Permeability tensor for various columnar dendrite structures

The complete prediction of the second order permeability tensor for a three dimensional multi-axial preform is critical if we are to model and design the manufacturing process for composites by considering resin flow through a multi-axial fiber structure. In this study, the in-plane and transverse permeabilities for a woven fabric were predicted numerically by the coupled flow model, which combines microscopic and macroscopic flows. The microscopic and macroscopic flows were calculated by using 3-D CVFEM(control volume finite element method) for micro and macro unit cells. To avoid a checkerboard pressure field and improve the efficiency of numerical computation, a new interpolation function for velocity is proposed on the basis of analytical solutions. The permeability of a plain woven fabric was measured by means of an unidirectional flow experiment and compared with the permeability calculated numerically. Reverse and simple stacking of plain woven fabrics were taken into account and the relationship between the permeability and the structures of the preform such as the fiber volume fraction and stacking order is identified. Unlike other studies, the current study was based on a more realistic three dimensional unit cell. It was observed that in-plane flow is more dominant than transverse flow within the woven perform, and the effect of the stacking order of a multi-layered preform was negligible.

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Study on the Formation of Stray Grains during Directional Solidification of Nickel-Based Superalloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.1582 ◽

2016 ◽

Vol 879 ◽

pp. 1582-1587 ◽

Cited By ~ 3

Author(s):

Maria Rita Ridolfi ◽

Oriana Tassa ◽

Giovanni de Rosa

Keyword(s):

Directional Solidification ◽

Gas Turbines ◽

Complex Geometry ◽

Turbine Blades ◽

Columnar Dendrite ◽

Affecting Factors ◽

Stray Grains ◽

Geometrical Factors ◽

Stray Grain ◽

The Impact

Ni-based superalloy single-crystal turbine blades are widely used in gas turbines for aircraft propulsion and power generation as they can be subjected to high service temperature and show high mechanical properties due to the almost total elimination of grain boundaries. Particularly in presence of complex geometry shapes, rare grains nucleating apart from the primary grain, become a serious problem in directional solidification, when characterized by high-angle boundaries with the primary grain, extremely brittle due the elevated amount of highly segregating elements and the absence of grain boundary strengthening elements. It is of fundamental importance analyzing the physical mechanisms of formation of stray grains, to understand which thermo-physical and geometrical factors highly influence their formation and to find possible ways to reduce the impact of the problem. In this paper, constrained dendrite growth and heterogeneous grain nucleation theories have been used to model the formation of stray grains in directional solidification of Ni-base superalloys. The study allows to derive the preferred locations of stray grains formation and the role played by the most affecting factors: (i) geometrical: angle of primary grain dendrites with withdrawal direction and orientation of the primary grain with respect to the side walls, responsible for the formation of volumes where the stray grain undercooling is lower than the undercooling of the columnar dendrite tip; (ii) process and alloy: thermal gradient ahead to the solidification front and alloy composition, influencing the columnar dendrite tip undercooling; (iii) wettability of foreign substrates, on which the stray grain undercooling strongly depends.

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Numerical Calculation of Equivalent Permeability Tensor for Fractured Vuggy Porous Media Based on Homogenization Theory

Communications in Computational Physics ◽

10.4208/cicp.150709.130410a ◽

2011 ◽

Vol 9 (1) ◽

pp. 180-204 ◽

Cited By ~ 29

Author(s):

Zhaoqin Huang ◽

Jun Yao ◽

Yajun Li ◽

Chenchen Wang ◽

Xinrui Lv

Keyword(s):

Porous Media ◽

Network Model ◽

Darcy's Law ◽

Permeability Tensor ◽

Homogenization Theory ◽

Fine Scale ◽

Porous Rock ◽

Coarse Scale ◽

Equivalent Permeability ◽

Discrete Fracture

AbstractA numerical procedure for the evaluation of equivalent permeability tensor for fractured vuggy porous media is presented. At first we proposed a new conceptual model, i.e., discrete fracture-vug network model, to model the realistic fluid flow in fractured vuggy porous medium on fine scale. This new model consists of three systems: rock matrix system, fractures system, and vugs system. The fractures and vugs are embedded in porous rock, and the isolated vugs could be connected via discrete fracture network. The flow in porous rock and fractures follows Darcy’s law, and the vugs system is free fluid region. Based on two-scale homogenization theory, we obtained an equivalent macroscopic Darcy’s law on coarse scale from fine-scale discrete fracture-vug network model. A finite element numerical formulation for homogenization equations is developed. The method is verified through application to a periodic model problem and then is applied to the calculation of equivalent permeability tensor of porous media with complex fracture-vug networks. The applicability and validity of the method for these more general fractured vuggy systems are assessed through a simple test of the coarse-scale model.

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The Microwave Permeability of a Ferrite-Filled Parallel-Plate Transmission Structure

Canadian Journal of Physics ◽

10.1139/p73-326 ◽

1973 ◽

Vol 51 (23) ◽

pp. 2495-2497

Author(s):

C. K. Campbell

Keyword(s):

Parallel Plate ◽

Effective Permeability ◽

Phase Shifter ◽

Permeability Tensor ◽

Ferrite Phase ◽

Circularly Polarized ◽

Polarized Waves ◽

Transmission Structure ◽

Microwave Permeability

With the aid of a phasor diagram it is shown that the scalar effective permeability μe = (μ2 − K2)/μ of a parallel-plate longitudinally magnetized microwave ferrite phase shifter may be simply obtained in terms of four circularly polarized waves relating to the permeability tensor eigenvalues μ + K and μ − K.

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A predictive model for the permeability tensor of magnetized heterogeneous materials

IEEE Transactions on Magnetics ◽

10.1109/tmag.2004.837755 ◽

2005 ◽

Vol 41 (1) ◽

pp. 17-23 ◽

Cited By ~ 9

Author(s):

P. Queffelec ◽

D. Bariou ◽

P. Gelin

Keyword(s):

Predictive Model ◽

Heterogeneous Materials ◽

Permeability Tensor

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Calculation of Magnetization and Permeability Tensor of a Partially Magnetized Cylindrical Ferrite Resonator

IEEE Magnetics Letters ◽

10.1109/lmag.2016.2532319 ◽

2016 ◽

Vol 7 ◽

pp. 1-4 ◽

Cited By ~ 3

Author(s):

Tae-Wan Kim ◽

Byeong-Yong Park ◽

Seung-Young Park ◽

Seong-Ook Park

Keyword(s):

Permeability Tensor ◽

Ferrite Resonator

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Calculation of permeability tensor of fractured rock mass based on statistics and its application in the fissured water around the tunnel

Boundaries of Rock Mechanics ◽

10.1201/9780203883204-140 ◽

2008 ◽

pp. 727-730

Keyword(s):

Rock Mass ◽

Fractured Rock ◽

Permeability Tensor ◽

Fractured Rock Mass

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Formability of laser welded steel/magnesium dissimilar metal with Sn powder-adhesive interlayer

Materials Science-Poland ◽

10.2478/msp-2021-0014 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Tao Tao ◽

Jinshui Liu ◽

Dianwu Zhou ◽

Youruiling Yan ◽

He Zhou

Keyword(s):

Magnesium Alloy ◽

Molten Pool ◽

Adhesive Layer ◽

Metal Vapor ◽

Fusion Welding ◽

Columnar Dendrite ◽

Laser Fusion ◽

Welded Steel ◽

X Ray ◽

Finite Element Software

Abstract The exploratory experiments of laser fusion welding with Sn powder and the automotive adhesive addition were conducted for DP590 dual-phase steel and AZ31B magnesium alloy in an overlap steel-on-magnesium configuration. The characteristics of metal vapor/plasma were analyzed by collecting and analyzing plasma shape and welding spectra. The microstructure of the welded was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS). The temperature field distribution of the joint was simulated by COMSOL finite-element software. The results showed that the transfer of heat from steel to the magnesium alloy is hindered by the adhesive layer, which is conducive to the simultaneous melting of steel and magnesium with large differences in melting and boiling points. In addition, the width of the molten pool increases, but the depth is shallow on the magnesium side. Meanwhile, the recoil pressure induced by the splashing of the molten pool reduces, and the surface quality of the weld is improved. Some intermetallic compounds (IMCs), such as FeSn, Fe1.3Sn, and Fe3Sn, are formed inside the molten pool, while columnar dendrite Mg2Sn phase is also produced. The presence of these phases helps realize the bidirectional metallurgical bonding of steel/magnesium dissimilar metals.

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