Publication: ANÁLISIS TEÓRICO EXPERIMENTAL DE RESPUESTA ESTRUCTURAL EN BANCO DE PRUEBAS PARA ALTERNADORES DE CAMIONES MINEROS
Date
2016
Authors
ROSAS CASTILLO, CRISTIAN ANTONIO
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Abstract
Se utilizó un programa de análisis dinámico con elementos finitos para modelar un banco de pruebas de alternadores de camiones mineros, incluyendo la fundación. El objetivo fue proponer modificaciones estructurales que disminuyeran los problemas de vibraciones que suelen ocurrir durante las pruebas de los alternadores. El modelo tuvo que ser validado a partir de ensayos realizados sobre la estructura.Los alternadores de camiones mineros que son identificados con problemas en sus componentes, son enviados a una empresa de re-manufactura con el fin de ser probados en el banco. El problema es que para algunos alternadores durante las pruebas normales se inducen fuertes vibraciones, esto debido a que las frecuencias de operación del alternador coinciden con las frecuencias de resonancia del sistema alternador-motor eléctrico-estructura del banco.Mediante pruebas con un alternador GTA41 en desaceleración, desde una frecuencia de rotación sobre la normal de operación, se registró con acelerómetros tri-axiales para distintos puntos de la estructura, los movimientos del sistema hasta detenerse. Además, para corroborar los registros, se grabó con una cámara de alta velocidad fijada en el muro del taller. Finalmente se realizaron ensayos de impacto para encontrar las resonancias de los componentes por separado.Los resultados de los ensayos corroboraron que el alternador incurre en resonancias durante las frecuencias de operación de la prueba, las que debido al bajo amortiguamiento de la estructura metálica, amplificaron las vibraciones registradas. Además, con los registros obtenidos durante la prueba con varios acelerómetros se detectaron movimientos del tipo cabeceo, balanceo y torsionales en torno al eje vertical. Finalmente se observó que todos los talleres que realizaron la prueba de desaceleración para el mismo tipo de alternador presentaron comportamientos algo diferentes.Los resultados del análisis modal indicaron que las mejores soluciones para elevar las frecuencias del sistema era adicionar puntos de apoyo al conjunto alternador-motor eléctrico, bajar el centro de masas del sistema y rigidizar el chasís metálico. También se aumentó el espesor y se iteró con las dimensiones de la losa para encontrar la mejor respuesta del sistema frente a las frecuencias rotacionales.
A dynamic analysis program with finite elements was used to model a test bench for mining truck alternators and the foundation. The aim was to propose structural modifications that would reduce the vibration problems that often occur during alternator testing. The model had to be validated with tests performed on the structure.Alternators of mining trucks that are identified with problems in their components are sent to a re-manufacturing company in order to be tested on the bench. The problem is that some alternators during the normal tests induce strong vibrations because the operating frequencies of the alternator coincide with the resonance frequencies of the alternator/electric motor structure.By testing a GTA41 alternator in deceleration, from a rotational frequency above the normal operating with tri-axial accelerometers at different points of the structure registering movement of the system until cessation. In addition, to corroborate the records, tests were recorded with a high speed camera fixed to the wall of the workshop. Finally, impact tests were performed to find resonances of the components separately.The results of the tests corroborated that the alternator incurs resonances during the operating frequencies of the test, which due to the low damping of the metallic structure amplifies the recorded vibrations. In addition, with the records obtained from several accelerometers, it was found that the foundation tends to rotate around its horizontal axis during the test, causing translations of the alternator/electric motor axis. Finally, it was observed that all the workshops that performed the deceleration test for the same type of alternator presented different magnitudes of vibration and resonances at different operating frequencies.The results of the modal analysis indicated that the best solutions to raise the frequencies of the system were to add support points to the alternator/electric motor axis, to lower the mass center of the system and to reinforce the metallic chassis. The thickness of the slab was also increased and iterated with the sides of the foundation to find the best response of the system to the rotational frequencies.
A dynamic analysis program with finite elements was used to model a test bench for mining truck alternators and the foundation. The aim was to propose structural modifications that would reduce the vibration problems that often occur during alternator testing. The model had to be validated with tests performed on the structure.Alternators of mining trucks that are identified with problems in their components are sent to a re-manufacturing company in order to be tested on the bench. The problem is that some alternators during the normal tests induce strong vibrations because the operating frequencies of the alternator coincide with the resonance frequencies of the alternator/electric motor structure.By testing a GTA41 alternator in deceleration, from a rotational frequency above the normal operating with tri-axial accelerometers at different points of the structure registering movement of the system until cessation. In addition, to corroborate the records, tests were recorded with a high speed camera fixed to the wall of the workshop. Finally, impact tests were performed to find resonances of the components separately.The results of the tests corroborated that the alternator incurs resonances during the operating frequencies of the test, which due to the low damping of the metallic structure amplifies the recorded vibrations. In addition, with the records obtained from several accelerometers, it was found that the foundation tends to rotate around its horizontal axis during the test, causing translations of the alternator/electric motor axis. Finally, it was observed that all the workshops that performed the deceleration test for the same type of alternator presented different magnitudes of vibration and resonances at different operating frequencies.The results of the modal analysis indicated that the best solutions to raise the frequencies of the system were to add support points to the alternator/electric motor axis, to lower the mass center of the system and to reinforce the metallic chassis. The thickness of the slab was also increased and iterated with the sides of the foundation to find the best response of the system to the rotational frequencies.
Description
Catalogado desde la version PDF de la tesis.
Keywords
ESTRUCTURA DE PRUEBA , FRECUENCIAS DE RESONANCIA , RESPUESTA ESTRUCTURAL