Abstract
The behavior of bolted joints tightened with steel bolts under the impact tensile load are studied experimentally, changing the mechanical properties classes and length of straightportion of reduced diameter of bolts. The effects of the initial tightening force on the steel bolt strength is clarified through experiment. The result obtained are as follows : (1) As the initial tightening force is increased, the maximum stress and Φ-value (additional force/external impact load) decrease. (2) Without the initial tightening force, the higher the property class, the higher the maximum impact load. (3) Regardless of the property class, increasing the initial tightening force results in lowered impact absorbed energy. (4) Load capacity of the joints tightened in yield point is a little lower than that in elastic region. (5) Permitting the decrease of initial tightening force by 10%, the allowable load is about 85% of the yield strength of the bolt. (6) The allowable load estimated in the joint (load cell) whose stiffness is lower than actual condition is in safety zone.
