Mechanical Engineering Commons^™

Cryogenic Burnishing Of Co-Cr-Mo Biomedical Alloy For Enhanced Surface Integrity And Improved Wear Performance, Shu Yang

Theses and Dissertations--Mechanical and Aerospace Engineering

The functional performance of joint implants is largely determined by the surface layer properties in contact. Wear/debris-induced osteolysis and aseptic loosening has been identified as the major cause of failure of metal-on-metal joint implants. A crucial requirement for the long-term stability of the artificial joint is to minimize the release of debris particles.

Severe plastic deformation (SPD) processes have been used to modify the surface integrity properties by generating ultrafine, or even nano-sized grains and grain size gradients in the surface region of many materials. These fine grained materials often exhibit enhanced surface integrity properties and improved functional performance (wear …

Geometric Control Of Inflatable Surfaces, Isaac John Scherrer

Theses and Dissertations--Mechanical and Aerospace Engineering

High precision inflatable surfaces were introduced when NASA created the ECHO 1 Balloon in 1960. The experiment proved that inflatable structures were a feasible alternative to their rigid counterparts for high precision applications. Today inflatable structures are being used in aviation and aerospace applications and the benefits of using such structures are being recognized. Inflatable structures used in high precision structures require the inflatable surfaces to have controllable and predictable geometries. Many applications such as solar sails and radar reflectors require the surface of such structures to have a uniform surfaces as such surfaces improve the efficiency of the structure. …

Experimental Benchmarking Of Surface Textured Lip Seal Models, Wei Li

Theses and Dissertations--Mechanical and Aerospace Engineering

A thorough investigation on the existing hydrodynamic lubrication theories and the reverse pumping theories for the conventional lip seal is conducted. On that basis, the algorithms and the methods used in the numerical modeling of the conventional lip seal are modified and applied to the study of the lip seal running against surface textured shafts. For each step of the study, the numerical model is benchmarked against the experimental results. Important physical mechanisms which explain the reverse pumping ability of the triangular surface structures are revealed. Meanwhile, the accuracy of the numerical model is tested. In general, the numerical simulation …

A New Metric-Based Lca Method For Assessing The Sustainability Performance Of Metallic Automotive Components, Xiangxue Zhang

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis presents a new metric-based Life-cycle Assessment (LCA) method for assessing the sustainability performance of metallic automotive components. The unique feature of this research work include the development and use of a metrics-based product sustainability index (ProdSI) methodology by considering the total life-cycle approach and the triple bottom line (TBL) with the 6R methodology. It has been shown that the manufactured product’s sustainability performance can be comprehensively assessed using this new methodology. The major focus of this research is the integration of the 6R activities (Reduce, Reuse, Recycle, Recover, Redesign and Remanufacture). Four life-cycle stages of the …

Transport Phenomena Associated With Liquid Metal Flow Over Topographically Modified Surfaces, Wen Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

Brazing and soldering, as advanced manufacturing processes, are of significant importance to industrial applications. It is widely accepted that joining by brazing or soldering is possible if a liquid metal wets the solids to be joined. Wetting, hence spreading and capillary action of liquid metal (often called filler) is of significant importance. Good wetting is required to distribute liquid metal over/between the substrate materials for a successful bonding.

Topographically altered surfaces have been used to exploit novel wetting phenomena and associated capillary actions, such as imbibitions (a penetration of a liquid front over/through a rough, patterned surface). Modification of surface …

Finite Element Analysis Of Cancellous Bone, Lucas T. Wilkerson

Theses and Dissertations--Mechanical and Aerospace Engineering

A variety of pathologies exist which increase the likelihood of bone fracture. Present methods for determining the fracture risk of a specific patient are based exclusively on the amount of bone present. While the quantity of bone tissue is correlated with strength, it neglects to account for bone’s intricate microarchitecture. To assess the effect of bone quality on strength, a methodology was developed for the structural analysis of cancellous bone biopsies. Thirty biopsies were selected from a pre-existing biopsy bank, and scanned using a SCANCO µCT-40 at a resolution of 30 microns. Cortical bone was removed from the resulting three-dimensional …

Design And Flight Testing Of A Warping Wing For Autonomous Flight Control, Edward Brady Doepke

Theses and Dissertations--Mechanical and Aerospace Engineering

Inflatable-wing Unmanned Aerial Vehicles (UAVs) have the ability to be packed in a fraction of their deployed volume. This makes them ideal for many deployable UAV designs, but inflatable wings can be flexible and don’t have conventional control surfaces. This thesis will investigate the use of wing warping as a means of autonomous control for inflatable wings. Due to complexities associated with manufacturing inflatable structures a new method of rapid prototyping deformable wings is used in place of inflatables to decrease cost and design-cycle time. A UAV testbed was developed and integrated with the warping wings and flown in a …

Low Reynolds Number Flow Field Modification Via Travelling Wave Actuation Of A Vertically Aligned Wire Array Surface, John C. Calhoun

Theses and Dissertations--Mechanical and Aerospace Engineering

Experiments were conducted to observe the effects of an active wire surface on low-Reynolds number Poiseuille flow. The objective was to evaluate the feasibility of actuating piezoelectric nanowires into a travelling wave motion in order to reduce wall shear stress in turbulent flows. Studies have shown that travelling wave motions introduced into the bounding wall of turbulent flow can reduce wall shear stress by disrupting the formation of drag-inducing coherent vortical structures. A Reynolds number scaled flow facility was designed to represent the near-wall region of turbulent flow. A wire surface was installed in the bounding wall and dynamically actuated …

Root Locus Techniques With Nonlinear Gain Parameterization, Brandon Wellman

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis presents rules that characterize the root locus for polynomials that are nonlinear in the root-locus parameter k. Classical root locus applies to polynomials that are affine in k. In contrast, this thesis considers polynomials that are quadratic or cubic in k. In particular, we focus on constructing the root locus for linear feedback control systems, where the closed-loop denominator polynomial is quadratic or cubic in k. First, we present quadratic root-locus rules for a controller class that yields a closed-loop denominator polynomial that is quadratic in k. Next, we develop cubic root-locus rules …

Aerodynamics And Control Of A Deployable Wing Uav For Autonomous Flight, Michael Thamann

Theses and Dissertations--Mechanical and Aerospace Engineering

UAV development and usage has increased dramatically in the last 15 years. In this time frame the potential has been realized for deployable UAVs to the extent that a new class of UAV was defined for these systems. Inflatable wing UAVs provide a unique solution for deployable UAVs because they are highly packable (some collapsing to 5-10% of their deployed volume) and have the potential for the incorporation of wing shaping. In this thesis, aerodynamic coefficients and aileron effectiveness were derived from the equations of motion of aircraft as necessary parameters for autonomous flight. A wind tunnel experiment was performed …

Viability Of A Controllable Chaotic Micromixer Through The Use Of Titanium-Nickel Shape Memory Alloy, David Ryan Lilly

Theses and Dissertations--Mechanical and Aerospace Engineering

Microfluidic devices have found applications in a number of areas, such as medical analysis, chemical synthesis, biological study, and drug delivery. Because of the small channel dimensions used in these systems, most microchannels exhibit laminar flow due to their low Reynold’s number, making mixing of fluids very challenging. Mixing at this size scale is diffusion-limited, so inducing chaotic flow patterns can increase the interface surface area between two fluids, thereby decreasing overall mixing time.

One method to create a chaotic flow within the channel is through the introduction of internal protrusions into the channel. In such an application protrusions that …