Fulltext search in archive

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.

In the previous paper [12], a design of location and construction of a rotating turning tool has been documented. Sporadically, this tool has appeared in literature [1], [2], [3], [4] in different applications. So far its operational characteristics, mainly its considerable influence on machined surface quality, exceptional durability and possibility to be used to turn hard machinable materials have not been appreciated. Some of its priorities are verified in the paper.

The paper presents the results of the evaluation experiments of the new lance for powder injection process. The pneumatic powder injection process itself has been well known since many years and it can be operated both with submerged and non-submerged lance. The new invented by authors injection lance is dedicated for processes without its submersion especially when the powders are injected into liquid metal bath inside the ladles or induction crucible furnaces. In these cases it is important to not introduce the carrier gas into metal volume to make the temperature decrease as low as possible. However, when the lance is not submerged the problem with particles jet introduction into liquid metal with proper distribution appears. The new lance of special design with slots and flange at the outlet was checked both in model water experiments and real conditions for ferroalloys injection into liquid cast grey iron. The results proved the efficiency of the powder introduction and low liquid alloy temperature decrease, too.

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.

For technology firms it is crucial to integrate progressive product design methods such as Product Lifecycle Management (PLM) tools in their daily routines to improve the quality of the product development process. However, in practice one problem arises: research and development (R&D) employees show little motivation to implement these tools in their work. This paper aims at determining human factors for successful implementation of PLM by studying the motivation of R&D employees. Based on a literature study, face-to-face interviews with 16 R&D experts were performed. Furthermore, a survey study with 22 participants using online questionnaires was conducted. Based on the results of the data analysis, a list of critical human success factors which help managers to implement PLM tools in R&D departments of technology firms successfully is presented.

This paper is concerned with an experimental and numerical study of the fatigue behaviour of cylindrical 6063-T66 welded specimens subjected to biaxial loading. In-phase torsion-bending fatigue tests under constant amplitude loading were performed in a standard electromechanical machine with a suitable gripping system. The experimental part was focused on the modeling of combined biaxial loading and determining the number of cycles to fracture in the region of low-cycle fatigue. In-phase loading can be treated fairly well using the conventional hypotheses (von Mises or Tresca) on basis of the nominal, structural or local strains or stresses. Based on the experimental results the fatigue design curves are compared to the fatigue data from base metal and weldments.

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.

This paper presents the nonlinear analysis of the reinforced concrete buildings of nuclear power plant under the aircraft attack. The response from the nonlinear analysis was considered taken the deterministic calculation procedures. The dynamic load is defined in time on base of the airplane impact simulations considering the real stiffness, masses, direc-tion and velocity of the flight. The dynamic response is calculated in the system ANSYS using the transient nonlinear analysis solution method. The damage of the concrete wall is evaluated in accordance with the standard NDRC consid-ering the spalling, scabbing and perforation effects. The simple and detailed calculations of the wall damage are compared.

This paper deals with detection of surface burn after grinding operations on bearing rings made of case - hardened steels. The paper reports about Barkhausen noise technique employed for non destructive monitoring of grinding burn and discusses the main aspects affecting the Barkhausen noise emission such as thickness of heat affected zone, micro hardness, stress state, carbides, dislocation density and volume of retained austenite. Results of experiments indicate that the influence of stress state on Barkhausen noise is only minor whereas influence of structure features dominates. On the other hand, it is difficult to unwrap influence microstructure features contribution to the Barkhausen noise. For this reason their influence should be studied on the model surfaces undergoing the different regime of chemical and heat treatment.

Metal-plastic parts with steel inserts prepared by overmolding technique showed several molding defects including sink marks. The depths of sink marks on overmolding metal-plastic parts prepared at two injection overmolding temperatures of 280 and 230 °C and the same packing pressure of 60 MPa were measured by contact profilometer. They reached the depths of 3.02 mm and 1.51 mm at the overmolding temperature of 280 and 230 °C respectively. These values were correlated with sink marks indexes simulated in Moldflow software at the same conditions. Based on the simulated and measured results the optimal process parameters with injection temperature of 200 °C and packing pressure of 25 MPa were proposed. Simulation showed a positive effect of optimized parameters on sink marks minimizations. Sink marks indexes decreased of 20 % and 53 % compared to injection molding temperatures of 230 and 280 °C respectively. Maximal depth of sinks marks decreased to the value of 1.00 mm at optimized injection overmolding process parameters.

This work deals with the problematics of 3D printing. Additive manufacturing (AM) covers a lot of principles of producing products and prototypes, for example, Direct Metal Laser Sintering (DMLS). This principle is based on sintering metal powder in thin layers, layer by layer. This theme is very extensive and a very popular research area. The paper is focused on printing thin walls. The material for printing was Maraging Steel MS1. This material achieves great mechanical properties like as high strength and high hardness. The tensile strength can be up to 2000 MPa after age hardening. The printer used was an EOS M290. The effects of different part position on safety of printing are compared. Also, the effect of support structures on accuracy was investigated. The main part of the paper is focused on an experiment where thin walls are printed and subsequently evaluated. The influences and limitations were investigated. The measurements were carried out on a Blickle Multicheck PC500 microscope.

The field of material surface modification with aim of biomaterials construction involves several approaches based on surface treatments that allow to prepare materials, which support the cell adhesion and proliferation and thus aid and improve the tissue formation. Modified materials have a surface composition and morphology intended to interact with biological systems and cellular functions. Not only surface chemistry has an effect on material biological response, surface structures of different morphology can be constructed to guide a desirable biological outcome. Nano-patterned material surfaces have been tested with aim to determine how surface geometry, physical and chemical properties on a micro- and nano-scale can affect cellular response and influence cell adhesion and proliferation. Surface physico-chemical properties (e.g. chemistry, morphology, wettability, electrical conductivity, optical and mechanical properties) of treated surfaces were determined. The enhancement in cell adhesion and proliferation on modified substrates was studied in vitro. Bactericidal action of noble metal nano-particles (e.g. Au, Ag) on polymers was characterized. The influence of metal nano-particles grafting by using metal nano-particle suspension prepared by "green" methods was determined.

The article is aimed on the analysis of the internal damping changes depending on the amplitude of the magnesium alloys AZ31 and AZ91 in as cast state. In experimental measurements was used only resonance method, which is based on continuous excitation of oscillations of the specimen and the entire apparatus vibrates at a frequency which is near to the resonance. Starting resonance frequency for all measurements was about f = 20470 Hz. These mechanisms have been studied by ultrasonic resonant apparatus. Damping capacity of alloys is closely tied to the presence of defects including solute atoms, second phases and voids. The interaction between moving dislocations and point defects is one of the major internal damping mechanisms of magnesium alloys so the precipitates influence the damping capacity and contribute to damping properties.

In this work, the influence of alloying element in equimolar Ni-Ti alloy was investigated. Selected alloying elements (cobalt, chromium, niobium) were added into Ni-Ti46 wt. % powder mixture. The samples were prepared by self-propagating high-temperature synthesis at temperature of 1100 °C with the use of high heating rate (300 °C/min). The changes in microstructure, phase composition, temperature of reaction between Ni-Ti-X powders, phase transformation temperatures and mechanical properties were studied.

Gears are integral part of mechanisms and machines. The development of new composite materials impulse to increase of specific weight and load-carrying ability of gears. Current trend can be supplied with fiber reinforced materials (FRP) whose specific weight strength could by five times higher than of hardened steel. Those the mechanical properties of FRP wheel can substantially be influenced by technological heredity than metallic one. That is why the influence of technological steps should be taken into account during FRP wheels manufacture. The purpose of current research is to develop integrated technique of FRP wheels manufacture. Consequently in current experimental research the cooperation of load-carrying ability of non metallic and metallic wheels was provided. Different techniques were used for optimization of reinforcement fiber geometry when FRP wheels manufacture. Operating procedure of wheel manufacture contents computer simulation of forming, and properties programming helped to provide quality and load-carrying ability of the wheels.

This work deals with an impact of abrasive particles used in powder injection molding (PIM) on a surface roughness of the tool. For this purpose, the surface of new mold cavity was compared with the same mold cavity after 2 000 injection molding cycles. Processed PIM compounds contained polymeric binder with around 60 vol. % of metal or ceramic particles (0.1 up to 20 μm). Surface analysis was performed on cavity impressions prepared from a special silicone imprinting substance in two directions by a 3D surface scanner. Investigated parameters were surface roughness (Ra) and roughness depth (Rz) which have an influence on flow instabilities of highly filled compounds such as wall slip affecting the final product quality. Obtained results showed a significant wear of the mold cavity which was statistically confirmed by t-test and F-test parametric methods. A greater part of the mold cavity was smoothed during injection of PIM compounds, while the surface roughness increased near the point gate (runner system) probably due to a high injection pressure in this part of the mold.

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.

Iron has a low solubility in aluminium solid solution even at elevated temperatures and forms brittle intermetallic phases with needle-like or platelets-like morphology when it is produced by conventional casting technologies. These phases have a detrimental effect on mechanical properties. Therefore with increasing significance of recycling and also amount of aluminium scrap that needs to be recycled, it is necessary to find a promising ways of processing such waste materials. Powder metalurgy leads to intensive microstructural refinement, increases solid solubility of alloying elements and overall to improvement of mechanical properties. Hence, it belongs to promising alternatives for proccesing aluminium materials with increased amount of iron. Aluminium alloy with 17 wt. % iron was prepared by centrifugal atomization and consolidated by spark plasma sintering followed by hot extrusion. The microstructure and phase composition of compact samples as well as mechanical properties were studied. Fine microstructure has been achieved by centrifugal atomization and consolidation by spark plasma sintering in combination with hot extrusion. Compression strength was 565 MPa with remarkable ductility reaching almost 35 %.

In the paper, results of a research on influence of piston stroke rate on structures of AlSi9Cu3(Fe) (EN AB-46000 group) castings manufactured at constant intensification pressure of 290 bar are presented. Relation between piston speed (0.3-2.3 m/s) and casting structure was evaluated after a series of trial high-pressure castings. The examinations were carried-out on properly prepared samples taken from the castings in places with the largest cross-section area. The effect of pouring rate was evaluated on the grounds of metallographic observations on a light microscope and a scanning electron microscope. It was found that larger grains of the very hard phase solidify at low piston speed between 0.3 and 0.75 m/s. Higher piston speed results in finer casting structure and in refinement of particles of intermetallic Fe-Mn phase, which is beneficial for usable properties of the castings.

Failures of machines are caused by variety of external and internal effects and process that cause ultimately interruption of operation. These factors have resulted in changes of properties of machines parts and these changes are the first causes of technical failures. Wear is one of the major factors that contribute to the creation of failures and with this is connected generation of wear particles. Wear particles come into oil in lubrication system, where they cause contamination and degradation of lubricating properties and consequently it may result in major failure of machines. Among these contaminants are included mainly adhesive, abrasive and fatigue particles wear. The paper describes number and morphology of wear particles generated during modified Reichert test (friction pair - steel and aluminium alloy) analysed by LasetNet Fines device. Experiment also compared capability of lubrication of four different engine oils exposed to various weight load.

This contribution deals with the computer simulation and the follow analysis of the rail vehicle running with wheel flat. It comprises of two parts. The first part addresses to the problem of rail vehicle operational, which wheel is damaged. There are several types of wheel damages. In this work the wheel flat problem is introduced. Generally, the rail vehicle running with wheel flat is adverse because the track can be shopworn, some parts of rail vehicle can be damaged and also operational condition for passenger or goods (depending on kind of rail vehicle) can be worse markedly. There is also included a system of forces and accelerations measurement during rail vehicle running on the given track section. The second part includes computer modelling and simulation of this phenomenon. Analyses were focused on the assessemnt of the rail vehicle motion smoothness and its damaging impact on the track. For this, there was created computer model of a twin-bogies passenger car, which the one wheel was modelled as damaged, i.e. wheel flat. Then, there were performed simulations of the rail vehicle running at various speeds. The passenger car was run on the straight track without irregularities in order to avoid adding excitation. Subsequently, values of the vertical wheel forces of the wheel with flat was evaluated.

This work deals with fatigue testing of the EN S355 structural steel welded joint. The weld was manufactured by the MIG welding technology and as the filler material was used the G3Si1 wire. The fatigue tests were carried out in the rotating bending mode on the specimens manufactured from the welded joint of the S355 steel. The main aim was to evaluate the fatigue endurance of the weld material and for this reason were used machined axis symmetrical specimens to remove the notch effect of the weld shape. In order to increase the fatigue endurance of the weld, the Nd-YAG laser was used for laser shock peening (LSP) of specimens surfaces, which lead to removing of the weld defects but in overall caused that LSP has behaved as the notch and lead to decreasing of the fatigue endurance. Obtained results of fatigue tests are compared, discussed and supported by correlation with results of additional experiments, e.g. identification of incurred structures after the laser shock peening by the metallographic observations and micro-hardness tests.

The ultrasonic/ceramic membrane combined process was employed to have a better effect of the filtrated water quality. We set the ultrasonic frequency at 20 kHz and the corresponding power at 2kW. Innovatively we probed into different range of molar weight of organic matters in the filtrated water, and results showed that the ultrasonic/ceramic membrane combined process could change the distribution of micromolecule organic matters. We found that with the increasing of turbidity of raw water, the membrane flux decreased rapidly but the quality of filtrated water changed little. Studies on different range of molar weight showed that for the organic matters whose molar weight were below 1kD, higher turbidity had an optimistic effect on removing them while for those whose molar weight were above 1kD, the effect was reverse.

A mechanical treatment of an adherent before an application of adhesives is one of key factors influencing resultant strength of an adhesive bond. A grit blasting belongs among one of the most often used methods of the surface treatment. A resultant structure of blasted adherent and also parameters of the surface roughness can be changed during the blasting by a suitable choice of many parameters among which a material and a size of abrasive particles, a distance of an air jet and a blasted material, a size of the jet, an air pressure and an angle of abrasive particles impact can be ranked. This experiment describes an injector system of grit blasting using basic abrasives - corundum and glass ballotini. During grit blasting of common steel adherent it came to the change of the impact angle of the abrasive particle in a range from 75° (a perpendicular angle) to 10°. Different impact angle led to different roughness parameters and to various structure of the adherent surface which was evaluated by an electron microscopy. Subsequently, it came to experimental description of the strength of adhesive bonds which were created by adherents whose surface was grit blasted under various impact angles of abrasive particles.

This article offers a novel method of gold nanoparticles preparation which increases their obsevation feasibility. Gold nanoparticles were prepared by sputtering of 6 nm of gold on surface of NaCl crystals and consequent annealing. Gold nanoparticles were separated from the substrate mechanically in the ultrasonic bath. The preparation of gold nanoparticles on NaCl substate is extremely versatile. It enables to descibe size and shape of the individual nanoparticles much better than usually used SEM and AFM techniques, it enables to see the lattice arrangements and also to do more precise chemical analysis without the influence of the substrate. It is applicable for characterization of temperature-, time-, chemical composition- and atmosphere influence on morphology of gold nanoparticles. The nanoparticles were observed by HRTEM. In our case, the influence of carbon addition on morphology of gold nanoparticles was studied by sputtering one or two carbon interlayes in the gold layer. It was found out that one carbon interlayer slightly descrease nanoparticle size. On the other hand, two carbon interlayers lead to formation of irregular large shapes of the gold particles.

A soil processing belongs among basic steps in an area of a crop farming. The research was focused on increasing a service life of ploughshares by an overlaying technology. The research within field conditions was focused on innovations of ploughshares in the area of a conventional processing of the soil by means of the overlaying technology. A new functional profile was created by means of overlaying electrodes on the conventional tool in order to respect drainage of the processed soil, i.e. oblique overlays. The overlaying material was put in the most stressed places of the ploughshare, i.e. parallel with a face and an edge and these both in a front as well as in a back part. New functional surface was distinguished for a reinforcement of a top of the ploughshare edge and the back part of the ploughshare. Overlaying material was of carbide type OK Tubrodur 15.82. Within the tools service life testing under the field conditions the change of the tools shape and their mass loss were investigated. Statistical methods were used for evaluating of the experiments.

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.

Merchant's model of chips formation considers an "ideal" (sharp) cutting edge. However, nowadays many manufacturers of cutting tools modify the tool geometry with the goal to increase the tool life and to improve the surface quality. The processes, at which the modified tools are used, go along with chip formation and physical phenomena that differ from Merchant's model.
The article deals with the simulation of chip formation at various ratios of rounded cutting edge and cutting thickness. Aim of the research has been focused on the interpretation of new knowledge from the cutting theory. Authors have tried to understand the theory of cutting process by means of simulation and provide the recommendations for practical usage. They explain the differences between the Merchant's model with a sharp edge and a model with a rounded cutting edge. The contribution describes changes and manifestations of physical phenomena result from given conditions. There were also simulated dependencies of the tool load on the radius of cutting edge in the article. Achieved results will enable not only better integration of cutting tools into the manufacturing, but they also allow to increase the machining efficiency.

A chemical cleaning of an adhesive bonded surface is a significant technological factor at a creation of an adhesive bond. Owing to the fact that producers do not provide information about releasing of harmful substances into the atmosphere mass values of a flow of pollutants were experimentally tested in various chemical environments serving for an adhesive bonded surface treatment. A piece of knowledge of the mass flow of the pollutants which are released into the space is a possible solution which is dealt with in this paper. There is a difference in the individual chemical treatments influence on the adhesive bond strength. The scanning electron microscopy was used for the evaluation of the influence of the chemical treatment of the adhesive bonded material on the adhesive bond quality. The adhesive bond strength was determined depending on the chemical treatment of the surface on the base of mechanical tests. The adhesive bonded surface treatment did not change the fracture surface. The optimum values of the adhesive bond strength and the lowest values of the evaporation in the environment at the same time were reached at perchlorethylene and toluene.

The article deals with the results of the simulation analysis of a railway wagon bogie model. We analysed four freight wagon bogie variants for its dynamics properties research. The bogie models correspond in general to the Y25 bogie concept. The models were created in SIMPACK software enhanced by the RAIL module. From the research results depicted in the graphs we found out, that the newly designed bogie variant gives the best results when compared to the other analysed versions. The newly designed model consists of a standard Y25 bogie frame with two Lenoire friction dampers. This bogie is equipped with longitudinal linkages on both sides. These linkages are completed with a radial torsion binding, torsion rod, between side bogie parts. The contact of railway wheels and rails generates active forces affecting the surface contact, affecting the size of the normal and tangential stress, wear surfaces of the wheel/rail, or directly the size of the derailment.