Key Engineering Materials Vol. 952

Abstract: The results of research into new materials are increasingly pushing the boundaries of science and technology. For some of the materials, such as polymers, composites and nanomaterials, new knowledge is expected in the future. However, new knowledge is also being gained in the case of metal alloys, which were considered to have been fully investigated. Thus, in 2018, new knowledge emerged about materials that are believed to be able to significantly influence many areas of modern society. They include seven completely different materials such as polymers, nanocomposites, and metal alloys. The materials are Wood Sponge – the greener way to clean up oceans; the strongest bio-material – stronger than steel and its biodegradable; self-healing material – it does it without external stimulant; Platinum Gold Alloy – matching Diamond in wear resistance; Silicon X – better than the original; Indefinitely recyclable plastics – making a case for the future of plastics; and Glass coating that can block sunlight. In this paper, an overview of knowledge about them is given, and their application characteristics are highlighted.

Abstract: 100Cr6 is a steel used both for bearings and for certain components that need precise hardness and stability of properties over time. The paper proposes the analysis of the heat treatment applied to the 100Cr6 steel in order to obtain the imposed hardness in the range of 450-550 HV_0.1, within very tight tolerances.

Abstract: Nanocrystalline materials have different properties compared to materials with microcrystalline grains. Nanocomposites, as a subdivision of nanomaterials, have different magnetic properties for each individual constituent. In the paper, a series of nanocomposite materials from the sphere of W ferrites are developed by mechanical grinding. Mixtures of commercial BaO and α-Fe₂O₃ powders, in the micron range, were used. The commercial powders were mechanically ground in order to reach the nanometric range. The use of suitable grinding parameters for ceramic powders led to the discovery of the nanometric range in a not very long time. An important parameter, which was used in the current research, was wet grinding which is a more suitable method for obtaining finer powders than dry grinding. Dividing the materials as finely as possible ensures a better reactivity due to the free valences of the ions on the surface of the granules and due to the fact that the number of contact points and the contact surface are much larger than in coarse-grained materials. The powders were unilaterally compacted, using a cylindrical die with an inner diameter of 15 mm. A resistive heating device was designed and built in order to assure the sintering process of the samples. Before resistive sintering, a thermal simulation of the heating process was carried out to see the distribution of the thermal field in the samples at different temperatures. According to the simulation, the optimal heating temperature was chosen. The sintered samples were analyzed from the point of view of the magnetic properties and it was found that the samples with the granulation in the nanometric range have higher magnetic characteristics than those in the micron range.

Abstract: The paper considers the issue of the influence of ambient temperature and service life on the endurance of pipe steels of underground pipelines. The results of numerous experimental studies allowed us to draw the following conclusions. An analysis of the experimental data indicates that for all the studied steels, the endurance decreases with decreasing air temperature, mainly down to-20... -30 °C. This can be explained by the embrittlement of the metal, i.e. a decrease in the plastic properties of the pipeline metal structure. In addition, it can be seen from the given data that low-alloy steels 48KhN, 09G2S, 10GS have the highest endurance. Weak endurance is mainly typical of grade 20 carbon steel. Experimental studies show that with an increase in the service life of pipes, their endurance decreases, and this tendency is inherent in all the studied steels. Studies of the endurance of pipe steels under complex stress states show that static torsional stresses close to the yield strength, when tested in the air, do not reduce fatigue life. Although the corrosive environment significantly reduces the cyclic strength of steel under shear stresses up to τ_cr=05τ_Y, the conditional limit of corrosion fatigue is not lower than when tested for corrosion fatigue under the action of only alternating stresses in a symmetrical cycle. It could be considered that the torsional stress in the pipeline system does not exceed 10 MPa. In that case, their influence on practical calculations on the endurance of pipes of underground pipeline systems can be neglected.

Abstract: The dealloying technique has been a well-known process since antiquity, but recently it has started to be used to produce nonporous metals and metal oxide semiconductors for various electrochemical applications. The dealloying process is carried out in both acidic and basic solutions, depending on the base material and the desired application. In this study, Cu-based amorphous ribbons were dealloyed in alkaline aqueous solution at room temperature, keeping the temperature constant and varying the concentration of the solution. This process has the advantage that both dealloying of the ribbons and nanostructured copper oxide synthesis on their surface is obtained in one step. For the preparation of copper-based amorphous ribbons, the melt-spinning process was used, and the composite obtained consisting of nanopores decorated with Cu₂O/CuO nanoparticles makes it an ideal candidate for electrochemical applications. For the investigation of the structural, morphological, and optical properties of the obtained materials, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Abstract: The work is mainly aimed at solving technical problems in the field of unconventional fluid-jet processing, a field in which ISIM Timisoara has developed technical and technological expertise. A crucial part of an effective cleanup process is the secure transportation and disposal of sludge-type materials and related clean-up waste in the industry to a designated site and then to waste treatment plants, as ecological regulations continue to evolve. As a result, experts strive to discover the most state of the art and effective methods for storing and cleaning produced waste.The technical solution studied in this paper consists in obtaining an efficient system for the evacuation of the waste water and abrasive mixture, elements generated during abrasive waterjet cutting, in the shortest time, without stopping the technological cutting process.In this sense, a water eductor system is studied, by carrying out a preliminary experimental program, for use in abrasive waterjet installations collector tanks, by CFD simulation process.The operating parameters of eductor-type mixing nozzles and their effect on the liquid abrasive mixture in a tank of an abrasive-water jet cutting system were analysed.

Abstract: The paper deals with research on a hybrid technique of coating by Electrical Discharge Deposition (EDD) which has the advantage of lower costs than the other similar methods. This is due to the possibility of using a usual electrical discharge machine, with common tooling, aided by electromagnetic coils that increase the precision and the quality of deposed layers. Some metallic materials like W, Al, Ni, and Ti of high purity are used for EDD, which could be taken from available wires providers. Numerical simulation of the EDD process, using the metals mentioned above was achieved in Comsol Multiphysics. Two connected modules (physics) were used: Magnetic Fields that produced the magnetic force that actuated each of these four categories of ions and Charged Particle Tracing that highlighted the distribution of particles on different cut planes – Poincare maps. Based on these results provided by numerical simulation, it was possible to evaluate the ions behavior, in comparison to electrons, during EDD that is influenced by their atomic mass and the charge number.

Abstract: The reliable operation of an engineering structure is highly influenced by the joints of its structural elements. The selection of the applied joints is often determined by the function of the structure. In addition, the requirements for joints must be considered: strength, elongation, sealing, mobility, assembly, safety against loosening, feasibility, economy, design, etc. of the joint. The range of sheet materials used in the vehicle industry is very broad: manufacturers can choose the most suitable materials for a given purpose from a wide selection of materials, and it is also common to use sheets of several types of materials, with different thicknesses and physical and chemical properties, within a structural element. However, these sheets need to be combined in some way to produce a proper final product design. For combining thin sheet material, several different joining technologies are known. The aim of the study is the examination of clinched joints made of aluminium due to the highly increasing percentage of aluminium sheet usage in car bodies. The applied materials are EN AW 5754 and EN AW-1050 with different thicknesses. The joints were analysed by FEA and experimentally tested as well.

Abstract: Machining of difficult-to-process materials, including composite materials, is carried out in cost-effective conditions by resorting to abrasive water jet cutting. The quality of the kerf depends on a large number of input parameters, so that their selection becomes a current problem of real technological interest. Thus, the paper analyzes the cut zones defined by the material removal mechanisms, regarding both their extension and the obtained roughness, through the experimental modeling of the Rz parameter.