Vibrations of Cylindrical Shell Structures Filled With Layered Viscoelastic Material

A thin-walled shell and a thick-walled mass (cylinder) in contact with it, made of a different material, are structural elements of many machines, apparatus, and structures. The paper considers forced steady-state vibrations of cylindrical shell structures filled with a layered viscoelastic material. The study aims to determine the damping properties of vibrations of a structurally inhomogeneous cylindrical mechanical system under the influence of harmonic loads. The dynamic stress-strain state of a three-layer cylindrical shell filled with a viscoelastic material under the action of internal time-harmonic pressure is investigated. The oscillatory processes of the filler and the bonded shell satisfy the Lamé equations. At the contact between the shell and the filler, the rigid contact conditions are satisfied. Dependences between stresses and strains for a linear viscoelastic material are presented in the form of the Boltzmann-Voltaire integral. The method of separation of variables, the method of the theory of potential functions (special functions), and the Gauss method are used to solve this problem. Based on the analysis of the numerical results, it was found that the dependence of the resonant amplitude of the shell displacements on the viscous properties of the filler is 12-15%. Analysis of the results obtained shows that the study of vibrations of shells containing fillers according to the rod theory will lead to rather large erroneous results (up to 20%)

Vibrations of Cylindrical Shell Structures Filled With Layered Viscoelastic Material

A thin-walled shell and a thick-walled mass (cylinder) in contact with it, made of a different material, are structural elements of many machines, apparatus, and structures. The paper considers forced steady-state vibrations of cylindrical shell structures filled with a layered viscoelastic material. The study aims to determine the damping properties of vibrations of a structurally inhomogeneous cylindrical mechanical system under the influence of harmonic loads. The dynamic stress-strain state of a three-layer cylindrical shell filled with a viscoelastic material under the action of internal time-harmonic pressure is investigated. The oscillatory processes of the filler and the bonded shell satisfy the Lamé equations. At the contact between the shell and the filler, the rigid contact conditions are satisfied. Dependences between stresses and strains for a linear viscoelastic material are presented in the form of the Boltzmann-Voltaire integral. The method of separation of variables, the method of the theory of potential functions (special functions), and the Gauss method are used to solve this problem. Based on the analysis of the numerical results, it was found that the dependence of the resonant amplitude of the shell displacements on the viscous properties of the filler is 12-15%. Analysis of the results obtained shows that the study of vibrations of shells containing fillers according to the rod theory will lead to rather large erroneous results (up to 20%)

Źródła naturalne w prewencyjnej konserwacji tekstyliów naturalnie starzejących się

Natural antimicrobials can eliminate fungi and prevent the aging of cotton fabrics. While fungi can cause severe infections to the fabric user etc, natural antimicrobials have the advantage of not being toxic to humans. The present study showed that the essential oils of lemon (Citrus limon), lavender (Lavandula angustifolia) and mint (Mentha piperita) have inhibitory effects on yeast and mould spores on a piece of textile from Romanian cultural heritage, "ie", stored in a space within an ethnographic museum., inhibitory action against Botrytis sp., the inhibitory effect of lemon essential oil on Cladosporium sp. and that of peppermint essential oil on yeast species Rhododtorula mucilaginosa were demonstrated, respectively. Being environmentally friendly, these sources, can be tested on a large scale.Naturalne środki przeciwdrobnoustrojowe mogą eliminować grzyby i zapobiegać starzeniu się tkanin bawełnianych. Chociaż grzyby mogą powodować poważne infekcje u użytkowników wyrobów, naturalne środki przeciwdrobnoustrojowe mają tę zaletę, że nie są toksyczne dla ludzi. Przeprowadzone badanie wykazało, że olejki eteryczne z cytryny (Citrus limon), lawendy (Lavandula angustifolia) i mięty (Mentha piperita) działają hamująco na zarodniki drożdży i pleśni na tkaninie z rumuńskiego dziedzictwa kulturowego, przechowywanej w przestrzeni muzeum etnograficznego. Przyjazne dla środowiska źródła mogą być rekomendowane do stosowania na dużą skalę