Darius Zabulionis

Simulation of Adhesive–Dissipative Behavior of a Microparticle Under the Oblique Impact

The adhesive–dissipative behavior of a microparticle under the oblique impact is investigated numerically and the new discrete element method (DEM)-compatible interaction model is elaborated. The modeling approach is based on the Derjaguin–Muller–Toporov model of normal interaction for the adhesive elastic contact. Adhesion hysteresis is specified by the loss of the kinetic energy governed by the fixed amount of the adhesion work, required to separate two adhesive contacting surfaces. This effect is captured in the new interaction model by adding an additional dissipative force component to normal contact during unloading and detachment. The essential feature of this approach, differing from that of the viscous damping model, is that, according to the proposed method, the amount of the dissipated energy is not influenced by the actual initial velocity during the entire contact. The influence of adhesion on slip friction is reflected by considering the adhesive normal force components in the Coulombs law of friction. The contribution of the adhesion-related dissipation is illustrated by a comparison of the behavior of the attractive–dissipative and attractive–non-dissipative models. The oblique impact of a microparticle on the plane surface at the intermediate impact angle is also investigated numerically. The link between adhesion and friction is supported by the numerical results.

Statistical analysis of design codes calculation methods for punching sheer resistance in column‐to‐slab connections

Abstract This paper analyses the compliance of the design codes calculation methods for punching shear resistance in reinforced concrete slabs STR 2.05.05:2005, E DIN 1045–1, ENV 1992–1‐1 EC 2, prEN 1992–1 [Final draft] EC 2, Model Code CEB‐FIP 1990, BS 8110, ACI 318–99 to the experimental data. It has been analysed whether the difference in the results of the mean punching shear resistance received according to these methods and through experiments is statistically significant, when the level of significance value is 0,05. To analyse the significance of the difference of the means Student t test was used. An analysis was carried out to find out which methods show the least different resistance results from the experimental data. According to this analysis, a classification of methods was made. Student t test was applied to analyse in which methods the ratio between the punching shear resistance results obtained and the punching shear resistance results received through experiment is statistically insigni...

Model for Time-Dependent Stress and Strain Analysis of Layered Composite Element

The authors have proposed a relatively simple and convenient method for engineering purposes that allows one to simulate time-dependent viscoelastic properties of a multilayered composite element subjected to loading along layer joints. The method proposed is found to be of a good coincidence in comparison with the known analytical solution of a two-layered composite element. Numerical analysis is also performed adopting the model proposed for the deformational response of reinforced concrete elements.

A Lattice Model for Elastic Particulate Composites

In the present article, a version of the lattice or spring network method is proposed to model the mechanical response of elastic particulate composites with a high volume fraction of spherical particles and with a much weaker matrix compared to the stiffness of the particles. The main subject of the article is the determination of the axial stiffnesses of the springs of the cell. A comparison of the mechanical response of a three-dimensional particulate composite cube obtained using the finite element method and the proposed methodology showed that the efficiency of the proposed methodology increases with an increasing volume fraction of the particles.

Stress and Strain Analysis of Three-Layer Composites with Interlayer Slip under Hygrothermal Loads

This article deals with the stress and strain state of a three–layer composite material with interlayer slip subjected to hygrothermal loading. The exact solutions in an explicit function form that allows one to determine the stress-strain state and deflection of three–layer composite subjected to hygrothermal loading and by taking this into consideration the interlayer slip is proposed.

THE INFLUENCE OF MORTAR MICROSTRUCTURE ON ITS THERMAL EXPANSION COEFFICIENT

Abstract Thermal strain is one of the factors causing additional stresses in a composite structure. It is necessary to calculate the coefficient of thermal expansion in evaluating thermal strains. According to the research, concrete is a material consisting of three phases: aggregate, interfacial transition zone (ITZ) and cement paste. The article presents the technique which enables the estimation of the thermal expansion coefficient of the mortar consisting of various aggregate fractions and covered with ITZ layer. A parametric study of various ITZ layer characteristics influencing the coefficient of thermal expansion has been carried out in the present paper. It has been determined that dry mortar or concrete could be treated as a material consisting of two components. While evaluating moist mortar or concrete it is necessary to take into account the depth of the ITZ the bulk modulus and the coefficient of thermal expansion.