Abstract
The criteria of evaluation of technical condition of structures with crack-like defects on the basis of the concept of «resistance of structural element to crack propagation» were proposed. This indicator is a characteristic of the rate of change in stress intensity factor at the top of the crack in the structure element in the course of its development. For six model cases of crack-like defects, taking into account the theoretical principles of mechanics of destruction of materials and structures, we established analytical dependences of SIF K I and derivative dK I /da with respect to dimensionless parameter a/t, where a and t are characteristic dimensions of a crack and a slab. We substantiated the characteristic values of ratios (a/t)*, as well as the depth of potential crack-like defects, in case of exceeding of which there is an abrupt increase in the rate of change in stress intensity factor K I . Values (a/t)* will be used for assessing the strength and reliability of elements of constructions with crack-like defects. At the same time, using the created experimental database and analytical relationship in the form of the Paris power law, the criterial values of SIF in the studied elements of structures for different systems «material-environment» were defined. These values are put into the basis of calculating critical lengths of crack-like defects in profile elements of the structure by the model scheme, considered above. The examples of assessing technical condition of damaged elements of a structure according to the cracks depth with regard to operational factors (load nature, influence of working media, condition of material etc.) were considered. Engineering recommendations for the prediction of crack-like defects were formulated. As an analysis of the outcomes of conducted studies demonstrated, monitoring of defect detection of profile elements of the boom of stack discharge conveyor is necessary to carry out, guided by the calculations of resistance of material to crack propagation. Each system «material – environment» requires an individual approach to diagnosis and monitoring of technical condition. The research outcomes might be used for engineering evaluations of the results of monitoring of profile elements of the boom of stack discharge conveyor.
Highlights
Nowadays, the problem of providing for reliability and security of functioning of engineering long-operating structures is absolutely relevant in many countries of Europe and throughout the world [1]
Residual strength and residual durability of engineering structures are significantly influenced by corrosion and corrosive-mechanical defects that occur on the surfaces of their elements
Based on the results of experimental research, we defined the criterial values of SIF for steel of art. 3, of which the straightedge of the boom of the stack discharge conveyor 45 × 45 × 5 mm was manufactured
Summary
The problem of providing for reliability and security of functioning of engineering long-operating structures is absolutely relevant in many countries of Europe and throughout the world [1] This is explained by the fact that the planned resource of many technological complexes and engineering constructions is gradually being exhausted and more and more damage of diverse nature is revealed in their elements [2]. The results of technical diagnosis of technological equipment [1, 2] indicate that in structural elements the number of so-called non-traditional damages, which are impossible to predict using regulations and documents, is increasing They appear as a result of long operation of equipment or various deviations of parameters of operational modes from their calculated values. Such damage is mostly of corrosive-mechanical nature and is formed primarily in the areas of high concentration of stresses caused by special features of design or by the technology of manufacturing the parts [4]
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