Hygrothermoelastic response in the bending analysis of elliptic plate due to hygrothermal loading

Abstract

This study investigates the theoretical outline to couple both classical Fourier’s and Fick’s laws to frame a new model of two-temperature hygrothermoelastic diffusion theory for a non-simple rigid material. Based on hygrothermoelasticity method, a system of linearly coupled partial differential equations for the thermal and moisture diffusion for the case of a non-simple medium is established. The transient response using the decoupled technique of a multilayered elliptic plate perpendicular to the axial axis, subjected to hygrothermal loading is considered, to derive closed-form expressions for temperature, moisture, deflection, bending moments, and hygrothermal stresses. The solutions to the governing coupled equations and its boundary conditions are solved by employing a new integral transform technique. The small deflection equation is found and utilized to preserve the intensities of bending moments and stresses, involving the Mathieu functions and its derivatives. Moreover, the elliptical region can be degenerated into a circular part by applying limitations. Numerical results of the transient response of hygrothermoelastic fields are established graphically for the better understanding the underlying elliptic structure, improved understanding of its relationship to circular profile, and better estimates of the effect of the associated hygrothermoelastic responses.     

Effect of Co loading on the hydrogen storage characteristics of hollow glass microspheres (HGMs)

The use of hydrogen as a fuel either direct combustion in an IC engine or for power generation in fuel cells continues to be a topic of significant interest. Developing and popularizing fuel cells for vehicular or other stationary applications depends upon the availability of safe and reliable hydrogen storage method. The greatest challenge as of now in this regard is the production of a light weight, nontoxic and easily transportable material which can store hydrogen. World-wide research is being conducted on developing newer materials for hydrogen storage. Hollow glass microspheres (HGMs) can be considered to be a potential hydrogen carrier which can store and deliver hydrogen for energy release applications. In this paper, we are reporting the preparation and characterization of cobalt loaded HGMs from amber glass powder for hydrogen storage applications. The feed glass powder with different percentage of cobalt loading was prepared by soaking and drying the feed glass powder in required amount of cobalt nitrate hexahydrate solution. Further, the dried feed glass powder was flame spheroidised to get cobalt loaded HGMs. Characterizations of all the HGMs samples were done using SEM, FTIR and XRD techniques. Hydrogen adsorptions on all the samples were done for 10 bar pressure at room temperature and 200 °C for 5 h. The results showed that the hydrogen adsorption capacity on these samples increased with increase in cobalt wt% from 0.2 to 2.0%. The hydrogen storage capacity of HACo2 was found to 2.32 wt% for 10 bar pressure at 200 °C.     

Pressure control strategy to extend the loading range of an alkaline electrolysis system

Alkaline electrolysis (AEL) is the most mature electrolysis technology and is widely used in large-scale power-to-gas scenarios. However, the loading range of AEL system is restricted by the minimum load, 10%–40% in general, which prevents system operation during low-load periods. This minimum load is caused by the flammable mixture formed by the impurity crossover and is related to operation conditions such as current and pressure. In this paper, we propose a novel pressure control strategy to extend the loading range of an AEL system by reducing the system pressure at low-load periods while also maximizing the system efficiency. A dynamic impurity accumulation model is established illustrating the flexibility limitation mechanism of the AEL system. Two pressure controllers are designed based on the steady-state and dynamic impurity accumulation model, including an operation curve tracking controller (OCT) and a model predictive controller (MPC). In the case study, both controllers achieve satisfying results under the peak shaving scenario, with an extension of the AEL system's minimum load from 27.5% by the traditional constant pressure controller to 10.5% by the OCT controller and 10% by the MPC controller. This pressure control strategy reduces the electricity abandonment and improves the system economy significantly.     

On the difference of fatigue strengths from rotating bending,four-point bending,and cantilever bending tests

Comparisons of piping fatigue data demonstrate that the fatigue strength from rotating bending tests is lower than that from cantilever and four-point bending tests, especially in the low-cycle fatigue life range. The lower strength from the rotating bending test is generally believed to result from the fact that in this test all the points on the piping surface are subjected to the maximum stress range. Consequently, the weakest point in the specimen always initiates and causes failure. On the contrary, in cantilever and four-point bending tests, the maximum stress range occurs only at the top and bottom extreme fibers, which may not contain the weakest point in the specimen. Hence, the pipes in rotating bending tests usually fail earlier in comparison with the other two tests. Finite element analyses for the three tests revealed another and more compelling reason for the lower fatigue strength from the rotating bending test. The results demonstrated that, for the same prescribed bending moment range, the inelastic strain range in rotating bending is higher than the ranges in four-point and cantilever bending tests. Experimental data also demonstrate a similar trend. The new observation suggests that fatigue data from these three tests should be analyzed or compared in terms of strain range, instead of nominal stress range.     

Effects of nonlinear hygrothermomechanical loading on bending of FGM rectangular plates resting on two-parameter elastic foundation using four-unknown plate theory

In the present study, a simple four-unknown exponential shear deformation theory is developed for the bending of functionally graded material (FGM) rectangular plates resting on two-parameter elastic foundation and subjected to nonlinear hygrothermomechanical loading. The elastic properties, coefficient of thermal expansion, and coefficient of moisture expansion of the plate are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of volume fractions of material constituents. Unlike first-order and other higher-order plate theories, the present theory has four independent unknowns. The in-plane displacement field of the present theory uses exponential functions in terms of thickness co-ordinate for calculating out-of-plane shearing strains. The transverse displacement includes bending and shear components. The principle of virtual displacement is employed to derive the governing equations and associated boundary conditions. A Navier solution technique is employed to obtained an analytical solutions. The elastic foundation is modelled as two-parameter Winkler–Pasternak foundation. The numerical results obtained are compared with previously published results wherever possible to prove the efficacy and accuracy of the present theory. The effects of stiffness and gradient index of the foundation on the hygrothermomechanical responses of the plates are discussed.     

Development of new analytical solutions for elastic thermal stress components in a hollow cylinder under sinusoidal transient thermal loading

For the analysis of high-cycle thermal fatigue due to striping (such as has been observed due to turbulence at mixing tees of class 1–2–3 piping of nuclear power reactors) it can be necessary to consider the time-dependent temperature gradient within the pipe wall thickness rather than just at the surface. To address this, a set of analytical solutions with several new features has been developed for the temperature field and the associated elastic thermal stress distributions for a hollow circular cylinder subjected to sinusoidal transient thermal loading at the inner surface. The approach uses a finite Hankel transform and some properties of Bessel functions. The analytical predictions have been successfully benchmarked by comparison with results from finite element analysis, and also with some results of independent studies.     

Comparison of the thermal performances of single hollow and double hollow concrete slabs

This paper compares the thermal performances of single hollow (SHS) and double hollow concrete slabs (DHS) from three points of view: (i) the overall reduction in heat flux, (ii) load levelling and (iii) the phase difference. It is seen that, for the same total thickness of concrete (i) a DHS performs only slightly better than an SHS as far as the overall reduction in heat flux is concerned, (ii) for load levelling, a DHS is superior to an SHS, (iii) neither the SHS nor the DHS introduces any additional appreciable phase difference compared with a single concrete slab (SS).     

Effect of Pd loading in Pd-Pt bimetallic catalysts doped into hollow core mesoporous shell carbon on performance of proton exchange membrane fuel cells

A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells was synthesized by microwave irradiation using a hollow core mesoporous shell (HCMS) carbon as catalyst support that was prepared by template replication of core/shell spherical silica particles and two different carbon precursors. Pt/Pd percent weight ratios on carbon support were varied as 20/0, 15/5, 10/10, 5/15 to 0/20. As the average pore diameter of the carbon support was increased from 3.02 nm to 3.90 nm by changing the type of the carbon precursor, fuel cell performances of the HCMS carbon based Pd-Pt bimetallic catalysts were improved significantly.     

On nonlinear bending and instability of imperfect cylindrical tubes

In this paper, the nonlinear bending and instability of initial geometrical imperfect cylindrical tubes subjected to pure bending load are studied. The imperfection is assumed to be a small ovality expressed as Timoshenko initial noncircularity function. A set of new nonlinear differential equations is developed, through a virtual work principle with a Lagrange multiplier, and solved asymptotically by means of a perturbation method. The asymptotical expressions for a nonlinear moment–curvature relationship and a critical moment are obtained. The effect of the noncircularity on the bending and instability are examined. The results of numerical calculations are presented by curves and compared with available theoretical and experimental data.     

Fabrication of porous hollow glass microspheres

Porous hollow glass microspheres have many uses, including porosity enhancers for lead-acid batteries. A fast, facile and high yield synthetic method for fabricating porous hollow glass microspheres with diameters around 45-55 μm is demonstrated. The process involves shaking commercially available hollow glass microspheres in dilute hydrofluoric acid for 20 min. This process yielded two pore morphologies by using different commercially available starting materials; sponge-like submicron pores etched from S38 microspheres, and straight through micron pore etched from K25. Yields were 33% and 40%, respectively. The simplicity of the reported fabrication technique has the potential to be scaled up for large scale production.     

节能空心砖设计与使用

文章述说了空心砖节能的原理，指出空洞尺寸、方向与节能效果的关系以及设计使用空心砖让空发挥最大节能效果的相关原则。     

Fabrication and characterization of an anode-supported hollow fiber SOFC

In this study, an anode-supported hollow-fiber solid oxide fuel cell (SOFC) of diameter 1.7 mm has been successfully fabricated using the phase inversion and vacuum assisted coating techniques. The cell has a special structure consisting of a 12-μm-thick yttria-stabilized zirconia (YSZ) electrolyte film and a Ni-YSZ anode layer which has large finger-like pores on both sides of the hollow-fiber membrane. The hollow-fiber SOFC has an active electrode area of 0.63 cm² and generates maximum power densities of 124, 287 and 377 mW cm⁻² at 600, 700 and 800 °C, respectively, indicating that its use in applications requiring high power density is promising.     

Cross-sectional flattening of pipes subjected to bending

Pipes subjected to bending may fail by cross-sectional flattening due to a plastic hinge mechanism occurring at the mid-section. In this paper the relationship between the applied bending moment and the stresses and strains at the neutral axis is calculated, using a power law stress-strain relationship. As a tentative failure criterion, a critical local bending radius of the pipe wall was selected. It can be expected that failure by the flattening mechanism occurs in the medium range of wall thickness to pipe radius ratio. For smaller ratios buckling on the compressive side—and, for larger ratios, fracture on the tensile side—of the pipe is shown to be the failure mechanism.     

The interaction of pressure and bending on a dented pipe

Results are presented from an FE numerical study of the capacity of a dented pipe to withstand combined pressure and moment loading. The denting process was modelled with internal pressure applied at the design level. The pipe support was modelled by a saddle-type arrangement. The strength of the dented pipe was first assessed under pure bending, applied in such a way that the dent was either on the tension side or the compression side. The strength of the dented pipe was then assessed under internal pressure loading. Finally, the behaviour of the dented pipe under combined bending and pressure loading was assessed and interaction diagrams prepared.     

Compound cracks in pipes under combined bending and tension

Limit load and J-resistance curve solutions are developed for a compound crack in a pipe under combined tension and bending. The solution is based on a thick-walled cylinder assumption and the J solution can be applied with load-displacement data from one pipe test. Material resistance curves are developed for compound cracks in Type-304 stainless steel, Inconel 600 and A106 GrB base materials and a 304 stainless steel TIG weld. Tearing instability analyses are performed to assess the load-carrying capacity of pipes containing compound cracks and to evaluate nonconservatism associated with the use of C(T) specimen J-R data.     

Feasibility and optimization of the hollow optical fiber drawing process

The drawing process for the fabrication of a hollow optical fiber involves the flow of glass, which is largely heated by thermal radiation, in an inert gas environment. It is critical to maintain the central core, which can collapse if the thermal conditions are not properly imposed and controlled. This paper presents the analysis and simulation of this complicated process. A numerical model is developed, validated, and applied to simulate the hollow optical fiber drawing process under a wide range of boundary conditions, particularly draw speed, tension, and temperature. A feasible domain of the drawing process is identified to give the range of the drawing parameters for which the geometry of the fiber is maintained and collapse of the core and viscous rupture of the fiber are avoided. The effects of drawing temperature and feeding speed, which are crucial factors in determining the geometry and quality of the fiber, are investigated in detail. A multi-variable unconstrained optimal design problem is posed and considered in terms of the feasible domain. An appropriate objective function, comprised of the maximum velocity lag, thermally induced defect concentration and draw tension, is proposed to quantify the quality of the hollow fiber. The univariate search method is then applied to obtain the optimal drawing temperature and feeding speed. This study provides a basis for the optimization of hollow fiber drawing process and indicates that a substantial improvement in fiber quality can be achieved.     

高压风压力控制系统设计与优化

高压风是保证循环流化床锅炉返料系统正常工作的动力源,其压力直接影响锅炉返料腿的返料效果与锅炉设备的安全.针对某流化床锅炉高压风系统实际存在的缺陷,提出了增加工厂风作为备用风源的解决方案,并对高压风压力控制系统进行了优化.运行结果表明:经过此次系统的优化,大大降低了该锅炉因返料风压力越低限导致锅炉MFT的次数,有效地提高了锅炉运行的可靠性.     

Surface flaw in a pressurised and thermally-shocked hollow cylinder

The first part of this paper deals with stress intensity factors of a semi-elliptical crack, with a third order polynomial pressure distribution in a finite thickness flat plate. These solutions are determined by the alternating technique in three-dimensional fracture mechanics where both the front and back surface effects of the flat plate are accounted for. The second part is concerned with the applications of these solutions in deriving approximate solutions for a semi-elliptical crack in a pressurised cylinder and in a thermally-shocked cylinder. Curvature effects of the cylinder are estimated from two-dimensional finite element solutions of fix-gripped single-edge notched plates with prescribed crack pressure and single-edge notched cylinders with the same prescribed crack pressure. The stress intensity factors of a pressurised semi-elliptical crack in a flat plate are modified by this curvature correction factor to yield an estimate of the stress intensity factors of semi-elliptical cracks in a pressurised or thermally-shocked cylinder, with outer to inner diameter ratios ranging from 10:9 to 3:2 at crack depths of 0·4 to 0·8.     

压力流量控制器稳压储能原理探讨

介绍了压缩空气系统压力流量控制器的节能原理、系统储气能力计算方法，并对有无压力流量控制器的系统工况进行了对比，进一步证明了储能、稳压对压缩空气系统的重要性。     

Assessment of cracks under secondary and combined loading

Following a recent presentation of methods for the assessment of defects under primary loading, proposals are made here for the extension of these methods to combined primary and secondary loading, without necessarily involving the excessive pessimism of treating the secondary loading as primary, but allowing for strain enhancement at reduced ligaments. Finite element calculations have shown that the proposals provide a pessimistic bound on the value of the contour integral J in the cases considered for a number of work-hardening relationships and geometries, including cases of elastic follow-up.