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Briggs, Maxwell H.Improving Free-Piston Stirling Engine Power Density
Doctor of Philosophy, Case Western Reserve University, 2015, EMC - Mechanical Engineering
Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

Committee:

Joseph Prahl (Advisor)

Subjects:

Aerospace Engineering; Alternative Energy; Applied Mathematics; Conservation; Design; Electrical Engineering; Energy; Engineering; Mechanical Engineering; Mechanics; Naval Engineering; Nuclear Engineering; Technology

Keywords:

Stirling, Engine, Power Density, Energy, Free-Piston, Nodal Analysis, Isothermal Analysis, Analysis, Experimental Validation,

Young, Paul SModeling and Analysis for Atmospheric Galvanic Corrosion of Fasteners in Aluminum
Master of Science in Engineering, University of Akron, 2015, Chemical Engineering
Corrosion at fasteners in aluminum presents a high risk and challenge to corrosion mitigation strategies. The objective is to model atmospheric galvanic corrosion and determine the stages of damage evolution for 2024-T3 around fasteners. The synthesis of three test methods, exposure testing, laboratory measurements, and software modeling, are used to increase understanding of corrosion modes and damage evolution in order to help mitigate risk for atmospheric galvanic corrosion from fasteners in aluminum. An exposure study in Daytona Beach, Florida consisted of coupling aluminum coupons to metal fasteners for 24 months. Fastener metals used are 316L stainless steel, cadmium-plated low carbon 1018 steel, and cadmium-plated fasteners with Cd partially removed to simulate damaged plating. The corrosion damage modes at each stage are identified, and the impact of galvanic action is determined. A sequence of corrosion damage stages is developed and the transition through the stages is related to corrosion processes and their controlling factors. The results are related to corrosion mitigation for fasteners in Al. Galvanic corrosion is studied in the lab through Mixed Electrode Theory and through analytical modeling. Data quantifies the impact of galvanic action from fastener metal on the corrosion of aluminum. The models provide visual and quantitative data to identify galvanic couples of higher risk. Models predictions are at time zero and without the influence of damage evolution or changing environments. Laboratory testing allows for samples to be damaged so corrosion modes can be identified. The combination of modeling for quantifying the galvanic impact and damage evolution from lab tests allow for more effective corrosion mitigation methods to be employed. Models are becoming a valuable tool as user knowledge increases about the sensitivity of parameter inputs. Fasteners in aluminum, comparable to Daytona exposure tests, are used as examples for model applications. The effects of model inputs on the predictions of model outputs are analyzed for all inputs through quantified data. Models produce 3-D diagrams that highlight corrosion damage, making results easy to comprehend for non-subject experts and providing the ability to increase the effectiveness of material selection. Knowledge pertaining to atmospheric galvanic corrosion from fasteners in aluminum is increased. Laboratory tests and software models correlated very well due to the controlling input parameter (polarization curves) for software modeling being generated from laboratory data. Exposure tested aluminum coupons go through a series of corrosion stages that include pitting, intergranular corrosion and stress corrosion cracking. A synergistic effect is generated when the three test methods, exposure testing, lab testing, and software modeling, are used in combination.

Committee:

Joe Payer, Dr. (Advisor); Hongbo Cong, Dr. (Committee Member); Chelsea Monty, Dr. (Committee Member); Rajeev Kumar Gupta, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Chemical Engineering; Engineering; Materials Science; Metallurgy; Naval Engineering; Science Education

Keywords:

Atmospheric galvanic corrosion, intergranular corrosion, stress corrosion cracking, mixed electrode theory, modeling, exposure testing, wedging, aluminum, 2024-T3, finite elemental analysis, coulometric reduction, rust, aerospace alloys

Nelson, William ForresterAn Investigation into the Use of Mussel Adhesive Proteins as Temporary Corrosion Inhibitors for HY80 Steel
Master of Science (M.S.), University of Dayton, 2014, Chemical Engineering
Several proteins found in the adhesive system of the common blue mussel Mytilus edulis have chemical properties which might enable them to inhibit the flash rusting of steels. In this work, Mytilus edulis foot proteins (MeFPs) 1, 3, and 5 were purified and applied to HY80 steel in a number of buffer systems containing various amounts of borate, acetate, and phosphate at pH 5.5-7.0. Treated HY80 samples were then monitored in an exposure chamber at 40°C and 100% relative humidity for 7 days. The MeFP treatments were also evaluated electrochemically via electrochemical impedance spectroscopy (EIS). The effect of enzymatic crosslinking of the applied proteins using mushroom tyrosinase was also investigated. HY80 samples treated with MeFP-1 failed to inhibit corrosion when the protein was dissolved in deionized water, and the effect of MeFP-1 on the corrosion on HY80 in buffers containing acetate was not significantly different from the control samples. However, in 0.05M phosphate buffer solution at pH 5.5, crosslinked MeFP-3 and MeFP-5 were capable of significantly increasing the time to corrosion and significantly reducing the mass loss of HY80 in the exposure chamber compared to relevant buffer-only controls. The performance of crosslinked MeFP-5 was similar to a commercial temporary corrosion inhibitor applied at the same mass concentration as the protein, suggesting that MeFP-5 and similar proteins or polymers may be capable of inhibiting corrosion under certain conditions.

Committee:

Douglas Hansen (Advisor); P. Terrence Murray (Committee Member); Robert Wilkens (Committee Member)

Subjects:

Biochemistry; Engineering; Materials Science; Naval Engineering

Keywords:

flash rust; corrosion inhibitor; flash rust inhibitor; mussel protein; mussel adhesive protein; MAP; MeFP;

Thummalapalli, Vimal KumarBiomimetic Composite T-Joints
Master of Science (M.S.), University of Dayton, 2011, Materials Engineering

Composite structural joints, as observed throughout the natural world, have been systematically altered and proven via lengthy evolutionary processes. Biological fixed joints tend to exhibit unique attributes, including highly optimized fiber paths to minimize stress concentrations. In addition, since the joints consist of continuous, uncut fiber flow patterns, the joint does not inhibit the biological organism in the transportation of information, chemicals and food from one part of the body to the other. To the contrary, large sections of man-made composite material structures are often joined using bolted or bonded joints, which involve low strength and high stress concentrations. These methods are also expensive to achieve. Additional functions such as fluid transport, electrical signal delivery, and electrical and thermal conductivity across the joints typically require parasitic tubes, wires, and clips. By using the biomimetic methods, we seek to overcome the limitations which are present in the conventional methods. In the present work, biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber, epoxy resin, and structural foam. The joints were fabricated using the wet lay-up vacuum bag resin infusion method. Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared. The various joint designs were tested quasi-statically in bending of the T in a calibrated screw-driven load frame. Custom, purpose-designed fixtures were required to support the base of the joint during the bending load. The weight savings using the biomimetic approaches is discussed, as well as a comparison of failure modes versus fiber/core architectures is given.

In addition to developing structurally optimized, weight-efficient joints, a tremendous ancillary benefit to the approach is the ability to easily embed wires and micro tubes contiguous across the joined elements. This approach is key to achieving true robust structural multi-functionality.

Committee:

Steven Donaldson (Committee Chair); Thomas Whitney (Committee Member); Elias Toubia (Committee Chair)

Subjects:

Aerospace Engineering; Aerospace Materials; Automotive Engineering; Automotive Materials; Biology; Civil Engineering; Engineering; Materials Science; Mechanical Engineering; Mechanics; Naval Engineering; Plant Sciences; Polymers; Textile Research

Keywords:

Composites; Composite T-Joints; Sandwitch Structures; Biomimetics; Bionic