On the Local Stress Fields in Inhomogeneous Media Determined by the Acoustic Emission Method

Physics of the Solid State - Local internal stresses in two natural inhomogeneous materials differing in the structure have been calculated using analysis of pauses between acoustic emission...     

Dynamics of the Surface Morphology of a Tungsten Foil under Load

Physics of the Solid State - The dynamics of changes in the surface morphology of recrystallized tungsten foil under the action of uniaxial tension was studied in situ by the methods of low-energy...     

Kinetic theory of strength and a self-organized critical state in the process of fracture of materials

The basic principles of the Zhurkov kinetic approach are analyzed in light of the modern idea of self-organization of nonlinear systems under nonequilibrium conditions. It is indicated that the final state before fracture can be described in terms of the model of a self-organized critical state.     

Numerical characteristics of recurrence plots as applied to the evaluation of mechanical damage in materials

The response of a material with a random uniform distribution of pores to a sound impulse was studied. The behavior of the numerical characteristics of the recurrence plots (RP) of the normal displacement vector component depending on the degree of damage was investigated. It was shown that the recurrence quantification analysis (RQA) parameters could be very informative for sonic fault detection.     

Statistical Regularities of Formation of a Main Crack in a Structurally Inhomogeneous Material under Various Deformation Conditions

Physics of the Solid State - The peculiarities of the formation of a main crack in the Westerly granite samples under quasistatic uniaxial compression without any lateral upthrust have been studied...     

Wavelet transform as a method for studying the fractal properties of the surface of amorphous metals under mechanical load

The effect of mechanical tension on the multifractal characteristics of the lateral surface of a Fe₇₇Ni₁Si₉B₁₃ amorphous alloy is studied by scanning tunneling microscopy (STM). It is established that, at small loads, the surface is smoothed out much as a crumpled sheet of paper is smoothed out under tension. With an increase in the load, there appears a tendency to the formation of a fractal structure on the surface.     

Formation of different surface reliefs of metallic glasses under mechanical stress

The micro- and nanoreliefs of loaded lateral surfaces and fracture surfaces of foils of the Fe₇₇Ni₁Si₉B₁₃, Fe₅₈Ni₂₀Si₉B₁₃, and Fe₇₀Cr₁₅B₁₅ amorphous alloys have been investigated using scanning tunneling and atomic force microscopy. The isotropic and anisotropic surface reliefs have been examined. The fractal dimensions of the surfaces of loaded specimens and the fracture surfaces along and across the direction of crack propagation have been estimated using the box counting method. Fractal characteristics of the surfaces, such as the Hölder exponent and the half-width of the singularity spectrum, have been calculated using the wavelet transform method. It has been found that, on the topographies with a clearly pronounced anisotropy of the relief, the surface is fractal in only one direction, and the surface is fractal in two directions on the topographies with a less pronounced anisotropy of the relief. The fractal characteristics of the lateral surfaces and the fracture surfaces with allowance made for their anisotropy have close values. It has been shown that the formation of two types of fracture surfaces is adequately described in terms of the model of a cellular automaton.     

Detection of the fracture zone by the method of recurrence plot

Recurrence plots (RPs) and recurrence quantification analysis (RQA) characteristics for the normal component of the displacement vector upon excitation of a defect steel plate by a sound pulse are analyzed. Different cases of spatial distribution of defects (uniform and normal) are considered, and a difference in the RQA parameters in these cases is revealed.     

Formation of power-law size distributions of defects during fracture of materials

The experimental data on the surface relief of loaded ribbons of an amorphous alloy have been obtained. The distributions of surface defects formed under loading have been analyzed using the wavelet transform and box counting method. Moreover, the data on the time accumulation of microcracks in the volume of a loaded granite specimen have been examined. It has been shown that power-law size distributions of defects (scaling) appear on the surface and in the bulk before fracture. It has been revealed that the appearance of the power-law distributions is one of the indications of the formation of the self-organized critical state. The formation of the self-organized critical state in the bulk and on the surface of the material has been considered. It has been established that the formation of the self-organized critical state precedes the fracture of a solid.