Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Fabrication and assessment of anode supported SOFCS doped with aluminum titanate via electrochemical and non-destructive micro-indentation testing(Montana State University - Bozeman, College of Engineering, 2019) Kent, John Parker; Chairperson, Graduate Committee: Stephen W. SofieCeramic-metal (cermet) composites are the most promising electrochemical anodes for commercial implementation in solid oxide fuel cells (SOFC). Recent advances at MSU in cermet formulations utilizing aluminum titanate (ALT) dopants in nickel oxide (NiO)-yttria stabilized zirconia (YSZ) anodes has shown substantial performance gains in degradation rates as well as mechanical behavior when evaluated in low power density electrolyte supported cell (ESC) geometries and bulk anode forms through modulus of rupture and equibiaxial flexure. The benefits associated with ALT are due to the formation of secondary phases of nickel aluminate and zirconium titanate in NiO-YSZ cermets that form during processing. Cermet modulus of rupture studies are rigorous, can span multiple months, and requiring hundreds of samples when studying the effects of both thermal and redox cycling on SOFC anodes to achieve statistically significant results. The use of non-destructive methods such as micro-indentation to examine the strength and toughness of doped and differently processed cermet anodes can rapidly speed up the analysis of mechanical properties including the mechanical support characteristics of higher power density anode supported cell (ASC) geometries targeted by industrial SOFC developers. The aim of this study was to examine non-destructive micro-indentation testing in evaluating cermet anode materials in both oxidized and reduced state in direct contrast with traditional destructive methods. Extending the current state of ALT anode doping by utilizing these rapid assessment methods, this work examines mechanical properties degradation and fracture toughness under multiple thermal and redox cycles. Additionally, this work details the framework for cell fabrication methods that were developed to process ASCs with state of the art 5 micrometer electrolytes for the first evaluation of ALT doping of SOFCs in this high power cell configuration.Item Influence of fabric architecture on damage progression as evidenced by acoustic emission(Montana State University - Bozeman, College of Engineering, 2016) Lolatte, Austin James; Chairperson, Graduate Committee: David A. MillerFabric reinforced polymer matrix composites are integral structural materials used in wind turbine blades. Wind turbines are expected to increase in size and utilization as global focus turns toward power generation utilizing renewable sources. How these materials change properties due to damage accumulated are important to the future of wind energy. They feature damage mechanisms that are unique from any other engineering material. These factors are now driving innovation for design and manufacturing of the blades. This has led to investigation in characterizing the mechanical behavior of the composites. These composites were manufactured using unidirectional and biaxial fiber layups from three fabrics composed of an epoxy matrix and glass fibers. The effect of the architecture of the fibers on damage progression was determined with acoustic emission sensors that were attached linearly to capture elastic waves emitted by damage mechanisms inside the samples during testing. The critical data extracted from the elastic waveforms include the peak frequency and absolute energy released by the samples and how they are associated with the strength of the samples. A static loading scenario was determined to be the optimal testing method. The use of AE measurements proved to be an invaluable tool to determine how the damage progression of composite materials lead to failure for some, while not being accurate for others. Results found that simple architecture differences for the same fibers have drastic effects on damage progression. However, the energy measurements proved to be imperfect with current technology and application; improvement will be necessary for AE instruments to be a viable tool for energy measurement in the future. AE provides a unique analysis that can identify and characterize damage related to fabric composition. The frequency content provides a consistent method of identifying damage mechanisms between varying materials. Optimal architecture and layup can be determined with the help of AE. Correlating acoustic energy to actual energy dissipated still has potential as a valuable tool if improvement in sensor technology can be achieved. Ultimately, a foundation for correlating mechanical properties of the materials and damage progression to fabric architecture and layup using AE tools was created.Item Non-destructive assessment of household reverse osmosis water treatment membrane biofouiling(Montana State University - Bozeman, College of Engineering, 2015) Markwardt, Stephen Donald; Chairperson, Graduate Committee: Anne CamperReverse osmosis (RO) membrane treatment is well known for its ability to desalinate sea and brackish waters on a massive scale in large treatment plants. Conversely, RO membranes are also used to treat freshwater from questionable sources at the point of use. Both types of systems suffer from the negative effects of membrane fouling. There are four basic types of fouling: inorganic, colloidal, organic, and biofouling. Traditional methods for assessing fouling either cannot differentiate between the fouling types or destroy the membrane in the process. Currently, many new and innovative methods to non-destructively assess the degree and type of fouling inside a membrane unit are being researched. Most of these methods require the use of expensive electrodes and equipment which is not economical for point of use systems. This research was aimed at determining economical non-destructive methods to assess biofouling in point of use RO membrane treatment systems. Experimentation was performed on three parallel household RO membrane units operated under controlled feed water conditions to promote biofouling, inorganic fouling and a combination of both. Operational and biological parameters were monitored throughout the systems' lifespan. Membrane autopsies were also done to assess the degree and type of fouling. Statistical models were performed on the operational data to determine statistically relevant parameters between the fouling types that were subsequently validated by the membrane autopsies. Several non-destructive methods to assess the presence of biofouling were determined. Permeate flow rates decreased in a significantly different way when biofouling was present compared to when it was not. Large increases in permeate conductivity were also noted in membranes suffering from biofouling while they were not observed in membranes that had been inorganically fouled. The concentration of cell clumps in the retentate also increased in membranes experiencing biofouling while they did not increase in membranes that were inorganically fouled. These methods were found to not be sensitive enough to provide early warning for the presence of biofouling. However, these methods could be used to conveniently and economically assess the types of fouling problems being experienced household RO systems.Item Nondestructive testing : a curriculum developed for industrial education(Montana State University - Bozeman, College of Education, Health & Human Development, 1976) Thomas, Merle CliffordItem A finite element approach to predicting vibrothermographic heat detections of fully embedded delaminations within composite plates(Montana State University - Bozeman, College of Engineering, 2013) Cook, Corey Joseph; Chairperson, Graduate Committee: Ahsan MianVibrothermography is a Nondestructive Evaluation (NDE) technique which is particularly well suited for locating discontinuities, such as cracks and sub-surface delaminations within composite structures. The Vibrothermographic method relies on high-amplitude vibrational excitations within a structure to cause frictional rubbing along flaw surfaces. Frictional heat energy dissipated between flaw surfaces diffuses through the material of the structure to a surface where heat signatures are monitored using infra-red thermographic camera technologies. Vibrothermographic testing methods, developed in the late 1970's with the advent of improved IR camera technologies, have been somewhat slow to develop, due in part to a lack of understanding of the physics surrounding damaged areas of structures. The focus of this research is on the use of Finite Element (FE) Analysis, using ANSYS® software, to simulate the Vibrothermographic method. One goal of the research is to produce algorithms predicting the likely-hood of thermal detection of numerous delamination flaws within a fiberglass/epoxy composite plate. The FE modeling attempts accurately characterize harmonic responses surrounding the "damaged" regions (flaw areas) of the plate. Harmonic response analyses are performed on the FE plate model, and nodal harmonic displacement data is subsequently utilized within transient analysis sub-modeling procedures. Each of the nine delamination flaws are analyzed within these sub-modeling procedures and the rates at which frictional heat energy dissipation, due rubbing, occur at the flaw faces are derived. Each delamination sub-model is subjected to a high-resolution frequency sweep analysis, where frequency dependent heat generation data is collected over a frequency bandwidth of 800-30000Hz. The latter portion of the paper discusses the use of a novel finite element approach to estimating the likely hood of thermal detections for the flaws. The approach uses generic finite element model to predict thermal detection times for an expansive set of flaw and testing parameters. A response surface method of curve-fitting is applied to the collected detection time data, and the resulting equation is subsequently used to predict the heat-signature detectability for each flaw. The results of this method are ultimately compared to empirical vibrothermographic frequency-sweep data, and a preliminary assessment of the viability of the approach is made.Item Parametric study of heat diffusion in vibrothermography using analytical and numerical methods(Montana State University - Bozeman, College of Engineering, 2012) Trundnowski, Anthony James; Chairperson, Graduate Committee: Ahsan MianThe development of precise and accurate non-destructive examination (NDE) techniques is an essential element in preventing failures and increasing reliability in engineering materials. In particular, few present day composite material NDE techniques give the desired precision and cost-effectiveness required for many high-reliability applications such as on airplane wings or wind turbine blades. This study contributes to the development of a NDE technique known as vibrothermography. Vibrothermography is performed by measuring frictional heating of internal flaws that occur as a result of inducing specimen vibrations via an ultrasonic transducer. This frictional heat conducts itself to the surface, where it can be detected by an infared camera. Vibrothermography is a potential cost-effective alternative to detecting a wide variety of flaws in composite materials. This study models the heat generation that occurs during a vibrothermography test; and it simulates the manner at which this heat would conduct to the specimen's surface. Once the models were developed, they were used to simulate the influence of the following potential test parameters: specimen thickness, flaw generation amount, flaw size, flaw depth, and flaw orientation. The results provide an initial insight of which of these parameters could most greatly influence a vibrothermography test, and which ones may or may not be able to be detectable from a vibrothermograhy test. Lastly, in conjunction with Kyle Spaulding, an initial thermal-mechanical combined analysis was developed that includes specimen vibration, heat generation, and heat conduction to create a start to finish vibrothermography simulation. This model is soon to be compared with experimental data. If the model results match experimental data, then the models will be implemented as a useful tool in determining the overall feasibility, accuracy, reliability, and optimal test procedures for vibrothermography.