Stress and Function Analysis of Drive Shaft Components

Drive shaft components are among the key parts of mechanical transmission systems in diesel locomotives. The drive shaft of the DF4 locomotive is designed to transmit power output from the diesel engine to the hydrostatic transmission gearbox, driving two hydrostatic pumps to generate high-pressure hydrostatic oil. Meanwhile, in accordance with the temperature requirements of oil and cooling water, it drives and regulates the operation of hydrostatic motors to cool high-temperature and low-temperature cooling water.

It can be seen that the drive shaft is mainly subjected to torsional torque. The magnitude of this torque varies with the rotational speed of the diesel engine and increases with the rise in its output power. Therefore, the drive shaft bears alternating torsional torque. After long-term service, cracks will inevitably initiate at weak points. If not detected in a timely manner, stress concentration will occur at the cracked area, resulting in a drive shaft rupture failure within a short period.

The base materials of the hollow shaft and splined shaft in the drive shaft are 40# carbon steel and 45# carbon steel respectively. 45# steel is a medium carbon steel, and the weldability of carbon steel changes significantly with increasing carbon content. Higher carbon content and greater workpiece thickness lead to the formation of low-plasticity hardened structures in the heat-affected zone under the welding thermal cycle. This brittle state, combined with considerable shrinkage stress, can cause cold cracks in the heat-affected zone [1]. According to the carbon equivalent formula of the International Institute of Welding (IIW), the carbon equivalent Ceq of 45# steel is calculated as 0.67%. Generally, when this value exceeds 0.60%, the material exhibits extremely high crack sensitivity. Strict welding procedures must be adopted to prevent cracking.

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