ANALYZIS OF THE FATIGUE LIFE OF HYDROGEN HIGH PRESSURE TANKS
Nevertheless, in order to respond to the economic a nd environmental criteria, hydrogen production and storage have to be improved. This wo rk focuses on gaseous storage under high pressure (700 bar) using a type III vessel (figure 1) that is to say composed of a metal liner – which prevents gas diffusion – and of a composite l aminate wrapped by filament winding – which is used as a mechanical strengthening piece. Th problem with this type of high pressure vessel is the early explosion when it is t ested to cyclic pressures. To solve this problem, the components – liner and composite – hav e to be well-proportioned.
Optimal design of a Type 3 hydrogen vessel: Part I—Analytic modelling of the cylindrical section
The present paper aims to study the cylindrical section of a Type 3 high-pressure hydrogen storage vessel, combining an aluminium liner which prevents gas diffusion and an overwrapped composite devoted to reinforce the structure. Today, this technique is widely used but still requires consistent time investments whenever a competitive solution, involving to definitely increase weight efficiency, is needed. The laminate composite is assumed to be an elasto-damage material whereas the liner behaves as an elasto-plastic material. Based on the classical laminate theory and on Hill's criterion to take into account the anisotropic plastic flow of the liner, the model provides an exact solution for stresses and strains on the cylindrical section of the vessel under thermomechanical static loading. Part I focuses on the theoretical background. The effect of the stacking sequence on the gap occurrence, on the residual stress magnitude and on the structure stiffness may then be investigated. This will be done and be compared with results of experiments which are carried out on prototypes in the second part of this paper before an optimization is performed.
The influence of hemodynamic forces on biomarkers in the walls of elastase-induced aneurysms in rabbits
IntroductionBiological and biophysical factors have been shown to play an important role in the initiation, progression, and rupture of intracranial aneurysms. The purpose of this study was to evaluate the association between hemodynamic forces and markers of vascular remodeling in elastase-induced saccular aneurysms in rabbits.MethodsElastase-induced aneurysms were created at the origin of the right common carotid artery in rabbits. Hemodynamic parameters were estimated using computational fluid dynamic simulations based on 3-D-reconstructed models of the vasculature. Expression of matrix metalloproteinases (MMPs), their inhibitors (TIMPs) and markers of vascular remodeling were measured in different spatial regions within the aneurysms.ResultsAltered expression of biological markers relative to controls was correlated with the locations of subnormal time-averaged wall shear stress (WSS) but not with the magnitude of pressure. In the aneurysms, WSS was low and expression of biological markers was significantly altered in a time-dependent fashion. At 2 weeks, an upregulation of active-MMP-2, downregulation of TIMP-1 and TIMP-2, and intact endothelium were found in aneurysm cavities. However, by 12 weeks, endothelial cells were absent or scattered, and levels of pro- and active-MMP-2 were not different from those in control arteries, but pro-MMP-9 and both TIMPs were upregulated.ConclusionThese results reveal a strong, spatially localized correlation between diminished WSS and differential expression of biological markers of vascular remodeling in elastase-induced saccular aneurysms. The ability of the wall to function and maintain a healthy endothelium in a low shear environment appears to be significantly impaired by chronic exposure to low WSS.