Engineering critical structures, such as pressure vessels and pipelines, are designed to withstand a variety of in-service loading specific to their intended application. Random vibration excitation is observed in most of the structural component applications in the offshore, aerospace, and nuclear industry. Likewise, fatigue life estimation for such components is fundamental to verify the design robustness assuring structural integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still largely used for damage assessment on fatigue estimations, even though, its limitations are well-known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects, and trans-granular crack propagation are hardly predicted, indicates that a probabilistic characterization of the material behavior is needed. In this work, the methodology was applied to a Titanium alloy structural component. Low alloyed titanium alloys have no tendency to corrosion cracking in high-temperature high-pressure water containing impurities of chloride and oxygen found in a steam generator of nuclear power plants. The inherent uncertainties of the fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL) statistic method. Furthermore, a frequency domain technique is used to determine the response power spectrum density (PSD) function of a structural component subjected to a random vibration profile excitation. The fatigue life of the component is then estimated through a probabilistic linear damage cumulative model.
First and above all, I thank God, for providing me with this opportunity. Mygratitude to my supervisor Prof. Dr. Diego Felipe Sarzosa Burgos for his support, guidance, tutoring and patience. A special thanks to my colleagues from Continental Brasil, Mr. Glenan Lago for the encouragement and Mr. Douglas Custodio for the support with the testing. This dissertation is dedicated to my beloved wife Natalie Cuzziol Pascualinotto, for her unconditional support during the elaboration of this work, to my son Miguel Cuzziol Pascualinotto and my daughter Olivia Cuzziol Pascualinotto for being my source of inspiration.
Engineering structures are constructed to withstand a variety of in-service loading specific to their application. Random vibration excitation is observed in most structural components in the offshore, aerospace, and automotive industries. Likewise, fatigue life estimation for structural elements is fundamental for verifying the design and assurance of structural integrity throughout service. The linear cumulative Palmgren-Miner's damage rule is widely used for damage assessment, despite its well-known limitations. The scatter of fatigue testing data suggests that a probabilistic characterization of the material behavior should be considered during fatigue life predictions. In this work, the inherent uncertainties of the fatigue phenomenon and the influence of a geometrical discontinuity are explored in the fatigue life estimation of a structural component subjected to random vibration profiles. The fatigue life estimated using the methodology proposed in this work presented a good agreement with testing results using Dirlik frequency domain counting methods.
This work proposes a new test methodology to characterize the fracture toughness values for either brittle or ductile materials, such as steels of risers and pipelines used in the oil and gas industry by using non-standard four-point bending specimens. Four-point bending (4PB) specimens show to be reliable configuration to characterize fracture toughness values. The methodology involves obtaining compliance equations, stress intensity factors, the proportionality factors between the deformation energy and J-integral, known as η-factor. This study evidences the impact of geometry variation on the crack-tip constraint. Laboratory tests were performed with four-point bending specimens. These experiments were compared with experimental data of standardized geometries SE(B) and SE(T). The results from the preliminary experimental campaign validated the numerical analysis. Thus, the proposed equations can be used to obtain the fracture toughness values using four-point bending specimens.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.