Department of Mechanical Engineering

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IIT Jodhpur

World University root node

International Journal of Advanced Robotic Systems

Calibration and statistical techniques for building an interactive screen for learning of alphabets by children

Unsteady flows in highly curved geometries are of interest in many engineering applications and also in physiological flows. In this study, we use flow visualization and computational fluid dynamics to study unsteady flows in a highly curved tube with square cross-section; here, is the ratio of the half edge length to the radius of curvature of the tube. To explore the combined effects of curvature and pulsatility, we use a single flow pulse of duration and peak area averaged axial velocity , which are independently varied to investigate a range of Dean and Womersley numbers. This range includes cases corresponding to flows in the ascending aorta. We observe radially inward moving secondary flows which have the structure of wall jets on the straight walls; their subsequent collision on the inner wall leads to a re-entrant radially outward moving jet. The wall jet arises due to an imbalance between the centrifugal force and the radial pressure gradient. During the deceleration phase, the low-axial-momentum fluid accumulated in the jet reverses direction and leads to flow separation near the inner wall. We use boundary layer equations to derive scales, which have not been reported earlier, for the secondary flow velocities, the wall shear stress components and the distance traversed by the secondary flow structures in the transverse plane. We show that predicts the movement of vortical structures until collision. In the limit , the Reynolds number based on this secondary flow velocity scale asymptotes to the secondary streaming Reynolds number proposed by Lyne (J. Fluid Mech., vol. 45 (01), 1971, pp. 13-31) in loosely curved pipes. The magnitude of the secondary flow velocity is high and of for physiological flow conditions. We show that the flow separation on the inner wall has origins in the secondary flow, which was reported in a few earlier studies, and is not due to the axial pressure gradient in the tube as proposed earlier. The wall shear stress components, hypothesized to be important in arterial mechanobiology, may be estimated using our scaling relations for geometries with different curvatures and varying pulsatilities. © 2017 Cambridge University Press.

Journal of Fluid Mechanics

Separations and secondary structures due to unsteady flow in a curved pipe

The current study involves a simple hydrazine based colorimetric chemo-sensor for selective determination of various anions. The anion-binding ability of the ligand with various anions via polar-non polar interactions and hydrogen bonding has been examined. The sensor displayed significant UV-vis enhancement response to anions such as fluoride, acetate, hydroxide, cyanide and hydrogen sulphate, with respect to concentration and time. The rate constants (K) and binding constants, Ka, for these anions have been measured by using Benesi-Hildebrand equation. A time dependent NMR study revealed stronger interaction for cyanide and fluoride ions among competing anions. © 2017 by Elsevier B.V.

Department of Chemistry

Journal of Environmental Chemical Engineering

Dipicrylhydrazine: A versatile visual anions sensor

This paper discusses the development of an optimal wheel-torque controller for a compliant modular robot. The wheel actuators are the only actively controllable elements in this robot. For this type of robots, wheel-slip could offer a lot of hindrance while traversing on uneven terrains. Therefore, an effective wheel-torque controller is desired that will also improve the wheel-odometry and minimize power consumption. In this work, an optimal wheel-torque controller is proposed that minimizes the traction-to-normal force ratios of all the wheels at every instant of its motion. This ensures that, at every wheel, the least traction force per unit normal force is applied to maintain static stability and desired wheel speed. The lower this is, in comparison to the actual friction coefficient of the wheel-ground interface, the more margin of slip-free motion the robot can have. This formalism best exploits the redundancy offered by a modularly designed robot. This is the key novelty of this work. Extensive numerical and experimental studies were carried out to validate this controller. The robot was tested on four different surfaces and we report an overall average slip reduction of 44% and mean wheel-torque reduction by 16%. © Cambridge University Press 2015.

Robotica

An optimal wheel-torque control on a compliant modular robot for wheel-slip minimization

We describe the modeling, estimation and control of a quadrotor in 3D environment using the 3DR Pixhawk PX4 as controller through Robot Operating System(ROS). The paper discusses a method to measure moment of inertia of quadrotor about its principal axes to achieve better results in an inexpensive way. We also present the trajectory generation and segment optimization of the trajectory commanded to the quadrotor. We describe a method of controlling the quadrotor through ROS by providing necessary inputs to the flight controller using the built-in firmware. © 2016 IEEE.

International Conference on Robotics and Automation for Humanitarian Applications, RAHA 2016 - Conference Proceedings

Design, trajectory generation and control of quadrotor research platform

One of the major challenges in the fabrication of glass-metal Joint is the wettability of glass sealant over the metal surface. The aim of the work was to study the wetting and spreading behavior of borosilicate glass sealant over austenitic stainless steel SS 304 and copper substrates with different surface roughness and oxidation conditions. During the wettability study of borosilicate glass sealant over the metal specimen, glass pallets were melted over the different oxidized metal specimens. The wetting behavior of borosilicate glass over metal specimen was measured in terms of contact angle and spreading area. The types of oxide and change in microstructure after oxidation were examined with the help of XRD analysis and optical microscopy. Tensile strength and hardness of the metal substrates after oxidation was also evaluated. © 2017 Trans Tech Publications, Switzerland.

Materials Science Forum

Effect of surface roughness and oxidation conditions on wettability of borosilicate glass sealant

The bimetallic weld joints are widely utilized in the pressurized water reactors, boiling water reactors, heat exchangers in process industries, heat transport piping system utilized in nuclear plants, etc. The present study is aimed at analyzing the bimetallic weld strength degradation due to thermal fatigue. For generating thermal fatigue like conditions, an experimental test rig has been developed. The bimetallic weld between low alloy steel SA 516 grade 70 and stainless steel 304 L was prepared. The experimental results show that, heating time, notch radius and number of cycles have the effect on tensile properties of bimetallic welds. © 2017 Trans Tech Publications, Switzerland.

Experimental analysis of thermal fatigue in bimetallic welds

A commercial organically modified montmorillonite Cloisite® 15A was modified via a new silanization route by two different silane coupling agents: 3-Aminopropyltriethoxysilane and 3-Glycidyloxypropyltrimethoxysilane. This method enables the use of very high concentration of silanes for functionalization of clay minerals. The ratio of weight of silane coupling agent to that of weight of clay mineral (X) was varied from 0.1 to 6. Small angle X- ray scattering and thermogravimetric analysis were carried out on silane modified clay minerals to quantify the grafting of silanes as a function of ratio of weight of silane agent to that of clay mineral. Fiber reinforced epoxy nanocomposites containing silylated clay minerals were manufactured using vacuum assisted resin infusion molding method. Also, curing studies were carried out on fiber reinforced epoxy nanocomposites containing Cloisite® 15A at different cure temperatures, e.g. 70 °C, 80 °C, 85 °C, 95 °C and for two different curing time periods, e.g. 7 h and 10 h. Significant improvements in mechanical properties of fiber reinforced nanocomposites were obtained with incorporation of clay minerals silanized using high concentration of silanes in solvent and chosen curing schedule. The tensile modulus, tensile strength, flexural modulus and bending strength increased by 30%, 37%, 139% and 146% respectively, in nanocomposites containing clay mineral modified using 4X aminopropyltriethoxysilane. An attempt has been made to correlate the results with the morphology of nanocomposites by transmission electron microscopy and that of fractured surfaces by scanning electron microscopy. © 2016 Elsevier B.V.

Applied Clay Science

Curing studies and mechanical properties of glass fiber reinforced composites based on silanized clay minerals

The Glass-Metal Joints play an indispensable role in many applications such as, in concentrating solar power, nuclear and electronics industry. The aim of the present work is the fabrication of glass-metal joints using borosilicate glass with austenitic stainless steel and copper. The joints were fabricated using resistance heating and mechanical behavior of these fabricated joints was determined. Single lap joint between glass and metal was used in order to measure the strength of glass-metal joint. The micro-hardness evaluation of these fabricated joints was also carried out. Oxidation studies were also conducted to examine the role of oxide formation in the joints using X- Ray Diffraction measurements. The mechanical behavior and microstructure evolution of austenitic stainless steel to borosilicate glass joint and copper to borosilicate glass joint were analyzed and it was found that bonding characteristic of different glasses with copper was poor, because of its poor thermal stability at higher sealing temperature. Out of different composition glasses, G6 glass resulted shear strength around 0.124MPa which was the maximum among all joints. © 2017 by The American Ceramic Society.

Ceramic Engineering and Science Proceedings

An experimental study on fabrication, mechanical behavior characterization and micro structural evolution in glass-metal joints

The microstructural and mechanical properties of creep enhanced ferritic (CSEF) steels are affected by various parameters, solutionizing temperature is one of them. In the present investigation, the effect of normalizing temperature on the microstructural and mechanical properties of cast and forged (C&F) P92 steel were carried out. Grade P92 steel is considered as a candidate material for Thermal and Nuclear power plants at temperatures of up to 650 °C. In this study, C&F P92 steel was subjected to various normalizing temperatures (from 950 °C to 1150 °C). For microscopic characterization, Optical microscope and Field emission scanning electron microscope (SEM) were used. The grain size, precipitate size, area fraction of precipitates and Cr/Fe were calculated from micrographs. The normalized specimens were tested for tensile strength, hardness, and toughness. Considering observation for the optimum combination of strength, ductility, and toughness, the normalizing at 1000 °C and tempering at 760 °C has been suggested for C&F P92 steel. © 2017 Elsevier B.V.