Dimensional instability studies in machining of Inconel 718 nickel based superalloy as applied to aerogas turbine components

Inconel 718 alloy is used extensively in aerogas turbines and this alloy is most difficult to machine and highly prone to dimensional instability after machining. Such detrimental phenomenon poses an enormous problem in engine assembly and affects structural integrity. This paper highlights the systematic research work undertaken to study the plastic deformation characteristics of Inconel 718, and the effect of process variables on machined surface, subsurface, and dimensional instability. Also illustrated is the technique developed for simultaneous optimization of several process variables such as cutting speed, feed, depth of cut, rake angle, and tool nose radius to control the residual stresses and dimensional instability within the acceptable tolerance band of the component. Prediction equations were developed for residual stress, dimensional instability, tool life, surface finish, and material removal rate. Predicted data were validated experimentally. This paper also presents the qualitative and quantitative data on dimensional instability with specific case studies of jet engine components, and it clearly illustrates the approach followed to develop a technique to control such detrimental effect

Determination of Surface Area of Head for Biomedical and other Applications

A simple, rapid and reproducible method has been devised for measuring the surface area of the head relevant for armour design. In this method, the following stages are involved: (i) securing a kraft paper over the head with the help of elastic band, (ii) tightly folding the paper wherever necessary to make a snug contour-matched paper dome, (iii) marking the folded areas with lines, (iv) spreading the paper and cutting out areas within the folds and the area filling outside the marked periphery of interest, (v) weighing the cut-out pieces and few pieces of known area from the same sheet, and finally (vi) calculating the head-surface area. Preliminary data on 12 volunteers indicated that head-surface area has no significant correlation with their age, total body-surface area calculated from height and weight or with the circumference of their heads. A significant and positive correlation was found with cephalic length. The new method can find application in biomedical studies and head gear designs (e.g. helmets)

Normal and Oblique Impacts of Hard Projectile on Single and Layered Plates-An Experimental Study

The phenomenon of ordnance velocity impact of projectile on single and layered plates is of interest for many applications. In this paper. an experimental study of normal and oblique impacts or an ogive shaped, hard steel projectile on single and layered plates of mild steel and aluminium is presented. The projectiles were fired at an impact velocity of about 820 ms-1. The plate thickness was varied in the range 10 mm to 40 mm and the ratio of plate thickness to the diameter of the projectile varied in the range 1.5 to 13.0. Observations on target damage and measurements of incident and residual velocities for different angles of impact are presented. Plate thickness t*, for which the incident velocity is the ballistic limit, is determined. Computer simulations were carried out using a hydrodynamic code to simulate the normal impact of a projectile and compared these with the experimental results. Experiments were performed to evaluate the response of these plates of intermediate thickness when layered. and the results were compared to the results of single plate of same total thickness

Influence of Polymer Restraint on Ballistic Performanceof Alumina Ceramic Tiles

An experimental study has been carried out to evaluate the influence of confinement ofalumina ceramic tiles through polymer restraint, on its ballistic performance. Tiles of 99.5 per centpurity alumina were subjected to ballistic impact against 7.62 mm armour piercing projectiles atvelocities of about 820 m/s. The tiles of size 75 mm x 75 mm x 7 mm were confined on both facesby effectively bonding varying numbers of layers of polymer fabrics. These were then bondedto a 10 mm thick fibre glass laminate as a backing using epoxy resin. High performance polyethyleneand aramid polymer fabrics were used in the current set of experiments for restraining the tiles.Comparative effects of confinement on energy absorption of tiles with varied number of layersof fabrics were evaluated. It was observed that by providing effective confinement to the tile,energy absorption could be doubled with increase in areal density by about 13 per cent.Photographs of the damage and the effects of restraint on improvement in energy absorptionof ceramic tiles are presented and discussed

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Not AvailableEfficient genetic transformation of sorghum plant requires an effective selection marker system that precisely differentiates transformed cells from non-transformed ones. Hence the present Hygromycin study was undertaken to optimize the selection marker antibiotic Hygromycin to screen transformed cells in sorghum transformation experiments with vectors harbouring hpt gene. Shoot meristem explants of sorghum were grown in somatic embryo induction media containing various concentrations of Hygromycin. At lower concentrations of Hygromycin (20mg/L and less), the growth of shoot apices was unaffected and the survival rates were very high (87.5–100%) during the three sub-culture passages. At a Hygromycin concentration of 50 mg/L the percentage of survival decreased gradually with three subcultures - 62.5, 25 and 0% survival respectively, while at concentrations of 200 and 800 mg/L, these were higher mortalities of explants in the first subculture itself (only 31.3-37.5% survival). The least concentration of Hygromycin at which all susceptible explants died was 50 mg/L (after three subcultures). Therefore it is suggested that 50 mg/L of Hygromycin may be used as the optimum concentration for the selection of sorghum shoot meristem explants transformed with vectors harboring the hpt gene.Not Availabl

Some experimental studies on angle effect in penetration

This investigation describes and analyses the experimental results pertinent to the penetration of Al-7017 plates with non-deformable steel projectiles at a velocity of 840 ± 15 m/s at different angles of impact. The results include the variation in damage pattern, damage area at front and back, mid penetration channel observations, residual velocity and energy absorption capacities at different obliquities. Some observations relating to the adiabatic shear bands formation have also been presented. The micro hardness values along the path of penetration have been studied in order to understand the increase in energy absorption at oblique impact. The experimental data shows a transition of failure mode from an adiabatic shear band induced shear plugging at lower obliquities to a more homogeneous deformation of the target material and gouging at higher obliquities

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Not AvailableSorghum bicolor (L. Moench.) is considered as one of the crop species highly recalcitrant to tissue culture and genetic manipulation studies. During the last two decades several studies were done on sorghum somatic embryogenesis (SE) and plant regeneration, but the rate of plant regeneration was not sufficiently high and practical difficulties still exist in establishing and regenerating plants in a relatively shorter time period. The approach to regenerate the plantlets from somatic cells via intervening callus phase is time consuming and laborious which takes about 15-20 weeks. Hence an improved protocol using direct somatic embryogenic route of regeneration from shoot apices explants was developed. The shoot tips were cultured in the presence of Benzylaminopurine (BAP) and 1- Napthaleneacetic acid (NAA) at varying concentrations in Murashigeand Skoog (MS) media to determine the optimal media for SE as indicated by bulging of explants in the meristematic nodal region. The highest frequency of bulging (80%) due to SE was obtained on MS medium supplemented with 5.0 mgl-1 of BAP and 1mgl-1NAA. Further,plant regeneration could be directly induced from the bulged regions when supplemented half-strength MS media with Indole Butyric acid (IBA) and Indole acetic acid (IAA). Nearly 90% plant regeneration was achieved by using 2 mgl-1 of IBA and 0.5 mgl-1 of IAA. The well rooted plants are subjected to hardening and acclimatization in the glasshouse for 4 weeks. This rapid and efficient sorghum plant regenerative protocol described in this study is more useful for various genetic transformation studies.Not Availabl

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Not AvailableThe already available comprehensive genome sequence information of model crops along with the transcriptomic resource from other crops provides an excellent opportunity for comparative genome analysis. We studied the synteny between each of the four major sorghum staygreen quantitative trait loci (QTL) regions with that in the rice genome and attempted to increase marker density around the QTL with genic-microsatellites from the sorghum transcriptomic resource using the rice genome as template. For each of the sorghum QTL regions, the reported RFLP markers were compiled, used for sequence similarity searches against the rice genome which identified syntenous regions on rice chromosome 1 for Stg1 and Stg2 QTL, on chromosome 9 for Stg3 QTL, and on chromosome 11 for Stg4 QTL. Using the Gramene genome browsing tool, 869 non-redundant sorghum expressed sequence tags (ESTs) were selected and 50 genic-microsatellites (18, 12, 15, and 5, for Stg1, Stg2, Stg3, and Stg4 QTL, respectively) could be developed. We could experimentally establish synteny of the Stg1, Stg2, Stg3, and Stg4 QTL regions with that of the rice genome by mapping ten polymorphic genic-microsatellite markers (20%) to the positions of the staygreen QTL. The simple strategy demonstrated in the present study could readily be extrapolated to other cereals of the Poaceae family. The markers developed in this study provide a basis for the isolation of genes underling these QTL using an association study or map-based gene isolation approach, and create an additional option for MAS of the staygreen trait in sorghum.Not Availabl