Some urgent problems of the strength of materials and durability of structures
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SOME URGENT PROBLEMS OF THE STRENGTH OF MATERIALS AND DURABILITY OF STRUCTURES V. V. Panasyuk
UDC 620.22: 539.4.01
We present some important theoretical and experimental results obtained in the field of fracture mechanics of materials and durability of structural elements. The main foundations (concepts) of the fracture mechanics and strength of cracked elastoplastic bodies are formulated and some urgent problems of advanced studies in this field of science of materials and their strength are posed. Some problems of the fatigue fracture and durability of metals operating in working media are also investigated. Keywords: fracture mechanics of materials, durability of structures, elastoplastic bodies with cracks, working media.
For the creation of new machines, buildings, and means of material production, it is necessary to have new materials and the data on their physicomechanical characteristics [strength, plasticity, hardness, resistance to the action of corrosive media, and fatigue under the action of long-term constant or variable (in time) loads, etc.]. From ancient times, significant attention was given by the mankind to the accumulation of data of this sort. These investigations led to the formation of science dealing with the physicomechanical properties of materials and, in particular, with their strength, fracture, and durability under given operating conditions and the development of the methods aimed at the prediction of these properties. In the first half of the 20th century, a significant amount of physicomechanical conjectures (hypotheses, generalizations of the experimental data, and postulates) aimed at the evaluation of the serviceability of materials under loading was accumulated in the engineering practice. The “classical approaches” of fracture mechanics and strength of materials were developed on the basis of these theoretical and experimental results and the methods for the evaluation of strength and fracture of materials created by analyzing these results. These classical approaches were used to develop the corresponding criteria for the evaluation of strength and durability of structural elements and propose special procedures for the determination of the basic physicomechanical characteristics of macrovolumes of structural materials, i.e., of the samples of these materials whose sizes exceed the characteristic sizes of the microstructure of material by two orders of magnitude. These approaches are extensively used in the engineering practice and, in many cases, are sufficient for the evaluation of the serviceability of structural elements under normal (not extreme) conditions of operation. However, under the extreme conditions, in particular, in the presence of sharp stress concentrators or cracks, the classical criteria become insufficient. Thus, it is necessary to generalize the basic concepts of the classical mechanics of materials and develop new, more physically substantiated, computational schemes and models for the solution of these problems. As a result of theoretical and experim
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