Publication: DETERMINACIÓN DE VIDA A LA FATIGA EN EJE DE TURBINA FRANCIS, APLICACIÓN UTILIZANDO ANSYS
Loading...
Date
2015-09
Authors
CARRASCO BUSTAMANTE, FRANCISCO JAVIER
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
El diseño de máquinas, vehículos y estructuras, requiere de un correcto uso de los
materiales para asegurar que una falla estructural no ocurra. La seguridad, la
confiabilidad, la durabilidad y los requerimientos económicos han sido el objetivo de
ingenieros y diseñadores para poder comprender el comportamiento mecánico de los
materiales en situaciones dinámicas y complejas, y así, ser aplicado a un fenómeno
conocido como fatiga.
Estudios demuestran que entre el 80 y 90 por ciento de todas las fallas
estructurales ocurren a través de un proceso de fatiga. Además, los costos económicos
asociados a estas fallas por fatiga se podrían reducir en cerca de un 30 por ciento con
la aplicación de la tecnología en la predicción fatiga [1]. Por tanto, el incremento de
altos costos, las nuevas tecnologías, máquinas y equipos sofisticados, además de la
interacción con vidas humanas en su servicio, hacen necesario confiar y asegurar un
buen funcionamiento, y especialmente, un diseño adecuado y preciso.
En este trabajo se desarrolla un análisis para estimar la vida a la fatiga del eje de
una turbina Francis, a través de métodos teóricos y simulación numérica computacional
basada en el método de elementos finitos (MEF). El eje es parte de un sistema de
generación de energía y es sometido a cargas dinámicas durante su operación. El
problema surge desde una solución práctica para la fijación axial de algunos
deflectores, y ciertamente, se modifica la geometría con una perforación, de modo que
es necesario calcular una nueva resistencia a la fatiga del eje en esta región, junto con
su nueva vida a la fatiga.
Para desarrollar el análisis de vida a la fatiga en la zona crítica, en primer lugar, se
realiza una estimación teórica, con código Matlab, utilizada como una referencia en los
resultados, después, y por medio del software ANSYS Mechanical 14.5, el eje es
modelado con una geometría equivalente simplificada utilizada para realizar la
simulación numérica y análisis por MEF para fatiga.
Finalmente, en la sección 5.1 de análisis de resultados, se concluye con los valores
obtenidos, la nueva vida a la fatiga del eje es aproximadamente 121,5 [años] y cumple
con los requerimientos durante su tiempo de servicio.
The machines, vehicles and structures designs requires a correct use of the materials to ensure that any structural failure do not occur. Safety, reliability, durability and economic requirements have been the target of engineers and designers to understand the mechanical behavior of materials under dynamic and complex situations, and thus, be applied to the phenomenon known as fatigue. Studies show that between 80 and 90 percent of all structural failures occurs due to a fatigue process. Furthermore, the economic costs associated to these fatigue failures could be reduced in almost 30 percent with the application of technology into fatigue prediction [1]. Therefore, the increasingly higher cost, new technologies, machines and large equipments, besides the interaction with human lives to its service, make it necessary trust and ensure a right performance, especially, a suitable and accurate design. The current work carries out an analysis is developed for estimating the fatigue lifetime of main shaft of a Francis turbine, through theoretical methods and computational numerical simulation based on finite element method (FEM). The main shaft is part of a power generation system submitted to dynamic loads during its performance. The problem arises from a practical solution for axial fixing of some baffles, and certainly, the geometry is modified with a drill, so it is necessary to recalculate new fatigue strength for the main shaft in this region, featuring its new fatigue life. To develop an analysis to the fatigue lifetime in the critical region, first, a theoretical estimate, with Matlab code was used as a reference in the results, then, by the ANSYS Mechanical software 14.5, the main shaft is modeled with a simplified equivalent geometry used for numerical simulation and analysis by MEF for fatigue. Finally, in the 5.1 section of analysis of results, was concluded that with the obtained values, the new fatigue lifetime of the main shaft is approximately 121,5 [years] and requirements during service are fulfilled.
The machines, vehicles and structures designs requires a correct use of the materials to ensure that any structural failure do not occur. Safety, reliability, durability and economic requirements have been the target of engineers and designers to understand the mechanical behavior of materials under dynamic and complex situations, and thus, be applied to the phenomenon known as fatigue. Studies show that between 80 and 90 percent of all structural failures occurs due to a fatigue process. Furthermore, the economic costs associated to these fatigue failures could be reduced in almost 30 percent with the application of technology into fatigue prediction [1]. Therefore, the increasingly higher cost, new technologies, machines and large equipments, besides the interaction with human lives to its service, make it necessary trust and ensure a right performance, especially, a suitable and accurate design. The current work carries out an analysis is developed for estimating the fatigue lifetime of main shaft of a Francis turbine, through theoretical methods and computational numerical simulation based on finite element method (FEM). The main shaft is part of a power generation system submitted to dynamic loads during its performance. The problem arises from a practical solution for axial fixing of some baffles, and certainly, the geometry is modified with a drill, so it is necessary to recalculate new fatigue strength for the main shaft in this region, featuring its new fatigue life. To develop an analysis to the fatigue lifetime in the critical region, first, a theoretical estimate, with Matlab code was used as a reference in the results, then, by the ANSYS Mechanical software 14.5, the main shaft is modeled with a simplified equivalent geometry used for numerical simulation and analysis by MEF for fatigue. Finally, in the 5.1 section of analysis of results, was concluded that with the obtained values, the new fatigue lifetime of the main shaft is approximately 121,5 [years] and requirements during service are fulfilled.
Description
Keywords
COMPORTAMIENTO MECÁNICO , FATIGA , PREDICCIÓN , FALLA , VIDA A LA FATIGA , SIMULACIÓN NUMÉRICA , MEF , DAÑO A LA FATIGA , ANSYS