Results 1 - 10 of 1316
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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] A method is proposed for calculating the actual contact area in a pressure coupling between components of different hardness. The reduced plastic hardness of the components is discussed.
[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 paper presents a first-order austenitization kinetics model for 22MnB5 steel, commonly used in hot forming die quenching. Model parameters are derived from constant heating rate dilatometry measurements. Vickers hardness measurements made on coupons that were quenched at intermediate stages of the process were used to verify the model, and the Ac1 and Ac3 temperatures inferred from dilatometry are consistent with correlations found in the literature. The austenitization model was extended to consider non-constant heating rates typical of industrial furnaces and again showed reasonable agreement between predictions and measurements. Finally, the model is used to predict latent heat evolution during industrial heating and is shown to be consistent with values inferred from thermocouple measurements of furnace-heated 22MnB5 coupons reported in the literature.
[en] In this study, β-Si3(Cx,N1−x)4 Silicon Carbonitride was prepared by Self-Propagation High-Temperature Synthesis (SHS). And the influence of carbon on structure stability, mechanical and tribological properties of β-Si3(Cx,N1−x)4 were investigated. The results showed that the solubility of carbon in β-Si3(Cx,N1−x)4 was about 10 wt%, beyond which cubic-SiC segregated out of β-Si3(Cx,N1−x)4 to form β-Si3N4/cubic-SiC composite. Regarding influences of carbon concentration on mechanical properties, the hardness of β-Si3(Cx,N1−x)4 decreased from 1400 Hv to 1200 Hv with the increase of carbon concentration. Whereas, the fracture toughness of β-Si3(Cx,N1−x)4 increased from 6.5 MPa · m0.5 to 7.6 MPa · m0.5 with the increase of carbon concentration. The tribological property studies revealed the anti-wear performance of β-Si3(Cx,N1−x)4 was enhanced by the increase of carbon concentration. The dominated wear mechanism could be attributed to the abrasive wear by fracture. (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)