The article deals with the problems of calculation of elastically deformable systems with unilateral constraints and Coulomb friction. For the numerical solution of the problem, the finite element method is used, the contact interaction is modeled by means of the contact finite elements (CFE) of the frame-rod type. The basic relations and statements of static and dynamic contact problems for the interacting elastic bodies are given. To comply with the limitations under the conditions of ultimate friction-sliding, the method of compensating loads is applied. On the basis of the proposed discrete contact model and step-by-step loading schemes, the numerical algorithms are developed, which allows calculating structures with unilateral constraints and Coulomb friction, both under static and dynamic loads, as well as taking into account the different contact conditions that approximate the calculation scheme to the real operating conditions of a structure or construction. With the help of the proposed approach, numerical solutions of the problem of contact of the structure with the base under dynamic load are obtained and analyzed.

The work is devoted to modeling the process of formation, development and propagation of cracks. Currently, there is a large number of physical and mechanical-mathematical models describing the process of destruction of various materials. In addition to the fracture criteria, it is also important to correctly take into account changes in the rheology of the fractured material, including the contact interaction between the surfaces of cracks and fragments. This paper proposes a numerical approach to solving the problems of contact interaction and brittle fracture of elastically deformable bodies. Crack bank interactions, including frictional forces and contact pressures, is modeled by the means of frame-type contact finite elements (CFE) using a stepwise analysis method. Various contact conditions – separation, clutch, friction-sliding, as well as rheological properties of crack surfaces and fragments – contact layer pliability, adhesion strength, etc. are modeled with the help of CFE. The proposed approach was used in the numerical modeling of bone damage under the penetrating action of a rigid indenter. The conducted numerical studies have shown a good correspondence of the calculated and experimental results, despite the substantial approximation of the used calculation schemes.

The article deals with the dynamic problem of deformable solid mechanics with unilateral constraints and Coulomb friction. For the numerical solution of the problem, the finite element method is used, the contact interaction is modeled by means of the contact finite elements (CFE) of the frame-rod type. The statement of dynamic contact problem for the interacting elastic bodies is given. On the basis of the proposed discrete contact model and the method of step-by-step analysis a numerical algorithm has been developed, which allows in one step-by-step (on time) process to perform the integration of the equations of motion and the implementation of the conditions for unilateral constraints with Coulomb friction on the contact simultaneously. Under the conditions of ultimate friction the method of compensating loads has been applied. With the help of the proposed approach, numerical solutions of the problem of contact of the structure with the base at different parameters of the dynamic load have been obtained and analyzed.

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Problems with unilateral constraints are not uncommon in the practice of calculating  building construction and structures. Certain difficulties in solving them arise during contact friction, as well as the dynamic action of the load. It is known that such problems from a mathematical point of view s are not correct enough, their solution becomes more complicated and depends on the history of loading and deformation of the structure. At the same time, the ability to take into account the complex working conditions of the structure makes its calculation more complete and accurate. The paper considers the solution of  a dynamic contact problem on the basis of the finite element method and the step-by-step loading method. Unilateral constraints with Coulomb friction are modeled using contact finite elements of a frame-rod type. The method of compensating loads is applied in order to comply with the limitations under ultimate friction-sliding conditions. Based on the considered discrete contact model and the step-by-step analysis method, a numerical algorithm has been developed, which allows in one step-by-step process to integrate simultaneously the equations of motion and implement contact conditions with Coulomb friction. With the help of the proposed approach, numerical solutions of the problem pertaining to a structure contact with the base have been obtained and analyzed at various parameters of dynamic load. Comparison of the results with the solution obtained by the well-known iteration method on the ultimate friction forces allows to conclude about the efficiency and reliability of the developed algorithm under complex contact conditions and dynamic loading.