Degradation reliability modeling for ball screws subject to fatigue elastic failure mode

Ball screws have been receiving increasing attention in the aerospace and military industry for their high reliability and high positioning accuracy. Under such extreme working conditions, ball screws are required to bear heavy loads in a short time, where they are mainly subject to fatigue elastic failure mode. Traditional reliability modeling methods based on the fatigue pitting failure mode are not suitable any more. However, reliability based on fatigue elastic failure in ball screws has not been investigated yet. To this end, we first established a degradation mechanism model for the fatigue elastic of ball screws. Subsequently, we proposed the degradation reliability model for ball screws, along with a novel Expectation Maximization method for parameter estimation. Additionally, we proposed a novel test method for the fatigue elastic life for ball screws utilizing a designed test bench. The mean curve for the degradation model almost exhibited a relative error less than 5%, confirming the validity of the proposed model. Lastly, we conducted a sensitivity analysis of structural parameters on fatigue elasticity, finding that the helix angle significantly influences the rated elastic life, while the ball diameter has a minimal effect. These findings contribute valuable insights for reliability evaluation and reliability design for ball screws under extreme working conditions.