The dynamic response of the double drive shafts, as the core component of the dual-coupled axial piston pump, affects the stability and reliability of the pump. The double drive shafts bear complex dynamic loads accompanied by a certain degree of vibration during the transmission of power, which results in abnormal contact between the double drive shafts and the bearing, as well as between it and the splined coupler, leading to increased wear. In this study, addressing the fatigue failure issue of the double drive shafts in the dual-coupled axial piston pump, a rigid-flexible coupling dynamic model of the dual-coupled axial piston pump is established. The stress and strain conditions of the double drive shafts under various load ratios are analysed, along with the dynamic characteristics between the drive shaft and the barrel block, as well as between it and the spline sleeve in both time and frequency domains, and the variation pattern of the vibration displacement of the double drive shafts. Additionally, the fatigue damage of the double drive shafts under various load ratios is analysed using the fatigue cumulative damage model. The results show that under various load ratios, obvious stress and strain concentrations occur in the neck near the bearing connection and the spline sleeve connection. The safety factor of the double drive shafts is higher than 1.5 in the obtained safety load range. The contact force between the double drive shafts and the barrel block is mainly influenced by the reciprocating motion of the pistons, while the contact force between the double drive shafts and the spline sleeve is affected by the synergistic effect of the reciprocating motion of the piston and the rotation of the drive shaft. Furthermore, the increase in the rear pump load pressure results in irregular trends in the vibration displacement of the double drive shafts, as well as superimposed fatigue damage to the front shaft. This study provides a reference for fatigue failure prevention, noise reduction, and vibration damping of the double drive shafts under various load ratios.
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