Browsing by Author "Deka, Surja"

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A comprehensive experimental and modeling study of the strain rate- and temperature-dependent deformation behavior of bio-degradable Mg-CeO2 nanocomposites
(ELSEVIER, 2024) Deka, Surja; Mozafari, Farzin; Mallick, Ashis; 0000-0001-8218-4410; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Mozafari, Farzin
A comprehensive study was undertaken on the temperature-dependent and strain rate-sensitive deformation behavior of near-dense low-volume fraction magnesium-cerium dioxide (Mg-CeO2 ) nanocomposites synthesized by powder metallurgy technique. The process involved ball milling of elemental powders → cold compaction → sintering in an inert atmosphere, and in-situ hot extrusion. The Mg-CeO2 nanocomposites displayed strain rate and temperature sensitivity, exhibiting higher yield strength, superior compressive characteristics, greater hardness, and improved ductility compared to pure Mg and most commercial Mg alloys. Furthermore, a thorough micro-structural investigation was conducted to characterize the distributions of ceria nanoparticles, grain refinement degree, ceria-magnesium interface, formation of deformation twins and interfacial bonding between the reinforcement and matrix. The present study has proposed two modeling approaches, the Johnson– Cook (J–C) constitutive model and a machine learning-assisted model, to predict the mechanical behavior of monolithic Mg and Mg-CeO2 nanocomposites. The models effectively explained the deformation behavior under various strain rates and temperatures.
Deformation behavior of nanostructured aluminum: Experiment and computational study
(Elsevier Ltd, 2023) Deka, Surja; Mozafari, Farzin; Mallick, Ashis; 0000-0001-8218-4410; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Mozafari, Farzin
Nanocrystalline metals have been processed from powder predecessors in recent times in significant ways, and nowadays, materials are starting to be manufactured which are not only strong but also ductile. Nanocrystalline aluminum (Average grain size 51 nm) was synthesized through high-energy ball milling at the room temperature of microcrystalline powder. The particle size and crystallite sizes were obtained by Williamson Hall and found to be in good correlation with transmission spectroscopy (TEM) data. There was a significant increase in the mechanical properties of nanostructured aluminum in comparison to coarse-grained aluminum. Moreover, a phenomenological model of large-deformation, isotropic, rate-dependent plasticity is developed, which takes into account pressure dependency, plastic dilatation, and non-normal flow. The model has been incorporated into a finite element program. Compression and tension experiments were performed on nanocrystalline aluminum, and the constitutive parameters within the model were estimated from these experiments. The present study shows that the constitutive model successfully simulates the mechanical response of nanocrystalline aluminum with reasonable accuracy using our numerical finite-element capability.
Development of high-performance nanostructured aluminum and its constitutive modeling
(Taylor and Francis Ltd., 2023) Deka, Surja; Mozafari, Farzin; Mallick, Ashis; Thamburaja, Prakash; Gupta, Manoj; 0000-0001-8218-4410; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Mozafari, Farzin
A new technique, an in-situ hot-extrusion-based synthesizing process, is proposed to develop high-performance nanocrystalline aluminum (nc-Al) with an optimally tuned strength-to-ductility ratio suitable for various technologically relevant applications. Comprehensive investigations are conducted by characterizing mechanical and microstructural properties to realize the influence of various synthesizing variables on the properties of the bulk nc-Al. Furthermore, a continuum-scale constitutive modeling approach is proposed based on dominant microstructural mechanisms of plastic deformation and implemented into a finite element solver using a user-defined material interface. It is shown that the proposed theory can provide a versatile platform to predict the nanocrystalline aluminum mechanical response quite well.
Microstructural, mechanical, tribological, and corrosion behavior of ultrafine bio-degradable Mg/CeO2 nanocomposites: Machine learning-based modeling and experiment
(ELSEVIER SCI LTD, 2023) Deka, Surja; Mozafari, Farzin; Mallick, Ashis; 0000-0001-8218-4410; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Mozafari, Farzin
The present study investigated the microstructural, mechanical, tribological, and corrosion behavior of near-dense and low-volume fraction magnesium-cerium dioxide (Mg/CeO2 ) (x = 0.5, 1, and 1.5 vol.%) nanocomposites synthesized by in-situ hot extrusion assisted powder metallurgy (PM) process. Results showed a significant improvement in wear resistance for Mg/CeO2 nanocomposite compared to monolithic Mg at varied applied loads. Microindentation tests were performed to access the Vickers microhardness homogeneity along the extrusion direction. The corrosion analysis revealed that introducing ceria nanoparticles enhanced Mg’s corrosion resistance and expedited the development of an apatite layer on the surface, providing enhanced protection. A feedforward neural network and Long Short-Term Memory (LSTM) network were also developed to characterize nanocomposites’ wear and corrosion behavior.