Browsing by Author "Roque, Rui Manuel Resendes"
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- A critical review on damage accumulation in multiaxial fatigue modelsPublication . Roque, Rui Manuel Resendes; Anes, Vítor Manuel RodriguesFracture and fatigue are common causes of failure in mechanical components of structures, needing a comprehensive understanding of the underlying physical mechanisms by mechanical design engineers. An area that requires further investigation is the impact of loading type on the fatigue strength of materials. Proportional and nonproportional loads lead to different fatigue lives, even when subjected to the same loading amplitudes. Even within proportional loads, the fatigue life can vary depending on the ratio between shear and normal stresses. Numerous models have been proposed in the literature to address these concerns, but a universally applicable model for estimating fatigue strength considering loading effects is yet to be developed. This dissertation presents a thorough literature review focusing on multiaxial fatigue, covering topics such as the phenomenological characterization of fatigue, critical plane models, cycle counting methods, fatigue damage monitoring and bibliographic data. During the review, a modified equivalent strain amplitude (MESA) model, raised pertinent questions that are addressed in subsequent chapters. A case study was conducted that utilizes multiaxial fatigue data of the high strength steel 42CrMo4, which was obtained from literature sources. The analysis was made to include plane orientations ranging from -90° to 90° while evaluating ten multiaxial loading paths. The research hypothesis aimed to evaluate the effectiveness of a proposed critical plane model in determining the crack initiation plane and estimating the fatigue life of variable amplitude loading paths, without relying on cycle counting methods. In order to simplify the demonstration of this method, alternative critical plane models were employed to assess their efficiency in determining these parameters. The obtained results revealed that the MESA critical plane model is indeed effective in successfully estimating fatigue life under multiaxial fatigue loading paths while others cannot without the use of additional cycle counting methods. Nevertheless, the MESA critical plane model exhibited unsatisfactory results when assessing the crack initiation plane in comparison to other critical plane models like SWT, Fatemi-Socie, Brown-Miller, and Liu. The estimations of these models for the crack initiation plane showed relatively strong consistency, except for the MESA model. Furthermore, a bibliographic analysis was included with the purpose of better illustrating the current state of the engineering field that researches multiaxial fatigue and damage accumulation approaches. A study on scientific papers published since the 2000’s until now is conducted by outlining the output and growth trend of said publications in the selected research areas, the most influential countries and journals and by establishing the connection between internationalization and multiaxial fatigue and damage accumulation. Findings regarding this analysis indicate a significant growth in the research field, with a substantial increase in the number of published documents each year. The People's Republic of China emerges as the leading contributor with 1434 publications across all the mentioned subjects, closely followed by the USA and Germany. Furthermore, it is noteworthy that nearly half of the countries worldwide are actively involved in researching these subjects, demonstrating a diverse range of nationalities contributing to the field. Interestingly, Portugal ranks among the top 15 countries in all selected keyword categories, highlighting its involvement and contribution in the research.