Applied Mechanics and Materials Vol. 827

Abstract: The development of effective localized corrosion damage prediction methods is essential for the successful avoidance of unscheduled downtime in steam turbines. It is reported that damage in steam turbines initiates in highly localized areas, most commonly at corrosion pits that act as stress raisers. Therefore, the evaluation of pits distribution and depth is necessary.

Abstract: Photoelasticity is a whole field experimental technique for the measurement and visualizing of the stress and strains in the loaded members. This work is intended to create a unique procedure that allows the use of a computer aided technique in the evaluation of the measurement results. The specimens of the thin annular disk, the thin disk and the shaped beam were tested. The PATRAN program is used for the finite element solution of stress analysis in the investigated specimens. The excellent agreement is established between the results of experimental technique based on the created computer procedure and the results of numerical computations.

Abstract: The paper deals with a problem of stress crack initialization on surface of low pressure steam turbine blade during operational regime. The mention stress analysis together with described environment indicate procedure of experimental works. The other goals of research should lead to a concept of assessment methodology of resistance of moving blades against corrosion and technology increasing fatigue strength of blade steels using surface strengthening. A prototype of the moving blade of the low pressure stages of steam turbine with the increased corrosion resistance should be an output of developed efforts.

Abstract: The typical defect based on the experimental study of the ceramic surfaces was defined. Finite element numerical model was used to compute stresses which develop in the ceramic surface layer with single typical defect under the action of thermal loading. The relationship between heat flow and stresses in the defective surface layer of oxide ceramics is identified.

Abstract: This article describes load capacity of dynamically loaded gears, more precisely describes the mechanical pulsation tests of carburized gears with different thickness of case-hardened depth and case-hardening technology, i.e. addition or removal of certain steps during the case-hardening process of the tooth flank and foot root. The comparison was made on six different process chemical-heat treatment, in two thicknesses of case-hardened depth and two pressure angles. Results are shown and compared in a Wöhler’s curve.

Abstract: Low-pressure steam turbine parts are generally exposed to lowest steam parameters only and it could seem that they should not be susceptible to permanent deformation. However, this assumption is incorrect and permanent changes in geometry become visible in low-pressure turbine casings when they are disassembled after the first time in operation. The driving mechanism of the plastic deformation of the low-pressure casings is mainly the non-uniform temperature field. This paper deals with results obtained from a numerical FEM simulation of a steam turbine low pressure part, which includes elastic-plastic behavior of the material, and results measured under the real conditions.

Abstract: The article is focused on the design and development of the system simulating nonlinear attachment of the engine on the aeroelastic demonstrator. The aim is at obtaining the nonlinear (i.e., amplitude dependent) modal characteristics of the engine pitch vibration mode. Three mechanical concepts were tested to simulate the incremental stiffness characteristic of the engine pitch attachment. The nonlinear demonstrator is utilized for research and development of the advanced methods for the identification of nonlinear modal parameters.

Abstract: In this contribution a theoretical basis of pendulum oscillations is described. The authors deal also with an experimental investigation of nonlinearity in oscillations of large displacement pendulum. High-speed correlation system was used for the registration of pendulum free motion. The obtained data were consequently processed in Matlab and depicted in a form of graphical visualizations and tables.

Abstract: The contribution is focused on research results of thin elements with UHPC matrix reinforced by textile glass reinforcement. A set of three test samples with size of 1100 x 120 x 20 mm were produced in laboratories of the Klokner Institute. Using accompanying tests the material characteristics of the concrete matrix and the textile glass reinforcement were determined. This reinforcement is modified by a protective epoxy surface layer, co called coating. The reason of the coating is to prevent a formation and a development of corrosive processes on the reinforcement texture. The samples were tested at four-point bend test in a thermal chamber. The thermal chamber is a space where it is possible to gradually regulate the temperature up to 75 °C under a constant value of a loading. In the course of the temperature increasing is using a measuring unit measured mainly bend in the middle of the span in time and the course of an inner and outer temperature. The impact of the increased temperature on the cohesiveness of the non-conventional reinforcement and the UHPC matrix is evaluated from the monitored data.

Abstract: Research in the Ultra-High Performance Concrete applications field is very important. Current experiences shows that the structure design should be optimize due to relatively new fine-grained cement-based Hi-Tech material with excellent mechanical and durability properties. It is not sure if some of the volumetric changes like creep or shrinkage has or has not an impact on an advantage for the construction and for the structure design. The effect of the shrinkage and creep of common used concretes are well known and well described at publications but the effect of volumetric changes of the UHPC is mostly unknown because of the fact that some of experimental tests are long term and the development of UHPC is still in its basics. A lot of works are focused on a basic mechanical properties and durability tests.