Implementation of planar 3D hydraulic fracture model in rock with layered compressive stress

Plane 3D model of hydraulic fracture propagation is implemented. Fluid flow inside the fracture, leak-of, rock deformation and breaking are taken into account. Asymptotic solution for tip of semi-infinite plane fracture is used to set boundary conditions for fluid flow problem and to calculate fracture front propagation velocity. Elastic and fluid flow equations are united in one system of nonlinear equations and solved simultaneously by Newton method with analytically calculated Jacoby matrix. The implemented model may be used as a start point for testing various methods of solution of “hydrodynamic-elasticity” problem and improving their convergence speed. Also model can be used for developed hydraulic fracture simulation.

Preparation of (Mo,Nb)Si2 Ternary Alloys by Self−Propagating High−Temperature Synthesis

An experimental study on the preparation of (Mo,Nb)Si2 ternary alloys was conducted by self-propagating high-temperature synthesis method from elemental powder compacts of different stoichiometries. And the combustion mode, combustion temperature, flame-front propagation velocity and product structure were discussed. The results show that (Mo,Nb)Si2 ternary alloys are characterized by an unsteady state combustion mode with a spiral−trajectory reaction front from top to bottom. The combustion temperature and flame−front propagation velocity decrease with the addition of coarse niobium powder. The combustion temperature and flame-front propagation velocity of MoSi2 are 1629K and 3.13mm/s respectively. However, those of (Mo0.8Nb0.2)Si2 alloy are 1460K and 1.97mm/s. The solid solubility of niobium in MoSi2 is less than 2.5at.%, and the combustion synthesis produce still remains Cllb single-phase structure in (Mo1-x,Nbx)Si2(x<0.075) sample. The C40-type structure appears in (Mo0.925,Nb0.075)Si2 compact and the intensity of diffraction peaks of C40-type phase gradually reinforces with the increase of niobium content. Combustion synthesis is an effective technology for producing (Mo,Nb)Si2 ternary alloys.

Binary frontal polymerization: Velocity dependence on initial composition

Frontal polymerization is a mode of polymerization in which a localized zone of reaction propagates through the coupling of thermal diffusion and the Arrhenius dependence of the reaction rate. The dependence of the front propagation velocity on the initial composition has been determined in initially miscible binary systems of a free-radically cured diacrylate and an amine- or cationically cured epoxy resin. A minimum of the velocity as a function of the monomer mole fraction is observed if the two polymerizations occur independently. Excellent agreement with an analytical description was found with the diacrylate and an amine-cured epoxy but not for a diacrylate and a cationically cured one because of the effect of HCl impurities on the peroxide.