Shakedown and failure of the threaded joints under low cyclic loading

Abstract

The initiation and propagation of fatigue cracks in threaded joints are under consideration. The low of growth of such cracks are described as well. The stress intensity factors K, are proposed in order to describe the failure process of bolted joints. The presented data show the fatigue process withins the elements the working conditions of which depend on the influence of other elements, have many specific features. The increase of pressing force and variable repeated loading of stud-bolt connections lead to the plastic deformation of certain zones of bolts. Due to such nonelastic deformation dangerous states may occur leading to deterioration of bolts. One of such states is characterised by a progressing accumulation of deformations resulting in the changes in the geometry of conctructive elements. The method of “additional load” has been used for the estimation of the bolt shakedown. The parameters in case of tensioning and bending. By using obtained theoretical and experimental results (at the normal and elevated temperatures) the assessment of thread joint safety was carried out in consideration to various limit states: initiate of crack, fatigue fracture and ductile failure.