Faculty Publications
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Item Investigation of fracture toughness analysis of polymer composites using finite element analysis(Elsevier, 2024) Doddamani, S.; Begum, Y.; Bharath, K.N.; Rajesh, A.M.; Mohamed, K.K.This chapter includes a study on using finite element analysis (FEA) to investigate the fracture toughness of polymer composites. This study’s objective is to assess polymer composites' fracture toughness. By considering the material properties and stress distributions, multiscale modeling approaches in FEA enable a thorough assessment of the material behavior under various loading circumstances. The analysis’s findings shed important light on the polymer composites' fracture toughness. The chapter ends with recommendations for further research and a review of the benefits and drawbacks of employing multiscale modeling and FEA techniques to analyze fracture toughness in polymer composites. The results of this work have significant ramifications for polymer composite structure design and optimization, particularly in applications requiring high fracture toughness. © 2024 Elsevier Ltd. All rights are reserved including those for text and data mining AI training and similar technologies.Item Development of austempered ductile iron for high tensile and fracture toughness by two step austempering process(2008) Ravishankar, K.S.; Udupa, K.R.; Prasad Rao, P.P.During conventional austempering austempered ductile iron showed a decrease in fracture toughness with increasing austempering temperature, while the tensile toughness increased. Thus high fracture toughness was associated with low tensile toughness. A two step austempering treatment was then adopted where the samples were first au stem p ered at 3000e for sh ort peri 0 ds varyi ng from 10m in utes to 60 minutes, and then subsequently transferred to a second furnace at 4000e for further austempering for 2 hours. It was found that this resulted in fine ferrite grain size, high carbon content of the retained austenite together with increased stability of the austenite. Under such conditions it was possible to achieve an excellent combination of high fracture toughness and high tensile toughness.Item Plasma-sprayed graphene oxide reinforced alumina composite coatings on low carbon steel with improved fracture toughness, brittleness index, and microhardness(Elsevier Ltd, 2020) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.In this work, the mechanical properties of atmospheric plasma-sprayed Al2O3and Al2O3-xGO (x = 0.5, 1.0, 1.5, and 2.0 wt%) coatings on low carbon steel was evaluated using the Vickers indentation technique, and the effects of GO addition in microhardness brittleness index and fracture toughness were investigated. The Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) techniques were employed to analyze the microstructural characterization of the plasma-sprayed coatings and to confirm the retention of GO in the Al2O3-xGO composite after the plasma spray. It was found that the Vicker's microhardness of as-sprayed Al2O3is 4.148 GPa and it decreased with the increase in the addition of GO and for Al2O3-2.0GO, it is 3.305 GPa. The fracture toughness of Al2O3is 4.86 (MPa m1/2) whereas for Al2O3-2.0GO is 16.85 (MPa m1/2). The fracture toughness has increased whereas the brittleness index has decreased as the weight percentage of GO addition is increased in the Al2O3-GO composite. Thus, the plasma-sprayed Al2O3and Al2O3-xGO coatings suggest that 2 wt% GO addition helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier Ltd. All rights reserved.Item Experimental investigation on Mode-I fracture toughness of Carbon-Carbon composites fabricated by preformed yarn method(Elsevier Ltd, 2021) Sunil Kumar, B.V.S.; Neelakantha Londe, V.; Lokesha, M.; Anilas, M.; Surendranathan, A.O.Carbon-Carbon composites are one such material that gives designers significant importance for advanced applications over conventional materials. They are applied in applications at very high temperatures (up to 3000°C), and under extreme conditions. They have a density which is much less than metals and ceramics and thus, make low part weight a significant factor for aerospace applications. Fracturing toughness is a measurable way to express a substance's resistance to fracture in the case of a break. This paper describes the experimental studies done to investigate the Mode-1 fracture toughness of carbon-carbon composites which was fabricated via the preformed yarn method. Fracture toughness was determined for four different (a/w) ratios i.e. 0.45, 0.47, 0.50 and 0.52 respectively. The results showed that with only two cycles of pitch impregnation, HIP and graphitizing, carbon-carbon composites were successfully produced. The specimen having an (a/w) ratio of 0.45 had a higher fracture toughness value in comparison with all values. As the (a/w) ratio was increasing, the fracture toughness value decreased and the fractured surface clearly shows a brittle fracture behavior. © 2021 Elsevier Ltd. All rights reserved.Item Study on fracture toughness of carbon-carbon composites at low temperatures(Elsevier Ltd, 2022) Sunil Kumar, B.V.S.; Neelakantha, N.V.; Kumar, M.; Lokesha, M.; Vasantha Kumar, S.N.; Surendranathan, A.O.Carbon-carbon composites (C-CC), employed as composites in space and other industries for their outstanding properties. In extreme temperatures, the C-CC has proved to be the most efficient material. C-CC is one of the top thermal quality high-temperature materials such as high-temperature stability, excellent thermal conductivity, and low-temperature expansion coefficients. C-CC brake disks are highly demanded in aviation, trains, trucks, even race vehicles. Although C-CC is normally utilized at very high service temperatures, recently it has been necessary to explore these in low-temperature circumstances as components must also pass through low-temperature conditions in modern applications. In developing engineering structures, materials and systems for their technical safety, durability, and reliability, fractures and damage prevention and evaluation have an important role to play. Fracture toughness means quantifying the resistance of the fracture when a crack occurs. The present experimental study explores the influence of low temperature on the fracture toughness of C-CC. The low temperatures test of the samples has been done at a temperature between -10 °C and -40 °C. The results demonstrate that the fracture toughness value consistently raised as the temperature dropped. The Fluctuation began at a -10 °C from 2 % with a forecast of -40 °C to 32 %. © 2022 Elsevier Ltd. All rights reserved.Item Investigation of fracture toughness in mixed mode for hybrid laminated polymer composites using an A4PB type specimen(Elsevier Ltd, 2022) Vijay Kumar, T.N.; Sharanaprabhu, C.M.; Kudari, S.K.In this paper, the fracture toughness of hybrid composites for with and without fly ash composites is evaluated for asymmetric four-point bend test specimens. The preparations of specimens are by simple hand layup technique. Specimens are tested under a universal testing machine for peak load. And concluded that the specimens with fly ash composition yield better fracture toughness compared to without flyash. The scanning electron microscope study shows that the crack starting and progression is mainly dependent on s/d ratios. © 2022Item Ductile cast iron samples were austenitized at 927 °C and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 °C, 288 °C, 316 °C, 343 °C, 371 °C, and 399 °C. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pet retained austenite containing more than 1.8 wt pet carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of KIC2 against ?? (X?C?)1/2 resulted in a straight line, as predicted by the model.(Minerals, Metals and Materials Society, Dependence of Fracture Toughness of Austempered Ductile Iron on Austempering Temperature) Prasad Rao, P.; Putatunda, S.K.1998Item An investigation was carried out to examine the influence of chromium content on the plane strain fracture toughness of austempered ductile iron (ADI). ADIs containing 0, 0.3 and 0.5 wt.% chromium were austempered over a range of temperatures to produce different microstructures. The microstructures were characterized by optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and correlated with microstructure and chromium content. The chromium content was found to influence the fracture toughness through its influence on the processing window. Since the chromium addition shifts the processing window to shorter durations, the higher chromium alloys at higher austempering temperatures tend to fall outside of the processing window, resulting in less than optimum microstructure and inferior fracture toughness. A small chromium addition of 0.3 wt.% was found to be beneficial for the fracture toughness of ADI. © 2002 Elsevier Science B.V. All rights reserved.(Elsevier BV, Investigations on the fracture toughness of austempered ductile iron alloyed with chromium) Prasad Rao, P.; Putatunda, S.K.2003Item Ductile cast iron was austenitized at four different temperatures and subsequently austempered at six different temperatures. Plane strain fracture toughness was evaluated under all the heat treatment conditions and correlated with the microstructural features such as the austenite content and the carbon content of the austenite. Fracture mechanism was studied by scanning electron microscopy. It was found that the optimum austempering temperature for maximum fracture toughness decreased with increasing austenitizing temperature. This could be interpreted in terms of the microstructural features. A study of the fracture mechanism revealed that good fracture toughness is unlikely to be obtained when austempering temperature is less than half of the austenitizing temperature on the absolute scale. © 2002 Elsevier Science B.V. All rights reserved.(Elsevier BV, Investigations on the fracture toughness of austempered ductile irons austenitized at different temperatures) Prasad Rao, R.; Putatunda, S.K.2003Item Simulated weldments of AISI grade 304 stainless steel having a ferrite content of 4-6% with three levels of nitrogen (0.03, 0.08, and 0.11 wt-%) were prepared using a modified elemental implant technique. From these weldments, subsize Charpy impact specimens were prepared and subjected to aging treatment at different temperatures, 623-748 K, and for different times, 1000-5000 h. Impact toughness curves for these aged samples were generated by testing at various temperatures from 77 K to 300 K. From the impact curves the upper shelf energy (USE) and lower shelf energy (LSE) were determined. It was observed that both USE and LSE decreased with aging time at all temperatures. Nitrogen seems to offer a beneficial effect as far as impact toughness is concerned, as both USE and LSE values increased with increasing nitrogen content. The worst aging conditions were identified as 748 K, 2000 h at the lowest nitrogen level of 0.03 wt-%. An empirical relation connecting the aging temperature, aging time, and nitrogen content to the LSE was developed, which can be used to predict the time for embrittlement at a given nitrogen level and aging temperature. © 2005 Institute of Materials, Minerals and Mining.(Prediction of embrittlement during aging of nuclear grade AISI 304 stainless steel TIG welds) Nayak, J.; Udupa, K.R.; Hebbar, K.R.; Nayak, H.V.S.2005