Abstract: Traction set and brake device are the key parts of the high speed electric multi-unit(EMU). The traction sets make the carbody and the bogies move together. The brake devices stop the train. Traction performance and brake action exert forces on the devices and the bogies to cause the damage and fatigue of the structures. Currently, the traction and brake investigations focus on the traction power, drive forces, brake type, brake efficiency and so on. Seldom studies related to the loads of the two type of devices of the EMU could be found. The measurement methods of the traction loads and brake forces are presented. The devices are manufactured to test the two type of loads. The loads are measured with field experiment at Datong-Xian high speed railway. After dealt with the sampled data, the two kinds of forces are obtained in time domain and frequency domain. The effect of the operation speed, curve passing and running performance of the train on the loads are analyzed. The dynamic characteristics of the loads are presented with the operation condition of the train such as start, acceleration, idling running and brake. Rain Flow Count Method are introduced to implement the loads count. The load distributions are presented with different operation speed of the train. Equivalent loads of the two type of forces are calculated with the load spectra. The results show that, the operation speed has effect on the loads of traction sets and brake devices. The effect of the curve radius of the track on the two type of forces is negligible. The vibrations of the brake devices lead to high frequent forces. The structural damage of the traction set is mainly caused by the traction forces and the vibrations have little contribution on its structural damage. The structural damage of the brake devices is caused by the vibrations and the brake loads. It is helpful of the investigation to design the structure of traction sets and brake devices and to study the structural damages of the high speed EMU.

Key words: high speed EMU, traction load, brake load, field measurement, load characteristics analysis, damage