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From Dániel Vetö's website:
http://doktori.bme.hu/bme_palyazat/hallgato/veto_daniel/veto_daniel_en/index.html
Dániel Vetö
Csonka Pál Doctoral School
Department of Mechanics, Materials and Structures
Dániel Vetö writes about his research on
"Application of Geometric Method for the Research of Buckling of Spherical Shells
Introducing the research area
"The research focuses on the buckling of the total spherical shell loaded with concentrated force or distributed load. There are many questions about the shell buckling which have not been answered as yet. One can observe that the theoretical and experimental results about the buckling load differ. Also, there can be many different kinds of buckling shape in some cases for one given shell. It could be experienced in several cases that the sphere remains in the buckled state even after the load is removed. We try to find the explanations for these phenomena and answer these questions."
Brief introduction of the research place:
"The Department of Mechanics, Materials and Structures is engaged in a big variety of problems in the field of structural design. The research topics are related to steel, timber, reinforced concrete, masonry and composite structures. Morphological and topological problems, stability of shell structures are also a part of their research activity, both from theoretical, and from practical point of view and there have been 17 successful PhD defenses."
History and context of the research:
"Relatively thin surface structures that have curved middle surface are called shells. One can find them at many places in engineering practice, e.g. domes (Fig. 1.), silos, containers, pressure vessels, different vehicles, micro switches. Similar constitutions can be found in nature as well, e.g. stem cells, unicellular organisms, bacteria, organs (heart, circulatory system). It is also important to keep in mind that engineering structures can lose their stability, which means a change in the load-bearing capacity of the structure due to the change of the geometry describing it. The loss of stability of shells is called buckling. Finding the buckling load of shells is not a simple task and has not been completely worked out as yet. The difference between theoretical and experimental results cannot be merely attributed to shape imperfections in experiments, but also due to the insufficiencies in theoretical models."
"In the 1950s, A. V. Pogorelov worked out the so-called geometric shell buckling theory. Although known to scientists since its publication, its applicability was severely constrained by the fact that the assumption of the buckled shape has only been based on experiments. During the last 10 years scientists – mainly physicians – laid the determination of the buckled shape on mathematical bases, but the load-deflection diagram of the shell was examined only qualitatively. For engineers, quantitative determination of buckling load may also be essential."
Aim of the research:
"The main purpose of the research is to determine the load-deflection diagram of spherical shells using Pogorelov's geometric shell buckling theory. The determination of the load-deflection diagram is important because the notable points on the curve correspond to the buckling load of the shell. The load-deflection diagram that describes the behaviour of real (imperfect) shells (Fig. 5.) has typically one maximum and one minimum, and the corresponding load values are called upper and lower critical loads. The maximum on the load-deflection diagram of the theoretical (perfect) shell is called linear critical load, but only a fraction of this value is reached in real shells."
(For more see the website cited above.)
Publications:
[1] Vetö, D. and Sajtos, I.: Application of Geometric Method to Determine the Buckling Load of Spherical Shells. Pollack Perodica, 4 (2), pp. 123 _134. (2009)
[2] Vetö, D. and Sajtos, I.: Application of Geometric Method to Determine the Buckling Load of Spherical Shells. ed.: Lehoczky, L.: XXIII. microCAD International Scientific Conference, University of Miskolc, 19 _20. March, 2009, Miskolc, Hungary, Innovation and Technology Transfer Centre, Miskolc, pp. 61 _66. (2009)
[3] Vetö, D. and Sajtos, I.: Application of Geometric Method to Determine the Buckling Load of Spherical Shells. ed.: Iványi, M.: Pollack PhD, Fourth International PhD, DLA Symposium, University of PÈcs, Pollack Mih·ly Faculty of Engineering, 20 _21. October, 2008, Pécs, Hungary, Rotari Press, Komló, p. 61. (2008)
[4] Vetö, D. and Sajtos, I.: Investigation of Buckling of Spherical Shells. FUDoM 09, Finno-Ugric International Conference of Mechanics, 23 _29. August, 2009, Ráckeve, Hungary, pp. 31 _32. (2009)
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