http://dspace.dtu.ac.in:8080/jspui/handle/123456789/108 2026-04-28T06:25:02Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22684 Title: OPTIMIZATION OF PROCESS VARIABLE FOR ADDITIVE MANUFACTURED PLA BASED TENSILE SPECIMEN USING TAGUCHI DESIGN OF EXPERIMENT AND ARTIFICIAL NEURAL NETWORK (ANN) TECHNIQUE Authors: TEHARIA, RISHABH; SINGARI, RANGANATH.M (SUPERVISOR) Abstract: Additive Manufacturing or 3-D printing is a fabrication process by which a 3-dimensional solid iobject iis imanufactured iby idepositing ilayers iby ilayers ion ithe iobject. iIt iis iemerging ias ione iof ithe iinnovative itechnologies iand ihighly iaffect ithe imanufacturing isystem. iToday, iadditive imanufacturing i(AM) ireveals ichanges iin icomplete ivalue icreation, istrategic isystem, iand iprocesses. iMass icustomization iwith iminimization iof iwaste iand iability ito imanufacture icomplex istructure imake ithis iprocess isuperior iover iother. iFreedoms iof idesign, irapid iprototyping iare isome iother ibenefits. i The iaim iof ithis istudy iis ito ioptimize ithe iprocess iparameters iof ifused ideposition imodeling i(FDM) iby iexploring ithe itensile itesting iof iPolylactic iacid i(PLA). iIn ithis iwork, iwe ivaried iprocess iparameters ilike ilayer ithickness, iraster iorientation, istructure, ispeed, iand inozzle itemperature iare iinvestigated. iBased ion ithese iparameters iTensile ispecimen iare iprinted iby iusing iFusebot i250+ iFDM. iThe iTensile ibehavior iwas iinvestigated iunder idifferent icondition. iUsing iArtificial iNeural iNetwork, ithe iobtained iexperimental iresults iare ivalidated iand ichecked ifor ioptimum ivalue iof itensile istrength iunder idefined iconditions. 2021-06-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22543 Title: DESIGN OF HYBRID SETUP FOR DETERMINATION OF MECHANICAL PROPERTIES OF SERVICE EXPOSED MATERIALS USING SMALL PUNCH TEST AND FEM Authors: SHEKHAR, SHIVAM Abstract: The accurate determination of mechanical properties for materials exposed to harsh service conditions is critical for ensuring the safety, reliability, and extended operational life of components in industries such as nuclear power, aerospace, and oil and gas. Traditional mechanical testing methods often demand large material volumes, which is impractical for in-service components or hazardous materials like irradiated specimens. The Small Punch Test (SPT) offers a miniaturised, semi-nondestructive alternative, yet its standalone application is limited by reliance on empirical correlations and the complex biaxial stress state, hindering direct property extraction. This research addresses these limitations by proposing a novel hybrid experimental-numerical setup that integrates SPT with the Finite Element Method (FEM). Our methodology involves a meticulously designed hybrid setup that combines a miniaturised SPT fixture with high-precision extensometers for accurate punch displacement measurement. The iterative optimisation process, managed through ABAQUS routines, enables the extraction of fundamental material properties. Through rigorous validation and case studies, the hybrid SPT-FEM approach demonstrated significant improvements in material property characterisation. Finite Element Analysis (FEA) results, including load-displacement curves and deformed specimen shapes, showed strong agreement with experimental data. Notably, FEM analysis helped refine empirical correlations, leading to improved estimations for ultimate tensile strength. The setup's efficacy was validated across diverse service-exposed materials, including AL6082 alloy & Cr-Mo Steel. This research transforms the Small Punch Test from a qualitative screening tool into a robust, quantitative method for material characterisation, particularly for scenarios with limited or hazardous sample availability. The hybrid SPT-FEM setup provides critical insights into material degradation, enabling more accurate fitness-for-service assessments and reliable life extension predictions for ageing industrial infrastructure. 2025-05-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22542 Title: EXPERIMENTAL STUDY OF TRIBOLOGICAL PERFORMANCE OF LASER TREATED STEEL SURFACE WITH SMART COATING UNDER THE VIBRATIONAL LOADING Authors: JHA, SHUBHAM KUMAR Abstract: High-performance materials such as stainless steels and nickel based super alloys are widely used in demanding applications where high mechanical and thermal properties are required. The applications of super alloys are mainly found in jet engines, power plants and gas turbines demanding high fatigue strength, corrosion and oxidation resistance as well as wear resistant properties. In order to use them, they go through various machining processes such as milling, turning, cutting, polishing etc. until the final product is achieved. Modern manufacturing industries employs various machining tools and technologies to improve the machining process of heat resistant super alloys. However, there are still challenges which needs to be addressed. Among them, adhesive wear of the machining tools is one of the main wear mechanism during the tribological interaction of tool and workpiece, preventing them to achieve the desired quality and surface finish of the end product. Moreover, it damages the tool reducing its lifecycle and in return, increasing the production cost. Among the cutting tools tungsten carbide (WC/Co) tools coated with TiAlN coating due to their good high temperature performance are extensively used. Nonetheless, these coatings still face issue like adhesive wear, abrasion, oxidation at higher temperature damaging the tools and subsequent machining. Therefore, it is imperative to understand the initiation mechanism of adhesive wear during the tribological interaction of super alloys and coated cutting tool material. In this research work, the tribological response of two coatings deposited by physical vapour deposition (PVD), having the composition Ti60Al40N and Ti40Al60N have been studied against two super alloys material, i.e. Inconel 718 and stainless steel 316L. A high temperature SRV (Schwingung (Oscillating), Reibung (Friction), Verschleiß (Wear)) reciprocation friction and wear test set up was employed to investigate the friction behaviour, wear rate and dominant wear mechanisms. For Ti60Al40N coating, the experimental results revealed that generally, friction increases in case of sliding against Inconel 718 up to 400 °C and drops at 760 °C. A high wear volume at room temperature and a decrease to a minimum at 760 °C has been observed for Inconel 718. On the other side, Stainless steel 316L (SS 316L) faces a continuous rise in friction coefficient with highest value at 760 °C during sliding against Ti60Al40N coating. Wear is highest at 400 °C for SS 316L pin. The worn surfaces shows that both workpiece materials experience increase in material transfer due to adhesive wear with rise in temperature. At 400 °C, adhesion is the primary wear mechanism for both workpiece materials. A further rise in temperature to 760 °C promotes the adhesive wear through oxides formation on both material surfaces. Similarly, Ti40Al60N coating shows the same friction behaviour with change in average steady state friction values for both material of Inconel 718 and SS 316L. Both workpiece materials responds in a similar way to wear volume loss, i.e. lowest at room temperature and highest at 760 °C. For Inconel 718, transfer of coating constituents on to the Inconel 718 pin surface was detected and associated with coating rupture and peeling, exacerbating with rise in temperature. Adhesion, abrasion, and oxidation are primary wear mechanisms at 400 °C and 760 °C. For SS 316L, coating vi transfer only happen at 400 °C. No damage of coating at 40 °C, a complete damage at 400 °C, and formation of dense porous oxides layers at 760 °C have been noticed. At 400 °C, adhesion, abrasion, and chipping while at 760 °C, adhesion, three body abrasion, ploughing and oxidation are the main wear mechanisms. Additive manufacturing has revolutionized component fabrication by enabling the production of complex geometries and tailored surface textures unachievable by traditional methods. However, AM surfaces often exhibit intrinsic roughness, porosity, and microstructural heterogeneity, which can detrimentally affect frictional characteristics and accelerate wear under operational stresses. To mitigate these drawbacks, laser surface treatment is employed as an effective post-processing technique to modify surface hardness, induce compressive residual stresses, and homogenize surface microstructure, thereby improving wear resistance and mechanical integrity. The incorporation of advanced smart coatings—such as magnetorheological fluids and shape- memory polymers—further enhances the tribological system by providing adaptive vibration damping and frictional modulation capabilities, which are particularly advantageous in high- frequency vibrational environments. The research methodology involves detailed finite element analysis (FEA) using ANSYS Workbench, simulating a representative pin-on-disk tribological configuration under dry sliding conditions coupled with various vibrational load profiles. Comparative simulations across three primary surface conditions—untreated AM, laser-treated, and smart-coated laser-treated surfaces—are conducted to quantify and analyze key tribological metrics including coefficientof friction, wear depth, contact pressure distribution, and vibrational response characteristics. The simulation results reveal a marked improvement in tribological performance for laser-treated and smart-coated surfaces, exhibiting reduced frictional forces, diminished wear rates, and superior vibration attenuation compared to conventional AM surfaces. These findings elucidate the synergistic effects of combining advanced manufacturing, surface engineering, and smart material technologies to realize robust, adaptive, and long-lasting tribological systems. 2025-06-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22493 Title: NUMERICAL INVESTIGATION OF FRACTAL-SHAPED MICROCHANNEL HEAT SINK (MCHS) Authors: SADIQUE, HUSSAM Abstract: The problem of effective temperature management has emerged as a significant obstacle to future developments in microelectromechanical systems (MEMS) and high-performance computing devices due to the growing integration and miniaturisation of electronic systems. Because of its small size and high surface-area- to-volume ratio, microchannel heat sinks (MCHS) have become a state-of-the-art option for efficient heat dissipation in constrained locations. This thorough analysis compiles a large body of research on enhancing heat transfer in MCHS using sophisticated geometrical adjustments, nanofluids, and best optimisation strategies. With a focus on passive solutions like geometrical alterations, a first comprehensive analysis offers a thorough overview of state-of-the-art cooling strategies and divides MCHS enhancing techniques into active and passive categories. The study demonstrates how boundary layer development degrades thermal performance in straight channels and how fractal-shaped designs, which naturally produce chaotic advection and secondary flows, provide a ground-breaking method of improving convective heat transfer with negligible pressure drop penalties. Inspired by natural mass and energy transport phenomena, fractal MCHS (FMCHS) designs show exceptional ability to reduce temperature non-uniformity and thermal resistance. In the beginning of the study, simplified MCHS geometries were investigated by adding square ribs with double-filleted and rounded corners. To comprehend the function of local geometric smoothening in flow behaviour and thermal augmentation, three configurations, such as MC-SQ, MC-SQ-FR, and MC-SQ-DFR were examined. Through boundary layer re-development and improved mixing, the results showed that adding fillets to the rib corners significantly improved thermal performance. The MC-SQ-FR design increased Nusselt numbers by 15-22% while only increasing pressure drop by 2-10%. Building on this, a new FMCHS with cavities and ribs was suggested and subjected to ANSYS Fluent numerical analysis. Although there was a corresponding rise in pressure drop, the FMCHS with ribs (FMCHS-R) and diagonally positioned ribs (FMCHS-DR) layouts demonstrated the most notable heat transfer gains among the different configurations examined. An intelligent optimisation framework utilising Artificial Neural Networks (ANN) in conjunction with the Moth Flame Optimisation (MFO) algorithm was utilised to address the design trade-offs. This led vi to an ideal configuration where the best thermal-hydraulic performance was obtained with a rib radius of 26% along the FMCHS paths at a flow rate of 200 ml/min. RSM and HHO optimisation methods were also employed for the fractal microchannel heat sink (FMCHS) with ribs and cavities and show a thermal performance-thermal efficiency trade-off. RSM chose an FMCHS design with ribs (model value 1) and a moderate flow rate of 295 ml/min. The thermal resistance was 0.983, pumping work was 201.112 mW, high efficiency was 0.955, and Nusselt number (Nu) was 23.053. Conversely, HHO chose a rib-dominant hybrid design (model value 0.645) with a 400 ml/min flow rate. This design lowered thermal resistance to 0.7609 K-cm 2 /W, improving cooling performance, but it also increased pumping work (376 mW) and decreased efficiency (0.8835). Nusselt was 21.59, slightly lower. The effect of nanofluids, specifically water-based Al₂O₃ nanofluids, was examined in FMCHS under various Reynolds numbers (1000-3000) and a bottom heat flux of 50 W/cm² in order to further enhance the thermal performance. According to the findings, heat transport was significantly improved by nanofluids, quadrupling the Nusselt number at Re=3000. Increased viscosity and density resulted in a larger pressure drop, but the overall performance evaluation criterion (PEC) was greatly enhanced, demonstrating the thermophysical advantages of using nanoparticles. The idea that integrating bio-inspired geometries, nanofluid cooling, and AI-based optimisation provides a revolutionary route for the next generation of ultra-compact, high-efficiency thermal management systems is essentially supported by this collective body of research. 2025-07-01T00:00:00Z