Materials Science and Engineering Commons^™

The Effects Of A Collaborative Problem-Based Learning Experience On Students’ Motivation In Engineering Capstone Courses, Brett D. Jones, Cory M. Epler, Parastou Mokri, Lauren H. Bryant, Marie C. Paretti

Interdisciplinary Journal of Problem-based Learning

We identified and examined how the instructional elements of problem-based learning capstone engineering courses affected students’ motivation to engage in the courses. We employed a two-phase, sequential, explanatory, mixed methods research design. For the quantitative phase, 47 undergraduate students at a large public university completed a questionnaire that measured the components of the MUSIC Model of Academic Motivation (Jones, 2009): empowerment, usefulness, success, situational interest, individual interest, academic caring, and personal caring. For the qualitative phase that followed, 10 students answered questions related to the MUSIC components. We identified several instructional elements that led to motivating opportunities that affected students ...

A Three-Dimensional Quantitative Understanding Of Short Fatigue Crack Growth In High Strength Aluminum Alloys, Wei Wen

Theses and Dissertations--Chemical and Materials Engineering

The behaviors of short fatigue crack (SFC) propagation through grain boundaries (GBs) were monitored during high cycle fatigue in an Al-Li alloy AA8090. The growth behaviors of SFCs were found to be mainly controlled by the twist components (α) of crack plane deflection across each of up to first 20 GBs along the crack path. The crack plane twist at the GB can result in a resistance against SFC growth; therefore SFC propagation preferred to follow a path with minimum α at each GB. In addition to the grain orientation, the tilting of GB could also affect α.

An experiment ...

Feasibility Study For Detection And Quantification Of Corrosion In Bridge Barrier Rails, Lisa H. Brasche

Tech Transfer Summaries

Three non-destructive technologies were evaluated for their abilities to detect and quantify corrosion damage in reinforcing steel used in bridge barrier rails.

Feasibility Study For Detection And Quantification Of Corrosion In Bridge Barrier Rails, Terrance C. Jensen, Scott E. Wendt, Joseph N. Gray, Chester C.H. Lo, Frank J. Margetan, David J. Eisenmann, Norio Nakagawa, Lisa H. Brasche

Center for Nondestructive Evaluation Project Reports

Technical challenges exist with infrastructure that can be addressed by nondestructive evaluation (NDE) methods, such as detecting corrosion damage to reinforcing steel that anchor concrete bridge railings to bridge road decks. Moisture and chloride ions reach the anchors along the cold joint between the rails and deck, causing corrosion that weakens the anchors and ultimately the barriers.

The Center for Nondestructive Evaluation at Iowa State University has experience in development of measurement techniques and new sensors using a variety of interrogating energies. This research evaluated feasibility of three technologies—x-ray radiation, ground-penetrating radar (GPR), and magnetic flux leakage (MFL)—for ...

High-Stress Shear-Induced Crystallization In Isotactic Polypropylene And Propylene/Ethylene Random Copolymers, Zhe Ma, Lucia Fernandez-Ballester, Dario Cavallo, Tim Gough, Gerrit W. M. Peters

Mechanical & Materials Engineering Faculty Publications

Crystallization of an isotactic polypropylene (iPP) homopolymer and two propylene/ethylene random copolymers (RACO), induced by high-stress shear, was studied using in situ synchrotron wide-angle X-ray diffraction (WAXD) at 137 °C. The “depth sectioning” method (Fernandez-Ballester, Journal of Rheology 53:5 (2009), pp. 1229−1254) was applied in order to isolate the contributions of different layers in the stress gradient direction and to relate specific structural evolution to the corresponding local stress. This approach gives quantitative results in terms of the specific length of fibrillar nuclei as a function of the applied stress. As expected, crystallization becomes faster with increasing ...

Compositional Tuning Of Structural Stability Of Lithiated Cubic Titania Via A Vacancy-Filling Mechanism Under High Pressure, Hui Xiong

Materials Science and Engineering Faculty Publications and Presentations

Experimental and theoretical studies on the compositional dependence of stability and compressibility in lithiated cubic titania are presented. The crystalline-to-amorphous phase transition pressure increases monotonically with Li concentration (from ∼17.5  GPa for delithiated to no phase transition for fully lithiated cubic titania up to 60 GPa). The associated enhancement in structural stability is postulated to arise from a vacancy filling mechanism in which an applied pressure drives interstitial Li ions to vacancy sites in the oxide interior. The results are of significance for understanding mechanisms of structural response of metal oxide electrode materials at high pressures as well as ...

Process-Structure Relationships Of Magnesium Alloys, Arindam Banerjee

University of Western Ontario - Electronic Thesis and Dissertation Repository

This research study characterizes the effects of solidification conditions on the resulting microstructure of an AM60B magnesium alloy during the solidification cycle of the casting. Seventeen control points are chosen from different sections of an instrument panel beam casting and its centerline coordinates are located. These control points locations are then used by Meridian Lightweight Technology Inc. to run a simulation in a MAGMASoft casting software to obtain temperature-time specific data.

An exact analytical solution to the Stefan problem is used to compute the one dimensional heat transfer for a section of the casting and to calculate its temperature distribution ...

Pore-Size Dependence Of Ion Diffusivity In Dye-Sensitized Solar Cells, Yiqun Ma

Open Access Dissertations and Theses

The pore-size dependence of liquid diffusivity in mesopores has been a controversial topic. It is especially meaningful in dye-sensitized solar cells (DSSCs) because the triiodide ion diffusivity is closely related to the cell performance. By applying electrochemical measurements, the pore-size dependence of ion diffusivity in DSSCs was investigated based on TiO₂ thin films of variable pore diameters. The alternation of pore-size was achieved by the epitaxial growth of TiO₂ after TiCl₄ post-treatments. From the trend of normalized diffusivities, the respective valid regimes of pore-size dependent and independent diffusion were determined, which were separated by the transition point ...

Sol-Gel Derived Biodegradable And Bioactive Organic-Inorganic Hybrid Biomaterials For Bone Tissue Engineering, Bedilu A. Allo

University of Western Ontario - Electronic Thesis and Dissertation Repository

Treatments of bone injuries and defects have been largely centered on replacing the lost bone with tissues of allogeneic or xenogeneic sources as well as synthetic bone substitutes, which in all lead to limited degree of structural and functional recovery. As a result, tissue engineering has emerged as a viable technology to regenerate the structures and therefore recover the functions of bone tissue rather than replacement alone. Hence, the current strategies of bone tissue engineering and regeneration rely on bioactive scaffolds to mimic the natural extracellular matrix (ECM) as templates onto which cells attach, multiply, migrate and function.

In this ...

Durability Of Repair Techniques Of Fine Cracks In Concrete, Anna-Krystyna Rzezniczak

Open Access Dissertations and Theses

Aging public infrastructure in North America continues to challenge engineers and scientists to develop repair and rehabilitation strategies that are practical, durable and cost effective. Of specific interest is the state of concrete and concrete repair in buildings and civil engineering infrastructures that are in deteriorating condition. In particular, cracks pose a threat to the durability and ultimately the structural integrity of concrete. Cracks in concrete may form for several reasons, e.g. plastic shrinkage, thermal contraction, mechanical loading or as a result of overloading. Once formed, cracks present a combination of problems to the service life and performance of ...

On The Crystallography Of Bainitic Transformation In Steels, Raheleh Hadian

Open Access Dissertations and Theses

Bainite is a low temperature transformation product of austenite decomposition in steels. Its unique range of microstructures offers promising combinations of strength with ductility. At low transformation temperatures the crystallography of a phase transformation often plays an important role in the overall microstructure and how it develops. Therefore in this study the structures of ferrite/cementite and ferrite/austenite interfaces in bainite were investigated from a crystallographic viewpoint. After describing these interfaces, the idea of interphase boundary nucleation of cementite on a ferrite/austenite interface was investigated.

An O-line model (a special case of the O-Lattice) was used to explain ...

Complex Rare-Earth Antimonide Suboxides For Thermoelectric Applications, Peng Li Wang

Open Access Dissertations and Theses

Thermoelectric (TE) materials are able to convert heat directly into electricity and vice versa. This special property makes them valuable for a variety of applications involving power generation and refrigeration. In the search for potential high-performance TE materials, a number of rare-earth (RE) antimonide suboxide phases have been investigated.This presentation will focus on two classes of rare-earth antimonide suboxides: the RE₃Sb₃O₃ and RE₈Sb_3-dO₈ phases (C2/m space group) based on the RE–O frameworks and the anti-ThCr₂Si₂ type RE₂SbO₂ compounds ...

Fatigue Behavior Of High-Entropy Alloys, Michael Alexander Hemphill

Masters Theses

Research was performed on the Al₉Co_18.2Cr_18.2Cu_18.2Fe_18.2Ni_18.2 [subscripts atomic percent] and Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ high-entropy alloys (HEAs) in an attempt to study their fatigue behavior. The present investigation shows encouraging fatigue-resistance characteristics due to their high fatigue lives of various samples at relatively high stresses. The current results indicate that the fatigue behavior of HEAs compares favorably to many conventional alloys, such as steels, titanium alloys, and advanced bulk metallic glasses with a fatigue-endurance limit of ...

Lignin Yield Maximization Of Lignocellulosic Biomass By Taguchi Robust Product Design Using Organosolv Fractionation, Anton Friedrich Astner

Masters Theses

Lignin, a byproduct of the organosolv pretreatment process using lignocellulosic biomass from switchgrass (Panicum virgatum) and tulip poplar (Liriodendron tulipifera) is currently being explored for its potential use in the production of value-added chemicals and biobased polymers. Pretreatment is one of the most expensive processing steps in cellulosic biomass conversion. Optimization of the process is one of the major goals of the biomass-toethanol conversion process. Taguchi Robust Product Design (TRPD) provides an effective engineering experimental design method for optimizing a system and designing products that are robust to process variations. Given the results of several preliminary studies of the organosolv ...

Understanding Size Effects In Small Scale Deformation: A Statistical Perspective, Sudharshan Phani Pardhasaradhi

Doctoral Dissertations

Recent experimental observations of micro-compression / tension tests indicate that as the size of test specimen decreases the yield strength increases. This raises a fundamental question: Why is smaller stronger? Is there a fundamental relationship between the size of a specimen and its intrinsic strength? This simple question pushes the limit of the current understanding of the physical mechanisms underlying material deformation, especially at small scales. In order to explain the experimental observations of the strength of small specimens containing a limited number of dislocations, a simple statistical model is developed. Two different types of randomness are introduced, viz., randomness in ...

Structure And Dynamics Of High Temperature Superconductors, Jennifer Lynn Niedziela

Doctoral Dissertations

High temperature superconductivity in iron based compounds has presented a series of complex problems to condensed matter physics since being discovered in 2008. The stalwart basis of condensed matter physics is the “strength in numbers" aspect of crystalline periodicity. Perfect crystalline periodicity has made possible the reduction of the questions of structural and electronic properties to single dimensions, increasing the tractability of these problems. Nevertheless, modern complex materials stretch these assumptions to their limits, and it is at this point where our work starts. Using neutron and x-ray scattering, we have conducted a series of studies on the structural disorder ...

An Examination Of The Potential Of Building Information Modelling To Increase The Efficiency Of Irish Contractors On Design And Build Projects, Charles Anthony Mitchell, Myles Keaveney

Conference papers

Competition between Irish contractors is more aggressive than ever before. In the current economic climate an ability to construct with greater efficiency could ensure a company’s survival. The purpose of this research was to determine the extent to which efficiency benefits could be realised by contractors on design and build projects as a result of implementing a revolutionary process referred to as Building Information Modelling (BIM). After a critical analysis on all aspects of BIM in the literature review, questionnaires were sent to establish the success of this system in the US and also in the comparatively few Irish ...

P3ht:Pcpdtbt:Pcbm Multi- Polymer Single Layer Solar Cells, Ted Andreas

Physics

OPV efficiencies are limited by their narrow absorption; rather than using tandem architecture to overcome this obstacle, our group combined P3HT and PCPDTBT into a single layer BHJ solar cell that achieved 2.0% PCE. This is 33% higher than the pure P3HT control from this group, proving that multi-polymer solar cells have the potential to outperform their single-polymer components.

Mehanical Characterization Of Ion-Iradiated Silicon Carbide By Nanoindentation, Alex Hackett, Kurt Johanns, Haizhou Xue, Yanwen Zhang, Erik Herbert, George Pharr

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Tests are done on various types of silicon carbide in order to analyze mechanical properties and radiation resistance.

Helical Ordering In Chiral Block Copolymers, Wei Zhao

Open Access Dissertations

The phase behavior of chiral block copolymers (BCPs*), namely, BCPs with at least one of the constituent block is formed by chiral monomers, is studied both experimentally and theoretically. Specifically, the formation of a unique morphology with helical sense, the H* phase, where the chiral block forms nanohelices hexagonally embedded in the matrix of achiral block, is investigated. Such unique morphology was first observed in the cast film of polystyrene-b-poly(L-lactide) (PS-b-PLLA) from a neutral solvent dichloromethane at room temperature with all the nanohelices being left-handed, which would switch to right-handed if the PLLA block changes ...