Faculty Publications
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Item Development and properties evaluation of Mg-6% Zn/Al multilayered composites processed by accumulative roll bonding(Cambridge University Press, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Accumulative roll bonding (ARB) process was used to develop Mg-6% Zn/Al and Mg-6% Zn/anodized-Al multilayered composites. Microstructural characterization was done using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattered diffraction, and transmission electron microscopy. An average grain size measured in the roll-bonded layers of Al, anodized Al, and Mg-2% Zn was found to be 1.8 ?m, 1.6 ?m, and 0.6 ?m, respectively. Phases Al17Mg12, AlMg4Zn11, and Al2O3 after 5-pass of ARB were confirmed by X-ray diffraction analysis. The Mg-6% Zn/Al and Mg-6% Zn/anodized Al composites exhibited tensile strengths ?252 MPa and ?256 MPa, respectively, after a 5-pass ARB process. Hardness of the individual layers of composite increased linearly with an increase in the number of ARB passes. Fractographs of the multilayered composite illustrated the ductile failure in Al and anodized Al layers and transgranular brittle fracture in Mg-6% Zn layers. © Materials Research Society 2017.Item Effect of Secondary Mg17Al12 Phase on AZ80 Alloy processed by Equal Channel Angular Pressing (ECAP)(Springer Netherlands, 2018) Muralidhar, M.; Narendranath, S.AZ80 alloy was subjected through Equal Channel Angular Pressing (ECAP) to refine the grains at three different temperatures 548 K, 573 K, and 623 K up to 4 passes for route Bc, where the specimen is rotated 90? counter-clockwise direction for each pass. In the present work, experiments have been continued with route Bc and the average grain size was obtained of 7 ?m, 9.5 ?m and 11.2 ?m for the temperatures of 548 K, 573 K, and 623 K respectively after 4 ECAP passes. The average grain size of the procured AZ80 alloy was found to be 44.5 ?m. Mechanical properties of AZ80 alloy have been improved to the corresponding various processing temperatures. X-ray diffraction studies have been done on a fourth ECAP processed specimen and compared with a zero pass specimen to know the phase transformation at different processing temperatures. Fracture behavior of each of the three materials was studied and it revealed brittle fracture by increasing the number of ECAP passes. © 2015, Springer Science+Business Media Dordrecht.Item Internal damage growth in quasi-brittle fibre-reinforced cementitious materials under cyclic compressive loading(Structural Engineering Research Centre, 2023) Vidya Sagar, R.; Basu, D.J.; Suhas Reddy, K.V.; Prathap, Y.; Bhuvaneswari, G.; Sai Keerthi, P.This article reports a comparison between the internal damage growth in cementitious materials without fibres and with fibres subjected to elevated amplitude cyclic compressive loading. The damage progression was assessed using ultrasonic testing method and Acoustic Emission (AE) testing. The intricate fracture mechanism in the test specimens causes rise to a higher harmonic generation, which was used as an indicator to the internal damage. The decrement in wave peak amplitude with higher harmonic generation may be regarded as a ‘internal damge growth’ in the deformable solid. The complexity in the fracture mechanism in fibrous cementitious matrix influenced the heterogeneity of the specimen, which is reflected by the steep decrement in the slope of the line plotted using normalized higher harmonic ratio and load. It was observed that the ‘magnitude of the total damage’ developed in plain concrete at the last loading phase was relatively lower than brass coated steel fibre reinforced concrete. This was supported by the damage parameter based on generated AE, where final failure of the specimens preceded an AE avalanche. Therefore, the utilization of a combination of nondestructive testing techniques such as AE and nonlinear ultrasonic testing can offer a more comprehensive understanding of the progression of damage in quasi-brittle cementitious materials. © 2023, Structural Engineering Research Centre. All rights reserved.Item Failure of Soap Extruder Bolt Assembly(Springer, 2023) Kumar, J.K.R.; Mogra, N.; Padasale, B.; Dsilva, P.C.; Sondar, P.; Hegde, S.R.Present work investigates failure of EN8 steel bolt in a bolt–pin assembly that was used as a fastener in an industrial soap extruder. Unexpectedly, EN19 steel pin that is supposedly the sacrificial element in the assembly remained intact. The investigation follows standard failure-analysis procedure comprising, site-visit, visual inspection, metallography, mechanical-testing, design-analysis, numerical stress-analysis, and fractography. The design-analysis finds that the materials of construction were mistakenly swapped between the pin and the bolt that caused plastic-deformation, necking, and eventual failure of the bolt during operational peak-loading condition. The numerical stress analysis illustrates that the bolts failed at the thread-root region that acted as the stress-raiser. Additionally, the investigation finds that poor-quality machining left-behind jagged thread-root profile that increased the stress-concentration furthermore. The metallography and the fractography indicate that a transverse crack that was initiated at poorly machined thread-root led to the brittle fracture of the bolt. The investigation illustrates how human errors can cause recurring failure of critical components leading to production losses and makes suitable recommendations to prevent such failures in the future. © 2023, ASM International.Item Effect of Surface Modification on Erosion Behavior of Alumina-Samarium Strontium Aluminate Composite Thermal Barrier Coatings(Springer, 2025) James J, F.; Arya, S.B.; Yadav, S.; Paul, C.P.The mechanical and tribological characteristics of a thermal barrier coating are highly critical in gas turbine applications to resist high-temperature oxidation, corrosion, and solid particle erosion. In the present investigation, a composite coating with alumina and samarium strontium aluminate has been developed through a plasma spraying process. The as-coated composite top coat consisted of three phases ?-alumina, ?-alumina, and Sm2SrAl2O7. The as-coated surface is re-engineered with an Nd: YAG fiber laser to improve the mechanical and microstructural properties. The laser-treated samples showed a better erosion resistance than the as-coated samples. Despite the surface treatment, both the as-coated and the laser-treated samples showed a higher ‘average erosion value’ at an impact angle of 90° for the test temperatures of 200 and 800 °C. In addition, the as-coated and the laser-treated samples have a higher erosion rate at 800 than at 200 °C for the selected impact angles, with a mixed mode of material removal presenting both ductile and brittle failure mechanisms. © ASM International 2024.Item Studies on high-temperature erosion behaviour of HVOF sprayed NiCr based composite coatings(Elsevier B.V., 2025) Medabalimi, S.; Hebbale, A.M.; Gudala, S.; Ramesh, M.R.; Gujar, R.; Aravindan, N.; Petr?, J.Solid particle erosion at high temperature is a major problem in many industries and advanced protective coatings are needed to extend the service life of components subjected to harsh environment. The main objective of this study is to investigate the erosion behavior of HVOF sprayed (NiCr) + 5 % Si and (NiCr)+ 2% C based composite coatings at different impact angles and temperature, with specific emphasis on the effect of coating composition. The coatings exhibited excellent erosive wear resistance at elevated temperatures due to the formation of stable oxide layers (CrO, NiCr?O?, SiO?) and the incorporation of silicide phases (Ni?Si) to the NiCrSi coatings. However, NiCrC coatings containing hard carbide phases (such as NiC) showed higher erosion resistance at higher temperatures and normal impact angles (90°) because of their robust microstructure and thermal stability. The analysis of microhardness indicated that NiCrSi coatings provided higher hardness attributable to silicides and were therefore better suited to moderate erosive environments, whereas NiCrC coatings, with slightly lower hardness, exhibited excellent resilience under severe erosive environments. SEM, EDAX and XRD analyses showed that preferential erosion mechanisms were cutting and plowing at oblique angles (30°) and brittle fracture at normal angles (90°). Notably, at 800 °C, NiCrC coatings outperformed the NiCrSi coatings via consistently superior thermal and erosion resistance. These findings indicate that HVOF sprayed NiCrC coatings are suitable for high temperature erosion protection, and NiCrSi coatings are specifically developed for high erosive wear resistance at low impact angles. © 2025 The Author(s)Item Application of Taguchi's optimization techniques for enhancing the fracture characteristics and brittleness of self-compacting alkali-activated concrete(Elsevier B.V., 2025) Kuttagola, I.; Prashanth, M.H.Alkali-activated concrete has emerged as a promising material for energy-efficient construction, offering a technically viable and eco-efficient alternative that aligns with global sustainability goals. This study explores optimizing fracture properties in self-compacting alkali-activated concrete (SAAC) through controlled variations in maximum aggregate size (dmax) and fly ash. A systematic approach incorporating Taguchi's design of experiments (DOE) and ANOVA analysis was employed to identify optimal mix proportions that enhance fracture performance and ductility. The study employed the Weight-Compensated Work of Fracture Method (WWFM) based on curtailment of the tail of the P–? curve to determine the size-independent fracture energy (GF), enhancing the reliability of SAAC in structural applications. Additionally, the Two-Parameter Fracture Model (TPFM) evaluated the critical stress intensity factor (KsIc) and critical crack tip opening displacement (CTODc), while the MATLAB-based Box-Counting Dimension Method (BCDM) assessed the fractal dimension (D). The findings revealed a higher fracture performance with 0 % fly ash and 16 mm dmax (GF of 206.3 N/m and KsIc of 1.91 MPa?m), suitable for structural applications requiring maximum fracture energy and toughness. The study further tailored a higher ductility mix with 50 % fly ash and 16 mm dmax (CTODc of 0.032 mm and D of 1.144) offering a balanced solution for non-structural applications, providing sufficient strength with enhanced ductility. The closed-form predictive design (CPD) model enables the prediction of ft and KIc under a specified maximum fracture load, offering engineers a practical tool to optimize SAAC formulations by adjusting aggregate sizes and binder proportions for specific project needs. Regression models aligned strongly with experimental and existing literature results, affirming the reliability of predictive performance for future SAAC mix designs. © 2025 Elsevier Ltd