is designed from processed CT data of the patient affected knee-joint (the femur distal part, a tibia proximal part). The 3D model of the implant prototype of the femoral component is created on the basis of data editing in CATIA software. The final 3D model is then located to the composition (a bone, the implant prototype) and using anchoring ribs it is fixed on the femur distal part.

This article provides perspective into creation of virtual 3D models of manufacturing devices and optimization of existing machine tools by using an alternative scanning device and freeware software applications (open source elements). This alternative offers scans of components surfaces that are from the viewpoint of precision and quality comparable with much more expensive devices. Various parts of the paper describe the process of creation of the environment with the use of Kinect scanner device and various software tools. At the end an additional options are provided for using with sensing device.