Browsing by Keyword "Fracture mechanics"
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Item Finite element method for sustainable and resilient structures made with bar and fiber -reinforced EAFS concrete(2024-07) Garcia-Llona, Aratz; Piñero, Ignacio; Ortega-López, Vanesa; Santamaría, Amaia; Aguirre, Miquel; E&I SEGURAS Y RESILIENTESStructural engineers have to address the climate change challenge by designing sustainable and resilient structures. At this juncture, Electric Arc Furnace Slags (EAFS), a steel-industry waste, are used in replacement of natural aggregates to enhance concrete properties. Moreover, steel and synthetic fibers are added to improve the postcracking behavior while the traditional bar reinforcement enhances the tensile performance. This makes EAFS concrete substantially ductile compared to normal concrete, which contributes to a higher structural resiliency, and hence minimizes functionality disruptions. However the use of fiber and bar -reinforced EAFS concrete in structures is still limited due to the uncertainties introduced by EAFS and fibers. This justify the development of advanced modeling techniques (ie. Finite element Analysis, FEA), which can be used to predict the behavior of EAFS concrete structures at the designing stage. This work build up from the extensive work of the coauthors in the testing of EAFS concrete and, more recently, in the developed FEA of fiber-reinforced EAFS concrete. In this paper the modeling of bar reinforcement is added to the FEA to study the behavior of structural elements made with fiber-reinforced EAFS concrete. The presented FEA is validated through full-scale experiments (four-point flexural test), which shows that the presented FEA is appropriate. The presented numerical model enables to study phenomena difficult to study from experiments or in-situ such as the cracking. It is worth noting that the addition of steel fibers reduced the crack mouth opening displacement in 29.3% and the depth of the cracks in 12.7% in the presented EAFS concrete.Item The influence of temperature on hydrogen environmentally assisted cracking of AA7449-T7651 in moist air(2021-03) De Francisco, Unai; Larrosa, Nicolas O.; Peel, Matthew J.; MATERIALES PARA CONDICIONES EXTREMASThe 7xxx series of aluminium alloys are sensitive to intergranular hydrogen environmentally assisted cracking (HEAC) in moist air environments. A new generation of 7xxx alloys used in aircraft components (including AA7449) have been found to be more sensitive to HEAC. This investigation aims to quantify the HEAC crack growth rates of AA7449-T7651 in moist air at different temperatures. Double cantilever beam specimens were loaded at a constant displacement and placed in moist air (80–85% relative humidity) at temperatures between 25 and 80 °C. Regular measurements of crack length permitted the determination of the crack growth rate as a function of the stress intensity factor (KI) during stage I (high KI dependence of growth rate) and stage II (low KI dependence of growth rate). Increasing the temperature was found to increase the crack growth rate during stage II cracking, following Arrhenius kinetics. The activation energy for the stage II crack growth rate at a stress intensity factor of 14.5 MPam was estimated as 84.7 kJ/mol. Additionally, the threshold stress intensity factor for HEAC was found to decrease with increasing temperature. This was attributed to a higher hydrogen solubility at higher temperatures. The crack growth rate of AA7449-T7651 at room temperature was similar to that of overaged AA7050 and AA7075-T7651, ranging between 1.3 and 2.1 × 10−7 mm/s. It was inferred that the alloy temper has more influence than the composition during stage II cracking at room temperature.