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Articles 1 - 12 of 12
Full-Text Articles in Mechanical Engineering
Energy Dissipation And Entropy Generation During The Fatigue Degradation: Application To Health Monitoring Of Composites, Ali Kahirdeh
Energy Dissipation And Entropy Generation During The Fatigue Degradation: Application To Health Monitoring Of Composites, Ali Kahirdeh
LSU Doctoral Dissertations
In this dissertation, an experimental approach for characterizing energy dissipation and degradation evolution in a woven Epoxy/Glass (G10/FR4) laminate subjected to fully reversed bending fatigue test is presented. Infrared thermography and acoustic emission are utilized to characterize the degradation progression. The results show similar evolutionary response indicating the presence of three degradation stages. The effect of the surface cooling on the fatigue life of the laminates is investigated both experimentally and analytically. The results show that the life of the laminate is highly dependent on the temperature and that surface cooling can significantly increase the fatigue life of the laminate. …
The Effects Of Asymmetric Micro Ratchets On Pool Boiling Performance, Lance Austin Brumfield
The Effects Of Asymmetric Micro Ratchets On Pool Boiling Performance, Lance Austin Brumfield
LSU Doctoral Dissertations
Nucleate boiling is an attractive method for achieving high heat flux at low superheat temperatures. It is frequently used for industrial applications such as heat exchangers and is being considered to cool advanced central processing units (CPU) which produce heat fluxes on the order of 1 MW/m2 and are becoming increasingly less efficient to cool via forced conduction of air. The issue with implementing nucleate boiling as a cooling mechanism lies in the difficulty of quantifying the numerous and complex mechanisms which control the process. A comprehensive nucleate boiling model has yet to be formulated and will be required in …
Crack Self-Healing In Sic/Spinel Nanocomposite, Fariborz Tavangarian
Crack Self-Healing In Sic/Spinel Nanocomposite, Fariborz Tavangarian
LSU Doctoral Dissertations
Spinel is one of the best known and widely used ceramic materials. It has good thermal shock resistance, high chemical inertness in both acidic and basic environments, excellent optical and dielectric properties, high strength at both elevated and normal temperatures, and has no phase transition up to the melting temperature (2135°C). Spinel is used in the metallurgical, electrochemical, and chemical industrial fields. It has also found some applications in dentistry, catalyst supports, humidity sensors, reinforcing fibers, photoluminescent materials, etc. One of the limitations of spinel ceramic is its brittleness. Furthermore, at high temperature applications, a rapid heating or cooling can …
Innovative Heat Transfer Augmentation Techniques In Mechanical Face Seal, Nian Xiao
Innovative Heat Transfer Augmentation Techniques In Mechanical Face Seal, Nian Xiao
LSU Doctoral Dissertations
Excessive heat generated at the face seal contact interface has been recognized as one of main causes of failure of mechanical seals. In the past few decades various efforts have been attempted to remove heat from the contact interface uniformly in order to reduce the interfacial temperature, eliminate thermally-induced failure, and thus increase the life of a mechanical seal. Two innovative heat transfer augmentation techniques - surface texturing and built-in phase change device - have been developed in our laboratory to effectively enhance the heat transfer in mechanical face seal. Surface texturing can increase the surface area, change the near …
Novel Syntheses And Surface Modifications Of Electrode Materials For Superior Lithium-Ion Batteries, Jianqing Zhao
Novel Syntheses And Surface Modifications Of Electrode Materials For Superior Lithium-Ion Batteries, Jianqing Zhao
LSU Doctoral Dissertations
Rechargeable lithium-ion battery is one of the most promising energy conversion and storage systems that offers high energy and powder densities, long service life and assuring safety. Performance of lithium-ion batteries crucially relies on electrochemical characteristics of electrode materials, i.e., anode and cathode materials. This dissertation work aims at developing novel electrode materials with high capacity, excellent cycling stability and remarkable rate capability for next-generation lithium-ion batteries. The effects of surface modifications for LiMn2O4 cathode materials are studied by depositing ultrathin conformal amphoteric oxides via atomic layer deposition (ALD). In the case of ZnO coating, the thickness of ZnO ALD …
Applications Of The Variational Approach To Fracture Mechanics, Ataollah Mesgarnejad
Applications Of The Variational Approach To Fracture Mechanics, Ataollah Mesgarnejad
LSU Doctoral Dissertations
In this study we present the variational approach to fracture mechanics as a versatile tool for the modeling of the fracture phenomenon in solids. Variational fracture mechanics restates the problem of initiation and propagation of cracks in solids as an energy minimization problem. The edifice of this energy minimization problem is such that unlike other methods (e.g. extended finite element method XFEM, cohesive-zone methods) the variational approach to fracture mechanics, diminishes the need for an a priori knowledge of the crack path or ad hoc assumptions in the form of path selection laws. We will show applications of the variational …
Utilization Of Carbon Nanofibers Grown On Glass Microballoons (Nmbs) In Point-Of-Care Diagnostic Devices, Emmanuel Gikunoo
Utilization Of Carbon Nanofibers Grown On Glass Microballoons (Nmbs) In Point-Of-Care Diagnostic Devices, Emmanuel Gikunoo
LSU Doctoral Dissertations
The use of point-of-care (POC) diagnostic systems holds great promise for the early detection of various diseases. However, detection limits for commercially available POC systems have not been able to meet the lower cutoffs offered by the specialized laboratory testing methods. Research into the use of carbon nanofibers (CNFs) grown on glass microballoons in POC devices was studied. The growth of several millions of the CNFs on each microballoon (NMBs) presented a large surface area with high probability of capturing minute concentrations of biospecies. Functionalization of the NMBs with the carboxyl group needed for biospecies conjugation was achieved by air …
Meso-Scale Analysis Of Deformation Induced Heating In Granular Metalized Explosives By Piston Supported Waves, Sunada Srinath Nagamani Chakravarthy
Meso-Scale Analysis Of Deformation Induced Heating In Granular Metalized Explosives By Piston Supported Waves, Sunada Srinath Nagamani Chakravarthy
LSU Doctoral Dissertations
Shock sensitivity of heterogeneous explosive composites is dependent on the formation of hot-spots which are small regions of elevated temperatures within the material. Changes in the initial meso-structure (i.e. packing density, composition, particle size and shapes) of the explosives can significantly alter the hot-spot fields in the material and thereby affect its shock sensitivity. In this study, an explicit, 2D, Lagrangian finite and discrete element technique is used to numerically simulate the deformation induced heating of granular mixtures of explosive (HMX), and metal (Al) particles due to piston supported uniaxial deformation waves (400 ≤ Up ≤ 800 m/s). A number …
Hot Corrosion Behaviour Of New Candidates For Thermal Barrier Coatings Application In Turbine Simulated Environments, Mohammad Hamed Habibi
Hot Corrosion Behaviour Of New Candidates For Thermal Barrier Coatings Application In Turbine Simulated Environments, Mohammad Hamed Habibi
LSU Doctoral Dissertations
Thermal barrier coatings (TBCs) are used gas turbine engines. The current material of choice (YSZ) degrades when it contacts with impurities arise from low quality fuels such vanadium and sulfur. YSZ cannot be used in temperature higher than 900˚C. Higher efficiency and performance of gas turbine engines will require a new generation of thermal barrier coatings (TBCs). In current work, hot corrosion behavior of new candidates including Gd2Zr2O7, ZrO2 stabilized with Ta2O5, zirconia stabilized with both Ta2O5 and Y2O3 and zirconia stabilized with CeO2 and TiO2 is investigated. For YSZ case, the reaction between NaVO3 and Y2O3 produces YVO4 and …
Novel Nanostructured Titania And Titania Nanocomposites For Photovoltaics And Photocatalysis, Xinning Luan
Novel Nanostructured Titania And Titania Nanocomposites For Photovoltaics And Photocatalysis, Xinning Luan
LSU Doctoral Dissertations
With the consumption of energy continually increasing around the world and the main source of this energy, fossil fuels, slowly being depleted, the need for alternate sources of energy is becoming more and more pertinent. Demand for solar energy has experienced exponential increase over the last decade. Nanostructured TiO2 has attracted significant attention due to its nontoxicity, low cost and wide applications in photovoltaics and photocatalysis. This research is focused on novel synthesis and surface modification of TiO2 nanotube arrays for applications in advanced dye-sensitized solar cells (DSSCs) and efficient photocatalysis. The first part of this work entails fast synthesis …
Energy And Thermodynamically Based Approaches For Analysis Of Damage In Contact Problems, Afshin Babaie Aghdam
Energy And Thermodynamically Based Approaches For Analysis Of Damage In Contact Problems, Afshin Babaie Aghdam
LSU Doctoral Dissertations
A novel methodology for analysis of damage in contact problems in presented. Two important categories of contact damage are studied, namely crack nucleation and adhesive wear. The proposed methodology is primarily based on the laws of energy and thermodynamics, and as such offers great advantages by unifying the analysis of damage in a variety of contact configurations. Crack nucleation is the first damage type analyzed. For this purpose, the line-contact fretting configuration is chosen. A thermodynamically-based continuum damage mechanics (CDM) approach is employed. Intense stress gradients in the contact region are found to be highly influential in the crack nucleation …
Tomographic Imaging Of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy (Tdlas), Avishek Guha
Tomographic Imaging Of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy (Tdlas), Avishek Guha
LSU Doctoral Dissertations
This work concentrates on enabling the usage of a specific variant of tunable diode laser absorption spectroscopy (abbr. TDLAS) for tomogaphically reconstructing spatially varying temperature and concentrations of gases with as few reconstruction artifacts as possible. The specific variant of TDLAS used here is known as wavelength modulation with second harmonic detection (abbr. WMS-2f) which uses the wavelength dependent absorbance information of two different spectroscopic transitions to determine temperature and concentration values. Traditionally, WMS-2f has generally been applied to domains where temperature although unknown, was spatially largely invariant while concentration was constant and known to a reasonable approximation (_x0006_+/- 10% …