Department of Mechanical Engineering

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IIT Jodhpur

A continuum mixture model is proposed for phase change of binary alloy including the effect of thermal anisotropy. Thermal anisotropy is incorporated by an additional departure source in the conventional isotropic heat transfer-based energy equation. The governing equations for heat, mass, momentum, and species transport are solved using implicit finite volume method. The pressure and velocity in the momentum equation are coupled using SIMPLER algorithm. The solute mixture concentration is updated using two commonly used methods, the lever rule model and the Scheil rule model. A comprehensive study is made to investigate the effect of thermal anisotropy on solidification physics and final macrosegregation pattern after complete solidification for two cases: one with three sides of the enclosure insulated where planar front generates and the other with two opposite sides insulated where irregular front evolves. The directional effect of thermal anisotropy ratio (AR) on binary alloy phase change behavior has been investigated in detail. © 2020, © 2020 Taylor & Francis Group, LLC.

World University root node

Numerical Heat Transfer, Part B: Fundamentals

Thermal anisotropy in binary alloy solidification: An equivalent isotropic model

The present study focuses on the thermodynamic analysis of zeolite–water and activated carbon–ethanol based adsorption cooling systems. The performance of the system depends critically on four operating temperatures namely maximum desorption temperature, minimum adsorption temperature, condensing temperature, and evaporating temperature and also on the ratio of specific heat of structural material and the specific heat of adsorbent. Dubinin–Astakhov equation is used to estimate the equilibrium uptake of working pairs. A comparative study is made between these working pairs for the air-conditioning applications. © 2020, Springer Nature Singapore Pte Ltd.

Energy, Environment, and Sustainability

Thermodynamic Analysis of Activated Carbon–Ethanol and Zeolite–Water Based Adsorption Cooling Systems

The application of data-driven or machine learning models is becoming imperative in recent times to analyze manufacturing process attributes. These models use input and output datasets to evolve the relationship similar to human perceptions. The development of a reliable data-driven model is challenging due to the necessity of conducting numerous experiments, the presence of outliers and noise in the datasets, process disturbances, etc. The data-driven models can be scaled easily by accommodating new variables and attributes to evolve progressively. Alternatively, physics-based models establish an explicit relationship between process variables and desirable attributes based on scientific knowledge and a set of assumptions, but its scalability is difficult. This paper presents the development of a hybrid cutting force model for end milling operation, combining both approaches to ensure that adequate process knowledge is captured. The outcomes of the proposed method are substantiated by performing a set of computational studies and end milling experiments. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 53rd CIRP Conference on Manufacturing Systems

Fulltext

Procedia CIRP

Amalgamation of physics-based cutting force model and machine learning approach for end milling operation

This paper presents the design, development and testing of a novel neck chamber device for non-invasive stimulation of an individual carotid baroreceptor in a graded manner. The proposed neck chamber device is a strap-free design that avoids discomfort during testing due to tight seal generated by the neck collar design, and facilitates unilateral testing and targeted assessment without stimulating other neck baroreceptors. The device consists of two independent components to achieve these requirements: an outer suction mechanism and an inner chamber. The outer mechanism consists of multiple suction cups to grip the device over the human neck, while the inner chamber creates controlled positive and negative pressure for stimulation of baroreceptors using a pump. The indigenously developed device was employed for the testing by providing neck chamber stimulation in discrete steps of -20 mm Hg, -40 mm Hg, -60 mm Hg, 0 mm Hg, 20 mm Hg, 40 mm Hg and 60 mm Hg with the gap of 60 s between each stimulation as per the standard test protocol of autonomic function test. The changes in heart rate and RR interval were recorded to determine the baroreceptor gain using the logistic equation derivative and gain curve plot. The results of the present study show that the estimated baroreceptor gain is -0.109±0.04, which is consistent with the previous studies conducted using neck collar devices. The testing results showed that the desired objectives are achieved successfully by the prototype device, opening up the possibility of its use for the treatment of resistant hypertension. © 2020 Author(s) (or their employer(s)). No commercial re-use. See rights and permissions. Published by BMJ.

BMJ Innovations

Preliminary design and testing of neck chamber device for baroreflex sensitivity assessment

This paper presents a comparative assessment of three different approaches to highlight the importance of incorporating bottom and flank cutting edges in cutting force models for flat-end milling operation. The study focuses on identifying the most appropriate method that includes the effect of both cutting edges and predicts accurately over a wide range of cutting widths, i.e., axial depth of cut (ADOC) and radial depth of cut (RDOC). The first approach uses the average cutting constants directly estimated from the experimental force data. The second approach pre-processes the experimental data to exclude the contribution of bottom edges and determine flank constants for the estimation of cutting forces. The third approach considers the systematic derivation of independent coefficients for flank and bottom cutting edges and summing the individual contribution to determine cutting force. These approaches are implemented in the form of computational models, and machining experiments are conducted to examine the efficacy of proposed methods in estimating cutting force for flat-end milling operation. Based on the outcomes of the study, it is realized that the third approach can predict cutting forces accurately over a wide range of cutting widths. Also, it is observed that the bottom edge has a marked effect on the normal force component for select combinations of cutting widths. © 2020, Springer-Verlag London Ltd., part of Springer Nature.

International Journal of Advanced Manufacturing Technology

Importance of bottom and flank edges in force models for flat-end milling operation

We report an experimental study of evaporation from a non-homogeneous dual porous system consisting of a finer pore size material at the centre surrounded by coarser particles in a glass beaker. This configuration can be considered to mimic, to a first order, the coupling between the plant roots and soil water. Similar to how roots extract water from the soils, here also water moves, driven by the capillary pressure gradient, from larger to the smaller voids. We explore two different configurations (a) when the small pore sizes span the entire porous column along the gravitational direction and (b) when they are limited to a thin annular region at the porous medium top surface. We measured the mass loss from the system, surface temperature using a thermal camera, and the ambient conditions. We compared the results with two standard systems – (a) a homogeneous porous medium and (b) a texturally layered configuration of finer particles at the top and coarser at the bottom. Compared to the homogeneous case, the duration of stage 1 (high evaporation rate regime) of evaporation and thus the characteristic evaporative length increased significantly in the case of root-mimics; this outcome shows the ability of the root-mimics in sustaining the surface water content induced by the strong capillary pressure gradient in such a dual porosity system. Finally, we track the evaporation sites using the fluorescein dye particles method and assess its effect (if any) on the overall evaporation characteristics. © 2019 Elsevier B.V.

Agricultural Water Management

Mimicking some features of a root-soil system by dual porosity media

The purpose of this investigation was to quantify the effects of intermetallic and secondary phases on the sliding wear behavior of super duplex stainless steel 2507 against bearing steel type EN-31 under both dry and wet contact conditions. Phases were precipitated by suitable heat treatment in the range of 475–875 °C. A pin-on-disc technique was used to investigate the wear characteristics in the wet environment of 3.5% NaCl solution, 1 M HCl solution, 10−2 M sodium thiosulfate solution, and artificial ocean water. These media were chosen to closely match the actual service environment of super duplex stainless steel 2507. Pins were slid against a disc of EN-31 steel for distances of 1,000, 1,500, 2,000, 2,500, and 3,000 m. Results indicate that precipitation of the sigma phase gives the best wear resistivity, followed by precipitation of chi and R phases and then precipitation of the α′ phase. The experimental investigations reveal that hydrogen in acidic medium accelerates the reaction kinetic compared to the neutral medium because of the different cathodic reactions. Progressive wear was closely observed using the change in the sliding pin’s contact face profile and corresponding weight loss data. Scanning electron microscopy was used to study the wear mechanism. © 2020, © 2020 Society of Tribologists and Lubrication Engineers.

Tribology Transactions

Effect of Intermetallic and Secondary Phases on Dry and Wet Sliding Wear Behavior of Super Duplex Stainless Steel

Offshore structures in recent time are witnessing the increased application of dissimilar metal welds for enhanced structural integrity. Offshore structures are complex systems. Fabrication, maintenance, and repair of these structures require conventional and advanced welding technologies along with suitably chosen welding consumables. The present work aims at the design and development of shielded metal arc welding (SMAW) electrode coating using extreme vertices design methodology. This work also attempts to study weld metal chemistry along with microstructure and microhardness. Red ochre, a mineral waste from iron ore is added in the coating composition. Multi response optimization has been carried out to obtain optimum flux composition and to study the effect of individual constituents and their interactions on the weld chemistry and microhardness. © 2020 American Society of Mechanical Engineers (ASME). All rights reserved.

Journal of Pressure Vessel Technology, Transactions of the ASME

Weld Metal Chemistry of Mineral Waste Added SiO2-CaO-CaF2-TiO2 Electrode Coatings for Offshore Welds

This article is an attempt to examines high-temperature wettability properties of laboratory-developed electrode coatings for power plant applications. The properties include contact angle between the solid/liquid interfaces, spreading area, surface tension, and work of adhesion. Coatings were prepared using CaO-CaF2-SiO2 -Al2O3 basic flux system. The sessile drop method was used to estimate the contact angle at the liquid/solid interface while surface tension was calculated using Young’s and Boni’s equations based on the measured contact angle. The interaction effect of individual minerals and their binary mixtures (CaO.CaF2, CaO.SiO2, CaO.Al2O3, CaF2.SiO2, CaF2.Al2O3, and SiO2.Al2O3) on the wettability properties were studied using the regression analysis. Optimum flux compositions were estimated using Multi-response optimization. The contact angle decreases when basic oxides (CaO, CaF2) were added in a higher proportion than the acidic oxides. With the decrease in the contact angle spreading area increased and CaF2 comes out to be the significant constituent causes the increase in the spreading area. Binary mixtures CaO.CaF2, CaO.SiO2, and CaF2.SiO2 has an increasing effect on the work of adhesion. © 2020, Springer Nature B.V.

Silicon

High-Temperature Wettability Investigations on Laboratory-Developed CaO-CaF2-SiO2 -Al2O3 Flux System-Based Welding Electrode Coatings for Power Plant Applications

In the present study, the thermo-physical properties of twenty-one submerged arc welding slags were analyzed using a rutile-basic system. The submerged arc welding slags were analysed using hot-disc and thermogravimetric techniques. Thermo-gravimetric analysis was performed from 25 °C to 900 °C to find the thermal stability and change in enthalpy of the slags. Multi-response optimization technique was used to derive the optimized slag formulations. Different regression models for thermo-physical properties were developed. Individual slag constituents have an antisynergistic effect on all the thermophysical properties except density. Binary and ternary slag mixture constituents significantly affect the thermophysical properties of submerged arc welding slag. © 2019, Springer Nature B.V.