Department of Mechanical Engineering

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

Chemical and mechanical properties of the welded joint are greatly affected by flux composition. The resulting chemical compositions of C, Si, Mn, P and S in the weld metal have been studied using formulated fluxes. The constrained mixture design, extreme vertices design, has been used to formulate fluxes to study the effect of flux constituents. Regression models were developed for weld metal content in terms of individual flux constituents and their binary mixtures for submerged arc welding of high-strength low-alloy steel. From the results, it is found that CaF2 is the most significant flux constituent and Al2O3 is the second most significant constituent among individual mixtures. CaO-MgO and CaO-Al2O3 binary mixtures are the most effective to change weld metal content. Regression mathematical models have been checked for adequacy using t-test and analysis of variance (F-test). Flux mixtures' composition has been provided for optimum chemical composition of weld metal. © IMechE 2014.

World University root node

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

Modeling flux chemistry for submerged arc weldments of high-strength low-alloy steel

In this paper a nonconforming spectral element method is discussed for the elliptic partial differential equations with periodic boundary conditions. The formulation is based on the minimization of a functional by the least squares method. The periodic boundary conditions are added in the weak form in the formulation of the functional and the normal structure of resulting coefficient matrix is retained. To obtain the conforming solution a set of corrections are made and the error is estimated in H1norm. © 2014 Elsevier Inc. All rights reserved.

Applied Mathematics and Computation

Spectral element method for elliptic equations with periodic boundary conditions

The aim of the present study is to understand the mechanism of propulsion in biological flyers, initially starting from rest, towards development of micro-air vehicles employing the same concept using a computational analysis of the plunging motion of a rigid wing. A two-dimensional numerical model has been developed to probe the fluid mechanics associated with the vertical plunging motion of a flat plate analogous to the biological flight of birds and insects. Recent experiments have shown that propulsion can be achieved in still air by a rigid wing if it is flapped above a critical Reynolds number (based on the flapping frequency). The influence of parameters such as density ratio ρ* and flapping Reynolds number Ref on the propulsion of a vertically heaving wing unconstrained to move in horizontal direction has been investigated. Flow fields generated at different time instants indicate that the interaction with the previous shed vortices creates asymmetry that pushes the wing into locomotion. The vortical wake patterns are scrutinized at steady translation which varied depending upon the Strouhal number. In addition, the behavior of input/output power and efficiency has been quantified.

32nd AIAA Applied Aerodynamics Conference

Forward propulsion of a rigid plunging airfoil

The present study focuses on the analysis of the fluid dynamics associated with the flapping motion of finite-thickness wings. A two-dimensional numerical model for one and two-winged "clap and fling" stroke has been developed to probe the aerodynamics of insect flight. The influence of kinematic parameters such as the percentage overlap between translational and rotational phase ξ, the separation between two wings δ and Reynolds numbers Re on the evolvement of lift and drag has been investigated. In addition, the roles of the leading and trailing edge vortices on lift and drag in clap and fling type kinematics are highlighted. Based on a surrogate analysis, the overlap ratio ξ is identified as the most influential parameter in enhancing lift. On the other hand, with increase in separation δ, the reduction in drag is far more dominant than the decrease in lift. With an increase in Re (which ranges between 8 and 128), the mean drag coefficient decreases monotonously, whereas the mean lift coefficient decreases to a minimum and increases thereafter. This behavior of lift generation at higher Re was characterized by the "wing-wake interaction" mechanism which was absent at low Re. © 2014 AIP Publishing LLC.

Fulltext

Physics of Fluids

Lift-drag and flow structures associated with the "clap and fling" motion

For performance improvement and noise reduction, swept and anhedral tips have been incorporated in advanced geometry rotor blades. While there are aerodynamic benefits to these advanced tip geometries, they come at the cost of complicated structural design and weight penalties. The effect of these tip shapes on loads, vibration and aeroelastic response are also unclear. In this study, a comprehensive helicopter aeroelastic analysis which includes rotor-fuselage coupling shall be described and the analysis results for rotor blades with straight tip, tip-sweep and tip-anhedral shall be presented and compared. The helicopter modeled is a conventional one with a hingeless single main rotor and single tail rotor. The blade undergoes flap, lag, torsion and axial deformations. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The complete 6-dof nonlinear equilibrium equations are solved for analyzing any general flight condition. Response to pilot control inputs is determined by integrating the full set of nonlinear equations of motion with respect to time. The effects of tip-sweep and tip-anhedral on structural dynamics, trim characteristics and vehicle response to pilot inputs shall be presented. Copyright © 2014 by the American Helicopter Society International, Inc. All rights reserved.

American Helicopter Society International - 5th Decennial AHS Aeromechanics Specialists' Conference 2014: Current Challenges and Future Directions in Rotorcraft Aeromechanics

Effects of rotor blade tip geometry on helicopter trim and control response

In this work, a reduced-order forward dynamics of multiclosed-loop systems is proposed by exploiting the associated inherent kinematic constraints at acceleration level. First, a closed-loop system is divided into an equivalent open architecture consisting of several serial and tree-type subsystems by introducing cuts at appropriate joints. The resulting cut joints are replaced by appropriate constraint forces also referred to as Lagrange multipliers. Next, for each subsystem, the governing equations of motion are derived in terms of the Lagrange multipliers, which are based on the Newton-Euler formulation coupled with the concept of Decoupled Natural Orthogonal Complement (DeNOC) matrices, introduced elsewhere. In the proposed forward dynamics formulation, Lagrange multipliers are calculated sequentially at the subsystem level, and later treated as external forces to the resulting serial or tree-type systems of the original closed-loop system, for the recursive computation of joint accelerations. Note that such subsystem-level treatment allows one to use already existing algorithms for serial and tree-type systems. Hence, one can perform the dynamic analyses relatively quickly without rewriting the complete model of the closed-loop system at hand. The proposed methodology is in contrast to the conventional approaches, where the Lagrange multipliers are calculated together at the system level or simultaneously along with the joint accelerations, both of which incur higher order computational complexities, and thereby a greater number of arithmetic operations. Due to the smaller size of matrices involved in evaluating Lagrange multipliers in the proposed methodology, and the recursive computation of the joint accelerations, the overall numerical performances like computational efficiency, etc,; are likely to improve. The proposed reduced-order forward dynamics formulation is illustrated with two multiclosed-loop systems, namely, a 7-bar carpet scrapping mechanism and a 3-RRR parallel manipulator. © 2013 Springer Science+Business Media Dordrecht.

Multibody System Dynamics

Reduced-order forward dynamics of multiclosed-loop systems

Trace levels of hydrogen detection using high surface area nanostructured films is a wide area of research and materials like Zinc Oxide, Tin Oxide etc. have been explored widely for high performance sensor design. In this work we report a highly nano porous palladium film which has been fabricated with a very robust methodology i.e., amenable to microfabrication by using metal co-sputtering and selective etching strategies for sensitive hydrogen detection. The morphology of the highly porous films has been extensively evaluated by scanning electron microscope (SEM) and their chemical composition has been evaluated by energy dispersive X-ray spectroscopy (EDAX). The average pore diameter of the films was recorded as 40 nm with the pore density of 425 pores/μm2. To evaluate the sensitivity of the fabricated device towards hydrogen, the electrical resistance of the film in the presence of trace concentrations of hydrogen was evaluated in the temperature range 140∼240 °C. The fabricated film shows high sensitivity, good response, excellent stability and good reconditionability. The sensor performance shows highest sensitivity (∼80%) at 180 °C at 600 ppm H2 and a cycle time of 28 sec. Copyright © 2014 American Scientific Publishers All rights reserved.

Sensor Letters

Nano porous palladium sensor for sensitive and rapid detection of hydrogen

Exploring the symbiotic nature of biological systems can result in valuable knowledge for computer networks. Biologically inspired approaches to security in networks are interesting to evaluate because of the analogies between network security and survival of human body under pathogenic attacks. Wireless Sensor Network (WSN) is a network based on multiple low-cost communication and computing devices connected to sensor nodes which sense physical parameters. While the spread of viruses in wired systems has been studied in-depth, applying trust in WSN is an emerging research area. Security threats can be introduced in WSN through various means, such as a benevolent sensor node turning fraudulent after a certain period of time. The proposed research work uses biological inspirations and machine learning techniques for adding security against such threats. While it uses machine learning techniques to identify the fraudulent nodes, consecutively by deriving inspiration from human immune system it effectively nullify the impact of the fraudulent ones on the network. Proposed work has been implemented in LabVIEW platform and obtained results that demonstrate the accuracy, robustness of the proposed model. © 2014 IEEE.

Department of Bioscience & Bioengineering

2014 6th International Conference on Communication Systems and Networks, COMSNETS 2014

Novel approach for security in Wireless Sensor Network using bio-inspirations

A mathematical model incorporating higher order deformation in bending is developed to investigate the nonlinear behavior of rotor. Transverse harmonic base excitation is imparted to rotor system and Euler-Bernoulli beam theorem is applied with effects such as rotary inertia, gyroscopic effect, higher order large deformations, rotor mass unbalance and dynamic axial force. Discretization of the kinetic and strain (deformation) energies of the rotor system is done using the Rayleigh-Ritz method. Second order coupled nonlinear differential equations of motion are obtained using Hamilton's principle. Nonlinear dynamic response of the rotor system is obtained by solving above equations using the method of multiple scales. This response is examined for resonant condition. It is concluded that nonlinearity due to higher order deformations and variations in the values of different parameters like mass unbalance and shaft diameter significantly affects the dynamic behavior of the rotor system. It is also observed that the external harmonic excitation greatly affects the dynamic response. © 2014 published by EDP Sciences.

MATEC Web of Conferences

Nonlinear responses of externally excited rotor bearing system

A theoretical investigation of an electrically actuated beam has been illustrated when the electrostatic-ally actuated micro-cantilever beam is separated from the electrode by a moderately large gap for two distinct types of geometric configurations of MEMS accelerometer. Higher order nonlinear terms have been taken into account for studying the pull in voltage analysis. A nonlinear model of gas film squeezing damping, another source of nonlinearity in MEMS devices is included in obtaining the dynamic responses. Moreover, in the present work, the possible source of nonlinearities while formulating the mathematical model of a MEMS accelerometer and their influences on the dynamic responses have been investigated. The theoretical results obtained by using MATLAB has been verified with the results obtained in FE software and has been found in good agreement. Criterion towards stable micro size accelerometer for each configuration has been investigated. This investigation clearly provides an understanding of nonlinear static and dynamics characteristics of electrostatically micro cantilever based device in MEMS. © 2014 published by EDP Sciences.