Some aspects of workability studies on P/M sintered high strength 4% Titanium carbide composite steel preforms during cold upsetting

Workability is concerned with the extent to which a material can be deformed in a specific metal working process without the initiation of cracks. Ductile fracture is the most common failure in bulk forming process. The formability is a complicated phenomenon which depends on the friction between the preform and the die surface in cold upsetting. A complete experimental investigation on the workability behavior of the steel composite of 4%TiC was performed under different stress states, namely, plane and triaxial stress state conditions. Cold upsetting of the Fe–1.0%C–4%Ti steel composite preforms was carried out applying different lubricants, namely, graphite, zinc stearate and molybdenum disulphide, and without lubricant, and the formability behaviour of the same under plane and triaxial stress state conditions was determined. The curves plotted for different preforms were analysed and relationship was established between the axial strain and the formability stress index under plane and triaxial state conditions. A relationship between the relative density and the axial strain was also established. Various stress ratio parameters, namely, (σ_θ/σ_eff), (σ_m/σ_eff) and (σ_z/σ_eff), under plane and triaxial stress state conditions were determined empirically as a function of the relative density. An attempt is also made to study the variation of slope of the relative density versus stress ratio parameters under plane and triaxial stress conditions with respect to the relative density to identify the pore closure mechanism.     

Influence of Shallow and Deep Cryogenic Treatment on Tribological Behavior of En 19 Steel

 The influence of cryogenic treatment on the wear resistance of En 19 steel was studied. Furthermore, a comparative analysis on the effect of Deep Cryogenic Treatment (DCT, -196 ℃×24 h), Shallow Cryogenic Treatment (SCT, -80 ℃×5 h) and Conventional Heat Treatment (CHT) was done through dry sliding wear testing. The microstructures of CHT, SCT and DCT samples were also examined through scanning electron microscopy. The results indicated that the wear resistance of shallow and deep cryogenically treated samples is higher when compared to that of conventionally treated samples. X-ray diffraction pattern revealed that the transformation of retained austenite into martensite is responsible for the wear resistance improvement.     

Synthesis and characterization of CdWO4 nanocrystals

The CdWO₄ nanocrystals were successfully synthesized by simple co-precipitation method. The X-ray diffraction pattern confirms the phase purity and the single phase formation of monoclinic Wolframite structure of CdWO₄. The average crystallite size of 22 nm was calculated from X-ray line broadening method. The FT-IR spectra confirm the presence of stretching and bending vibrations of metal cations like Cd-O, W-O and Cd-O-W bands in the CdWO₄ structure. The morphological features were analyzed by TEM and HRTEM techniques. The electrical conductivity of the materials is found to increase with increasing temperature as well as frequency which enumerates the semiconducting behavior of the material.     

A distributed parametric model of Brinson shape memory alloy based resonant frequency tunable cantilevered PZT energy harvester

International Journal of Mechanics and Materials in Design - This paper presents, an analytical model of piezoelectric vibration energy harvester consists of Brinson shape memory alloy (SMA) plate...     

Prediction of water retention capacity of hydrolysed electrospun polyacrylonitrile fibers using statistical model and artificial neural network

Box Behnken design of experiment was used to study the effect of process variables such as alkali concentration, temperature and time on water retention capacity of the alkaline hydrolysed electrospun fibres. The hydrolysis of electrospun polyacrylonitrile fibres was carried out using sodium hydroxide with different processing conditions like concentration of alkali, temperature and time. With the increase in the concentration of alkali, time and temperature, the water retention capacity of membrane was found to increase in the membranes. Water retention capacities of the membranes were modeled and predicted using empirical as well as artificial neural network (ANN model). The fiber diameter and mean flow pore diameter of electrospun polyacrylonitrile fibers and hydrolyzed fibers shown in SEM images were 310 ± 50, 275 ± 75 nm, 0.9258 and 1.12 microns, respectively. The present study indicated that the nanofibrous membranes have potential for the water absorbing applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Impact of the shape of electrode-tool on radical overcut of micro-hole in electrochemical micromachining

To make use of the full capability of electrochemical micro-machining (EMM), a meticulous research is needed to improve the material removal, surface quality and accuracy by optimizing various EMM process parameters. Keeping this in view, an indigenous development of an EMM machine set-up has been considered to carry out a systematic research for achieving a satisfactory control on the EMM process parameters to meet the micromachining requirements. In this study an EMM machine has been developed and experiments were conducted to study the influence of some of the major process parameters such as the machining voltage, electrolyte concentrations, the pulse-on-time and the machining current on the machining rate and accuracy. The effect of the shape of the tool electrode tips on EMM has been investigated experimentally with 304 stainless steel sheets. The machining rate and the overcut are significantly influenced by the shape of the tool electrode tip.     

Influence of dimethoxymethane addition on performance,emission and combustion characteristics of the diesel engine

This paper assesses the effects of dimethoxymethane (DMM) blends on combustion characteristics, fuel economy, emissions and engine’s power. Experiments were carried out on a single-cylinder, four-stroke compression ignition engine of direct injection with volume fractions of DMM blends of 5%, 10%, 15% and 20% v/v starting from base diesel. Experimental results suggest that 20% DMM blended with diesel achieved better performance in terms of efficiency as well as in exhaust emissions. Carbon monoxide emission levels, hydrocarbon and smoke are reduced considerably with DMM additions, while the oxides of nitrogen emission in exhaust increase due to higher in-cylinder temperature. The oxygen content in the DMM blends plays a greater role in the combustion process compared to neat diesel fuel. The combustion profile was smoother, and no knocking was experienced while operating with DMM blends. Also, it is observed that addition of DMM in diesel shortens the ignition delay and total combustion duration.     

Structural and electrical studies of nano structured Sn1?x SbxO2 (x?=?0.0, 1, 2.5, 4.5 and 7 at%) prepared by co-precipitation method

SnO₂ semiconducting nanopowders doped with antimony Sn_1−x Sb _x O₂ (x = 0.0, 1, 2.5, 4.5 and 7 at%) was achieved by co-precipitation method. TG/DTA and FT-IR studies revealed the removal of organic residuals in the precursor leading to the formation of oxides during calcinations process. A change in color from white to bluish occurred on calcinations of the powder at 500 °C in air. The distortion ratio, strain and particle size were measured from X-ray diffraction (XRD) spectra and their changes with dopants concentration were determined. Transmission electron microscopy (TEM) images support to conform the particle size. The electrical resistivity and activation energy of the ATO particles decreases as compared with pure SnO₂, due to the incorporation of on Sn⁴⁺ ions by as Sb⁵⁺ ion in the host SnO₂ matrix. Incorporation of Sb⁵⁺ was evidenced through the XPS spectrum.     

Post Hartree-Fock and density functional theory studies on structure and conformational stability of nitrosoethylene and substituted compounds of nitrosoethylene

Post Hartree-Fock and density functional theory (DFT) methods were used to study the different conformers of nitrosoethylene H-CH=CH-NO, and substituted compounds of the nitrosoethylene R-CH=CH-NO (R = Cl, NH2, N(CH3)2, OH, OCH3). The molecules were optimized at MP2/6-31G* level of theory of ab initio and B3LYP/6-31G* and B3PW91/6-31G* levels of theory of DFT. Special emphasis has been given to the effect of substitution of pi-electron donor groups NH2, N(CH3)2, OH, and OCH3, which play a major role in modifying the geometrical parameters of -N=O group by the electronic transmission effects through the central group -CH=CH-. The ability of DFT methods to predict the bond length adjacent to the atoms having lone pair electrons has been discussed. The conformational stabilities have been studied using the relative energies and DFT parameters such as chemical hardness and chemical potential. The role of intra-molecular hydrogen bond on the equilibrium structure has been discussed. The vibrational spectra for the different conformers of the nitrosoethylene and substituted compounds have been generated using the MP2/6-31G* level of theory.     

In Vitro Conditioning of Adipose-Derived Mesenchymal Stem Cells by the Endothelial Microenvironment: Modeling Cell Responsiveness towards Non-Genetic Correction of Haemophilia A

In recent decades, the use of adult multipotent stem cells has paved the way for the identification of new therapeutic approaches for the treatment of monogenic diseases such as Haemophilia A. Being already studied for regenerative purposes, adipose-derived mesenchymal stem cells (Ad-MSCs) are still poorly considered for Haemophilia A cell therapy and their capacity to produce coagulation factor VIII (FVIII) after proper stimulation and without resorting to gene transfection. In this work, Ad-MSCs were in vitro conditioned towards the endothelial lineage, considered to be responsible for coagulation factor production. The cells were cultured in an inductive medium enriched with endothelial growth factors for up to 21 days. In addition to significantly responding to the chemotactic endothelial stimuli, the cell populations started to form capillary-like structures and up-regulated the expression of specific endothelial markers (CD34, PDGFRα, VEGFR2, VE-cadherin, CD31, and vWF). A dot blot protein study detected the presence of FVIII in culture media collected from both unstimulated and stimulated Ad-MSCs. Remarkably, the activated partial thromboplastin time test demonstrated that the clot formation was accelerated, and FVIII activity was enhanced when FVIII deficient plasma was mixed with culture media from the untreated/stimulated Ad-MSCs. Overall, the collected evidence supported a possible Ad-MSC contribution to HA correction via specific stimulation by the endothelial microenvironment and without any need for gene transfection.