Mechanical Engineering Commons^™

Effect Of Alignment, Sizing, And Manufacturing Method On Mechanical Properties Of Recycled Carbon Fiber Composites, Nekoda Van De Werken

Mechanical Engineering ETDs

The exceptional combination of properties offered by carbon fiber composites has propelled their incorporation into high performance markets such as aerospace, wind energy, luxury cars and sporting goods. While the use of carbon fiber in these sectors is expected to continue to increase, the high price and energy cost associated with carbon fiber production acts as a significant barrier of entry into larger volume markets, such as the automotive industry. One method of navigating this transition is through the use of recycled carbon fiber composites.

Carbon fiber reclamation can produce fibers with up to 90% and 100% of the strength …

Tensile Experimentation Of Structural Aluminum Studying Void Growth, Scott Gampert

Mechanical Engineering ETDs

Uni-axial tensile tests were conducted on multiple dog-bone shaped poly-crystalline Aluminum specimens. The goal for this study was to understand the effects of voiding in structural aluminum and how voids grow under tension. The voids were represented by simply drilling and reaming one or more holes in varying patterns in the center of the sample. The testing clearly showed that the different hole patterns affect the area growth of voids. It also compares the developmental growth of a plasticity zone around samples with one hole to a previous study done with a different specimen shape(Ray,2003). In order to look at …

Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi

Mechanical Engineering ETDs

Clean (and specifically renewable) energy is steadily improving its global share. However, finite availability of fossil fuels and the growing effects of climate change make it an urgent priority to convince the industry and governments to incentivize investment in the renewable energy field and to make it more attractive by decreasing the capital cost. Until recently, uncertainties in funding limited renewable energy development, especially in the US. That limitation has been one of the barriers to progress. Another limitation of many renewable energy systems is the variability in their output, which makes them unsuitable for baseline power production. Therefore, fossil …

A Thermodynamic Study Of Binary Real Gas Mixtures Undergoing Normal Shocks, Josiah M. Bigelow

Mechanical Engineering ETDs

We investigate the difference between Amagat and Dalton mixing laws for gaseous equations of state (EOS) using planar traveling shocks. Numerical modeling was performed in the Sandia National Laboratories hydrocode CTH utilizing tabular EOS in the SESAME format. Numerical results were compared to experimental work from the University of New Mexico Shock Tube Laboratory. Latin hypercube samples were used to assess model sensitivities to Amagat and Dalton EOS. We find that the Amagat mixing law agrees best with the experimental results and that significant difference exist between the predictions of the Amagat and Dalton mixing methods.

Characterizing The Viscoelastic Behavior Of Pdms/Pdps Copolymers, Mark E. Small

Mechanical Engineering ETDs

Viscoelasticity is the property of materials that exhibits both viscous and elastic characteristics when undergoing deformation. In polymeric materials, the mechani- cal behavior is dominated by this viscoelastic phenomenon. Creating computational models for these materials can be quite complicated due to their frequency depen- dent and temperature dependent material properties. The research presented in this paper will use state of the art methods to fully develop a material model for a filled polydimethylsiloxane-polydiphenynlsiloxane (PDMS/PDPS) copolymer foam that has yet to be characterized. Mechanical properties of PDMS/PDPS copoly- mers are currently being studied to assess engineering performance, and to provide accurate …

Evaluation Of Concrete Constitutive Models For Impact Simulations, Guillermo A. Mata

Mechanical Engineering ETDs

The research documented in this thesis deals with computational analysis of reinforced concrete impacted by both hollow and solid missiles as a continuing effort on the work conducted by the Committee on the Safety of Nuclear Installations (CSNI) and Nuclear Energy Agency (NEA). The analysis focuses on comparing two similar material models and their ability to capture the mechanistic response of a reinforced concrete slab subjected to impact loads. The analysis was performed using the Sandia National Laboratories computing software SIERRA Solid Mechanics to run the finite element model. The two constitutive models studied were the Holmquist-Johnson-Cook and Johnson-Holmquist 2 …

An Experimental And Numerical Study Of Nanomechanical Behavior Of Hard/Soft Multilayered Coatings, Benigno Sandoval

Mechanical Engineering ETDs

Multilayer thin film composites, sometimes referred to as nanolaminates, have emerged as an important subset of materials with novel, and often tunable, properties such as high strength, high toughness, and resistance to wear or corrosion. Often fabricated using alternating layers of two or more materials, these multilayer thin film coatings are typically expensive and time intensive to fabricate and characterize and exhibit novel responses to nanomechanical testing such as plasticity during unloading. This thesis explores the nanoindentation response of hard/soft multilayer coatings through examination of the optical coating Al/SiC and similar coating Al/SiO2. Instrumented indentation was used to study single …

Analytic Solutions For The Crack-Tip Plastic Zone Under Mixed Mode Loading Conditions, Jason Ivey

Mechanical Engineering ETDs

Analytic solutions for the plastic region surrounding a crack tip are derived under mixed mode I/II and mixed mode I/II/III loading conditions for an elastic-plastic solid with a semi-infinite crack. Both the Von Mises and Tresca yield criteria are applied. Additionally, plane stress and plane strain assumptions are included when applicable. The results show a strong dependence on the ratio of the stress intensity factors for each loading mode. It is shown that the plastic zone area given by the Tresca yield criterion is larger than that given by the Von Mises yield criterion. Lastly, it is investigated whether or …

Characterization Of A Small Electro-Mechanical Contact Using Non-Conventional Measurement Techniques, Kelsey M. Johnson

Mechanical Engineering ETDs

Currently there are limitations in computing chatter behavior of small electrical contacts embedded in components using finite element models. Reduced order models (ROM) have been developed of such electrical contact sub-assemblies to assess the chatter behavior of the contacts during vibration and shock environments. The current ROM method requires experimental validation. This ROM also neglects the damping effects of the viscous fluid that typically surrounds such sub-assemblies. Dynamic ring-down testing of the electrical contacts in air was performed and will provide a validation data set for the current ROM. Additionally, dynamic ring-down testing of the electrical contact was performed in …

The Mathematical Theory Of Deformation Arrest In Large-Strain Dynamic Plasticity, Brendan A. Kullback

Mechanical Engineering ETDs

Ductile structural components subjected to explosive loadings exhibit a large range of behaviors. The response of beams, walls, and blast doors is estimated using two methods. The engineering level approaches are highly simplified and neglect much of the relevant physics while the use of finite element or shock-code simulation is expensive and not suited to rapid problem solving and parameter studies. In this dissertation, a medium fidelity reduced order modeling approach has been derived to capture the most relevant physics governing rupture of ductile bodies dynamically deforming in tension.

Solution of the inertially stretching jet is used to reveal the …

High-Throughput Tensile Testing Reveals Stochastic Properties In Additively Manufactured Steel, Bradley C. Salzbrenner

Mechanical Engineering ETDs

An adage within the Additive Manufacturing (AM) community is that “complexity is free”. Complicated geometric features that normally drive manufacturing cost and limit design options are not typically problematic in AM. While geometric complexity is usually viewed from the perspective of part design, this advantage of AM also opens up new options in rapid, efficient material property evaluation and qualification. This Thesis demonstrates how 100’s of miniature tensile bars can be produced and tested for comparable cost and in comparable time to a few conventional tensile bars. With this technique, it is possible to evaluate the stochastic nature of mechanical …

Simulation And Analysis Of A Drilling Fluid Using A Herschel-Bulkley Model, Daniel Powell

Mechanical Engineering ETDs

In the study, a drilling fluid with known properties is analyzed and simulated in the laminar regime through a pipe with dimensions of 1.5m in length and 0.02m in diameter. The purpose of the conducted analysis is to demonstrate the advantages of the Herschel-Bulkley model currently used in the oil and gas industry for analyzing non-Newtonian drilling fluids.

For comparison, the analysis is also performed using more simple models for non-Newtonian fluids such as the Bingham Plastic model and the Power Law model and for a Newtonian fluid (water). In addition to analytical models, computations are conducted using …

Drag And Shape Analysis Of Fiberglass Particles, Cody Williams

Mechanical Engineering ETDs

Settling tests were performed on particles of NUKON fiberglass to relate the drag coefficient of the particles to the Reynolds number of the particles. A new method was developed to measure fiberglass particles. The projected area, projected perimeter, and average height of the particles are measured using this method. The measurements are used to calculate the measured drag coefficient and measured Reynolds number for the particles. Data collected was compared to previous studies that focused on the settling of sand grains. A predictive correlation that was developed for sand grains was applied towards the particles of fiberglass. Tests were run …

A Visual Velocity Impedance Controller, Victor Nevarez

Mechanical Engineering ETDs

Successful object insertion systems allow the object to translate and rotate to accommodate contact forces. Compliant controllers are used in robotics to provide this accommodation. The impedance compliant controller is one of the more researched and well known compliant controllers used for assembly. The velocity filtered visual impedance controller is introduced as a compliant controller to improve upon the impedance controller. The velocity filtered impedance controller introduces a filter of the velocity impedance and a gain from the stiffness. The velocity impedance controller was found to be more stable over larger ranges of stiffness values than the position based impedance …

Mesh Addition Based On The Depth Image (Mabdi), Lucas E. Chavez

Mechanical Engineering ETDs

Many robotic applications utilize a detailed map of the world and the algorithm used to produce such a map must take into consideration real-world constraints such as computational and memory costs. Traditional mesh-based environmental mapping algorithms receive data from the sensor, create a mesh surface from the data, and then append the surface to a growing global mesh. These algorithms do not provide a computationally efficient mechanism for reducing redundancies in the global mesh. MABDI is able to leverage the knowledge contained in the global mesh to find the difference between what we expect our sensor to see and what …

Non-Destructive Evaluation Of Functional Material Properties Performed On Additively Manufactured Coupons, Devin S. Plagge

Mechanical Engineering ETDs

This thesis presents the development of non-destructive characterization of functional material properties of additively manufactured metals. In particular, this study was focused on the common structural stainless steel alloy, 316L, utilizing a coupon designed specifically for simple modal analysis. Additive manufacturing (AM) has moved to the forefront of the manufacturing world, particularly in aerospace and defense segments because of the potential to produce multi-functional, highly optimized components. The ability to confidently qualify these complex, and thus expensive, components has been lagging behind the advancing technology. The adoption of traditional characterization techniques developed for wrought materials has been most common, and …

Development And Implementation Of High Fidelity Human Models For The Investigation Of Blast And Non-Penetrating Projectile Impact, Candice F. Cooper

Mechanical Engineering ETDs

Military operations abroad have highlighted the effects of several types of physical traumas including traumatic brain injury and behind armor blunt trauma. While previous approaches toward understanding and mitigating trauma caused by blast or blunt impact relied upon physical testing of animal subjects, post mortem human subjects, or human tissue surrogates, recent advances in computational capability have spurred a growing area of research in computational investigations into wound injury and its mitigation. The development of high-fidelity human torso and head-neck-torso models are presented here. These models are employed in blast and non-penetrating projectile impact simulations in order to demonstrate the …

Theory, Fabrication, And Experimentation Of Phononic Crystals In Mems At Micro/Nano Scale: Engineering Of Thermal And Rf Phonons To Applications In Thermoelectrics And Microresonators, Seyedhamidreza Alaie

Mechanical Engineering ETDs

Phononic Crystals (PnCs) are novel materials comprised of a periodic structure of inclusions in a matrix. This periodic arrangement creates phononic bandgaps, and modifies phononic bandstructures of a material. Such a property offers promising applications at the micro and nano scales to engineer acoustic filters, high Q-factor resonators, and thermoelectric properties of materials. Studying PnCs at the micro/nano scale requires specific characterization techniques, which rely on Micro Electro Mechanical Structures (MEMS). This work focuses on the study, and characterization of PnCs using MEMS in view of their prospective applications in thermoelectric materials, microresonators and acoustic filters, and also the prospective …

A Biomechanical Comparison Of Locking Plates Contrasted With Intramedullary Treatment Of Distal Femur Fracture, Christina Salas

Mechanical Engineering ETDs

This study compares the pattern of failure of locking compression plates (LCP) and intramedullary nails (IM) used in treatment of unstable comminuted distal femur fractures in osteoporotic and normal bones. Possible late failure of the fixation represents a critical problem in the treatment of distal femur fractures. Few biomechanical studies have examined the effects of osteoporosis on stability of the bone after fixation. Some reports have described catastrophic failure of fixation when LCP were used compared with IM nails making salvage procedures difficult. This thesis reports on the behavior of synthetic composite bone and embalmed cadaveric bone with and without …

Proper Orthogonal Decomposition Of Hartmann Wavefront Sensor Data For A Plane Mixing Layer, Peter J. Szyjka

Mechanical Engineering ETDs

The ''snapshot" proper orthogonal decomposition (POD) was used to analyze the turbulent characteristics of a plane mixing layer. A two-dimensional (2-D) Hartmann wavefront sensor measured optical tilt propagation through a flow field downstream of a splitter plate. The velocity difference across the splitter plate produced roller vortices via the Kelvin-Helmholtz instability. Refractive-index fluctuations were produced by slightly heating the flow on the low-speed side of the splitter plate. The Hartmann sensor detects gradients in refractive index (and thus temperature) in directions perpendicular to its direction of propagation. The measured field of two-dimensional tilt (or optical deflection) is proportional to the …

Investigation Of The Excessive Bending Stiffness Of The Four Node Plane Stress/Plane Strain Quadrilateral Finite Element, William Lee Hacker

Mechanical Engineering ETDs

An eigenvalue-eigenvector approach is taken to study the details of the causes of and remedies for the overly stiff behavior exhibited by this element. The exact functional variation of the eigenpairs with element aspect ratio and material properties are derived for rectangular elements. These analytic expressions for the eigenpairs have not previously appeared in the literature. It is then shown that only the eigenvalues of the two flexure modes are decreased by the lower integration rules that are often applied, thereby causing a more flexible response. Knowing the variation in the eigenvalues with the various integrations then allows the element …

A Finite Element For The Three-Dimensional Deformation Of A Circular Ring Of Arbitrary Cross Section, Jeffrey Stuart Knowlton

Mechanical Engineering ETDs

A two-node finite element for relatively compact, solid curved beams is derived. A node is located at the centroid of each end of the beam, and each node has six degrees of freedom, consisting of three translations and three rotations in mutually perpendicular directions. The element stiffness matrix has dimensions 12x12. A cylindrical polar coordinate system is used to express the components of the associated displacement and load vectors. As a consequence of the assumption of a nonzero cross-section product of inertia, deflec­tions in the plane and out of the plane of beam curvature are coupled. Hence in-plane loads can …

Use Of Thermal Storage For Load Management In A Solar-Augmented Heat Pump System, James Thomas Schmitz

Mechanical Engineering ETDs

Electric utilities are today faced with the dilemma of satisfying increasing demands for electrical energy while their ability to build new power plants is being severely curtailed primarily due to environmental concerns. By redistributing the power demand of individual customers (and thus the utility) with respect to time, greater overall electricity consumption can be met without increasing the generating capacity of the utility. This redistribution can be accomplished using thermal energy storage at the customer’s location. For heating and cooling of buildings, thermal storage, combined with off-peak period operation of the mechanical system's major electricity consuming equipment, can lower peak …

The Compatibility Of Mild Carbon Steel And Water In A Heat Pipe Application, David D. Kenney

Mechanical Engineering ETDs

The phenomena that govern the performance and affect the lifetime of heat pipes are reviewed. The phenomena include the corrosion of metals by aqueous solutions, the diffusion of gases through metals, and the effects of hydrogen on metals. Heat pipes of 1015 C.D. carbon steel were fabricated and operated with a control group of 304 stainless steel heat pipes over the temperature range from 140° to 300° C. Results indicate that carbon steel/water heat pipes perform as well or better than 304 stainless steel/water heat pipes over the temperature range covered in this test.

Lee's Moment Method Applied To Binary Flow In Jet And Channel Devices Used For The Aerodynamic Separation Of Uranium Isotopes, Edward Eugene Holcomb

Mechanical Engineering ETDs

Lees' moment method is applied to the problem of compressible, binary flow of uranium hexafluoride gas through a parallel plate chan­nel. The time-dependent numerical problem is solved to yield the steady state solution. The results obtained are preliminary to the solution of the flow field for the curved nozzle and colliding jet devices used in the aerodynamic separation of uranium isotopes. Lees' concept of two-sidedness of the distribution function doubles the number of variables required to describe the system, and the resulting set of moment equations is not easily solved. The assumptions of isothermal, hydrodynamically fully developed flow are made …

A Survey Of Structural Identification Techniques, Doris Evelyn Miller

Mechanical Engineering ETDs

This work is a collection and survey of system identification methods in the open literature. The motivation for the work was to find suitable methods of system identification for use in structural diagnosis. Methods surveyed include those which identify the system in terms of modal parameters, and those which identify the system either nonparametrically or in terms of arbitrary parameters. Both deterministic and stochastic methods are reviewed. Particular emphasis is placed on determining damping coefficients, and on a formulation known as modal synthesis. It is concluded that stochastic methods are better suited to the problem of structural diagnosis, and that …

Complete Elastic-Plastic Solution Around A Tensile Crack In Strain-Hardening Materials, Clancy Hatleberg

Mechanical Engineering ETDs

A complete elastic-plastic solution for both small and large scale yielding is found for the total stress field surrounding a tensile crack in an infinite sheet of strain-hardening materials under conditions of plane stress. The solution is based on the deformation theory of plasticity in conjunction with strain-hardening stress-strain relations, and is found by using the minimum of a modified complimentary energy principle coupled with a modified Ritz method. Numerical results are obtained for two approximate constitutive laws; a Ramberg-Osgood stress-strain relation and a modified Ramberg-Osgood stress-strain relation. Results indicate that the total stresses are discontinuous as the crack tip …

Surface Roughness Effects In Hydrodynamic Lubrication, Johnny Lynn Teale

Mechanical Engineering ETDs

Prediction of pressure and leakage in a hydrodynamic bearing when surface roughness effects are important is an essential step in bearing design. The inclusion of surface roughness effects in bearing analysis allows more accurate prediction of bearing life. It has been shown that the average flow model developed by Cheng and Patir is a promising technique for determining surface roughness effects. The objective of this investigation is to examine the validity, applicability and limitation of the average flow model. Validity of the average flow model is ascertained by checking the independence of flow factors. Discussion of the general Reynolds equation …

Geothermal Energy: Heat Extraction From Hot-Dry-Rock Masses In The Presence Of Secondary Thermal Cracks, Yaw-Min Lu

Mechanical Engineering ETDs

Additional heat extraction from geothermal energy reservoirs depends on the feasibility to extend the main, hydraulic fracture through secondary thermal cracks of the adjacent hot rock. When the main, hydraulic fracture is cooled sufficiently, these secon­dary thermal cracks are produced normal to the main fracture surface, As such, both the heat transfer surface area and heat energy available to the fluid circulating through the main, hydraulic fracture system increase.

A Design Study For A Wavy Hydrodynamic Mechanical Face Seal, Raymond Edward Pierce

Mechanical Engineering ETDs

A desirable objective of mechanical face seal design is to achieve the maximum hydrodynamic load support possible while main­taining an acceptable leakage. In this way, mechanical face seal life can be greatly extended as the wear of the seal faces is significantly reduced. It has been shown that circumferentially varying waviness of one of the faces of a mechanical face seal causes such hydrodynamic lubrication.

The objective of this investigation is to examine the performance characteristics of the wavy mechanical face seal by studying the effects of certain design parameters. Seal performance is measured by leakage and wear rate. The …