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The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. PrefaceThis monograph is devoted to one of the most popular methods for the determination of the plastic material properties, i.e. the tensile test particularly from the moment of neck appearance in the sample.Despite the fact that a few different classical formulae exist which describe the stress distribution in the neck, there is not any certainty which of them is more accurate and the choice to apply a certain formula is often somewhat arbitrary. After thorough literature search, it turned out that the formula of Bridgman is more often utilised in practice for the yield stress determination. However, our preliminary analysis has shown that it may generate rather non-negligible error (up to ten percent) at least in the case of ideal plastic materials.It is well known that in the western literature Bridgman's formula is more frequently used while the eastern literature prefers the approximation by Davidenkov-Spiridonova. Both of these formulae were derived in the forties of the last century. What is interesting is that for the first time a formula for the determination of the average normalised axial stress in the minimal section plane was derived by Siebel, which indeed overlaps with the approach proposed by Davidenkov-Spiridonova. Siebel's work is however less often used and its relative obscurity can probably be historically explained by the fact that it was published in Germany shortly after the Second World War. Obviously, repeated trials were made to derive more accurate formulae and at least two of them were successful (Szczepiński's, Malinin's) but the obtained solutions are still seldom utilised in practice also because of a lack of information on their accuracy in comparison with the classical formulae.The authors' aim in the presented monograph is to collect all known results in the area and to answer the aforementioned questions. Indeed, one can find in the detailed description of materials flow curves determination, criteria of neck creation, derivations of all known formulae for stress distribution in the neck of axisymmetric samples as well as estimation of accuracy of simplifying assumptions applied during the derivation of the classical formulae by means of very accurate numerical simulations. As a result of the critical analysis of the simplifications, a new empirical formula was derived which depends on the same v geometrical parameter (i.e. ratio of the sample radius in the minimal section to the contour radius of the deformed sample) as the classical formulae, but revealing higher accuracy than them. In addition, a new analytical model was proposed, which describes the stress distribution in the neck of an axisymmetric tensile specimen and on its basis a new formula for the average normalised axial stress in the minimum section...

The purpose of this study is to suggest a new formulation for active vibration control of a rectangular plate based on the optimal positions/orientations of piezoelectric actuators/sensors attached to the plate. The free vibration and modal properties are derived by using Rayleigh-Ritz and the transient response by assumed modes methods based on the classical plate theory. Three criteria are proposed for optimal location of piezoelectric patches attached to the simply supported plate. In other words, the optimal positions/orientations of piezoelectric patches can be determined based on spatial controllability/observability gramians of the structure, as well as the consideration of residual modes to reduce the spillover effect. These criteria are used to achieve the optimal fitness function defined for a genetic algorithm optimizer to find the optimal locations/orientations of piezoelectric sensors/actuators. To control the vibrations of the plate, a negative velocity feedback control algorithm is designed. The results of simulations indicate that by locating piezoelectric patches in the optimal positions, the depreciation rate of the structure increases and the amplitudes of the plate vibrations reduce effectively. The effect of number of piezoelectric devices on the active damping property of the system is also analyzed.

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In this paper, three BaTiO 3 powders of various particle size distributions were obtained as a result of mechanical activation in the mixer mill. Green barium titanate pellets and cylindrical specimens were fabricated by both uniaxial and isostatic pressing methods. As a result of the application of different maximal sintering temperatures, the obtained materials were characterized by various average grain sizes: 0.8 µm, 20 µm and 31.0 µm. The basic properties of sintered pellets and cylinders were determined and the influence of materials average grain size on their Young's modulus and compressive strength were determined through compression tests in a uniaxial testing machine, Zwick/Roell Z100. The elastic properties were similar for tested materials with a different grain size. However, the microstructure of BaTiO 3 strongly influenced the compressive strength.