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The automotive industry is one of the most dynamically developing segments of the industrial production worldwide. The introduction of still increasingly stringent emission limits for newly developed cars forces car producers to still reduce the fuel consumption of cars. One option is to use hybrid drive units in combination with a redesign of the automobile body while maintaining the highest possible level of vehicle safety. For these reasons, the automotive industry has been increasingly demanding to apply and process low density (lightweight) alloys, including aluminium-based alloys. These materials are subject to high demands both in terms of mechanical properties and technological workability in the mass production process. The utilization of mathematical modelling (numerical simulations) of production processes is now one of the standards in all phases of design and production the car-body and allows the implementation of variable designs in a relatively short time scale and the detection of potential production problems as well. In this paper, the influence of the kinematic hardening model on the accuracy of spring-back prediction is shown in comparison with the commonly used isotropic hardening model. For deformation analysis, a simple workpiece having ?U-shape? of EN AW 6111 material was used. Such aluminium alloys is used for production car-body panels in the automotive industry. Achieved accuracy of numerical simulation results is evaluated by the comparison shape obtained by numerical simulations and shape of experimentally bended workpiece.

The paper is focused on the polymorphic transformations of selected steel types. Generally, when creating CCT diagrams, the transformation temperature values Ac1 and Ac3 are determined under at very low heating rates (max. 0.1 °C?s-1). The only exceptions are so-called in-situ CCT diagrams, which are determined based upon the real temperature cycles. However, in the case of dynamic processes such as welding technology or heat treatment with magnetic induction heating, cannot be used information from conventional CCT diagrams. Incorrectly selected temperatures lead either to incomplete austenitizing during heat treatment or to a different development of phase transformations in HAZ of welds. Especially, when these processes are carried out without soaking temperature. That is why as the main aim of this paper was to determine the heating rate influence for steels S460MC, S690QL and X23CrMoV12-1 on the shift of their transformation temperatures Ac1 and Ac3. The in-tensity of the heating rate effect on the transformation temperature depends on the steel structure and amount of alloying elements. Consequently, steels with different structures, different type of processing and mechanical properties were deliberately selected to make the assessment as complex as possible.

The effects of strengthening phase in particulate ceramic composites on their properties were studied in presented paper. The experimental materials were a monolithic Si3N4 and particulate ceramic composites consisting of Si3N4 matrix with different additions of the SiC strengthening phase (10 and 20 vol.%). The microstructure, density, hardness and fracture toughness of Si3N4 + SiC ceramic composite materials were compared with monolithic Si3N4 based ceramic material. The addition of SiC particles into the Si3N4 based matrix does not positively influence the phase transformation from ?-Si3N4 to ?-Si3N4 in Si3N4 + SiC ceramic composite materials, but it affects the growth of prismatic ?-Si3N4 grains and contributes to the creation of fine-grained microstructure. The increase of SiC strengthening phase portion slightly increases relative density of Si3N4 + SiC ceramic composite materials. The hardness of ceramic materials increased from 14.48 GPa at monolithic Si3N4 ceramics to 16.99 GPa at ceramic composite with 20 vol.% SiC. The highest fracture toughness value of 8.30 MPa.m1/2 was achieved for monolithic Si3N4 ceramics, the lowest value of 7.09 MPa.m1/2 was achieved for ceramic composite with 20 vol.% SiC.

In this paper, the possibilities of selective laser melting (SLM), one of metal additive manufacturing technologies, in the preparation of trabecular structures are discussed. Despite great advantages in geometrical freedom, there are specific process-inherent aspects that must be considered before the production of such structures. To verify SLM capabilities, we tested different orientations (horizontal and vertical) and thicknesses (0.2-4.0 mm) of single struts. Significant irregularities in strut thickness and deviations from the designed cross-sectional area were observed. Horizontal struts showed greater geometrical deviations. Based on our observations, a trabecular structure was prepared with all struts inclined 45° from the building platform. Due to the 72% porosity, mechanical properties approached those of the bone, which is beneficial for the application of such structure in orthopaedics for bone tissue substitution.

The aim of the study was to compare the strength of assembly joints of sleeve elements made of different structural, polymeric materials. Experimental tests were carried out to determine the mechanical properties of adhesive and welded joints. Adhesive joints were made of polyvinyl chloride pipes with the use of three types of adhesives: Epidian 53/PAC/100:80, Epidian 53/TFF/100:22, Vodaro 15010-VO. The welded joints were made of polypropylene pipes. All of the joints have been made with the use of a pipe fitting allowing for correct joints. Then the completed joints were subjected to destructive strength tests. The obtained results made it possible to carry out statistical analysis, which aimed at determining significant differences between the various methods of assembly. The tests carried out proved that the adhesive joints made with the Vodaro 15010-VO one-component adhesive were characterized by the highest strength - 2.30 MPa. The lowest strength was obtained in the case of adhesive joints made with Epidian 53/TFF/100:22 - 0.45 MPa epoxy ad-hesive composition. Statistical analysis showed that the strength obtained in case of adhesive joints made with epoxy compositions differs significantly from the strength of adhesive joints made with Vodaro adhe-sive. No significant differences at the assumed level of significance α=0.05 were also observed in the case of the strength of PP-R adhesive joints made with Vodaro adhesive and the strength of PVC-U welded joints.

Deep sea nodules are considered as an alternative and very rich source of several metals. Up to pre-sent days, the processing of these polymetallic ores is cosidered to be carried out by the extraction of individual metals. This work deals with the processing of the deep-sea nodules by metalothermic method by aluminium and silicon. The nodules are reduced complexely without the extraction of individual metals, forming the polymetallic alloys. Reduction was carried out in a small scale with the initiation in an electric resistance furnace. Microstructures of the formed alloys and the slag were described in dependence on the excess of the reduction agent against the stoichiometry. Even though both of the reduction agents are generally applicable, reduction by aluminium was proved to be more efficient and leads to more complex alloys.

The paper reviews the results of an evaluation of the influence of the operating factors on traction-adhesive prop-er-ties of a locomotive. Planning of an xperiment was performed for two locomotives ?freight locomotive 2TE116 and shunting locomotive TEM103. The input for performing the numerical experiment was variation of 6 factors: the change in the wheel diameter of the first wheelset due to wear, the change in the mass of the locomotive as a result of the change in the amount of the fuel as well as the wheel rims wear, the impact of the friction damper in the primary suspension, change in the primary and secondary suspension stiffness due to operation. Regression equati-ons were obtained in code and natural form, which describe the effect of operating factors on the coeffi-cient of utilization of the locomotive adhesion mass.

Grinding is one of the basic finishing operations which can be used for parts made from different materials where high quality and surface accuracy is required. One of these materials is maraging steel 1.2709, which is used for the test samples for tensile testing. In this case, it is very important to achieve good surface quality. Wear of a grinding wheel is best expressed as G-ratio which shows us if the grinding parameters are selected correctly. This article deals with the influence of grinding conditions and grinding wheels on surface roughness and wear of the grinding wheels when grinding tool steel VACO 180 on a 5-axis grinding machine. The experiment was designed to investigate the influence of changes in cutting speed, depth of cut and using two different grinding wheels for these two values. At the end of the article, the results from the experiment are summarized and compared.

In the recent years, the demand for weight reduction in modern vehicle construction has led to an increase in the application of hydroforming processes for production of automotive and aerospace lightweight components. The tube hydroforming measurement site (TH stand), designed and built at Warsaw University of Technology allows both die, and free tube hydroforming processes to be performed, thereby making it possible to obtain information about the material, as well as optimal process parameters [1][2]. The present freshly patented method for metal tube hydroforming is dedicated to short product series or even single products and prototypes [3]. The method is applicable to forming difficult-to-machine materials. The well-known techniques use dies made of plastic or wood, especially to form short product series. The use of moulding sand and properly prepared geometry of casting mould makes possible shaping materials at high temperatures, which could not be done in previous short series solutions, where a plastic or wooden die were used. [1] Sadłowska H., Jasiński C. Morawiński Ł., Strain measurements on the tube hydroforming testing machine, Archives of Metals and Metallurgy Vol. 65 , Issue 1, 2020, pp. 257-263 [2] Sadłowska H., Odkształcanie się rur podczas swobodnego rozpęczania hydromechanicznego na stanowisku TH, w: Prace Naukowe Politechniki Warszawskiej. Mechanika, Vol. 267, 2015, ss. 25-30 (in Polish) [3] Patent No. PL424401, Kochański A., Sadłowska H., Bulletin of the Patent Office of Inventions and Utility Models vol. 17_2019, pp. 11

Direct Metal Laser Sintering (DMLS) is a method which builds metal parts in a layer by layer procedure. The melting of metal powder by a laser beam is a complex physical metallurgical process and successful processing of the whole manufacturing procedure requires complex management. Therefore, a successful result is not guaran-teed. The print job is designed based on the designer?s personal experience, and the possibility to verify the cor-rectness of a job proposal would save time and money. Nowadays, there are many kinds of software which allow timely detection of errors in the print job design. This paper deals with demonstrations of print task simulations. The results from actual simulations are useful as support for the print job designer, but they do not completely substitute for real production tests of parts.

This paper deals with the experimental testing of the basic crash element, which is made of PA6 with short carbon fiber reinforcement by additive technology. Additive technologies allow the production of very complex, thin-walled and hollow shapes, which can be used to tune the desired characteristics of the deformation member. The variable size of the deceleration, the length of the deformed portion and the total amount of energy absorbed can be controlled by suitable geometry. The initial impact peaks can be reduced by gradually changing the geometry. Experimental testing of basic crash elements was performed on several specimens and average values are used here. Primarily the maximal and average deceleration and total energy absorbed are monitored. Obtained data will be used for validation of material properties in Crash-Pam software. Using a validated material model, larg-er and more complex deformation members will be proposed, eg for the racing car Formula SAE.

Processing of synthetic diamonds is accompanied by low productivity and high values of relative con-sumption of diamond wheels. The coefficient of use of diamond grains in these processes does not exceed 5-10%. Using synthetic diamonds as a blade tool, requires sharpening and refinement. This study proposes to use ultra-high-speed machining modes and the same diamond grinding wheel at all stages of tool shaping. At the first stage, i.e. at high speeds, a rough productive sharpening of dia-mond blade tool is made with a wheel on an iron-based binder. At the second stage processing speed is reduced, as a result grains cease to self-sharpen and to wear out. When the iron binder comes into contact with the sharpened diamond, the speed must be increased, so that the temperature in the contact zone of the binder with the rough surface of the cutter, increases. Due to diffusion wear, from the surface of the diamond, the height of the roughness micro-hills decreases. In other words, the process of high-quality thermally activated refinement of the working surface of the diamond cutter starts to be implemented.

The submitted paper describes the utilization of numerical simulations to predict sheet metal forming process of ultra-high strength TRIP steel HCT690T EN 10346. Numerical simulations of production processes are increasingly becoming an integral part of the pre-production stage of the sheet metal forming processes. Furthermore, it is possible to use these numerical simulations not only in the production itself (e.g. to test the validity of the process or influence of process parameters, etc.), but also in the post-production stage as a tool for various controls and comparative measurements with the real processes, testing the capacity of the process and so on. For proper and the reliable course of the numerical simulation must be at first obtained and then entered the correct input data into the numerical simulation software. This data enters into the simulation in the form of definition the material computational model. Such computational model is defined by using material data and individual material characteristics at different loading methods. With regard to the material model and the given process parameters, it is possible to realize the process simulation, which takes place in the numerical simulation software – in this paper was used PAM STAMP 2G from the French company ESI Group.

Steels which are used for manufacturing of highly stressed parts of military equipments such as barrels of small arms weapons must be modified by heat treatment due to achieve required mechanical properties. Moreover, other important properties of functional parts, especially a friction coefficient and surface pa-rameters of bore of barrels, must be optimized due to obtain the best accuracy in target and to increase the life time of barrel [1, 2]. The technology chromium plating, very widespread in the past, has been gradually replacing by more ecological nethods. This article is devoted to find a technology as a replacement of tradi-tional chromium plating. Experiments are focused on using of optimized gas nitriding processes for surface treatment. As a result, a higher surface hardness with low influence on the dimensional accuracy is expected. Gas nitriding process was applied to steels 42CrMo4 and 32CrMoV12-10 used for barrel manufacturing. The most important parts of barrel were evaluated, especially surface parameters as a morphology than chemical composition and naturaly a microstructure of the material. The analysis of surface morphology were performed by scanning electron microscopy; chemical composition was evaluated by GDOES method and mechanical properties by using microhardness methods. The measurements of depth of diffusion layer were performed by destructive and non-destructive methods. The measurements showed the influences of chemical composition of alloying elements in core of material after chemical-heat treatment process on depth of diffusion and influence of technology on development of porosity. All fundamental mechanical prop-erties significant for requiring function of barrel were documented [1, 2]. Nevertheless, the main task was the description of the porosity development in compound layer after gas nitriding and the increasing of sur-face hardness and the depth of diffusion layer according to chemical composition. Nitriding process was ap-plied for increasing of surface hardness of material in depth and improving of mechanical properties. Me-chanical properties of tested material were significantly increased.

The paper deals with processing of material in semisolid state by the technology of semisolid squeeze casting. The investigated material was a subeutectic aluminium alloy AlSi7Mg0.3. The influence of various preparation meth-ods of batch material on the structure after processing by this technology was studied. Alloy AlSi7Mg0.3 was pre-pared as gravity cast, inoculated, heat treated and by technology of direct squeeze casting. In article is assessed microstructure of castings before and after processing by technology of semisolid squeeze casting. The shape and distribution of eutectic silicon was observed. The shape and the distribution of alpha phase formations has an im-pact on whether micro-volumes of molten eutectic will be closed in alpha phase or will be segregated along the boundaries of alpha phase formations. It was observed the partial inheritance in microstructure. Also the segrega-tion in surface layer was observed.

Currently, companies have been trying to make the use of their technology, manufacturing capabilities and experienced workforce to respond flexibly to market demands. Collecting and processing of all relevant data in the company is one of the key points to which increased attention should be paid so as to maximize the efficient use of own resources and consequently ensure a continuous reduction of pro-duction costs. The article deals with the use of burning machines in engineering company. The product range involves the production of burnouts from standard and special materials as well as welded steel parts of structures. The company has long struggled to optimize the material and information flow between particular production operations. This paper was focused on information flow logistics, which proved to be the biggest weakness of the central material preparation department during the bottleneck analysis. The scientific contribution of the resolved issue can be seen mainly in the possibility of inter-connecting process analysis and optimization of material and information flows.

Thanks to today’s computer programs, engineers can derive a large amount of information from chemical com-position of a material. This information includes phase transformation temperatures Ac1, Ac3, Ms and Mf. CCT and TTT diagrams for austenite decomposition can be determined as well. When steel is heated, austenite grains nu-cleate and grow in the initial microstructure. On cooling, the grains decompose into pearlite, ferrite, cementite and hardening phases. Transformations of this kind are thoroughly described in literature: the ways the individual phases form and the speed of their formation and temperatures involved. However, in-situ visual recordings of such transformations are relatively rare. With Linkam TS1400XY high-temperature stage and chamber integrat-ed in an optical microscope, one can observe phase transformations in situ during heating and cooling. This paper explores microstructural evolution in 42SiCr steel in the course of heat treatment in a high-temperature chamber on an optical microscope stage which offers observation of changes in the material right under the microscope objective.

Modern production systems requires high effectivity and flexibility with always increasing demands for precision as an imperative for more efficient components. The same apply for quality inspection providing data for feedback regu-lation of production processes. CMMs (coordinate measuring machines) which are flexible and universal in use yet very accurate and easy to automate are a standard mean for quality inspection. With many sensors available on the market, central fixed scanning heads with tactile scanning probes are a reference equipment for inspection of precise production of engine and transmission components. Tactile probes are right choice where very high accuracies and stability of results is required. Effectivity was allways a target in production processes and today the same pressure for effectivity and productivity is required from measuring machines, yet measurement strategies are often taken from measurement plans even 10 years old. This means that in old programs low scan speeds are used based on capability of older technologies and the approach of don´t change it when it works is common. This limits productivity of the whole quality control process. Motivation for this paper and whole research is to increase productivity and thus capaci-ty of quliaty inspection without compromising process capability. Lack of measuring capacity is usually solved by purchase of a new machine which may not be allways necessary. Primary motivation of companies supplying these technologies is not maximum efficiency of quality inspection, which in context of spare capacities ultimately means lower sales. Aim of this article is to describe influence of scanning speed and size of inspected feature on CMMs accu-racy. High-precision CMM control itself is not easy because with decreasing path radius dynamic effects of machine construction itself increase on measurement results. Accuracy of CMM measurement is then function of feature size being checked. This knowledge can be used for optimization of measurement plans in terms of productivity while maintaining sufficient measurement accuracy depending on required tolerance.

Magnesium materials are interesting for application in medicine as biodegradable implants. There is an ef-fort to improve mechanical and corrosion properties for this application. Powder metallurgy seems to be a progressive method suitable for improving those demanded properties. Therefore, this paper deals with the preparation of pure Mg by extrusion of milled powder. The milling process should lead to better homogenei-ty of microstructure and the disturbing of the oxide layer on the powder particles. Also, the input deformation energy in the milled powder should affect the deformation and recrystallization process during extrusion. In this paper, the influence of extrusion temperature on microstructure, mechanical, and corrosion properties is evaluated. Higher extrusion temperature leads to the larger deformed grains in the extrusion direction and higher tensile strengths. On the other hand, the plasticity and compressive yield strengths are reduced with higher extrusion temperatures. Corrosion properties are negatively affected by the iron inclusions incorpo-rated in the structure during milling. Otherwise, corrosion resistance decrease with increasing extrusion tem-perature due to the grain size.

The authors presented paper deals with experimental measurement and evaluation of nanomechanical properties of hard turned and grinded surfaces on the cross section specimens made of the 33NiCrMoV15 steel. 33NiCrMoV15 steel was selected to perform for all realized investigations. Even before the start of the experi-ments that investigated the effect of hard finish turning against grinding, it was necessary to subject the investi-gated 33NiCrMoV15 steel to basic research with regard to its chemical composition, fundamental microstructure and basic mechanical properties. The microstructure was performed on Neophot 32 optical microscope. Chemical composition was realized on the spectral analyzer Spectrolab Jr CCD. Mechanical properties, like nanohardness H and reduced Young modulus Er were subsequently performed on the Hysitron TI950 Triboindenter with a Cube Corner measuring tip, and evaluated by software Triboscan. Based on the acquired values, a 2D nanostructure of the distribution map of s H and Er was then evaluated in Matlab. This scientific research, together with all measured and calculated values, is the fundamental that will help to optimizing the quality and used all these results to optimize presented material and technological processes in term of surface integrity.

The use of lathe chucks in machine building companies is the result of a great deal of work and the develop-ment of technical thought. Due to the progress and the possibility of increasing efficiency and at the same time relieving people from work that requires a lot of effort, especially physical effort, the use of better and more efficient production methods is a target that should be pursued nowadays. In the manufacturing pro-cess, these objectives can be achieved with the use of dedicated equipment. The following work will present an example of a lathe chuck specialized in turning operations. The aim of the work was to use a universal chuck as a base for designing and manufacturing a specialized chuck so that it is possible to mount rope wheels with diameters from 240 to 580 mm. This would eliminate the necessity of time-consuming changeo-vers. In addition, it is assumed that the handle must meet the conditions imposed by the limited number of tools and the working dimensions of the machine. The machining process itself was also important, where the most advantageous solution was to perform most of the operations in one clamping.

Prototype production is a key element in the process of developing a new product. The prototype is important both for the initial materialization of ideas and intentions for product design, as well as for subsequent assessment of the technological design of this design. 3D printing technology is also used today as a suitable technology for prototype production, especially for the possibility of relatively rapid adaptation to complex shape geometries, the ability to produce what would be difficult or impossible to produce with conventional technologies, and last but not least, the increasing availability of 3D printing equipment.This paper demonstrates the principle of production of auxiliary gauges, for checking the dimensions of a prototype product with complex shape, 3D printing and its further possible use in the conditions of an engineering company. The conclusions of the paper should show the possibility and suitability of integration of modern and classical production technologies in the conditions of piece or custom production.

Three cutting technologies, plasma, laser, and acetylene, were used to produce the same geometry of a hole with 33 cm diameter. The plates of the same steel St-37 (1.0038, ČSN 11375) with a thickness of 50 mm were used in all three cases and the aim of the work was to evaluate and compare micro-structure changes of the cut surfaces. Longitudinal and transverse samples were taken from all cuts for subsequent analysis. Light and scanning electron microscopy of surface and below-surface areas were carried out at all samples. Hardness profiles were determined by micro-hardness and nano-hardness measurements. Based on these results, the depth of material that was influenced by cutting was established by image analysis of light micrographs, micro-hardness measurement and nano-hardness measurement. It was found out, that all three technologies influence significantly micro-structure and surface hardness of cut steel. Acetylene cutting resulted in the deepest affected zone consisting of several layers with gradually changing microstructures based on various ferritic-carbidic morphologies.

The article deals with a practical problem solution of the steel 15 128 steam pipeline properties change after prolonged exposure. Steam pipelines made of steel are stressed for a long time at higher temperatures and pressures and under conditions that are not constant throughout the pipeline operation. During operation, it occurs in the degradation processes, which are accompanied by changes in structure and mechanical properties. In terms of mechanical properties, it is mainly important the impact strength. The paper examines steam pipeline after long-term exploitation and results from microstructure evaluation, fractographic analysis, and comparison of impact strength test results.

Surface integrity plays an important role in the functional performance of mechanical components and is one of the most particular consumer requirements in machined parts. Customarily, surface roughness is considered to be the principal parameter in evaluating surface integrity and surface quality on machined parts and has a significant effect on service reliability and component durability. It is dependent on a large number of machining parameters, such as tool geometry (i.e. nose radius, edge geometry, rake angle, etc.) and cutting conditions (feed, cutting speed, depth of cut). The effects of these parameters have not however been adequately quantified. So in order to identify the optimum combination of cutting conditions corresponding to better roughness, accurate predictive models for surface roughness must, as a first step, be constructed. An investigation in this regard has been conducted to address the surface integrity optimisation and prediction issue by applying the polynomial regression method for a variety of experiments and cutting conditions. A higher correlation coefficient (R?) was obtained with a cubic regression model, which had a value of 0.9480 for Ra. The use of the response surface optimisation and composite desirability show that the optimal set of machining parameters values are (250m/min, 0.2398 mm/rev and 2.3383 mm) for cutting speed, feed and depth of cut, respectively. The optimised surface roughness parameter and productivity are Ra =2.7567 ?m and Q = 95.341*103 mm3/ min, respectively. Results show that the models developed can accurately predict the roughness on the basis of measured cutting conditions as input parameters, and can also be used to control the surface roughness by making a comparison between measured and estimated values. Furthermore, operators can benefit from the proposed models if the aim is the reverse determination of the cutting conditions corresponding to the requested roughness profile.

Projection welding belongs to the group of resistance welding technologies. The basic process parameters are the welding current and the current flow time. Although the resistance projection welding of nuts on galvanized steel sheets is widely used in industry, only a few research articles have been published. The resistance projection weld-ability of the fasteners on metal sheets is not as well understood as the resistance spot weldability of the sheets, so complex studies for the wider application of resistance welding of nuts in the automotive industry are still needed. This research is aimed at valuation the effect of resistance projection welding parameters (steel nuts on galvanized steel sheet DP 600) on joint properties. The hard welding mode (high welding current, clamping force and short welding time) provided 2 times higher strength of the weld joints as the soft welding mode. When using the soft welding mode, an increased Zn concentration from the sheet metal coating was measured in the transition area between the welded materials at the folding locations. When applying the hard welding mode, only a slight in-crease in the Zn concentration was observed at the inner boundary of the weld joint.

At the present time, mechanical vibration is undesirable in many cases. Therefore it is necessary to minimize unwanted vibrations in any appropriate manner. This paper is focused on a study of factors influencing vibration damping properties that were investigated using multilayer composite structures. Frequency dependencies of the displacement transmissibility over a frequency range of 2?1500 Hz were determined by the method of forced oscillations. It was found in this study that the vibration damping properties of investigated multilayer structures are significantly influenced by number of material layers, excitation frequency of mechanical vibration, applied materials in multilayer structures, inertial mass, material thickness and density. It was also observed that a superior ability to damp mechanical vibration leads to a shift of the first resonance frequency peak position to lower excitation frequencies.

The aim of the article is to compare the experimental investigation of deflection of the sandwich composite beam with theoretical models. The experimental test specimens were composed of three layers. Skins were made using epoxy-resin-impregnated glass laminates with plain weave. The light weight foam Divinycell H100 was used as sandwich core. The three-point bending test was carried out. Fibre-optic strain gauges, SOFO SMARTape Compact deformation sensors, were used for determining the deflection of the sandwich composite structure. Experimentally obtained data were used for comparison with theoretical models – sandwich theory with the transverse shear, sandwich theory without the transverse shear, laminate theory with the transverse shear and laminate theory without the transverse shear.

The paper presents the results of an experimental research and a numerical calculation of a multi-gap seal of a centrifugal pump. The experimental research allowed to obtain the characteristics? performance of the multi-gap seal at different operating modes, in dependence on the axial size of the chambers, pressure distributions? changes, and a leakage from the seal. Using finite volume methods, values of radial hydrostatic forces, pressure distribu-tions and leakage values were obtained. The results of the numerical calculation were compared with the results of the experiment, which showed that they matched.

The given paper deals with the wear of the tensioner which is produced from aluminium alloy and used of the motorcycle timing chain. This component was made due to the unavailability on the spare parts market. The AlMgSi1 alloy was chosen for this purpose, taking into account the requirements for producing of the tensioner. After production, the tensioner was put into operation where its functionality was regularly controlled. The suitability of the selected material was checked after the tensioner was removed. Possible damages and structural changes in the material were assessed using a scanning thermoemission electron microscope. Detection of the chemical composition of foreign particles trapped on the surface of the tensioner from engine oil during the operation was performed by EDS analysis.