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Full-Text Articles in Mechanical Engineering
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
LSU Doctoral Dissertations
Irreversible material degradation due to cyclic mechanical loading is investigated utilizing the concept of thermodynamic entropy, plastic strain energy, and temperature slope measurement. Uniaxial tension-compression and fully-reversed bending fatigue tests are performed over a wide range of loading conditions with metallic and composite materials subject to both constant- and variable-amplitude loading. A methodology is developed for the estimation of the fatigue fracture entropy (FFE) and fatigue toughness of metallic specimens in a rapid fashion. It is found that the FFE and the fatigue toughness of each material tested are within a small band. The value of FFE is found to …
An Experimental Investigation Of Corrosion Fatigue Life Via Thermographic Method, Richard Wayne Purvis
An Experimental Investigation Of Corrosion Fatigue Life Via Thermographic Method, Richard Wayne Purvis
LSU Master's Theses
The effect of prior corrosion fatigue damage on the thermographic response of 1018 low carbon steel is investigated. Specimens were subject to rotating bending fatigue at 38 Hz loading frequency while being exposed to a 3.5% NaCl and distilled water solution. Some specimens were subject to corrosion fatigue for part of their fatigue life and then their thermographic response measured under fatigue in air at 62 Hz loading frequency. Fatigue tests in air with thermographic measurement were performed as a comparison. It was observed that the initial temperature rise after corrosion fatigue fits the previously proposed model for air fatigue, …
Using A Sleep And Activity Monitor To Operationalize Fatigue Risk Management, Vanessa Bégat Seitz
Using A Sleep And Activity Monitor To Operationalize Fatigue Risk Management, Vanessa Bégat Seitz
LSU Master's Theses
When a person continues to work despite being fatigued, an accident may occur or productivity may decrease. Reducing fatigue related accidents is complicated due to the subjective nature and pervasiveness of the feeling of fatigue. Because finding one universal definition or measure of fatigue is problematic, fatigue is typically measured by a combination of factors such as amount of sleep obtained, physical or cognitive work performed, or sleepiness which can then be related back to a measure of performance. Until recently, sleep measurement was restricted to a lab setting; however, with the emergence of actigraph devices, it is now possible …
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. …
Thermodynamic Approach To Fatigue Failure Analysis In Metals And Composite Materials, Mehdi Naderi Abadi
Thermodynamic Approach To Fatigue Failure Analysis In Metals And Composite Materials, Mehdi Naderi Abadi
LSU Doctoral Dissertations
Fatigue is a dissipative process and must obey the laws of thermodynamics. In general, it can be hypothesized that the degradation of machinery components is a consequence of irreversible thermodynamic processes that disorder a component, and that degradation is a time dependent phenomenon with increasing disorder. This suggests that entropy —a fundamental parameter in thermodynamics that characterizes disorder— offers a natural measure of component degradation. The majority of the existing methods for prediction of fatigue are limited to the study of a single fatigue mode, i.e., bending or torsion or tension-compression. Further, the variability in the duty cycle in a …
Fatigue Fracture And Microstructural Analysis Of Friction Stir Welded Butt Joints Of Aerospace Aluminum Alloys, Vinay Raghuram
Fatigue Fracture And Microstructural Analysis Of Friction Stir Welded Butt Joints Of Aerospace Aluminum Alloys, Vinay Raghuram
LSU Master's Theses
Friction-Stir-Welding (FSW) has been adopted as a major process for welding Aluminum aerospace structures. Al-2195, which is one of the new-generation Aluminum alloys that has been used on the external tank of the new super lightweight external tank of the space shuttle. The Lockheed Martin Space Systems (LMSS), Michoud Operations in New Orleans is continuously pursuing Friction-Stir-Welding technologies in its efforts to advance fabrication of the external tanks of the space shuttle. The future launch vehicles which will have to be reusable, m, an dates the structure to have good fatigue properties, which prompts an investigation into the fatigue behavior …