Przeglądaj wg Autor "Tomczyk, Barbara"
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Pozycja Lenght-scale effect in stability problems for biperiodically stiffened cylindrical shells(Wydawnictwo Politechniki Łódzkiej, 2012) Tomczyk, BarbaraThin linear-elastic cylindrical shells having a micro-periodic structure along two directions tangent to the shell midsurface (biperiodic shells) are object of considerations. The aim of this paper is to investigate the effect of a periodicity cell size on the stationary stability of such shells. In order to take into account the length-scale effect in special stability problems, a new averaged non-asymptotic model of biperiodic shells, proposed in [Tomczyk B.: Thin cylindrical shells, in: Thermomechanics of Microheterogeneous Solids and Structures. Tolerance Averaging Approach. Ed. by Woźniak C, Michalak B., Jędrysiak J., Lodz Technical University Press, Lodz 2008, pp. 165-175] is applied. In the framework of this model not only the fundamental "classical" critical forces but also the new additional higher-order critical forces depending on the period of heterogeneity will be derived and discussed. These critical forces cannot be obtained from the asymptotic models commonly used for investigations of the shell stability. The differences and similarities between results derived from the aforementioned non-asymptotic biperiodic shell model and a certain asymptotic one as well as from the non-asymptotic model for shells with a micro-periodic structure along one direction tangent to the shell midsurface (uniperiodic shells) will be discussed.Pozycja On stability of thin periodically, densely stiffened cylindrical shells.(Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej, 2005) Tomczyk, BarbaraThe aim of this contribution is to propose a new averaged nonasymptotic model of stationary stability problems for thin linear-elastic cylindrical shells reinforced by stiffeners which are periodically, densely spaced along one direction tangent to the shell midsurface. As a tool of modelling we shall apply the tolerance averaging technique. The resulting equations have constant coefficients in the periodicity direction. Moreover, in contrast with models obtained by the asymptotic homogenization technique, the proposed one makes it possible to describe the effect of the periodicity cell size on the global shell stability (a length-scale effect). It will be shown that this effect plays an important role in the shell stability analysis and cannot be neglected.