Deterioration and Performance Analyses of Subway Electric Multiple Units

초록

In order to guarantee the performance and safety during the operation of subway electric multiple units (EMUs), which were used for over 20 years, it is required to assess the current deterioration and reliability conditions for EMU components as well as the whole systems. Also, according to Korean urban transit railway law, in order to validate the extension possibility for legal lifetime of 25 years in subway EMUs, the current condition assessment, safety assessment, remaining lifetime evaluation, etc. need to be performed. Based on the precision diagnosis results, the legal lifetime of subway rolling stocks could be extended up to 5 years. In this investigation, the EMUs used for over twenty years were selected for the deterioration and reliability evaluation. The subway rolling stocks used for this investigation were composed of 6 EMUs including 2 control cars, 2 motor cars, and 2 trailer cars, and they were the chopper controlled subway rolling stocks. Moreover, various types of engineering analysis techniques were used for the current performance and safety evaluation. Several characterization means including nondestructive evaluation (NDE) techniques, corrosion testing, and three-dimensional measurements, were employed for the evaluation of car bodies and bogies in EMUs. The NDE techniques include ultrasonic testing for the measurement of thickness changes and flaw detection, magnetic particle testing for the detection of surface flaws, and radiography method for the defects in weldments. In order to confirm the changes in dimension of car body or bogies, three- dimensional measurements were performed using the laser tracker. The measurement results were compared with the dimensions in original drawing. Furthermore, stress and structural analyses using commercial finite element method (FEM) software provided important information on stress distribution and load transfer mechanisms, and the FEM results were compared with running safety testing results during test running. After deterioration analyses of EMUs, in order to investigate performance characteristics of deteriorated subway rolling stocks, several engineering assessment methods, such as the acceleration, vibration, and braking performance tests, were carried out on subway EMUs.