Applied Mechanics and Materials Vols. 725-726

Abstract: The paper presents the results of experimental studies and numerical simulation of straining and failure of reinforced concrete folded-plate roof structures in limit and out-of-limit states performed on models and real structures, taking into account the combined mechanical loads and environmental actions. The results of the study show that in the process of reconstruction design for concrete prismatic roof structures of operated industrial and public buildings, along with the traditional limit state methods of calculation it is reasonable to carry out a residual strength reserve analysis.

Abstract: The work explores feasibility of 3D finite element modeling (FEM) to study the effective linear properties of porous brittle material microstructures represented by a uniform cubic mesh. Both artificial virtually generated and real 3D tomography specimens are considered in this work. A method for assessment of the critical value of tomography resolution is proposed. A method to build approximations of the linear effective structure properties of interest at virtually zero FE size is developed. The methods do not have to be associated with mechanical modeling only but can be applied in some other cases, e.g. effective thermal conductivity or effective permeability calculations.

Abstract: The influence of the crystallographic orientation, the level of axial strain and the test temperature on the progressive cross-section ellipticity of single crystal samples under uniaxial tension is analyzed in order to improve axial strain measurement in experiments. The direct three-dimensional finite element modeling of elasto-plastic deformation process of single-crystal initially cylindrical samples is used with taking into account finite strains, slip mechanisms and necking.

Abstract: This work is devoted to the research of mechanical and strength properties of polymer composite material with short carbon fibers produced by injection molding technology. The material is PEEK90HMF20 with 20 % of carbon fibers mass fraction and based on polyether ether ketone (PEEK) polymer matrix. Mechanical and strength properties were researched on samples that had been cut from molded plates. A set of tension tests was performed and stress-strain diagrams of samples with different orientation in relation to the global direction of injection were obtained. Two-step homogenization procedure and pseudo-grains failure model were used to describe composite material behavior. The material model parameters were calibrated with experimental data by means of reverse-engineering procedure. Finite element simulation of tension tests was performed to check the quality of built model from the point of view of its ability to predict failure.

Abstract: At the moment a problem of fracture and lifetime estimation for piezoelectric materials is not completely solved. The paper considers fundamentals of linear fracture electromechanics, fracture parameters and fracture criteria. The main difference from linear mechanics is crack face boundary conditions taking into account relative permeability of media inside the crack gap and coulomb traction. Different types of crack face boundary conditions and their numerical implementation are described. The paper presents results of finite element modeling of fracture toughness experiments on the compact tension specimens under combined electromechanical loading. Different types of crack face boundary conditions were tested and comparison of fracture parameters and fracture criteria was carried out.

Abstract: During operation of transport and maneuverable gas-turbine units, there are crack formation in turbine disc rims what exerted by thermomechanical cycling loads. For in-depth study of these problems we have to use theories of plasticity and creep which form the basis for determining the complex stress-strain state in the stress concentration zone for disc rims, and a modern failure criterion which can predict lifetime under conditions of simultaneous plastic and creep strain accumulation. There is a finite-element method (FEM) that allows us to evaluate the stress-strain state in a stress concentration zone for a non-elastic material behavior. With plasticity and creep theories, it is possible to determine local strain quiet reliable by FEM.

Abstract: The time-dependent effects of piezoceramic material under the constant electric field are analyzed. The new rate-dependent ferroelectroelastic phenomenological model is proposed and compared with known models and experimental data.

Abstract: In this paper it was performed curve negotiation analysis of three axle bogie of locomotive type JŽ 461. This locomotive has large distance between first and middle i.e. middle and last axle, which leads to increased lateral forces during curve negotiation. Final result might be widening of track gauge in curves with small radius. This paper points that Infrastructure Manager must take into account vehicle performances and type of track when defines track gauge in curves.

Abstract: Modern business strategies and quality of business environment are conditions for increasing competitiveness of companies in the civil engineering sector. Basic idea of Customer Relationship Management (CRM) is to shift the focus from the product to the buyer and in that way to build quality, long term and profitable relations. Products and services must be adjusted to the demands and specifications of certain clients. CRM is not a technology but a business concept, business philosophy. Basic aim of CRM in the civil engineering sector is gaining and keeping customers with the biggest purchasing potential. The article show that the implementation of the CRM system is in the direct positive correlation with business results of the companies from the civil engineering sector. In order to make the CRM strategy successful, it is necessary to determine appropriate strategy of creating long term, sustainable and profitable relationships with buyers, then to adjust business processes of the company and if necessary to adapt the organizational structure to creating the environment which is totally focused on the buyer.

Abstract: In article is offered the method of calculation of a frontal and rhythmical stream, at which initial temporary operating conditions of crews periodically repeat (under a condition of continuous use of resources). It allows to provide the demanded duration of performance of work and the minimum quantity of resources.