Master of Science in Engineering, University of Akron, 2021, Mechanical Engineering

The viscoelastic properties of rubber have allowed compounds to be utilized across many different industries. Rubber is a very unique material, and the chosen manufacturing process can result in numerous variations of the polymer. With many potential outcomes, it is crucial to accurately determine the physical attributes of the polymer. For many applications, but specifically for the tire industry, one of the standard methods for determining viscoelastic properties is through dynamic mechanical analysis (DMA). The raw data from DMA is adjusted through the Williams, Landel, and Ferry (WLF) shift equation to create a master curve for the rubber specimen. This study investigates methods for the calculation of friction coefficient, and suggests a new code to predict the friction coefficient. Several discussions in the paper will be for validation of the code and its range of applications. We then implement a parametric analysis to determine which factors critically affect the friction factor results. By finding the sensitivity of the inputs to the new code for friction coefficient, the critical inputs can be identified. The parameters that are studied are the storage modulus, loss modulus, surface asperities heights, the surface asperities wavelength, and the adhesive contribution to friction. The adhesion and hysteresis contributions to the friction coefficient are also discussed in this paper. It is shown that the adhesive contribution plays a large role in determining the friction coefficient. The data from the study will determine the effect that direct DMA testing has on the friction coefficient as well as tire performance indicators. The indicators that the direct testing affects the most are the wet traction indicator, the snow traction indicator, and the ice traction indicator.

Committee: Siamak Farhad (Advisor); Alex Povitsky (Committee Member); Shing-Chung (Josh) Wong (Committee Member) Subjects: Automotive Materials; Materials Science; Mathematics; Polymers

Doctor of Philosophy, University of Akron, 2015, Biomedical Engineering

The number of people suffering from urolithiasis (formation of kidney stones) has increased over the past few decades. Ureteroscopic stone extraction devices are effective and ubiquitous tools in the management of urolithiasis. These devices, however, have the potential to cause injury to the ureter. Avulsion and perforation of the ureter as a result of excessive forces on the extraction device are the most serious complications of this treatment. Moreover, effective management of kidney stones depends on their size, location, and composition. In this dissertation, different treatment modalities for kidney stone disease are discussed. In the first part of this dissertation, analysis of the peristaltic movement, which drives the urine from the kidneys to the bladder through the ureter, is presented. More specifically, different sizes and types of kidney stones are modeled inside the ureter and their effects on the urine flow and pressure on the ureter wall are studied. It is concluded that in addition to the stone size, different stone shapes result in different pressures on the ureter wall. In the second part of this dissertation, a kidney basket prototype with a force sensor has been developed. This device was built based on the measured injury forces during basketing, using two different setups, a benchtop model and an ex-vivo porcine ureter. The force sensor provides instantaneous visual force measurements imposed on the ureter wall during stone extraction, and thereby, aids in reducing the risk of complications by highlighting the safety and hazardous extraction forces. The tests were performed in conjunction with the Division of Urology, Southern Illinois University, School of Medicine, Springfield, IL. The results obtained from these tests were consistent with injury forces reported in the literature. The designed prototype, together with the stone analysis performed in this study could potentially lead to an improvement in the treatment of urolithiasis (open full item for complete abstract)

Committee: Ajay Mahajan Dr. (Advisor); Abhilash Chandy Dr. (Committee Member); Rouzbeh Amini Dr. (Committee Member); Bing Yu Dr. (Committee Member); Jutta Luettmer-Strathmann Dr. (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Design

Doctor of Philosophy, The Ohio State University, 2007, Chemistry

An inductively coupled plasma dynamic reaction cell mass spectrometer (ICP-DRC-MS) was used to study reactions between elemental analyte ions, elemental and polyatomic background ions (such as argides (ArM+), oxides (MO+) and doubly charged species (M2+)) with NH3 and C2H4. NH3 reduced most ion signals from a deionized water sample (DI H2O), argides (ArM+), oxides (MO+) and doubly charged species (M2+). C2H4 was less powerful at reducing background ion signals from a deionized water sample (DI H2O) and generated new in-cell product ions, increasing the background signal at many masses. Loss of ion signal rates were calculated and reported in orders of magnitude per (mL/min increase in reaction gas flow rate (in Argon equivalent units)). NH3 attenuated most elemental ion signals between 1 and 3 orders of magnitude although rates up to five orders of magnitude were seen. C2H4 reduced most elemental ion signals up to 2 orders of magnitude although rates up to 3 orders of magnitude were seen. The products of reactions between NH3 and 70 elemental ions were identified, categorized and quantified. The major product ions from C2H4 and monoisotopic elemental ions greater than 100 amu were identified and categorized. Effects of the Mathieu parameter q (or RPq) on elemental and product ion signals in an NH3 pressurized reaction cell were studied. Comparisons of product ion prevention via RPq value and kinetic energy discrimination were made. A simulation of ion signal (sample and blank) and estimated detection limits (EDL) versus reaction gas flow rate was created and designed to aid selection of the optimum reaction gas flow rates. A strategy for method development with the ICP-DRC-MS is presented. Results using this strategy are shown for the detection of 27Al+ in the presence of 11B16O+, detection of 51V+ in the presence of 35Cl16O+. Also included are the results for the detection of 75As+ as 75As16O+ and 80Se+ as 80Se16O+ at masses 91 and 96, respectively, to avoid the sp (open full item for complete abstract)

Committee: Susan Olesik (Advisor) Subjects: Chemistry, Analytical

Doctor of Philosophy, Case Western Reserve University, 2008, Mechanical Engineering

The scope of this dissertation is to develop and apply a non-intrusive molecular Rayleigh scattering diagnostic that is capable of providing time-resolved simultaneous measurements of gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 32 kHz. Molecular Rayleigh scattering is elastic light scattering from molecules; the spectrum of Rayleigh scattered light contains information about the gas temperature and velocity of the flow. Additionally, the scattered signal is directly proportional to the molecular number density. These characteristics are utilized in the development of the measurement technique. This dissertation results in the following: 1. Development of a point-based Rayleigh scattering measurement system that provides time-resolved simultaneous measurement of temperature, velocity, and density at sampling rates up to 32 kHz. 2. Numerical modeling of the light scattering and detection process to evaluate uncertainty levels and capabilities of the measurement technique. 3. Validation of the developed measurement system in benchmark flow experiments in which velocity and temperature fluctuations were decoupled and independently forced at various amplitudes and frequencies. 4. Demonstration of simultaneous measurement of all three quantities in an electrically-heated free jet facility at NASA Glenn Research Center. 5. Comparison of Rayleigh scattering measurements in all experiment phases with thermal anemometry measurements. The experimental measurements are presented in terms of first-order time-series results that are measured directly by the technique, and second-order statistics, such as power spectral density and rms fluctuations, which are calculated from the direct time-resolved quasi-instantaneous measurements. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements. Experiments were (open full item for complete abstract)

Committee: Chih-Jen Sung (Advisor) Subjects: Engineering, Mechanical