Search

In the present study, the grain refinement effects of carbon on AZ 81 (Mg–8%Al) alloys were investigated through the addition of synthetic graphite and activated charcoal inoculants. The mechanical and dry sliding wear properties of AZ 81 (Mg–8%Al) alloys with and without grain refiners were studied. The composition, microstructure and wear surface of the cast alloys were analyzed with the aid of atomic absorption spectroscopy, optical and scanning electron microscopes. The wear test was conducted at a speed of 5.37m/s and two loading (20N and 30N) conditions in a pin on disc wear apparatus. The mean grain size of the alloy is significantly reduced from about 185 to 32μm when the carbon content is increased to 0.98% C. Both tensile strength and ductility increase with increasing carbon content. Also, the wear rate decreases with the increase of carbon content in the alloy. The activated charcoal with 0.98wt% C is found to be a better grain refiner in improving the properties of tensile behaviour and wear resistance. The fracture surface morphology shows the brittle intergranular fracture. Analyses of wear surface morphology show that abrasive and delamination wear mechanisms are responsible for the wear loss in the AZ 81 alloy.

In the present study, the composites of A357 (Al-7%Si) alloy reinforced with the bimodal sizes (~250µm (L) and ~38 µm (S)) of 6wt% SiCp and the A357 alloy were prepared by permanent mould die casting. Three different combinations of bimodal distributions were considered: (3% L + 3% S, 4% L + 2% S, and 2% L + 4% S). The wear behavior of the alloy and the composites was studied for the speed of 1 m/s and load conditions of 10-30 N with an interval of 5 N in a pin on disc apparatus. The hardness and microstructure of the composites were also characteristised. The results suggest that the addition of bimodal size of particles significantly improves the hardness and wear resistance of the alloy. Among the different combinations, the 4% L + 2% S bimodal distribution combination provides the highest wear resistance and the hardness. This result indicates that the higher amount of large size particles are more important than that of small size particles to improve the wear resistance, which implies that the particle decohesion is the rate controlling step in the present investigation. The wear rate increases with an increase of load and sliding distance. The critical load to enter into the severe wear regime for the alloy and composites is 25 N. The rapid wear loss begins above 1500 m sliding distance in the composites and the as cast alloy. The wear rate curve with respect to the sliding distance shows three regimes (1) transition period (2) steady state (3) severe wear state. The wear morphology studies show that the abrasive wear is the main wear mechanism in the bimodal size composites whereas the delamination wear is predominant in the alloy.

In this study, A357 (Al-7%Si-0.5%Mg) alloy/Al2O3 composites with various volume fractions (4%, 8%, 10%) were prepared by using permanent mould casting. In addition, A357 alloys were cast for comparison purposes. The alloys and composites were given a T6 heat treatment process (solution treatment and artificial ageing), Also microstructure, hardness and tensile properties of these composites were evaluated and compared. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus at a constant sliding velocity of 1m/s and pressure of 0.35 MPa. The microstructure of the composites shows homogenous distribution of Al2O3 plate-like particles in the Al matrix except in the A357/10%Al2O3 composite. The wear and mechanical properties of composites improve with increasing the volume fraction of Al2O3 upto 8% and then decreases. Particularly, mechanical properties of the A357/10%Al2O3 composite are lower than the alloy indicating that the critical volume fraction of Al2O3 reinforcement in the A357 alloy is 8%. Wear morphology studies show that abrasive and delamination wear are extensive in the alloy whereas the slight delamination wear with some abrasive grooves are found in the composites.

The effects of quench delay time on tensile properties of AA 7075 Al alloy were investigated for various diameters (30, 65, 100, 125 and 165 mm). The bars were kept in air after solution treatment for selected delay time depending on the diameter and were given water quenching and double ageing. Tensile properties and microstructure properties were investigated. The tensile and yield strength properties decrease with increasing the quench delay time and there has been no specific trend observed between the tensile properties and the quench delay time. The drop in the tensile strength may be categorised into three regions: 30-65, 100-125 and 165-200 mm, the strength variation within the region is negligible in contrast to the wide variation observed between the regions, the superimposition of the C curve with the predicted time data explains reasonably the cause of drop in mechanical properties with the diameter.

The failure of turbine blades due to solid particle erosion is a serious concern in aviation applications. This research investigates the solid particle erosion behavior of laser powder bed fused IN718 alloy for the effect of temperature (400 °C, 500 °C, and 600 °C) and impact angle (45 deg and 90 deg) in a gas-jet erosion setup. The erosion rate progressively increased with the test temperature and it is significantly higher in the 45 deg eroded samples. The eroded samples were characterized for residual stress distribution, surface topography, and surface roughness using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and 3D optical profilometer. Compressive residual stress is evident in all eroded samples, and higher residual stress is measured in the 90 deg eroded samples. Ploughing, crater lip formation, and cracking are the erosion features observed in the 45 deg eroded samples. In comparison, localized plastic deformation, platelet mechanisms, and cracked ridges are observed in the 90 deg eroded samples. Crack formation at 600 °C test condition is attributed to severe erosion degradation in both the impact conditions (45 deg and 90 deg). The as-printed and solution-double aged samples were thoroughly investigated for microstructure and microhardness distribution at the region parallel and perpendicular to the build direction.

Multicolor electrochromic systems based on heat cross-linkable arylamine-substituted fluorene derivatives, FDand FDOMe, are reported. These derivatives with pendant vinyl groups have been synthesized by the Buchwald–Hartwig amination reaction and were well-characterized using various analytical and spectroscopic techniques such as NMR, ESI-MS, and single-crystal X-ray diffraction analysis. FDand FDOMeexhibited thermally activated cross-linking above their melting temperatures, which was confirmed through absorption, differential scanning calorimetry (DSC), FT-IR, and wide-angle X-ray diffraction (WAXD) techniques. Cross-linked FDfilms (FD-X) on ITO showed two reversible redox peaks at 0.74 and 0.91 V (versus Ag/AgCl) that correspond to the formation of radical cations and dications, respectively. The corresponding redox peaks were observed at 0.6 and 0.8 V for cross-linked FDOMefilms (FDOMe-X). Spectroelectrochemical studies of the electrochromic films on ITO revealed multicolor electrochromism of FD-X(colorless–yellow–dark cyan) and FDOMe-X(colorless–brick red–blue) with a color contrast of ∼44% at 485 nm for FD-Xand ∼63% at 500 nm for FDOMe-Xand good switching stability between the neutral and oxidized states (>300 cycles) with low switching voltages (<0.9 V for the first oxidation and <1.3 V for the second oxidation). Furthermore, fabrication of electrochromic devices using FD-Xand FDOMe-Xon FTO substrate with PMMA-based solid electrolyte was demonstrated, where the devices exhibited reasonably low switching time between the redox states (<30 s) with good optical contrast.

Ti-6Al-4V alloy is widely used in Aerospace applications owing to its high specific strength, low coefficient of thermal expansion and good corrosion resistance. Presence of interstitial elements in the alloy has some significant effects on its properties. However the poor notch toughness and cryogenic ductility restricts the usage of Ti-6Al-4V for temperatures lower than 77 K (-196 °C). The Extra Lower Interstitial grade alloy was developed in order to improve the notch toughness and cryogenic ductility of the Ti-6Al-4V alloy. In this refined grade, the interstitials, Oxygen and Carbon are controlled to a maximum limit of 0.12% and 0.08% respectively as compared to a maximum of 0.2% and 0.1% of standard Ti-6Al-4V alloy. In this study, the ELI grade of Ti-6Al-4V rods from three different manufacturing sources were subjected to tensile test at liquid hydrogen temperature at 20 K (-253 oC). The tensile properties obtained are compared and analyzed. The obtained ductility at 20 K is observed to have close relation with the chemical composition and interstitial content and compared with the Ti5Al2.5Sn-ELI which is ideally suitable for low temperatures upto 20 K, owing to its single phase HCP structure. A correlation has been made between the ductile properties and microstructure. By close control of chemical composition and mechanical working, Ti6Al4V-ELI can be used for temperatures lower than 77 K (-196 oC), which is otherwise is forbidden. This paper details the test data obtained from three different compositions of Ti6Al4V-ELI at 20 K, which enables the usage of this material for temperatures lower than 77 K (-196 °C) upto 20 K.

Gears play an important role in every aspect of power and motion of transmission from historical period to modern day period . Due to this , gear design has become a complicated art.A considerable amount of research has been carried out to determine the amount of dynamic gear tooth loads acting.The findings of the dynamic load between the gear teeth results in difficulty for the designer.In this paper, an effort has been made to formulate a simple design procedure for calculating the dynamic load .Earlier the stiffness characteristics and deformation of the gear tooth were studied to predict the dynamic load acting. This was developed with the tooth assumed as a short cantilever.Whereas in reality, an involute profile exists in a spur gear tooth.Based on this reality, work has been done to model the exact profile of the tooth.Later ,the stiffness characteristics were carefully analysed and an improvement was thus made. It was proved that FEA is one such technique that can be used for predicting dynamic loads acting on a gear tooth.

Polyols from chaulmoogra seed oil and grape seed oil were prepared by epoxidation and ring opening of oxirane ring using lactic acid in nitrogen atmosphere with a control over their functionality. Nanocellulose was derived from Desmostachya Bipinnata grass leaves and further surface functionalized. Modified nanocellulose was used as filler to prepare porous flexible bio-based polyurethane nanocomposites via in-situ polymerization. Adsorption of malachite green (MG) dye from wastewater using the prepared polyurethane composites was carried out. The effect of varying factors such as weight percentage of filers (modified nanocellulose), dosage of the adsorbent, pH, temperature and time on the MG adsorption have been studied experimentally. Material characterization for prepared materials was carried out using FTIR, NMR, TGA, DSC, and SEM along with other physical and chemical methods. FTIR results indicated the presence of peaks at 1704 cm−1for –C=O stretching vibrations from urethane groups, 1531 cm−1for –NH bending, 1232 cm−1for –C–N stretching and 1105 cm−1for –C–O stretching in the urethane group (–NHCOO–) thus, indicating the formation of urethane linkage in the polyurethane. Polyols with functionality around 2.8 were obtained from the oils, which has contributed to forming flexible polyurethanes. Morphological studies indicate the nano fibrillation of cellulose and closed-cell porosity in polyurethane and its composites. The flexible porous PU and its nanocellulose composites displayed improved thermal stability from 256.3°C to 270.5°C. Taguchi’s L27orthogonal array have been applied for experimental design and optimization and the results were analyzed using ANOVA for raw and S/N ratio. It was found that pH is the most influential factor for adsorption lead by quantity of nanocellulose, time, dosage of the adsorbent and temperature.

Blindness is an obstacle that is not even comprehendible for the non-blind. Many day-to-day activities may become challenging, complicated and may require much more labor for those with eye-sight problems or blindness. One of the major problems they face is understanding visual or text information which are not in the Braille form. Not every written or printed document that a blind person would like to read is available in Braille. A blind cannot read any of the handwritten documents. They feel it very difficult, while someone has to read it for them. This is the fundamental issue that we deal with, and try to solve, with a new piece of technology, which is essentially an automated text-to-audio converting pen. According to this keynote concept, any piece of text that a person would like to read/understand is converted to an audio signal. This audio signal is transmitted to the person’s ears through wireless technology such as Bluetooth. Since this technology is in the form of a pen, it is very convenient to use and is also portable. This instrument is radical and can definitely be a empowering force in a blind person’s life, and can be helpful in relieving them of their frustration of not being able to read whatever they want, thus making their life easier.

In this work, the effect of the nitriding process on microstructure and mechanical properties of additively manufactured (AM) 17-4PH stainless steel is investigated. The nitriding was performed at 530°C, 560°C, and 580°C for 2 hours. The nitriding process improves the hardness and surface roughness of the AM 17-4PH steel. Detailed microstructural characterizations of both as-built and nitride samples are performed using an optical microscope, scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction technique. It reveals that the nitride layer thickness increases with nitriding temperature. A distinct transition layer between the substrate and nitride layer is observed in the 560°C and 580°C nitride samples. The nitriding process develops almost equiaxed grain microstructure with new secondary phase precipitates, whereas in the as-built material, the grains are primarily columnar along the AM process build direction. Specifically, the nitriding process introduces γ-Fe4N, ε-Fe3N, CrN, and Ni3N precipitates. The increase in Ni- and Cu-rich precipitates with the nitriding temperature explains the observed improvement in the hardness and surface roughness. Furthermore, the nitriding process does not alter the substrate’s initial weak crystallographic texture.

In this paper, a brief review of the literature on technology choice is presented, the necessity of applying fuzzy set theory to technology choice is discussed, and a brief review of the literature on fuzzy multicriteria decision making is given. An algorithm for the technology choice problem is proposed. This algorithm is based on the fuzzy set theory and hierarchical structural analysis. In this method, experts are asked to give their opinions by pair–wise comparison of variables, in linguistic values (say Very High, High, Medium, Low and Very Low and so on). By aggregating the hierarchy, the preferential weight of each alternative is found, which is called fuzzy choice index. The fuzzy choice indices of various alternatives are ranked and preferential ranking order of alternatives are found. An hypothetical fuzzy technology choice problem is given here to demonstrate the algorithm. The proposed methodology will improve technology choices. The methodology can also be applied to any other multicriteria applications.