Original Research the use of a Neural Network Classifier of Material Facture Criteria for the Rational Choice of the Method for Cutting of Rolled Stocks

To select a rational method for cutting of rolled stocks made from materials with different physical and mathematical properties, an engineer must have the tools to make such a choice. For this, it is proposed to use the well-known synergistic material fracture criteria. In order to find the most informative system of synergetic criteria allowing to classify materials authentically by their fracture sensitivity, the software was developed. It allows to solve the clustering problem in a multidimensional space of parameters and present the obtained information in a visual form using self-organizing Kohonen maps. The cluster analysis of the synergetic criteria of fracture material was carried out. The most informative criterion among the ones characterizing the mechanical properties of steels is the «offset yield strength», among the synergistic ones – «scale criterion». At the same time, among the traditional mechanical features of steels, a set allowing to classify materials with a given integrity by their cutting sensitivity has not been found. It was established that the synergistic criteria: «crack propagation criterion» and «brittleness criterion» are basic informative features. When adding any of the remaining complex criteria («crack nucleation criterion» or «scale criterion»), they form the most informative sets of minimal power, providing the classification of materials by their cutting sensitivity with a given integrity. In order to obtain high quality billets at a minimum conversion cost, recommendations were developed for choice of the method for cutting of rolled stocks in magnitude of criteria values: «crack propagation criterion» and «brittleness criterion». To cut materials «in plastic state», the cutting with a shear should be used, specifically – a closed cut-off scheme or an incompletely closed cut-off scheme with an active transverse clamp or a cut-off scheme with a differentiated rolling clamp. If increased requirements are imposed on the geometric accuracy of the billets, it is recommended to use complex blanking and cutting processes. For cutting materials «in elastoplastic state» there are good reasons to use a cut with a shear, and in particular – an incompletely closed cut-off scheme with an active and passive transverse clamp. Closer to the class interval, it is possible to apply cold bend breaking with the application of an effective stress concentrator. Cold bend breaking should be used to cut «brittle» materials. The carried out experiments confirmed the adequacy of theoretical conclusions and recommendations on the choice of a rational method for cutting of the rolled stocks to obtain high quality billets.

A New Family of Boolean Functions with Good Cryptographic Properties

In 2005, Philippe Guillot presented a new construction of Boolean functions using linear codes as an extension of the Maiorana–McFarland’s (MM) construction of bent functions. In this paper, we study a new family of Boolean functions with cryptographically strong properties, such as non-linearity, propagation criterion, resiliency, and balance. The construction of cryptographically strong Boolean functions is a daunting task, and there is currently a wide range of algebraic techniques and heuristics for constructing such functions; however, these methods can be complex, computationally difficult to implement, and not always produce a sufficient variety of functions. We present in this paper a construction of Boolean functions using algebraic codes following Guillot’s work.

A Cohesive-Zone Model for Simulating Hydraulic-Fracture Evolution within a Fully Coupled Flow/Geomechanics-Simulation System

Summary A modular multiphysics reservoir-simulation system is developed that has the capability of simulating multiphase/multicomponent/thermal flow, poro-elasto/plastic geomechanics, and hydraulic-fracture evolution. The focus of the work is on the full-physics hydraulic-fracture-evolution-simulation capability of the multiphysics simulation system. Fracture-growth computations use a cohesive-zone model as part of the computation of fracture-propagation criterion. The cohesive-zone concept is developed using energy-release rates and cohesive stresses. They capture the strain-softening behavior of deforming porous material consistent with real-life observations of poro-plastic deformation. Thus, they can be reliably used within both poro-elastic and poro-plastic geomechanics applications, unlike the conventional stress-intensity-factor-based fracture-propagation criterion. The partial-differential equations (PDEs) that govern the Darcy-scale multiphase/multicomponent/thermal flow, poro-elasto/plastic geomechanics, hydraulic-fracture evolution, and laminar channel flow in the fracture are tightly coupled to each other to give rise to a numerical protocol solvable by the fully implicit method. The ensuing nonlinear system of equations is solved by use of a novel adaptively damped Newton-Raphson method. Example fully coupled single-phase isothermal-flow, geomechanics, and hydraulic-fracture-growth simulations are analyzed to demonstrate the predictive power of the simulation system. Numerical-model predictions of fracture length/radius and width are validated against analytical solutions for plane-strain and ellipsoid-shaped fractures, respectively. Results indicate that the simulation system is capable of modeling hydraulic-fracture evolution accurately by use of the cohesive-zone model as the propagation criterion. We also simulate and explore the sensitivities around a real-life hydraulic-fracture-growth problem by fully accounting for the thermal-, multiphase-, and compositional-flow effects.

Numerical modeling of liquid CO2 phase transition blasting based on smoothed particle hydrodynamics algorithm

Liquid CO2 phase transition blasting is a physical blasting method to enhance permeability through liquid CO2 phase transition expansion. To study the propagation criterion of fractures during blasting, the energy of phase transition blasting is evaluated through the thermodynamic equation by studying the action process of the liquid CO2 blasting, thus obtaining the scope of the smash zone and crack zone as well as the propagation criterion of fractures under the effect of high pressure gas. The gas blasting model for a coal body is established based on the SPH algorithm, thus obtaining the criteria for formation of the smash zone and for generatio and propagation of the crack zone. Moreover, the radius of phase transition blasting is surveyed onsite by the peephole method. It is shown that the explosive energy of the MZL-51/2000 phase transition blasting equipment with a release pressure of 270 MPa is 1510 kJ. The coal body is crushed by the high pressure CO2 percussive drilling, forming the smash zone. Meanwhile, fractures are generated around the smash zone. With the expansion and migratio of the gas, the fracture will further grow into a crack zone. The fracture inside the coal body goes through four states: rapid, slow, rapid, and then slow again. According to field surveys, the blasting radius of the MZL-51/2000 equipment with loaded liquid of 1.8 kg is approximately 3 m.