Department of Mechanical Engineering

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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.

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IIT Jodhpur

Preventing nosocomial infection is a major unmet need of our times. Existing air decontamination technologies suffer from demerits such as toxicity of exposure, species specificity, noxious gas emission, environment-dependent performance and high power consumption. Here, we present a novel technology called “ZeBox” that transcends the conventional limitations and achieves high microbicidal efficiency. In ZeBox, a non-ionizing electric field extracts naturally charged microbes from flowing air and deposits them on engineered microbicidal surfaces. The surface’s three dimensional topography traps the microbes long enough for them to be inactivated. The electric field and chemical surfaces synergistically achieve rapid inactivation of a broad spectrum of microbes. ZeBox achieved near complete kill of airborne microbes in challenge tests (5–9 log reduction) and > 90 % efficiency in a fully functional stem cell research facility in the presence of humans. Thus, ZeBox fulfills the dire need for a real-time, continuous, safe, trap-and-kill air decontamination technology. © 2021, The Author(s).

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Scientific Reports

Novel non intrusive continuous use ZeBox technology to trap and kill airborne microbes

Abstract: The COVID-19 global pandemic has caused a profound change in the teaching pedagogies and assessment strategies in engineering curricula worldwide. Concerning this, the article examines the role of animation-enhanced concept-in-context maps as a learning resource for the introductory materials science course in an online flipped format. The research was conducted on second-year mechanical engineering undergraduates. The methodology used two-group quasi-experimental design where the experimental group received animated concept-in-context maps as a learning resource, in contrast to the control group, which obtained static concept-in-context maps. The student's understanding of the topic was evaluated from their performance in pre-quiz and post-quiz scores. The preliminary results of the pilot study turned out to be in favor of animation-assisted mapping; further research is in process, and in-depth experimentation has been planned. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to The Materials Research Society.

MRS Advances

Animated concept-in-context maps as a materials science learning resource in an online flipped classroom

Parabolic dish concentrator-based solar cooker is a highly promising alternative green technology capable of providing clean energy solution for wide varieties of domestic and commercial culinary requirements. Since a significantly high temperature range of 250–350 °C can be easily obtained adjacent to the focal region of the parabolic concentrator, the technology is suitable for a wide variety of cooking involving grilling, frying, simmering, and boiling. The utilization of solar energy for domestic or commercial cooking also reduces dependence on fossil fuels, resulting in lower carbon footprints. However, a major limitation of the existing forms of such solar cookers is associated with the duration and availability of solar irradiation, which renders the system active only during the on-sun period. The inaccessibility of solar radiation for cooking before sunrise and after sunset can only be addressed by incorporating effective thermal energy storage (TES) systems in conjunction with parabolic dish reflectors. The development of a compact storage cooking unit involving latent heat thermal energy storage (LHTES) might play a crucial role to overcome this severe limitation. Phase change material (PCM) with suitable melting point and large latent heat of fusion can be considered as an ideal thermal energy storage medium for household or commercial cooking applications. The usage of PCM as the thermal energy storage medium also enables the storage system to deliver heat at a narrow band of temperature during the cooking. Thermal energy is stored during the melting of PCM, and the process is defined as charging of LHTES system. The stored heat can be extracted during the cooking involving heat flow from the molten PCM to the cooking unit rendering gradual solidification of the storage medium. Although phase change materials (PCM) seem to be an ideal thermal storage medium, one of the major concerns associated with them is their low thermal conductivity (0.25–0.5 W/mK). Potential phase change materials with melting temperature close to 300 °C are mostly inorganic salts in pure or multicompositional forms, having low thermal conductivity. As a result, charging duration involving complete melting process of the PCM might end up getting extended beyond a feasible time span of solar irradiation. Low thermal conductivity of storage medium also causes undesirable steep thermal gradient within the storage unit. Therefore, thermal conductivity enhancement of the PCM is of utmost importance. Usage of PCM-CEG (CEG: compressed expanded graphite) composite to enhance the thermal conductivity of the latent heat storage medium is explored and found to be a promising solution. The present chapter is aimed at providing a detailed feasibility study of solar cookers containing LHTES integrated with parabolic concentrator. Numerical studies are performed to analyze the heat transfer phenomena in PCM-CEG composite embedded inside the thermal storage container with and without circumferentially oriented radial fins. Enthalpy updating scheme addressing the inclusion of CEG matrix embedded within PCM has been adapted for the numerical prediction of melt fraction within the LHTES. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Energy, Environment, and Sustainability

Parabolic Dish Solar Cooker: An Alternative Design Approach Toward Achieving High-Grade Thermal Energy Storage Solution

Autonomous on-orbit servicing, such as capture, refuel, repair and refurbishment of on-orbit satellites using a robotic arm mounted on servicing satellite is one of the important components of future's space missions. Space robots increase reliability, safety, and ease of execution of space operations, but pose a novel challenge due to micro-gravity and space environments. While capturing high speed orbiting objects, robotic arms undergo impact and require appropriate modeling of the system. In this paper, a unified framework is provided for modeling impact dynamics, post-capture stabilization and target maneuvering of a multi-arm robotic system mounted on a servicing satellite while capturing orbiting objects. The dynamic model of multi-arm space robot is obtained using the Decoupled Natural Orthogonal Complement (DeNOC) based formulation and closed-loop constraint equations. All three phases of the capturing operation, namely, approach, impact, and post-impact are modeled using Impulse-momentum approach and conservation of momentum. In the approach phase, robot arms are planned to move from its initial configuration to the desired capture configuration. In the impact phase, a framework is developed to estimate the impulse forces and changes in the generalized velocities caused by the impact. In post-impact phase, these velocities are used as initial conditions for the post-impact dynamics simulations. The uncontrolled dynamics during post-impact will result in an undesirable motion, thus post-impact reactionless control (minimum base disturbance) strategy is used to maneuver the space robot's arms and target object. As such, the robotic arms can be used to maneuver an astronaut for repair of satellite. Most of the times the parameters of target object are not known. Hence, an adaptive reactionless control strategy has been devised for capturing object with unknown parameters. The effectiveness of the framework is shown using a dual-arm robot mounted on a servicing satellite performing capturing operation for multiple objects. The effects of relative velocity and angle of approach on the impact forces are also investigated. © 2021 IAA

Acta Astronautica

Impact modeling and reactionless control for post-capturing and maneuvering of orbiting objects using a multi-arm space robot

The ability to drill smaller size holes down to micron level is a challenging task in many industries that manufacture high-tech products. Due to restriction in the tool size existing in conventional manufacturing, non-conventional approaches are being adopted to meet the challenges related to miniaturization. Laser sources have emerged as a clean source of energy for microfabrication techniques. In this work, micron level holes in the polyethylene terephthalate (PET) substrate are fabricated with fiber laser machining arrangement. Design of experiments (DOE) was used to perform the experiments giving equal weightage to all the input variables and the results were analysed through analysis of variance (ANOVA) to develop the optimization model. Experiments have been performed while taking power, frequency, pulse on time and cycle time as process parameters and hole diameter and heat affected zone (HAZ) as output parameters. Further, a mathematical model has also been developed and simulated for the hole fabrication through laser as the energy input. The experiment conducted using the optimized parameters resulted in hole diameter of 457 mu m and HAZ thickness of 284 mu m.

LASERS IN ENGINEERING

Laser-assisted Microhole Fabrication in a Flexible Polymer Substrate

The dissimilar welds joint of 2.25Cr-1Mo steel and lean duplex LDX2101 steel was prepared using the Gas Tungsten Arc Welding (GTAW) process and employing the Inconel 617 filler. The microstructural stability of the dissimilar welds joint (DWJ) was studied using the optical microscope and field emission scanning electron microscope (FESEM) for as-welded (AW) and post-weld heat treatment (PWHT) condition. The PWHT was employed at 760 degrees C (PW 1) and 810 degrees C (PW 2) for 2 h of duration. The application of the heat-treatment resulted in the formation of the soft zone at the interface of weld metal and HAZ in 2.25 Cr-1Mo side, i.e., low Cr side. The mechanical behavior of the DWJs was also studied for AW and PWHT condition. A measurable change in the width and hardness of the soft and hard zones was measured with an increase in PWHT temperature. For weld metal, the minimum average hardness was measured 237 HV in AW and a maximum of 248 HV for PW 2. In the AW condition, the average CIT of the weld metal was measured 46.5 +/- 3.5 J, which meets the minimum recommended value as per EN 1557:1999 standards. The PWHT showed a drastic reduction in CIT and a minimum of 34 +/- 3 J was measured for PW 2. The CIT of the 2.25Cr-1Mo HAZ (notch adjacent to fusion boundary includes the soft ferrite region) was measured 45 +/- 5 J in AW and get increased drastically after the PWHT and maximum was measured for PW 2 (86 +/- 5 J).

FUSION ENGINEERING AND DESIGN

Characterization of the soft zone in dissimilar welds joint of 2.25Cr-1Mo and lean duplex LDX2101 steel

The microstructure and mechanical behavior of the Gas Tungsten Arc (GTA) welded joint of ferritic/martensitic (F/M) P91 and austenitic SS304L steel was investigated in as-welded and post-weld heat treatment (PWHT) conditions. The microstructural studies included the particle size and its distribution, grain size, and percentage area fraction of the precipitates (%AFP) in different zones of the weldments. In as-welded condition, weld metal showed untempered martensitic microstructure devoid of carbide precipitates. After the PWHT, weld metal was characterized by tempered martensitic microstructure along with the decoration of the coarse carbide particles at PAGBs and fine carbonitride particles inside the matrix region. The mechanical behavior of the dissimilar weld was analyzed in as-welded and PWHT conditions by performing tensile testing, Charpy impact testing, and microhardness testing. A significant variation in microstructure and mechanical properties was obtained across the dissimilar welded joint (DWJ) for as-welded, which was minimized after the PWHT. The minimum%AFP in the coarse grain heat-affected zone was measured due to the formation of the precipitate-free soft δ ferrite patches, which also showed a negligible response to PWHT. The poor Charpy impact toughness (CIT) of 0.8 ± 1.5 J and high tensile strength of 864 ± 12.5 MPa were measured for the as-welded joint. The combination of high strength and low CIT was obtained mainly due to the untempered martensitic microstructure in the weld fusion zone. The DWJ after the PWHT showed a significant increase in Charpy impact toughness (CIT), and it was measured 70 ± 4 J. Improved mechanical behavior with a good combination of ultimate tensile strength and CIT were obtained after the PWHT. © 2021 Elsevier B.V.

Fusion Engineering and Design

Role of the heterogeneity in microstructure on the mechanical performance of the Autogenous Gas Tungsten Arc (GTA) welded dissimilar joint of F/M P91 and SS304L steel

In the present experimental work, an attempt has been made to investigate the effect of filler metal on solidification, microstructure, and mechanical properties of the dissimilar weld between super duplex stainless 2507 and high strength low alloy API X70 pipeline steel. This joint is widely used in offshore hydrocarbon drilling risers and oil-gas transportation pipelines. Welds have been fabricated by the gas tungsten arc welding process using super duplex 2594 and austenitic 309L grade filler. A comparative assessment of both the fillers has been done by investigating multiple aspects of weld's structural integrity. 309L fillers weld has skeletal ferrite morphology, whereas 2594 filler solidifies with precipitation of multiple reformed austenites in the ferrite matrix. Lower width unmixed zone is formed on the API X-70 side in 2594 filler as compared to 309L. The tensile and impact strength of 309L filler weld is superior to 2594 filler. Precipitation of reformed austenite in the weld zone leads to lower hardness in 2594 as compared to skeletal ferrite dominated 309L weld zone. High chromium concentration in the weld zone results in superior pitting corrosion resistance of 2594 filler. © 2020 Elsevier B.V.

Materials Science and Engineering A

Effect of filler metal on solidification, microstructure and mechanical properties of dissimilar super duplex/pipeline steel GTA weld

The present paper aims at the material design for wind turbine blade that can sustain different environmental conditions. It is difficult to keep regular maintenance of blade; we need to design a material that can repair the damage by its own. The present work is an attempt to study the effect of moisture, temperature and saline medium on glass fiber-reinforced polymer (GFRP) having Cloisite 30B (nanoclay) as reinforcement in epoxy polymer matrix. The changes in the physical and mechanical properties of the composite material under accelerated condition have been studied. The concept of self-healing is a vital tool to encounter the damage by itself. We have used DCPD (dicyclopentadiene)-contained microcapsules as a healing agent. These microcapsules have shown a great decrease in the rate of degradation of blade material. Wind turbine blades are mainly made up of FRP composites, and these composites have tendency to absorb moisture. It has been observed that water absorption can affect the mechanical performance as well as reduce the durability of turbine blade. To encounter this effect, nanoclay as filler has been used in GFRP composites. It has been noticed that degradation reduces to high extent. The percentage reduction in strength is more in saline water than in normal tap water. Epoxy samples show more degradation in saline medium (39-46\%) at 40 degrees C as compared to plain water medium (29-41\%) at the same temperature.

TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS

Environmental Degradation of Glass Fiber-Reinforced Nanocomposites with Self-Healing Reinforcement in Polymer Matrix for Wind Turbine Blade Application