An experimental study of localized bulging in inflated cylindrical tubes guided by newly emerged analytical results

Abstract

An experimental study is conducted on localized bulging of inflated latex rubber tubes of a range of wall thicknesses and tube lengths, guided by newly emerged analytical results. In the case when the tube has one free closed end that may or may not be subjected to a dead weight, the initiation pressure for localized bulging is determined by a bifurcation condition, and the propagation pressure is determined by Maxwell's equal-area rule. It is shown that after bulge initiation the pressure will decrease monotonically towards, but will never reach, the propagation pressure, and it is when the pressure is sufficiently close to this propagation pressure that rapid propagation of the bulge in the axial direction takes place. It is found that the experimentally observed initiation pressure is around 15% below the theoretical prediction, which is consistent with the fact that bulging initiation is a subcritical phenomenon and is therefore sensitive to imperfections. The experimentally observed propagation pressure is always very close to the theoretical prediction, which confirms the insensitivity of this pressure to imperfections and demonstrates the predictive power of the material model fitted from our own experiments on equibiaxial stretching. In the other case when the tube is first stretched and then fixed at both ends, bulge initiation takes place in the same manner as in the previous case, but the propagation pressure is no longer determined by Maxwell's equal-area rule. After bulge initiation the pressure will first decrease to a minimum and then rises slowly, and it is on the latter ascending path that the bulge starts to propagate rapidly in the axial direction. A semi-analytical method is proposed for the determination of the minimum pressure. Numerical simulations with the use of the software Abaqus are also conducted to verify the theoretical predictions.

Weakly nonlinear analysis of localized bulging of an inflated hyperelastic tube of arbitrary wall thickness

“…z = 0) can be determined by solving two algebraic equations whether it is the N or λ z that is fixed (Fu et al, 2008). In the case of fixed length, these principal stretches can be determined by using the iteration procedure explained in Wang et al (2019). Thus, in all three cases the amplitude diagrams can be obtained semi-analytically.…”

“…This result makes it possible to examine the effect of rotation (Wang et al, 2017b), fibre-reinforcement (Wang & Fu, 2018), and multi-layering (Liu et al, 2019;Ye et al, 2019) in a systematic manner. An experimental study guided by these newly emerged theoretical results has also been conducted (Wang et al, 2019).…”

Fate of a bulge in an inflated hyperelastic tube: theory and experiment

“…Pressurized cylindrical vessels are found in many technological applications: in oil and gas pipes [1,16], nuclear plants and also blood vessels, for example. The stability of pressure vessels under combined loading is an active area of research despite its long history [2,14,17,18], not all of which can be surveyed here as the literature spans at least four decades. Pertinent results are recalled here.…”

“…For instance, it is shown by analysis [30] that the localized bulge formation with fixed–free BCs is not possible for fibre-reinforced tubes. Furthermore, the bifurcation conditions associated with the bulge have been verified by experiment for both fixed–fixed and fixed–free BCs [14]. A comparison between the weakly nonlinear model and membrane theory can be found in [15].…”

“…A limited number of experiments did observe buckling [33,34] but did not investigate the influence of buckling on rupture. It is possible, in applications such as both an aneurysm or supported pipes, to observe a BC where both ends are held fixed [14]. This can be accomplished, for example, by holding a tube between spatially fixed jaws of a material testing system to impose a predefined axial stretch.…”