Fulltext search in archive

The aim of this paper is the comparison of selected rheological properties of polymeric composites with glass fibers materials before and after exposure in UV box. Rate and depth of degradation induced by the environment were evaluated by Frequency Sweep Test, which monitors changes in viscoelastic properties of polymers with respect to their molecular structure and their behavior in thermoplastic processes. Degradation process resulted in changes of complex dynamic viscosity, storage and loss modulus, changes in molecular weight and its distribution. UV radiation is intense degradation factors affecting the change in the structure and properties of polymers - the polymer matrix gradually degrades by UV radiation, the viscosity of the composites decreases, the COP is moved to lower angular frequencies with increasing molar mass.

Spin coating is basic method for preparation of thin polymer resist layer (polycarbonate) or colloidal solution (grapheme oxide in alcohol). This method main benefits are speed of preparation and the possibility of tuning final coating of silicon sample by variations of parameters such as the speed of rotation, time and the amount of the solution. To find out the exact graphene oxide layer spin coating process a planned experiment was designed. The greatest coverage of the silicon sample grapheme was obtained by studying the data obtained from electron microscopy (SEM) and light microscopy (LM) of the spin coating input conditions

In the last decades, advanced brake technology in the port sector follows the global productivity developments of the international maritime trade. Container vessels are getting bigger and bigger and the ship to shore cranes is getting consistently higher. But service, emergency or storm brakes cannot be getting bigger and bigger to meet these increasing demands. Throughout history, innovations and advancements in technology have made industry better through automation and increased efficiency. No matter how advanced industry becomes, the need for emergency duty stopping brakes will not go out of style because there are always circumstances that require mechanical brakes to do the job. Brakes will invariably insure against those rare, yet potentially catastrophic events that even modern technology cannot defend against.

Passing of vehicles along curved track is a serious technical problem, which needs special attention. It is especially actual in the environment of urban lines, where it is necessary to pass a track of small radius. There is a significant strain of track as well as tram's bogies. It results in excessive wear in rail-wheel contact. Considerable is also the noise caused by operation on such track. Behavior of the vehicle when riding along track curve is influenced by the wheelset guidance design. If the wheelset guidance is able to set the wheelsets in track curve to a radial position, mitigation of the negative phenomenon can be expected. This paper deals with a design of a mechanism for setting wheelsets in a track curve to a radial position for tram cars. Dynamical analysis of a simplified tram car model was performed. Courses of monitored values of bogie with and without designed mechanism are compared.

The use of a new method of attaching fixed blades to a stator disc led to the need for evaluating the strength of a riveted joint. Conventional mechanical testing revealed large variations in the strength of this joint. After sectioning the joint, it was found that the shank did not fill completely the hole in the shroud of the disc. Further investigation involved numerical simulations using the DEFORM software, because securing additional samples for physical examination was complicated. The first simulation task focused on determining the tearing-out force, taking into account work hardening of the shank material due to plastic deformation. The second simulation task aimed to identify optimum initial dimensions of the shank. The goal was to ensure that the rotary upsetting process causes the shank to completely fill the hole in the shroud. As a result, the joint strength would be improved and, above all, the variation in strength eliminated.

On the base of a well-known method of machining with disk-shaped rotating tool the self-propelled tool was designed. The principle is based on braking the tool rotation during machining, until the moment of determined wear criterion on the tool flank. As with the growth of tool wear the force of cutting resistance increases, it is possible to use it for automatic tool swinging into a new position by which a new part of cutting edge comes into engagement. The paper describes the tool design, theoretical analysis of Rz after machining and actual experimental machining results.

The aim of the research was to compare a classical (turning) machining and an abrasive-free ultrasonic machining (bufo) at three different materials. The surface was evaluated on the basis of an Olympus LEXT 3100 measuring of a surface roughness and hardness HV5. An ultrasonic set I - 4 consisted of the ultrasonic generator, power output 630 W and working frequency 22 kHz ± 10%, was used for the research. Main results are: increasing of the hardness HV5 of the machined surface, lowering of the roughness parameters Ra at the application of the abrasive-free ultrasonic machining, lowering of the roughness parameters Rz was not statistically proved at the application of the abrasive-free ultrasonic machining. It is possible to say according to a visual observing of the steel sample surface that a corrosive resistance was increased at the application of the abrasive-free ultrasonic machining.

The research is focused on an analysis of bonds adhesive bonded with structural two-component epoxy adhesives by means of an electron microscopy. The paper deals with an evaluation of basic factors influencing an adhesive bond creation with an emphasis on a resultant adhesive bond quality. The adhesive bond quality was reviewed on the basis of an assessment of reached adhesive bond strength, a fracture surface and by a research on adhesive bonds cuts by means of the optical analysis (SEM). Evaluated criteria of the adhesive bond creation were: the adhesive bonded surface treatment, the time of an adhesive workability and the loading value at the fixation of adhesive parts. The results of SEM analysis proved an occurrence of impurities in the adhesive bond at omitting the chemical cleaning of the adhesive bond which get into the adhesive layer. The adhesive bond strength fall was more than 70 %. The strength and the quality of the adhesive bond depend on the adhesive bonded surface treatment, the adhesive workability time and the loading value of the adhesive bond at its creation. Above mentioned conclusions were proved by the mechanical tests and SEM analysis.

This article deals with the analysis of the chemical pre-treatment influence on the corrosion resistance of the low carbon unalloyed steel material after cold forming. These are the pre-treatments nanotechnology based. The layer is created by sol-gel technology. Except two used types of nano chemical pre-treatments is also used classical ferric phosphate. The six variants of chemical pre-treatments were prepared and these variants were then compared in terms of corrosion resistance and the way of exclusion and surface morphology using SEM and EDS analysis. The experimental samples were prepared for each variant. They were observed macroscopically and using SEM before corrosion load. These analysis shows the differences between each variant. Using SEM and EDS analysis was searched the typical elements for each variant and was observed the excluded layer and potential defects. The experimental samples were placed in the corrosion chamber and loaded according to the standard CSN EN ISO 9227 after this analyses. The surface of the experimental samples were without any other protection thus there was observed changes on the surface of the samples after one hour. The corrosion loading was finished after 24 hours. Experimental samples were evaluated macroscopically and were compared. The result of the experiment is the best variant of chemical pre-treatment in terms of corrosion protection of steel substrate concluded after all analyses and observations.

This study discusses the impact of heat treatment conditions on the final properties of quenched and low-tempered bearing components in terms of microstructure, hardness and impact strength. Technological process of heat treatment must be done rationally and in addition to the required hardness must also ensure the dimensional precision of bearings components. Different austenitization conditions have a great influence on the phenomena which takes place in the material during the austenitizing. Heat treatment of rolling bearing components is an indispensable part of their production and it is also an unavoidable item of the price calculation of bearings. The aim of a competitive struggle for the rolling bearings market is an offer of the best quality bearings (dimensional accuracy, stability and durability) at a reasonable price.

The situation of analysis and finding solution of unique material flow managing and planning in production company allows increasing the competitiveness company on the market. The uniqueness of the material flows is in its combination of metallurgical and machinery character. There are continuous metallurgical and discrete mechanical material flow with even different speed which are joining at one place - aluminium casting. The research has brought also the recommendation of new layout of the company. Each company is original from the point of production processes. Application of standard enterprise information system (SAP, proAlpha, Baan, etc.) need difficult adaptation especially for conditions of small or medium enterprises and the price of that system is relatively high. Therefore, the proposed model of capacity planning is much more suitable for the conditions, requires and demands of this enterprisers.

Presented research paper deals with possibilities of replacement of conventional mold materials by new, unconventional. Traditionally, laminate, wood or gypsum molds (in the case of small production series) are used for the production of composite parts. Furthermore, milled aluminum molds are conventionally used only for mass production. Due to this, thin metal sheet was prepared as an unconventional production mold for manufacturing of motorbike facing part. Vacuum bagging using prepared one side mold was chosen as the most appropriate technology. Normally, two facing sides are not commonly manufactured using this technology. Because of this, possibilities to create two facing sides at areas that are not in contact with mold itself were investigated. Presented results can help manufacturing companies with their production and considerably decrease manufacturing costs due to not necessity to use two side molds.

This article describes usage of ultrasonic method TOFD for testing of welds on plastic pipelines welded with butt fusion with hot plate. As an artificial defects were selected cold fusion and inclusion in the weld area, by using metallic tape and wire as a mentioned defects. To test defects was necessary to use wedges with water as a bonding agent. Results of testing are proof of usefulness of this method. It can severely reduce risks of accidents caused by unidentified defects, which can occur in welded joints. Since plastic pipelines are used even in nuclear industry as a replacement for metal pipelines for its resistance against radiaton decay, it is necessary to implement similar testing regulations to avoid fatal incidents and method like TOFD and Phased Array ultrasonic testing can prevent such failures.

Additive technologies belong to modern trends in production of prototype components. They include e.g. sintering of powders with a various chemical composition, granularity, physical, chemical and other usable qualities. There belong to additive technologies especially a technology of Rapid Prototyping that use various principles to make components. According to the used technology photopolymers, thermoplastics, a specially modified paper or metal powders are used in a Rapid Prototyping machinery.
An article deals with a characteristic, concept, calculation and production of a prototype model of an axial fan that enables quick build-up time of fan turbine speed. Production of the axial fan is realized by an additive technology of Rapid Prototyping using a method of Fused Deposition Modelling - a 3D printer Fortus 360mc. The article describes individual development stages from the concept to production itself including a final visualization of the prototype model of an 11-blade axial fan.

The paper presents the evaluation of tribiological properties and condition of the tool steel surface for hot work 55NiCrMoV6 (WNL). Due to the fact that the steel 55NiCrMoV6 is used for components operating at high temperature, the tribological tests were performed at the room temperature as well as higher temperature (150 °C). The wear tests were performer with help of ball-on-disc tribotester, according to the standard ASTM G-99. The applied load was 5 N and 20 N. The counter specimen consisted of balls with the diameter of 6 mm made of steel 100Cr6. Steel samples 55NiCrMoV6 undergone thermal improvement. The average hardness amounted to 57 HRC. The test was performed with the slip speed of the friction pair 0.15 m/s and sliding distance 200 m. During the test, one registered the friction coefficient, frictional force, temperature and the depth of friction. Then, one calculated the wear rate for the friction agents. The evaluation of friction was performed after tribiological tests. For the load of 5 N the average friction coefficient in the room temperature amounted to μ=0.46. At the temperature of 150 °C it increased up to μ=0.69. The wear rate for the sample subjected to tests at room temperature was 3.618×10-5 mm3N-1m-1. At the temperature of 150 °C it increased up to 8.058×10-5 mm3N-1m-1. The maximum Herzian stress was 1.099 GPa.
For the load of 20 N an average friction coefficient at the room temperature was μ=0.69. At the temperature of 150 °C the friction coefficient was μ=0.57. The wear rate for the sample subjected to tests at the room temperature amounted to 2.136×10-5 mm3N-1m-1. At the temperature of 150 °C it increased up to 2.737×10-5 mm3N-1m-1. The maximum Herzian stress was 1.741 GPa. The wear of the steel 55NiCrMoV6 increased with the increased temperature. It has been confirmed by application of two different loads. The basic wear consisted in abrasive wear.

This paper deals with materials of selected safety components of lifts and it describes their mechanical and chemical testing. It particularly concerns with chemical analysis of two basic types of pulleys from gray and ductile cast iron, and subsequently with the measurement of the hardness and the strength of these materials. The aim of the research was to prove if these types of pulleys, widely used as safety components in the lift industry, meet the current law requirements. Finally, the results of the research are briefly discussed as well as their application in the university education.

Numerical simulation of welding is an efficient tool for prediction of temperature distribution during welding process, residual stresses and final distortions of the welded parts. Importance of numerical analysis can be even higher during optimization of the large structures welding, in which preparing of the experimental samples is more expensive. Numerical analysis of T-joint welding for bridge construction parts in SYSWELD software is presented in the article. Welding simulation was prepared for two welding sequences with the same welding parameters required to ensure penetration of the weld metal. Obtained thermal analysis results were compared to measurement by thermocouples, and final distortions were compared with contactless measurement by TRITOP system. Lower distortion were obtained by simulation and experiments in welding at once by the two welding devices, while the second device followed the first one with technological delay of 25 seconds.

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.

High entropy alloys belongs to quite novel materials that are attracting far more attention throughout the entire materials research. They are characterized by wide range of unique properties e.q. ultra-high strength while maintaining its ductility, good corrosion resistance, wear resistance, thermal stability, magnetic properties and many others. Generally, they are composed at least by five elements with nearly eqiatomic compositions that are further characterized by high mixing entropy allowing only formation of solid solutions. The investigated CoCrFeNiMn high entropy alloy was prepared by powder metallurgy processes combining the mechanical alloying with high-tech compaction via spark plasma sintering. The microstructure of prepared compact alloy was examined by the optical microscopy and electron scanning microscopy with EDS detector. The chemical and phase composition was determined by the results of the XRF analysis and by X-ray diffraction analysis. Prepared alloy reached ultra-high compressive yield strength of 1570 MPa and hardness 352 HV 30 outperforming the cast alloy with identical chemical composition that reached only 230 MPa and 120 HV 30, respectively.

The present paper deals with the microstructure characterization of drosses originated during production of a new type of coating called Zinkomag. This coating creates during continuous galvanizing process and it is characterized by addition of 0.8 - 1.0 wt. % Mg and 0.8 - 1.0 wt. % Al in the zinc galvanizing bath. The addition of magnesium in such coatings leads to increasing of hardness, corrosion resistance, and better color adhesion than most common used coatings (GI coatings). In this paper drosses were investigated using AAS, LM, SEM with EDX microanalysis, and XRD.

In the present work Mg-Ga, Mg-Sn and Mg-In binary alloys with 1 and 3 wt.% Ga, Sn or In were studied in the as-cats state. Selected Mg-3Ga and Mg-3Sn binary alloys were subsequently extruded at 400 °C. Structures of investigated materials were studied using scanning electron microscopy and energy dispersive spectrometry. Mechanical properties were determined by Vickers hardness measurements and tensile and compressive testing. All materials were composed of primary magnesium dendrites and contained strong dendritic microsegregation. Both Ga and Sn have strengthening effect on magnesium; the effect of In is negligible. The extruded alloys were characterized by grain size in the range between 10-50 μm. Tensile yield strength and ultimate tensile strength of extruded alloys were clearly improved.

A "composite" is characterized as the comibation of two or more materials with diametrically different properties, which result into the creation of a new superior and unique material. This is the most commondefinition that holds true for all composites, however, more recently the term "composite" describes reinforced plastics. Polymers are used in every walk of life now-a-days. They are not even hundred years old, but play the significant role in every sector of life such as sports, defense, medicine, automotive, electrical, agricultural etc. In the beginning, polymers were considered as excellent insulators, but today also conductive polymers are available.. In general, polymers have good water resistance, but there are some polymers with good water absorbtion. Presented article deals with monitoring the changes in the mechanical properties of composites with polymer matrix. Composite has been formed from the PA (polyamide) matrix with glass fibers reinforcement. Mechanical properties, impact strength (Charpy) and micro-hardness (Vickers) have been evaluated on samples of the composite before and after the exposure of UV radiation.

Microscopy is mainly used in tribotechnical diagnostics for the analysis of the total number and morphology of the wear particles in the lubrication systems. Wear particles may accelerate wear and ultimately may cause a failure in lubricating systems. Therefore, this paper deals the tribodiagnostic problem which is focused on microscopic analysis of wear particles and additional tribodiagnostic analysis of motor oil. There was taken sample of motor oil after failure of turbocharger of combustion engine. The purpose of the paper is to compare the results of microscopic analysis for evaluation of wear particles in motor oil. These analyses are key for assessing wear of the combustion engine and for indicating of impending failure. The aim of this experiment was to assess hypothesis that scanning electron microscopy (SEM) is appropriate for tribology diagnostics of seized turbocharger of internal combustion engine.

Titanium-aluminium base nanomultilayer (NML) coatings are deposited by cathodic arc evaporation using pure titanium and aluminium with eighteen percent silicon cathodes. Each multilayer Ti-Al-Si-N structure consists of 49 bi-layers with different thickness. The external deposited layer is with five times longer growing period. The coatings are deposited at the pressure of 2 Pa and the substrate temperature of 400 °C. Polished steel discs (Ø 20 mm × 5 mm thick) are used as the substrate material.
This article presents an investigation of the surface morphology and mechanical properties of the coatings, particularly the adhesion and nanohardness. The AFM analysis indicates that the coatings are dense, with an average surface roughness in the range of 33 / 58 nm. The coating with the smaller value of average surface roughness exhibited a maximum hardness of 43 GPa. High calculated value of plasticity index (H/E) is 0.104. The scratch test results revealed that all the investigated coatings have very good adhesion in the normal loading interval from 1 N to 40 N.

The aim of the submitted paper is to study the influence of the speed of the penetration of the indenter into the test piece ranging from 0.302 μm s-1 to 1.089 μm s-1 and applied load ranging from 10 g to 100 g on measured values of micro-hardness. Whereas certified reference material with defined specified hardness and its uncertainty was used as a test piece, the measurement involved indirect calibration of the tester. The influence of observed factors on measured value of the micro-hardness was evaluated by Meyer's index n, PSR method and by Analysis of Variance (ANOVA). The influence of the load on the measured value of micro-hardness is statistically significant and the relationship between applied load and micro-hardness manifests "reverse" ISE. The velocity has statistically significant effect on the micro-hardness. Meyer's index on average decreases with increasing of the speed.

Modelling of cutting forces is important for understanding and simulation of the machining processes. This paper presents cutting force modelling of data obtained from machining of C45 carbon steel with a coated carbide tool. The model is based on a rather extensive measurement of 270 combinations of cutting tool geometry parameters (rake angle, clearance angle and helix angle), tool wear (flank wear average value), chip thickness and cutting velocity. The model with the friction and cutting component of the cutting force is presented and discussed. We conducted an analysis of the identified model and found a relationship between the increase in tangential and radial cutting forces and tool wear. We concluded that flank wear influences the cutting force acting on the worn tool more significantly than cutting tool geometry. This is caused by changes in cutting edge geometry and the resultant significant increase in the friction component of the cutting force as is shown using the identified model.

In this work there are published results about fatigue resistance of ductile iron with various types of matrix obtained at cyclic loading in very-high-cycle region. The results show continuous decrease of the stress amplitude with increasing of cycles number to the failure. The tensile strength increase is not accompanied with corresponding increase of fatigue properties. The fatigue durability decreases while the tensile strength increases.

From the viewpoint of residual stresses and microstructure of ground surface, Inconel 713 superalloy is an attractive material since it is frequently used in high temperature gas turbine applications where residual stresses are relevant for service life. The goal of this contribution is to find whether there exists a relation between grinding parameters and final surface integrity parameters such as residual stresses, roughness, crystalitte size, and generally, microstructure. Highly productive creep feed grinding has been applied to produce both simple flat areas and complex fir three blade root. It has been found that the used grinding method lead to very thin deformed layer on the surface with compressive residual stresses and fine crystallites. Moreover, the detailed analyses have been carried out in order to pinpoint plausible reasons behind crack origination.

The article deals with non-destructive measurement of the effective throat thickness of fillet weld with deep penetration in T-joint. Ultrasonic Phased Array technology is used to indirectly measurement of effective weld throat thickness. Phased Array ultrasonic systems utilise multi-element probes, which are individually excited under computer control. By exciting each element in a controlled manner, a focused beam of ultrasound can be generated. Software enables the beam to be steered. Two and three dimensional views can be generated showing the sizes and locations of any flaws detected. The results of Phased Array ultrasonic measurements are compared with the real results obtained from the real macrostructural analysis. The methodology is appropriate for verifying compliance with the design weld throat thickness in the production of steel structures.

Modification alloy is an important part of the metallurgical process, and this also applies, of course, for aluminum alloys, particularly for Al-Si (silumins). As a modification of the material we can use the modification using the selected element or heat treatment of alloys, or a combination of both processes. One of the elements that it is possible to modify the alloy of Al-Si used is antimony (Sb). The paper examines the possible effect of the modification that element and heat treatment on the final tool wear after machining of the alloy AlSi9CuMnNi. In the experiments were made three castings from the alloy AlSi9CuMnNi without modification, three castings with the modification and without heat treatment, three castings with modification and without heat treatment, and three castings with modification and heat treatment too. These all castings were machining by turning with the same cutting conditions and next the tool wear of using inserts was analyzed. The described experiments and analysis are part of extensive research, focusing on a Faculty of Production Technology and Management, J. E. Purkyne University in Usti nad Labem.