Habib Alehossein
Commonwealth Scientific and Industrial Research Organisation
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Publication
Featured researches published by Habib Alehossein.
Journal of Fluid Mechanics | 2007
Z. Qin; Klaus Bremhorst; Habib Alehossein; T. Meyer
A model for simulating the process of growth, collapse and rebound of a cavitation bubble travelling along the flow through a convergent-divergent nozzle producing a cavitating water jet is established. The model is based on the Rayleigh-Plesset bubble dynamics equation using as inputs ambient pressure and velocity profiles calculated with the aid of computational fluid dynamics (CFD) flow modelling. A variable time-step technique is applied to solve the highly nonlinear second-order differential equation. This technique successfully solves the Rayleigh-Plesset equation for wide ranges of pressure variation and bubble original size and saves considerable computing time. Inputs for this model are the pressure and velocity data from CFD calculation. To simulate accurately the process of bubble growth, collapse and rebound, a heat transfer model, which includes the effects of conduction plus radiation, is developed to describe the thermodynamics of the incondensable gas inside the bubble. This heat transfer model matches previously published experimental data well. Assuming that single bubble behaviour also applies to bubble clouds, the calculated distance from the nozzle exit travelled by the bubble to the point where the bubble size becomes invisible is taken to be equal to the bubble cloud length observed. The predictions are compared with experiments carried out in a cavitation cell and show good agreement for different nozzles operating at different pressure conditions.
International Journal of Rock Mechanics and Mining Sciences | 1999
M. S. Bobji; K Shivakumar; Habib Alehossein; V Venkateshwarlu; S.K. Biswas
Indentation hardness is usefully applied in the field of rock comminution, where high contact stresses are commonly encountered. Hardness measurements provide a means for estimating the discontinuity wall strength which is required to understand the shear strength of the discontinuity. The hardness value is also used to estimate compressive strength of rocks with known density. Hardness is measured by penetrating a hard indenter of known geometry onto the rock, either quasi-statically or dynamically. However, the scatter involved in such measurements is quite large. Some of the reasons for the scatter could be attributed to local variation in the composition and grain size of the minerals, bond strength of the matrix, presence of flaws and geometric irregularities (roughness) of the surface under the indentation region. The scatter due to surface irregularities or roughness can be reduced by polishing the surface of the rock. Polishing of rock surface becomes diAcult particularly during in situ measurements. In such situations the study of the eAect of surface roughness on the scatter in hardness measurements becomes imperative. In this paper, the quasi-static indentation of a fractal surface is numerically simulated to characterize the scatter resulting from surface roughness in terms of surface roughness parameters such as fractal dimension, D and the root mean square (rms )o f asperity height.
Journal of Materials in Civil Engineering | 2012
Habib Alehossein; B. Shen; Z. Qin; C. Huddlestone-Holmes
Backfilling and injection of granular materials into mining induced voids, separated beddings, and cracks, as either diluted slurry or concrete paste, is widely used to control coal mine subsidence. As a viable environmental solution, mine waste and rejected materials from underground coal seams are used in both backfilling and injection mine operations. During longwall mining, the grout slurry is pumped into the separated beds of the fractured rock mass through a pipeline connected to a central vertical borehole, which is drilled deep into the interburden rock strata above the coal seam. Either as dilute slurry or thick paste or cake, the fill material normally needs to travel a significant distance in a long pipeline. A blockage can occur in the pipeline when the slurry velocity falls below a certain critical threshold value, indicating a material phase change from cohesive-viscous to cohesive-frictional. In a previous study of radial flow through disks, complete analytical solutions of the required pump pressure versus fluid volume rate were presented for such slurries, categorized as frictional Bingham-Herschel-Bulkley fluids. This paper is an extension to the theory of fluid mechanics to this type of flow in uniform circular pipes. General analytical solutions were developed for complex fluids in velocity and pressure gradients and velocity and pressure as a function of pipe length, from which special and familiar equations for simpler fluids are derivable by mathematical reduction of the general equations. This study differs from the previous research in consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behavior, and implementation of a friction function to mimic behavior of the depositing and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance.
Advanced Materials Research | 2009
Habib Alehossein; Xing S. Li; Jim N. Boland
Industrial application of synthetic diamond ceramics is growing very fast due to their super hardness, superb wear resistance and long-life durability. In rock, concrete and metal cutting, drilling, mining and quarrying and dimension stone industries, cutting tools made of diamond composites or impregnated diamond composite segments are gradually replacing the more commonly used cemented tungsten carbide (WC) tools. Through its SMARTCUT research program, CSIRO in the past 15 years has developed harder and stronger thermally stable diamond composite (TSDC) drag picks to encourage and help manufacturing and mining industries improve their cutting performance by replacing these traditional WC cutting tools with the new revolutionary TSDC tools. This improvement process however is much more complex than a simple material or cutting tool replacement, since the mechanism and configuration of cutting are substantially different in the two cutter head systems and its successful implementation requires a better understanding of the basics of rock cutting. Some of the factors influencing the differences are: cutter wear, fracture toughness, compressive and tensile strength, thermal properties, geometrical shape, spacing, angle of attack, rake angle, sharpness and bluntness characteristics, lacing design and cutter arrangements. Besides, it is most important to understand the relation between the tool or tool force and the fragmentation of the rock, which is the main focus of this paper.
Communications in Numerical Methods in Engineering | 2000
Habib Alehossein; A. Korinets
A mesh-independent finite difference method for elastoplastic boundary value problems with strain softening is proposed. The regularization of the problem is achieved by introducing the second-order gradient of the plastic multiplier in the yield function. The addition of a gradient term in the material failure criterion preserves ellipticity or hyperbolicity conditions and consequently removes mesh dependency after the strain-softening regime has been entered. The method is extended to the Mohr–Coulomb material model and the implementation of the gradient-dependent plasticity theory to finite difference codes is discussed. Copyright
Rock Mechanics and Rock Engineering | 2016
Mehdi Serati; Habib Alehossein; N. Erarslan
Using a three-dimensional analytical approach, the sensitivity of the Brazilian test to its standard testing recommendations was investigated. It was concluded that the tensile stress induced in a Brazilian disc is significantly affected by the distribution of the applied load along its thickness rather than its circumferential condition. Under a non-uniform contact pressure along the BTS thickness, it was evident that both the numerical value and the location of the maximum tensile stress varied as a function of the geometrical aspect ratio of the disc specimen. For test conditions in which load distribution in the contact region along the thickness does not follow the standards or the uncertainty of its exact nature is large, e.g. in testing of super hard materials with relatively high stiffness and hardness greater than the contact testing platens, great care should be taken in regard to the interpretation of the Brazilian test result.
Materials | 2012
Habib Alehossein; Karsten Beckhaus; Martin Larisch
Tremie pipes are used to control concrete flow rate and minimize bleeding and dilution when placed into deep, submerged excavations. The L-box test is designed to measure workability and flowability of tremie pipe concrete as an indirect index measure of concrete viscosity and plastic yield. This test has been simulated by a mathematical model of the representative partial differential equation (PDE) derived for one-, two-, and three-dimensional (1-D, 2-D, and 3-D) applications. The L-box model solves a dimensionless PDE in terms of the flow velocity along the L-box channel length as a function of time and distance, which is analogous to a nonhomogeneous heat conduction equation. An example problem for the 1-D application has been solved both numerically (by the finite difference method) and analytically (using Fourier analysis). The two methods and results are comparable and model the concrete flow behavior as observed in standard laboratory L-box tests.
ASME 2012 International Mechanical Engineering Congress and Exposition (IMECE2012) | 2012
Mehdi Serati; Habib Alehossein; David J. Williams
Steel roller discs are an efficient mechanical tool for cutting soft to medium strength rocks in both civil and mining projects. However, their application for hard rock cutting has been hindered since steel discs wear quickly and fail prematurely due to high concentrated stresses generated at the sharp corners and thin elements of the disc. To overcome this problem, the current generation roller discs comprises a steel shaft connected to a tungsten carbide (WC) disc. In other words, while the material of the disc itself is replaced by a stronger WC material, steel continues to be used for the shaft body. In this paper, to comprehend the influence of material parameters on the induced stresses inside different parts of a roller cutter, an analytical closed-form solution and a series of finite element (FEM) numerical studies are performed. By considering the problem as a traction boundary-value problem in an elastic domain, the analytical solution is based on the Airy stress formulation in Cartesian coordinates with a Fourier series representing the boundary conditions. The analytical result is developed for both plane stress and plane strain conditions, encompassing all possible loading con?gurations and shaft geometries. To verify the numerical models, these results are also compared with laboratory experimental data obtained from cutting granite using mini discs for the penetration range 1 to 3 mm.
INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM 2015) | 2016
Habib Alehossein; Zongyi Qin
Most materials in mining and civil engineering construction are not only viscoplastic, but also cohesive frictional. Fresh concrete, fly ash and mining slurries are all granular-frictional-visco-plastic fluids, although solid concrete is normally considered as a cohesive frictional material. Presented here is both a formulation of the pipe and disc flow rates as a function of pressure and pressure gradient and the CFD application to fresh concrete flow in L-Box tests.
11th International Conference of Numerical Analysis and Applied Mathematics 2013, ICNAAM 2013 | 2013
Habib Alehossein; Z. Qin
The shear stress generated in mine backfill slurries and fresh concrete contains both velocity gradient dependent and frictional terms, categorised as frictional viscous plastic fluids. This paper discusses application of the developed analytical solution for flow rate as a function of pressure and pressure gradient in discs, pipes and cones for such frictional Bingham-Herschel-Bulkley fluids. This paper discusses application of this continuum fluid model to industrial materials like mine and mineral slurries, backfills and fresh concrete tests.
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