https://dspace.iiti.ac.in:8080/jspui/handle/123456789/3646 2026-05-15T09:14:36Z 2026-05-15T09:14:36Z Kundalwal, Shailesh https://dspace.iiti.ac.in:8080/jspui/handle/123456789/18372 2026-05-14T12:28:28Z 2026-01-01T00:00:00Z

Title: Energy-efficient machining using untextured and laser textured cutting inserts: Experimental investigation and pareto-based optimisation Authors: Kundalwal, Shailesh Abstract: Laser surface texturing has emerged as an effective approach to enhance tool–workpiece interactions and improve machining performance. In the present work, a combined experimental and optimisation framework is aimed at assessing the energy-efficient machining of AISI H13 steel using Nd: YAG laser surface-textured cemented carbide tools under various conditions. Turning experiments were conducted on a semi-automatic lathe, and the machining responses were recorded using a dynamometer setup. The regression models were formulated from the conducted experiments and used as surrogate objective functions for optimisation. The Archimedes Optimisation Algorithm (AOA) was considered for single-objective optimisation to find optimal machining conditions for minimum cutting force, minimum coefficient of friction, and maximum material removal rate. To explore the trade-offs associated with conflicting objectives, Pareto optimisation was employed using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), yielding a Pareto front and a balanced (knee-point) solution. The AOA-based balanced solution was obtained at cutting speed (CS) = 75 m/min, feed rate (FR) = 0.20 mm/rev, and depth of cut (DC) = 0.42 mm, yielding cutting force (Fz) = 149.9 N, coefficient of friction (CoF) = 0.320, and material removal rate (MRR) = 0.404 kg/s. In comparison, the NSGA-II knee-point solution at CS = 72 m/min, FR = 0.15 mm/rev, and DC = 0.41 mm resulted in Fz = 123.66 N, CoF = 0.3515, and MRR = 0.3149 kg/s, providing more balanced and stable machining conditions. The quantitative comparison revealed that the NSGA-II provided better optimal solutions, resulting in a 17.5% reduction in cutting force, 2.5% reduction in Specific Consumption Energy (SCE) compared to the AOA-balanced solution, with a balanced increase in friction and a meticulous reduction in material removal rate, thereby representing improved process stability and energy efficiency. The findings are directly related to industrial machining of AISI H13 steel used in die and mould manufacturing, where improved energy efficiency and process stability are critical. © 2026 The Authors.

2026-01-01T00:00:00Z Jagdish, Sarang https://dspace.iiti.ac.in:8080/jspui/handle/123456789/18360 2026-05-14T12:28:27Z 2026-01-01T00:00:00Z

Title: Elasto-viscous regime in coalescence of viscoelastic droplets Authors: Jagdish, Sarang Abstract: The merging of two droplets represents an energy-minimizing process whereby they combine to produce a thermodynamically stable droplet. Coalescence of Newtonian droplets is characterized by distinct viscous and inertial regimes. In contrast, viscoelastic fluids containing polymers display additional regimes when elastic and viscous stresses are comparable. We reveal a transition from an elasticity-dominated regime to an elasto-viscous regime in the coalescence of concentrated polymer droplets. Experimental measurements of interface curvature reveal that common assumptions used to estimate axial curvature are not universal. Using numerical simulations based on a volume-of-fluid framework with the exponential Phan–Thien–Tanner model, we reproduce the viscoelastic neck growth in good agreement with experiments. These results advance the understanding of droplet coalescence and highlight the role of viscoelastic effects in complex fluids. Copyright © 2026 the Author(s).

2026-01-01T00:00:00Z Bheda, Nikunjbhai J. Joshi, Suhas S. Palani, Anand Iyamperumal https://dspace.iiti.ac.in:8080/jspui/handle/123456789/18354 2026-05-14T12:28:26Z 2026-01-01T00:00:00Z

Title: Investigation of the influence of high reflective coatings on NiTi SMA-bimorph for realization of deformable mirror Authors: Bheda, Nikunjbhai J.; Joshi, Suhas S.; Palani, Anand Iyamperumal Abstract: In adaptive optics wavefront correction, the surface of the deformable mirror experiences tiny deformations to generate specific Zernike mode shapes. These mode shapes are used to compensate for distortions in the incoming wavefront caused by atmospheric turbulence or optical system imperfections. In this regard, there is a need to develop a highly reflective, deformable mirror structure capable of controlled micro-actuation for adaptive optics applications. Such mirrors can adjust the aberration caused by atmospheric turbulence, thereby improving the quality of the optical signal. In this work, the highly reflective deformable mirrors were fabricated by integrating NiTi shape memory alloy bimorph with reflective coatings. NiTi shape memory alloy (SMA) thin film was deposited onto a 200 µm Kapton substrate using electron beam evaporation, forming a flexible bimorph structure. This structure was deposited with aluminum (Al), silver (Ag), and copper (Cu) coatings individually via thermal evaporation to achieve Al-NiTi, Ag-NiTi, and Cu-NiTi-based deformable mirrors. Electro-thermomechanical simulations incorporating Joule heating were performed to predict actuation behavior, which was experimentally validated using a laser displacement sensor. The simulation results demonstrate an enhancement in the shape recovery ratio of the NiTi bimorph actuator from 77.7% to 93.7% with an increment in the convection coefficient from 100 to 200 W/m2*K for the same cycle time. Similarly, reducing the bimorph width from 20 mm to 10 mm improves recovery from 76.9% to 88.9% due to faster thermal reaction and lower structural inertia. Wettability results show a maximum improvement of 5.8% for the Al-NiTi mirror compared to the NiTi bimorph mirror in the martensite phase. The reflectivity of the NIR wavelengths was observed as 95 ± 1% for Al-NiTi, 96 ± 1% for Ag-NiTi and 98 ± 1% for Cu-NiTi-based deformable mirrors. These findings demonstrate the potential of NiTi-based deformable bimorphs with metallic coatings as reflective surfaces for wavefront correction in adaptive optics. © 2026

2026-01-01T00:00:00Z Singhal, Mohit Gaur, Aditya Gaur, Akshay Singh, Dhiraj Kumar Patel, Satyanarayan https://dspace.iiti.ac.in:8080/jspui/handle/123456789/18339 2026-05-14T12:28:25Z 2026-01-01T00:00:00Z

Title: Piezocatalytic enhancement in La-doped Na0.5Bi0.5TiO3 ceramics for water treatment Authors: Singhal, Mohit; Gaur, Aditya; Gaur, Akshay; Singh, Dhiraj Kumar; Patel, Satyanarayan Abstract: In the present work, La-doping (1, 1.5, and 2 mol%) is used in Na0.5Bi0.5TiO3 (NBT) ceramics to enhance piezocatalytic performance. La-doping increased the density of the sintered pellets (from 91% to 98.5%) and significantly enhanced their poling response. The piezoelectric coefficient of NBT-xLa increased from 58 pC/N (x = 0) to 101 pC/N (x = 1.5%). Additionally, the piezoelectric coefficient to relative permittivity ratio increases with La concentration, indicating enhanced piezoelectric potential. The optimized NBT-0.015La composition achieved 92% RhB degradation within 120 min under ultrasonication with a catalyst dosage of 1 g/L. When applied as a piezocatalyst in a ball-milling system, the same composition achieved ∼61% degradation at a dosage of 2 g/L. Poled NBT-0.015La pellet as catalysts further demonstrated ∼61–67% degradation over five reuse cycles with negligible performance loss. Overall, NBT-0.015La shows strong piezoelectric efficiency, stability, and reusability, establishing ultrasonication-driven piezocatalysis as a promising lead-free route for sustainable wastewater treatment. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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