@article {3804, title = {Analysis of the machinability of different types of sintered carbides with WEDM in both water and oil baths}, journal = {The International Journal of Advanced Manufacturing Technology}, year = {2023}, abstract = {

The unconventional wire electric discharge machining (WEDM) technology represents a vital manufacturing technology in different industrial branches. This technology is essential because of the possibility to machine difficult-to-machine materials such as sintered carbides. For this reason, this study analyses the machinability of sintered carbides WKP23S, WSM33S and WK1 with WEDM in both water and oil baths. We investigated the influence of the machining parameters, namely, pulse off time, gap voltage, discharge current, pulse on time and wire feed, on the cutting speed, surface roughness and defect occurrence. We investigated 9 different roughness parameters, analysed surface morphology with an electron microscope and also analysed cross-sectioned samples. We found out that machining sintered carbides in oil bath yields better results than machining in deionized water. The oil tank prevents the removal of the cobalt binder, but it does not reduce fissure occurrence in any significant way. The lowest Ra value, that is 0.7 {\textmu}m, was recorded for the WKP23S sample when machined in oil and Ra 0.9 {\textmu}m when the same material was machined in water.

}, keywords = {AIF, MF}, issn = {1433-3015}, doi = {10.1007/s00170-023-10913-4}, url = {https://doi.org/10.1007/s00170-023-10913-4}, author = {Mouralova, Katerina and Benes, Libor and Prokes, Tomas and Zahradnicek, Radim and Fries, Jiri and Plichta, Tom{\'a}{\v s}} } @article {3796, title = {Rapid identification of pathogens in blood serum via Raman tweezers in combination with advanced processing methods}, journal = {Biomed. Opt. Express}, volume = {14}, year = {2023}, month = {Dec}, pages = {6410{\textendash}6421}, keywords = {AIF, BF, LF, MF}, doi = {10.1364/BOE.503628}, url = {https://opg.optica.org/boe/abstract.cfm?URI=boe-14-12-6410}, author = {Ond{\v r}ej Vacul{\'\i}k and Silvie Bernatov{\'a} and Katar{\'\i}na Rebro{\v s}ov{\'a} and Ota Samek and Luk{\'a}{\v s} {\v S}ilhan and Filip R{\r u} {\v z}i{\v c}ka and Mojm{\'\i}r {\v S}er{\'y} and Martin {\v S}iler and Jan Je{\v z} ek and Pavel Zem{\'a}nek} } @article {3803, title = {Stable a-CSi:H films with a wide range of modulus of elasticity and low internal stress}, journal = {Surface and Coatings Technology}, volume = {459}, year = {2023}, pages = {129147}, abstract = {

Amorphous hydrogenated silicon carbide (a-CSi:H) thin films were deposited by plasma-enhanced chemical vapor deposition using tetravinylsilane as organosilicon precursor. The mechanical properties of the thin films, namely the modulus of elasticity, hardness, and elastic recovery parameter, were determined by nanoindentation, as well as the internal stresses by scanning electron microscopy and optical profilometry. It was found that the modulus of elasticity increased from 10 to 137\ GPa with increasing power (2{\textendash}150\ W) delivered to plasma, while the hardness increased from 1.5 to 14.5\ GPa. This improvement in mechanical properties with increasing energy delivered to the plasma is related to greater fragmentation of the precursor which led to an increase in the crosslinking of the material network. The compressive internal stresses in the films reached low values of -0.04 to -0.2\ GPa with increasing power (2{\textendash}75\ W) and an acceptable -0.5\ GPa for 150\ W. The elastic recovery parameter decreased with increasing power from 0.86 to 0.64, i.e., the thin films behaved more plasticity with increasing power. The modulus of elasticity and hardness were investigated in terms of the aging of the films for a period of 6\ years when samples were stored under ambient conditions. No significant changes in these properties were observed. However, minor changes were observed in the indentation curves obtained for the 2\ W and even less for the 10\ W samples. Small changes were then also observed for the elastic recovery parameter, whose value for these samples partially decreased which may be related to postdeposition oxidation. No changes in internal stress values over time were observed. The wide range of mechanical properties of stable a-CSi:H films with low internal stress increases their application potential and their wide use as materials with tailored properties from polymer-like to tough material.

}, keywords = {AIF, MF}, issn = {0257-8972}, doi = {https://doi.org/10.1016/j.surfcoat.2022.129147}, url = {https://www.sciencedirect.com/science/article/pii/S0257897222010684}, author = {Tomas Plichta and Vaclav Sulc and Miloslav Ohlidal and Vladimir Cech} } @article {3628, title = {Experimental analysis of microhardness changes of subsurface areas affected by WEDM}, journal = {Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering}, volume = {236}, year = {2022}, pages = {1979-1991}, abstract = {

The influence of the surface area by the impact of high temperatures after wire electric discharge machining (WEDM) is a known fact. However, the affected parameters also include a change in microhardness. In order to further investigate this statement, 5 different ferrous and non-ferrous materials were selected, from which three samples were always made with different settings of machine parameters (gap voltage, pulse on and off time, wire feed and discharge current). This examined not only the effect of the machining itself on the material but also whether the change in the microhardness of the material is affected by the setting of the machine parameters. In order to measure the microhardness of the subsurface layer, a metallographic preparation was made from each sample, which enabled accurate measurements always in the same area. Subsequent evaluation revealed that the microhardness may not be affected at all and everything depends only on the type of material being machined. The changes in microhardness affected by setting machine parameters are negligible.

}, keywords = {AIF, MF}, doi = {10.1177/09544089221078383}, url = {https://doi.org/10.1177/09544089221078383}, author = {Katerina Mouralova and Stefan Michna and Radim Zahradnicek and Josef Bednar and Tomas Plichta and Jiri Fries} } @article {3629, title = {Production of precision slots in copper foil using micro EDM}, journal = {Scientific Reports}, volume = {12}, year = {2022}, month = {MAR 23}, pages = {5023}, keywords = {AIF, MF}, issn = {2045-2322}, doi = {10.1038/s41598-022-08957-9}, author = {Mouralova, Katerina and Bednar, Josef and Benes, Libor and Plichta, Tom{\'a}{\v s} and Prokes, Tomas and Fries, Jiri} } @article {3630, title = {Surface topography affects the nanoindentation data}, journal = {Thin Solid Films}, volume = {745}, year = {2022}, pages = {139105}, abstract = {

The near-surface mechanical properties of thin films as well as bulk materials are amongst the key parameters important for their application, and instrumented nanoindentation is a standard technique for determining these mechanical properties. However, it is known that the surface topography of the characterized materials may affect the nanoindentation data when a sharp indenter for small penetration depths (displacements) is used. A thin film of hydrogenated amorphous silicon carbide with a thickness of 1.0\ μm was deposited on a silicon wafer by plasma-enhanced chemical vapour deposition. The cyclic nanoindentation was used to construct a depth profile of mechanical properties for the flat surface (0.5\ nm roughness) of the thin film, which made it possible to determine its modulus of elasticity of 83\ GPa and hardness of 8.6\ GPa unaffected by the silicon substrate. Grains with a spherical cap geometry with a typical radius of 0.5\ {\textmu}m and a\ height of 60\ nm are distributed along the flat surface of the film. The grains have the same mechanical properties as the deposited film. Depth profiles of mechanical properties were determined for different types of contact between the Berkovich indenter with a radius of 50\ nm and the selected grain (grain top, grain foot, two or three grains); i.e. for these measurements the following applied - the radius of the tip curvature was less than grain radii (RBerkovich \< Rgrain). Residual imprints after nanoindentation measurements were carefully observed by atomic force microscopy and scanning electron microscopy. The near-surface mechanical properties were significantly affected by the surface topography, and the determined modulus of elasticity and hardness were crucially under- or overestimated in the range of 50\% to 100\% compared to the real values. The nature of these deviations was discussed. The solution is to use cyclic nanoindentation performed on the flat surfaces or on the top of grains, followed by extrapolation of the depth profiles to the zero-contact depth (film surface).

}, keywords = {AIF, MF}, issn = {0040-6090}, doi = {https://doi.org/10.1016/j.tsf.2022.139105}, url = {https://www.sciencedirect.com/science/article/pii/S0040609022000268}, author = {Tomas Plichta and Radim Zahradnicek and Vladimir Cech} } @article {3486, title = {The Adhesion of Plasma Nanocoatings Controls the Shear Properties of GF/Polyester Composite}, journal = {Polymers}, volume = {13}, year = {2021}, pages = {593}, abstract = {

High-performance fibre-reinforced polymer composites are important construction materials based not only on the specific properties of the reinforcing fibres and the flexible polymer matrix but also on the compatible properties of the composite interphase. First, oxygen-free (a-CSi:H) and oxygen-binding (a-CSiO:H) plasma nanocoatings of different mechanical and tribological properties were deposited on planar silicon dioxide substrates that closely mimic E-glass. The nanoscratch test was used to characterize the nanocoating adhesion expressed in terms of critical normal load and work of adhesion. Next, the same nanocoatings were deposited on E-glass fibres, which were used as reinforcements in the polyester composite to affect its interphase properties. The shear properties of the polymer composite were characterized by macro- and micromechanical tests, namely a short beam shear test to determine the short-beam strength and a single fibre push-out test to determine the interfacial shear strength. The results of the polymer composites showed a strong correlation between the short-beam strength and the interfacial shear strength, proving that both tests are sensitive to changes in fibre-matrix adhesion due to different surface modifications of glass fibres (GF). Finally, a strong correlation between the shear properties of the GF/polyester composite and the adhesion of the plasma nanocoating expressed through the work of adhesion was demonstrated. Thus, increasing the work of adhesion of plasma nanocoatings from 0.8 to 1.5 mJ{\textperiodcentered}m-2 increased the short-beam strength from 23.1 to 45.2 MPa. The results confirmed that the work of adhesion is a more suitable parameter in characterising the level of nanocoating adhesion in comparison with the critical normal load.

}, keywords = {AIF, MF}, issn = {2073-4360}, doi = {10.3390/polym13040593}, url = {https://www.mdpi.com/2073-4360/13/4/593}, author = {Plichta, Tom{\'a}{\v s} and {\v S}irjovov{\'a}, Veronika and Zvonek, Milan and Kalinka, Gerhard and {\v C}ech, Vladim{\'\i}r} }