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[en] The purpose of the current work is to analyse the effect of tilt angle and tool hardness on mechanical and microstructural characteristics of FSWed Al-Mg4.2 joints. The joints were fabricated varying the tilt angle and tool hardness at six different levels each, keeping other FSW parameters constant. Microstructure, macrostructure, strength and hardness characteristic of the welds has been sifted in order to understand the sensitivity of studied input variables on the joints quality. The outcome of the present investigation clearly indicates that the tilt angle and tool hardness notably affects the performance parameters of the FSWed joints. The paper suggests that 1°−3° tilt angle and 40–50 HRC tool hardness produces sound quality joints. The present work dredges a novel look on FSWed Al-Mg4.2 joints by dint of relating the macrostructure, microstructure and fractographs with the plasticized material movement in the process. (paper)
[en] Analytical formulas are obtained for the loading and unloading of topocomposites in tool indentation. On that basis, theoretical penetration diagrams are derived, for use in the creation of new tribological topocomposites.
[en] We report on the first analysis of an AstroSat observation of the Z-source GX 5–1 on 2017 February 26−27. The hardness-intensity plot reveals that the source traced out the horizontal and normal branches. The 0.8−20 keV spectra from simultaneous SXT and LAXPC data at different locations of the hardness-intensity plot can be described well by disk emission and a thermal Comptonized component. The ratio of the disk flux to the total flux, i.e., the disk flux ratio, increases monotonically along the horizontal branch to the normal one. Thus, the difference between the normal and horizontal branches is that in the normal branch, the disk dominates the flux while in the horizontal one it is the Comptonized component which dominates. The disk flux scales with the inner disk temperature as and not as , suggesting that either the inner radius changes dramatically or that the disk is irradiated by the thermal component changing its hardness factor. The power spectra reveal a quasi-periodic oscillation (QPO) whose frequency changes from ∼30 Hz to 50 Hz. The frequency is found to correlate well with the disk flux ratio. In the 3−20 keV LAXPC band, the r.m.s. of the QPO increases with energy (r.m.s. ), while the harder X-rays seem to lag the soft ones with a time-delay of milliseconds. The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component. (paper)
[en] Wear test results on commercial pure titanium (CP-Ti) indicated that despite the increase in hardness by 2.6 times after the surface mechanical attrition treatment (SMAT), wear properties of the treated samples were diminished. Samples embrittlement and wear rate increased over process time while hardness increased. In other words, wear properties depend on both hardness and toughness and simply improving hardness characteristic would not necessarily lead to optimized wear properties. Under low forces, abrasive wear with ploughing mechanism and adhesive wear were active. However, ploughing, plastic deformation and delamination became dominant wearing mechanisms under high forces. Delamination was actually responsible for harsher wearing of the treated samples in comparison with the untreated sample. (paper)
[en] For robust automatic measurement of Brinell hardness, we propose a novel measurement of the indentation diameter by using a convolutional neural network (CNN), which is a type of deep learning. In the Brinell hardness measurement, it is sometimes difficult to detect the indentation edges by image processing methods, due to the surface conditions or a change in the contrast with hardness levels. CNNs can automatically extract features required for object recognition of humans, hence we expect that the CNN can detect the indentation edges as robust as human operators, regardless of the surface conditions. We developed a CNN system to detect the indentation edges, and trained the CNN using the dataset combined with the indentation edge images and the position of edges given by a human operator. To verify the usefulness of the CNN method, we compared this method with measurement by a human operator and the region growing (RG) method, which is a simple region segmentation method in image processing. In the CNN method, indentation diameters and Brinell hardness were in good agreement with the manual measurement compared with the RG method, regardless of the hardness levels of test samples. Moreover, the CNN method enabled good measurement of a rough surface that is different from the dataset for training the CNN. Thus, our novel method is as robust as measurement by experienced operators and versatile in terms of independence of the hardness of samples or the characteristics of the surface conditions. (paper)
[en] This research synthesizes hydroxyapatite-calcium titanate composites (HA-CT) using conventional route technique. The synthesis procedure involves two steps: (i) synthesis nanoparticle of HA and the fine powder of CT and (ii) synthesis the HA-CT composites ceramic, respectively. The nanoparticle of HA was synthesized through the co-precipitation method with control pH at 8. The fine powder of CT was prepared by molten salt synthesis. The densification, phase formation, microstructure, and mechanical properties of the HA-CT composite samples were investigated. The decreasing decomposition of HA in HA-CT composites at high temperature sintering is related to the increase of CT content. The HA-CT composites showed improvement properties of densification, Vickers hardness, Knoop hardness and Young’s modulus with the maximum value as 91.20 GPa for CT 0.15 mol% in HA-CT samples. The fracture toughness resulted in data shown that the fracture toughness behavior of the HA-CT composites was controlled by the CT contents as well as grain size and porosity. The information of microstructures by SEM analysis indicated that the CT content produced a notable decrease in grain size of the HA-CT composites. (paper)
[en] This work aims to characterize the 36 NiCrMo 6 steel in monotic traction. The tested samples were subjected to mechanical surface treatment (MST) by diamond ball burnishing. This process allow it possible to modify the physical and geometrical properties of the material. The stress-strain diagram obtained were processed and digitalised. The hardening domain was modelled and rational curves were established, taking into account the stresses triaxiality. Thus, the work hardening exponent of material considered was evaluated. The effect of ball burnishing on this exponent has studied in proceeding a comparative manner between burnished and machined surface. The results obtained show that by applying the optimal parameters for burnishing, the work hardening exponent of pre-machined surface layer can be increased by 10%, where nB = 0.407 (nT = 0.312 machined surface). (paper)
[en] The first important limitation of ADI usage in industries is the machinability of the parts. Machinable Austempered Ductile Cast Iron (MADI) is a novel kind of ADI with improved properties such as better machinability compared to ADI and similar to as cast ductile iron. Furthermore, MADI has a higher strength than ductile iron at the same hardness value. The present work aimed to investigate into the impact of the austempering time and temperature on microstructure and mechanical properties of ductile iron samples prepared from Y-block with 75 mm thickness. In order to achieve the microstructure of the continuous matrix of equiaxed ferrite with islands of austenite, samples were partially austenitized (intercritical austenitization) at 850 °C for 2 hours. The austempering process was carried out at 350 °C and 390 °C for 1, 2, 3, 4 hours. The result of this study indicated that austempering at 390 °C, results in lower strength and hardness and higher ductility and toughness compared to austempering at 350 °C. It was also noticed that the minimum hardness was achieved by austempering at 390 °C for 2 hours. (paper)
[en] The effects of predeformation on the precipitation processes in a Cu-2.8 Ni-1.4 Si (at.%) alloy were studied using differential scanning calorimetric (DSC), transmission electron microscopy (TEM) and microhardness measurements. The calorimetric curves shows the presence of one exothermic reaction attributed to the formation of d-Ni2Si precipitates in the copper matrix that was confirmed by TEM. In addition it can be observed that the temperature of the maximum of the DSC peak decreases with the increase of the pre-deformation to the aging treatments. The activation energies calculated for the precipitation of d-Ni2Si, by the Kissinger method, were similar to those calculated by an Arrhenius function, from the maximum hardening of the matrix due to aging treatments (saturation of the hardness during isothermal aging). The analysis of the microhardness measurements together with the calorimetric curves and the TEM micrographs confirm, on the one hand, that the formation of the d-Ni2Si phase, during the aging treatments, are responsible for the hardening of the copper matrix, and on the other hand that the deformation prior to the aging treatment partially inhibits the formation of the precipitates.
[es]Los efectos de la deformación previa sobre los procesos de precipitación en una aleación de Cu-2,8 Ni-1,4 Si (at.%) fueron estudiados utilizando calorimetría diferencial de barrido (DSC), microscopía electrónica de transmisión (TEM) y medidas de microdureza. Las curvas calorimétricas muestran la presencia de una reacción exotérmica atribuido a la formación de precipitados de δ-Ni2Si en la matriz de cobre, lo cual fue confirmado mediante TEM. Además, sse puede observar que la temperatura del máximo del pico de DSC decrece con el aumento de la deformación previa a los tratamientos de envejecimiento. Las energías de activación calculadas para la precipitación de δ-Ni2Si, mediante el método de Kissinger, resultaron similares a aquellas calculadas mediante una función de Arrhenius, a partir del máximo de endurecimiento de la matriz debido al tratamiento de envejecimiento (saturación de la dureza durante el envejecimiento isotérmico). El análisis de las medidas de microdureza en conjunto con las curvas calorimétricas y las micrografías TEM permiten corroborar, por una parte que la formación de la fase δ-Ni2Si, durante los tratamientos de envejecimiento, son los responsables del endurecimiento de la matriz de cobre, y por otra que la deformación previa al tratamiento de envejecimiento inhibe parcialmente la formación de los precipitados.
[en] The Structural Concrete Spanish Code (EHE-08) set up the basis to select the most appropriate materials and concrete composition for structural purposes. Given that, the material designers have a really good tool to achieve the designing of strong and safe structures over time . Therefore, the projected service life would be guaranteed by using such Code. In particular, a series of specifications are provided for the cement, aggregates, water, additives and so on, to produce strong and durable concrete. The EHE-08 also contains a series of requirements specifically concerning the building materials, exposition environment, calculation methodology, and materials characterization. It is the inadequacy of Annex 9 th of the Structural Concrete Spanish Code (EHE-08) in technical terms that has been increasingly debated and criticized (Figure 1). The aim of this paper is to assess the application of Annex 9 th in some coastal buildings