INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 15, No. 7, pp. 1331-1335 JULY 2014 / 1331 © KSPE and Springer 2014 Bending Fatigue Life Evaluation of Cu-Mg Alloy Contact Wire Guo Zhen 1 , Yongseok Kim 1 , Li Haochuang 1 , Jae-Mean Koo 1 , Chang-Sung Seok 1,# , Kiwon Lee 2 , and Sam-Young Kwon 2 1 School of Mechanical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gteonghi-do, South Korea 2 Korea Railroad Research Institute, 176, Cheoldobangmulgwan-ro, Uiwang-si, Gyeonghi-do, South Korea # Corresponding Author / E-mail: seok@skku.edu, TEL: +82-31-290-7446, FAX: +82-31-299-4866 KEYWORDS: Cu-Mg contact wire, Bending fatigue test, Operating condition, Copper alloy Contact wire is one of the most important components used to supply electricity to railway vehicles which equipped with a pantograph. When the speed of electric vehicle is not as high as now, the failure of contact wire caused by friction and wear behaviors of carbon strip/contact wire were considered more important. But the fatigue fracture become more and more important for the failure of contact wires on account of several fatigue fractures happened while the speed of electric vehicle increase continuously. A bending fatigue tester simulating the working conditions of contact wires developed by Kang and etc has been used to evaluate the fatigue characteristic of pure copper and Cu-Sn alloy contact wires. In this study, this bending fatigue tester also is used to evaluate the fatigue characteristics of Cu-Mg alloy contact wire which developed for 400km/h high speed rail in Korea. Test result is also compared with the result of Kang's research on pure copper contact wire. Finally, in order to evaluate the fatigue life of contact wires for any mean stress, the relationships between plastic strain and fatigue life were abstained for two kinds of contact wires combined the FE analysis. Manuscript received: September 11, 2013 / Revised: December 19, 2013 / Accepted: December 20, 2013 1. Introduction With the rapid development of global economy, the high-speed and heavy haul electric vehicles are urgently required. 1 High-speed railway technology has advanced competitively all over the world, and the maximum speeds of trains have steadily increased in countries like Japan (405 km/h), France (574.8 km/h), Germany (403.7 km/h), South Korea (430 km/h), and China (483 km/h). 2,3 Contact wire is one of the most important components used to supply electricity to railway vehicles which equipped with a pantograph in the system of overhead wires. At first, the failure of contact wire caused by friction and wear behaviors of carbon strip/contact wire were considered more important. But the fatigue fracture become more and more important for the failure of contact wires on account of several fatigue fractures happened while the speed of electric vehicle increase continuously. 3,4 Especially, when the driving speed of electric railway vehicles rapidly increases to 400 km/h, the higher tension force applied on contact wire in order to increase the wave propagation speed. 5 Also, alone with the more harsh vibration and increase of internal average tensile stress, the Cu-Mg alloy contact wire was developed for 400 km/h high-speed electric railways with more excellent mechanical performance than pure copper contact wire. A bending fatigue tester simulating the working conditions of contact wires developed by Kang 3 and etc has been used to evaluate the fatigue characteristic of pure copper and Cu-Sn alloy contact wires, and certified work well. 3,6 In this paper, we use the bending fatigue test system for contact wire simulating real conditions 3 to do the bending fatigue testing of Cu-Mg Alloy contact wire (for 400 km/h high-speed railways), and the fatigue life is compared with the results of existing pure copper wire (300 km/h-level). In addition, the strain gauge was attached to the top of the contact wire where is known as the most vulnerable location to happened fatigue failure to measure the bending strain. Based on the measured bending strain and obtained strain-stress curve through the tensile testing, the relationship between maximum stress at the top of the damage section and fatigue life was obtained from the strain-fatigue life curve using the bending fatigue test system for contact wire simulating real conditions. Also, in order to evaluate the fatigue life of contact wires for any mean stress, the relationships between plastic strain and fatigue life were abstained for two kinds of contact wires combined the FE analysis. Finally, the fracture surface was observed to DOI: 10.1007/s12541-014-0473-z