http://dspace.dtu.ac.in:8080/jspui/handle/123456789/108 2026-11-04T00:48:37Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/23380 Title: NUMERICAL ANALYSIS OF PULL-IN VOLTAGE OF FIXED-FIXED BEAM MEMS ACTUATOR INCORPORATING MATERIAL AND GEOMETRY VARIATIONS Authors: GUPTA, PRIYANKA; Gautam, Vijay (SUPERVISOR); Prasad, Bijendra (CO-SUPERVISOR) Abstract: Microelectromechanical systems (MEMS) electrostatically actuated fixed-fixed beam actuators are ubiquitous in RF switches, tunable varactors, resonant sensors, and optical micro-mirrors. The pull-in instability, the critical electromechanical event at which the electrostatic attractive force irreversibly overcomes the elastic restoring force of the beam defines the safe operating voltage ceiling of every such device and is the primary design constraint in MEMS electromechanical engineering. This thesis presents a systematic coupled electromechanical finite element investigation of fixed-fixed beam MEMS actuators in COMSOL Multiphysics v6. Three structural materials- gold (Au, E = 79GPa), molybdenum (Mo, E = 329GPa), and tungsten (W, E = 411GPa) are investigated for three beam lengths (100μm, 150μm, and 230μm), with a fixed cross-section of 7μm × 0.5μm and an initial air gap of 0.9μm, yielding nine simulation configurations. For each configuration, parametric voltage sweeps at 0.1V increments deliver: (i) the pull-in voltage; (ii) the mid-span displacement versus voltage curve; (iii) the peak von Mises stress versus voltage curve; (iv) the full arc-length displacement and stress profiles at pull-in; and (v) three-dimensional volumetric displacement and stress field renderings at representative intermediate voltages. Pull-in voltages range from 0.68 V (Au, 230μm) to 10.0 V (W, 100μm), a 14.7 fold span. The scaling law Vpi ∝ E (1/2) · L (-3/2) is confirmed across all nine configurations with R² ≥ 0.997 in log-log regression. The universal one-third gap pull-in criterion (mid span displacement = g₀/3 = 0.167μm) is verified for all configurations. Arc-length von Mises stress profiles exhibit a characteristic triple-lobe pattern with primary peaks at the anchor junctions 2.4-2.8× higher than the mid-span plateau, identifying the anchors as the fatigue-critical hot spots. Peak stresses at pull-in range from 2.1 MPa (Au, 230μm) to 28.0 MPa (W, 100μm), yielding stress safety margins of 24× to over 144× against material yield strengths. Three-dimensional field maps confirm that electromechanical instability 5 is the universal failure mode. Results are validated against published analytical models and experimental data from the literature, with agreement within 5%. The thesis provides a comprehensive parametric design database and scaling law verification for fixed-fixed beam MEMS actuators that are directly actionable by MEMS designers and process engineers engaged in RF switching, inertial sensing, and optical MEMS applications. 2026-09-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/23359 Title: NUMERICAL ANALYSIS AND VISUALIZATION OF SHOCK STRUCTURES IN A CONVERGENT-DIVERGENT NOZZLE Authors: ALAM, MEHARBAN; ZUNAID, MOHAMMAD (SUPERVISOR) Abstract: High-speed gas flow through Convergent-Divergent Nozzles is a fundamental aspect of aerospace and propulsion engineering, where efficient energy conversion is critical. This study presents a detailed numerical investigation of shock structure formation and flow behaviour within a Convergent-Divergent nozzle. Although the nozzle is initially designed for a Mach number of 2.0, the analysis reveals that the exit Mach number varies significantly with nozzle pressure ratio, ranging from approximately 2.1 under over-expanded conditions (NPR ≈ 6.81) to about 2.7 under under-expanded conditions (NPR ≈ 12.25) based on boundary conditions. A Computational Fluid Dynamics approach is employed using a density-based implicit solver to simulate compressible flow across different regimes, including choked, over-expanded and under-expanded conditions. The study evaluates variations in key flow parameters such as Mach number, static pressure, temperature, and velocity, highlighting their dependence on NPR and nozzle geometry. The results provide detailed visualization of shock structures and their propagation within and downstream of the nozzle. It is observed that both the location and intensity of shock waves are strongly influenced by NPR. The findings are consistent with compressible flow theory and contribute to a better understanding of shock dynamics, offering valuable insights for optimizing nozzle design and improving performance in high-speed propulsion systems. 2026-05-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/23358 Title: NUMERICAL AEROTHERMAL ANALYSIS OF A HYPERSONIC MISSILE AT VARIOUS MACH NUMBERS Authors: NIRANJAN, DEVANG; ZUNAID, MOHAMMAD (SUPERVISOR) Abstract: Hypersonic Missiles are the type of missiles which are regarded as the fastest in the world, and they are currently being researched and developed in various regions of the world. It works with Mach numbers greater than 5. In this study, we examine the behavior of hypersonic missiles operating at a specific height under various flow field conditions at Mach numbers 5, 7, and 10, as well as the behavior of heat transfer loads on the hyperbolic profile structure. The flow architecture and behavior of shock waves are being numerically simulated. This study contributes to an understanding of the design considerations for hypersonic missiles operating at various heights and atmospheric conditions and it will also help in thermal designing of hypersonic vehicles so that proper thermal management can be designed. The results indicate distinct relationship between the Mach number and the thermal and aerodynamic characteristics at the nose tip and along the body. It is evident that as the Mach number increases from 5 to 10, the intensity of the Mach number decrease near the nose tip becomes more pronounced, leading to increased thermal loads on the missile. The data presented highlights that at Mach number 5, the nose tip temperature reaches approximately 2,000 K, while increasing the Mach number to 10 raises the peak temperature to around 2,300 K. However, the temperature decreases more gradually with length at Mach number 10 compared to Mach number 5 and 7. This suggests that although higher Mach numbers result in more nose tip temperatures, the rate of temperature decrease along the body is not proportional to the Mach number increase, warranting further investigation into the thermal protection requirements for missiles operating at these speeds. 2026-05-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/23225 Title: INDUSTRY 4.0 IN SMART MANUFACTURING Authors: SACHAN, NAMAN; Yuvraj, N. (SUPERVISOR) Abstract: Industry 4.0 has revolutionized the conventional manufacturing sector by introducing advanced digital technologies like the Internet of Things (IoT), artificial intelligence (AI), machine learning (ML), cloud computing, cyber-physical systems (CPS), digital twins, and big data analytics to manufacturing processes. Smart manufacturing systems, using Industry 4.0 concepts, can be used to improve operational efficiency, minimize unplanned downtime, improve product quality, facilitate real-time decision-making, and contribute to sustainable industrial practices by implementing intelligent automation and highly interdependent manufacturing environments. This research addresses various directions of Industry 4.0 technologies in smart man ufacturing systems development and research on measurable effects on productivity, sustainability, predictive maintenance, supply chain optimization, and operational flex ibility. The study is a thorough literature review of over sixty research papers covering all the reputed international journals and conference proceedings on the topic of Indus try 4.0 and the smart manufacturing technologies. Bibliometric analysis is also carried out to elucidate the trend of growth, the contribution of research work by countries, frequent keywords, and technological development in the area. The research covers the enabling technologies of Industry 4.0, like artificial intelligence, machine learning, cloud manufacturing, additive manufacturing, autonomous robotics, IoT sensor systems, digital twins, and cyber-physical systems. The challenges related to the implementation of these technologies in manufacturing environments, such as cybersecurity risk, cost of technology adoption, interoperability of data, skill gaps of the workforce, and resistance from the organization, are discussed critically. The results show that Industry 4.0 greatly enhances manufacturing efficiency, produc- iv tion flexibility, the ability to predict maintenance needs, and supply chain visibility and promotes sustainable production practices. Based on the research, intelligent, data-driven, and autonomous manufacturing systems are the future of global industrial production, and for their successful and sustainable adoption, strategic investments, or ganizational readiness, skilled workforce development, and strong cybersecurity frame works are essential. 2026-05-01T00:00:00Z