8 research outputs found
Fatigue behavior of ultra high strength structural materials
No full textUltra high strength structural AF1410 steel is commonly used in critical aircraft structural components in aerospace and marine application, because it possesses high toughness and outstanding mechanical properties. However, there exists a lack of knowledge of its corrosion-fatigue properties and hydrogen embrittlement. This study attempts to undertake an accurate simulation of actual service conditions mimicking a realistic environment and to characterize the hold time-fatigue interaction on aircraft structural members. AF1410 steel was evaluated in marine environment and electrolytic hydrogen charged conditions. A decrease in lifetime of AF1410 was observed as a function of increasing severity of the simulated environment and reducing test frequency. The crack growth rate of hydrogen charged specimens and under simulated marine environment was higher than specimens evaluated without hydrogen (air), when evaluated using sinusoidal and trapezoidal loading forms. Furthermore, hydrogen charged specimens at one and two lateral surfaces exhibited a drastic reduction in the lifetime caused by simultaneous effect of hydrogen and fatigue loading. Our results show that hold time effect under environmental hydrogen embrittlement conditions was detrimental on fatigue lifetime of AF1410 steel which is
frequently ignored under environmental temperatures. Additionally, the hydrogen charged specimens underwent a change in the fracture modes from ductile to
brittle. Since, hydrogen has not permeated the entire specimens; the experiments
provided a more realistic approach to the study of large aircraft components during service. In addition, a phenomenological mathematical model for lifetime prediction was developed to account for the effect of hydrogen on the fatigue crack growth rate for AF1410 steel. Finally, the phenomenological model developed shows an excellent agreement between the experimental and predicted results.El acero AF1410 es comúnmente usado en componentes estructurales críticos en aplicaciones aeroespaciales y marinas, ya que posee una alta tenacidad y propiedades mecánicas excepcionales. Sin embargo, existe una falta de conocimiento de las propiedades de corrosión-fatiga de este acero de ultra alta resistencia. Este estudio intenta iniciar una simulación adecuada de las condiciones actuales de servicio de componentes estructurales imitando un ambiente real y también caracterizar términos de tiempo cortos de carga sostenida combinado con fatiga. AF1410 fue evaluado en ambiente marino y condiciones de cargado electrolítico de hidrógeno. Se observó una disminución en el tiempo de vida del AF1410 como función de incrementar la severidad del medio ambiente y reduciendo la frecuencia. La velocidad de crecimiento de especimenes cargados con hidrógeno fue más alta que especimenes evaluados sin hidrógeno. El tiempo de vida para especimenes expuestos a ambiente corrosivo e hidrógeno disminuyó bajo formas de cargas sinusoidales y trapezoidales. Además, especimenes cargados con hidrógeno en ambas caras laterales exhibieron una drástica reducción en el tiempo de vida por una acción simultánea de hidrógeno y tiempo de carga sostenida. Nuestros resultados mostraron que el tiempo de carga sostenida fue crítico sobre el tiempo de vida del AF1410, el cual es frecuentemente ignorado bajo temperaturas ambientales. Adicionalmente, especimenes cargados con hidrógeno experimentaron un cambio en el modo de fractura de dúctil a frágil. Debido a que el hidrógeno no permea los especimenes enteros, los experimentos proveen una aproximación real al estudio de estructuras aéreas grandes en servicio. En adición, un modelo fenomenológico para predecir la vida del material fue desarbolado para tomar en cuenta el efecto del hidrógeno sobre el crecimiento de grieta en fatiga para el AF1410. Finalmente, el modelo fenomenológico desarrollado mostró un excelente acuerdo entre los resultados predichos y experimentales.NAVY & Office of Naval Research200
Effect of Initial Debond Crack Location on the Face/core Debond Fracture Toughness
No full textThis paper studies the effect of initial crack location on the face/core debond fracture toughness under different mixed mode loading conditions. The mixed mode loading at the crack tip is defined in terms of the mode-mixity. In order to achieve the desired initial debond crack location, a pre-cracking technique is developed, where the mode-mixity, number of cycles, crack increment and load level are accurately controlled. Results show that the debond fracture resistance of foam-cored sandwich specimens depends on parameters such as loading condition (mode-mixity), core and face properties, as well as initial debond crack location. Lower fracture toughness values were measured for specimens with the initial crack location in the face laminate
Caracterización del recurso eólico en el observatorio meteorológico Luis Olazo Olivera - Perayoc de la UNSAAC, Cusco: 2012 – 2023
No full textEl presente estudio tiene como objetivo caracterizar el recurso eólico en el Observatorio Meteorológico Luis Olazo Olivera – Perayoc, de la Universidad Nacional de San Antonio Abad del Cusco (UNSAAC), a partir de datos de velocidad y dirección del viento registrados entre los años 2012 y 2023 mediante una estación automática Davis, con mediciones cada cinco minutos. Se excluyeron los años 2020 y 2021 debido a registros incompletos ocasionados por la pandemia. Los datos fueron procesados en R, RStudio y Excel, generando 120 promedios mensuales representativos. Se calculó la densidad del aire considerando la altitud (3365 msnm), la densidad de potencia del viento, las direcciones predominantes mediante rosas de viento y los parámetros de la distribución de Weibull. Los resultados indican una velocidad promedio general de 0,4817 m/s y una densidad de potencia de 0,0459 W/m², valores muy inferiores al umbral mínimo de 200 W/m² establecido por el Atlas Eólico del Perú. Las direcciones predominantes fueron Oeste (W) y Sur-Sureste (SSE). El modelo de Weibull presentó parámetros k = 3,348 y c = 0,4886 m/s, lo que indica una distribución estable y coherente con la media general de velocidad. Aunque el recurso eólico no cumple con los estándares para generación de energía a gran escala, su estabilidad y caracterización lo convierten en una fuente útil para fines experimentales, educativos y estudios de dinámica del viento en entornos urbanos de baja velocidad. Estos resultados aportan información relevante para investigaciones y proyectos en contextos similares
The Dynamics of Al-Irsyad Al-Islamiyah Educational Institution (1914-2000)
No full textThis study aims to determine the background of the establishment of the Al-Irsyad Al-Islamiyyah Educational Institution and the education system at the Al-Irsyad Al-Islamiyyah Educational Institution. The type of research used in this study is library research. The point is to answer the problem formulation, the author collects data from books, journals, scientific papers, and so on. The study also used an induction and deduction approach where the collected data was drawn to generalizations to conclusions. The results of this research are the background for the establishment of the Al-Irsyad Al-Islamiyyah Educational Institute. The organization was founded in 1914 by Sheikh Ahmad Surkati Al-Anshori, a great cleric from Mecca who came from Sudan. Al-Irshad Al-Islamiyyah focuses on education, teaching, social, and da'wah at the national level. Al-Irshad Al-Islamiyyah is committed to purifying the teachings of Islam, expanding science, and developing a civilized and Islamic moral society. Al-Irshad Al-Islamiyyah aims to purify tawhid, worship and amaliyah Islam. Engaged in education and da'wah. To realize this goal, AI Irsyad has established hundreds of formal schools and non-formal educational institutions throughout Indonesia. And in its later development, Al-Irshad activities also penetrated the health sector, by establishing several hospitals. The largest are currently Al-Irsyad Hospital in Surabaya and RS. Siti Khadijah in Pekalongan
Cooperative Learning Strategies for Engaging History Education: Exploring GI and TGT Models
No full textHistory learning is considered boring learning for students, this learning is considered less useful because it is identical to memorization, therefore educators must have expertise in mastering learning methods and models so that learning in the classroom becomes not boring. This writing aims to see the relevance of the Group Investigation (GI) and Team Game Tournament (TGT) learning models. The method used in this article is descriptive qualitative. Qualitative descriptive research method is one type of analysis that explains a phenomenon or data obtained. The phenomenon or data is obtained from books, journals, and articles with collection techniques namely editing, organizing, and finding. The results of the analysis conducted by the author regarding the definition of GI and TGT, then the relevance of GI and TGT in learning history. The conclusion of this writing is that by using interesting and interactive learning models such as GI and TGT, history learning which is considered boring will become interesting learning for students
Literatura del desarraigo en la novela “Maldeojo” de Huilo Ruales Hualca
No full textLa investigación tiene como objetivo indagar sobre la literatura del desarraigo en la obra “Maldeojo” del autor ecuatoriano contemporáneo Huilo Ruales, con el fin de poner en evidencia las características utilizadas en sus escritos y su latente estilo. En consecuencia se ha requerido utilizar una indagación de enfoque cualitativo de tipo bibliográfico-documental, el cual consistió en adquirir información necesaria para el desarrollo del trabajo investigativo. El soporte teórico está sustentado en fuentes de verificación como: libros, artículos y entrevistas de los hechos vividos por el autor siendo estas experiencias la base para sus obras. Asimismo, se utilizó la técnica de análisis documental para su posterior interpretación en el estudio narratológico de la obra. Dejando una pauta para futuras investigaciones en el tema.The research aims to investigate the literature of rootlessness in the literary work “Maldeojo” of the contemporary Ecuadorian author Huilo Ruales, in order to highlight the characteristics used in his writings and his latent style. Consequently, it has required to use an inquiry of qualitative approach of bibliographic-documentary type, which consisted to acquire information necessary for the development of the research. The theoretical support is based on verification sources such as: books, articles and interviews of the facts lived by the author, these experiences being the basis for his literary works. Likewise, the technique of documentary analysis was used for its subsequent interpretation in the narratological study of the literary work. Leaving a guideline for future research on the subject
Noisy Kites? Exploring Noise Annoyance for Airborne Wind Energy Systems with a Laboratory Listening Experiment
No full textNoisy Kites? Exploring Noise Annoyance for Airborne Wind Energy Systems with a Laboratory Listening Experiment
No full textWind EnergyAircraft Noise and Climate EffectsOrganisation & Governanc
