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Effect of pulsed current micro plasma arc welding process parameters on fusion zone grain size and ultimate tensile strength of Inconel 625 sheets

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Acta Metallurgica Sinica(English Letters) 2012年第3期25卷 179-189页

作者： Kondapalli Siva prasad Chalamalasetti Srinivasa rao Damera Nageswara rao Department of Mechanical Engineering Anil Neerukonda Institute of Technology & SciencesVisakha- patnam India Department of Mechanical Engineering AU College of Engineering Andhra UniversityVisakhapat- nam India Centurion University of Technology & Management Odisha India

The paper focuses on developing mathematical models to predict grain size and ul- timate tensile strength of pulsed current micro plasma arc welded Inconel 625 nickel alloy. Four factors, five levels, central composite rotatable design matrix is used to op- timize the number of experiments. The mathematical models have been developed by response surface method. The adequacy of the models is checked by analysis of vari- ance technique. By using the developed mathematical models, grain size and ultimate tensile strength of the joints can be predicted with 99% confidence level. Contour plots are drawn to study the interaction effect of pulsed current micro plasma arc welding parameters on fusion zone grain size and ultimate tensile strength of Inconel 625 weld joints.

关键词： Pulsed current Micro plasma arc welding ANOYA response surface method: Inconel 625

The role of Vanadia for the Selective Oxidation of Benzyl Alcohol over Heteropolymolybdate Supported on Alumina

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催化学报 2011年第11期32卷 1719-1726页

作者： Pasupulet Siva Nageswara rao Kasanneni Tirumala Venkateswara rao Potharaju S. SAI prasad Nakka LINGAIAH Catalysis Laboratory Inorganic and Physical Chemistty Division Indian Institute of Chemical Technology Hyderabad 500 607 lndia

A series of 12-molybdophosphoric acid (MPA) supported on V2O5 dispersed γ-Al2O3 catalysts with different vanadia loadings were prepared by impregnation and characterized by N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, in situ laser raman spectroscopy, UV-Vis diffused reflectance spectroscopy, scanning electron microscopy, and temperature-programmed desorption of NH3 techniques. Their catalytic activities were evaluated for the vapor phase aerobic oxidation of benzyl alcohol. The catalysts exhibited high catalytic activity and the conversion of benzyl alcohol depended on the vanadia content while the catalyst with 15 wt% V2O5 content showed optimum activity. The characterization results suggest the presence of well-dispersed V2O5 and partially disintegrated Keggin ions of MPA on the support. In situ raman studies showed a reduced Mo(IV) species when the catalysts were calcined at high temperatures. The high oxidation activity of the catalysts is related to the synergistic effect between MPA and V2O5.

关键词： molybdophosphoric acid vanadia alumina oxidation benzyl alcohol

Friction assisted solid state lap seam welding and additive manufacturing method

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Defence Technology（防务技术） 2016年第1期12卷 16-24页

作者： prasad rao KALVALA Javed AKrAM Mano MISrA Dept. of Metallurgical Engineering University of Utah

This paper describes results of seam welding of relatively high temperature melting materials, AISI 304, C-Mn steels, Ni-based alloys, CP Cu, CP Ni, Ti6Al4V and relatively low temperature melting material, AA6061. It describes the seam welding of multi-layered similar and dissimilar metallic sheets. The method described and involved advancing a rotating non-consumable rod(CP Mo or AISI 304) toward the upper sheet of a metallic stack clamped under pressure. As soon as the distal end of the rod touched the top portion of the upper metallic sheet, an axial force was applied. After an initial dwell time, the metallic stack moved horizontally relative to the stationery non-consumable rod by a desired length, thereby forming a metallurgical bond between the metallic sheets. Multi-track and multi-metal seam welds of high temperature metallic sheets, AISI 304, C-Mn steel,Nickel-based alloys, Cp Cu, Ti6Al4V and low temperature metallic sheets, AA6061 were obtained. Optical and scanning electron microscopy examination and 180 degree U-bend test indicated that defect free seam welds could be obtained with this method. Tensile- shear testing showed that the seam welds of AISI 304, C-Mn steel, Nickel-based alloy were stronger than the starting base metal counterparts while AA6061 was weaker due to softening. The metallurgical bonding at the interface between the metallic sheets was attributed to localized stick and slip at the interface, dynamic recrystallization and diffusion. The method developed can be used as a means of welding, cladding and additive manufacturing.

关键词： Lap seam welding Friction assisted welding Solid-state welding Cladding Additive manufacturing

Evaluating location specific strain rates, temperatures,and accumulated strains in friction welds through microstructure modeling

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Defence Technology（防务技术） 2018年第2期14卷 83-92页

作者： Javed Akram prasad rao Kalvala Vikas Jindal Mano Misra Dept. of Metallurgical Engineering University of Utah Dept. of Metallurgical Engineering Indian Institute of Technology(BHU)

A microstructural simulation method is adopted to predict the location specific strain rates, temperatures, grain evolution, and accumulated strains in the Inconel 718 friction welds. Cellular automata based 2D microstructure model was developed for Inconel 718 alloy using theoretical aspects of dynamic recrystallization. Flow curves were simulated and compared with experimental results using hot deformation parameter obtained from literature work. Using validated model, simulations were performed for friction welds of Inconel 718 alloy generated at three rotational speed i.e., 1200, 1500, and1500 rPM. results showed the increase in strain rates with increasing rotational speed. These simulated strain rates were found to match with the analytical results. Temperature difference of 150 K was noticed from center to edge of the weld. At all the rotational speeds, the temperature was identical implying steady state temperature(0.89 T_m) attainment.

关键词： Microstructure modeling Dynamic recrystallization Friction welding Inconel 718 EBSD Hot deformation Strain map

Experimental evaluation of a 35 kVA downdraft gasifier

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Frontiers in Energy 2013年第3期7卷 300-306页

作者： Ashok Jayawant rao KECHE Gaddale AMBA prasad rao Department ol Mechanical Englneenng National Institute of lecnnology Warangal 506004 (AP) India

Energy conversion systems based on biomass are particularly interesting because biomass utilization effectively closes the carbon cycle besides achieving selfsustainability. Biomass is particularly useful for highly populated and agriculture dependent economic nations like China and India. A compact and cost effective downdrafl gasifcation system was developed. The present paper describes an experimental investigation on a biomass based gasifier engine system with a capacity of 35 kVA for power generation application. The problem of cooling and cleaning the hot and dirty gas from the gasifier has been satisfactorily solved by the effective cooling and filtration system. The gasifier developed is observed to be operation friendly. The quality of gas was evaluated in terms of its composition, conversion efficiency and total particulate matter. The maximum output of the power plant was obtained at the combustion zone temperature of 850~C. The experimental investigations showed that the percen- tage reduction in total particulate matter is 89.32%. The conversion efficiency of the biomass gasifier is found to be dependent on the operation conditions and fuel properties of the gasifier. The optimum value of equivalence ratio was observed to be 0.3134 for achieving the maximum gas conversion efficiency of the present gasifier configuration.

关键词： biomass gasification producer gas equivalence ratio total particulate matter conversion efficiency of gasifier

Spectroscopic investigations on Dy^(3+) ions doped zinc lead alumino borate glasses for photonic device applications

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Journal of rare Earths 2019年第1期37卷 52-59,M0004页

作者： Nisha Deopa Shubham Saini Sumandeep Kaur Aman prasad A.S.rao Department of Applied Physics Delhi Technological University

This paper presents the structural, optical absorption, photoluminescence (PL) and decay spectral properties of Dy^(3+)ions doped zinc lead alumino borate (ZPAB) glasses to elucidate their possible usage in photonic devices such as w-LEDs and lasers. A broad hump shown by the XrD spectrum recorded for an un-doped ZPAB glass confirms its non-crystalline nature. The Judd-Ofelt (J-O) intensity parameter evaluated from the measured oscillator strengths of the absorption spectral features were used to estimate various radiative parameters and also to understand the nature of bonding between Dy^(3+)ions and oxygen ligands. Under 350 nm excitation, the as-prepared glasses are exhibiting two emission bands^4F_(9/2)→~6H_(15/2)(blue),and^4F_(9/2)→~6H_(13/2)(yellow) at 483 and 575 nm,respectively. From the PL spectra,the Y/B ratio values, CIE chromaticity color coordinates and color correlated temperature (CCT) were evaluated. The experimental lifetimes measured from the decay profiles are decreasing with increase in Dy^(3+)ions concentration in these glasses which may be attributed to the cross-relaxation and nonradiative multiphonon relaxation process. Decay profiles observed for higher concentration were well fitted to Inokuti-Hirayama (I-H) model to understand the energy transfer process and subsequent decrease in experimental lifetimes. The higher values of radiative parameters, emission cross-sections,quantum efficiency, optical gain and gain band width suggest the suitability of 0.5 mol%of Dy^(3+) ions in these ZPAB glasses for the photonic device application.

关键词： Glasses J-O parameters Luminescence Inokuti-Hirayama model Energy transfer rare earths

Valorization of banana peel into ?-amylase using one factor at a time (OFAT) assisted artificial neural network (ANN) and its partial purification, characterization, and kinetics study

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FOOD BIOSCIENCE 2023年第3期53卷 472-486页

作者： Saha, shyama prasad Ghosh, Shubham Mazumdar, Deepika Ghosh, Sarbobhouma Ghosh, Dipanwita Sarkar, Mahima Misti roy, Swarnendu Univ North Bengal Dept Microbiol Siliguri 734013 India North Bengal St Xaviers Coll Dept Microbiol Jalpaiguri 735135 India Univ North Bengal Dept Bot Plant Biochem Lab Siliguri 734013 India

In this present study alpha-amylase producing bacteria were isolated from the soil near North Bengal University canteen on an amylase agar medium. Primary screening of the isolates was done by iodine test, based on the clear zone around the bacterial colonies in the media plates. Seven bacterial isolates were selected and quantitatively screened for amylase production. Among them, strain sps2 showing the highest amylase activity (215 +/- 2 IU/ml) was selected for further studies. Isolated strain sps2 was identified both morphologically and biochemically and further confirmed by 16s rrNA sequencing as Streptomyces pratensis sps2 (Gene bank accession No. OP 236721). Optimization of alpha-amylase produced by the isolate was conducted under submerged fermentation of low-cost carbon source banana peel, using a one factor at a time (OFAT) approach. Maximum amylase activity of 821.33 +/- 0.57 IU/ml was recorded after 2 days of fermentation. The artificial neural network (ANN) model was employed using the OFAT data to generate a predictive model for amylase production and the r-value of 0.94496 and the rMSE of 64.82 suggesting that the neural network has the precise capability to generate an optimization environment. Ammonium sulfate precipitation and dialysis techniques were used to partially purify the alpha-amylase and then characterized. The enzyme was found to have a molecular mass of 28 kDa (SDS-PAGE and zymogram) with a Km and Vmax of 2 mg/ml and 1000 mu mol/min, respectively. The enzyme was found to be thermostable in the temperature range of 4-90 degrees C and more stable at alkaline pH with optimum pH of 7.

关键词： ?-amylase Streptomyces pratensis sps2 OFAT ANN Km Vmax

Enhanced visible green and 1.5μm radiative emission of Er^(3+)ions in Li_(2)O-PbO-Al_(2)O_(3)-B_(2)O_(3) glasses for photonic applications

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Journal of rare Earths 2021年第5期39卷 520-525页

作者： Nisha Deopa Mukesh K.Sahu Sumandeep Kaur Aman prasad K.Swapna Vinay Kumar r.Punia A.S.rao Department of Physics Chaudhary Ranbir Singh UniversityRohtak Bypass RoadJind126102HaryanaIndia Department of Applied Physics Delhi Technological UniversityBawana RoadNew Delhi110042India Department of Physics K L Educational FoundationVaddeswaram522502Guntur(Dt.)Andhra PradeshIndia Department of Electronics and Communication Engineering Graphic Era(Deemed to be University)Dehradun248002UttrakhandIndia

A series of Er^(3+)ions doped lithium lead alumino borate(LiPbAlB)glasses were synthesized via melt quench method and their structural,physical and optical properties were ***-Ofelt theory in correlation with the emission and absorption profiles was performed for the measurement of various radiative parameters for different transitions of Er^(3+)doped *** as-prepared glasses show deep green(550 nm)as well as NIr(1532 nm)emission at 380 and 980 nm excitation wavelengths,*** intensity of emission spectra increases with Er^(3+)ions concentration up to 1.5 mol%and beyond quenching is *** Dexter theory applied to the emission profiles reveals the interaction between Er^(3+)ions as dipole-dipole in *** color coordinates are found to fall in the green region of the visible *** is observed that 1.5 mol%of Er^(3+)ions concentration is optimum to exhibit the maximum quantum efficiency,branching ratios,gain bandwidth,emission cross-section,gain crosssection and aptly suitable for visible and NIr photonic applications.

关键词： rare earths Glasses Judd-Ofelt theory Photoluminescence Dexter theory

Numerical investigations on HCCI engine with increased induction induced swirl and engine speed

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Journal of Central South University 2015年第10期22卷 3837-3848页

作者： T.Karthikeya Sharma G.Amba prasad rao K.Madhu Murthy Department of Mechanical Engineering NIT

Homogeneous charge compression ignition(HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NOx as well as soot emissions as it combines the compression ignition(CI) and spark ignition(SI) engine features. In this work, a CI engine was simulated to work in HCCI mode and was analyzed to study the effect of induction induced swirl under varying speeds using three-zone extended coherent flame combustion model(ECFM-3Z, compression ignition) of STAr-CD. The analysis was done considering speed ranging from 800 to 1600 r/min and swirl ratios from 1 to 4. The present study reveals that ECFM-3Z model has well predicted the performance and emissions of CI engine in HCCI mode. The simulation predicts reduced in-cylinder pressures, temperatures, wall heat transfer losses, and piston work with increase in swirl ratio irrespective of engine speed. Also, simultaneous reduction in CO2 and NOx emissions is realized with higher engine speeds and swirl ratios. Low speeds and swirl ratios are favorable for low CO2 emissions. It is observed that increase in engine speed causes a marginal reduction in in-cylinder pressures and temperatures. Also, higher turbulent energy and velocity magnitude levels are obtained with increase in swirl ratio, indicating efficient combustion necessitating no modifications in combustion chamber design. The investigations reveal a total decrease of 38.68% in CO2 emissions and 12.93% in NOx emissions when the engine speed increases from 800 to 1600 r/min at swirl ratio of 4. Also an increase of 14.16% in net work done is obtained with engine speed increasing from 800 to 1600 r/min at swirl ratio of 1. The simulation indicates that there is a tradeoff observed between the emissions and piston work. It is finally concluded that the HCCI combustion can be regarded as low temperature combustion as there is significant decrease in in-cylinder temperatures and pressures at higher speeds and higher swirl ratios.

关键词： HCCI engine ECFM-3Z swirl ratio emissions and performance