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.     

Analysis of multi-layered thick-walled filament-wound hydrogen storage vessels

In this paper a three-dimensional elasticity analysis on multi-layered thick-walled filament-wound hydrogen storage vessels is outlined. An exact solution to stresses of the metal liner and each anisotropic layer is presented, based on Lekhnitskii's theory and the generalized plane strain assumption. The governing equation for determining the radial displacement of the hydrogen vessel is derived and the stresses in the cylindrical coordinates are then obtained. The matrix equation that determines the integration coefficients of the governing equation is formulated by considering the boundary and interface conditions. The normal and in-plane shear stresses and the twisting rate of the vessel are calculated for various thicknesses of the aluminum liner; the results are then compared to those presented by Xia et al. It is shown that the addition of the liner significantly reduces the stress magnitude of the hydrogen vessel; this stress magnitude decreases as the liner thickness increases. The results also revealed that the twisting effect is reduced by increasing the liner thickness. The ratio of hoop-to-axial stress is no longer a constant through the vessel wall and varies within the wall thickness. In addition, various combinations of anisotropic composites and isotropic liner materials are here examined to pinpoint preferable material combinations that lead to a lower equivalent stress level of the liner and higher strength reserve of the composite laminate.     

Experimental and analytical investigation of the cylindrical part of a metallic vessel reinforced by filament winding while submitted to internal pressure

In this work, we present an experimental and analytical investigation of a hydrogen storage vessel. This vessel is made of a carbon/epoxy envelope coated on a metal liner. In the theoretical part, an analytical model is proposed in which the laminate composite is assumed to be an anisotropic purely elastic material, whereas the liner is considered as an elasto-plastic material. The suggested analytical model provides an exact solution for stresses and strains on the cylindrical section of the vessel solution submitted to mechanical static loading. The aim of the experimental part is to validate the results of the theoretical model by manufacturing and testing some prototype vessels. Some analytical results are compared with the finite element solutions, a good correlation is observed.     

Reductions in cost and greenhouse gas emissions with new bulk ship designs enabled by the Panama Canal expansion

Historically, fuel costs have been small compared with the fixed costs of a bulk vessel, its crewing and management. Today, however, fuel accounts for more than 50% of the total costs. In combination with an introduction of stricter energy efficiency requirements for new vessels, this might make design improvement a necessity for all new bulk vessels. This is in contradiction to traditional bulk vessel designs, where the focus has been on maximizing the cargo-carrying capacity at the lowest possible building cost and not on minimizing the energy consumption. Moreover, the Panama Canal has historically been an important design criterion, while the new canal locks from 2014 will significantly increase the maximum size of vessels that can pass. The present paper provides an assessment of cost and emissions as a function of alternative bulk vessel designs with focus on a vessel's beam, length and hull slenderness, expressed by the length displacement ratio for three fuel price scenarios. The result shows that with slenderer hull forms the emissions drop. With today's fuel price of 600 USD per ton of fuel, emissions can thus be reduced by up to 15–25% at a negative abatement cost.     

COMPUTATION OF TRANSIENT THERMAL STRESSES IN ELASTIC-PLASTIC TUBES: EFFECT OF COUPLING AND TEMPERATURE-DEPENDENT PHYSICAL PROPERTIES

The objective of this study is to obtain the transient solution of the thermoelastic-plastic deformation of internal heat-generating tubes by considering the thermomechanical coupling effect and the temperature-dependent physical properties of the material. The previously developed steady-state model describing the elastic-plastic behavior of the tubes is modified to obtain the transient solution. The propagation of the elastic-plastic interface for a given heat load is obtained; and the corresponding stress, displacement, and plastic strain components are computed. The effect of the coupling is investigated using three different engineering materials, namely, steel, aluminum, and magnesium; and it has been found to be negligible. On the other hand, the temperature dependence of the mechanical and thermal properties affects the computed profiles significantly.     

Fatigue life evaluation of high pressure hydrogen storage vessel

By combining the micromechanics and continuum damage mechanics, a theoretical model is proposed to perform the fatigue evaluation of high pressure hydrogen storage vessel under cyclic internal pressure, which concentrates on the fatigue properties of the aluminum liner. Results show that the fatigue lifetime of vessel relates to the finite element mesh size, crack density and ratio in an element, cyclic loading amplitude and stress status at the liner. Effects of the mesh size and crack density on the fatigue lifetime of vessel are discussed. In addition, numerical results are also compared with those by experiments.     

Experimental study of the stacking sequence effect on polymer/composite multi-layers submitted to thermomechanical cyclic loadings

Fast filling of hydrogen pressure tank leads to thermomechanical stresses in vessel structure. In this paper, the aim is to study the thermomechanical behaviour of the material used in the vessel structure. Flat coupons made of the same constituents as the hydrogen tank materials and with different stacking sequences have been tested under quasi-static tensile tests and fatigue. Three types of fatigue tests have been performed in order to understand damage mechanisms due to interactions between thermal and mechanical stresses: thermomechanical fatigue, 1 Hz mechanical fatigue and mechanical fatigue with a constant stress level stage. Damage development has been followed by acoustic emission and microscopic observations. Results show that, whatever the applied loading, there is a significant influence of the stacking sequence of the composite part. Moreover, the comparison of the material response to the different types of fatigue has revealed the harmful role of coupled temperature/mechanical cyclic stresses.     

Elastic-Plastic Stresses and Strains in Thin Discs with Temperature-Dependent Properties Subject to Thermal Loading

The von Mises yield criterion and its associated flow rule are adopted to provide the exact analytic solution for the elastic-plastic stress and strain distributions within the discs with temperature-dependent properties subject to thermal loading by a uniform temperature field and subsequent unloading. This article examines the effect of temperature-dependent properties on the size of the plastic zone. Qualitative features of the solution are emphasized. The primary objective of the article is to provide a benchmark problem having the exact analytic solution for justifying the possibility to neglect or the necessity to account for temperature-dependency of thermomechanical properties in analysis of elastic-plastic discs under plane stress conditions.     

MIXED VARIATIONAL FORMULA FOR THE THERMAL BENDING OF LAMINATED PLATES

A mixed variational formula based upon Hamilton's principle is obtained including the thermomechanical action of composite structures. Based on this formula, a linear thermomechanical composite plate model is presented. The model accounts for a Mindlin-type assumption on displacements and stresses in consistence with general surface conditions. So the rationale for the shear correction factor is obviated. Governing equations of orthotropic composite plates subjected to thermal and mechanical loading are derived. A wide variety of results are presented. The validity of the model is demonstrated by comparison with solutions available in the literature. The present results are in good agreement with the results of others.     

Modelling and simulation of a zero-emission hybrid power plant for a domestic ferry

This paper presents a simulation tool for marine hybrid power-plants equipped with polymer exchange membrane fuel cells and batteries. The virtual model, through the combination of operational data and dynamically modelled subsystems, can simulate power-plants of different sizes and configurations, in order to analyze the response of different energy management strategies. The model aims to replicate the realistic behavior of the components included in the vessel's grid, to asses if the hardware selected by the user is capable of delivering the power set-point requested by the energy management system. The model can then be used to optimize key factors such as hydrogen consumption. The case study presented in the paper demonstrates how the model can be used for the evaluation of a retrofitting operation, replacing a diesel electric power-plant with fuel cells and batteries. The vessel taken into consideration is a domestic ferry, operating car and passenger transport in Denmark. The vessel is outfitted with a diesel electric plant and an alternative hybrid power-plant is proposed. The hybrid configuration is tested using the model in a discrete time-domain.     

THERMAL STRESSES IN ELASTIC-PLASTIC TUBES WITH TEMPERATURE-DEPENDENT MECHANICAL AND THERMAL PROPERTIES

The thermoelastic-plastic deformations of internal heat-generating tubes are investigated by considering the temperature dependence of the thermal conductivity coefficient, Young's modulus, the coefficient of thermal expansion, and the yield limit of the material. A model describing the elastic-plastic behavior of the tube is developed. The model consists of a system of two second-order ordinary differential equations and a first-order ordinary differential equation involving nonlinear temperature-dependent coefficients. The computer solution of the model is obtained, and the results are compared with the analytical solution that assumes constant thermomechanical properties. It is found that the difference between the two solutions becomes significant in the regions of high temperatures.     

AEROTHERMOELASTIC PHENOMENA OF AEROSPACE AND COMPOSITE STRUCTURES

The thermal postbuckling and aerodynamic-thermal load analysis of cylindrical laminated panels has been performed using the finite element method. To consider large deflections due to thermomechanical loads, the von Karman nonlinear displacement-strain relationships based on layerwise theory are applied. The cylindrical arc-length method is used to take account of the snapping phenomena. The panel flutter analysis of cylindrical panels subject to thermal stresses is carried out using Hans Krumhaar's supersonic piston theory. For the enhancement of the postbuckling and panel flutter behavior subjected to thermal load, the shape memory alloy hybrid composite (SMAHC) panel is investigated.     

Analysis of multilayered carbon fiber winding of cryo-compressed hydrogen storage vessel

In order to meet the hydrogen storage requirements of fuel cell vehicles, and improve the storage density of hydrogen, a cryo-compressed hydrogen storage method was proposed. The performance of cryo-compressed hydrogen storage vessel was analyzed in this paper. Based on the classical laminate theory and heat transfer solution, the stress and displacement of carbon fiber were precisely calculated to guarantee the cryo-compressed vessel severing in the cryogenic condition. Subsequently, the Tsai-Wu failure criterion was used to judge the failure of carbon fiber reinforced plastics layers. The stacking sequence, winding angle, comparison of the vessel's performance at room temperature and low temperature were conducted. The numerical results showed that the properties of storage vessel decreased at cryogenic condition, and the thickness of carbon fiber at cryogenic temperature at least increased by 47.06% than that at the room temperature. Mainly influence of low temperature on the cryo-compressed vessel were concentrated on the hoop stress of helical winding and the axial stress of hoop winding. For the vessel design, it is achievable to increase these two parts by using higher strength resin materials.     

Thermal and Stress Analysis of Glazing in Fires and Glass Fracture Modeling with a Probabilistic Approach

The aim of the study is to predict the thermal and stress behavior of a framed glass subjected to typical fire conditions, and the initial glass fracture time and locations using a probabilistic approach as an alternative to Pagni's deterministic criterion. Thermal stresses in glass have been little researched. The probabilistic approach has the advantage of taking into account some uncertainties such as the edge conditions. The model employed is based on stress and conduction heat transfer models, a spectral discrete ordinates radiation model, and a failure probability model. Some results of its verification and applications are reported here.     

THERMAL TEMPERING SIMULATION OF GLASS PLATES: INNER AND EDGE RESIDUAL STRESSES

Narayanaswamy's model is used to describe the thermomechanical behavior of glass. It includes both stress relaxation (to take into account the viscous aspect of glass) and structural relaxation (to take into account the structure state of glass). The necessary thermal and mechanical characteristics are given for the float soda-lime silicate glass.

The thermal tempering of thin glass plates is simulated. Transient and residual stresses are given for the inner part of the plate. Computational results are compared with experimental results of previous works. This comparison validates Naranaswamy's model associated with material characteristics given previously.

The edge effect (variation of stresses close to the edges) is described for thin plates. The thermal tempering of thick plates is simulated, and computational results are validated with optical measurements and a fractographic analysis.     

Bursting problem of filament wound composite pressure vessels

Using the nonlinear finite element method, we have calculated the stresses and the bursting pressure of filament wound solid-rocket motor cases which are a kind of composite pressure vessel. Maximum stress failure criteria and a stiffness-degradation model were introduced to the failure analysis. The effects of material performance and geometrical nonlinearity on the relative loading capacity of the dome were studied. For the model I case with skirts, relative loading capacity of the dome increased when geometrical nonlinearity was considered and composite material of higher strength was used. But for the model II case without skirts, the conclusion obtained was contrary to that for the model I case.     

Evaluation of modeling techniques for a type III hydrogen pressure vessel (70 MPa) made of an aluminum liner and a thick carbon/epoxy composite for fuel cell vehicles

Stress distributions in the composite layers of a Type III hydrogen pressure vessel composed of a thin aluminum liner (5 mm) and a thick composite laminate (45 mm) were calculated by using three different modeling techniques. The results were analyzed and compared with the plausible stress distribution calculated by a full ply-based modeling technique. A laminate-based modeling technique underestimated the generated stresses especially at the border between the cylinder and dome parts. A hybrid modeling technique combining a laminate-based modeling for the dome part with a ply-based modeling for the cylinder part was also tried, but it overestimated the generated stresses at the border. In order for the ply-based modeling technique to carry out precise analysis, a fiber trajectory function for the dome part was derived and the composite thickness variation was also considered.     

Elastoplastic analysis of FGM plate with a central cutout of various shapes under thermomechanical loading

The present work aims to study the elastoplastic buckling, postbuckling, and failure behavior of perforated Ni/Al₂O₃ functionally graded material (FGM) plate with various shaped cutouts (i.e., circular, square, diamond, and elliptical) of various sizes under thermomechanical loading conditions using finite element method (FEM). The nonlinear FEM formulation is based on the first-order shear deformation theory and von Kármán’s nonlinear kinematics in which the material nonlinearity is incorporated. The nonlinear temperature-dependent thermoelastic material properties of FGM plate are varied in the thickness direction by controlling the volume fraction of the constituent materials (i.e., ceramic and metal) as per a power law, and Mori–Tanaka homogenization scheme is applied to evaluate the properties at a particular thickness coordinate of FGM. In accordance with the Tamura–Tomota–Ozawa model (TTO model), the ceramic phase of FGM is considered to be elastic, whereas the metal phase is assumed to be elastoplastic. Further, the elastoplastic analysis of FGM is assumed to follow J₂ plasticity with isotropic hardening. After validating the present formulation with the results available in the literature, various numerical studies are conducted to examine the effects of material inhomogeneity, thermal loading, cutout shape, and size on the elastoplastic buckling, postbuckling, and failure behavior of perforated FGM plate. It is observed that for smaller cutout sizes, the FGM plate with square shape cutout possesses maximum value of ultimate failure load; however, for larger cutout size, the FGM plate with diamond cutout depicts highest ultimate failure load. Furthermore, for all cutout shapes, the ultimate failure load of FGM plate decreases with an increase in cutout size. It is also revealed that irrespective of shape and size of cutout, the material plastic flow has considerable effect on postbuckling path of FGM plate, and under thermomechanical loading conditions, the FGM plate shows destabilizing response after the point of maximum postbuckling strength.     

Study on the failure behavior of the current interrupt device of lithium-ion battery considering the effect of creep

The working condition of the CID (current interrupt device) has an important impact on the safety of the prismatic lithium-ion batteries. One of the important factors that causes the failure of the prismatic power battery is the overturning of CID due to material creep. The tensile and creep tests of the MFX2 aluminum alloy which is the material of CID were designed. Based on the experimental data the isotropic hardening multilinear elastic-plastic constitution and creep constitution at the battery working temperature were established. The constitutions were also verified by the notch test. The finite element model of the CID and the cap was established to analyze the effect of creep on the failure behavior of the CID throughout life. The simulation tests in the constant temperature and constant load of CID is designed. The simulation results showed that the constitution characterizes the basic mechanical properties of the CID reasonably. During the life of the CID, the creep behavior would go through the fast stage firstly and then fall into the slow steady-state stage. The creep effect of the material would cause the CID to overturn in advance, overturning pressure would be reduced, the life of the power battery would also be reduced.