Defense Metallurgical Research Laboratory

Hyderabad, India

Defense Metallurgical Research Laboratory

Hyderabad, India
Time filter
Source Type

Rao N.V.,CVR College of Engineering | Kumari V.M.,Defense Metallurgical Research Laboratory
Information Security Journal | Year: 2011

Medical image watermarking has been widely recognized as a relevant technique for enhancing data security, image fidelity, authenticity and content verification in the current e-health environment where medical images are stored, retrieved and transmitted over networks. Medical image watermarking preserves image quality that is mandatory for medical diagnosis and treatment. The present paper highlights essential needs of medical image watermarking with a review of developments since 2000 and simulated experiments to demonstrate the significance of watermarking in medical information management. © Taylor & Francis Group, LLC.

Rao T.S.,ACE Engineering College Ghatkesar | Reddy G.M.,Defense Metallurgical Research Laboratory | Rao S.R.K.,SSN College of Engineering
Metallurgia Italiana | Year: 2016

High strength aluminum alloy 7075 is widely used in aerospace applications. In this investigation, Al-Zn-Mg-Cu alloy- AA7075-T651 was friction stir welded, in two thicknesses-10 mm and 16 mm, in order to investigate variations in microstructure and hardness profiles across the joint in through thickness direction. Process parameters resulting in defect free welds were identified using trial and error method. The variations in microstructures and hardness profiles were studied by means of optical microscopy, transmission electron microscopy (TEM) and hardness tests. 10 mm thick welds were found to show better performance in terms of hardness compared to 16 mm thick welds. However, both welds were found to exhibit significant loss in the hardness in the heat-affected zone (HAZ). Furthermore, the loss of hardness due to the welding is more in 16 mm thick welds. Hardness across the joint increases as the survey moves away from the surface of the specimen to the root of the weld. The weld nuggets in both the welds reveal very fine recrystallized grains and the grain size was found to decrease from surface to root of the joint along the thickness of the weld. TEM studies reveal that the weld nugget suffers from dissolution of precipitates and the HAZ consists of wide precipitate free zones, which are considered responsible for lower hardness in the HAZ. It is concluded that sound welds can be produced on thick plates ofAA7075- T651 and welds made on thicker plates exhibit inferior hardness values.

Srikanth I.,Advanced Systems Laboratory | Daniel A.,Advanced Systems Laboratory | Kumar S.,Advanced Systems Laboratory | Padmavathi N.,Defense Metallurgical Research Laboratory | And 4 more authors.
Scripta Materialia | Year: 2010

High ablation resistant carbon-phenolic (C-Ph) composites were fabricated by the addition of nano silica powder and tested under plasma arc jet at a flux of 2.5 MW m-2. Nano silica C-Ph composites exhibited much higher ablation resistance compared to conventional C-Ph composites under similar conditions. Microstructure and X-ray diffraction studies reveal that nano silica reacts with char at high-temperature, forming ablation resistant silicon carbide phase. The mechanism of in situ siliconization and the thermophysical properties of the C-Ph composites are discussed. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Balaram V.,CSIR - Central Electrochemical Research Institute | Roy P.,National Institute of Oceanography of India | Subramanyam K.S.V.,CSIR - Central Electrochemical Research Institute | Durai L.,Defense Metallurgical Research Laboratory | And 5 more authors.
Indian Journal of Geo-Marine Sciences | Year: 2015

REE (Rare Earth Elements) and yttrium in sea water samples, from the Afanasy-Nikitin Seamount (ANS) located around 3° South latitude and 83° East longitude in the north central Indian Ocean were precisely determined by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) method. A modified procedure has been designed for determination of REE and yttrium wherein the water samples were subjected to a pre-concentration step using bis-2-ethylhexyl phosphoric acid (HDEHP) complexing agent. Sea water reference materials such as NASS-5 and SLEW-3 were used for calibration as well as to check the accuracy of the procedure adopted. Samples were analyzed for REE and yttrium by HR-ICP-MS. Precisions achieved for various rare earths and yttrium is better than 8% RSD with comparable accuracies. Limit of detection (3σ) were generally in the range of 0.02-1.2 pg/ml range for all these elements. This method facilitates rapid and interference-free determination of REE and yttrium from relatively small volume of sea water (10 ml). Recoveries for different REE and Y were better than 5%, and accuracy and precision of the determinations are within 8% RSD. The Ce-negative anomalies with smooth normalized-REE patterns obtained for both certified reference materials and samples further substantiate that the procedure adopted and the data generated are extremely accurate. A slight enrichment of heavy REE were observed in the central Indian Ocean waters which might be attributed to the river flows containing more dissolved trace elements including REE. A sharp negative Ce-anomaly in the normalized REE distribution patterns indicates that the source of REE in particular Ce in marine sediments is seawater. Results of the variation in REE concentrations with depth indicated that the physico-chemical conditions of bottom ocean water follow a very complex mechanism. © 2015, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.

Chander G.S.,Swarna Bharathi Institute of Science and Technology | Reddy G.M.,Defense Metallurgical Research Laboratory | Tagore G.R.N.,National Institute of Technology Warangal
International Journal of Advanced Manufacturing Technology | Year: 2013

Dissimilar joints between austenitic stainless steel and low alloy steel are extensively used in many high temperature applications in the energy conversion systems. In the present investigation, emphasis is made on the influence of process parameters on the impact toughness and hardness of the friction welded joints between these two materials. The important process parameters in friction welding such as friction force, forge force, and burn-off lengths are considered for optimization by Taguchi method using L8 27 orthogonal array. It is found that under low friction force, forging force, and burn-off conditions, the impact toughness is high due to the observed acicular martensite. Low impact toughness is reported for the welds made at higher levels of the parameters. Carbon depletion is also observed close to interface in low alloy steel side. Microhardness at the weld center is less than the microhardness on either side at the interface of low alloy steel and austenitic stainless steel close to weld center. The contribution of each parameter and significance of interactions of these parameters is determined by Taguchi method. Among these parameters, friction force has significant influence and forging force has negligible influence on microhardness. The burn-off has maximum influence while forge force has minimum effect on toughness of the welds. Statistical analysis of variance is carried out, optimum process parameters are evaluated, and regression equations are obtained. © 2012 Springer-Verlag London Limited.

Chander G.S.,Swarna Bharathi Institute of Science and Technology | Reddy G.M.,Defense Metallurgical Research Laboratory | Rao A.V.,Defense Metallurgical Research Laboratory
Journal of Iron and Steel Research International | Year: 2012

Fundamental investigation of continuous drive friction welding of austenitic stainless steel (AISI 304) and low alloy steel (AISI 4140) is described. The emphasis is made on the influence of rotational speed on the microstructure and mechanical properties such as hardness, tensile strength, notch tensile strength and impact toughness of the dissimilar joints. Hardness profiles across the weld show the interface is harder than the respective parent metals. In general, maximum peak hardness is observed on the stainless steel side, while other peak hardness is on the low alloy steel side. A trough in hardness distribution in between the peaks is located on the low alloy steel side. Peak hardness on the stainless steel and low alloy steel side close to the interface increases with a decrease in rotational speed. All transverse tensile joints fractured on stainless steel side near the interface. Notch tensile strength and impact toughness increase with increase in rotational speed up to 1500 r/min and decrease thereafter. The mechanism of influence of rotational speed for the observed trends is discussed in the torque, displacement characteristics, heat generation, microstructure, fractography and mechanical properties. © 2012 Central Iron and Steel Research Institute.

Aditya A.V.,Mahatma Gandhi Institute | Aditya A.V.,Atlas Copco | Subramanian P.K.,Mahatma Gandhi Institute | Gopala Krishna V.,Defense Metallurgical Research Laboratory | Chinta Babu U.,Defense Metallurgical Research Laboratory
Transactions of the Indian Institute of Metals | Year: 2012

This work reports the effectiveness of multidirectional forging in breaking up the as-cast microstructure, and also discusses the influence of variation in rolling path on the homogeneity and grain size in heavily deformed tantalum (Ta) plates that are subjected to static recrystallization annealing. Ingots of electron-beamrefined, Ta were multi-directionally forged and subsequently cold rolled to a strain of 250 %. Cold rolling was performed in three distinct modes and the effect of the change in the rolling path on the microstructure and mechanical properties in as-rolled and annealed condition were investigated. The influence of such rolling path was found to be significantly strong. Results show that the kinetics of static recrystallization in differently rolled products are equal. Microstructural evaluation has revealed a high degree of homogeneity and elimination of orientation effects in cross rolled products. Discussion on the hardness and tensile properties in various conditions is also presented. © Indian Institute of Metals 2012.

Devendra Kumar N.,University of Hyderabad | Rajasekharan T.,Defense Metallurgical Research Laboratory | Gundakaram R.C.,International Advanced Research Center for Powder Metallurgy And New Materials | Seshubai V.,University of Hyderabad
IEEE Transactions on Applied Superconductivity | Year: 2011

The origin of high current densities to very high magnetic fields (better than 10 3A·cm -2 to 6.5 T at 77 K) in YBa 2Cu 3O 7 - δ superconductor fabricated by the preform-optimized infiltration-growth process (POIGP) is investigated. The main techniques used in the paper are field-emission scanning electron microscopy and transmission electron microscopy (TEM). An electron- backscattered-diffraction study of the samples is also carried out. A comparison between the microstructures of the optimized sample with the nonoptimized ones show that extensive twinning on a nanometer scale with crossing twins occurring near the optimally separated Y 2BaCuO 5 precipitates can be the origin of the observed high J c(H) in the POIGP sample. The TEM study reveals the presence of very fine defects starting from the twin boundaries. The observed defect spacing and densities account for the uniformly high current densities observed to high fields. © 2011 IEEE.

Bhuyan R.K.,Indian Institute of Technology Guwahati | Kumar T.S.,Indian Institute of Technology Guwahati | Goswami D.,Indian Institute of Technology Guwahati | James A.R.,Defense Metallurgical Research Laboratory | And 2 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2013

We report the study of the effects of processing parameters and additive concentration on the structure, microstructure and microwave dielectric properties of MTO-CeO2 (x wt.%) ceramics with x = 0, 0.5, 1.0 and 1.5 prepared by solid-state reaction method by adding CeO2 nanoparticles as a sintering aid. The pure Mg2TiO4 ceramics were not densifiable below 1450 °C. However, when CeO2 nanoparticles were added to MTO, the densification achieved at 1300 °C along with the increase in average grain size with the uniform microstructure and improved microwave dielectric properties. This is mainly driven by the large surface energy of CeO2 nanoparticles and their defect energy during the sintering process. While the addition of CeO2 nanoparticles in MTO ceramics does not change the dielectric constant (εr), the unloaded quality factor (Qu) was altered significantly. MTO-CeO2 (1.5 wt.%) ceramics sintered at 1300 °C exhibit superior microwave dielectric properties (εr ∼ 14.6, Q × f0 ∼ 167 THz), as compared to the pure Mg2TiO4 ceramics. The observed results are correlated to the enhancement in density and the development of uniform microstructure with the enhanced grain size. © 2013 Elsevier B.V. All rights reserved.

Srinivasulu G.,Defense Metallurgical Research Laboratory | Ghosal P.,Defense Metallurgical Research Laboratory | Singh N.,National Physical Laboratory India | Naze L.,MINES ParisTech Center of materials | And 5 more authors.
Materials Science and Engineering A | Year: 2014

Low cycle fatigue behavior of an O+B2 alloy was evaluated at 650. °C in ambient atmosphere under fully reversed total axial strain controlled mode. Three different microstructures, namely equiaxed O plus aged B2 (fine O plates in B2 matrix), lenticular O laths plus aged B2 and a pancake composite microstructure comprising equiaxed α2, lenticular O and aged B2, were selected to study the effect of microstructure on low cycle fatigue behavior in this class of alloys. Distinct well-defined trends were observed in the cyclic stress-strain response curves depending on the microstructure. The cyclic stress response was examined in terms of softening or hardening and correlated with microstructural features and dislocation behavior. Fatigue life was analyzed in terms of standard Coffin-Manson and Basquin plots and for all microstructures a prevailing elastic strain regime was identified, with a single slope for microstructures equiaxed and composite and a double slope for lenticular O laths. © 2014 Elsevier B.V.

Loading Defense Metallurgical Research Laboratory collaborators
Loading Defense Metallurgical Research Laboratory collaborators