Faculty Publications

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    Effect of Porosity Distribution on Vibration and Stability Characteristics of FGM Plates Subjected to Nonlinearly Varying Edge Loads
    (Springer Science and Business Media Deutschland GmbH, 2023) Swaminathan, K.; Hirannaiah, S.; Rajanna, T.
    In this article, the consequences of porosity type of imperfection on vibration and stability characteristics of Functionally Graded Material (FGM) plate members are examined. Since it is challenging to predict the type of porosity distribution in the plate, four diverse varieties of porosity distributions varying through the thickness are considered during the modelling of FGM plates. The porosity effect is included in material modelling by means of modified rule of mixture. The in-plane edge loads acting on plates are seldom uniform in nature during the operational condition. And hence, vibration and stability characteristics of the FGM plates comprising porosity is analyzed considering nonlinearly varying in-plane edge load incorporating Finite element (FE) method. The numerical outcomes obtained are compared to those reported in the literature to help decide the formulation's correctness. The effect of geometric configuration, volume fraction exponent, porosity and loading on vibration and stability characteristics of FGM plate member with porosity is investigated. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.
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    Influence of Porosity and Temperature Load on Buckling Characteristics of Functionally Graded Material Plates
    (Springer, 2024) Swaminathan, K.; Hirannaiah, H.; Rajanna, T.
    Functionally graded material (FGM) plate is usually exposed to a thermal environment, and their mechanical behaviour under temperature loads is of great importance to the research community. Therefore, the objective of the current investigation is to study the impact of porosity and temperature loads on the buckling characteristics of FGM plates. The effective material properties of porous FGM plates are found using modified power law distributions, and the porosity defects are accounted for in this study as criteria of stiffness reduction. The buckling responses of porous FGM plates are investigated by incorporating four types of different porosity distributions. The analysis is carried out using the Finite Element (FE) technique. The accuracy of the current formulation is authenticated by comparing the present results obtained with analytical results existing in the literature. After the validation, the influence of several significant parameters such as the porosity, the volume fraction exponent, side-thickness ratio, support conditions and aspect ratio on buckling responses of the porous FGM plate under temperature loads is evaluated. Results showed that the buckling response of the FGM plate is substantially affected by porosity and temperature loads. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Effect of Process Parameters on Track Geometry and Porosity in Laser Direct Energy Deposition of High Strength Aluminum Alloy
    (Springer, 2024) Balla, S.K.; Manjaiah, M.; Selvaraj, N.; Bontha, S.
    Laser Directed Energy Deposition (LDED) is a metal Additive Manufacturing (Metal AM) process that has attracted significant attention due to its ability to produce complex geometries with material properties comparable to cast and wrought parts. High-strength aluminum alloys especially 2xxx, 6xxx, and 7xxx series are difficult to fabricate using LDED process since these alloys are prone to hot cracking due to rapid solidification during the LDED process. The focus of this work is to evaluate the effect of LDED process parameters on track geometry and porosity of Al7075 powder. The effects of process parameters such as laser power, scan speed, and powder flow rate on track geometry and porosity, were investigated using a Formalloy LDED machine via L27 orthogonal array of experiments. Increasing the laser power resulted in an increase in bead width and wetting angle, whereas increasing the scan speed led to a decrease in bead height and wetting angle and a minor increase in width. The results also showed a linear increase in wetting angle and bead height with increased powder flow rate, while the width of the bead remained relatively constant. Furthermore, it was also observed that increasing the laser power to 750 W resulted in a decrease in the cross-sectional porosity of the bead due to the availability of sufficient energy density thereby facilitating proper melting. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    Wave transformation due to a submerged porous block associated with a vertical barrier
    (Springer, 2020) Krishna, K.R.A.; Venkateswarlu, V.; Karmakar, D.
    In the present study, the combination of vertical porous barrier along with the porous block is proposed for wave energy damping. Three types of vertical barriers such as (a) fully extended barrier (b) bottom-standing barrier and (c) surface piercing barrier away from the porous structure are analysed for wave trapping. The finite spacing in between vertical barrier and the porous structure is proposed for better wave trapping. The continuity of velocity and pressure at the interfaces of vertical barrier and porous structure are considered and the eigenfunction expansion method is adopted to determine the wave transformation characteristics due to the presence of submerged vertical barrier and porous block. The resistance and reactance offered by the porous structure are taken into account using the complex dispersion relation proposed by Sollitt and Cross (1972). The effect of structural porosity, width of the structure and angle of incidence on wave transformation due to the vertical barrier away from the porous structure are examined in detail. The results are compared and validated with the available literature for specific configurations as in Sollitt and Cross (1972) and Mallayachari and Sundar (1994). The study suggests that the increase in the structural porosity enhances the wave energy damping and global minima is achieved in the wave reflection coefficient due to the formation of standing waves by the breakwater system. The proposed structure can be adopted in leeward, port and harbour regions to achieve the tranquillity condition. © Springer Nature Singapore Pte Ltd. 2020.
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    A Review on the Properties of Steel-Concrete Interface and Characterization Methods
    (Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2021) Sumukh, E.P.; Goudar, S.K.; Das, B.B.
    The Steel-Concrete interface (SCI) is usually regarded as the weakest region, which influences both mechanical properties and durability of reinforced concrete structures. Several researchers have well explored and defined the importance of SCI on the service life of the reinforced concrete structures as it directly affects the durability. The primary objective of this paper is to report and compare a variety of published findings and microstructural analysis on the SCI in one place which appears in reinforced concrete. The information available on the occurrence, formation, properties, various characterizing and analysing techniques of SCI are reviewed for a better understanding of microstructural properties of SCI on the hardened and durability properties of reinforced concrete. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. Significant factors like quantification of porosity, porous zone thickness and actions that affect the properties of SCI like wall effect, bleeding, settlement and segregation of fresh concrete which were favourable to both initiation and propagation of corrosion are described in this paper. The influence of w/c ratio, hydration age, steel orientation and mineral admixtures on the distribution profiles of hydration products and Engineering properties of SCI is also discussed. © 2021, Springer Nature Singapore Pte Ltd.
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    Anti-corrosion treatment for bearing steel
    (American Institute of Physics Inc., 2021) Chawla, S.; Larsson, S.; Huang, H.; Hegde, S.
    The rolling bearing is one of the key components for the functioning of sophisticated machinery in the demanding industrial world today. For efficient and smooth operation, bearings need to sustain wear, fatigue, high loads, and sometimes, heat and harsh environments. Preceding failure analysis of the current work concluded that the recurring failure of the bearings under consideration is predominantly caused by the excessive wearing of the bearing track, and false brinelling due to harsh corrosive environment. This work, as a remedial measure, aims at enhancing the bearing life by suitably applying nitrocarburizing, a thermochemical heat treatment, to bearing parts. By heat treatment, nitrogen and carbon are diffused in hardened bearing races and rolling elements at a relatively lower temperature of 560-580 °C followed by controlled oxidation. Structural transformation during the process formed a compound layer at the sub-surface consisting of s-Fe2-3(N, C) and y'-Fe4(N, C) phases and a thin continuous layer of Fe3O4 on the compound layer as confirmed by X-Ray diffraction and microstructural analysis. Microhardness profile confirmed progressively declining hardness from the surface towards the core. Salt spray tests performed on the nitrocarburized parts indicated excellent corrosion-resistance properties. © 2021 Author(s).
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    NUMERICAL INVESTIGATION ON THE EFFECTS OF INHOMOGENEOUS GAS DIFFUSION LAYER AND IMPACT OF INTERFACIAL CONTACT RESISTANCE ON PERFORMANCE OF POLYMER ELECTROLYTE FUEL CELLS
    (International Association for Hydrogen Energy, IAHE, 2022) Shinde, U.; Padavu, P.; Koorata, P.K.
    A three-dimensional single-channel is modeled numerically to simulate homogeneous and inhomogeneous gas diffusion layer (GDL). The effect of interfacial contact resistance (ICR) between flow field ribs and GDL is also studied. The present study involves GDL being considered as a single component (homogeneous) in one case while in another case, GDL being considered with varying porosities to depict the inhomogeneity. The inhomogeneity in GDL is assumed to occur due to localized deformation induced due to non-uniform contact pressure. The study reveals increased availability of reactants at higher current loads in the case where ICR is assumed negligible. This study explains how the presence and absence of ICR impact reaction concentrations, water concentration, current density and polarization curve of polymer electrolyte fuel cells. It is observed in polarization curve that the presence of ICR has effect both in ohmic and mass transport region. This work involves considering 4 cases viz: homogeneous GDL, inhomogeneous GDL, homogeneous GDL with ICR and inhomogeneous GDL with ICR. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
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    Impact of Phase Change Materials on the Durability Properties of Cementitious Composites—A Review
    (Springer Science and Business Media Deutschland GmbH, 2023) Vismaya, K.; Snehal, K.; Das, B.B.
    Phase change materials (PCMs) are the novel thermal storage materials which have an ability to engross and dispel heat during the process of phase transition from solid to liquid and vice versa. Utilization of PCMs in cementitious composites has gained a lot of attention from the research fraternity to minimize the energy loadings used for space conditioning and heating in building. Impact of PCM’s presence in cementitious composites on the durability parameters is the need for its better usage. This paper gives the state of review on the influence of inclusion of phase change materials in the cementitious system on its various durability aspects. Durability properties such as porosity, water absorption, shrinkage, chloride ingression, and chemical attacks are compiled in this article. It is stated that the integration of PCM in cement composites enhances the porosity of cementitious system. Major hindrance described by the researchers is the interruption of hydration activity of cementitious system by the addition of PCM. Literature also signified that the micro/nano encapsulates PCMs and the use of highly reactive Pozzolans such as silica fume or nano-silica in conjunction with PCMs has the ability to lock up the limitations of PCMs. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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