От Редакционного Совета

Номер приурочен столетней годовщине выпуска первого номера журнала "Известия Томского технологического института"

Time-Delay and Doppler Tests of the Lorentz Symmetry of Gravity

Modifications to the classic time-delay effect and Doppler shift in general relativity (GR) are studied in the context of the Lorentz-violating standard-model extension (SME). We derive the leading Lorentz- violating corrections to the time-delay and Doppler shift signals, for a light ray passing near a massive body. It is demonstrated that anisotropic coefficients for Lorentz violation control a time-dependent behavior of these signals that is qualitatively different from the conventional case in GR. Estimates of sensitivities to gravity-sector coefficients in the SME are given for current and future experiments, including the recent Cassini solar conjunction experiment

Multilevel modelling of mechanical properties of textile composites: ITOOL Project

The paper presents an overview of the multi-level modelling of textile composites in the ITOOL project, focusing on the models of textile reinforcements, which serve as a basis for micromechanical models of textile composites on the unit cell level. The modelling is performed using finite element analysis (FEA) or approximate methods (method of inclusions), which provide local stiffness and damage information to FEA of composite part on the macro-level

Ductility of coupled shear walls

In this project the strength and behaviour of coupled shear walls subjected to seismic type of lateral load are examined. The sensitivity of shear wall response to changes in relative stiffnesses of beams and walls, and the effects of cracking are studied. Using a finite difference approximation the application of laminar analysis is extended to coupled walls with variation in properties of beams and walls with height, different boundary conditions, different pattern of loading and two or more rows of openings. Theoretical approaches are suggested for the estimation of strength and post-cracking stiffnesses of beams and walls. Using these approaches, with the aid of finite difference approximation of the laminar technique, the history of the shear wall's behaviour is followed by an incremental non-linear elasto-plastic analysis which exposes the ductility requirements of beam and wall hinges and reveals the sequence of their yielding. Two quarter full size seven storey reinforced concrete coupled shear wall models, with differently reinforced coupling beams, have been tested under static reversed cyclic loading to simulate seismic effects. The experiments revealed that carefully designed and detailed shear walls can possess adequate ductility to give the desirable protection against catastrophic ground shaking. The shear wall model with diagonally reinforced beams exhibited superior stiffness, ductility and energy dissipation characteristics. Finally, the significant findings of this investigation have been translated into design recommendations for coupled shear wall structures

Eliminating the volume redundancy of embedded elements and yarn interpenetrations in meso-finite element modelling of textile composites

© 2015 Elsevier Ltd. All rights reserved. Embedded elements (EE) present a potential for an effective solution of interpenetration of yarn volumes, excluding the need for creation of continuous meshes in the matrix and in the reinforcement. The paper investigates application of contact algorithm to eliminate the interpenetration and introduces a stiffness correction in volumes made redundant because of coincidence of the embedded and the host meshes. Different fibre configurations (two intersecting yarns and a 3D woven reinforced composite) are considered and a good agreement is observed between the continuously meshed and EE models in prediction of the homogenised properties and strain-stress profiles in loaded unit cells.status: publishe

Influence of oxidation on steel fiber yarn and knitted fabric properties

Fine steel fibers are spun into yarns and then knitted into fabric, which is used, among other applications, as a high resistance separation material in forming of automotive glass. In press bending, the glass sheet is first heated to temperature of about 650°C and subsequently vacuum pressed on a mold covered by steel fiber knitted fabric. This high temperature changes the surface of fibers by oxidation, which influences mechanical properties of yarn and fabrics. The paper investigates interrelation between change of yarn and fabric properties caused by oxidation. Higher tensile resistance of the oxidized fabric corresponds to higher bending stiffness and higher friction of the oxidized yarn. The change of the fabric biaxial tension behavior influences the optical quality of the formed glass.status: publishe

Model of shear of woven fabric and parametric description of shear resistance of glass woven reinforcements

Forming simulations of textile preforms require a description of the shear resistance of the preform plies. Experimental determination of the shear diagrams is time consuming, costly and requires highly qualified personnel. Typical glass rovings exhibit quite consistent behaviour, described by diagrams for bending, compression and tension, in function of linear density of the rovings. Based on these representative diagrams, a parametrical study of the shear resistance of glass preforms has been carried out, using a model, which accounts for different sources of the fabric resistance to shear: friction, compression of the yarns, yarn (un)bending, Possible simultaneous action of shear and (pre)tension is taken into account. The model (validated against experimental data) generates shear diagrams for plain, twill and 5-harness satin square fabrics. The diagrams were then processed to create analytical expressions of the shear diagrams: T = T₀ + T₁ tanªγ, where T is the shear force, γ is the shear angle, a, T₀, and T₁ are parameters, tabulated as functions of yarn linear density, fabric tightness and pretension. The value of α was found to be close to 2 in all the cases. The resulting family of shear diagrams was verified against experimental data.status: publishe

Virtual textile composites software WiseTex: Integration with micro-mechanical, permeability and structural analysis

The internal geometry of textile reinforcements is an important factor of the reinforcement performance during composite manufacturing and in the service life of the composite material. When a 3D-shaped composite part is concerned, the reinforcement is locally deformed (compressed, stretched and sheared), and any model describing the internal geometry of the reinforcement should account for this deformation. The software package WiseTex implements a generalised description of internal structure of textile reinforcements on the unit cell level, integrated with mechanical models of the relaxed and deformed state of 2D- and 3D-woven, two- and three-axial braided, weft-knitted and non-crimp warp-knit stitched fabrics and laminates. It is integrated with modelling of resin flow, micro-mechanical calculations of properties of textile based composites and micro-macro analysis of composite parts, finite element models and virtual reality software. The paper describes this family of models, which use a unified description of the geometry of the reinforcement unit cell.status: publishe