Evaluation of mechanical behavior of new type bellows with two-directionalconvolutions

Bellows are widely used as the element of expansion joint in various piping systems. Piping systems for industrial plants often suffer excessive defor mations or displacements caused by heat expansion, vibration, nonuniform su bsidence of ground, etc. Bellows have the function to absorb regular or irr egular expansion and contraction in such piping systems. Conventional bello ws, however, have difficulties such as the instability of deformations unde r cyclic loadings, and the inability to absorb torsional deformations. In o rder to solve these problems, a new type of bellows, so-called "double conv olution bellows", were proposed. This new type of bellows has convolutions in two directions: the first convolutions in the longitudinal direction are the same as the conventional bellows; and the second convolutions are adde d in the lateral direction. This paper presents a study on the mechanical b ehaviors of the new type bellows and conventional bellows to examine the de formation behaviors under repeated axial loading, internal pressurizing and torsional loadings, and the results show an improvement in thickness distr ibution, instability and torsional flexibility. (C) 2000 Elsevier Science S .A. All rights reserved.