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Hyderabad, India
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Raut A.,Kalinga Institute of Dental science | Paradkar A.,DMRL | Malakondaiah G.,DMRL
Indian Journal of Dental Research | Year: 2013

Statement of Problem: Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. Purpose: This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. Materials and Methods: The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Results: Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Conclusion: Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.


Srinivasa Vadayar K.,Jawaharlal Nehru Technological University | Satyanarayana D.V.V.,DMRL | Bhanu Prasad V.V.,DMRL | Poshal G.,IARE
Materials at High Temperatures | Year: 2013

TiB-TiC reinforced titanium matrix composites (TMCs) were synthesised through pressureless sintering of titanium and boron carbide (B4C) powder compacts. Effect of boron carbide (B4C) particle size and volume fraction of TiB-TiC reinforcement on steady state compression creep behaviour of composites was investigated in the temperature range of 773-873 K. The creep rates of composites are found to be about two orders of magnitude lower than those of unreinforced titanium. The creep rates further lowered with decrease in size of B4C particles (from 16 to 3 μm) used in preparation of composites as well as with increase in volume fraction of the TiB-TiC reinforcement from 10 to 30 vol.%. By using the concept of effective stress as well as incorporation of load transfer and substructural strengthening effect produced by the reinforcement into analysis, the entire creep data of Ti and the composites can be made to merge on to a single line within a scatter band of factor of 2-3 and can be represented by a unified power-law equation.


Srirangarajalu N.,Anna University | Reddy G.M.,DMRL | Rao S.R.K.,Tagore Engineering College | Rajadurai A.,Anna University
Communications in Computer and Information Science | Year: 2012

The objective of this experimental study was analyzing the joining behavior of 6 mm thick cold rolled copper plate using Friction Stir Welding (FSW) technique. The role of tool rotational speed, travel speed and tool pin profiles on the weld quality, tensile and bend behaviors, hardness, and microstrucuture was investigated. Defect free weld was obtained at tool rotational speeds ranging between 1300 - 1600rpm and welding travel speeds ranging between 30-45mm/min. Tensile strength interms of joint efficiency was found to be 73% compare to the base material (BM). The average hardness of the nugget zone was lesser than the base material because of annealing of the cold rolled copper plates during welding. Different microstructure zones were revealed by optical microscopy (OM). The nugget zone (NZ) and heat affected zone (HAZ) were found to have fine equiaxed grains and fine elongated grains respectively. © 2012 Springer-Verlag.


Khaple S.,DMRL | Baligidad R.G.,DMRL
Transactions of the Indian Institute of Metals | Year: 2012

This article presents the effect of melting process on chemical composition, microstructure and mechanical properties of Fe-7 wt% Al alloy. The alloy ingot was prepared by air induction melting (AIM), air induction melting with flux cover (AIMFC) and vacuum induction melting (VIM) and cast into 50 mm diameter split cast iron mould. These cast ingots were hot-forged and hot-rolled at 1,373 K to 2 mm thick sheet. Hot-rolled alloys were characterized with respect to chemical composition, microstructure and mechanical properties. Ingots produced by AIM, AIMFC and VIM were free from gas porosity, however AIM ingots exhibited higher concentration of hydrogen as compared to AIMFC and VIM. The recovery of aluminium as well as reduction of oxygen during AIM is very poor as compared to AIMFC and VIM. AIMFC ingots exhibit low level of sulphur as compared to AIM and VIM ingots. The alloys produced by AIMFC and VIM exhibited superior tensile ductility compared to the alloys produced by AIM. The tensile properties of alloys produced by AIMFC are comparable to the alloys produced by VIM. © 2012 Indian Institute of Metals.


Srinivasu G.,National Institute of Technology Warangal | Natraj Y.,Indian Institute of Technology Kharagpur | Bhattacharjee A.,DMRL | Nandy T.K.,DMRL | Nageswara Rao G.V.S.,National Institute of Technology Warangal
Materials and Design | Year: 2013

The effect of processing and heat treatment has been studied on tensile properties and fracture toughness of a high strength metastable beta titanium alloy, Ti-10V-2Fe-3Al. The alloy was double melted by vacuum arc melting and subsequently subjected to thermomechanical processing that included combinations of rolling and solution heat treatment both in α-β and β phase fields. Rolling temperatures were varied from 710. °C (sub-transus) to 860. °C (super-transus) and solution treatment temperatures were varied from 710. °C (sub-transus) to 830. °C (super-transus). A systematic microstructural investigation (optical as well as scanning electron microscopy) was undertaken in order to correlate the property trends with underlying microstructure which is strongly dependent on the thermomechanical processing sequence. A subtransus rolling followed by subtransus solution treatment resulted in equiaxed α morphology whereas a supertransus rolling followed by subtransus solution treatment resulted in more acicular/lenticular morphology of α phase. While α-β rolling followed by α-β heat treatment gave better tensile properties, β rolling followed by α-β heat treatment resulted in superior fracture toughness. © 2012 Elsevier Ltd.


Arivazhagan N.,Vellore Institute of Technology | Narayanan S.,Vellore Institute of Technology | Singh S.,Indian Institute of Technology Roorkee | Prakash S.,Indian Institute of Technology Roorkee | Reddy G.M.,DMRL
Advanced Materials Research | Year: 2012

In the present work hot corrosion studies were carried out on electron beam welded AISI 304 and AISI 4140 dissimilar weldment in molten salt (K 2SO 4-60% NaCl) environment at 800 °C for 50 cycles. The weight gain follows parabolic law in all the cases. It is observed that the scale formation was maximum on 4140 side as compared on 304 side. Moreover higher content of Fe 2O 3 and Cr 2O 3 on scale over weld zone may be due to enrichment of this zone with Fe and Cr. This could be attributed to diffusion of chromium towards AISI 4140 from the AISI 304 and diffusion of iron from AISI 4140 side towards AISI 304. Furthermore weld interface suffered accelerated corrosion behavior in the chloride and sulfate mixed molten salt environment in the form of intense spalling and sputtering of its scale. The cracking of oxide scale on the weldment might be attributed to different composition of base metals, weld metal and oxide formed.


Rajasekaran N.,CSIR - Central Electrochemical Research Institute | Mohan S.,CSIR - Central Electrochemical Research Institute | Arout Chelvane J.,DMRL | Jagannathan R.,CSIR - Central Electrochemical Research Institute
Journal of Magnetism and Magnetic Materials | Year: 2012

Cu-Co ferromagnetic alloys occurring as granular films and exhibiting giant magnetoresistance (GMR) property have been synthesized using both DC and pulse electrodeposition techniques. The growth process of these electrodeposits comprising multiple granules of disparate morphology, magnetic features exhibits critical dependence on electrodeposition conditions. Using ferromagnetic resonance and magnetic hysteresis data, we have attempted a correlation between evolution of these electrodeposits and their ferromagnetic properties with special emphasis on GMR property. © 2012 Elsevier B.V. All rights reserved.


Sivasankar S.,Indian National Institute of Engineering | Jeyapaul R.,Indian National Institute of Engineering | Bhanu Prasad V.V.,DMRL
Multidiscipline Modeling in Materials and Structures | Year: 2012

Purpose - This study aims to explore the machinability of ZrB2 using electrical discharge machining (EDM) with different tool materials. Design/methodology/approach - The workpiece for this study was fabricated through powder metallurgy compaction method. The disc is machined using diamond load grinding to have parallel surfaces, then, 2 mm diameter holes are machined on the disc using EDM spark erosion machine with different tool materials (graphite, aluminium, tantalum, niobium, copper, brass, silver, tungsten and titanium). Roundness, geometry of hole, and diameter of the hole at different diametric planes, surface roughness (SR), material removal rate (MRR), tool wear rate (TWR), taper angle and recast layer (RCL) thickness are measured. The photographic analysis of tools, holes in the top view, bottom view and sectional view. SEM analysis was conducted to study the recast layer. Desirability function analysis was employed to rate the performances of tools. Findings - A new theory is developed which relates recast layer thickness with melting point and thermal conductivity of the tool materials. Machining of ZrB2 by EDM is feasible; graphite is identified as the best tool. Recast layer thickness of the machined surfaces are indirectly proportional to the product of melting point and thermal conductivity of tool. Ablation behaviour of ceramic workpiece lead additional material losses in the tool. Originality/value - Extremely high strength and hardness of ZrB2 due to the coexistence of strong covalent and metallic bond make mechanical machining very difficult or even impossible. No machinability studies were conducted previously on ZrB 2 using EDM; this work reveals machinability study of ZrB2 with different tool materials. © Emerald Group Publishing Limited.


Manikandan M.,Vellore Institute of Technology | Nageswara Rao M.,Vellore Institute of Technology | Ramanujam R.,Vellore Institute of Technology | Ramkumar D.,Vellore Institute of Technology | And 2 more authors.
Procedia Engineering | Year: 2014

In the present work, a Design Of Experiment (DOE) technique, the Taguchi method was employed to bead on welding trials to optimize Pulsed Current Gas Tungsten Arc (PCGTA) welding process parameters of alloy C-276. A L9 orthogonal array of Taguchi design involving nine experiments for four parameters (pulsed current, background current, % on time, pulse frequency) with three levels was used. An analysis of the mean of signal-to-noise (S/N) ratio indicates that the depth of current is influenced significantly by the levels in the Taguchi orthogonal array. The higher the better response category was selected to obtain optimum conditions for depth of penetration. The optimum conditions were found to be 165 A pulse current, 77 A background current, 60 % on time and 5 Hz pulse frequency. Analysis of Variance (ANOVA) is performed to measure percentage contribution of each factor. The results show that the pulse current was most influencing parameter on the depth of penetration and % on time (23.28 %) the next most influencing. Confirmation test was carried out to validate the results of Taguchi analysis; the result shows that there is good match between expected and predicted results. © 2014 The Authors.

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