Search

The relevance of research is driven by the need to expand the possibilities of an explosion action controlling to obtain a rational rock mass fragmentation, the requirements to improve the safety of mining working, as well as the economic feasibility of reducing the loss of minerals and eliminating negative environmental factors of blasting. The paper presents some regularities of the radial air gap value influence for the TNT and ANFO charges on the yield of fractions during geo-environment explosive failure. The investigation were carried out experimentally on compositional models and numerically by the Smoothed Particle Hydrodynamics method (SPH). The article considers the methodological issues of combined application of compositional axisymmetric models and computer simulation for dynamic loading problems solving of the massive to identify patterns of stress localization and rock fragmentation. The research results made it possible to determine the dependences of the change in the middle rock piece and the yield of fines on the radial air gap value. In addition, the influence of the distance to the charge on the yield of the middle rock piece at different explosive densities was established. The developed research methodology makes it possible to determine numerically the influence of various factors on the nature of stress localization and to identify the trigger effect of the geo-environment explosive failure. The results comparison of processing physical experiments and computer simulation shows that the chosen approach ensures the reliability of the research results and turned out to be very useful for analyzing and better understanding the rock massive explosive failure mechanics. The results comparison for physical experiments processing and computer simulation shows that the chosen approach ensures the reliability of the research results and turned out to be very useful for analyzing and better understanding the rock massive explosive failure mechanics. [ABSTRACT FROM AUTHOR]

This work is connected with the problem of the dynamic loading of initially damaged media. The deformable solid medium with a complex internal structure is considered. The process of fracturing can drastically decrease the material stiffness and affect the wave propagation process. The continuum model of solid media with a discrete set of slip planes and nonlinear viscous-plastic contact conditions on them is formulated. It allows to simulate the dynamic behavior of complex media, like composite materials or geological fractured massifs. For a stable numerical solution of a system of differential equations, an explicit-implicit method is derived with an explicit approximation of motion equations and an implicit approximation of the constitutive relations containing a small parameter. To achieve a high precision, the hyperbolic part is solved with the grid-characteristic method on rectangular grids. In this research we compared simulated wavefields with the same ones obtained by the method of explicitly setting crack positions. The results can be useful for the problem of the low impact damage estimation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to explore the possibilities of applying a simple method of the solution of the differential equations of the 2nd order. Such equations describe the behavior of the structure under dynamic load (seismic effects, starting of rotating machines). A friction damper was developed at the Fraunhofer-Institut für Holzforschung in Braunschweig in order to limit the oscillation of the structure. Here is analyzed the mathematical model where hysteresis behavior (energy dissipation) is described. The model is basically based on a strongly non-linear stiffness change of the joints. [ABSTRACT FROM AUTHOR]

The destruction of thick-walled cylindrical shells under explosive loading is a typical example of a problem that cannot be solved without taking into account the heterogeneity of the material’s internal structure. A probabilistic approach to numerical simulation of dynamic fracture is described. Fragmentation spectrum of shells fracture under explosive loading (flat 2D modeling) is compared for different distributions of the strength properties. Using numerical simulation results, it is shown that increasing of strength properties dispersion leads to an increase in the spectrum part of medium and large fragments. It is shown that the fragmentation spectrum is determined mainly by dispersion of the distribution law, but not its shape. [ABSTRACT FROM AUTHOR]

Bulk layers of metal balls are used as damping elements, protecting the structure from impulsive influences. Previously obtained experimental diagrams are non-linear and irreversible. Numerical modeling of the quasistatic and dynamic compression of a symmetrical fragment of a granular layer for one of the variants of regular packing of lead balls - cubic packing. The contact three-dimensional problem was solved by the finite element method using the multilinear plasticity model with kinematic hardening. Dynamic compression was carried out by an absolutely rigid plane, moving at a constant speed for a given interval of time. The behavior of the obtained numerical compression diagrams corresponds qualitatively to the behavior of the experimental ones. It is shown that two main factors exert a significant influence on the difference in the behavior of quasistatic and dynamic diagrams of deformation of a porous layer: a limited time of action of the loading pulse in the dynamic regime and a difference in the dynamic diagram of the deformation of the base material from the quasistatic diagram. [ABSTRACT FROM AUTHOR]