Bolt Pull-Out Failure Analysis and Structural Optimisation for Heavy-Duty Rod End Bearings via a Combined Numerical-Analytical Method

Rod-end spherical bearings are widely used in heavy machinery, wind power, and transportation. Their bolted connections directly determine structural safety but are prone to pull-out failure under maximum articulation angle and heavy load. This study employs finite element (FE) simulation to elucidate the failure mechanism and, combined with Timoshenko beam theory, systematically analyses the effects of end cap parameters (size, height, modulus) on bolt head lateral force and bending moment. Results show that two-piece end caps induce abnormal contact and severe stress concentration under combined lateral and axial loads. A spigot design with optimised bolt number and contact geometry is proposed, reducing the additional bending moment from 1.882×104 N·mm to 2.193×103 N·mm and lateral load from 8.236×105 N to 7.092×104 N (over 88% reduction), bringing stress within a safe range. Although the numerical analysis was not directly verified experimentally, the experimental confirmation of the design’s functionality supports the optimisation. This study clarifies the pull-out mechanism and provides insight for anti-pull-out connections under high lateral forces.