Reliability research of impact fatigue life for pump´s valve covers

Based on the mathematical model of the pump valve-ball´s movement, the maximum impact stress of pump´s valve covers is studied using ANSYS/LS_DYNA and a regression model of impact stress is developed. Combining the S-N curve of material with linear cumulative damage law, considering various factors that influence machine parts´ fatigue life, the calculation model of impact fatigue life for pump´s valve covers is established. By applying the reliability theory to the analysis of the life distribution for pump´s valve covers, the reliability predication model of impact fatigue life for covers is presented. Taking into account the uncertainty of mechanical properties, the quality of machine parts, size structure and the impact speed of valve ball, the numerical solution of the model is obtained with the Monte Carlo method. The reliability simulation software of valve covers´ impact fatigue life has been developed. This software not only studies the motion law of oil-well pump valves, but also analyzes the impact of stroke and rate of pump, dynamic liquid level and pump depth on the speed of valve ball, valve cover´s life and reliability. Finally, some measures for increasing the fatigue reliability are explored.