Mechanical Engineering Commons^™

Static Response Calibration Of 3d Printed Thin Walled Structures Using Fused Deposition Modelling, Akhilesh Ravindra Kulkarni

Mechanical and Aerospace Engineering Theses - Archive

3-D printing has enabled flexible, tool-less fabrication that yields numerous benefits. One benefit is unique and complex structural arrangements that increase design freedom to minimize weight. Such arrangements can be guided by advanced topology, shape, and sizing optimization tools using appropriate process constraints to ensure a printable design and can include highly integrated structural details such as stiffeners, flanges, frames, and other connections. 3D printing thin wall aircraft structures presents challenges for material and structural characterization. 3D printing enables integrated structural details, each detail is affected by the print process capability to fabricate the local geometry and deviations from designed …

Backstepping Approach For Design Of Cascaded Pid Controller With Guaranteed Trajectory Tracking Performance For Micro-Air Uav, Yusuf Kartal

Mechanical and Aerospace Engineering Theses - Archive

Flight controllers for micro-air UAVs are generally designed using Proportional- Integral-Derivative (PID) methods, where the tuning of gains is difficult and time-consuming, and performance is not guaranteed. In this thesis, we develop a rigorous method based on the sliding mode analysis and nonlinear backstepping to design a PID controller with guaranteed performance. This technique provides the structure and gains for the PID controller, such that a robust and fast response of the UAV for trajectory tracking is achieved. First, the second-order sliding variable errors are used in a rigorous nonlinear backstepping design to obtain guaranteed performance for the nonlinear UAV …

Analysis Of Laminated Curved Beam With And Without Defects And Imperfections, Wei-Tsen Lu

Mechanical and Aerospace Engineering Dissertations - Archive

Several studies have focused on the modeling and response characterization of composite structural members, with particular emphasis on composite curved beams. The class of curved beam is explored to determine mechanical response in primary aerospace structural applications. The present work focuses on developing analytical closed-form solutions for investigating composite curved beams with and without fiber waviness and delamination. The present work can efficiently characterize the structural behavior of composite curved beams under bending. This work shows the development of a novel mathematical approach to predict structural performance by investigating axial stiffness, bending stiffness with consideration of shear deformation in composite …

Electrowetting-On-Dielectric (Ewod) Digital Microfluidic Device For Synthetic Organic Chemistry, Matin Torabinia

Mechanical and Aerospace Engineering Dissertations - Archive

Over the past decades, microscale chemical reaction technology has been attractive in diverse areas of chemistry. It allows the precise control of quantified reagents and highly efficient heat and mass transfer, because of a large interface-to-volume ratio–particularly in case of the exothermic reaction and mixing–, reduced consumption of toxic or expensive agents, improved reaction profiles, and enhanced selectivity compared to macro-scale reactions. The mainstream microscale reaction processes were established using continuous microchannel flow systems, which has emerged as a powerful complement to batch chemistry on the laboratory scale due to relative advantages, some of which include: increased safety, more accurate …

An Implementation Of The Regularized Extended Finite Element Method In Abaqus, Yu-Jui Liang

Mechanical and Aerospace Engineering Dissertations - Archive

The Regularized eXtended Finite Element Method (Rx-FEM) methodology is a discrete damage modeling (DDM) technique, which represents an approach to the progressive damage analysis (PDA) in laminated composites when multiple damage events such as matrix cracks and delamination are introduced into the model via the displacement discontinuities. In the Rx-FEM, the Heaviside step function that is typically used to introduce a displacement discontinuity across a crack surface in the eXtended Finite Element Method (x-FEM) is replaced by a continuous function approximated by using the finite element (FE) shape functions. This regularization offers unique possibility for the implementation of the Rx-FEM …

Material Characterization And Fracture Prediction Of Fdm Printed Parts, Sanchita Sheth

Mechanical and Aerospace Engineering Theses - Archive

In order to take advantage of the design freedom that Additive Manufacturing offers, most applications require reliable material characterization. This can ensure that a design performs within its environment and life requirements. This work discusses two models. One investigates the raster angle dependency of stiffness properties and the other numerically predicts fracture in Fused Deposition Modeling (FDM) printed polymer parts. Pre-processing of FDM geometry was done in Abaqus CAE (SIMULIA TM). FEA and post-processing was done in BSAM, which is a damage prediction software developed for composites. BSAM uses a regularized extended finite element approach of Discrete Damage Modeling. In …

A Robust Controller Design For A Tailless Uav With Effective Control Allocation, Ethem Hakan Orhan

Mechanical and Aerospace Engineering Theses - Archive

Attempts to completely remove the tails from aircraft can be dated back to the early days of modern aviation. A number of stability and control problems arising from the unique characteristics of the configuration resulted in poor handling qualities and some dangerous flight characteristics in the early designs. Lately, this configuration is becoming widespread again and the current state-of-the-art of fly-by wire technology and modern control design techniques enable design of tailless aircraft which are safe to fly. In this thesis, a study on the application of modern robust control design techniques on a tailless UAV is presented. A nonlinear …

Estimation Of The Fatigue Life Of Additively Manufactured Metallic Components Using Modified Strain Life Parameters Based On Surface Roughness, Peter Grohs

Masters Theses

In this study, a method is developed to estimate the effects of surface roughness on the fatigue life of additively manufactured titanium Ti6Al4V, aluminum 7075–T6, and steel 4340 alloys through modified strain life parameters using finite element analysis (FEA). This method is highly beneficial to the fatigue analysis of as-built additively manufactured metal components, which possess rough surfaces that reduce fatigue life significantly but are challenging to analyze directly using finite element simulation because of complex geometries, i.e., modeling an exact surface profile is arduous.

An effective stress concentration factor, incorporating roughness data, is defined to quantify their effects on …

Characterization Of Thermo-Mechanical Properties Of Copper Nano-Particles Infused Acrylonitrile Butadiene Styrene (Abs)- 3d Printed Specimens, Viswajit Talluru

Mechanical and Aerospace Engineering Theses - Archive

Now a days the use of metal nanoparticle infused polymer is becoming widespread, since the development of polymer with enhanced thermal properties are being used for the growth of electronic packaging industry. In this study, copper nanoparticles are mixed with the Acrylonitrile Butadiene Styrene (ABS) thermoplastic in varying mass proportions, to observe the changes in thermal and structural properties of ABS. As expected, the extruded wire with high nano-particle concentration exhibited much higher thermal conductivity than its raw ABS form. For the case of 2% copper nanoparticle infused ABS using one dimensional steady state heat flux method though extrude wire …

Axial Compressor Based On Plastic Additive Manufacturing, Chris Phu

Mechanical Engineering Undergraduate Honors Theses

Turbomolecular pumps designed to function in very low pressures tend to be too prohibitively expensive for student researchers. On the other hand, while conventional pumps are affordable, they can’t function in extreme low pressures. An additively manufactured axial compressor however is inexpensive to manufacturer and only needs to be build up enough pressure for a conventional pump to function. After many design iterations, a final iteration that is near vacuum chamber ready has been 3D printed and tested for spin functionally. The designed axial compressor is easy to assemble and very modular. Conclusions from each of the design iterations is …

Dynamic Pressure Sensing For The Flight Test Data System, Marc Y. Goupil

Master's Theses

This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation …

A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa

Dissertations

This dissertation explores a novel method of solving low-thrust spacecraft targeting problems using reinforcement learning. A reinforcement learning algorithm based on Deep Deterministic Policy Gradients was developed to solve low-thrust trajectory optimization problems. The algorithm consists of two neural networks, an actor network and a critic network. The actor approximates a thrust magnitude given the current spacecraft state expressed as a set of orbital elements. The critic network evaluates the action taken by the actor based on the state and action taken. Three different types of trajectory problems were solved, a generalized orbit change maneuver, a semimajor axis change maneuver, …

Experimental Characterization Of Thermal-Hydraulic Performance Of A Microchannel Heat Exchanger For Waste Heat Recovery, James Yih, Hailei Wang

Mechanical and Aerospace Engineering Faculty Publications

Given size and performance advantages, microchannel heat exchangers are becoming increasingly important for various energy recovery and conversion processes. In this study, detailed experimental measurements were conducted to characterize flow and heat transfer performance of a microchannel heat recovery unit (HRU) manufactured using standard photochemical etching and diffusion bonding processes. According to the global flow and temperature measurement, the HRU has delivered the predicted thermal performance under various oil and air flow rates. As expected, the heat transfer effectiveness varies between 88% and 98% for a given air and oil flow rates while it increases with air inlet temperature due …

An Investigation Of High-Speed Consolidation And Repair Of Carbon Fiber - Epoxy Composites Through Ultrasonic Welding, David A. Hoskins

LSU Master's Theses

Adhesive repair of carbon fiber composite structures is commonly done on damaged structures to extend the service life. This method requires careful preparation of the damaged surface with intricate steps to ensure good bonding between the repair patch and the parent structure by means of an adhesive film. As with many forms of composite manufacturing, it is required to perform vacuum bagging, debulking, and a heated cure depending on the resin. All these steps make the repair process costly and time consuming.

In this present work, an alternative method of repair is investigated which explores the experimental feasibility of using …

Sustainable Aviation Fuels Approval Streamlining: Auxiliary Power Unit Lean Blowout Testing, Erin E. Peiffer, Joshua S. Heyne, Meredith Colket

Mechanical and Aerospace Engineering Faculty Publications

An underpinning hindrance in the market penetration of sustainable aviation fuel is the approval process for alternative jet fuels. One solution to this is to develop low-cost screening tools that can be implemented earlier in the approval process. Auxiliary power unit combustors historically show the most sensitivity to physical and volatile fuel properties, making it a useful tool in assessing potential alternative jet fuel effects at test conditions representative of operability stability limits. It is hypothesized that these observations can be explained via timescale analysis considering fuel droplet breakup and evaporation, combustor mixing, and chemical reactivity timescales on the progression …

Transport Phenomena In The Knudsen Layer Near An Evaporating Surface, Eric Bird, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using the Combination of the Kinetic Theory of Gases (KTG), Boltzmann Transport Equation (BTE), and Molecular Dynamics (MD) Simulations, We Study the Transport Phenomena in the Knudsen Layer Near a Planar Evaporating Surface. the MD Simulation is First Used to Validate the Assumption Regarding the Anisotropic Velocity Distribution of Vapor Molecules in the Knudsen Layer. based on This Assumption, We Use the KTG to Formulate the Temperature and Density of Vapor at the Evaporating Surface as a Function of the Evaporation Rate and the Mass Accommodation Coefficient (MAC), and We Use These Vapor Properties as the Boundary Conditions to Find …

Extension Of A Penalty Method For Numerically Solving Constrained Multibody Dynamic Problems, Troy Newhart

Mechanical & Aerospace Engineering Theses & Dissertations

Numerical analysis of constrained static and multibody dynamic systems has become an integral part of engineering analysis with the continued improvements in technology and software availability. Many methods currently exist for numerically solving constrained static and dynamic systems. The applicability of a penalty method for constrained static solutions is observed in many academic texts and papers. The appeal for using a penalty method in statics pertains to its ease of implementation, computational suitability, and accuracy. This thesis extends a static penalty method for use with constrained multibody dynamics to observe if the penalty method’s benefits are similar for a dynamics …

Aircraft Hydraulic Systems - Fundamentals, Nihad E. Daidzic

Aviation Department Publications

Aircraft hydraulic systems are essential non-propulsive power systems. Hydraulic power systems are used to power major functional aircraft systems, such as flight controls (primary and secondary), friction braking, nose gear steering, thrust-reversers, operating heavy cargo doors, etc.

Rare But Conceivable: Determining The Likelihood Of Meteors And Other Infrequent Events, Michael S. Schmidt, Maria Vega-Westhoff

Engineering Management and Systems Engineering Faculty Research & Creative Works

In the aftermath of a rare but devastating disaster, there is a tendency to overestimate how frequent such an event may be, hence a tendency to overestimate the risk associated with such an event. Those concerned with process safety will acknowledge that though rare, events like meteors, hurricanes, and airplane crashes that can impact chemical plants are conceivable. Typically, though, they have nothing more than feelings to decide whether these events are likely enough to be considered "credible." This compiles data from the literature for several "meteors," both natural and man-made, that often become a cause of general concern after …

Reliability-Based Design Optimization Of Load Sharing Systems Using Ssi-Markov Models, Arun Bala Subramaniyan, Rong Pan, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a novel single loop approach to design the components of the load sharing systems by optimally allocating the failure probabilities to each component, thereby satisfying the overall system reliability requirement. The Reliability–Based Design Optimization (RBDO) of load sharing systems is computationally intensive due to the dynamic nature of component failure probabilities, since the failure of one component will vary the failure probabilities of other working components. Many RBDO methods have been successfully utilized to design individual components, however using these methods for handling system level reliability constraints is still a challenging task. This is because of a …

Nonlinear Control Of Unmanned Aerial Vehicles With Cable Suspended Payloads, Ameya Godbole

Mechanical and Aerospace Engineering Dissertations - Archive

The research focuses on the mathematical modeling and control of an unmanned aerial vehicle with cable suspended payload. A comprehensive mathematical model is derived for a quadcopter with a cable suspended payload using the Newton-Euler method and the Euler-Lagrange formulation. These methods assume that the cable is massless and always taut and cannot be used to simulate the cases when the cable is flexible. Hence, an alternative approach to model the flexibility of the cable is presented using Lagrangian mechanics by approximating the cable to be a chain of serially connected links. The motion of the payload induces disturbances on …

Modeling And Simulation Of Contact And Impact Dynamics In Multibody Systems, Abhishek Chatterjee

Mechanical and Aerospace Engineering Dissertations - Archive

Contact and impact analyses are an essential part of multibody dynamic simulations. Modeling of contact and impact problems have applications in a wide variety of areas including robotics, earthquake engineering, computer graphics, and manufacturing. Collisions between objects typically take place over surfaces that are represented by a set of points in the operation space, thereby requiring multi-point contact and impact analysis. Analysis of multi-point contact and impact may lead to indeterminate (underdetermined) problems with more number of unknowns (contact forces) than equations. This work pertains to the problem of resolving multi-point contact and impact problems in multibody systems consisting of …

Numerical Simulation Of Biodiesel Synthesis In A Continuous Flow Microreactor And A Porous Media Reactor, Terdsak Neadkratoke

Mechanical and Aerospace Engineering Dissertations - Archive

Biodiesel has become an increasingly popular fossil fuel substitute in recent years. Constant attempts are being made to develop new technology that increases the efficiency and yield of biodiesel production units. Numerical simulation can play an integral role in evaluating new reactor designs or optimizing existing ones. Various attempts have been made to develop an accurate computational model that represents biodiesel production. Many computational models for transesterification are based on simplified kinetic models that do not include the effect of saponification. Furthermore, many models assume isothermal conditions and uniform spatial concentrations. Therefore, these models would not be appropriate for evaluating …

Predicting Crack Initiation And Early Crack Growth Behavior Of Pure Nickel Using Surface Topography Analysis, Jalal Fathi Sola

Mechanical and Aerospace Engineering Dissertations - Archive

Fatigue has long been studied as the most critical loading mode for man-made structures. Despite the advances in material behavior characterization and numerical calculation, many structures unexpectedly fail before their designed life. Most of the studies in crack initiation are solely for describing the material and failure behavior and are not capable of predicting the failure before it starts. In addition, most of the fatigue crack growth models are based on the Paris Model with some modifications, which their application is limited to long crack. This implies that finding new methods which can reliably predict material failure is very important. …

A Numerical Study Of Cavitating Flows Based On Plic-Vof Method For Arbitrary Unstructured Meshes, Dezhi Dai

Mechanical and Aerospace Engineering Dissertations - Archive

Cavitation appears when local static pressure drops below the water vapor pressure and causes significant impacts on marine propeller blades. The Volume of Fluid (VOF) method, which is also referred to as the Transport Equation-based Model (TEM), has been extensively adopted in the cavitating flow simulations. Piecewise Linear Interface Calculation (PLIC) schemes have been extensively employed in the VOF method for interface capturing in numerical simulations of multiphase flows. Polyhedral unstructured meshes are often adopted due to their geometric flexibility and superiority in gradient calculation. Four analytical interface reconstruction algorithms in the PLIC-VOF method for arbitrary convex polyhedral cells have …

The Effect Of Controlled Nanomaterial Deposition Towards Electrodes For Microbial Fuel Cells And Electrolysis Cells, Bryan Dennis Steinhoff

Mechanical and Aerospace Engineering Dissertations - Archive

Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are relatively new energy harvesting technologies that utilize the bacteria in wastewater or other organic-rich aqueous media to produce either electricity or hydrogen gas, respectively. Given that MFCs and MECs are newer technologies, there has been many works over the past two decades that have provided understanding into how modifying electrode surface chemistry can improve these cells. It has been widely known that increasing the surface functional groups of MFC anodes, either chemically or thermally, causes the cell power density to increase dramatically. Since MFCs and MECs use the same anodes, …

Multi-Variable Optimization To Improve Temperature Uniformity In Burn-In Applications Subjected To Significant Thermal Shadowing, Ajinkya Suhas Mahajan

Mechanical and Aerospace Engineering Theses - Archive

Burn-in test typically employs voltage and/or temperature to accelerate the appearance of latent reliability defects in semiconductor devices. As a result, burn-in becomes a critical step in the parts screening process and is the primary technique to eliminate defective parts in the early phase of the product life. Thermal control in burn-in processes is generally achieved by either active or passive thermal controlling. In an active thermal control, each device has an individual temperature monitoring system to maintain a specific temperature in which the cooling/heating of each socket is controlled by an individual fan or heater. Whereas in passive thermal …

An Exploratory Study On Continuous Wave Laser And High-Speed Camera Combination In Planar Particle Image Velocimetry For Low Speed Flows, Bunyamin Gencler

Mechanical and Aerospace Engineering Theses - Archive

This study investigates the feasibility of using continuous wave lasers and high-speed CMOS cameras together in 2D particle image velocimetry (PIV) which is a widely-used non-intrusive method in experimental aerodynamics. In order to validate the setup, laminar and turbulent boundary layers over a flat plate with elliptical leading edge are examined in a low-speed wind tunnel. Before the experiments, the suitability of the elliptical-nose flat plate is determined (i.e. pressure gradient over the surface and separation), and the free-stream conditions (flow velocity and test section turbulence) are measured. To strengthen the validation of the setup, numerical simulations are added to …

Effect Of Sulfur - Porous Carbon Cathode Morphology On The Discharge Process In Lithium-Sulfur Battery, Sabarinathan Pushparajsubramaniyan

Mechanical and Aerospace Engineering Theses - Archive

In the present era, Lithium-ion (Li-ion) batteries are most commonly used in all electronic devices, but the demand for alternative energy increases rapidly due to the catastrophic climate caused by excess use of fossil fuels in automobiles. Li-ion batteries cannot fully satisfy the need as its theoretical capacity is low, and the cathode cost is high. On the other hand, Lithium-Sulfur (Li-S) battery meets the requirement with the highest theoretical capacity of Sulfur 1672 mAh/g. Lithium anode and Sulfur cathode together form to be having the highest energy density. The highest energy capacity of Sulfur is achieved by the conversion …

Comparative Cfd Analysis Of The Effect Of Air And Liquid Cooling On The Form Factor Of Gpu Server, Ankit Bharatkumar Sutaria

Mechanical and Aerospace Engineering Theses - Archive

Artificial intelligence (AI) has becoming an important area which may significantly impact everyone’s daily life. This means a lot of high-performance chips such as high-performance CPU, GPU, FPGA (Field-programmable gate array), ASIC (application specific integrated circuit) devices may need. The thermal design power (TDP) of these chips are high, and now it is very common to see a processor TDP reaches as high as 300Watts[1]. When these high-power density processors are packaged together, the power density of the servers and compute boxes are significantly high. Traditional air-cooling is approaching its cooling capability limitation, especially when a cluster of racks is …