Cast iron and mineral cast are the materials most often used in the machine structural elements design (bodies, housings, machine tools beds etc.). The materials significantly differ in physical and mechanical properties. The ability to suppress vibration is one of the most important factors determining the dynamic properties of the machine and has a significant impact on the machining capabilities of a machine tool. Recent research and development trends show that there is a clear tendency to move away from the traditional iron casting to the mineral casting, due to better dynamic properties of the latter. However mineral cast as a structural material for the whole machine tools bed turns out to be insufficient due to its poor mechanical strength properties. The best solution should benefit from the advantages of the cast iron and mineral cast materials while minimizing their drawbacks. The paper presents numerical modal analysis of two lathe beds: the first one made of gray cast iron and the second one made of hybrid connection of cast iron and mineral cast. The analysis was conducted in order to determine the dynamic properties of two bodies of similar shapes made in the traditional (cast iron) and innovative hybrid (cast iron and mineral cast) technology. In addition, an analysis of the static structure rigidity of the two beds was performed. During the simulation studies it was found a significant increase in dynamic stiffness and static rigidity of the machine tool body made of hybrid connection of cast iron and mineral cast. The results of numerical simulations have confirmed the desirability of using hybrid construction because the dynamic properties of such a body are more advantageous in comparison with the conventional body made of cast iron.Keywords: cast iron, mineral cast, dynamic properties, modal analysis, machine tool bed Żeliwo oraz odlewy mineralne są materiałami konstrukcyjnymi najczęściej wykorzystywanymi w dziedzinie projektowania elementów strukturalnych maszyn (korpusy, obudowy, łoża obrabiarek). Te materiały znacząco różnią się pod względem zarówno właściwości fizycznych, jak i mechanicznych. Zdolność do tłumienia drgań jest jednym z najważniejszych czynników determinujących właściwości dynamiczne urządzenia i ma znaczący wpływ na możliwości obróbkowe maszyny technologicznej. Najnowsze badania oraz trendy rozwojowe pokazują, że istnieje wyraźna tendencja do odchodzenia od tradycyjnych odlewów żeliwnych w kierunku odlewów mineralnych, ze względu na lepsze właściwości dynamicznych tych ostatnich. Jednakże odlewy mineralne jako materiał konstrukcyjny na całe łoże obrabiarki okazuje się być niewystarczający ze względu na słabe właściwości mechaniczne. Najlepsze rozwiązanie powinno korzystać z zalet żeliwa i odlewów mineralnych, jednocześnie minimalizując wady obu materiałów. W artykule przedstawiono teoretyczną analizę modalną dwóch korpusów obrabiarki: jednego wykonanego z żeliwa szarego oraz drugiego wykonanego z hybrydowego połączenia żeliwa i odlewu mineralnego. Analiza została przeprowa...

The article presents the results of studies on the dynamics of wear of five different cutting inserts (for machining difficult-to-cut materials, for finishing cast iron machining, for roughing cast iron machining, for steel machining and for stainless steel machining) during turning a non-homogeneous material such as polymer concrete. Polymer concrete is a difficult-to-cut, anisotropic, composite material. During the tests, a record of the components of the cutting force in real time was made. After each machining pass, the Ra and Rz surface roughness values were measured in the direction perpendicular to the machining marks and photos were taken under the microscope of the inserts corners, on the basis of which the width of major flank wear land and the width of minor flank wear land were measured. The view of each insert after the tests was also presented. Finally, the conclusions about the dynamics of wear of inserts taking part in the study as well as their applicability during polymer concrete turning were formulated.

In this study, the influence of the addition of styrene-butadiene rubber on the dynamic properties of polymer concrete was investigated. A 10% volume addition of styrene-butadiene rubber granulate with three different grain gradations was used for the tests. The modal study was carried out in the 0 to 2000 Hz frequency range. The response function for a single impulse excitation was tested. The relaxation time after excitation, the modes of natural vibrations and the amplitude of the transfer function values as well as vibration damping ratios were also compared. Finally, conclusions were formulated regarding the application of the styrene-butadiene rubber additive as a material to improve the dynamic properties of polymer concrete. The best results were obtained for a sample made with a 10% styrene-butadiene rubber volume addition with grain sizes from 0.6 to 2 mm. In this case, the biggest decrease of the amplitude of the transfer function value was 76%, while the biggest increase of the damping ratio was 431.5%, in comparison with the clear polymer concrete sample. The worst results were obtained for a sample made with a 10% styrene-butadiene rubber volume addition with grain sizes from 2.5 to 6 mm. In this case, the longest relaxation time of the sample, the increase of the amplitude of the transfer function value and the decrease in the damping coefficient were recorded.

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This paper presents a model of surface grinding with superimposed oscillation of the workpiece. The parameters of the model were experimentally derived and the equations of motions of the system were solved using Matlab. The results obtained showed a significant decrease in the amplitude of the relative vibration between the wheel and workpiece when the oscillation was superimposed onto the feed motion of the workpiece. A range of experimental work was undertaken and the results showed that the vibratory process had a superior performance in absolute terms with reference to conventional grinding. Low forces along with longer tool life were recorded with the added vibration. A notion of dynamic relief was introduced to express the efficiency of the vibratory process.