Transpiration cooling as potential replacement of multi-hole effusion cooling for gas turbine engines combustion liner application is investigated by comparing their cooling film effectiveness based on the mass transfer analogy (CFEM). Pressure sensitive paint was used to measure CFEM over PM surfaces which was found to be on average 40% higher than multi-hole effusion cooling. High porosity PM with low resistance to flow movement were found to offer uneven distribution of exiting coolant, with large amounts leaving the trailing edge, leading to lopsided CFEM. Design of anisotropic PM based on PM properties (porosity, permeability, and inertia coefficient) were investigated using numerical models to obtain more uniform CFEM. Heat transfer analysis of different PM showed that anisotropic samples offered better thermal protection over isotropic PM for the same porosity. Comparison between cooling film effectiveness obtained from temperatures CFET against CFEM revealed large differences in the predicted protection. This is attributed to the assumptions made to apply CFEM, nonetheless, CFEM remains a good proxy to study and improve transpiration cooling. A method for creating a CAD model of designed PM is proposed based on critical characteristics of transpiration cooling for future use in 3D printing manufacturing.

Indiana University-Purdue University Indianapolis (IUPUI) / Previous works suggest that 80% to 90% of failures observed in the rotary machines are accounted for fatigue failure. And it is observed that cyclic stresses are more critical than steady stresses when the failure occurred is due to fatigue. One of the most expensive industries involving rotary machines is the Oil and Gas industry. The large drilling tools are used for oil extracts on-shore and off-shore. There are several forces that act on a drilling tool while operating below the earth's surface. Those forces are namely pressure, bending moment and torque. The tool is designed from the baseline model of the former tool in Solidworks and Design Molder. Here load acting due to pressure and torque accounts for steady stress i.e., Mean Stress and loading acting due to bending moment account for fluctuating stress i.e., Alternating Stress. The loading and boundary conditions have been adapted from Halliburton’s previous works for the LWD drill tool to better estimate the size of the largest possible transducer. The fatigue analysis of static load cases is carried out in Ansys Mechanical Workbench 19.0 using static structural analysis. The simulation is run to obtain results for total deformation, equivalent stress, and user-defined results. The component is designed for infinite life to calculate the endurance limit. Shigley guidelines and FKM guidelines are compared as a part of a study to select the best possible approach in the current application. The width of the imaging pocket is varied from 1.25 inches to 2.0 inches to accommodate the largest possible transducer without compromising the structural integrity of the tool. The optimum design is chosen based on the stress life theory criteria namely Gerber theory and Goodman Theory.

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The research in this master's thesis examines the mechanics of primate and early hominid feeding within the context of hypotheses about australopithecine diets. Specifically, this work will be helpful in testing the hypothesis that derived craniodental features in australopithecines are adaptations for feeding on hard, brittle, seasonally available foods. These foods may have been “fallback” items that could be fed upon during periods of scarcity, and thus their consumption may have been ecologically important to survival of early humans. In order to test the fallback theory, accurate estimates of bite force to initiate a crack in a hard food source using different tooth shapes is essential. These estimates help test the theory in two ways. First, the estimation of bite force for different tooth profiles helps in explaining effect of tooth morphology on fracture of hard food sources. This will test the premise that some species have more efficient tooth shapes for fracturing hard food than other species. Second, the obtained bite force will be used as an input to full scale finite element skull model of different species. Stress and strain distributions in critical regions of the skull will be helpful in understanding feeding adaptations of the different species during evolution. In this work a fast and accurate finite element analysis method was developed to estimate bite force required to initiate crack in a hard food source like the macadamia nut with different tooth morphologies. The proposed research will help in understanding the effect of tooth shape on the bite force required to initiate a crack in a hard food source In first experiment we simulated nut biting behavior found in ancient hominid by indenting macadamia nuts with aluminum alloy replicas of primate teeth. Finite element analysis simulation of the biting behavior provided insight into stress profile in the nut at the time of fracture. The results were statistically inconclusive due to huge variation in thickness, diameter and material properties of macadamia nut. In order to study effect of teeth shape on bite force, another study was performed in this work where four different hominoid species namely A.afransis, A.africanus, A.boisei and A.robustus of similar age level, were considered. Cast iron replicas of these hominoid teeth were created. In order to eliminate variability in thickness, diameter and material properties, we used acrylic hemispheres as a macadamia nut substitute. Statistical significance testing and FEA revealed that flatter teeth produces significantly lower force required to fracture acrylic hemisphere as compared to pointed and sharp teeth with comparable fracture stress. Results suggest that pointed teeth produces higher stresses in the food resulting in lower force required to fracture but at the same time stresses in teeth is also high increasing the probability of enamel failure. During the evolution teeth might have evolved to obtain optimum shape which provides tread off between minimum force required to fracture hard food items and minimum stress in enamel to reduce probability of enamel fracture Past work in estimating bite force is limited to experimental testing. Physical testing of bite force is tedious and time consuming. The proposed combination of physical testing and supporting finite element analysis will be helpful in reducing lengthy physical testing. The main advantage of this method is the comparatively low computational cost and the ability to estimate full field stresses and strains, as opposed to measuring surface strain at specific points. As our modeling and experimental methods become more refined, we anticipate being able to assess the degree to which tooth morphology affects the force needed to fracture hard food items, thereby providing insights into the dietary adaptations of living and extinct primates, including fossil humans.

The Forestry Department at Mississippi State University has been contracted to design and test a novel beam to be used to create crossing platforms for cranes operating in muddy, swampy areas. To date, they have performed stress analyses on 30 beams, but their physical testing method requires costly amounts of material and man hours. It is theorized that the finite element method may be used as an alternative method of analysis in order to reduce costs. The focus of this study is to create models of tested beams using the finite element solver, ANSYS, and verify the accuracy of these models using the results of the Forestry Department’s physical testing.

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This investigation concerns the design, analysis, and initial testing of a new, two-component wall shear gage for 3D, high-temperature flows. This gage is a direct-measuring, non-nulling design with a round head surrounded by a small gap. Two flexure wheels are used to allow small motions of the floating head. Fiber-optic displacement sensors measure how far the polished faces of counterweights on the wheels move in relation to a fixed housing as the primary measurement system. No viscous damping was required. The gage has both fiber-optic instrumentation and strain gages mounted on the flexures for validation of the newer fiber optics. The sensor is constructed of Haynes 230, a high-temperature nickel alloy. The gage housing is made of 316 stainless steel. All components of the gage in pure fiber-optic form can survive to a temperature of 1073 K. The bonding methods of the backup strain gages limit their maximum temperature to 473 K. The dynamic range of the gage is from 0-500 Pa (0-10g) and higher shears can be measured by changing the floating head size. Extensive use of finite element modeling was critical to the design and analysis of the gage. Static structural, modal, and thermal analyses were performed on the flexures using the ANSYS finite element package. Static finite element analysis predicted the response of the flexures to a given load, and static calibrations using a direct force method confirmed these results. Finite element modal analysis results were within 16.4% for the first mode and within 30% for the second mode when compared with the experimentally determined modes. Vibration characteristics of the gage were determined from experimental free vibration data after the gage was subjected to an impulse. Uncertainties in the finished geometry make this level of error acceptable. A transient thermal analysis examined the effects of a very high heat flux on the exposed head of the gage. The 100,000 W/m2 heat flux used in this analysis is typical of a value in a scramjet engine. The gage can survive for 10 minutes and operate for 3 minutes before a 10% loss in flexure stiffness occurs under these conditions. Repeated cold-flow wind tunnel tests at Mach 2.4 with a stagnation pressure from 3.7-8.2 atm (55-120 psia) and ambient stagnation temperature (Re=6.6x107/m) and Mach 4.0 with a stagnation pressure from 10.2-12.2 atm (150-180 psia) and ambient stagnation temperature (Re=7.4x107/m) were performed in the Virginia Tech Supersonic Wind Tunnel. Some of these tests had the gage intentionally misaligned by 25o to create a virtual 3D flow in this nominally 2D facility. Experimental results gave excellent agreement with semi-empirical prediction methods for both the aligned and 25o experiments. This fiber-optic skin friction gage operated successfully without viscous damping. These tests in the supersonic wind tunnel validated this wall shear gage design concept. / Ph. D.

Labyrinth seal force estimates are important to the prediction of the stability of turbomachinery. The force prediction methods fall into several categories: experiments, bulk flow analysis, and finite volume analysis. Finite volume analysis can be split into two subcategories: self-developed and commercial. In this research, a commercial computational fluid dynamics (CFD) program called ANSYS-CFX was used to predict the forces generated in a labyrinth seal whirling at specified speeds. The results were compared to data from VT-FAST, a bulk flow code, and TASCflow, another commercial CFD program. It was shown that there were discrepancies among the results, and several hypotheses were made as to the reason for these discrepancies. Additionally, ANSYS-CFX was used to study the effect of labyrinth seal eccentricity ratio on the resultant force generated. It was shown that the radial force component within the seal behaved linearly with respect to eccentricity ratio. However, the tangential force component had no distinguishable relationship with the eccentricity ratio. It was hypothesized that the lack of a relationship was caused by the small fluctuations in the inlet swirl. Although the inlet swirl varied very little at each eccentricity ratio, it was shown there was a relationship between the tangential force and inlet swirl. / Master of Science