Papers by Keyword: Aspect Ratio

Abstract: Natural convection is studied numerically using finite element based computational procedure. The enclosure used for flow and heat transfer analysis has been bounded by adiabatic top wall, constant temperature cold vertical walls and a horizontal bottom wall. The grid independent study has been made with different grids to yield consistent values. Different grid sizes 30x30, 40x40, 50x50 uniform meshes have been studied. Study shows the convergence of average Nusselt number for a grid size of 41x41. Hence a grid size of 40x40 is used in all computations. Nusselt numbers are computed for different Rayleigh’s numbers (Ra) and aspect ratios of 1,2 and 3. Results are presented in the form of streamlines, isotherm plots and average Nusselt number. The average Nusselt numbers increase with Rayleigh number and for a given Ra, increase in Nu is obtained with increase in aspect ratio for bottom wall.

Abstract: The mechanical tests of normal concrete (NC) specimens, steel fiber reinforced concrete (SFRC) specimens and polypropylene fiber reinforced concrete (PPFRC) specimens have been carried out. Fiber-reinforced concretes containing different volume fraction and aspect ratio of steel and polypropylene fibers were compared in terms of compressive, splitting tensile, ultimate tensile properties. Test results indicate that the mechanical properties of NC can be improved by addition of steel fibers and can be enhanced with the increase of fiber content. However, polypropylene fiber may cause opposite effect, if volume fraction too high.

Abstract: Carbon reinforced aluminium laminate (CARAL) is a fibre metal laminate which consists of layers of carbon fibre and thin layers of aluminium. Buckling strength of CARAL under various support conditions is studied in this paper. Since CARAL is composed of fibre and metal, the pattern of failure of the laminate under compressive loads is truly imperative. The compressive buckling strength depends on geometrical parameters like length and width of the specimen and the sequence in which the layers are stacked. It also depends on the boundary condition. In this study, the critical buckling load is determined by varying the parameters such as aspect ratio (length/width), stacking sequence and boundary condition. Two different boundary conditions are considered, simply supported and fixed support condition. Numerical simulation analysis shows a maximum deviation of 16.72% from experimental results. The different failure modes executed by the laminate under compressive loading are also determined. The critical buckling load of CARAL constrained on all sides is evaluated numerically for different boundary conditions. Buckling load, in this case, takes maximum value when CARAL is clamped on all sides whereas it takes minimum value when the plate is simply supported on three sides keeping the fourth side fixed.

Abstract: Aspect ratio is a key factor to calculate stress intensity factor (SIF) K using fracture mechanics. While cracks are approximated to be semi-circle or semi-ellipse for simply evaluation, their shapes are changed by stress concentration source. In this study, a new method to modify aspect ratio of a crack at a notch root is proposed. Modified aspect ratio in this method succeeded to decrease prediction error of fatigue crack initiation stress, σ_w1 which was calculated using experimental value.

Abstract: Wind loads on buildings in realistic environments may be considerably either increase or decrease by interference buildings. It is commonly known as interference effect. This effect depend on the geometry and arrangement of these structures. It is objective of this work to study the interference effects of the tall buildings which have the different aspect ratios, upstream terrain conditions, distance between adjacent structures and direction. The obstructing model used in this work have the aspect ratio of 2, 3 and 4 and the distances between adjacent buildings are 0.5B, 1.0B, 1.5B and 2.0B, which B is the width of the building. And the above experimental results were compared with experimental data measured on isolated building.

Abstract: Strain hardening occurs as a result of extensive plastic deformation of a material at below recrystallization temperature. The powder metallurgy route subjects the elemental powders to highly plastic deformation under compaction; however it is softened while it is sintered. In order to enhance its mechanical behaviour, it is usually subjected to secondary deformation operation. In the present investigation the cold upsetting exercise is carried out in three different lubricants condition with two different preform geometries on sintered Fe-0.75%C. Unlike the conventional material under plastic deformation the matrix gets strain harden, in P/M material along with matrix the geometry supplements the strain hardening behaviour. The nature of matrix and geometric hardening behaviour has been dealt. In addition an empirical relationship and its corresponding parameters experimental values have been predicted which is of high importance in design of preforms and die-set for actual production.

Abstract: In order to promote the comprehensive utilization of salt lake brine resources, magnesium carbonate tri-hydrate (MgCO₃·3H₂O) was synthetized by low-temperature hydrothermal technique using purified MgCl₂-rich brine and ammonium hydrogen carbonate solution as raw materials, the orthogonal experimental as method. The morphology could be tuned by changing the operating parameters. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the structures and morphologies of the products. The results show that the optimum conditions are as follows : reaction temperature is 40-50°C, n (Mg²⁺):n (HCO₃^-)=1:2.2, pH value is 8.8-9.0, stirring speed is 130 r/min, aging time is 3h, reaction time is 70 min. Magnesium carbonate tri-hydrate synthetized is one-dimensional acicular with good settling performance. Average aspect ratio could up to 29.60.

Abstract: The effectiveness of heat transfer and the pressure drop coefficient of staggered elliptical tube banks are studied experimentally. The bank consists of 11 elliptical tubes of 0.75 equivalent diameter in an arrangement of 4-3-4. The major and the minor sub-axis of each tube are 24.70 mm and 12.35 mm respectively, and therefore the aspect ratio (AR) of the tube is 2.0. The geometric parameters of the bank are S_T = 24.70 mm, S_L = 37.00 mm and minimum frontal area B = 12.35 mm. Seven mid-tubes are internally heated by electrical heater of 69.6 Watt each. Experiment is conducted in a sub sonic wind tunnel and run with the wind velocities of 1 m/s 12.6 m/s which correspond with Reynolds number of = 346-6904. The results show that the effectiveness (ε) varied from 2144.44 to 15.26. It decreases exponentially at low Reynolds numbers and tended asymptotically at higher Reynolds number. The coefficient of pressure drop (CΔp) ranges from 7.21 to 4.41 decreases continuously at low Reynolds number and asymptotic at higher one.

Abstract: In the last several decades, coupled shear wall have become recognized as efficient lateral load resisting systems for high-rise structures, increasingly. Coupled shear walls give considerable lateral stiffness and strength as well as providing an architecturally practical structural system. In this paper, in order to observe seismic performance of coupled steel plate shear wall, models of previous study was verified, and coupled shear wall with steel plate was carried out with various parametric analysis. Parametric analysis was performed with various width of bay. As a result, model that aspect ratio of steel plate was close to 1 was the most structurally safe.

Abstract: Surface cracks with aspect ratio can occur in pipelines subjected to corrosion attacks. There are few studies on interaction relationship for double semi-elliptical surface cracks with such high aspect ratio. This paper attempts to develop a finite element method to determine on interaction of two semi-elliptical internal surface cracks with high aspect ratio by analyzing two key fracture mechanics parameters, i.e., the stress intensity factor and the-stress. The numerical results prove that the existing flaw-interaction criteria are too general to lose the worthy of application especially in pipeline engineering.