Sharif Digital Repository

Gas injection into reservoirs can be used to increase oil recovery. However, reservoir heterogeneity and high gas mobility reduce sweep efficiency and decrease recovery. Using foam can reduce gas mobility and therefore increase sweep efficiency. Foam is thermodynamically unstable, so it is important to predict the foam stability. In order to understand the influence of oil presence on foam stability, static experiments performed on foam by varying the type and amount of added oil and molecular weight of added alkane. Also static foam properties have been investigated by varying the surfactant concentration, ionic strength, composition of different salts in the sample, and addition of polymer... 

Long-chain branches are incorporated into the molecular backbone of a polypropylene (PP) in a foaming process. The branching of PP occurs by radical reactions of dicumyl peroxide and a tri-functional monomer, trimethylol propane trimethacrylate. Use of peroxide without tri-functional monomer results in scission of PP molecular chains and significant reduction in melt viscosity. The increase in melt viscosity in conjunction with the flow ability of the modified PP indicates that the polymer has a branched structure. Melting temperature of PP remains unchanged with branching reactions implying that reactions occur mainly in amorphous regions of PP. The improvement in melt strength and... 

The effect of spot welding failure, flange location, sheet metal thickness, glue presence in foam-wall contact area, and foam filling on the bending crash performance and the collapse mechanism of empty and foam-filled box-beams is investigated. It is observed that the flange location in box-beams controls spot welds force, the energy absorption capacity of box-beams, and collapse behavior of the sections. As a result, the definition of spot weld failure criterion is inevitable in most cases. A survey on the effect of slight aluminium foam filling (12% mass increase) shows that the specific energy absorption value (SEA) and the energy dissipation performance of a filled section can even... 

Experiments are being conduced in a photography technique to examine flow of aluminum, cast iron and steel into the molds. The purpose is to observe some parameters such as gas gap length, foam decomposition products, metal front and mold filling time in lost foam casting of aluminum, cast iron and steel. Foam-metal interface reactions and gas evolution have been observed during mold filling. The results indicate that the metal pouring temperature and foam density and coating layer thickness affect mold filling time. In the steel lost foam casting, the gas gap length and gaseous products volume and the mold filling time are significantly larger than the cast iron. In both the cast iron and... 

In this paper, the effects of foam density distribution and initial impactor inclination angle on crushing behaviour of metal foam-filled thin-walled square columns have been investigated. The simplified version of an existing pressure dependent self-similar constitutive model with tensile failure for metal foam has been implemented in ABAQUS/Explicit code. Random distribution of cubic regions with normal distribution of density has been created. The analyses have been accomplished for three distinct foam densities, two extreme random distributions (fine and coarse), and five different impactor inclination angles. A local effect on folding patterns of columns filled with low-density foam has... 

The crushing behaviour of dynamically loaded metal foam-filled square columns has been investigated using an extended version of the existing self-similar pressure dependent constitutive model for metal foams. The model has been implemented in ABAQUS/Explicit and analyses have been conducted using different approaches to model the uniaxial and hydrostatic hardening behaviour of metal foams. A practical and reliable procedure to approximate the observed anisotropic behaviour within the computational framework of isotropic plasticity is introduced. The comparison between the available experimental and newly generated numerical results is presented in order to illustrate the accuracy and... 

The effects of SiC addition on the foaming behavior and compressive properties of AlSi7 metal foams were studied. Elemental powders of Al, Si, SiC and TiH2 were mixed, hot compacted and foamed at temperatures between 750 and 810 °C. The role of SiC volume fraction up to 10 vol.% and its particle size (3, 8 and 16 μm) was investigated. It was found that the foaming behavior of AlSi7 alloy, i.e. the maximum foam expansion and its stability, depends on the size and volume fraction of SiC particles. Increasing the amount of the ceramic particles and/or decreasing the particle size leads to less melt drainage whilst the cell structure becomes non-uniform. This is attributed to the effect of the... 

Composite aluminum-SiC foam was manufactured by injection of air and addition of reinforcement particles into the liquid aluminum. Microstructure and mechanical properties of the Al/SiC foams were investigated by scanning electron microscopy and compression tests. Results showed that both the cell size and the wall thickness augmented with increasing of the SiC reinforcement particles; while SiC particles resulted in the reduction of the plateau border length. With more SiC particles, plateau stress became larger; but maximum plateau strain became smaller. The stress-strain curves exhibited serrations in the plateau region due to addition of the SiC particles  

Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass-ceramic composition were investigated using the sintering route. The foaming agent was 2 wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass-SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass-SiC wetting angle was decreased from 85°for the lead-free glass, to 55°for the glass that contains 15 wt.% PbO  

Mobile and rapidly assembled structures play an important role in building temporary and semi-permanent accommodations and shelters in post-disaster management. One of the most efficient construction systems that can be used in rapidly assembled buildings is lightweight panelized systems. Use of rapidly assembled panelized systems is becoming very popular for cutting the construction time and transportation costs that make them suitable options for rapid assembly construction. In addition, when acoustic and thermal insulation of buildings is important, foam filled composite sandwich panels are an effective solution. Soft, semi-rigid and rigid Polyurethane (PU) foams, which are first... 

The aim of this study is to compare the synergistic impact of like and opposite-charged nanoparticle and surfactant systems on enhancing stability and mobility of foam in the absence and presence of oil which is not sufficiently discussed in the available literature. Stability of nanoparticle dispersion is examined at various levels of pH when nanoparticle and surfactant are in like and opposite-charged conditions. In situ modification of silica nanoparticle by opposite-charged surfactant is analyzed. Static stability tests as well as Hele–Shaw cell are employed to understand how nanoparticle and surfactant charges may control the stability and mobility of foam when oil is present/absent.... 

This paper presents experimental results on the foaming behavior and compressive properties of AlSi7-3 vol.% SiC metal foam. Elemental powders of Al, Si, SiC and TiH2 were mixed, hot compacted and foamed at 750, 780 and 810 °C. It was shown that the addition of fine SiC particles (mean diameter of 3 μm) increases the melt expansion and improves the stability of AlSi7 foam. A less drainage in the cell structure was also noticed. Meanwhile, large irregular cells in the macrostructure and a slight degradation of the mechanical properties under compressive load were observed. © 2007 Elsevier B.V. All rights reserved  

In this investigation, an algorithm was developed to calculate the gas pressure at the melt/foam interface (gap) owing to degraded foam during mould filling in the lost foam casting process (LFC). The effect of back-pressure on mould filling was modelled using a new experimental function by the addition of a three-dimensional volume of fluid (3D-VOF) function. The molten flow and free surface were simulated using the solution algorithm-VOF (SOLA-VOF) numerical technique. To simulate the three-dimensional incompressible flow in the LFC, the pressure boundary conditions, heat transfer and foam gas pressure effect were modified. Finally, in order to verify the computational results of... 

Foamy Al alloy SiCp composites of different densities ranging from 0.4 to 0.7g/cm3 were manufactured by melt-foaming process, which consisted of direct CaCO3 addition into the molten A356 aluminum bath. Mechanical properties and morphological observations indicated that the three-stage deformation mechanism of typical cellular foams is dominant in the produced A356 aluminum foams. Middle-stage stress plateau shrinkage plus compressive strength and bending stress enhancements were observed in denser foams. With the same Al/SiCp ratio, energy absorption ability and plastic collapse strength of the closed-cell foams were increased with the foam density. Doubling cell-face bending effects...