Papers by Keyword: Expansion Ratio

Abstract: A 3-Dimensional fluid flow over the sudden expansion region of a horizontal duct for various Reynolds numbers have been studied by using the CFD Software package ANSYS Workbench Fluent v 13.0. The expansion ratio and aspect ratio for the sudden expansion are taken as 2.5 and 4 respectively. This work deals with the finding of critical Reynolds number for a fluid and also the length of re-attachments on stepped walls at various Reynolds numbers for the same fluid. The simulation is carried out in sudden expansion for Reynolds number ranging from 200 to 4000. The variations of local Nusselt number along the stepped walls of the sudden expansion are presented with the heat flux of 35 W/m2 on the stepped walls. Also, the plots of pressure coefficient (Cp) along the stepped walls for different Reynolds numbers are presented in this work.

Abstract: The foamed bitumen technology is experiencing a global renaissance and rather extensive development of innovative approaches with respect to both, its application and research, is clearly visible. However, the variability of available bituminous binders for utilization within the technology is quite large; therefore, a general methodology of quality parameters determination for foamed bitumen and the requirements for mixes bound by this type of binder must be specified.In general different types of pen grade bituminous binders can be used for producing the foam. Besides the pen grades which are defined by penetration and also its viscosity, the source of the bitumen can have important effect on final foamed bitumen quality given especially by its expansion ratio and stability of the foam as well. Experimental study has been done to compare different types of bitumen from different sources to assess the effects on the foamed bitumen and on cold recycled mixes produced by these binders. In parallel the effect of a suitable foaming agent has been assessed as well. The foamed bitumen was analyzed by its expansion ration, half time defining the stability of the foam and the so called foam index. Cold recycled mixes were produced with one type of reclaimed asphalt material and different foamed bituminous binders. For the mix assessment mainly indirect tensile strength, water susceptibility and stiffness modulus have been considered. Results and comparison of the evaluated effects are presented in this paper.

Abstract: Aluminum foam sandwiches (AFS) were successfully prepared by a powder metallurgical method. TiH₂ powders were pre-treated in air at 450°C and 500°C for 2h in order to clarify the effect of oxidation treatment on AFS in comparison to those as-received. The decomposition curves of as-received and oxidized TiH₂ powders were monitored using DSC. The macro-morphology, expansion ratio, interfacial bonding and cell structure of AFS were systematically investigated. The results show that the AFS utilize TiH₂ powders oxidized in air at 450°C for 2h exhibits the best performance, under which conditions the effective bonding between the panel and core, 200% of the expansion rate and uniform pore structure of AFS have been achieved.

Abstract: Combined with Taguchi method of experimental design and BP neural network technology, select process parameters including molding temperature, molding time and injection pressure, Taguchi experiments are respectively arranged for different diameters of sphere and cylinder, different side lengths of tri-prism and quadrangular prism, different thicknesses of thin sheet without hole and with hole etc. molds, then these experiment results are used as neural network sample data, and expansion ratio of EVA plastic can be predicted more accurately after neural network is trained.

Abstract: The expansive soil behaviour of expansive deformation and shear strength is deeply influenced by humidity condition. Different soil drying rate was set with constant temperature and different relative humidity. When saturated soil samples was dried to the different predetermined water content, the expansion ratio test with the upper load was made. It is shown that in the condition of high relative humidity, the expansion ratio is high. The smaller initial water content and upper load may lead to a larger swelling deformation. When soil samples with different initial water content was fully expanded, the consolidated direct shear tests were made. It is shown that the smaller drying rate leads to the greater shear strength after full expansion. What’s more, the upper load may improve the soil shear strength.

Abstract: It’s a chemical method that adding TOR into asphalt rubber to be TOR asphalt rubber mixture. In this study, 70# basic asphalt from Nanjing Jinling Company and 60 mesh waste rubber powder from Jiangyan Honglei Company were chosen for the SMA13 grading and SUP13 grading by the best preparation technology. The high temperature stability, anti-cracking performance and water stability of TOR asphalt rubber mixture were studied and the influence of dry and wet molding process on road performance of TOR asphalt rubber mixture was compared. The results show that both the dynamic stability and the low-temperature cracking performance of wet forming specimens are better than the dry process. The water stability of wet molding process is also slightly better than the dry process. And expansion rate tests were carried out on asphalt mixtures prepared by dry and wet forming processes on continuous gradation and discontinuous gradation to validate the applicability of discontinuous gradation to asphalt rubber.

Abstract: Combining with Jeffery equation and mechanics model of fixed point of Euler rigid body, research was done to study the mechanism and method of the short fiber radial orientation and characteristics of movement in tread extrusion process. The influence of tension flow field and shear flow field in flow channel on short fibers orientation has been systemically analyzed by flow characteristics of the tread during the extrusion process and combining with Jeffery equation and mechanics model of fixed point of Euler rigid body. The result show that the expansion ratio and the expanding angle of cross section are the key factors to determine the radial orientation of short fiber. Mathematical model of short fiber radial orientation was established. The extrusion die, which has a hinder dam by adopting such principle has been designed. The result also show that the best expansion ratio was 3-4, obtaining the average orientation angle between 70o-80o. and the rationality of the radial oriented mechanism and the mathematical model are verified.

Abstract: Continuous extrusion under the large expansion ratio is an advanced forming process for manufacturing copper strip, preventing mould structure, die structure, expansion chamber structure and the shape of the billet section is important process paraments of deformation. Based on the characteristic of the forming process, the model of rigid-plastic FEM on DEFORM-3D is established and the numerical simulation of continuous extrusion forming process of the copper strip is carried. The metal flow regularity and the mean-square deviation of velocity with the different process paraments is analyzed. As the result, when using the drum form of preventing mould with promote flow angle and the die with variable calibrating strap, the mean-square deviation of velocity is 0.58. When the second extending angle is 134°, the mean-square deviation of velocity is 0.23. When size of billet is 30 x 1.64 mm2, the mean-square deviation of velocity is only 0.19.

Abstract: In this paper, a concrete sulfate corrosion-resistance admixture is developed with anhydrite (CaSO₄), super fine slag powder (P800) and anhydrous calcium sulfo-aluminate (C-S-A). It is optimized by means of systematical research on specific surface area, setting time, expansion ratio, compressive strength ratio, corrosion resistance coefficient and expansion coefficient of 20 mixes, which are designed based on the hydration mechanism and performance requirements according to JC/T1011-2006. This new type sulfate corrosion resistance admixture has good performance and completely satisfies the requirements of industry standard JC/T 1011-2006 regarding “Sulfate Corrosion-Resistance Admixture for Concrete”, and has declared Chinese national invention patent (201010256189.2).

Abstract: With the rapid development of highway construction and rehabilitation, more and more waste asphalt mixture is produced. The waste is under great environment pressure. The reuse of the waste is urgent. Foamed asphalt cold recycling is a solution. In this paper, the foaming abilities of different kinds of asphalts are tested and the best foaming asphalt is found out. Then, the RAP is evaluated. Finally, the properties of the cold recycling mixture are studied. As a comparison, two different gradations with different amount of RAP are designed and their performances are evaluated. By all these tests, it is illustrated that the cold recycled asphalt mixture with foamed asphalt can fulfill all the technical requirements. The foamed asphalt mixture began its first use in Beijing and exhibits well.