Finite-element modeling of the interaction of reinforcement with concrete matrix

A finite-element model of a reinforced concrete beam with rebars modeled by a 3-D deformable body has been developed. An analysis of the stress-strain state of the beam allowed us to determine the stress distribution on cross sections of the rebars and the location of zones with cracks in concrete. It is found that the break of bond between the reinforcement and concrete goes outside the areas of intensely cracked concrete matrix. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 309–316, May–June, 2008.     

Mechanical properties of a composite with a carbonized matrix

The effect of reinforcement schemes that differ in the magnitude of the disorientation angle of neighboring filler layers on the mechanical properties of a "carbon-carbon" composite under extension, compression, or bending is shown.Translated from Mekhanika Polimerov, No. 2, pp. 235–240, March–April, 1976.     

The effect of a porous polyethylene matrix on the structure and mechanical and deformational properties of electroactive composites

Two types of new electroactive composite systems based on elastic substrates (porous polyethylene films) have been elaborated. The systems of the first type are composed of electroconductive polymers (polypyrrole and polyaniline) obtained by in situ oxidative polymerization of their monomers on porous polyethylene substrates. The composites of the second type contain a cross-linked polyelectrolyte, and they were prepared by polymerization of acrylic acid with a macromolecular cross-linker on the porous substrates. The mechanical properties and the deformational behavior of the porous films and composites have been investigated and analyzed. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 825–838, November–December, 2006.     

Computer modeling of dynamics of damage cumulation in the ductile matrix of a fiber-reinforced composite

Conclusions On the basis of the present results together with other previously obtained data [12, 14, 15, 18, 19] it can be assumed that the problem of deformation and failure [20, 21], which is often reduced to explaining the problem of whether failure is the result of deformation or its cause, has resulted from attempts to transfer the macroconsiderations of continuum to the atomic discrete level where the strain (shear accumulation) and failure (cumulation of ruptures) are interrelated to such an extent that their contraposition is of artificial nature. For example, the fluctuation rupture of the bond on the free boundary of the crystal causes formation of a dislocation and shearing [15], and shearing in the form of twinning leads to rupture of bonds and formation of a crack nucleus (see Fig. 1c). For analysis of failure, it is at present insufficient to use only dislocation [22] or only kinetic [21] considerations. As mentioned in [20], in the physics of failure it is necessary to examine all the objects examined in the physics of plasticity and, in addition to this, even more complicated objects. Attempts to simplify the problem proved to be unsuccessful and, consequently, the correct method of solving the problems of the physics of strength should be based on developing the methods of physics of strength up to analysis of atomic mechanisms of damage cumulation [20]. Molecular dynamics represents such a method of examining failure which makes it possible to change to the atomic level [10].Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 973–976, November–December, 1987.     

The supramolecular structure of polymers and its effect on their mechanical properties

A study is made of the conditions of formation of various supramolecular structures in polymers and their effect on the mechanical properties. The nonuniformity and instability of the structure, and hence of the mechanical properties, may be controlled by means of artificial crystallization nuclei.Mekhanika polimerov, Vol. 1. No. 1. pp. 5–16, 1965The research was carried out at the L. Ya. Karpov Physicochemical Research Institute.     

Effect of curvature of the reinforcement on the mechanical and thermophysical properties of a composite

The elastic constants and thermal expansion coefficients of a composite consisting of a matrix with low elastic properties and exceptionally stiff fibers have been experimentally determined. The curvature of the reinforcement in the specimens has been investigated. The results of the experiments are compared with the corresponding theoretical characteristics. The calculations are based on a model with an ideal arrangement of the fibers [4] and a model that takes the curvature of the reinforcement into account [5, 6].Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1036–1039. November–December, 1971.     

Analytic properties of the scattering matrix of many particle systems

We generalize the previous results on a meromorphic continuation of the scattering matrix for N particle systems. Our proofs seem to be much simpler than those given before.Dedicated to the dear memory of david Milman     

Effect of mineral fillers on properties of composite matrix material

The influence of mineral fillers on thermomechanical properties of matrix material of composites is investigated. Different methods to determine elastic properties and thermal expansion coefficients of composite materials have been considered and compared. Injection moulded polyester samples containing varying concentrations of talc filler are tested and properties such as Young 's modulus, thermal expansion coefficients, and volumetric shrinkage during cure are measured. Results obtained by theoretical models and from experiments are compared and discussed.To be presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October 1995).Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 435–445, July–August, 1995.     

Macroscopic mechanical properties of metal foam in dependence on the inhomogenities of the mesoscale

In this contribution, a way of simulating the influence of the mesoscopic irregular structure of metal foams on the macroscale is shown. To this end, mesoscopic periodic volume elements of a foam are derived in order to compute the mechanical properties including the effects of inhomogenities like imperfections, irregular structure and varying cell wall thicknesses. With the help of these volume elements, which are analysed via the finite element method, and their varying mechanical properties, a local varying stiffness can be computed and inserted into the macromechanical model. In this way the propagation of uncertainities from the mesoscale to the macroscale can be assessed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

DC-NMF: nonnegative matrix factorization based on divide-and-conquer for fast clustering and topic modeling

The importance of unsupervised clustering and topic modeling is well recognized with ever-increasing volumes of text data available from numerous sources. Nonnegative matrix factorization (NMF) has proven to be a successful method for cluster and topic discovery in unlabeled data sets. In this paper, we propose a fast algorithm for computing NMF using a divide-and-conquer strategy, called DC-NMF. Given an input matrix where the columns represent data items, we build a binary tree structure of the data items using a recently-proposed efficient algorithm for computing rank-2 NMF, and then gather information from the tree to initialize the rank-k NMF, which needs only a few iterations to reach a desired solution. We also investigate various criteria for selecting the node to split when growing the tree. We demonstrate the scalability of our algorithm for computing general rank-k NMF as well as its effectiveness in clustering and topic modeling for large-scale text data sets, by comparing it to other frequently utilized state-of-the-art algorithms. The value of the proposed approach lies in the highly efficient and accurate method for initializing rank-k NMF and the scalability achieved from the divide-and-conquer approach of the algorithm and properties of rank-2 NMF. In summary, we present efficient tools for analyzing large-scale data sets, and techniques that can be generalized to many other data analytics problem domains along with an open-source software library called SmallK.