Applied Mechanics and Materials Vol. 732

Abstract: Vibration reduction in term of lower acoustic noise level increases e.g. the passenger comfort, fulfills acoustic manufacturing standards, decreases the transportation influence on the environment etc. The basic sheet metal structure is complemented with damping layer which absorbs the vibration energy. The frequency response experiment analysis of the component structure with damping material helps to validate the separate material models used for predictive simulations.

Abstract: This paper presents the results of measurement of the stress and the theoretical analysis of the steel structure of the Kaplan turbo generator in the Kamýk power station in the Czech Republic. Based on the number of load cycles and the finding of the maximum stress range of critical details of the most loaded part, the lower star, the residual lifetime of the turbo generator was determined.

Abstract: This paper presents the results of visual inspection and the theoretical analysis of steel structure of the upper star of the Kaplan turbo generator in the Lipno power station in the Czech Republic. Based on the number of load cycles and the finding of the maximum stress range of critical details of the most loaded part, the upper star, the residual life-time of the turbo generator was determined.

Abstract: This article describes experimental research on properties of adhesive joints with embedded optical fibers. The objective was to determine whether fibers may cause a reduction of mechanical properties of joints. Specimens with single-lap joint for tensile test were made with various configurations of optical fibers in an adhesive layer. Shear strength and fatigue life tests were performed and results were evaluated using the statistical analysis methods.

Abstract: The Simulation Based Reliability Assessment SBRA Method is a probabilistic method using the Monte Carlo simulation [1,3]. Substance of that method consists in repeated calculations of relatively simple equations, where entering variables (dimensions of the body, mechanical properties, loads, etc.) can be constant or defined by histograms, respectively. Probability of failures of the model and the steel beam were determined using Anthill software [3].

Abstract: General principles on probabilistic approach to structural verification with respect to durability are provided in the international standard ISO 13823 which is currently being implemented into the system of Czech standards. The operational use of the new procedures in practice would require specification of probabilistic durability criteria, physical models of material deteriorations, and theoretical models of basic variables. It appears that the probabilistic methods of optimisation may provide valuable background information facilitating determination of appropriate criteria for durability.

Abstract: The paper presents results of long-time investigation of mechanical properties of composite gypsum material using nondestructive technique. The gypsum block was put to the façade of the building for four years. Then it was removed and cut to smaller specimens, which were investigated. The matrix of 6 × 4 specimens of dimensions 40 × 40 × 160 mm were cut from the block after its removal from the façade. After 6 and 9 years, the Young’s moduli and shear moduli of these specimens were determined from the transversal, longitudinal and torsional vibrations using the impulse excitation method.

Abstract: Significant progress has been made in the last years towards understanding the short and long – term performances of fibre reinforced cementitious materials and this has resulted in a number of novel and innovative uses. One of the main problems concerns the great quantity of random parameters– the placement of fibres, their orientation and quantity in a determined section etc. In consequence, full – probabilistic methods could be recommended for the analysis and evaluation of FRC. It can be assumed that for some structures probabilistic parameters derived from actual material tests could be used. A series of 9 specimens with the same reinforcement was used for a standard 4-point bending test. Using the obtained results, probabilistic normal distributions for the necessary input data were defined. The diagram of the experiment can then be recalculated probabilistically using the method SBRA. The ductility of the material can be expressed energetically. The final result is a histogram of the flexural toughness of the specimen that can be used for further calculations and evaluations.

Abstract: Non-destructive acoustic analysis methods, Impact-echo method as a traditional and the Acoustic Emission method as nontraditional method for civil engineering, were used for experiment. This paper reports the experiment during hardening and drying of specimens of alkali activated slag mortars. Alkali activated slag is a material having a great potential to be used in practice. The main drawback of this material is a high level of autogenous and especially drying shrinkage, which causes a deterioration of the mechanical properties. The aim of this paper is introduce the effect of method used and time curing on the microstructure of alkali activated slag mortars. An understanding of microstructure–performance relationships is the key to true understanding of material behaviours.

Abstract: There are a lot of structures in building and civil engineering where the significant structural elements are loaded by large tensile forces (e.g. tension bars of building structures). In many practical cases it is important to know the actual value of tensile forces in tensile structural elements for assessment of their reliability. The four experimental techniques are used for determination of tensile forces in practice most often. The vibration frequency method, which is one of them, is very suitable for experiments done only one time or sometimes, especially in cases when the examined structural elements are already activated and the application of an experimental method is necessary in this situation. The experiment described in this paper was focused on the tensile force determination in steel rods, which were very short and relatively stiff. The evaluated tensile forces of the investigated short steel rods were affected by a significant error when only the simplest models (the string model, the simply supported beam and the fixed beam) and measured natural frequencies were applied. In order to precise the determined tensile forces, the theoretical beam model supported by simple supports with torsion springs (“the elastically fixed beam”) and the measured natural modes of the rods had to be necessarily taken into account.