The paper analyses deformation and heat flow aspects of chip formation in grinding process by developed unique quick stop method and properties of ground surfaces, mainly micro-hardness. The cutting ...speed of the grinding process is within the range of high-speed turning and milling, so the chip formation is characterized by a high contact temperature and intensive plastic deformation. Moreover, the grinding wheel is a cutting tool of undefined geometry and the dimensions of grinding grains are several orders lower in comparison with the defined geometry cutting tools. The mentioned features make the research of the grinding process very specific. The paper provides the obtained micro-section of the chip forming process and the special chip shapes obtained by quick stop method in the grinding process. Furthermore, the paper analyses the special properties of the ground surface and even subsurface layers through the micro-hardness analysis, discusses performance in subsequent operating conditions and subsequent grinding of that layers. The experiments were carried out for the steel workpieces, ceramics grinding wheels and grinding without cooling.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The present work contributes to the research on the damping properties of fibre composites through an experimental approach by using the free damped vibration measurement based on impulse-force ...system response, the developed measurement stand and laser Doppler vibrometry. Moreover, the influence of the material configuration on the damping properties was investigated and was compared with conventional homogeneous isotropic materials. The measurement was based on the analysis of flexural vibrations generated by the Dirac impulse force, as well as on the free decaying-vibrations response; the time- and frequency-domain modal identification was employed. The fibre composites were represented as layered bidirectional long carbon- and glass-fibre composites (laminates) with different material configurations and as short carbon-fibre composites.
This paper presents the prototype design, implementation and testing of a thermoelectric generator unusually applied to the fireplace stoves. The tested low-cost thermoelectric generator can be used ...as an alternative low source of electricity in areas with limited access to public electricity networks. Moreover, inclusion of a thermoelectric generator in the fireplace stove structure is novelty and interesting accessory in offer for customer. This study focuses on testing and determining the output values of voltage and current of the initial design using the natural and forces air cooling. The results are obtained by developed measuring device for that testing. The low-cost thermoelectric generator provided the power of 1.5 W at temperature difference 94°C using forced air cooling. Thus a thermoelectric generator prototype design is suitable for powering LED lighting and fans or recharging a mobile phone battery.
The paper analyzes static stiffness of technological system machine tool - cutting tool - workpiece as one of factors affecting machined part accuracy. It focuses on turning and milling and their ...tool and workpiece characteristics as size, geometry, stiffness, tool wear, clamping etc. The paper identifies inaccuracies as a result of deformation of elastic component joints during acting the cutting and clamping forces. The paper provides final shapes and its deviations from ideal shape. The analysed results are obtained either by numerical simulation or by experiment. Finding the deviations generating mechanisms, it is possible to link dimensional, geometric and surface accuracy of workpiece to specific elements of technological system that is the significant point of the machine and tool design.
The paper presents the analysis of the material configuration of composites based on the measurement of their dynamic response. The article presents the measurement scheme, the design of the ...measuring stand together with the analysis of the results. Moreover, it analyses the FFT spectrums of layered long fibre composite, short fibre composites of different fibres materials and homogeneous materials as steel and aluminium alloy.
The presented article investigates the biomechanics of the calcaneal nail C-NAILTM by numerical calculations and, partially, experimentally. This nail is widely used in trauma and orthopaedics. A ...numerical model of implants directly interacting with the bone tissue model obtained from CT scans was calculated. The material properties of the bone tissue can be described by several models; in this work, a non-homogeneous material model with isotropic elements and prescribed elastic modulus was used to provide a more accurate model of the applied force distribution on the individual parts of the implants. The critical areas of the nail and its fixtures were investigated using finite element strength calculations to verify their strength and reliability, contributing to the safety and faster and easier treatment of patients. These analyses suggest that the strength of the calcaneal nail C-NAIL, as well as the stabilization of bone fragments resulting from its use, are sufficient for clinical practice.
The present study deals with the harmful torsional resonance vibrations of textile rotor bearings, the amplitudes of which are reduced mainly by the use of high-capacity damping materials, ...characterized by an internal hierarchical structure and macroshape, added into the machine mechanical system. The additional materials are polymer matrix composites reinforced either by carbon nanofibers or carbon chopped microfibers and either aramid or carbon continuous fibers. The macroshape is based on a honeycomb with internal cavities. Torsional vibrations arise in mechanical systems as a result of fluctuations in the low-level pressing load of the flat belt driving the rotor-bearing pin and the changing of kinematic conditions within it, which, in the resonance area, leads to cage slip and unwanted impulsive torsional vibrations. Moreover, this occurs during high-frequency performance at around 2100 Hz, i.e., 126,000 min
. The condition, before the redesign, was characterized by significantly reduced textile rotor-bearing life due to significant impulse torsional vibrations in the resonance area. The study showed a significant reduction in average and maximum torsional amplitudes in the resonance area by 33% and 43%, respectively. Furthermore, the paper provides visualization of the propagation of a stress wave at the microscale obtained by the explicit finite element method to show the dispersion of the wave and the fibers as one of the sources of high damping.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this paper, we present an extensive experimental study on the dynamic mechanical properties of composites with polymer matrices, as well as a quantification of the parameters that influence these ...properties. Polymer-composite matrices make it possible to form any reinforcement arrangement of fibres, particles, and layers, which makes it possible to form composite materials with certain dominant mechanical properties according to the internal arrangement for the application. In this study, we focused on the dynamic properties (i.e., damping parameters, such as the loss factor (tan d), logarithmic decrement (λ), storage modulus (E′), and loss modulus (E″)) of composites with polymer matrices, including parameters such as the fibre material, fabric weaving, fibre orientation, temperature, frequency, particle size, volume of short fibres, and epoxy resin type. If other articles focus on one type of composite and 1–2 parameters, then the benefit of this article lies in our analysis of 8 mentioned parameters in the experimental analysis of 27 different types of composites with polymer matrices. The tested fibre materials were glass, aramid, and carbon; the tested woven fabrics were twill, plain, unidirectional, and satin; the temperature range was from −50 to +230 °C; the frequency was 1 Hz and 10 Hz; the particle size was 0.1–16 mm; the volume percentages of the short fibres were 3, 6, and 12 vol.% of the hybrid polymer composites and the type of polymer matrix. We used the free-damped-vibration method with vibration dynamic signal analysis and the forced-damped vibration of dynamic mechanical thermal analysis for testing. We ranked the parameters that influence the dynamic vibration properties according to the effects. Among sets of results provided in the paper, considering the storage modulus, loss modulus, and loss factor, the best results of the fibre composites were for aramid-fibre-reinforced polymers, regardless of the weave type, with an advantage for unidirectional fabric. The best results of the particle composites were for those with fine filler sizes that incorporated the short fibres.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The time taken to exchange a cutting tool and the actual machining time are the components in a total production cycle time for a part, that affects productivity. Automated plate exchange systems ...strive for the simplest possible principles to achieve the shortest possible tool exchange time with sufficient accuracy. The tool holder in the presented article is based on the principle of a combination of translational, rotational movement, and stop surfaces by using a single pull–push rod for simple control. The article provides alternative tool holder designs and turning results of such holders using Rz-f dependence. The results of the time reduction are satisfactory and give a prerequisite for using a tool holder for the automated exchange of triangular cutting inserts. Moreover, the article provides the approach to reduce the mentioned total production cycle time by a reduction in the actual machining time for a part by use of tooltip radii, not by increasing the cutting speed. The triangular cutting insert can have three tooltips of three different tooltip radii for roughing and finishing. In addition, for reduction of the actual machining time, the double cutting tool with both the small tooltip radius for rouging and the large tooltip radius for finishing is presented. The double tool holders showed a 2.4-times reduction in the actual machining time for a part with Rz = 20 µm.
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