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One of the main challenges for spaceflight safety is preventing crack growth. These defects can occur both in the skin of spacecraft and during the combustion of solid fuels. An important problem is the propagation of cracks at high temperatures. This paper proposes a study of a single polygonal crack under a constant load perpendicular to the crack plane. The solution is constructed numerically using the boundary element method. The main goal of the work is to calculate the stress intensity factors in the vicinity of the crack. The first intensity coefficient was calculated, and calculations were carried out for various crack parameters. • A symmetrical and asymmetrical polygonal cracks were studied. • An asymmetrical crack is more resistant to growth than a symmetrical one. • For a symmetrical crack the stress intensity factor increases in proportion to the size of the crack. • For an asymmetric crack, the stress intensity factor does not change on increasing one shoulder. [ABSTRACT FROM AUTHOR]

Various celestial bodies contain cracks. Also, cracks can be in the skin of aircraft, while their growth is one of the main mechanisms for the breakup of structures. This paper presents a study of one and two rectangular cracks. The influence coefficient (the ratio of the stress intensity factors for the fracture system to the corresponding value for a single crack of the same size) was chosen as the quantity under investigation. The final shape of the crack in the case of its growth is also studied. The following methods were used to model this process: the three-dimensional boundary elements method of discontinuous displacements, in which stress and displacement field is a finite series of expansions of analytically found functions, as well as the two-dimensional boundary elements method of discontinuous displacements, which takes into account the twisting of a growing crack along the stress field at the tip. • Single rectangular crack and system of two parallel cracks were investigated. • For rectangular crack growth is likely to happen from the centers of the sides. • The danger of two parallel cracks depends significantly on their relative position. • Pair of uniaxial cracks is less dangerous then a single crack of the same size. • Non-overlapping cracks in close planes are the most dangerous. [ABSTRACT FROM AUTHOR]

All celestial bodies have defects in the form of cracks. Some of the bodies are large. Colliding with such objects can be dangerous. Therefore, the problem of grinding such bodies remains very urgent. In order to avoid large financial costs, you need to know where to strike in order to achieve the greatest effect. This paper studies the behavior of internal defects under various loads. A three-dimensional elastic medium weakened by a system of plane parallel cracks was examined in this study. A method of boundary elements called the method of discontinuous displacements, was chosen as the numerical method. The advantage of this method is that only the crack boundary is divided into elements, which allows the use of a small (compared to other numerical methods) amount of computer memory. The code was implemented in C ++. The interaction of two circular cracks was investigated depending on the size of the cracks and their relative locations. Calculating the singular integral is required when solving problems involving one crack. In case of several cracks, such integrals are not analytically incalculable. In this study, we present a method that does not require the calculation of singular integrals. • The suggested method makes it possible developing stresses in fractures interactions. • Numerically developed stress intensity factors are in good agreement with analytical solutions. • Two plane fractures interaction in space being located in non-parallel planes was investigated. • Formation of wrinkles on the surface of curved fractures brings to an essential decrease of stresses. [ABSTRACT FROM AUTHOR]

Strength of Space vehicles is a crucial issue for Space flight safety. The presence of latent defects in the material has a significant effect on the strength at different loads: the speed and direction of crack growth. In this paper, we study a three-dimensional elastic medium weakened by a system of plane cracks and one crack with a bend. As a numerical method, the method of boundary elements was chosen, namely, the method of discontinuous displacements. The code is implemented in C ++. A comparison was made with known analytical results. Bend crack behavior is studied for various loads. • Cracks with a bend always begin to grow along the bend line. • Numerically developed stress intensity factors are in good agreement with analytical solutions. • Two plane fractures interaction in space being located at an angle was investigated. • Stress intensity factor depends on the nature of the applied load. [ABSTRACT FROM AUTHOR]

All structural materials contain certain microdefects. Various elements of aircraft and spacecraft made from these materials are subjected to high mechanical loads and thermal effects during operation, which, in turn, can lead to the evolution of defects and total fracture of individual parts of the mechanism. Therefore, a quantitative and qualitative estimation of the stress and temperature fields in different bodies with complex configuration of external loading and temperature disturbances is needed. This paper presents a technique for numerical modeling of the temperature field in a medium weakened by a large system of partially heat penetrable cracks, including the possibility of considering it as an infinite periodic system. The method is based on a numerical algorithm, which uses the expansion of the solution into a finite series. Every term of this series is a certain analytical solution of the heat conduction theory obtained by the authors. To verify the method, the numerical results were compared with the well-known analytical solutions both for a configuration with finite number of cracks and for the periodic system. Also the heat flux intensity factors for a doubly periodic system were determined. • The numerical modeling of the temperature field in a medium weakened by partially heat penetrable cracks is presented. • The possibility of considering an infinite periodic system of cracks is included. • The numerical results were compared with the well-known analytical solutions and showed good agreement. • The heat flux intensity factors for a doubly periodic system were determined. [ABSTRACT FROM AUTHOR]

One of the main problems of fracture mechanics is to describe the behavior of media with cracks. At the same time, more and more attention is paid to the study of large systems, including periodic structures. For several cracks, the coefficient of influence is considered to be an important parameter. It is the ratio of the stress intensity factor calculated in the problem of a system of cracks to the stress intensity factor for a single crack under the same load. The paper proposes a method that allows to accurately determine the coefficients of influence for large systems of cracks, including the case of periodic structures, in which the number of cracks is infinite. The method is based on a numerical algorithm developed by the authors that uses the method of discontinuous displacements of a high order of accuracy and an asymptotic representation of stress fields at the crack tip (M. Williams). To verify the method, the results of the implemented algorithm are compared with known analytical solutions both for single cracks and for an infinite doubly periodic system of cracks. • The suggested method makes it possible developing stresses in fractures interactions. • The method allows calculating infinite systems of cracks. • Numerically developed stress intensity factors are in good agreement with analytical solutions. • The interaction of periodic systems of cracks in space located in non-parallel planes was investigated. [ABSTRACT FROM AUTHOR]