Experimental Study On Bending Fatigue Strength Of Bolt Fastener

The axle-mounted brake discs in the high-speed train axle system are indirectly connected to the axles by high-strength bolts.The bending load of the bolt during the operation process has occurred,which has caused the failure of the brake disc bolt to break.Therefore,it is of great significance to study the bending fatigue strength of bolts to improve the fatigue test system and improve the safety of China's EMU operation.In this paper,the measured data of China's high-speed train EMUs are selected,and the bolt bending fatigue strength parameters are determined by bolt bending fatigue test to evaluate the reliability of the brake disc bolts.Firstly,Analyzing the actual working conditions of the brake disc bolts during loading with the ABAQUS simulation results,a bolt test tooling that can realize pure bending loading based on the MTS fatigue testing machine is designed.In order to ensure the durability of the tooling,some materials are made of 40Cr then heat treated.The bolts used in the test were M14x140 10.9 high-strength bolts,and three faces were test with strain gauges and connected to the EDAQ dynamic collector for strain data collection.The equipment used in the test was the MTS810 fatigue tester,which was loaded by displacement.Experiments show that the strain waveforms of the measuring points are sinusoids,and their amplitude decreases with increasing distance from the head of the bolt.The experimental data is processed based on ncode software to obtain the stress amplitude and cycle number of different measuring faces.The stress data indicates that the bending stress is more than ten times of the tensile stress;the stress amplitude of different measuring faces of the same bolt is negatively correlated with the distance from the head of the bolt,and the relational expression satisfies the theoretical equation of the beam.Calculating the stress at the bolt break,and draw the S-N curve of the bolt bending fatigue in combination with the number of cycles to determine the bending fatigue strength of the brake disc bolt.The obtained parameters are used for the measured data of the high-speed train line,and the reliability of the brake disc bolt is evaluated based on the ncode software.48 pictures,15 tables,41 references.