The influence of porosity on the fatigue life for sand and permanent mould cast aluminium

The automotive industry always strives to achieve light weight components to reduce fuel consumption and to meet environmental requirements. One way to obtain weight reduction is to replace steel components with components made of aluminium or other light weight materials. Aluminium has good corrosion properties and a high strength to weight ratio which makes it favourable in many applications. The increased use of aluminium castings in the automotive industry does also imply that the need for design data for aluminium increases. Especially for castings, the influence of casting defects are always an issue. For this reason fatigue properties for as-cast sand and permanent mould specimens with different contents of porosity have been studied.

Sand cast and permanent mould cast aluminium specimens of two different geometries were fatigue tested in cyclic bending at R = −1. Prior to fatigue test specimens were examined by X-ray and sorted into three quality groups depending on the porosity level. The aim of this work was to investigate the fatigue life for sand cast and permanent mould cast AlSi10Mg with different amounts of porosity. An additional aim was to predict the largest defect contained in a specified volume of a component, by using a statistical analysis of extreme values, and relate it to the fatigue life.

The results showed that fatigue strength for a smooth specimen geometry decreases by up to 15% with increased porosity. For specimens with a notched geometry, no influence of porosity on the fatigue strength was found. This is believed to be due to a much smaller volume subject to high stress than for specimens with low stress concentration.     

Motion of viscoelastic liquids in a porous medium

Nonlinear effects occurring in filtration of viscoelastic liquids are considered. The qualitative differences between one-dimensional and planar cases and between motion in homogeneous and inhomogeneous porous media are demonstrated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 5, pp. 751–756, May, 1987.     

Onset of convection in porous materials with vertically stratified porosity

The onset of convection in porous materials with vertically stratified porosity is studied. By means of an auxiliary integral equation, the absence of subcritical instabilities is shown and??in closed form??the global stability condition is obtained. How??in artificial porous materials??the porosity could be vertically stratified in order to either inhibit or promote the onset of convection is analyzed.     

Structural characterization and porosity analysis in self-supported porous alumina-silica thin films

In this study, alumina, silica and alumina-silica binary (36% mol silica) thin films are synthesized using the sol-gel technique. These form the basis for future gas separation membranes. The characterization of the synthesized oxides was performed using nitrogen physisorption, X-ray diffraction (XRD), Doppler-broadening measurements on the 511 keV annihilation photon peak, together with 3γ/2γ analysis, and Fourier transform infrared spectroscopy (FTIR) of adsorbed CO. It is found that silica is microporous, γ-alumina is mesoporous, and the binary material shows fingerprints of both the meso- and microporous nature of its constituents as well as of the respective crystal structures. These results open the possibility to also investigate thin supported porous films (a few microns thick), and especially the setting and drying aspects on porous supports for membrane production, using the positron annihilation technique.     

Ionic liquids confined in porous matrices: Physicochemical properties and applications

Ionic liquids are emerging as important materials for applications in electrochemical devices, green chemistry etc. For device applications, ionic liquids are generally, either incorporated in polymer matrices or confined in porous matrices (giving rise to an interesting class of materials ‘Ionogels’). This review deals with the science and technological applications of ionic liquids confined in nano-pores. A comprehensive overview is given about the experimental studies dealing with the changes in the physico-chemical properties of ionic liquids like thermal phase transition, stability, dynamical behavior, optical properties etc. Recent theoretical studies highlighting the layering and structural heterogeneity of ionic liquids confined in nano-pores are also discussed. To make the review self-reading, basic ideas about ionic liquids and the phenomena of confinement are also briefly included.     

Experimental investigations of filtration of relaxing liquids in heterogeneous porous media

Experimental investigations of filtration of relaxing liquids in heterogeneous porous media are performed. Models for describing the obtained results are proposed that can be used in practical calculations. Institute of Mathematics and Mechanics of the Academy of Sciences of Azerbaijan, Baku. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 1, pp. 9–15, January–February, 1996.     

Generic and SME-specific factors that influence the BIM adoption process: An overview that highlights gaps in the literature

Building information modeling/management (BIM) is an emerging technological and procedural shift in the architecture, engineering, construction and operation industry. In this study, we use an extensive state-of-the-art method to clarify the BIM adoption process and the factors that can influence the success or failure of BIM adoption, particularly during the implementation stage, which are not frequently found in the literature. As an innovation, the lexical field allocated to the spread of innovations is assigned to BIM (diffusion, adoption, and implementation). After recalling the definition of relevant terms and then removing the resulting inconsistencies in vocabularies, we investigate various studies to identify factors that influence BIM adoption and then unify all these studies in one coherent and consistent BIM adoption process model. We focus on factors that play a role in the adoption of BIM in small- and medium-sized enterprises (SMEs) because SMEs constitute the majority of companies in the construction sector. This research highlights and intends to fill in some gaps found in the current BIM adoption literature.     

Substance transfer in a porous medium saturated with mobile and immobile liquids

Consideration has been given to the problem of transfer of a substance in a porous medium consisting of two zones: a) with transit pores (with a mobile liquid) and b) with an immobile liquid (with bound water) with allowance for the effects of convective transfer, hydrodynamic dispersion, substance adsorption, and internal mass transfer between both zones. The fields of substance concentration, adsorption, and internal mass transfer for different cases determined by the character of adsorption and internal mass exchange have been determined. It has been established that the presence of zones with an immobile liquid significantly influences the general characteristics of substance transfer in the porous medium.     

Net flow of compressible viscous liquids induced by travelling waves in porous media

The influence of ultrasonic radiation on the flow of a liquid through a porous medium is analyzed. The analysis is based on a mechanism proposed by Ganiev et al. according to which ultrasonic radiation deforms the walls of the pores in the shape of travelling transversal waves. Like in peristaltic pumping, the travelling transversal wave induces a net flow of the liquid inside the pore. In this article, the wave amplitude is related to the power output of an acoustic source, while the wave speed is expressed in terms of the shear modulus of the porous medium. The viscosity as well as the compressibility of the liquid are taken into account. The Navier–Stokes equations for an axisymmetric cylindrical pore are solved by means of a perturbation analysis, in which the ratio of the wave amplitude to the radius of the pore is the small parameter. In the second-order approximation a net flow induced by the travelling wave is found. For various values of the compressibility of the liquid, the Reynolds number and the frequency of the wave, the net flow rate is calculated. The calculations disclose that the compressibility of the liquid has a strong influence on the net flow induced. Furthermore, by a comparison with the flow induced by the pressure gradient in an oil reservoir, the net flow induced by a travelling wave can not be neglected, although it is a second-order effect.     

Mass deployment of sustainable transportation: evaluation of factors that influence electric vehicle adoption

Mass penetration of electric vehicles into the market will have a number of impacts and benefits, including the ability to substantially reduce greenhouse gas emissions from the transportation sector. Therefore, it is expected that in coming years this technology will progressively penetrate the market. This research presents an analysis of factors that influence electric vehicle adoption by modeling the conditions under which an individual, particularly one with an engineering or technical background, is more or less likely to adopt an electric vehicle. This model is developed by considering demographic determinants as well as behavioral and attitudinal measures that affect individual adoption of the technology. The methodology involves applying logistic regression to provide a good fit and predict the response given explanatory variables. Analyzing these outcomes generates empirical findings that better inform electric vehicle technology and policy development. This study takes into account preferences of potential customers and analyzes how individuals with engineering and technology background differ in electric vehicle adoption considerations compared to the general population. Therefore, this research provides both engineers and policy makers with critical information for developing future electric vehicle technology. The model results show that several factors including willingness to pay for new appealing technology, distance driven, perceptions of electric vehicles as good for the environment, perception of EV speed are statistically significant in influencing willingness to purchase an electric vehicle.     

Influence of the porosity of a porous medium on the effective viscosity in Brinkman's filtration equation

Summary Brinkman's filtration equation is usually used to describe the low-Reynolds-number flow in porous media in situations where velocity gradients are non-negligible. In this paper a model problem is analysed to determine the influence of the porosity of the porous medium on the effective viscosity in Brinkman's filtration equation. In the idealized problem we consider axial flow through infinite and streaked arrays of cylindrical rods. Suppose that in such porous medium the flow is described by Brinkman's filtration equation then the effective viscosity can be calculated as a function of porosity. Contrary to the Einstein correction for dilute suspensions it is shown in this paper that the effective viscosity may be less than the viscosity of pure fluid.With 4 Figures     

BP模型在预测多孔NiTi合金孔隙度和屈服强度上的应用

基于BP神经网络的原理,建立了热爆法合成多孔NiTi形状记忆合金孔隙度和压缩屈服强度的神经网络模型.该模型拟合了温度、Ti粉颗粒尺寸和生坯密度对热爆产物孔隙度和压缩屈服强度的影响.当温度、Ti粉颗粒尺寸和生坯密度发生变化时,对反应产物的性能进行了预测,其预测值和实验值非常吻合.因此该模型可用于多孔NiTi形状记忆合金的性能控制,通过对性能的合理调控,使其与所替换的生物组织更加匹配,同时提高研究效率,降低成本.     

Effect of porosity and tension–compression asymmetry on the Bauschinger effect in porous sintered steels

The Bauschinger effect is a common phenomenon in metallic materials. In this paper, the Bauschinger effect in Fe–0.85Mo–2Ni powder metallurgy (PM) steel was investigated for different porosities and as a function of loading sequence (compression–tension versus tension–compression). Both the porosity and loading sequence had a significant effect on the magnitude and asymmetry of Bauschinger effect. Compression followed by tensile loading lead to a higher Bauschinger effect than tension followed by compression. This asymmetry of Bauschinger effect was more significant for higher porosity. Crack formation and propagation, observed in this study, were the main factors influencing the asymmetry in Bauschinger effect. Finite element analysis, based on the actual microstructure of the steels, yielded good agreement with the experimental stress-strain behavior. FEM showed that both the Bauschinger effect in the steel matrix and porosity contribute to the global Bauschinger effect of the PM steels.