The stability of the outer nonmetallic layer of a triple-layer rod with foam core was studied both experimantnlly and theoretically by the energy balance method. The buckling of the outer layer occurs by a sudden transition to a nonadjacent equilibrium form and this process should be seen in regard to a set of deformational factors.The predominant methods in current engineering calculations for the local stability of the compressed outer layer of triple-layer rods and plates involve evaluation of wave formation related to initial curvature. The problem usually reduces to a calculation of the second-order stability of a bent, compressed elastic rod or plate. As a rule, especially in the outer layers of structure consisting of thin metal sheets, this procedure gives a suitable result. However, a region of mechanical and geometrical parameters for the elements of triple-layer structures exists, in which there is a significant lack of agreement of the testing and calculation results. This study is devoted to a study of this question.The experimental part of this study involved testing two groups of triple-layer rods for off-center compression. The sables of the first group had an outer layer made of water-resistant veneer and a polystyrene foam middle layer of density 0.04 g/cm 3.Cement chip plates were used for the outer layers of the samples of the second group, while the core layer consisted of polyurethane with density 0.055 g/cm 3. The materials, span, and thickness of the layers were taken to correspond to actual structural elements. The rod dimensions, attachment conditions, and arrangement of the instruments are shown in Fig. la.The following results are most hnportant for solving the problem posed. The deformation of the outer layer from wave formation and the displacement of the contour of the middle layer from its transverse deformations perpendicular to the rod axis become noticeable even in the ~ los.ding stages. Judging from the nature of the wave formation, its initiator may be considered the initial curvature. The wave formation is regular in nature along the length of the rod and proceeds sinnsoidally with the length of the half-wave corresponding to the form of buckling of the rod on an elastic base in the case of minimal crific~ force (Fig. lb).At a given load, the total flexural deformations of the outer layer due to wave formation and displacement of the contour of the middle layer in separate segments along the length of the rod may reach values such that the sign of its curvature changes. This level approximately corresponds to the critical force in the outer layer. On the other hand, the experimental critical force values differ by a factor of 1.4-2 from the values calculated using the common formulas takirlg account of only wave formation [I].We should note that the form of protrusion of the outer layer changes upon buckling. As a rule, buckling occurs in the samples tested over two half-waves. The periodicity of the initial protrusion of the rod on an elastic base and the change in ks final ...
In the textbook "Engineering design. Metal structures and constructions from wood and plastics" outlines General information about engineering structures of buildings and constructions of steel, wood and plastics, examined physical and mechanical properties of these structural materials. The main principles of analysis of steel structures, wood and plastics in accordance with applicable building codes. The fundamentals of designing and calculation of designs of buildings and constructions of water supply and environmental purposes, considers special requirements of hydraulic engineering constructions, exposed to prolonged exposure to the aquatic environment. Provides references, examples of calculations and test questions. The textbook "Engineering design. Metal structures and constructions from wood and plastics" is the first part of the fourth revised and augmented edition for higher education institutions, and written in accordance with modern design standards the designs of the basic building materials. The textbook "Engineering design. Metal structures and constructions from wood and plastics" is intended for students of higher educational institutions studying in areas of training 08.03.01 "Construction" 20.03.02 "Environmental engineering and water management". The material presented in the textbook used for the formation of knowledge, skills and professional competences necessary for professional activities in the field of the theory and practice of analysis and design of engineering structures of buildings and structures for various purposes, used in construction. Methodological feature of the present edition is a concise form of presentation, which greatly facilitates its absorption with the requirements of the engineering disciplines, study programs for bachelors. The textbook "Engineering design. Metal structures and constructions from wood and plastics" meets the requirements of Federal state educational standard of higher education of the last generation. The textbook "Engineering design. Metal structures and constructions from wood and plastics" consists of the first (introductory) Chapter provides General information about engineering structures and two sections. The first section is devoted to metal structures, the second section is about the structures of wood and plastic. On the fourth edition of the textbook work: Chapter 1 — Professor Yu. M. Dukarsky; section I and applications — Professor Yu. M. Dukarsky and associate Professor O. V. Mareeva; section II — Professor F. V. Russ.
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