Applied Mechanics and Materials Vol. 595

Abstract: The theme of the present work is the analysis of the guided waves propagation along a flat, narrow composite plate (beam). The investigated structure is made of the multi - layered composite material (carbon fabric with epoxy resin). The applied material posses the quasi - isotropic mechanical properties. The guided waves are generated with the use of the piezoelectric activator. The finite element method is used in order to carried out the computer simulations. The plain state of the strain is assumed. The computations are performed for the intact and the damaged structure. In the case of the damaged structure the received signal (voltage) is significantly different in comparison with the intact structure. The qualitatively similar results are obtained from the experimental investigations.

Abstract: In this paper, the main design parameters of 750 kw horizontal-axis wind turbine wheel are computed based on simplified theoretical design model; The airfoil coordinates of the blade derived from Profili are spatial switched in Excel, then the spatial coordinates of every foline are obtained; In SolidWorks, the curves of foline outlines are drawn on the basis of former coordinates. Eventually, the 3D model of the blade is created by loft surfacing according to the foline outlines. The blade model created in this paper could be used in the coming finite element analysis.

Abstract: A comparative study on performances of rod-baffle (RB) and segment-baffle (SB) heat exchangers was carried out by numerical simulations under the same conditions. The results show that the overall heat transfer efficiencies are similar in these two types of heat exchangers with the same heat transfer areas. But RB heat exchangers show more uniform and smooth fluid flow, as well as much lower pressure in the shell side compared to SB counterparts. These detailed characteristics of heat transfer and fluid flow evidence better performances in RB heat exchangers and also provide a deeper insight into design and optimization of shell-and-tube heat exchangers.

Abstract: In this study, various alternative vector-valued ground motion intensity measures (IMs) are used to estimate maximum inter-story drifts and hysteretic energy demands of steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure as first parameter Sa (T₁). As the second parameter of the vector, IMs related to peak, integral and spectral shape parameters are selected. It is concluded that spectral-shape-based vector-valued IMs have the best relation with maximum inter-story drift and energy demands in steel frames subjected to narrow-band earthquake ground motions.

Abstract: The transport of 1M NaCl water solution in three different types of sandstones is studied For basic characterization of studied materials, their chemical composition, porosity, bulk density and matrix density are accessed. The chloride transport is analyzed using two different methods. In the first one, the chloride absorption coefficient is measured on the basis of a modified sorptivity concept. The second method consists in carrying out an inverse analysis of experimentally measured moisture and chloride concentration profiles, leading to the determination of chloride diffusion coefficient as a function of chloride concentration, and moisture diffusivity as a function of moisture content. The chloride transport properties obtained for the particular studied materials are compared and the observed differences are discussed.

Abstract: Temperature and enthalpy of phase changes taking place in PCM (Phase Change Material)-modified plasters within their heating and cooling exposure are studied in the paper. The studied plasters are composed of hydrated lime, pozzolan admixture, silica sand, water, and encapsulated parrafinic wax that is used as PCM. The studied materials are characterized by bulk density, matrix density, and total open porosity. The temperature of phase changes, heat of fusion and crystallization are evaluated by DSC (Difference Scanning Calorimetry) analysis that is performed in inert nitrogen atmosphere. Experimental data reveal a substantial improvement of heat storage capacity of PCM-modified plasters as compared to the reference material without PCM.

Abstract: The rebound hammers of the Schmidt system belong among the non-destructive testing methods that are used for determining compressive strength of building materials, most often concrete and rocks. Calibration relations between the rebound number and compressive strength must be available to determine the compressive strength. Calibration relations are determined on the basis of destructive and non-destructive tests of test specimens. This paper deals with the effects of internal compressive stress in calcium silicate bricks on measurement results obtained using the L-type Schmidt hammer. Based on the obtained information, in order to process calibration relations, it is recommended to apply such force to the test specimens, which corresponds to the internal compressive stress 10-15% of the final compressive strength. We do not recommend measuring on firmly supported bricks only.

Abstract: The seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF), modeled as complex MDOF systems, are estimated and the accuracy of the commonly used rules to combine the individual effects of the seismic components, as well as the influence of the correlation of the components and the correlation of the individual effects on the accuracy of the rules, are studied. The responses are also estimated for several incidence angles of the horizontal components and the critical one is identified. It is observed that the rules underestimate the axial load but they reasonably overestimate the interstory and base shear. The effect of individual components may be highly correlated, not only for normal components, but also for totally uncorrelated components. Moreover, the rules are not always inaccurate in the estimation of the combined response for correlated components. On the other hand, totally uncorrelated components are not always related to an accurate estimation of the combined response. The critical response does not occur for principal components and the corresponding incidence angle of the seismic components varies from one earthquake to another. In the general case, the critical response can be estimated as 1.30 times that of the principal components.

Abstract: The global ductility parameter (μ_G), commonly used to represent the capacity of a structure to dissipate energy, and the associated ductility reduction factor (R_μ), are estimated for steel buildings with perimeter moment resisting frames (PMRF), which are modeled as 2D and 3D complex MDOF systems. Results indicate that the μ_G value of 4, commonly assumed for moment resisting steel frames, cannot be justified. A value of 3 is more reasonable. The values of μ_G and R_μ may be quite different for 2D and 3D structural representations or for local and global response parameters, showing the limitation of the commonly used Equivalent Lateral Force Procedure (ELFP). Thus, the ductility and ductility reduction factors obtained from simplified structural representation must be taken with caution.

Abstract: The monitoring information of the coal mine trackless rubber tyre electric vehicle is analyzed and researched. The hardware and software of real-time data monitoring system electric vehicle is designed based on the TMS320F2812 DSP chip and LCD module MS12864. The coal mine trackless rubber tyre electric vehicle real-time data monitoring is achieved.