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В статье представлен численный подход к вероятностному описанию кинетики поверхностных полуэллиптических трещин в элементах труб и сосудов давления и их разрушения под действием циклически изменяющегося внутреннего давления. Разработанный подход использует метод статистических испытаний (метод Монте-Карло) и дает возможность учитывать вероятностный характер вязкости разрушения конструкционного материала, а также статистический разброс параметров кинетического уравнения роста трещины и начальной конфигурации фронта трещины. Показано, что максимальное значение коэффициента интенсивности напряжений по фронту полуэллиптической трещины может достигаться либо в самой глубокой точке ее фронта, либо в точке, выходящей на поверхность оболочки. При этом в процессе циклического подрастания трещины и корректировки соотношения между длинами полуосей положение точки с максимальным значением коэффициента интенсивности напряжений может изменяться. Кинетика трещины, а также вероятность разрушения и долговечность цилиндрической оболочки существенно зависят от начальной конфигурации трещины. Причем с увеличением начальной длины трещины при фиксированной начальной глубине долговечность существенно снижается. Установлено, что двухпараметрический критерий разрушения дает более консервативные оценки вероятности разрушения рассматриваемого конструкционного элемента по сравнению с однопараметрическим критерием классической механики разрушения. The paper presents a numerical approach to the probabilistic description of the kinetics of surface semielliptical cracks in the components of pipes and pressure vessels and their fracture under the action of cyclically changing internal pressure. The developed approach uses the Monte Carlo method and makes it possible to account for the probabilistic nature of the fracture toughness of a structural material, as well as the statistical spread of the parameters of the kinetic equation of crack growth and the initial configuration of the crack front. It is shown that, depending on the crack configuration, the maximum value of the stress intensity factor along the front of a semi-elliptical crack can be achieved either at the deepest point of its crack front, or at the front point emerging on the shell surface. In this case, in the process of cyclic crack growth and the change of the ratio between the lengths of the semiaxes, the position of the point with the maximum value of the stress intensity factor can change: in particular, it can shift from the deepest point of the crack front to the front point located on the shell surface. The crack kinetics, as well as the failure probability and durability of the considered cylindrical shell, depend significantly on the initial crack configuration. Moreover, with an increase in the initial length of the crack at a fixed initial depth, the value of durability decreases significantly. It has been established that the two-parameter failure criterion gives more conservative estimates of the probability of failure of the considered structural component in comparison with the one-parameter criterion of classical fracture mechanics.

The statistics of fires and accidents at the enterprises of oil and gas complex of Russia is presented. The choice of the method for assessing the state of industrial and fire safety is substantiated. It allows to transform the input information presented in the form of a characteristic description of the assessed event into an output dana that has a weighted numerical value. It is shown that the stable functioning of industrial enterprises depends on the safety margin of industrial and fire safety systems. Their maintenance at a certain level requires the allocation of resources (material, human, temporary, etc.), which are limited and insufficient to meet all the requests from the service managers. It is required to scientifically substantiate the targeted provision of activities that have a high index of risk. The purpose of the article is to obtain the result of the assessment of these measures in the form of a weighted risk indicator. This will allow to normalize each event included in the checklists (control sheets) of the enterprise for both industrial and fire safety. A pairwise comparison of the factors and alternatives using the selected method of hierarchy analysis makes it possible to identify the indicators of local and global priorities for each element under study. The weighting coefficients obtained in the form of local priorities relate to the event being tested. Global priorities are directly related to the services and structural units that ensure the sustainable functioning of the industrial and fire safety systems. Use of the methodology for assessing the state of industrial and fire safety at the objects of oil and gas complex of Russia will allow to transfer the management system of these enterprises to a new qualitative level.