ANALYTICAL STUDY ON THREAD SHAPE OF HIGH-STRENGTH BOLTS AIMED AT IMPROVING DELAYED FRACTURE RESISTANCE

For making bolted connections convenient and compact, higher bolt tension of the high-strength bolt is required. Therefore, the key point is prevention from the delayed fracture, which the tensile strength of the bolt is over 1,000N/mm2. The delayed fracture is easy to happen in a high stress and a large plastic strain location. FEM analysis was executed to compare stress concentration and plastic strain on the location of thread roots between new thread shape and usual thread shape. This paper deals with the FEM analysis to propose the improved thread shape.