Saudi Cultural Missions Theses & Dissertations
Permanent URI for this communityhttps://drepo.sdl.edu.sa/handle/20.500.14154/10
Browse
4 results
Search Results
Item Restricted Investigation of the Combined Effects of Temperature and Humidity on Fracture Behaviour of Al-Mg-Si-Mn Alloys: Implications in the Coastal Region(Cranfield University, 2024-03) Alqahtani, Ibrahim Mohammed; Starr, AndrewAluminium alloys have been integral to numerous engineering applications due to their favourable strength, weight, and corrosion resistance combination. However, the performance of these alloys in coastal environments is a critical concern, as the interplay between fatigue crack growth rate and fracture toughness under such conditions remains relatively unexplored. The combined effect of interdependencies between temperature and humidity under localised corrosion on the fracture toughness of aluminium alloys has not been extensively studied. Little attention has been paid to this phenomenon due to the challenge in understanding its behaviour, and the difficulty in predicting the effect of these factors on fracture behaviour. Therefore, the present study aims to address this knowledge gap and improve the understanding of the interdependencies between the coupled effects of temperature and humidity on the fracture toughness of Al–Mg–Si–Mn alloy. This research can have practical implications for selecting and designing materials in coastal environments. Fracture toughness experiments were carried out by simulating the coastal environments, such as localised corrosion, temperature, and humidity, using compact tension specimens. The fracture toughness increased with varying temperatures from 20°C to 80°C and decreased with variable humidity levels between 40% and 90%, revealing that the Al–Mg–Si–Mn alloy is susceptible to corrosive environments. Using a curve-fitting approach that mapped the micrographs to temperature and humidity conditions, an empirical model was developed, which revealed that the interaction between temperature and humidity was complex and followed a nonlinear interaction supported by microstructure images of SEM and collected empirical data. The fatigue crack growth rate (FCGR) of aluminium alloys under the combined influence of temperature and humidity remains a relatively unexplored area, receiving limited attention due to its challenges in predicting the combined effect of these factors. The challenge was to investigate and address the specific mechanisms and interactions between temperature and humidity, as in coastal environment conditions, on the FCGR of aluminium alloy. The fatigue pre- ii cracked compact tension specimens were corroded for seven days and then subjected to various temperature and humidity conditions in a thermal chamber for three days to simulate coastal environments. The obtained data were analysed to determine the influence of temperature and humidity on the FCGR of Al-Mg-Si-Mn alloy. An empirical model was also established to precisely predict fatigue life cycle values under these environmental conditions. The correlation between fatigue life cycles and fracture toughness models was also examined. The Al-Mg-Si-Mn alloy exhibits a 34% increase in the Paris constant C, indicating reduced FCGR resistance due to elevated temperature and humidity levels. At the same time, fatigue, corrosion, moisture-assisted crack propagation, and hydrogen embrittlement lead to a 27% decrease in the threshold stress intensity factor range. The developed model exhibited accurate predictions for fatigue life cycles, and the correlation between fracture toughness and fatigue life cycles showed less than 10% error, indicating a strong relationship between these parameters.23 0Item Restricted Corrosion Behaviour of Additively Manufactured Al-Si-Cu Alloy Processed by High Pressure Torsion (HPT)(University of Southampton, 2024-09-19) Alayli, Adel; Gao, NongThe corrosion behaviour of an Al-Si-Cu alloy has been investigated in the project. The samples were subjected to high pressure torsion (HPT) in order to explore the relation between HPT and corrosion resistance and strength of the material. In order to make comparisons, the HPT was carried out under 0.25, 0.5, 1, 5 and 10 turns at room temperature. Corrosion tests have also been carried out on the samples that have undergone HPT testing in order to evaluate their corrosion resistance. The samples were grouped into two groups: group 1 (1 hour corrosion) and group 2 (24 hours corrosion). The summary of Group 1 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 5 hpt sample has shown the highest corrosion resistance and the PPC showed that the 0.5 hpt sample has shown the highest corrosion resistance. On the other hand, the summary of Group 2 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 10 hpt sample has shown the highest corrosion resistance and the PPC showed that the 5 hpt sample has shown the highest corrosion resistance. From the chemical analysis (EDS results), it was found that the 0.5 hpt sample has shown the lowest amounts of O which means it has the lowest corrosion resistance. On the contrary, the EDS results revealed that the 1 and 10 hpt samples have shown the highest amounts of O which means they have the highest corrosion resistance. On another note, the hardness results have shown that the lowest hardness was recorded for the as-received sample whereas the highest hardness was for the 5 hpt sample. The Alicona results have shown that the 5 and 10 hpt samples have shown the lowest corrosion rate, i.e. best corrosion resistance. Moreover, the surface roughness of the oxide layer (from Alicona), after corrosion, showed that the roughness is highest for the as-received samples compared to significantly lower roughness levels for the HPT-processed samples.9 0Item Restricted Corrosion Behaviour of Additively Manufactured Al-Si-Cu Alloy Processed by High Pressure Torsion (HPT)(University of Southampton, 2023) Alayli, Adel; Gao, NongThe corrosion behaviour of an Al-Si-Cu alloy has been investigated in the project. The samples were subjected to high pressure torsion (HPT) in order to explore the relation between HPT and corrosion resistance and strength of the material. In order to make comparisons, the HPT was carried out under 0.25, 0.5, 1, 5 and 10 turns at room temperature. Corrosion tests have also been carried out on the samples that have undergone HPT testing in order to evaluate their corrosion resistance. The samples were grouped into two groups: group 1 (1 hour corrosion) and group 2 (24 hours corrosion). The summary of Group 1 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 5 hpt sample has shown the highest corrosion resistance and the PPC showed that the 0.5 hpt sample has shown the highest corrosion resistance. On the other hand, the summary of Group 2 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 10 hpt sample has shown the highest corrosion resistance and the PPC showed that the 5 hpt sample has shown the highest corrosion resistance. From the chemical analysis (EDS results), it was found that the 0.5 hpt sample has shown the lowest amounts of O which means it has the lowest corrosion resistance. On the contrary, the EDS results revealed that the 1 and 10 hpt samples have shown the highest amounts of O which means they have the highest corrosion resistance. On another note, the hardness results have shown that the lowest hardness was recorded for the as-received sample whereas the highest hardness was for the 5 hpt sample. The Alicona results have shown that the 5 and 10 hpt samples have shown the lowest corrosion rate, i.e. best corrosion resistance. Moreover, the surface roughness of the oxide layer (from Alicona), after corrosion, showed that the roughness is highest for the as-received samples compared to significantly lower roughness levels for the HPT-processed samples.17 0Item Restricted The Oral Environment Factors Affecting the Corrosion of Dental Implants(2023-07-28) Alhamad, Mostafa; Mathew, Mathew; Sukotjo, Cortino; Barão, ValentimOne of the main challenges facing dental implant success is peri-implantitis, the inflammation of gingival tissues around a dental implant with progressive bone loss. Recent evidence indicates that titanium (Ti) corrosion products and undetected-residual cement are potential risk factors for peri-implantitis. The literature on the impact of various types of dental cement on Ti corrosion is very limited. Growing evidence indicates that titanium (Ti) corrosion products are one of the potential risk factors for peri-implantitis. The literature on the impact of various oral factors on Ti corrosion is minimal. Thus, this research project aimed to evaluate the effect of Ti products, inflammatory factors, types of dental cement, and the effect of challenged host cells on Ti corrosion processes. In the present project, the experiments involved subjecting Ti surfaces to different environments, including increased Ti ion and particle concentration in artificial saliva, adding inflammatory products to artificial saliva, and subjecting the Ti surface to three different dental cement types. The Ti surfaces were also subjected to a simulated environment, where gingival fibroblasts and macrophages were challenged with Ti ions and particles. The samples were subjected to corrosion sequence following the American Society for Materials and Testing guidelines 61 (ASTM). The corrosion sequence entailed electrochemical tests such as open circuit potential, potentiostatic polarization, electrochemical impedance spectroscopy, and cyclic polarization. The results revealed that the increased concentration of Ti ions in artificial saliva is directly proportional to the corrosion rate. The addition of inflammatory products to artificial saliva increased the corrosion kinetics. Certain types of dental cement increased corrosion rates. Finally, the challenged fibroblasts and macrophages led to increased corrosion rates and kinetics. Such severe environments that accelerate Ti corrosion may contribute to the pathogenesis of peri-implantitis.18 0