Abstract: AA 2024 alloy is widely used as a structural material in aerospace applications. Its excellent strength to weight ratio makes it suitable for the subsequent application. The aerospace application required close tolerances and accuracy in the machined parts. Henceforth non-conventional machining processes are widely used for different machining operations such as drilling through holes. In the present study, Electrical Discharge Machining (EDM) process is used to drill through holes in 5mm thick AA 2024 alloy material. With the aim of reducing the difference between finished diameter of drilled hole and intended diameter, computational technologies were adopted for optimization. Mathematical models were developed using Response Surface methodology (RSM), and subsequently Genetic Algorithm (GA) was used to reach a set of input parameters in order to give minimum difference in diameter. Three input parameters such as current (I), Pulse on time (Ton) and Pulse off time (Toff) were selected. The ANOVA results indicated that developed models were adequate and robust. The GA based approach in conjugation with RSM was able to locate a single set of parameters which gave minimum difference in diameter. Confirmation test was again carried out and the difference between predicted and measured value was negligible.
Abstract: Corrosion can lead to failures in plant infrastructure and machines which are usually costly to repair, contaminating the product and causes environmental damage. Green inhibitor is a corrosion inhibitor which normally comes from the extract of plants and can inhibit corrosion by using chemisorption and/or physisorption mechanism on the metal surface or reacting with metal ions and forming a barrier-type precipitate on its surface. This paper discusses the corrosion inhibition of low carbon steel by addition of palm oil and corn oil as green inhibitors. We also compared the effect of these inhibitors in water and salt water environment. The corrosion behaviour of the low carbon steel was determined by immersion and electrochemical tests. The immersion test was carried out by immersing the samples in distilled water and 3.5% NaCl solution with and without the inhibitors for 1,2,4,6 and 8 weeks. The concentration of the inhibitors used was 100 g/L for both corn oil and palm oil. Scanning Electron Microscopy, Energy Dispersive Spectroscopy and X-Ray diffractometer were used to analyse the results. Immersion test results show that there is a slight weight gain for low carbon steel immersed in the presence of inhibitors suggesting that there is a thin protective layer formed which act as a barrier towards corrosion. Corn oil inhibitor in distilled water shows the highest inhibition efficiency. Its inhibition efficiency is 93.9%, which is slightly higher than palm oil (91.5%) in similar environment.
Abstract: Al addition in TWIP steel not only reduces the specific weight but also increases the stacking fault energy which strongly affects the deformation mechanisms. Hot rolled air cooled TWIP steel with low Al content (1.61 wt. %) reveals duplex microstructure comprising austenite with ferrite, whereas steel with higher content of Al (3.56 wt. %) reveals fully austenite microstructure. It is evident that nano-twins are formed within austenite grain after 50% cold deformation. TWIP steel with the duplex microstructure exhibits an excellent combination of strength and ductility. Hardness and tensile strength values of air cooled steel specimens increase with a concomitant lowering of total elongation with the application of cold deformation. However, steel with low Al content shows higher hardness and tensile strength along with lower elongation as compared to the TWIP steel having higher Al content.
Abstract: Here, we report the mechanical behaviour of open-cell foams of 6061-T6 Al-alloys under quasi-static loading. The foams were processed by pressurized salt infiltration technique with efficient control over pore size and distribution. Spherical salt beads of NaCl of required size distribution were used as preforms. The molten alloy was infiltrated into the preforms under an inert gas pressure of 2 bar followed by cooling and leaching of the salt pattern in a suitable aqueous medium. The pressurized infiltration process is convenient to overcome the capillary forces arising from the non-wetting conditions between salt beads and molten alloys and offers a versatile and economical route for the production of open-cell foams. The shape, size and distribution of the pores were studied with optical microscope and X-ray computed tomography (X-ray CT). The developed foam samples were cut into required dimensions following ASTM E9-09 standard and their mechanical properties were analyzed under quasi-static compressive loading.
Abstract: The development of postmodern theory, are based on contemporary cultural thought and practice. That is; the eclectic mixture of any tradition with that of its immediate. Thus, Postmodernists artists have shown the taste for hybrids, which involves conjoining two different techniques or cultures across the units of time, background and place. This conjunction or creative binding (hybrid) enables the appreciation of both sides of the equation and their union. Therefore, this study employed a deductive and practice-led approach to determine how viable rapid prototyping technology can improve the production process. However, in order to avoid outright elimination of the artisanal skills, the study examines the viability of integrating the conventional skill and modern technology as hybrid technique. The findings from the study revealed that the integration of rapid prototyping and hand-turning (conventional technique) is a viable hybrid production technique that can reduce the development time drastically, enhance product quality and reduce the development cost reasonably in ceramic production.
Abstract: The effects of adding Al2O3 and CeO2 on the microstructure, mechanical and physical properties of 3 mol% yttria-stabilized zirconia (3Y-TZP) ceramics is presented over a wide sintering regime by pressureless sintering. It has been revealed that small additions of dopant to Y-TZP were beneficial in enhancing the mechanical properties of Y-TZP. Sintered samples were used to evaluate the bulk density, Vickers’s hardness, Young’s modulus, and shrinkage of the material. Al2O3 and CeO2 doped Y-TZPs sintered at 1450∘ C retained high bulk density (>97% of theoretical density) and Young’s modulus (>200 GPa) without sacrificing tetragonal phase stability. The optimum level of dopant was found to be at 0.3 Al2O3 / 0.5 CeO2 at sintering temperature between 1250∘ C and 1450∘C using the standard 12 min holding time cycle, with sintered body exhibiting excellent combination of properties when compared to the undoped ceramics.
Abstract: The effect of manganese oxide (MnO2) and aluminum oxide (Al2O3) addition of up to 1 wt% in yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), sintered in air at 1450oC, was examined. The low temperature degradation resistance was observed by immersing the sample in Ringer solution at 37oC over a period of 8 weeks, whereby the weight loss and the SEM image of sample was analyzed to generate the degradation pattern of the sample. Additions of 0.6wt% Al2O3/ 0.4wt% MnO2 were found to be beneficial in retarding the ageing of the ceramics sample. Therefore the sample was deemed beneficial in the use of orthopedic applications.
Abstract: Neutron bombardment on semiconductor material causes defects, one such primary physical effect is the formation of displacement defects within the crystal lattice structure, and such defects effectively decrease the mean free path and thus shorten the recombination time. Ionizing radiation causes creation of electron-hole pair in the gate oxide and in parasitic insulating layers of the MOS devices. Calculations show increase of the dark current in depletion region caused by a single neutron. Determination of energy and angular distribution of primary knock on atoms, with 14 MeV neutron irradiation in silicon are presented.
Abstract: Crystalline silicon and amorphous silicon are main materials of solar cell. Under prolonged exposure to light, silicon will degrade in quality. Hydrogenation is believed can minimize this degradation by reduce the number of dangling bond. These Molecular dynamics simulations are aimed to elaborate the hydrogenation process of crystalline silicon and amorphous silicon and to elucidate effect of temperature on distribution of hydrogen atoms. Reactive Force Field is selected owing to its capability to describe forming and breaking of atomic bonds as well as charge transfer. Hydrogenation is performed at 300 K, 600 K, 900 K, and 1200 K. Hydrogenated silicon surface hinders further hydrogen atoms to be absorbed such that not all deposited Hydrogen atoms are absorbed by silicon surface. Generally, the higher hydrogenation temperature the more hydrogen atoms are absorbed. Increment of temperature from 900 K to 1200 K only enhances a few numbers of absorbed hydrogen atoms. However, it can enable hydrogen atoms to penetrate into deeper silicon substrate. It is also observed that hydrogen atoms can penetrate into amorphous silicon deeper than into crystalline silicon.