Faculty Publications
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Item A Bayesian inference approach: estimation of heat flux from fin for perturbed temperature data(Springer India, 2018) Kumar, H.; Gnanasekaran, N.This paper reports the estimation of the unknown boundary heat flux from a fin using the Bayesian inference method. The setup consists of a rectangular mild steel fin of dimensions 250×150×6 mm3 and an aluminium base plate of dimensions 250×150×8 mm3. The fin is subjected to constant heat flux at the base and the fin setup is modelled using ANSYS14.5. The problem considered is a conjugate heat transfer from the fin, and the Navier–Stokes equation is solved to obtain the flow parameters. Grid independence study is carried out to fix the number of grids for the study considered. To reduce the computational cost, computational fluid dynamics (CFD) is replaced with artificial neural network (ANN) as the forward model. The Markov Chain Monte Carlo (MCMC) powered by Metropolis–Hastings sampling algorithm along with the Bayesian framework is used to explore the estimation space. The sensitivity analysis of the estimated temperature with respect to the unknown parameter is discussed to know the dependency of the temperature with the parameter. This paper signifies the effect of a prior model on the execution of the inverse algorithm at different noise levels. The unknown heat flux is estimated for the surrogated temperature and the estimates are reported as mean, Maximum a Posteriori (MAP) and standard deviation. The effect of a-priori information on the estimated parameter is also addressed. The standard deviation in the estimation process is referred to as the uncertainty associated with the estimated parameters. © 2018, Indian Academy of Sciences.Item Corrosion protection of low-cost carbon steel with SS-309Mo and Inconel-625 bimetallic weld overlay(Institute of Physics Publishing helen.craven@iop.org, 2019) Mudha, A.A.; Shashikala, H.D.; Nagaraja, H.S.The dissimilar weld overlay coatings of components can lead to corrosion. In the present work, two different weld overlay layers (SS-309Mo and Inconel-625) are deposited on IS2062 grade B carbon steel, in order to avoid distortions and improve corrosion resistance. The microstructural investigations revealed that the intermediate layer SS-309Mo on carbon steel prevents the dilution by aiding crack-free weld overlay of Inconel-625 on the top. The corrosion behaviour of the coatings is studied using Linear Polarization Resistance and the Electrochemical Impedance Spectroscopy. The corrosion rate of the coatings decreased by two orders of magnitude compared to that of low carbon steel substrate. The corrosion rate of the deposited Inconel-625 along with intermediate SS-309Mo is 1.16×10-3 and is comparable to that of bare Inconel-625 (1.12×10-3 mmpy). Further, the immersion tests for 14 days show that, the depositions are stable with the formation of the passive film. ©2019 IOP Publishing Ltd.Item Effect of graphene oxide loading on plasma sprayed alumina-graphene oxide composites for improved anticorrosive and hydrophobic surface(IOP Publishing Ltd custserv@iop.org, 2019) Amudha, A.; Shashikala, H.D.; Asiq Rahman, O.S.; Keshri, A.K.; Nagaraja, H.S.Alumina is a widely used anticorrosive coating material for protection of metal surfaces. The graphene oxide (GO)-Alumina composite coatings can enhance the anticorrosion property of carbon steel surfaces used in an industrial scale. In the present work, the spray dried graphene oxide nanoplatelets of 0, 0.5, 1, 1.5 and 2 wt% reinforced alumina (?-Al2O3) were deposited on the low carbon steel substrate by Atmospheric Plasma Spray (APS) technique. The GO-Alumina nanocomposite coatings are characterised using XRD, FE-SEM, HR-TEM and Raman Spectroscopy. The electrochemical corrosion behaviour of the coatings on carbon steel has been examined using three electrode electrochemical method in 3.5 wt% NaCl electrolyte. A remarkable improvement in the corrosion resistance (with a corrosion current density of 0.01 nAcm-2) of about six orders with respect to pristine alumina was observed. The wettability tests revealed that, with 1.5 and 2 wt% graphene oxide nanoplatelets addition, the surface coating turned out to be hydrophobic with contact angle of 127°, from hydrophilic with contact angle 36°, which complements the anticorrosion results. The in situ reduction of GO to r-GO by APS deposition and bridging of alumina splats by the GO sheets accounts for observing the superior performance of the composite coatings. © 2019 IOP Publishing Ltd.Item Finite element analysis of thermal residual stresses in SS-309Mo and Inconel-625 multilayer weld deposition on low carbon steel(Elsevier Ltd, 2019) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.ANSYS Finite Element Analysis is adopted for simulation of SS-309Mo and Inconel-625 deposition in single and double layers, on IS-2062 Grade-B low carbon steel base metal. The Von-Mises residual stress distribution is obtained for twelve different combinations of weld deposition techniques and weld materials. Aim is to obtain a combination with minimum residual stress, using a technique of alternate skip weld deposition and base metal preheating. Also, the effect of change in the thickness of the base metal on coating residual stress is studied. The best model has 18 MPa surface residual stress. The very low values of residual stress obtained in the top layer of the multilayer deposition is helpful in preventing corrosion problems like stress corrosion cracking and corrosion fatigue, resulting in lower equipment downtime and losses to industry. © 2019 Elsevier LtdItem Multi-response optimization of the turn-assisted deep cold rolling process parameters for enhanced surface characteristics and residual stress of AISI 4140 steel shafts(Elsevier Editora Ltda, 2020) Prabhu, P.R.; Kulkarni, S.M.; Sharma, S.Surface and near-surface areas play an important role as far as safety and dependability ofengineering components particularly when it is subjected to fatigue loading. By applyingdiverse mechanical surface enhancement (MSE) strategies, close to surface layers can becustom-made bringing about enhanced fatigue strength. MSE methods are used to gener-ate surface hardened components without the time and energy-consuming heat treatment.Deep cold rolling (DCR) is one such method that can be employed where the mechanicalenergy induced enables surface-hardening of steels and thereby the combination of hard-ening and finishing in one single step. The objective of this work is to enhance residualstress and near-surface properties of AISI 4140 steel which is the most commonly usedmaterial in the automobile and aerospace industry. The samples were first turned and thendeep cold rolled with various process parameters. Microstructure, surface hardness, sur-face finish, fatigue life, and residual compressive stress after the treatment were examined.Response surface methodology (RSM) and desirability function approach (DFA) was used torelate the empirical relationship between the various process variables and responses andalso to determine the optimum parameter settings for better responses. Further, numericalsimulation of turn-assisted deep cold rolling (TADCR) process was done by utilizing ANSYS-LS-DYNA software to understand the state of residual stress under various treating settings.Confirmation experiments conducted with the optimum parameter setting to validate theimprovements in response and it is found that the deviation between optimum predictedand confirmatory experimental values is about 5%. © 2020 The Authors.Item Characterization and Sliding Wear Behavior of Iron-Based Metallic Coating Deposited by HVOF Process on Low-Carbon Steel Substrate(Springer, 2020) Prasad, C.D.; Jerri, A.; Ramesh, M.R.The main aim of this work is to improve the sliding wear resistance of boiler steel material. The iron-based or Metco 41C metallic feedstock was deposited over the ASTM-SA213-T11 steel substrate using high-velocity oxy-fuel spraying process. The resultant deposits were subsequently characterized for microstructure, density, hardness, porosity and surface roughness. These characterizations were carried out with the help of XRD, SEM and Vickers’s microhardness tester. The sliding wear performance of the substrate and coatings were investigated by varying normal loads of 10 N and 20 N at temperatures of 200 °C, 300 °C as well as room conditions by employing pin-on-disk tribometer. The friction coefficient, volume of wear loss and wear rate were being found out. The wear results were compared among the substrate and coating. The formation of additional carbide phases such as Fe2C and SiC in Metco 41C coating led to higher hardness results in better wear resistance compared with the substrate. © 2020, Springer Nature Switzerland AG.Item Surface Properties and Corrosion Behavior of Turn-Assisted Deep-Cold-Rolled AISI 4140 Steel(Springer, 2020) Prabhu, P.R.; Prabhu, D.; Sharma, S.; Kulkarni, S.M.In this research, the effect of various turn-assisted deep-cold-rolling process parameters on the residual stress, microstructure, surface hardness, surface finish, and corrosion behavior of AISI 4140 steel has been investigated. The examination of the surface morphology of the turned and processed samples was performed by using a scanning electron microscope, energy-dispersive spectroscopy, and atomic force microscopy. Response surface methodology and desirability function approach were used for reducing the number of experiments and finding local optimized conditions for parameters under the study. The results from the residual stress measurements indicate that the rolling force has the highest effect by generating a deeper layer of residual compressive stress. The outcomes of surface hardness and surface finish emphasize that rolling force and number of tool passes are the most significant parameters affecting the responses. Surface studies confirmed the corrosion and its intensity onto the metal surface, and according to atomic force microscopy studies, the surface had become remarkably rough after exposure to the corrosive medium. Improvements in surface microhardness from 225 to 305.8 HV, the surface finish from 4.84 down to 0.261 ?m, and corrosion rate from 6.672 down to 3.516 mpy are observed for a specific set of parameters by turn-assisted deep-cold-rolling process. The multiresponse optimization for surface finish and corrosion rate together shows that a ball diameter of 10 mm, a rolling force of 325.75 N, initial roughness of 4.84 µm, and number of tool passes of 3 give better values for the two responses under consideration with composite desirability of 0.9939. Based on the experimental work at the optimum parameter setting, the absolute average error between the experimental and predicted values for the corrosion rate is calculated as 3.2%. © 2020, The Author(s).Item Electrochemical studies on the corrosion resistance of Zn–Ni–Co coating from acid chloride bath(Springer, 2020) Bhat, R.S.; Manjunatha, K.B.; Prasanna Shankara, R.; Venkatakrishna, K.; Hegde, A.C.Anticorrosive deposits are a valuable approach to defending against corrosion from mild steel structures/machinery equipment. The Zn–Ni–Co coating has been deposited on low carbon steel surfaces using environment friendly optimized acidic chloride bath with ZnCl2·6H2O, NiCl2·6H2O, CoCl2·6H2O, sulphanilic acid (C6H7NO3S) and gelatin (C6H8O6). The standard Hull cell technique has been adopted for the optimization of bath components and experimental conditions, for the superior corrosion resistant coating. The corrosion test with potentiodynamic polarization method was performed to investigate the role of pH on the film quality and corrosion performances of the films. Further, the effect of current densities on corrosion resistance, thickness and hardness, have been investigated. Cyclic voltammetry technique has been used to test the electrochemical properties of the Zn–Ni–Co coating in acidic solutions. The results revealed that the increase in the current density favoured the increase in Ni and Co content in the deposit, showed higher corrosion resistance and higher cathodic current efficiency. The structural and morphological characteristics of the alloy coating have been obtained through scanning electron microscopy and X-ray diffraction techniques. The atomic force microscope was used to examine the topographic structure of the coating. X-ray Photoelectron spectroscopy was used to determine the chemical composition of alloy coatings and verified by energy dispersive X-ray analysis. The results indicate that a new and low-cost chloride bath for Zn–Ni–Co coating exhibit superior corrosion resistance properties and can be implement in various industrial applications such as automobiles, machine tools etc.[Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Evaluation of artificial neural network in data reduction for a natural convection conjugate heat transfer problem in an inverse approach: experiments combined with CFD solutions(Springer, 2020) Kumar, M.K.H.; Vishweshwara, P.S.; Gnanasekaran, N.In this work, natural convection fin experiments are performed with mild steel as the fin and an aluminium plate as base. The dimension of the mild steel fin is 250 mm × 150 mm × 6 mm and the aluminium base plate is 250 mm × 150 mm × 8 mm. A heater is provided on one side of the aluminium base plate and the mild steel fin emerges on the other side of the plate. The heater provides required heat flux to the fin base; several steady-state natural convection experiments are performed for different heat fluxes and corresponding temperature distributions are recorded using thermocouples at different locations of the fin. In addition, a numerical model is developed that contains the dimensions of the fin set-up along with extended domain to capture the information of the fluid. Air is treated as a working fluid that enters the extended domain and absorbs heat from the heated fin. The temperature and the velocity of the fluid in the extended domain are obtained by solving the Navier–Stokes equation. The numerical model is now treated as a forward model that provides the temperature distribution of the fin for a given heat flux. An inverse problem is proposed to determine the heat flux that leads to the temperature distributions during experiments. The temperature distributions of the experiments and forward model are compared to identify the unknown heat flux. In order to reduce computational cost of the inverse problem the forward model is then replaced with artificial neural network (ANN) as data reduction, which is developed using several computational fluid dynamics solutions, and the inverse estimation is accomplished. The results indicate that a quick solution can be obtained using ANN with a limited number of experiments. © 2020, Indian Academy of Sciences.Item Thermomechanical Simulation of Ferritic Rolling of Titanium-Niobium Interstitial-Free Steel(ASTM International, 2021) Satish Kumar, D.; Sambandam, S.; Kuruveri, U.B.Austenitic or two-phase rolling of ultra-low carbon steels face temperature control issues and generate shape defects. Ferritic rolling has been developed as a solution, and ferritic hot-rolled sheets are used as final products, replacing hot-rolled followed by cold-rolled sheets. However, it is not in regular industrial production because of mill limitations. Hence, ferritic hot rolling must be optimized for developing a ferritic cold-rolled and close-annealed sheet through subsequent processing. In this work, industrial ferritic rolling process was simulated for a titanium-niobium interstitial-free steel using a thermomechanical simulator. Multi-hit plane strain compression tests were carried out at three different regimes below the lower transformation temperature (Ar1). Steels were processed under high strain and strain rates as experienced during industrial hot rolling operation, and the results were compared with the conventional austenitic rolling. The flow stress of the material in the ferritic regime decreased with decreasing deformation temperatures but increased at temperatures below 700°C. Nonuniformity in grains and texture also increased with decreasing temperatures. High-temperature rolling in ferritic condition close to Ar1 temperature does not differ significantly from the austenitic condition, whereas the low-temperature ferritic rolled material had through-thickness microstructural nonuniformity and unwanted goss and brass fibers. The intensity of gamma-fiber {111}