PhD Theses (Mechanical Engineering)

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    Effective Utilization of Data for Enhancing the Performance of Manufacturing
    (2024) Chatterjee, Kaustabh
    The effective utilization of data is becoming increasingly important for enhancing the performance of manufacturing processes. In the era of Industry 4.0, advancements in technology have enabled the collection of vast amounts of data from various manufacturing processes, making it possible to analyze the data and derive insights that can help enhance the performance. One of the main advantages of using data-driven manufacturing is the ability to identify quality issues early in the production process. It reduces the likelihood of defective products, thereby enhancing customer satisfaction, reducing wastage and improving the profitability.
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    Experimental and Computational Studies on Exit-Hole-Free Friction Stir Spot Welding Processes
    (2024) Bhardwaj, Nitish
    This thesis contributes to understanding friction stir spot welding (FSSW) by investigating friction, heat generation and exit-hole elimination. Lubricants were applied during FSSW of aluminum alloy sheets resulting in a 44–55% reduction in torque and 12–24% reduction in plunge force requirements. More than 50% reduction in energy requirement while maintaining good joint strength is observed. This suggested the more important role of plastic deformation in heat generation as compared to friction. The study introduces an inverse approach to model friction during FSSW, utilizing finite element (FE) simulations in DEFORM 3D and validating with experiments. Further, this thesis investigates ways of producing exit-hole-free welds during FSSW. In one method the exit-hole is filled with waste aluminum chips and friction stir processing is performed over it. The process delivered 16% and 84% higher load-bearing capacities during T-peel tests compared to conventional FSSW with and without pin, respectively. A novel method of using consumable pin during FSSW is introduced to produce exit-hole-free joints. The feasibility and performance of FSSW using three consumable pin materials viz., AA6061-T6, mild steel and oil hardened non-shrinking die steel, are explored. Additionally, the research evaluates the impact of rotational speed and plunge rate on joint quality. It is found that the joint strength increases with increase in rotational speed up to 900 RPM and further increase in rotational speed decreases joint strength. A 1.7 times increase in joint strength at 900 RPM compared to 360 RPM is achieved. On the other hand, optimum plunge rate for highest joint strength is found to be 15 mm/min. A 4% increase in lap shear strength at 15 mm/min plunge rate compared to 6 mm/min, with an 8.5% decrease in energy requirements is obtained. A good match between experiments and FE simulations is obtained. Adhesive-bonded consumable pin along with application of lubrication is suggested for industrial application, which results in faster production speed and lower energy requirement while delivering good joint quality. This study provides a comprehensive understanding of FSSW, spanning friction, heat generation, exit-hole-free FSSW joints, parametric study and the integration of lubricants and adhesive-bonded consumable pins.
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    Application of Cold Metal Transfer Technology for Cladding of ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy
    (2024) Das, Bappa
    The Cold Metal Transfer (CMT) process is a specialized welding technique used for cladding and coating, which involves applying a layer of metal onto a base material. In fact, CMT cladding is an efficient additive manufacturing technology that finds application in the automotive, defence, and power plant sectors. As Additive Manufacturing evolves, new welding methods have emerged, including CMT, an advanced version of Metal Inert Gas (MIG) welding known for reduced spatter and low heat input. CMT-based cladding processes have gained attention for improved aesthetics and lower heat input. Utilizing a wire as feedstock and a robotic arm for deposition enables precise material placement in complex shapes, with heat input determined by process parameters like voltage, current, wire feed speed, and stand-off distance.
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    Performance Evaluation of Lubricated Polymer Gears
    (2023) Bharti, Sarita
    Injection molded polymer gears are being widely utilized as they offer several advantages, such as lightweight, good damping capacity, easy production, low manufacturing cost, and good mechanical properties for low and moderate-load applications. Many works have been earlier attempted to improve mechanical properties by incorporating fiber reinforcement. In this work, an attempt has been made to investigate the potential of using oil lubrication for performance improvement. In addition, the present study also aims to check the feasibility selective laser sintering (SLS) process and elastomeric material (thordon SXL) for gearing application. The sliding contact performance of these materials was also investigated using pin on disc configuration. The surface durability of the test gear was investigated using a house-developed gear rig at various loading conditions and a constant rotational speed under dry and lubricated conditions by observing the thermal response of gear teeth, lubricant temperature, periodically monitoring gear teeth surface, and failure morphology.
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    Development and Performance Investigation of a Biomass-fired grain dryer Coupled with Solar Air Heaters
    (2022) Kumar, Dhananjay
    In the present investigation, a cost-effective and efficient biomass-solar hybrid dryer has been developed for meeting the drying demand of agricultural products suitable for developing countries. The dryer mainly consists of a furnace, rectangular chamber, PCM tray, drying chamber, drying tray, solar air heaters, PVC pipe, sensible thermal storage (pebbles), and latent thermal storage (paraffin wax). In the present study, thermal analysis of the dryer is done for optimum removal of moisture. Energy and exergy analysis of the biomass-operated dryer, natural convection solar dryer, and forced convection solar dryer has been carried out. The drying characteristics of paddy have also been studied in the dryer. In the biomass-operated dryer, the effect of the sensible heat storage medium in the rectangular chamber was studied and found that the use of a sensible heat storage medium reduces the energy losses from the rectangular chamber (brick wall). It also reduces the exergy destruction in the rectangular chamber and retains a higher temperature for a longer period. Hence, it enhances the performance of the biomass-operated grain dryer. The effect of flue gas energy recovery has also been studied and found that the energy recovery technique reduces the wastage of energy in the flue gas. The use of a regulator valve in the exhaust pipe increases the temperature in the drying chamber
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    Numerical and Experimental Investigations for Electromagnetic Crimping and Welding of Multi-Material Tubular Components
    (2023) Kumar, Deepak
    Multi-material components have become necessities of the present time because of their ability to offer benefits of properties of multiple materials such as corrosion-resistant, lightweight, higher strength, and electrical conductivity in one single component. Joining multi-material combinations such as Cu-SS, Cu-Al, Al-Steel, and D9-SS 316LN by conventional fusion welding techniques is difficult due to the difference in their mechanical and physical properties, causing hot cracking; therefore, electromagnetic joining (EMJ), which is based on cold forming can be a viable alternative to conventional fusion welding processes. EMJ offers many advantages in the efficient manufacturing of multi-material components, yet it has not been widely adopted in industries. Therefore, this thesis aims to expand upon various forms of the EMJ process for tubular components to expedite its adaptation.
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    Stability and control of flow past elliptic cylinders
    (2022) Kumar, Deepak
    Linear stability analysis of steady two-dimensional flow past elliptic cylinders of different aspect ratio (Ar) is conducted. Computations are carried out for flow Reynolds number (Re) in the range 30-200. First, the main characteristics of the steady flow, like the bubble length, bubble width, separation Reynolds number, separation angle, drag coefficient, coefficients of the front and rear stagnation pressure, and the maximum vorticity on the cylinder surface have been obtained. The effect of blockage on the steady flow results has been studied by varying the location of the side boundaries. In certain cases, the flow properties are found to vary in a nonmonotonic fashion with change in the blockage. From the linear stability calculations, we find that there are three sets of complex eigenmodes (PWM, SWM and TWM) which become unstable with increase in Re. The critical Re for the onset of instability of these modes and the corresponding Strouhal number (St) have been computed. The effect of blockage on the linear stability results is also studied. Structural sensitivity analysis is conducted to find the region best suited for effecting control of the unstable modes. We carry out unsteady computations by selectively suppressing one or more linear modes to see the kind of flow which evolves and, as a result, make an attempt to understand the role of the unstable linear modes in the fully developed nonlinear flow.
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    Design and Development of Metal Hydride System for Thermal Energy Storage and Hydrogen Storage Applications
    (2022) Prasad, J Sunku
    The world is progressing toward renewable energy resources because of the increase in demand for energy, the price of fossil fuels and the global warming effect. A major shift from fossil fuels to renewable energy sources is needed to save the environment from global warming and climate change. Renewable energy sources are often limited for commercial use due to their intermittent nature, i.e., inconsistent energy supply and demand. This issue in concentrated solar thermal power (CSTP) technology can be addressed by integrating a thermal energy storage (TES) system. The excess thermal energy is stored in the TES system during sunshine hours. The stored energy is retrieved for producing electricity during the off-sun hours, making the CSTP plant operate continuously throughout the day and night. Thermal energy can be stored in three different ways: sensible heat storage (SHS), latent heat storage (LHS), and thermochemical energy storage (TCES). The TCES system offers high energy density, wide operating temperatures, and long-term storage among all TES systems. Another promising technology for storing excess renewable energy is in the form of hydrogen. Hydrogen as an energy carrier offers a large-scale, long-term, and seasonal storage of excess renewable energy. The excess electricity produced by renewables (primarily wind and solar PV) during low energy demand periods generates hydrogen using an electrolyzer. The stored hydrogen is utilized in stationary fuel cells for combined power and heat as per the demand.
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    Design Development and Control of a Compact Autonomous Underwater Vehicle
    (2022) Sahoo, Avilash
    Unmanned Underwater Vehicles (UUVs) are robotic devices used for various underwater applications. UUVs have gained popularity in scientific community because of their potential applications ranging from military and research establishments to marine industries. Most of these devices are expensive, bulky and developed for deep ocean applications. To extend the benefits of this technology to small-scale industries and general public, affordable compact AUVs are need of the hour. Here the design and development of an affordable compact underwater robot is presented. After identifying the design requirements, the robot model is designed using 3D modeling software ``SOLIDWORKS". Matlab optimization toolbox is used for the estimation of optimal position of internal components. Shape optimization with Ansys Fluent is carried out for drag coefficient minimization. The designed model has been analyzed using Finite Element Analysis to ensure its structural integrity in the underwater environment. Here stress analysis is used to show that the UUV with glass fiber composite body can withstand the underwater pressure at 100m depth with 1.8 factor of safety. Computational Fluid Dynamics (CFD) study is used to estimate the drag and lift coefficients, and the maximum velocity of the robot. The validated design is used to manufacture the UUV body using glass fiber composite. The developed robot is neutrally buoyant and has a three-part modular structure. This robot has 4 Degrees of Freedom (DOF) and uses three thrusters for propulsion. It has a closed-frame watertight enclosure, which houses different essential components such as battery, depth and temperature sensors, camera, Raspberry pi computer, Pixhawk controller and thrusters. During operation, the robot is connected to the computer on the ground using tethered connect for transmission of live underwater footage, sensor data, and control signal. Detailed cost analysis of the developed robot is also presented. The robot was successfully tested in a swimming pool, nearby river, and lakes, and the results are discussed.
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    Dynamic analyses of PZT based active nonlinear vibration absorbers
    (2022) Mohanty, Sibananda
    There are many physical systems such as engineering structures or machines which undergo severe vibration and need a reduction in vibration by using passive or active vibration absorbers. In the passive vibration absorber, structural modification is carried out by attaching an additional spring-mass-damper system to the vibrating main or primary system to reduce its vibration. Whereas in the active vibration absorber (AVA) various sensors and actuators are integrated with the passive vibration absorber to suppress the vibration of the primary system. The vibration absorbers are generally designed based on the assumption that the absorber structure possesses linear characteristics. However, an effective vibration absorber vibrates with a large amplitude leading to the dominance of structural nonlinearity. Thus, the linearity assumption regarding the elastic properties of the absorber substructure does not hold good in reality. Also, nonlinearity is inherently present in the main vibrating primary systems due to prolonged use, certain applications, or being subjected to various forms of external excitations. The available passive and active vibration absorbers also come up short to suppress the vibration in nonlinear primary systems under varied resonance conditions. Since the existence of nonlinearity in the primary systems and the absorber system are inevitable. It is observed from the literature that with the available passive or active vibration absorbers the vibration reduction of the primary system under varied resonance conditions is still high or limited to a very narrow range of operating frequencies. Also, complete vibration suppression of the nonlinear vibrating primary system is not achieved under various resonance conditions. The investigations of AVA with acceleration or combination feedbacks (displacement, velocity and acceleration) and its effectiveness in vibration suppression are also not explored. So, in the present thesis, a modified designed piezoelectric stack actuator based active nonlinear vibration absorber (ANVA) with various feedbacks and time delay is considered, where the frequency of the absorber can be actively changed to suppress the vibration of the primary system. In the modified designed ANVA the PZT (lead zirconium titanate) stack actuator is connected in series connection with a spring in the absorber configuration for a fail-safe design.
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    Numerical Investigation of the Unsteady Aerodynamics of ‘Passer Domesticus’ Inspired Biomimetic Wing
    (2022) Shaik, Masuruddin
    The flapping flight, which is governed by the unsteady aerodynamics, deals with inherent complexities especially at low Reynolds number (Re). Understanding the low physics behind these intricacies may lead to a great chance of enhancing the aerodynamic performance of Flapping Wing Micro Air Vehicles (FW-MAVs). Nature provides a variety of small flying birds and insects to achieve this goal via biomimicry. However, direct copying of concepts available in nature may not lead to feasible solutions. The balance between engineering implementation and exploitation of concepts from nature may lead to successful designs. The work presented in this dissertation attempts at bringing this vision a little closer to realization.
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    Film cooling analysis of injection configurations for afterburner aero-engine applications.
    (2023) Singh, Ashutosh Kumar
    There is a significant need for thrust augmentation in aircraft for several specific operations, such as combat or take-off from short runways. The additional thrust requirement is achieved by burning extra fuel in the afterburner, which further raises the temperature to 2200K. In order to increase thermal efficiency and power output, the turbine entry temperature of modern gas turbine engines has to be increased considerably. Furthermore, the exposed components in the pathway of the exhaust stream experience a very high temperature. Therefore, to maintain the permissible metal temperature for safe operation, the component under such high thermal loads requires a sophisticated cooling technique. “Film cooling” is one of the most adopted to protect the component which is subjected to hot flue gases.
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    Theoretical and Experimental Investigation of Axially Graded Smart Structures
    (2023) Kumar. Viwek
    The multi-segmented smart structures are a promising and versatile approach to designing complex systems that can be adapted to various applications. They offer greater flexibility, durability, and efficiency than monolithic structures and have the potential to transform the way of building structures. By breaking down a design into smaller segments, it is possible to make repairs or modifications to individual components without affecting the entire system. Additionally, segmented structures can be optimized for specific applications by adjusting the number, size, and shape of the segments. A variety of materials can be used to construct multi-segmented structures, including metals, composites, and polymers. This concept is extensively used in automobiles, aerospace, robotics, locomotives etc., to reduce the structure weight, material and cost. In this, the segments of different high-strength materials like steel are joined with lighter materials like composites. These segments may be joined along the longitudinal or transverse direction within the system. However, it causes the formation of interfaces at the segment joints and the generation of stress concentration due to sudden changes in the material. It may result in the failure of structures under different loading conditions. So, to tackle the issue of a sudden change in material properties, an idea was proposed to vary the material properties in a gradual manner along the span or thickness. Such advanced materials are known as functionally graded materials (FGMs). Hence, an appropriate method is required to investigate the behaviour of such structures, which can also serve as the benchmark for their optimal design and fabrication. Although numerical methods and commercial finite element packages are available for a variety of structural problems, there is always a need for analytical solutions. The analytical elasticity models can predict the behaviour of segmented structures more accurately as compared to the one or two-dimensional theories or numerical solutions. The extended Kantorovich method is undoubtedly one of the best techniques that offer an analytical solution for complicated problems.
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    Experimental Studies on Pore Scale Multiphase Flow in Homogeneous and Heterogeneous Micromodels Using Micro-PIV
    (2022) Haque, Md Najrul
    Micromodels are useful tool to study the fluid flow behavior in porous media at micron scale that is relevant to the many fields like petroleum recovery. During the last 30 years, micromodels have found to be the most precious tool, which allow the observation of fluid flow and transport at the micron scale in many processes related to chemical, biological, and physical fields of engineering. Micro-fluidic devices have been designed and used to investigate immiscible fluid-fluid displacement processes. Due to their optically transparent nature, such devices allow direct visualization of pore scale events using light microscopy. In this thesis, we focus on imaging multiphase flow phenomena at the pore scale within specifically designed micro-models using optical microscopy.
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    Mechanical, Microstructural, and Corrosion Characterizations of Similar & Dissimilar Induction Assisted Friction Stir Welding of Inconel 718 & Stainless Steel
    (2023) Raj, Sanjay
    Friction stir welding (FSW) of high-strength materials like Inconel 718 and steel is more challenging than welding softer materials for several reasons, including high tool degradation and the potential for defective joint formation. However, the demand for joining high-strength materials using the FSW technique is growing in industries such as nuclear plants, petrochemical, aerospace, submarine, and hydraulic power plant. This technique requires more development and improvement of the existing FSW techniques. Thus, the present study explored similar and dissimilar joining of Inconel 718 and stainless-steel materials under the conventional FSW and induction-assisted FSW process using tungsten carbide tool material. For the comparison of the conventional FSW process with external energy-assisted FSW, a setup for the induction-assisted FSW was developed, and experiments were carried out. It was found that tool life was significantly affected by the application of induction preheating. Various process parameters like weld traverse speed, tool rotational speed, plunge force, and preheating temperature affect the weld quality. From the experimental investigation of joining Inconel 718 by the FSW, it was found that an optimum traverse speed of 300 rpm and a low traverse speed of 90 mm/min resulted in refined grain microstructure, high microhardness, high strength and good corrosion resistance of the weld joint. The utilization of an induction preheating system in the FSW process resulted in improved weld quality at a high welding speed of 140 mm/min. The results also revealed that preheating affected the process temperature, lowering the axial force and frictional heat and improving the tool life
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    Dissimilar Friction Stir Welding of Low & High Melting Point Alloys and Its Numerical Thermal & Fluid Flow Analysis
    (2023) Pankaj, Pardeep
    A comprehensive understanding of metallography, heat generation, plastic deformation, and material flow/intermixing associated with the tool–workpiece intersection is required to substantially eradicate defects from the dissimilar friction stir welded joints. In this dissertation, an attempt was made to address the optimal dissimilar friction stir welding (FSW) process window through the experimental analysis, supported by the numerical modelling. The dissimilar material combination, i.e., shipbuilding grade DH36 steel & AISI 1008 steel, DH36 steel & 6061-T6 aluminum alloy (AA6061), and 304 stainless steel (304 SS) & AA6061 are chosen for the study. In the experimental work, the weld joints were characterized based on the mechanical performance, macro/microstructural studies, and quantification of intermetallic compounds (IMCs) & steel fragments. It is understood that the grain refinement and IMCs could improve the hardness. However, the thicker IMC layer and larger area fraction of steel fragments and IMCs reduced the joint strength and ductility of the joints. Numerically, the 3D transient thermal phenomenological models were established to compare the thermal history between FSW and plasma-assisted FSW of dissimilar steels. On the other hand, the steady-state multiphase thermal-fluid flow analysis based on computational fluid dynamics by incorporating a modified analytical model was performed for the steel & AA6061 combination. The volume of fluid method was implemented for the DH36 steel & AA6061 combination. A multi-species transport model (STM) coupled with a mixture model was established to simulate the dissimilar 304 SS & AA6061 joints for the first time. The simulation results revealed that the variation in welding parameters significantly affected the temperature and material flow properties (i.e., flow velocity, dynamic viscosity, and strain rate) and material intermixing around the high-speed rotating tool. The developed STM can capture the transversal/horizontal material flow features and embedded steel fragments/strips in the joints
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    Formability and Failure Response of AA5052-H32 Sheets Deformed using a Shock Tube
    (2022) Barik, Saibal Kanchan
    The emerging interest to minimize fuel consumption and carbon emission, lightweight component design has become one of the important goals in the automotive industries. Among the lightweight materials, aluminium alloys are used significantly in automotive body construction because of their acceptable strength to weight ratio, toughness, ductility, and corrosion resistance. However, the limitations include the moderate formability in the conventional sheet forming processes at room temperature and significant springback during stamping of complex geometries. Thus, improving the formability of aluminium alloys receives much attention in the stamping industries. Generally, warm forming and high-velocity forming are preferred to improve the formability of aluminium alloys. However, heating metals during deformation imposes an additional cost to the forming operation. Thus, various high-velocity forming processes are in demand because the inertial effect developed during these processes that delays necking by developing additional tensile stress outside the neck resulting in enhanced formability. In the recent past, various high-energy rate forming (HERF) processes such as electro-magnetic forming (EMF), electro-hydraulic forming (EHF) and explosive forming (EF) have been preferred to fabricate net-shaped products without any defects. Despite several advantages of HERF processes, the major limitations are the higher capital cost, difficulties in machine handling, and requirement of skilled persons.
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    Development of New Displacement-based Methods for the Computation of Notch Stress Intensities of Sharp V-notches
    (2022) Hussain, Mirzaul Karim
    Brittle fracture assessment of engineering components or structures containing sharp V-notches is an important and evolving research area in the field of notch fracture mechanics. A large number of brittle fracture criteria have been developed based on the notch stress intensity factor (NSIF). Therefore, a great deal of effort has been put forward to develop various analytical, experimental, and numerical methods for determining the NSIFs accurately. In the case of complex configurations with complex boundary conditions, many numerical methods, particularly finite element method (FEM) based methods, have been proposed over the years. Different stress-based, displacement-based and energy-based methods have been proposed in connection with the FEM. Many factors of the FEM and of the V-notches have a serious effect on the accuracy of the computed NSIFs. An important aspect of the finite element analysis of the sharp V-notch problems is the lack of special or singular notch tip elements to model the singularity at the notch tip. As a consequence, the current practice is to use the conventional (mostly the isoparametric quadrilateral element (Q8)) elements at the notch tip as well as in the rest of the analysis domain. Moreover, due to the presence of the rigid body terms in the displacement field, unlike the crack problems, the notch opening displacement (NOD) and notch sliding displacement (NSD) are rarely used for the calculation of the NSIFs. Indeed, due to the presence of these rigid body terms, very few displacement-based methods are currently available for the determination of the NSIFs. In the present investigation, two simple, rugged, and efficient finite element displacement-based methods are proposed, which utilize the NOD and NSD to compute the pure mode I, pure mode II and mixed mode (I/II) NSIFs of two-dimensional sharp V-notched configurations subjected to arbitrary in-plane loading. In the first method, certain special properties of the notch tip Q8 elements are investigated, and as a result, an optimum point on the notch tip element is identified for the first time where the displacements are found to be more accurate. Using the NOD and NSD at this point, the NSIFs are calculated. In the second method, the NSIFs are determined using a collocation method in which the NOD and NSD quantities at the recommended collocation nodes along the notch flanks have been employed such that the formulation neatly bypasses the rigid body displacement terms. Both the methods are used to determine the NSIFs of various pure mode I, pure mode II and mixed mode (I/II) benchmark problems, and the results are compared with the available reference solutions. The results obtained using the present methods show an excellent agreement with the published results. Further, the variation of the computed NSIFs using both the proposed method with the notch angle is in accordance with the theoretical and previous predictions. Many factors of the NSIF extraction methods, such as varied formulations, field variables sampled, location/areas of the sampling points and number of sampling points, etc., are known to affect the accuracy of the NSIFs. Furthermore, the use of the conventional elements at the notch tip in all of these methods also greatly affects the accuracy of the solution. Considering the impact of the above factors on the accuracy, to date, no comprehensive comparison of the above methods exists. Another aim of the present investigation is to conduct a comparison of the various available stress, displacement, and energy-based methods, including the two proposed displacement-based methods in order to study their performance in terms of accuracy of the computed NSIFs and the number of sampling points considered. By comparing all the methods, conclusions of practical relevance have also been provided.
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    Uniform Finishing of Complex Profiles using Rotational Magnetorheological Fluid-based Finishing (R-MRFF) Process
    (2022) Kumar, Manjesh
    The surface roughness of any component is a major concern in the medical, automotive, aerospace, military, and other industries. The performance and life of the components depend primarily on their surface quality. The components explored in the current study for finishing purposes are miniature gear and poppet valve. The poppet valve accurately regulates the perfect air/fuel mixture into the combustion chamber of a gas propulsion engine or internal combustion (IC) engine to reduce hydrocarbon emissions. Miniature gears are used in biomedical devices for pumping, cutting, and various other works, also in small servo motors, which are widely used in the UAVs, automotive, and aerospace industries. Previous finishing methods (mentioned in the literature) generate defects like burrs, pits, scratches, dents, etc. The uniform nano-scale finishing on such components is tough to achieve due to constraints related to the fixture design and fixture material. The surface roughness requirement of these complex components is at the nanometer level and should be uniform over the entire surface. The rotational magnetorheological fluid-based finishing (R-MRFF) process is proposed in the present study to counteract the problems faced during finishing miniature gear and poppet valve profiles while providing the required uniform surface finish and surface characteristics. A novel flow restrictor and workpiece fixture are designed and developed to uniformly nano-finish SS316L miniature gear teeth profiles. Also, a novel magnet fixture is designed and developed to nano-finish Nickel-Al-Bronze alloy (AB2 grade) based poppet valve ridge profiles uniformly. Magnetorheological (MR) polishing fluid is used in the R-MRFF process to finish both components.
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    GPU-based Strategies for Accelerating Topology Optimization of 3D Continuum Structures using Unstructured Mesh
    (2023) Ratnakar, Shashi Kant
    Topology optimization is a complex and time-consuming process used to develop the early conceptual design of industrial products. With the advancement of cost-effective many-core high performance computing architectures such as GPU, the challenge of high computational cost has been addressed. However, the development of efficient GPU computing strategies for the topology optimization of large-scale 3D continuum structures remains a challenge. This thesis aims to address some of the major challenges in GPU-based acceleration of structural topology optimization discretized by 3D unstructured meshes. In the first part of this thesis, a GPU-based finite element analysis (FEA) solver is developed. The proposed preconditioned conjugate gradient (PCG) FEA solver is equipped to handle large-scale 3D unstructured meshes efficiently. It employs a matrix-free or assembly-free strategy in which GPU threads solve the system of linear equations at the elemental or nodal level. The second part of the thesis focuses on enhancing the computational performance of the proposed GPU-based FEA solver by developing efficient GPU thread allocation strategies. The analysis of the results demonstrates a significant improvement in the computational performance as compared to the conventional GPU-based strategy from the literature. The proposed GPU-based FEA solver is further improved by reducing the amount of CPU-GPU data transfer and developing novel data storage and data access patterns on the GPU, which reduces the amount of GPU memory required by the FEA solver. The efficient GPU computing strategies proposed in this thesis accelerate the major computational bottlenecks of the GPU-based matrix-free FEA solver, resulting in a topology optimization framework with much less execution time and reduced memory consumption.