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

The effect of squeeze air-film and AC actuation voltage on dynamic stability of microswitch actuated electrostatically has been investigated in squeeze film domain. The dynamics of the device has been developed considering the load arising from the squeezed air film between the microcantilever attached plate and the grounded substrate. Using trajectories in phase plane and time history, characteristics of the pull-in phenomena have been studied in the presence of DC voltage combined with AC component. Pull-in voltage is observed to be less as compared to the conventional micro-cantilever devices which are actuated only due to DC loading. Furthermore, the dynamic pull-in voltage tends to approach static pull-in voltage, when the squeeze film damping is considered. The study indicates that although electrostatic forces cause softening characteristics, geometric nonlinearity produces a stiffening effect on the microstructure and the nonlinearities play a significant role when pull-in occurs. The ability to resist the bending deformation has become higher as the overall damping has been enhanced due to the effect squeeze film damping. The consideration of higher order nonlinearities while modeling electrostatic forces, predicts more accurate response. This research gives a desirable insight of dynamic behavior of MEMS device under the influence of squeeze film effect. © 2016 The Authors.

World University root node

Fulltext

Procedia Engineering

Effect of Squeeze Film Damping and AC Actuation Voltage on Pull-in Phenomenon of Electrostatically Actuated Microswitch

The new generation super critical thermal power plants are required to operate at enhanced thermal efficiency of over 50% to reduce the fuel consumption and environmental pollution. Creep strength-enhanced ferritic steels, commonly known as Cr-Mo alloys such as P91 (X10CrMoVNb 9-1) are such material of choice for the next generation power plants. The operating requirement of these next generation power plants is that steam temperature of around 650 °C is maintained. For such high-temperature application, creep strength of material is the primary consideration together with adequate weld heat-affected zone (HAZ) toughness. Present work deals with the effect of high service temperature on impact toughness of P91 (X10CrMoVNb 9-1) base material, weld fusion zone, and HAZ. The impact toughness of HAZ for conventional weld groove design and narrow weld groove design has been evaluated experimentally in as-welded and at different post-weld heat treatment conditions. Fractography of the impact toughness specimens of base metal, weld fusion zone, and HAZ was carried out using scanning electron microscope. The effects of heat treatment schemes on the percentage of element present at the fracture surface were also studied. © 2016, ASM International.

Journal of Materials Engineering and Performance

Effect of Heat Treatment on Microstructure and Hot Impact Toughness of Various Zones of P91 Welded Pipes

Hydrogen-assisted cracking (HAC) is a serious issue in P91 steel welds because of unwanted martensitic metallurgical-transformation in the heat affected zone (HAZ). In the present research, different electrode conditions have been employed during welding of P91 steel to study their effects on HAC. The HAC susceptibility of cast and forged (C&F) P91 steel welds produced by shielded metal arc welding (SMAW) process has been evaluated through implant test with respect to the different level of diffusible hydrogen content in the deposited metal. The weld implant test results such as applied stress vs time to failure, the lower critical stress (LCS), embrittlement index (EI) and normalized critical stress ratio (NCSR) were evaluated with respect to the different level of hydrogen content in the deposited metal. The microstructure of coarse grain heat affected zone (CGHAZ) and weld metal in different condition have been characterized by using scanning electron microscope (SEM). The fracture morphology of implant specimen was characterized by using the SEM. The paper also describes the effect of hydrocarbon contamination (oil or grease) in low-hydrogen basic SMAW electrode for P91 steel. It can be concluded that P91 steel welded by the electrode having higher contamination (high hydrogen level) is more susceptible to HAC. The LCS value was observed to be decreasing with the increase in the diffusible hydrogen content in deposited metal and minimum value was measured to be 180 MPa for 12.54 ml of diffusible hydrogen per 100 g of deposited metal. © 2016 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Hydrogen induced cold cracking of creep resistant ferritic P91 steel for different diffusible hydrogen levels in deposited metal

The influence of the blade geometric parameters on the structural dynamic characteristics, response and loads of a helicopter rotor under hover condition in a whirl tower was investigated. A general geometry was considered for the rotor blade which included configuration parameters like root offset, torque offset, pre-twist, pre-cone, pre-droop, pre-sweep, tip-sweep and tip-anhedral. The option of placing concentrated masses at any location on the blade was also included. Natural frequencies and the corresponding mode shapes of the rotating blade were obtained by solving the linear, undamped structural dynamics model in the finite element domain. For calculating the response and loads on the rotor, the complete aeroelastic equation was solved in modal space. Aerodynamic models used in the aeroelastic loads calculations were Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. From the study, the blade structural dynamic characteristics are found to be sensitive to variation in blade geometric parameters. Tip-sweep was found to have significant effects on root oscillatory moments. The moments at the tip junction with the straight portion of the blade were found to be substantially affected by tip-sweep and tip-anhedral. Copyright © 2016 Royal Aeronautical Society.

Aeronautical Journal

Effects of blade configuration parameters on helicopter rotor structural dynamics and whirl tower loads

We introduce a piecewise-linear, volume-of-fluid method for reconstructing and advecting three-dimensional interfaces and contact lines formed by three materials. The new method employs a set of geometric constructs that can be used in conjunction with any volume-tracking scheme. In this work, we used the mass-conserving scheme of Youngs to handle two-material cells, perform interface reconstruction in three-material cells, and resolve the contact line. The only information required by the method is the available volume fraction field. Although the proposed method is order dependent and requires a priori information on material ordering, it is suitable for typical contact line applications, where the material representing the contact surface is always known. Following the reconstruction of the contact surface, to compute the interface orientation in a three-material cell, the proposed method minimizes an error function that is based on volume fraction distribution around that cell. As an option, the minimization procedure also allows the user to impose a contact angle. Performance of the proposed method is assessed via both static and advection test cases. The tests show that the new method preserves the accuracy and mass-conserving property of the Youngs method in volume-tracking three materials. © 2015 Elsevier Inc.

Journal of Computational Physics

A three-dimensional volume-of-fluid method for reconstructing and advecting three-material interfaces forming contact lines

This paper reports on miniaturized hydrogen sensing platforms, exploring several means of fabricating nanostructured films and evaluating their sensing characteristics. Palladium-sputtered nanoporous organosilicate matrices are fabricated using the polymeric system [polymethylsilsesquioxane (PMSSQ); polypropylene glycol (PPG); propylene glycol methyl ether acetate (PGMEA)] followed by volatilization of the liquid phase, i.e., PGMEA and PPG at their boiling points. In order to provide greater adsorption/desorption sites for the test gas, ultra-dense ZnO nano-brushes with very high aspect ratios are successfully fabricated in the porous template. Thereafter, functionalization of ZnO is performed by sputter coating thin Pd films onto the ZnO surface. Intensive characterization for these nanostructures is performed using FESEM, EDAX, FTIR, TEM and AFM techniques. Comparison of all fabricated sensing platforms for hydrogen gas-dependent responses based on temperature, as well as test gas concentrations at various ppm levels, is performed. Palladium coating of ZnO nano-brushes renders this film highly selective to hydrogen and also improves its sensitivity by a factor of ∼66% relative to the uncoated film. Sensitivity to hydrogen is found to be ∼70% and a selectivity test is performed with CO2 and CH4, with sensitivities of 5% and 7%, respectively. Pd-functionalized ZnO nano-brushes display enhanced hydrogen response behaviour. © 2016, © 2016 Author(s). Licensee InTech.

Nanomaterials and Nanotechnology

Palladium-Functionalized Nanostructured Platforms for Enhanced Hydrogen Sensing

Apart from micro- structure fabrication, ablation, lithography etc., lasers find a lot of utility in various areas like precision joining, device fabrication, local heat delivery for surface texturing and local change of microstructure fabrication of standalone optical micro-devices (like microspheres, micro-prisms, micro-scale ring resonators, optical switches etc). There is a wide utility of such systems in chemical/ biochemical diagnostics and also communications where the standalone optical devices exist at a commercial scale but chip based devices with printed optics are necessary due to coupling issues between printed structures and external optics. This paper demonstrates a novel fabrication strategy used to join standalone optical fibres to microchip based printed optics using a simple SU8 drop. The fabrication process is deployed for fiber to fiber optical coupling and coupling between fiber and printed SU-8 waveguides. A CO2 laser is used to locally heat the coupling made up of SU8 material. Optimization of various dimensional parameters using design of experiments (DOE) on the bonded assembly has been performed as a function of laser power, speed, cycle control, spot size so on so forth. Exclusive optical [RF] modelling has been performed to estimate the transmissibility of the optical fibers bonded to each other on a surface with SU8. Our studies indicate the formation of a Whispering gallery mode (WGM) across the micro-droplet leading to high transmissibility of the signal. Through this work we have thus been able to develop a method of fabrication for optical coupling of standalone fibers or coupling of on-chip optics with off-chip illumination/detection. © 2016, Springer Science+Business Media New York.

Lasers in Manufacturing and Materials Processing

High Efficiency Coupling of Optical Fibres with SU8 Micro-droplet Using Laser Welding Process

This paper presents a sampling-based method for path planning in robotic systems without known cost-to-go information. It uses trajectories generated from random search to heuristically learn the cost-to-go of regions within the configuration space. Gradually, the search is increasingly directed towards lower cost regions of the configuration space, thereby producing paths that converge towards the optimal path. The proposed framework builds on Rapidly-exploring Random Trees for random sampling-based search and Reinforcement Learning is used as the learning method. A series of experiments were performed to evaluate and demonstrate the performance of the proposed method. Copyright © 2016 by ASME.

Proceedings of the ASME Design Engineering Technical Conference

RRT-HX: RRT with heuristic extend operations for motion planning in robotic systems

This study analyses the effect of different fin geometries on the heat transfer and pressure loss characteristics of a fin and tube heat exchanger. A numerical investigation is carried out on liquid–gas type double-finned tube heat exchanger under cross-flow condition. Three different cross-sections namely: a) Rectangular, b) Trapezoidal, c) Triangular are adopted to define the fin geometry. The CFD simulations are performed to incorporate coupled steady state conjugate heat transfer with the turbulent flow phenomenon for the Reynolds number in the range of 5000-13000. Dimensionless heat transfer and pressure loss characteristics such as Nusselt number, Euler number, and efficiency index are determined and utilized to compare the performance of different fin geometries. The results obtained from the models are verified using experimentally developed correlations. The results obtained from the numerical models show that triangular fin geometry can provide higher heat transfer performance in comparison to the fins with rectangular and trapezoidal geometry with lower pressure loss and a bonus of 7.27% reduction in weight under similar operating conditions. © 2016 University of Ljubljana.

ECOS 2016 - Proceedings of the 29th International Conference on Efficiency, Cost, Optimisation, Simulation and Environmental Impact of Energy Systems

Performance study of a fin and tube heat exchanger with different fin geometry

Measurement of transient temperature and heat flux has attained enormous importance with the recent advancement in technology. Certain situations demand transient measurements to be performed for extremely short durations (approximately few seconds) which in turn call for sensors capable of responding within microseconds or even less. Thin-film gauges (TFGs), a particular class of resistance temperature detectors (RTDs), are such kind of sensors which are suitable for above requirements due to their quick and precise measurements in transient environments. The present work aims at designing an in-house fabrication and calibration of fast response TFG prepared by depositing nanocarbon layer on silver films as a laminated composite topping to enhance thermal and electrical properties. A significant improvement in the thermal and electrical conductivity of the composite sensor is observed when compared to gauges made from pure metals. © Copyright 2016 by ASME.