Applied Mechanics and Materials Vol. 732

Abstract: Special industrial application of fiber-cement composites is currently one important issue of concrete industry and research activity. The field of refractory and high-temperature resistance materials is very large and contains the cement composites too. Hydrothermal curing together with using aluminous cement with refractory basalt aggregates and fibers shows high potential for its applications in high temperature. These composite is characterized by compressive strength over 140 MPa and tensile strength in bending 12 MPa (investigated on specimens 40 x 40 x 160 mm). After exposure to temperature 1000 °C these parameters are 60 MPa in compression respective 6 MPa in bending. Achieved values are significantly higher than in the case of laboratory curing condition and there are suitable especially for prefabricated fire resistance cladding or other special application in the industry.

Abstract: Finite-element (FE) analysis is important instrument for prediction of plastic car bumper tests. Accuracy of FE analysis depends on accuracy of material input data. It has developed experimental methodology for identification of mechanical properties. The methodology leads to more accurate material input data for numerical simulations.

Abstract: This article deals with multiaxial fatigue strength of notched round bars made of Cr-Al-Mo steel and tested under combined tension and torsion loading. Fatigue life is one of the important factors in design since majority of engineering components are subjected to variable loading. Most of mechanical components in engineering practice are subjected to combined loading, which can lead to sudden fatigue failure. In present work the fatigue life of specimens made of low-alloy Cr-Al-Mo high-strength steel is studied. Experiments were focused on the high-cycle fatigue region (over 100 000 cycles to final failure). The most relevant goal of this paper is to verify the efficiency of modified classical multiaxial fatigue criteria. The criterion proposed by Goncalves, Araujo and Mamiya was found to be the best in the fatigue life prediction for bending-torsion loading of notched specimens.

Abstract: The paper reports an issue found in using the hollow specimens claimed usually as unnotched. If the goal is to test them under multiaxial loading, the target is to reduce the shear stress gradient by making them thin-walled. Anyhow, the analyses described here show, that this attempt induces an issue unknown previously to authors – the maximum stress in tension loading is found on the inner surface of the tube. The individual effects concerning material and geometry are described.

Abstract: Biaxial tension test of the cruciform specimen of styrene-butadiene rubber is described in this paper. The rubber layer is a part of the conveyor belt used for the transportation of coal. The specimen are loaded by the home made biaxial testing device. The big deformation of specimen are determined by the Digital Image Correlation. The parameters of Mooney-Rivlin hyperelastic material were determined. Numerical simulation of the biaxial test was performed in Comsol Muliphysics.

Abstract: This paper deals with using resonance method for determine the development of the mechanical properties of cement paste with different polyvinyl alcohol content. Main properties which were monitored are the dynamic Young’s modulus and dynamic shear modulus. Those properties were measured during 161 days for better understanding of influence of Polyvinyl Alcohol (PVA) added in the cement paste. Difference between this paper and already published articles is in several parameters. Main difference is that samples in this paper were cured on air, not in water. Moreover was used higher amount of polyvinyl alcohol on modification of cement paste.

Abstract: Different carbon and glass fibre strips were subjected to the double clamp buckle beam test. Furthermore, thin-walled glass fibre box-beams were subjected to the three-point bending test. Results of experiments were compared to different numerical simulations using buckling analysis or static analysis considering large deformations.

Abstract: This paper is focused on the correct description of stress-strain behavior of the R7T steel. An experimental study on the wheel steel specimens including uniaxial as well as multiaxial tests has been conducted. The main attention was paid to such effects as ratcheting and nonproportional hardening of the material. A cyclically stable behavior of the steel under higher amplitude loading was found. The MAKOC model, which is based on AbdelKarim-Ohno kinematic hardening rule and Calloch isotropic hardening rule, has been applied in subsequent finite element simulations. The numerical results show very good prediction of stress-strain behaviour of the wheel steel.

Abstract: Suitable mechanical properties of composites are very important for light low energy constructions. Their specific properties can offer high specific strength, but current composite properties are not at maximum level, and therefore the efforts of development on further improving are focused. Properties of composites depend not only on character of a matrix and reinforcement, but also on properties of an Interphase between these components. Experimental and numerical analysis dealing with the mechanical properties at the micro level for new types of energy-efficient fiber composites with reduced environmental impact has been compiled. For numerical analyses a finite element method (FEM) was used. Analyses were focused on the cohesion and stress at the interface of the system fiber-matrix-core. From the results can be seen that the specific orientation of the reinforcement relative to the direction of applied force significantly affects the resulting elastic modulus. When investigating the delamination of the layers, the influence of the fiber orientation of the reinforcement is evident. Also quality of the interface has a crucial influence.

Abstract: Measurement of hardening under reversed uniaxial loading is because of its simplicity very effective mechanical test to achieve several important features of material behavior. In this paper is described special fixture which serves as a prevention of the sheet buckling during the cyclic tension-compression test. Result of the cyclic tension-compression test can consider several important features of the material behavior, which are necessary to be defined in the numerical simulation process. Experimental part of this paper consists of comparison results of strain path obtained from numerical simulation and real experiment. While in numerical simulation process was used material model describing isotropic hardening, real material behaved differently. Difference between strain paths also causes differences between results of springback values obtained in numerical simulation. New material models which include Bauschinger effect whether workhardening stagnation can diminish differences between results of an experiment and a numerical simulation and thus may also improve accuracy of the numerical simulation.