Study on the tensile performance degradation of bolt-ball joints after bolt-thread corrosion

Bolt-ball joints, which have been used in corrosive environments for a long time, are prone to corrosion problems, particularly in the contact area between the bolt and the ball, posing a threat to the overall structural safety. This paper established a refined finite element model of bolt-ball joints that considers the effects of boltthread corrosion and corrosion products using an integrated simulation method of 3D corrosion evolution and mechanical properties of steel building components. The reliability of the simulation method was verified through several tensile tests. Subsequently, the stress distribution and load-displacement curves of M20, M24, and M27 joints with varying degrees of corrosion were analyzed after tension. The results indicate that when the corrosion mass loss rate is less than 80%, the tensile failure mode of the joint is bolt rod yielding. However, when the mass loss rate of the thread reaches 80%, the failure mode is ball thread yielding. For joints with the same thread mass loss rate and section area, the bearing capacity degradation increases as the bolt diameter increases. Additionally, for joints with different cross-sectional areas of threads, the bearing capacity degradation rate is higher when the cross-sectional area of the thread is smaller. Finally, a degradation formula for the tensile bearing capacity, taking into account the corrosion mass loss rate and bolt diameter, was proposed through regression analysis. This formula serves as a technical reference for the safety evaluation of corroded bolt-ball joints and similar joints.