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1	Thermo-Mechanical Fatigue Assessment of Marine Boiler : Using linear Finite Element Analyses Alagbada, Adefemi Samuel January 2020 (has links) This thesis is on fatigue crack growth assessments of a thermomechanical loaded Marine Boiler- Sunrod CPDB12. The installation position of the marine boiler in the ship in relation to its fatigue life under mode 1 loading is investigated. Thermomechanical loading embodies pressures, temperatures, RAO, subjected to the rigid body dynamic of ship in the marine environment. Linear elastic fracture mechanics (LEFM) method was used is predicting the growth rates of the welding flaws at the joint based on stress range of the Paris law relationship. FEA Numerical simulation delivered better crack growth rate assessments and life predictions of the smallest detectable flaws in the boiler. The identified smallest detestable flaws at the welding joint diminishing the designed safe life of the boiler significantly. Also, installation position within the ship do affect the fatigue life of the boiler. Marine Boiler FEA Thermo-mechanical Loading LEFM Paris law Flaws RAO. Engineering and Technology Teknik och teknologier
2	Fatigue Crack Growth Mechanisms in Al-Si-Mg Alloys Lados, Diana Aida 04 February 2004 (has links) Due to the increasing use of cyclically loaded cast aluminum components in automotive and aerospace applications, fatigue and fatigue crack growth characteristics of aluminum castings are of great interest. Despite the extensive research efforts dedicated to this topic, a fundamental, mechanistic understanding of these alloys' behavior when subjected to dynamic loading is still lacking. This fundamental research investigated the mechanisms active at the microstructure level during dynamic loading and failure of conventionally cast and SSM Al-Si-Mg alloys. Five model alloys were cast to isolate the individual contribution of constituent phases on fatigue resistance. The major constituent phases, alpha-Al dendrites, Al/Si eutectic phase, and Mg-Si strengthening precipitates were mechanistically investigated to relate microstructure to near-threshold crack growth (Delta Kth) and crack propagation regimes (Regions II and III) for alloys of different Si composition/morphology, grain size, secondary dendrite arm spacing, heat treatment. A procedure to evaluate the actual fracture toughness from fatigue crack growth data was successfully developed based on a complex Elastic-Plastic-Fracture-Mechanics (EPFM/J-integral) approach. Residual stress-microstructure interactions, commonly overlooked by researches in the field, were also comprehensively defined and accounted for both experimentally and mathematically, and future revisions of ASTM E647 are expected. Microstructure Elastic-Plastic Fracture Mechanics Crack closure A356 J-integral Residual stress Heat treatment Fatigue crack growth mechanisms Threshold stress intensity factor Plastic zone Paris law Fracture toughness Roughness Aluminum castings Cracking Metals Fracture Aluminum alloys Cracking

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Thermo-Mechanical Fatigue Assessment of Marine Boiler : Using linear Finite Element Analyses

Fatigue Crack Growth Mechanisms in Al-Si-Mg Alloys