Study of strength properties of ceramic composites with soft filler based on 3D computer simulation

The movable cellular automaton method which is a computational method of particle mechanics is applied to simulating uniaxial compression of 3D specimens of a ceramic composite. Soft inclusions were considered explicitly by changing the sort (properties) of automata selected randomly from the original fcc packing. The distribution of inclusions in space, their size, and the total fraction were varied. For each value of inclusion fraction, there were generated several representative specimens with individual pore position in space. The resulting magnitudes of the elastic modulus and strength of the specimens were scattered and well described by the Weibull distribution. We showed that to reveal the dependence of the elastic and strength properties of the composite on the inclusion fraction it is much better to consider the mathematical expectation of the corresponding Weibull distribution, rather than the average of the values for the specimens of the same inclusion fraction. It is shown that the relation between the mechanical properties of material and its inclusion fraction depends significantly on the material structure. Namely, percolation transition from isolated inclusions to interconnected clusters of inclusions strongly manifests itself in the dependence of strength on the fraction of inclusions. Thus, the curve of strength versus inclusion fraction fits different equations for a different kind of structure

Probabilistic approach for analysis of strength of ceramics with different porous structure based on movable cellular automaton modeling

Movable cellular automaton method which is a computational method of particle mechanics is applied to simulating uniaxial compression of 3D porous ceramic specimens. Pores were considered explicitly by removing automata selected randomly from the original fcc packing. Distribution of pores in space, their size and the total fraction were varied. For each values of porosity there were generated several represented specimens with individual pore position in space. The resulting values of elastic modulus and strength of the specimens were scattered and well described by the Weibull distribution. We showed that to reveal dependence of the elastic and strength properties on porosity it is much better to consider not average of the values for the specimens of the same porosity, but the mathematical expectation of the corresponding Weibull distribution. It is shown that relation between mechanical properties of the material and its porosity depends significantly on pore structure. Namely, percolation transition from closed porosity to interconnected pores strongly manifests itself on strength dependence on porosity. Thus, the curve of strength versus porosity fits different equations for different kind of pore structure. Composite ceramics which pores are filled by plastic filler shows the similar behavior

Numerical analysis of the stress state and fracture of porous ceramics at the mesolevel

The paper is devoted to the numerical investigation of inelastic deformation and fracture of porous alumina ceramics. A structural model of the mesovolume is developed with the use of an experimental scanning electron microscopic image. The mechanical behavior of the matrix is described by two constitutive models from plasticity theory and continuum damage mechanics. Uniaxial tension and compression of the mesovolume are numerically simulated in a two-dimensional formulation. The features of fracture patterns in the cases of the two constitutive models adopted are analysed. Effective mechanical characteristics of the studied ceramics are determined from the performed calculations. The results obtained can be used to specify the characteristics of the Drucker–Prager material for macroscopic modeling

Numerical simulation of slow deformation perturbations in fault zones

Over the past half a century, the concept of slow deformation waves of the Earth has been developed and widely discussed in the Earth sciences. The velocity of slow waves is considered to be 5–6 orders of magnitude less than the velocity of sound and 7–8 orders of magnitude greater than tectonic flows. Analyzing and classifying various manifestations of slow deformation waves in the geomedium accumulated over forty years V. G. Bykov identifies two types of autowaves in his review—inter-fault and intra-fault. Here, the process of generation and propagation of slow deformation disturbances between two faults in an elastoplastic medium is studied numerically. The faults were defined as narrow elongated soft areas inclined to the axis of the load application. Just in these faults plastic deformation was permitted to generate. The simulations proved that the fronts of deformation waves head towards each other at approximately the same velocities, their shapes being close to planar but slightly curved

Analysis of stress and strain in the tetrachiral metamaterial with different kinds of unit cell connections

Metamaterials are artificially created materials whose unique properties are due to their structure rather than the chemical composition of the base material. The unit cells form the basis of a metamaterial. When creating the metamaterial, one should distinguish the methods of connecting its unit cells. The paper considers two methods of unit cell connection in a threedimensional metamaterial—joining and overlapping. Connecting the cells in the metamaterial by joining method may lead to a differently directed rotation of the rings, which will have a negative effect on the entire sample of the metamaterial. In the case of the other connection method, there is no differently directed rotation, so it would appear reasonable that creating a sample of a metamaterial by this method would achieve greater values of twist. The asymmetric deformation pattern is investigated in this work. For the two methods considered, also different results were obtained on stress distribution and strain localization in the sample under uniaxial loading. In the system of two cells in the metamaterial obtained by the joining method, an additional center of localization of deformation occurs at the junction of the two edges, which make up the tetrachiral elemen

Numerical analysis of the state of stress and strain in the Yenisei Ridge based on the regional tectonic state in the Asian continent

The paper presents the calculation of modern tectonic flow fields in the Yenisei Ridge located on the stable Siberian Craton. At the first stage, we solve the problem of calculating the average field of tectonic flows due to collisional processes at the southern and northeastern margins of the Eurasian Plate with Indian and Arabian and with North American plates, respectively. These calculations clarify the state of stress and the structure of tectonic flows on the territory of the Siberian Craton. The subtraction of the average displacements of the Siberian Craton as a whole in the northeast direction reveals the detailed structure of tectonic flows. Structural models are built along the Batolit-1982 and Shpat geological profiles crossing the Yenisei Ridge. At the second stage, we numerically study the state of stress and strain along these profiles determined by the global tectonics of Central and Southeast Asia, as well as their structural organization and interaction with the neighboring crustal elements

Numerical simulation of mechanical behaviour and prediction of effective properties of metal matrix composites with consideration for structural evolution under shock wave loading

Mechanical behaviour of stochastic metal-ceramic composite materials under shock wave loading was numerically simulated on mesoscopic scale level. Deformation of mesoscopic volumes of composites whose structure consisted of a metal matrix and randomly distributed ceramic inclusions was simulated. The results of numerical simulation were used for numerical evaluation of effective elastic and strength properties of metal-ceramic materials with different values of volume concentration of ceramic inclusions. The values of the effective mechanical characteristics of investigated materials were obtained, and the character of the dependence of the effective elastic and strength properties on the structure of composites was determined. It is shown that the dependence of the values of the effective elastic moduli on the volume concentration of ceramic inclusions is nonlinear and monotonically increasing. The values of the effective elastic limits increase with increasing concentration of the inclusions, however, for the considered composites, this dependence is not monotonic

Study of effect of damage accumulation on stress distribution parameters in mesovolume of biocomposite and its performance characteristics

Abstract—A numerical study of mechanical properties of zirconium ceramic–cortical bone tissue biocomposite has been fulfilled using a multiple-scale approach. Evolution of mesoscopic stress distribution in the components of biocomposite during its deformation has been studied with the assumption of damage accumulation until the macrostrength criterion is fulfilled. It has been shown that the parameters of the laws of distribution change with damage accumulation

Numerical investigation of effective mechanical properties of metal-ceramic composites with reinforcing inclusions of different shapes under intensive dynamic impacts

In the present paper, the results of numerical simulation of high-rate deformation of stochastic metal-ceramic composite materials Al–50% B4C, Al–50% SiC, and Al–50% Al2O3 at the mesoscopic scale level under loading by a plane shock wave are presented. Deformation of the mesoscopic volume of a composite, whose structure consists of the aluminum matrix and randomly distributed reinforcing ceramic inclusions, is numerically simulated. The results of the numerical simulation are used for the investigation of special features of the mechanical behavior at the mesoscopic scale level under shock-wave loading and for the numerical evaluation of effective elastic and strength properties of metal-ceramic composites with reinforcing ceramic inclusions of different shapes. Values of effective sound velocities, elastic moduli and elastic limits of investigated materials are obtained, and the character of the dependence of the effective elastic and strength properties on the structure parameters of composites is determined. The simulation results show that values of effective mechanical characteristics weakly depend on the shape of reinforcing inclusions and mainly are defined by their volume concentration