EN - PCCIN - Produção Científica do Centro de Investigação Naval (CINAV)
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Percorrer EN - PCCIN - Produção Científica do Centro de Investigação Naval (CINAV) por autor "Alves, João"
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- Dynamic Maintenance on Ships: Integrating Threat DimensionPublication . Lampreia, Suzana; Vilarinhos, Valter; Lobo, Victor; Morgado, Teresa; Alves, JoãoMaintenance management on ships is a pillar for operations success. As in other industry systems and equipment’s, maintenance has evolute from a corrective maintenance to systematic preventive, to condition based maintenance. To accomplish a condition-based maintenance with high quality and a dynamic maintenance concept can be considered various non-destructive techniques, and data from sensors. After obtaining the data from the various systems, it should be registered, and statistical models should be developed and applied to enhance the human evaluation about the data. The Failure Mode and Effect Critically Analysis may be one reliability evaluation and design tech-nique for data treatments and to calculate the risk about a system or equipment. As a case study it was selected a propulsion diesel engine and it was applied a Failure Mode and Effect Critically Analysis, which was modified, FMECA-CC, to integrate various sever-ities, and to integrate data from condition control and the Threat. To limit the study presentation on the present article, it was decided to developed only the variable Threat. The threat was integrated on the study because it represents a study on a military envi-ronment. It was considered 5 levels for the threat variable, which are manually introduced by an operator who receives hierarchic input about the threat environment and introduces on a propulsion decision-making software. The results showed that FMECA-CC may be applied on diesel engine monitoring on board ships integrated data from sensors and also the variable threat.
- Innovation in structural integrity prediction modelsPublication . Lampreia, Suzana; Alves, João; Morgado, Teresa; Martins, RuiStrong predictive models are needed for precise, reliable mechanical design in the aeronautical industry, to control the typically observed fatigue var-iability. Especially with the advances of additive manufacturing and the emer-gence of organic geometries. This paper reviews the development of structural integrity models, from early empirical formulations to advanced physics-based methods. The historical reliance on empirical models like Paris Law and the edge of its concept, The NASGRO, which, despite their utility, are often limited due to their empirical nature, is analyzed. One of the central themes of discussion is the scientific conflict between the "Global Driving Force" school, centered on extrinsic crack closure, and the “Local Cyclic Plasticity school, mainly focused on the induced plasticity at the crack tip. The limitations of both “schools” are scrutinized, including the inability of closure-based models to describe the be-havior at high stress ratios and the kinematic constrains linked to the local plas-ticity models. At the end of this research paper, the Christopher-James-Patterson (CJP) model is presented as a conciliatory approach, considering the crack as a plastic inclusion within an elastic material. This model provides a mechanistic description that accounts for plasticity-induced shielding and retardation without requiring arbitrary geometry correction factors. This review suggests the CJP model as the future of fatigue crack growth predictions.