ABSTRACT
Fatigue resistance of rectangular sealing beads of various width and depth were experimentally investigated to support sealed joint designs, in particular, how to decide dimensions of depth of them reasonably. First, fatigue tests were carried out for a polysulfide sealant at three levels of amplitude of joint movement, ± 10%, ± 30% and ± 50% of initial joint width. Beads of shallow cross-section buckled like an arch at joint contraction, while deep ones bulged like a barrel. The positions where cracks appeared closely related to the compressed shape during fatigue operation; Cracks mostly appeared in the middle of bottom surface of beads when buckled, and at the comers on both exterior and bottom surfaces when bulged. It was made clear through photo-elastic analysis that the positions of crack initiation correspond with the area in beads where tensile and compressive stresses appeared repeatedly in response to joint movement. Fatigue resistance of sealing beads was not simply related to their proportions of depth(D)/width(W), but much affected by depth itself. The number of cycles to crack initiation(N) can be expressed by log N = − Alog(Dn/W)+B, where A and B are constants. Finally, additional fatigue tests were carried out to determine whether the experimental equation can be applied to other sealants.
