Research on the fatigue strength of the installation bracket of the platform detection device under complex environments

Abstract

The platform detection device is an important device for assisting the train to stop at the station. It is connected to the car body through the mounting bracket, and the entire structure bears both aerodynamic loads from the air and vibration loads from the car body. The bracket, as a cantilever structure, has the risk of cracking. Once the bracket breaks, it will affect the train’s entry into the station and even endanger traffic safety. This paper combines experiments and simulations to study the fatigue strength of the mounting bracket of a platform detection device installed on a certain type of EMU. Firstly, modal and line tests are carried out on the bracket, using the rainflow counting method, referring to IIW standard, and calculating fatigue life of stress measurement points according to Miner cumulative damage theory. It is found that the bracket has not reached the design requirement of 9 million kilometers, and it is found that it is because the first-order mode of the bracket is excited by analyzing test data. Then, based on the experimental modal information, an accurate finite element model is established, and IRF is obtained by using finite element simulation with measured aerodynamic and vibration loads as input. The stress at the measurement point is calculated by using the time-domain convolution integral method, and the test results are reproduced to verify the accuracy of the simulation method. Finally, structural optimization is carried out on the bracket structure, and fatigue life prediction is carried out on the new structure using verified simulation methods. The fatigue life of the new structure is 129 billion kilometers, which meets the design requirements.