A solution to the problem of stability of thin-walled steel cylindrical shells

Introduction. It is necessary to improve methods of analysis of the limit states, occurring when a thin-walled shell is in the elastoplastic domain, to use these cylindrical shells as elements of heavily loaded products of construction and machine building industries. Materials and methods. The problem of stability of a circular thin-walled cylindrical shell, made of steel 45 GOST 1050-2013, that takes the load induced by pure compression and axial torsion, has been studied. Besides, experimental and theoretical components of the problem have been analyzed. Experimental facility SN-EVM was applied to perform an experiment test and analyze its findings in terms of different versions of the theory of plasticity used to solve shell stability problems beyond the elastic limit. The co-authors emphasize the unavailability of any definition of the criterion of stability loss under combined loading based on experimental dependences that were identified earlier. The results of the experiment were compared with the results of the theoretical study. The analysis of the shell stability in the case of complex subcritical loading are based on the A.A. Ilyushin theory of stability, in which plasticity functions are taken according to V.G. Zubchaninov’s approximations. Results. The problem was solved using the software programme, developed by the co-authors. The software solves the bifurcation problem of a cylindrical shell with regard for the complex nature of deformations at the moment of stability loss in the case of exposure to complex subcritical loading, commensurable processes and the trajectory that has the form of circular arcs. It has been shown that the proposed method of analysis and approximations describe the real stress-strain state of shells that feature low flexibility in respect of a complex pattern of deformation and characterize a stable state of the material beyond the elastic limit. Conclusions. The theoretical strength and deformability analysis of a cylindrical shell and its experimental studies demonstrate sufficient convergence which proves their reliability. This conclusion will allow to improve the process of design of structural elements made of materials that have complex mechanical properties.

Stability of articulated-movable supported perforated shells

The article considers sloping shell structures of rectangular design. The shells are made from orthotropic composite materials, articulated-movable supported on the contour, and weakened with holes. Two mathematical models of deformation of such structures have been developed: taking into account the discrete input of holes and with using the constructive anisotropy method. The shell stability calculation has been carried out, using three different geometries of shells which were made of 4 composite materials. Thus, altogether 12 structures have been investigated. It is shown that with an increase in the number of holes, the results obtained by the constructive anisotropy method coincide with the results obtained with the discrete introduction of holes.

Two decades of research on the stability of steel shell structures at the University of Essen (1985–2005): Experiments, evaluations, and impact on design standards

In this article, the author looks back on the shell buckling research activities during his 20 years as Full Professor for Steel Structures at the University of Essen, Germany. The main research projects of that time are described very shortly. They included unstiffened circular cylindrical shells under external pressure or meridional compression or combined loading, made of structural or stainless steel at ambient or high temperatures, optionally with wall openings. Stiffened circular cylindrical shells under external pressure or meridional compression were also dealt with, as well as unstiffened conical shells, either as part of cone/cylinder assemblies or as individual truncated cones. Furthermore, the special case of very thin-walled open cylindrical tank shells was investigated under axisymmetric external pressure or wind-like pressure distribution or transverse shear. All projects combined realistic experiments on steel specimens with comparative or enhancing numerical investigations, and all of them were aimed at contributing directly to the improvement of practical shell stability design rules. Last but not least, it is reported on early efforts to develop guidelines for shell buckling design by global numerical analysis, and the author’s credo argued that physical experiments are still indispensable in practice-oriented structural research, particularly in a complex field like shell stability. The article has been written in honor of John Michael Rotter, Professor Emeritus of the University of Edinburgh, who will celebrate his 70th birthday in October 2018.

Stability of a biodegradable microcarrier surface: physically adsorbed versus chemically linked shells

Microcarriers' shell stability was studied with competitive surfactants or with proteins contained in the MSCs culture medium.

Core–shell stability of nanoparticles plays an important role for overcoming the intestinal mucus and epithelium barrier

The stability of the core–shell structure plays an important role in the nanoparticles ability to overcome both the mucus and epithelium absorption barrier.