Mechanical Engineering Commons^™

Effect Of Stress Concentrations On Fatigue Of Composite And Metallic Structures, Ross Henry Falen

Masters Theses

"The complex shapes of hydrokinetic turbine blades can include part features such as a fillet, step, or hole. Situations can arise where two part features, such as a hole and a fillet, may be in close proximity which can introduce stress concentrations within the blade structure, adversely affecting the structure's life. Because the interaction between the part features isn't well known, fatigue data is needed to determine the proper analysis.

In this thesis, two separate topics are discussed and investigated. The first topic deals with stress concentrations in hydrokinetic turbine blades. Several blade designs were tested and improved upon to …

Characterization Of 304l Stainless Steel By Means Of Minimum Input Energy On The Selective Laser Melting Platform, Ben Brown

Masters Theses

"Developing parameter sets for new materials on the Selective Laser Melting (SLM) platform has traditionally been done through the use of single line processing windows and a basic design of experiments (DOE) which would include varying machine parameters to maximize density. This study expands the traditional method by determining the main effects statistically for density, allowing for a more in depth analysis wherein the experimental results are statistically correlated to the variable machine parameters used. With this analysis, parameter optimization with respect to achieving near full density, while also considering build rates, can be performed. New parameters for 304L stainless …

Fabrication Of Out-Of-Autoclave Bismaleimide Based Composite Laminates With Embedded Fiber Optic Sensors, Sudharshan Anandan

Masters Theses

"Composites are becoming the material of choice in applications where weight savings are critical, like aerospace structures. The common composites used are- Carbon/Epoxy and Carbon/Bismaleimide (BMI). BMI based systems are preferred in applications which involve operating temperatures higher than conventional epoxies. Carbon/BMI laminates are traditionally fabricated in an autoclave, which is associated with high operating costs. In this work, a low cost out of autoclave (OOA) process is evaluated. It is desirable to have BMI OOA prepreg systems cure at reasonably low temperatures with sufficient degree of cure and green strength to maintain rigidity for subsequent freestanding post cure Carbon/BMI …

Numerical Analysis Of Thermal Stress And Deformation In Multi-Layer Laser Metal Deposition Process, Heng Liu

Masters Theses

"Direct metal deposition (DMD) has gained increasing attention in the area of rapid manufacturing and repair. It has demonstrated the ability to produce fully dense metal parts with complex internal structures that could not be achieved by traditional manufacturing methods. However, this process involves extremely high thermal gradients and heating and cooling rates, resulting in residual stresses and distortion, which may greatly affect the product integrity. The purpose of this thesis is to study the features of thermal stress and deformation involved in the DMD process. Utilizing commercial finite element analysis (FEA) software ABAQUS, a 3-D, sequentially coupled, thermo-mechanical model …

Mechanistic Identification Of Specific Force Coefficients In Endmilling Inconel 718 Under Four Cooling Strategies, Mahmood Shaman Ameen

Masters Theses

“This thesis presents the results of experimental investigations of the mechanistic identification of specific force coefficients for uncoated bull-nose and uncoated wavy-edge/bull-nose helical endmilling of Inconel 718 under emulsion, minimum quantity lubrication (MQL), cryogenic (LN₂), and combined (MQL + LN₂) cooling. Several slot milling tests were conducted on Inconel 718 workpiece block with depth of cut 1.25 mm. The cutting parameters were varied as: spindle speed, n = 250 and 750 rev/min, feedrate, f = 25–75 mm/min by using uncoated carbide bull-nose helical endmill. Also 24 peripheral milling tests were conducted on Inconel 718 workpiece block …

Machinability Improvement During High-Speed End-Milling Of Inconel 718 Alloy, Chukwujekwu Nnadi

Masters Theses

“This thesis presents the results of the experimental investigation of the effects of machining parameters (spindle speed and feedrate) and cooling strategies [Minimum Quantity Lubrication (MQL), Cryogenic Liquid Nitrogen (LN₂), and combined (MQL+LN₂)] on cutting force components, cutting temperature, tool wear and surface roughness during high-speed slot end-milling of Inconel 718 alloy. In addition, a comparative evaluation of the three cooling strategies was conducted for cutting force components, surface roughness and residual stresses. All end-milling experiments were conducted on a Cincinnati Milacron Vertical Machining center (VMC), using a 0.5 inch (12.7 mm) diameter, 0.03 inch (0.762 …

An Interactive Product Development Model In Remanufacturing Environment: A Chaos-Based Artificial Bee Colony Approach, Vishwa V. Kumar

Masters Theses

"This research presents an interactive product development model in re-manufacturing environment. The product development model defined a quantitative value model considering product design and development tasks and their value attributes responsible to describe functions of the product. At the last stage of the product development process, re-manufacturing feasibility of used components is incorporated. The consummate feature of this consideration lies in considering variability in cost, weight, and size of the constituted components depending on its types and physical states.

Further, this research focuses on reverse logistics paradigm to drive environmental management and economic concerns of the manufacturing industry after the …

Additive Manufacturing Laser Deposition Of Ti-6al-4v For Aerospace Repair Application, Nanda Kumar Dey

Masters Theses

"Parts or products machined from high performance metals are very expensive, partly due to the processing complexities during manufacturing. Therefore, many high performance metal parts users, such as the aerospace industry, mold/die casting industry, heavy machinery consumers etc., extend the service of these damaged parts by employing repair or remanufacturing technology. The research objective is to use laser deposition and machining processes to repair titanium parts.

This thesis discusses a new way of approach for developing a repair process for Ti-6Al-4V for the aerospace industry using Laser Metal Deposition (LMD). The repairs were conducted in a multi-axis hybrid manufacturing systems …

A Driving Simulator Study To Evaluate The Impact Of Portable Changeable Message Signs (Pcms) On Driver Speed Characteristics, Bharath Kolar Venkat

Masters Theses

"This research project examined the effects of sequential Portable Changeable Message Signs (PCMS) on driver behavior in work zones. PCMS are temporary traffic control (TTC) devices, part of Intelligent Transportation Systems, which supplement static signs to provide advance warning and real-time information to drivers. Text and number based messages are displayed on the PCMS for which detailed evaluation has not been carried out before. This research fills this gap using a driving simulator (DS) supplemented by objective and subjective surveys. A work zone on I-44 in rural Missouri was replicated in the DS using video recordings and GIS (Geographical Information …

Modelling Of Directed Energy Deposition Processes, Xueyang Chen

Masters Theses

"The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed.

In the heat transfer and fluid flow model, the governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. …

An Effectiveness - Based Analysis Of Ground Coupled Heat Exchangers, Chou Shen

Masters Theses

"This thesis develops a theoretical framework, termed [Effectiveness] - BLU, to characterize the relation between temperatures, thermal contact and borehole length as it relates to the heat transfer processes in ground coupled heat exchangers used for ground source heat pump systems.

Borehole outflow temperature depends on the inflow temperature, the heat imposed on the borehole and the temperature history of the ground. In addition, variation of outflow temperature influences inflow temperature, even for the case of constant heat pump load. Because of this kind of feedback, the borehole inflow temperature may not be constant even with a fixed building load. …

Performance Analysis Of Cutting Graphite-Epoxy Composite Using A 90,000 Psi Abrasive Waterjet, Aiswarya Choppali

Masters Theses

"Graphite-epoxy composites are being widely used in many aerospace and structural applications because of their properties: which include lighter weight, higher strength to weight ratio and a greater flexibility in design. However, the inherent anisotropy of these composites makes it difficult to machine them using conventional methods. To overcome the major issues that develop with conventional machining such as fiber pull out, delamination, heat generation and high tooling costs, an effort is herein made to study abrasive waterjet machining of composites. An abrasive waterjet is used to cut 1" thick graphite epoxy composites based on baseline data obtained from the …

Impact Of Fracture Spacing And Mechanical Parameter Anisotropy On Fracture Width In Horizontal Wells In Shales, Deepak Gokaraju

Masters Theses

"The success of economically viable production of oil and gas from ultra-low permeability shale reservoirs depends on the creation of an extensive fracture network through hydraulic fracture stimulation. Multiple hydraulic fractures are created simultaneously in each stage to increase the surface area of contact between the wellbore and reservoir. The spacing between fractures is an important component to consider when developing an optimum stimulation design. An important aspect of shale rock properties is that shales are inherently anisotropic with a horizontal plane of isotropy (transversely isotropic) due to their finely layered structure. This study aims to provide an insight into …

Performance Evaluation Of Coaxial Horizontal Axis Hydrokinetic Turbines System, Abdulaziz M. Abutunis

Masters Theses

"Hydrokinetic energy technologies are emerging as a viable solution for renewable power generation. Unlike conventional hydropower turbines, hydrokinetic turbines are environmentally friendly; they operate at zero-head, and do not need dams to preserve the water. Unfortunately, they have a low efficiency which makes their design a challenging task. This work was focused on the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine arrangements and flow conditions.

It was undertaken in an effort to improve the efficiency of small HAHkTs that harness a river's kinetic energy. Four sets of experiments were performed in a water tunnel to investigate …